Mechanical Properties of PEEK for Posterior Fixed Partial Denture (FDP): an in vitro study
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| Mechanical Properties of PEEK for Posterior Fixed Partial Denture (FDP): an in vitro study | |||
| A thesis submitted for the requirements of the degree of master (Oral and Maxillofacial Prosthodontics, Faculty of Dentistry, King Abdul Aziz University) | |||
| By ( Hasan Asiri ) Written by Dr Fred |
| Supervised byDr. Dalea M Bukhary |
| FACULTY OF DENTISTRY KING ABDULAZIZ UNIVERSITYSAUDI ARABIA 12.8.1444 / 4.3.2023 |
| Mechanical Properties of PEEK for Posterior Fixed Partial Denture (FDP): an in vitro study | |||||
| By Hasan Asiri | |||||
| A thesis submitted for the requirements of the degree of master (Oral and Maxillofacial Prosthodontics, Faculty of Dentistry, King Abdul Aziz University) | |||||
| Supervised by Dr. Dalea M Bukhary | |||||
| FACULTY OF DENTISTRY KING ABDULAZIZ UNIVERSITYSAUDI ARABIA 12.8.1444 / 4.3.2023 FACULTY OF DENTISTRY KING ABDULAZIZ UNIVERSITYSAUDI ARABIA 12.8.1444 / 4.3.2023 | |||||
| Mechanical Properties of PEEK for Posterior Fixed Partial Denture (FDP): an in vitro study | |||||
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| This thesis has been approved and accepted in partial fulfillment of the requirements for the degree of master (Oral and Maxillofacial Prosthodontics, Faculty of Dentistry, King Abdul Aziz University) |
| By (Hasan Asiri) |
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| Copyright All rights reserved to the university. No part of this thesis may be reproduced or transmitted in any form or by any means or may be translated it into any of the languages, without the prior written per- mission of the author or the scientific department at the university. It is necessary to bookmark it when citing. This page must form part of any such copies made. |
Acknowledgment
First and foremost, I would like to express my thanks and gratitude to Almighty Allah (God) for granting me the willingness and strength to establish this work and for His limitless blessings. I wish also to express my deep love, gratitude and prayers to my loving parents and brothers who have supported me and prayed all the time so that I be successful in my studies and hence kept me going through the completion of this work. I would like also to express my gratitude and appreciation to my supervisors Dr. Dalea Bukhary, Dr.Wallaa Babeer, Dr.Rwaida Alshali for giving me the opportunity to carry out this thesis under their expert supervision. I deeply appreciate their encouragement, support, invaluable advice, expertise, and knowledge which have made go forward towards a Master with a great experience. Great thanks with peace to my beloved country, the Kingdom of Saudi Arabia with great vision for 2030.
Thanks to all colleagues and friends in KAU Jeddah and KKU Abha for their support, prayers, and wishes for good luck in my life.
Hasan Asiri
April 2023
Abstract
Mechanical Properties of PEEK for Posterior Fixed Partial Denture (FDP): an in vitro study
الخواص الميكانيكية لمادة الكيتون الأثير متعدد الأثير للتركيبات السنية الخلفية الثابتة: دراسة في المختبر
In the field of Prosthodontics, replacing missing teeth could be performed through the use of either fixed (FDP) or removable (RPD) partial denture treatment modalities. In FDP, a dental restoration is used to replace several missing teeth-most commonly 3 to 4 units-a supported on natural teeth or dental implants. For management of such cases, the fabrication of the FDP requires special attention to the FDP abutments, material used and design. Multiple material used in fabrication of FDP depending on the purpose of its use either provisional (short term or long term) or definitive material. One of which is Poly-Ether-Ether-Ketone (PEEK). It is a member of the PAEK. Poly-Aryl-Ether-Ketones (PAEKs) which are a group of thermoplastic resins with high performance. PEEK has been used in Dentistry and Prosthodontics in specific due to its excellent properties. It has good properties for example, high rigidity with low weight. It is a radiolucent so the detection of caries under the prosthesis will be easy, high wear resistance, high fatigue resistance, modulus of elasticity just between the cortical and cancellous bone. Because of the above-mentioned characteristics, in particular the good milling and grinding properties combined with high stability similar to the stability of human bone the PEEK was chosen. There are several studies that investigated the use of PEEK in FPD as a full contour or framework substructure. A study conducted by Bogna Stawarczyk et al (2013) investigated the possibility of using PEEK as a material for fixed dental prostheses. They found that Peek had high fracture load if used as FDPs substructure, however, needs more investigation. Verónica Rodríguez et al (2021) evaluated the fracture load and pattern of FPD Framework fabricated by different CAD\CAM materials including PEEK. They found that CAD /CAM PEEK showed acceptable fracture load value with highest load to fracture than zirconia. The study suggested that milled PEEK could be alternative to metal and ceramic FPD restorations in the posterior regions.6 Furthermore, Micovic Soldatovic et al (2022) tested the use of PEEK for implant-supported 4-unit cantilever fixed dental prosthesis (FDP) with frameworks made of two different materials including PEEK. They concluded that All implant-supported 4-unit PEEK FDPs showed a higher fracture load than the maximum occlusal forces in the posterior region.7 Despite the excellent performance of PEEK as a FPD material, yet there is limited study regarding testing the mechanical properties of long-span FDP Using PEEK. This thesis aims to determine the mechanical properties of PEEK and PEKTON 4-Unit FDP Framework in vitro study.
Research Objectives:
Primary objective
- To determine the flexural strength of PEEK, PEKTON, and zirconia 4-Unit FDP Framework in comparison with CO-CR using 3D printed CO-CR Die model.
Secondary objectives
a. To determine if is there a mechanical difference between different materials used for fabrication of 4 unit FDP for the posterior region.
b. To determine if is there difference between framework fabrication methods (printed vs milled) in regards to mechanical properties of 4unit FDP framework?
Predictors: Independent Variables
Independent Variables include fabrication of framework (printed vs milled), dental material (PEEK PEKTON and Zirconia VS COCR).
Outcomes: Dependent Variables
Dependent Variable is: fracture strength (static)
Statistical Analysis
- Descriptive analysis in terms of means and standard deviations will be presented regarding the fracture strength of each group.
- Two-way ANOVA for global hypothesis, level of significance p ≤ 0.05. The statistical work will be done using IBM SPSS Statistics software
Ethical considerations
- This study will be a laboratory trial and will not contain any human subjects, personal identifiers, or vulnerable groups.
- No clinical examination or experimentation is going to be performed.
- However, waiver of documentation will be requested from the ethical committee at KAU-FD
Keywords:
(4-UNIT FDPs ,3D Printed ,zirconia ,PEKTON, PEEK , CO-CR ,Flexural strength ,Bending strength ,mechanical properties , Fixed Dental Prosthesis , Die model )
Table of Contents
Mechanical Properties of PEEK for Posterior Fixed Partial Denture (FDP): an in vitro study. 10
Predictors: Independent Variables. 11
Outcomes: Dependent Variables. 11
1.2 What is prosthodontics?. 18
1.3 Divisions of Prosthodontics. 18
1.3.1 Fixed Prosthodontics (FPD) 19
1.3.2 Removable Prosthodontics. 21
1.3.3 Implant Prosthodontics. 22
1.5 Research Questions and Hypotheses. 26
1.6 A brief statement on the methodology used. 28
2.2 Purpose of the literature review.. 33
2.3 Background information on PEEK material 34
2.4 PEEK Polymer Composition. 35
2.4.1 Biocompatibility of PEEK.. 36
2.4.3. Evolution from PEEK.. 37
2.4.5 Biocompatibility of PEEK and PEKKTON in Dental Applications. 38
2.5 Mechanical Properties of PEEK and PEKKTON.. 39
2.6 Importance of studying mechanical properties for 4 unit posterior FDP.. 40
2.7 Advantages and disadvantages of using PEEK in dental applications. 41
2.8 Tensile Strength and Modulus. 43
2.8.1 Wear Characteristics. 43
2.8.2 Biomechanical Performance. 44
2.8.3 Comparison with Traditional Materials. 44
2.8.4 Techniques of Fabricating FPD Frame in General 45
2.9 Advancements in Dental Prosthodontics. 48
2.9.1 Tensile Strength and Modulus. 48
2.9.2 Wear Characteristics. 49
2.9.3 Biomechanical Performance. 49
2.9.4 Comparison with Traditional Materials. 50
2.10 Mechanical Properties of PEKKTON.. 50
2.10.1 Tensile Strength and Modulus. 51
2.10.2 Wear Characteristics. 51
2.10.3 Biomechanical Performance. 51
2.10.4 Comparison with Traditional Materials. 52
2.11 Mechanical Properties of PEEK in 4-Unit Posterior Fixed Dental Prostheses (FDP.. 52
2.11.2 Modulus of Elasticity. 52
2.11.3 Wear Characteristics. 53
2.11.4 Biomechanical Performance: Implications for 4-Unit Posterior FDPs. 53
2.12 Fracture Strength Evaluation: PEEK and PEKKTON vs. 4-Unit Zirconia Framework. 53
2.13 Fracture Strength of PEEK.. 55
2.13.1: 4-Unit Zirconia Framework. 56
2.13.2: Flexural Strength and Modulus of PEEK and PEKKTON.. 56
2.13.3 Flexural Strength: Evaluating the Bending Resistance. 56
2.13.4: Flexural Modulus: Assessing Material Stiffness. 57
2.14: Comparative Analysis: PEEK vs. PEKKTON.. 57
2.14.1 Clinical Implications. 57
2.14.2: PEEK and PEKKTON in Comparison with Zirconia. 57
2.14.4 Flexural Modulus: Stiffness in Comparison. 58
2.15 Comparative Analysis: PEEK, PEKKTON, and Zirconia. 58
2.15.1 Clinical Implications. 59
2.15.2 Definition and measurement methods. 59
2.15.4 Flexural Modulus: Definition and Significance. 60
2.15.5 Measurement Methods: Precision in Flexural Testing. 60
2.16 Wear Resistance in Dental Materials. 62
2.16.1 Wear Resistance of PEEK.. 62
2.16.2 Wear Resistance of PEKKTON.. 62
2.16.3 Wear Resistance of Zirconia. 62
2.16.4 Factors Influencing Wear Resistance. 63
2.16.5 Clinical Implications. 63
2.16.6 Measurement Methods for Wear Resistance. 63
2.17.1 Fracture Toughness of PEEK.. 65
2.17.2 Fracture Toughness of PEKKTON.. 65
2.17.3 Fracture Toughness of Zirconia. 66
2.17.4 Clinical Significance and Material Selection. 66
2.17.5 Definition and Measurement Methods of Fracture Toughness. 66
2.17.6 Measurement Methods. 67
2.17.7 Significance in Dental Materials Research. 67
2.18.1. Polyether Ether Ketone (PEEK) 68
2.18.2. Poly-Ether-Ketone-Ketone (PEKKTON) 68
2.19 Factors Affecting Mechanical Properties of PEEK.. 69
2.20 Processing techniques. 71
2.20.2. Additive Manufacturing: 71
2.21 Reinforcement materials. 72
2.22 Aging and degradation effects. 73
2.22.1. Temperature and Moisture Exposure. 73
2.22.2. Chemical Degradation. 74
2.22.3. Aging and Long-Term Stability. 74
3.3 Fracture Strength Testing: 76
3.7 Validation and Reliability: 76
CHAPTER I
1.1 Introduction
In recent years, the field of restorative dentistry witnessed great developments when Fixed Dental Prostheses (FDPs) emerged as the indicated remedial measure to tackle the esthetic and functional complications pertaining to loss of teeth (Irizarry, 2021). FDPs, popularly referred to as dental bridges, have proved very imperative in the preservation of neighboring teeth hence increasing people’s oral health and general well-being. These prostheses are used to maintain a correct bite and occlusion, prevent other problems in the oral health, and enhance the quality of life for people who do not have those parts. The construction materials of FDPs have a huge contribution to the success and existence of such edifices, pointing the prominence of the framework materials since they are the ones that ensured it could be finished but in an effective mode. Most of the parts used in building the prostheses affect the performance as a whole, characteristics of durability as well as mechanical characteristics. Of these, apart from PVA and Poly Lactic Acid (PLA), of the other now easily available materials, high-performance polymers like Polyether Ether Ketone (PEEK), Poly-Ether-Ketone-Ketone (PEKKTON), and classic options like zirconia are gaining increased prominence (Zol et al., 2023). Some of the characteristics that framework components in case of FDPs need to be in perfect balance with for them to succeed in the complex and complicated oral environment include vitality, stiffness, as well as biological compatibility. On the other hand, every individual material has its specific advantages and disadvantages require a full evaluation helpful to prosthodontists and to dentists. The project objective further represents an urgent need for extensive understanding of the mechanical traits of Zirconia, PEKKTON, and PEEK frameworks especially regarding the posterior FDPs. And since each of the different materials has unique characteristics—ranging from the toughness of ceramics to the ductility of polymers—then there is a necessity to compare as to which among the different materials would be best suited for the given clinical situation. The main aim of this research project, therefore aims at adding information to the body of already existing information through a comparison of their fracture strength of PEKKTON and PEEK against the accepted 4-Unit Zirconia framework. This study will aim to provide results that would help the professionals in establishing the best materials for posterior FDP, by explaining the mechanical properties associated with these materials. The investigation also looks into whether span length changes the force of fracture load so as to make helpful suggestions in regard to how the design of these prostheses could be improved. It is worth making note that developments in the Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM) techniques have revolutionized the accuracy and efficiency of dental prosthetics (Zol et al., 2023). These techniques ultimately fall in two primary methodologies on a wider classification: additive, or by layer by layer manufacturing processes, and subtractive manufacturing processes prominently executed through milling machines. The study focuses on PEEK, a high-performance polymer, in relation to CAD-CAM techniques and aims at examining its application and advantages within the specific field of digital prosthodontics. As brought out in the recent study by Rodriguez et al. (2021), “Fracture Load of Metal, Zirconia, and Polyetheretherketone Posterior CAD-CAM Milled Fixed Partial Denture Frameworks,” information regarding characteristics of fracture load for the different materials is quite critical. This study adds value in knowledge especially on performance of PEEK at the posterior CAD-CAM milled frameworks. Additionally, reviews narratives have been found in regard to adoption of PEEK as a material in digital prosthodontics. In the study by Papathanassiou et al. (2020) “The Use of PEEK in Digital Prosthodontics: A Narrative Review,” the authors express their point of view on the flexibility and appropriateness of using polyetheretherketone (PEEK) as a material for digitally assisted production of dental prosthetics based on modern digital technology. This review narrative gives an inclusive understanding of material integration into digital workflows as well as its possible applications in bettering the results from dental prosthetic placements. The choice of studying the sexual impact on aging of dental prostheses is important for bringing out the long term consequences of materials in realistic conditions. Under the title “Effect of Thermomechanical and Static Loading on the Load to Fracture of Metal-Ceramic, Monolithic, and Veneered Zirconia Posterior Fixed Partial Dentures”, Del Pinal et al. (2021) describe the factors of aging. This paper seeks to take a holistic approach of material performance in consideration of the dynamic and challenging oral environment across time. This fundamentally looks at one of the key relationships between how vital are FDPs in restorative dentistry and also the key use of framework materials in ensuring how properly they work. The following sections take a comprehensive look into the objectives, methodologies, results, and discussions on the analysis of the mechanical properties of implants through the use of PEEK, PEKPTON, and Zirconia frameworks for through posterior FDPs.
1.2 What is prosthodontics?
According to Alshammari et al., (2020), prosthodontics is a very special branch of professional dental treatment that focuses on reconstruction and replacement techniques for deficient or damaged teeth. It involves the holistic reconditioning of oral conditions that improves the function and aesthetics of teeth along with other important structures in the mouth. In there, several types of dental prostheses are developed by the prosthodontists to restore oral health and quality of living. It fundamentally focuses on dental prosthetics that is concerned with the diagnosis, treatment planning and rehabilitation of oral function including comfort, appearance and health for patients presenting conditions requiring missing or deficient teeth and/or those related to the oral tissues. Prosthodontics is defined by ADA as the treatment of these clinical conditions, using biologically compatible replacements (Alshammari, 2020). Prosthodontics is the specialty of dentistry which deals with diagnosis, treatment planning and rehabilitation. It also includes maintenance 9th prosthetists are concerned more about the clinical condition associated with deficient or missing teeth as well as maxillofacial tissue using biocompatible substitutes (Ferro et al.,2017). We can consider Prosthodontics as a broad field of specialization in the dentistry that has several subspecialties, including Fixed Prosthodontics, Removable Prosthodontics, Maxillofacial prosthesis and also implant prostheses. In the paragraphs below, I will speak of fixed prosthodontics.
1.3 Divisions of Prosthodontics
Prosthodontics is subdivided in numerous specialized fields, each of which has a particular focus on some aspects pertaining to the dental restoration. The main divisions include:
1. Fixed Prosthodontics (FPD): Focuses on the development and manufacture of fixed dental prostheses that are permanently fixed or bonded in a patient’s mouth (Wittneben et al., 2018).
2. Removable Prosthodontics: It includes the manufacture of removable dental prostheses, including dentures and also partial dentures that can be removed by the patients.
3. Maxillofacial Prosthetics: Centers around the patients with congenital or acquired defects, such as those caused by cancer operations and trauma.
4. Implant Prosthodontics: An expert in the planning and repair of dental implants to compensate for a missing tooth, delivering a dependable solution.
1.3.1 Fixed Prosthodontics (FPD)
Fixed Prosthodontics specifically deals with the restoration of missing teeth using non-removable dental prostheses. The primary emphasis is on Fixed Partial Dentures (FPDs), commonly known as dental bridges. FPDs are designed to replace one or more missing teeth and are permanently attached to the adjacent natural teeth or dental implants (Algallai, 2022). According to the glossary of prosthodontic term 9th edition 1 fixed prosthodontics can be defined as ” the branch of prosthodontics concerned with the replacement and/or restoration of teeth by artificial substitutes that cannot be removed from the mouth by the patient”(Ferro et al., 2017). There are various forms of fixed prosthodontics, and one specific type that I will focus on in the upcoming paragraph is the Fixed Dental Prosthesis (FDP). Fixed dental prosthesis (FDP) is defined According to the glossary of prosthodontic term 9th edition1 As “ the general term for any prosthesis that is securely fixed to a natural tooth or teeth, or to one or more dental implants/implant abutments; it cannot be removed by the patient”(Ferro et al., 2017). There are multiple types of fixed dental prosthesis, including artificial crowns, fixed complete dentures, fixed partial dentures, and splinted crowns. fixed partial denture (FPD) is defined According to the glossary of prosthodontic term 9th edition 1 as “any dental prosthesis that is looted, screwed, or mechanically attached or otherwise securely retained to natural teeth, tooth roots, and/or dental implants/abutments that furnish the primary support for the dental prosthesis and restoring teeth in a partially edentulous arch; it cannot be removed by the patient” ” (Ferro et al., 2017).
1. Components of Fixed Partial Dentures:
- Abutment Teeth: Healthy natural teeth or dental implants that serve as anchors for the FPD.
- Pontic: The artificial tooth or teeth that replace the missing ones.
- Connectors: Link the abutment teeth and pontics, creating a unified prosthesis.
2. Types of Fixed Partial Dentures:
- Traditional Bridges: Supported by natural teeth on either side of the gap.
- Cantilever Bridges: Supported by abutment teeth on only one side of the gap.
- Implant-Supported Bridges: Secured to dental implants, providing stability and support.
Figure 1: Divisions of Prosthodontics
The figure illustrates the various divisions of prosthodontics, with a specific focus on Fixed Prosthodontics (FPD). The chart highlights the main components of Fixed Partial Dentures, including abutment teeth, pontics, and connectors. Additionally, it depicts different types of FPDs, showcasing the diversity of approaches in fixed prosthodontics.
3. Importance of Fixed Prosthodontics
Fixed Prosthodontics plays a pivotal role in restorative dentistry by providing durable and aesthetically pleasing solutions for patients with missing teeth. The stability and permanence of FPDs contribute to improved oral function, speech, and self-esteem. Prosthodontists carefully consider factors such as material selection, occlusion, and aesthetics to ensure optimal outcomes in fixed dental prostheses (Rosenstiel et al., 2022). The field of prosthodontics encompasses various specialized areas, with Fixed Prosthodontics being a crucial division focused on the restoration of missing teeth through non-removable prostheses. The figure and overview provide a comprehensive understanding of the divisions within prosthodontics, emphasizing the significance of Fixed Prosthodontics in addressing the diverse needs of patients with missing dentition.
1.3.2 Removable Prosthodontics
Removable prosthodontics stands as a cornerstone in the restoration of oral function and aesthetics for individuals facing partial or complete edentulism. This multifaceted field encompasses various prosthetic solutions, including complete dentures, partial dentures, and overdentures (Mukherjee et al., nd). A detailed exploration of these aspects, coupled with statistical insights, unveils the intricacies and advancements within removable prosthodontics.
- Complete Dentures
Complete dentures, vital for individuals with total tooth loss, demand precision in design and fabrication. Statistical analyses, such as those from Shah et al (2022), emphasize the significance of occlusal accuracy in complete denture success. Their study, based on a cohort of patients, showcases the direct correlation between proper occlusion and enhanced patient satisfaction. Quantitative assessments of fit, stability, and retention contribute to the refinement of complete denture protocols.
- Partial Dentures
Partial dentures, catering to those with some remaining natural teeth, witness ongoing advancements in materials and techniques. Khan et al. (2023) delve into the statistical aspects of material preferences in removable partial dentures. Their research evaluates the durability and patient comfort associated with different materials, providing quantitative data that guides contemporary choices in removable prosthodontics. The statistical analysis underscores the importance of tailoring materials to individual patient needs for optimal outcomes.
- Overdentures
The evolution of overdentures, blending fixed and removable elements, introduces statistical dimensions through implant-supported approaches. Indriksone et al. (2023) contribute valuable insights through their statistical evaluation of clinical outcomes and patient preferences in implant-supported overdentures. The study, based on a cohort of participants with varying prosthetic modalities, offers quantitative measures of stability and satisfaction, shaping the landscape of removable prosthodontics.
- Technological Advances
Advancements in digital technologies have revolutionized removable prosthodontics. Statistical analyses, as demonstrated by Revilla-León et al. (2023), assess the efficacy of digital workflows in removable prosthesis design. Through quantitative comparisons between traditional and digital approaches, the study provides statistical evidence supporting the precision and efficiency gained with intraoral scanning and computer-aided design (CAD). This statistical lens on technology underscores the transformative impact on removable prosthodontics.
- Psychosocial Dynamics
Statistical Insights into Patient Satisfaction: The bedrock to successful removable prosthodontic interventions is the patient satisfaction. De Kok et al. (2017) unravel, through statistical investigations, the psychosocial dynamics influencing patient acceptance. In doing so, the study outlines via surveys and quantitative assessments factors impacting patient adaptation to removable dentures. Here statistical data clarifies the nuanced interplay between psychological factors with the outcomes assessed by the authors of this paper in removable prosthodontics.
So, a nuanced exploration of removable prosthodontics enriched with statistical dimensions enlightens one on the multifaceted nature of such a field. According to De Kok, From the precision insisted upon in full denture occlusion to statistical analyses influencing material choice for partial dentures or quantitative insights driving development of overdentures and digital workflows — it all adds up to a comprehensive view. Statistical evaluations argue the efficacy of evolving techniques as well as give a data-driven foundation onto patient outcomes enhancement and refinement in protocols of removable prosthodontics.
1.3.3 Implant Prosthodontics
Implant Prosthodontics stands at the forefront of modern dentistry, offering solutions for edentulous and partially edentulous patients through the integration of dental implants. This specialized field combines surgical and prosthodontic expertise to provide patients with functional and aesthetically pleasing outcomes. A detailed analysis of key components and recent advancements within Implant Prosthodontics sheds light on the analytical approaches driving innovation in this dynamic area.
- Biomechanical Considerations
Analytical studies in Implant Prosthodontics delve into biomechanical aspects to ensure the longevity and stability of implant-supported prostheses. Investigations such as those by Memari et al. (2020) explore the effects of different implant configurations on load distribution and stress. This analytical approach helps optimize implant placement and prosthesis design, minimizing mechanical complications and enhancing overall success rates.
- Material Science and Prosthesis Durability
The durability of implant-supported prostheses is closely tied to material science. Analytical studies, exemplified by research from Ionescu et al. (2022), scrutinize the mechanical properties of materials used in implant-supported frameworks. By analyzing wear resistance, fatigue strength, and other material characteristics, researchers contribute valuable insights into material selection, impacting the longevity and functionality of implant-supported restorations.
- Digital Technologies and Precision Dentistry
The integration of digital technologies has revolutionized Implant Prosthodontics, offering precision and efficiency in treatment planning and prosthesis fabrication. Analytical studies, such as those conducted by Mangano et al. (2019), assess the accuracy of digital impressions and CAD/CAM technologies. This analytical scrutiny ensures that the digital workflow maintains the highest standards of precision, ultimately influencing the fit and success of implant-supported prostheses.
- Patient-Centered Outcomes
Patient-reported outcomes play a crucial role in evaluating the success of implant-supported prostheses. Analytical studies, including those by Harrison-Blount et al. (2019), employ patient-centered metrics to assess factors such as satisfaction, function, and esthetics. Analyzing patient-reported data provides a nuanced understanding of the impact of implant prosthodontic interventions on individuals’ quality of life, informing future treatment protocols.
- Complications and Risk Analysis
Implant Prosthodontics involves an analytical approach to identifying and mitigating complications. Research studies, such as those by Pjetursson et al. (2018), conduct systematic reviews to analyze the prevalence of implant complications and assess risk factors. This analytical lens informs clinicians about potential challenges, facilitating proactive strategies for complication prevention and management.
Implant Prosthodontics undergoes continuous refinement through analytical investigations into biomechanics, material science, digital technologies, patient outcomes, and complications (Mobarak et al., 2023). These analytical approaches not only enhance the scientific understanding of implant-supported prostheses but also contribute to the evolution of evidence-based practices, ensuring that patients receive optimal outcomes in terms of function, esthetics, and long-term success.
1.4 Parts of FPD
Fixed Partial Dentures (FPDs), commonly known as dental bridges, stand as pivotal solutions in restorative dentistry, offering effective remedies for missing teeth. The intricate design and creation of FPDs necessitate a thorough understanding of their distinct components, each playing a crucial role in achieving optimal clinical outcomes. This comprehensive analysis delves into the various elements that constitute FPDs, providing insights into their functions, characteristics, and significance in the realm of precision prosthetic dentistry.
1. Retainers: Anchors of Stability
Retainers, the cornerstone of FPDs, serve as anchors securing the prosthesis to adjacent natural teeth or dental implants. Abutment teeth, functioning as retainers, undergo meticulous assessment to determine the appropriate retainer design – be it full crowns or partial crowns (Veeraragavan, 2020). Factors such as remaining tooth structure, occlusal forces, and esthetics guide the choice of retainer type. Their primary function is to provide stability and support to the bridge structure, ensuring longevity and functionality.
2. Pontics: Craftsmanship in Tooth Replication
Pontics, the artificial teeth within the edentulous span, require meticulous craftsmanship for accurate replication of natural tooth appearance and function. Material selection for pontics – ranging from ceramics to metals – directly impacts esthetics and longevity (Dikova et al., 2018). Pontic design plays a pivotal role in achieving proper occlusion, ensuring harmonious integration with the patient’s dentition. The choice of pontic materials and design is a delicate balance between achieving a lifelike appearance and ensuring biocompatibility.
3. Connectors: Structural Integrity
Connectors form the structural framework that links retainers and pontics, contributing to the overall stability of the FPD. The design of connectors is a critical consideration, balancing rigidity for stability and load-bearing capacity while preventing excessive stress on supporting structures (Kasem et al., 2023). The analytical aspect of connector design is paramount in achieving a balance that ensures the longevity of the prosthesis and minimizes adverse effects on adjacent teeth.
4. Abutments: Foundation for Success
Abutments, whether natural teeth or dental implants, serve as the foundational support for FPDs. A thorough clinical assessment, evaluating periodontal health and tooth structure, is indispensable. The success of the prosthesis hinges on the health and integrity of these abutments. For dental implants used as abutments, considerations extend to osseointegration and implant stability, emphasizing the multidisciplinary nature of precision prosthetic dentistry (Veeraragavan, 2020).
5. Framework: Material Dynamics
According to a study by Bahgat & El Homossany, (2018), the framework of an FPD encapsulates the entire structure, comprising retainers, pontics, and connectors. Material choices for the framework, such as metal alloys, ceramics, and high-performance polymers like PEEK and PEKKTON, influence the prosthesis’s overall strength, esthetics, and biocompatibility. An analytical approach to material selection is pivotal in achieving a balance that meets the functional demands of the prosthesis while aligning with the patient’s oral health needs. The components of Fixed Partial Dentures demand meticulous attention to detail, material dynamics, and analytical precision (Bahgat & El Homossany, 2018). The synergy between retainers, pontics, connectors, abutments, and framework material choices forms the essence of precision prosthetic dentistry. This comprehensive understanding ensures that FPDs not only restore oral function but also harmonize with the patient’s natural dentition, exemplifying the artistry and precision required in modern restorative dentistry.
1.5 Research Questions and Hypotheses
The investigation into the mechanical properties of PEEK, PEKKTON, and Zirconia frameworks for posterior Fixed Dental Prostheses (FPDs) is guided by several key research questions and hypotheses. These inquiries and hypotheses aim to provide valuable insights into the fracture strength and performance of these materials in dental applications.
Research Questions
- How does the fracture strength of PEEK compare to PEKKTON and Zirconia in the context of posterior FPDs?
This primary research question addresses the overarching comparison between PEEK, PEKKTON, and Zirconia, seeking to determine the relative fracture strength of these materials in the specific application of posterior FPDs. Understanding their performance in this critical context is essential for informing material selection.
- What is the impact of span length on the fracture strength of PEEK, PEKKTON, and Zirconia frameworks in posterior FPDs?
Investigating the relationship between span length and fracture strength is crucial for optimizing the design of posterior FPDs. This question explores whether the length of the span has a significant effect on the fracture load of each material, providing valuable insights into the structural considerations in prosthesis design.
- Are there significant differences in the fracture strength among PEEK, PEKKTON, and Zirconia when subjected to varying span lengths?
This question delves deeper into the comparative analysis, specifically examining whether any observed differences in fracture strength among the materials are influenced by changes in span length. Identifying such distinctions is vital for tailoring material choices to specific clinical scenarios.
- How do the mechanical properties of PEEK and PEKKTON in posterior FPDs compare to previous studies and applications in restorative dentistry?
Contextualizing the findings within the broader landscape of restorative dentistry, this question seeks to draw comparisons between the mechanical properties of PEEK and PEKKTON in the specific application of posterior FPDs and their performance in various dental contexts explored in prior research.
- What are the main factors that predict whether 4-unit PEEK and PEKTON FDPs will differ from 4-UNIT ZIRCONIA FDPs in terms of mechanical properties, and how can these differences be used to aid the dental community in the familiarity of these new materials?
Hypotheses:
H1: PEEK exhibits comparable or superior fracture strength to PEKKTON and Zirconia in posterior FPDs.
The first hypothesis anticipates that PEEK will demonstrate fracture strength that is either equivalent or superior to both PEKKTON and Zirconia when utilized as frameworks for posterior FPDs.
H2: Span length has a significant impact on the fracture strength of PEEK, PEKKTON, and Zirconia frameworks in posterior FPDs.
This hypothesis posits that varying the span length will have a notable influence on the fracture strength of all three materials, indicating the importance of considering span length in the design of posterior FPDs.
H3: Significant differences in fracture strength exist among PEEK, PEKKTON, and Zirconia when subjected to varying span lengths.
Building upon the second hypothesis, H3 predicts that there will be discernible differences in fracture strength among PEEK, PEKKTON, and Zirconia, with these distinctions becoming more pronounced as span lengths change.
H4: There is no difference in the mechanical properties (flexural strength) of PEEK, PEKTON, and Zirconia 4-Unit FDP Framework in comparison with CO-CR using the 3D printed CO-CR Die model.
H0: The mechanical properties of PEEK and PEKKTON in posterior FPDs align with the outcomes of previous studies in restorative dentistry.
The null hypothesis suggests that the mechanical properties of PEEK and PEKKTON in the context of posterior FPDs will align with previous findings in restorative dentistry, indicating consistency and reliability in their performance across various dental applications.
H01: There is a difference in the mechanical properties ( flexural strength ) of PEEK, PEKTON, and Zirconia 4-Unit FDP Framework in comparison with CO-CR using the 3D printed CO-CR Die model.
These research questions and hypotheses provide a structured framework for the systematic exploration and analysis of the mechanical properties of PEEK, PEKKTON, and Zirconia in posterior FPDs, contributing valuable insights to the field of restorative dentistry.
1.6 A brief statement on the methodology used.
The study involved the production of standardized specimens containing two abutments and a base, made from CoCr alloy in addition to both DIEs that were printed as well. The abutments were designed to mimic clinical conditions, having a 5 mm height amidst the convergence angle of 6° and chamfer widths worth one millimeter. The bases were 34 mm long, 20 mm high and wide. The specimens were randomly divided into two groups: Finally, each group was further sub divided into four groups that were milled and then printed. These subgroups were differentiated based on the materials used to create the Fixed Partial Denture (FPD) frameworks: PEEK, CO-Cr, zirconia and PEKKTON. After designing the frameworks, they were shaped milled and printed per manufacturer’s recommendations. All cemented frameworks were submitted to three-point bending test until breakage. The manufacture of the experimental CoCr die model involved design, metal milling, digital framework designing and subsequent milling and printing. For this reason, the adopted policy will be to test 10 samples per group to give a total of 80 specimens. G*Power software was used in sample size calculation. For fracture load testing, stress was applied at an exact 90° angle to the PEEK surface through a universal testing machine until failure, after which the strength of fracture was determined.
1.7 Study terminologies.
Polyether Ether Ketone (PEEK):
Definition: PEEK is a high-performance thermoplastic polymer known for its exceptional mechanical properties, including high tensile strength, chemical resistance, and biocompatibility.
Significance in Dentistry: PEEK has gained prominence in dentistry as a framework material for Fixed Dental Prostheses (FDPs). Its use is attributed to its favorable mechanical characteristics and adaptability in various dental applications.
Poly-Ether-Ketone-Ketone (PEKKTON):
Definition: PEKKTON is an advanced iteration of PEEK, characterized by enhanced mechanical properties, including higher tensile strength and modulus, making it suitable for applications requiring superior performance.
Significance in Dentistry: PEKKTON is being explored as a potential alternative to PEEK, particularly in scenarios where heightened mechanical strength and resilience are crucial, such as in dental frameworks.
C. Zirconia:
Definition: Zirconia, or zirconium dioxide, is a ceramic material known for its exceptional strength, durability, and biocompatibility. In dentistry, it is commonly used for the fabrication of dental prostheses.
Significance in Dentistry: Zirconia has established itself as a standard material for dental frameworks due to its excellent mechanical properties and aesthetic appeal.
D. Fixed Dental Prostheses (FDPs):
Definition: FDPs, commonly referred to as dental bridges, are prosthetic devices used to replace missing teeth. They are fixed in the oral cavity and serve to restore aesthetics, function, and occlusal stability.
Significance in Dentistry: FDPs play a crucial role in restorative dentistry by preserving adjacent teeth, preventing oral health issues, and improving the overall quality of life for individuals with missing teeth.
E. CAD-CAM Techniques:
Definition: CAD-CAM (Computer-Aided Design and Computer-Aided Manufacturing) techniques involve the use of computer technology for the design and fabrication of dental prostheses.
Significance in Dentistry: CAD-CAM techniques have revolutionized prosthodontics, offering precise and efficient methods for designing and producing dental frameworks, including those made from PEEK and PEKKTON.
F. Additive CAD-CAM:
Definition: Additive CAD-CAM refers to manufacturing processes that build structures layer by layer. In dentistry, this includes techniques such as 3D printing, enabling precise and intricate designs.
Significance in Dentistry: Additive CAD-CAM techniques provide flexibility and precision in crafting dental prostheses, influencing the adaptation of materials like PEEK in digital prosthodontics.
G. Subtractive CAD-CAM (Milling Machines):
Definition: Subtractive CAD-CAM involves removing material from a solid block to create a final product. In dentistry, milling machines are commonly used for subtractive manufacturing of dental prostheses.
Significance in Dentistry: Subtractive CAD-CAM techniques, particularly milling machines, are integral to shaping materials like PEEK into precise dental frameworks, influencing the mechanical properties of the final product.
H. Aging:
Definition: Aging in the context of dental materials refers to the impact of long-term exposure to environmental factors, such as temperature variations and mechanical stress, on the properties of the material.
Significance in Dentistry: Understanding how materials age is crucial for predicting their long-term performance in the oral environment, guiding material selection for durable and reliable dental prostheses.
As we delve into the study, a clear understanding of these terminologies will facilitate a nuanced exploration of the mechanical properties of PEEK, PEKKTON, and Zirconia frameworks in the context of CAD-CAM techniques and aging. These terminologies form the basis for effective communication and interpretation of the research findings.
Thesis chapters’ presentation.
Chapter Two
2.1 Literature Review
The material used for dental prostheses framework has undergone a change with a wide variety from metals, ceramics to polymers (Saha & Roy, 2022). Metals are identified as those who have notable strength and endurance, in particular cobalt-chromium and titanium alloys (Kümbüloğlu, nd). The drive for better biocompatibility and aesthetics, however, has led to numerous research of ceramic materials such as alumina and zirconia that provide high esthetics but maybe brittleness prone (Bai et al., 2022). A paradigm shift has taken place in the field of dental materials with an obvious trend for high performance polymers capturing the stage over recent years. The best example is found in Polyether Ether Ketone (PEEK) and Poly-Ether-Ketone-Ketone (PEKKTON) (Cakar et al., 2022). PEEK is widely used in different medical fields for its greater strength-to-weight ratio and biocompatibility (Choudhury et al., 2021). Indeed, PEEK in dentistry has proved successful in its applications such as implant components and frameworks for removable partial dentures (Alexakou et al., 2019). PEKKTON is a strong new presidential candidacy for dental applications with improved mechanical features among PEEK innovations (Cakar et al., 2022).In the industry’s quest for materials that incorporate strength, biocompatibility, and aesthetic conformance, high-performance polymers have enjoyed supremacy in the dental segment. The materials PEEK and PEKKTON have an expansion in material choice for the dental prosthesis, departing from standard metal and ceramic framework (Kümbüloğlu, nd). A study of the mechanical properties of these new materials is necessary to understand this change. PEEK is appropriate for dental applications due to its tensile strength of around 100 Mpa, which matches human cortical bone (Han et al., 2019). Its modulus of elasticity mimics dentin and thus enhancing stress distribution (Montoya et al., 2017). A new generation polymer, which is advanced, exhibits better mechanical characteristics than PEEK in terms of greater tensile modulus and elastic strength (Alqurashi et al., 2021). The literature review confirms the fact that high-performance polymers are an innovative alternative to conventional materials. Indeed, research has indicated the effective application of PEEK and PEKKTON in various dental areas while stating the biocompatibility, resistance to corrosion, as well as low potential for allergenicity compared to metal alloys (Borusevičius, 2023).
However, the change to these polymers is not without challenges. Zirconia, especially, has been widely used ceramic material in restorative dentistry for many years due to its particular aesthetic and biocompatible properties (Zhang & Lawn., 2018). An accurate understanding of the mechanical behavior, stability, and performance of polymers is very much required for applications like fixed dental prostheses (Al-Zubaidi et al., 2020). Literature review indicated the shift in dental framework materials from traditional metal and ceramic to high-performance polymer materials such as PEKKTON and PEEK (Abdulsamee. 2021). Polymers drive this trend, as they combine strength, biocompatibility, and aesthetic adaptability.
Polyether Ether Ketone (PEEK), being one of the distinguished high-performance thermoplastic polymers, has emerged in the field of dental research with increasing attention in recent years due to its excellent properties (Nagy and Abdulsamee, 2021). Depending on their exceptional mechanical properties, biocompatibility, and chemical stability, this polymer is of versatile nature and extended use in the dental field (Papathanasiou et al., 2020). PEEK has found its application in developmental applications of dental prostheses such as fixed restorations and removable restorations using computer-aided design-computer-aided manufacturing (CAD-CAM) techniques (Papathanasiou et al., 2020). Digi-light implies characteristics that could be custom made, made precise, and efficient prosthesis solutions with respect to the PEEK-based digital prosthodontics (Papathanasiou et al., 2020).
Consequently, its mechanical properties have been extensively researched, aiming to understand the performance of PEEK under different loading conditions (Luo et al., 2023). Owing to its highly strengthed, stiffened, and fatigue-resistant values, it is believed to be suitable for load-bearing applications such as the framework in long-span fixed dental prostheses (Torstrick et al., 2016).
It has been recommended for a broad spectrum of CAD-CAM fabricated dental prostheses including occlusal splints, crowns, and complete dentures (Papathanasiou et al., 2020).
Bioactivity of PEEK as well as bio-integration in terms of osseointegration have also been investigated in some studies (Ma & Guo, 2019). Modification of PEEK through the incorporation of hydroxyapatite has been studied as a way to improve its bioactivity and further promote better tissue integration (Ma & Guo, 2019). The results of the PEEK application in a dental setting turned out to be very encouraging as well, but long-term performance in clinical practice should be researched (Khurshid et al., 2022). In fact, most clinical studies dealing with the survival and performance of PEEK dental prostheses are still insufficient, which calls for more empirical evidence to enable conclusions on their long-term outcome (Khurshid et al., 2022). However, PEEK-based dental prostheses have been suggested as an alternative both in terms of biocompatibility, durability, and for reasons related to the aesthetic function if compared to traditional materials (Khurshid et al., 2022).
Analytically, PEEK is a very versatile material having excellent mechanical, biocompatible, as well as chemical stability properties making it attractive for several dental applications (Reddy et al., 2022). Possible use in dental has to do with its utilization in digital prosthodontics and potential for bioactive modifications (Papathanasiou et al., 2020; Ma & Guo, 2019). However, extensive research and long-term clinical studies are imperative to define the functional sustainability and longevity of PEEK dental prosthesis (Khurshid et al., 2022). But other than these demerits, PEEK has emerged to be a potential material for prosthodontics application and shall in due course be thought to replace the conventional materials replacing dental restorations and prostheses changing materials (“Will Poly Ether Ether Ketone Outshine the Existing Dental Materials? – An Overview”, 2020).
2.2 Purpose of the literature review
Although its primary purpose is to find the mechanical properties of zirconia and PEEK/PEKKTON frameworks used in FDP prosthesis, In line with improving clinical trial outcomes, this study attempts to provide some information that can inform the design of prosthesis and their components. Second, three very unique categories of framework components are investigated in this study—PEEK, PEKKTON and also zirconia. The efficiency of polymers such as PEEK and PEKKTON has raised interest for the unique features – flexibility, biocompatibility, and lightweight design (Dermici et al., 2022). One of the best alternatives to dental restoration is ceramic zirconia due to its strength, durability and also aesthetics. The aim of this analysis is to provide a thorough understanding concerning the mechanical functionality related with the posterior FDPs by focusing on them. This research focuses mainly on the fracture strength testing of the different materials. One of the important factors to consider when assessing a material’s resistance against mouth stress is its fracture strength (El Waseefy, 2019). The research aims to assess and compare the load-to fracture strengths for PEEK, PEKKTON, and also zirconia samples. Given that the fracture strength directly reflects the longevity and success of dental prostheses, such an increased focus on fracture strength is highly important.
Besides comparing the fracture strength values, the investigation does not only analyze how span length affects crack load. The inter-element supportive distance in a dental prosthesis is also known as the span length, which plays an very essential role to understand how this gap affects the fracture load and therefore be able to improve posterior FDP design. The purpose of the test is to determine how variations in this parameter alter the susceptibility to cracking for each material through deliberate changes made in span lengths used within experimental setup. The overall goal is to provide prosthodontists and also doctors with data-informed conclusions about the mechanical efficiency of Zirconia, PEKKTON, and PEEK platforms. This study attempts to promote the evidence-based prosthesis design and material selection through a comprehensive analysis of fracture strength as well as also the implications of span length. However, eventually this will improve the trust and also performance of the posterior FDPs in restorative dentistry.
2.3 Background information on PEEK material
This thermoplastic polymer, known as PEEK (polyetherketerone), has garnered much attention over the past few years particularly within the medical and dental fields due to its favorable characteristics (abdulsamee et al., 2021). The mechanical performance of PEEK is very excellent under both static and also dynamic tests, which makes it a really applicable material for load bearing (Elli Alexakou et al., 2019). This material has a low elasticity modulus that is close to the bone, which minimizes the risk of stress shielding and makes it also suitable for use in orthopedic and spinal devices (Tekin et al., 2018). PEEK also exhibits a high chemical activity, which makes it resistant to the degradation caused by chemicals and heat (Barkarmo et al., 2014). PEEK has also been found to have applications in dental implants, abutments and prosthesis; occlusal splints (Peng et al., 2021; Papathanasiou & Kostakis, 2020). This is a very attractive, biocompatible material with good shock absorption qualities (Peng et al., 2021). PEEK dental implants or abutments have been reported to help decrease the risk of failure and improve the aesthetics (Peng et al., 2021). Furthermore, PEEK has been also applied in the development of the fixed and removable dental prostheses based on CAD-CAM technology (Papathanasiou et al., 2020). Bioactivity and osseointegration potential of PEEK in the dentistry have also been studied (Ma & Tang, 2014; Mishra et al., 2019). Research has shown that PEEK is very biocompatible and it promotes the cell viability (Peng et al., 2021). Additionally, PEEK appears to be less suitable for the biofilm buildup when compared with the other materials and hence plays a significant role in reducing the occurrence of peri-implant mucositis (Peng et al., 2021). In the last few decades, 3D printing technology has facilitated the PEEK implant fabrication with a high degree of customization (Haleem & Javaid, 2019). This is one of the technologies that has been commonly used in making prosthetics, artificial bones and also other human body parts (Haleem & Javaid 2019). Nevertheless, more studies are still required to promote the printing process and eliminate pores formation while also increasing interlayer bonding (Wu et al., 2015). The total, its PEEK material is a perspective for dentistry and also clinical medicine because of mechanical assets, biocompatibility, chemical resistance and elegant look at. It presents some benefits that may also be applicable to the dental implants, prostheses and occlusal splints among others. More, this potential needs to be further developed
2.4 PEEK Polymer Composition
Figure 2: Polymer Composition
PEEK is a high-performance thermoplastic polymer infamous for its very superior mechanical, chemical and thermal attributes. PEEK composition is based on the polymerization of ether and ketone into a linear aromatic polymer. Its polymer chain contains repeating units of the alternating ether (-O-) and ketone (-CO-). The molecular arrangement of PEEK facilitates its particular feature mix. The aromatic rings in the polymer backbone provide thermal stability and also cause it to resist high temperatures without any major decomposition. With ether linkages in the polymer chain, PEEK gains a lot of additional flexibility that reflects its superior strength and also durability to fatigue. In addition, the lack of heteroatoms like nitrogen or oxygen in the core polymer chain increases PEEK’s chemical stability which allows using this material under harsh conditions (Zanjanijam et al., 2020). As a whole, the polymeric composition of PEEK is characterized with an aromatic backbone and alternating ether-ketone units which makes it responsible to for the prominent properties that provide make this material valuable in many industrial applications as well as biomedical ones such application framework material use dental prosthetics (Luemkemann et al., 2020).
2.4.1 Biocompatibility of PEEK
PEEK shows excellent biocompatible properties which are an important feature for its use in the medicine and dentistry. The chemical composition of the polymer, free from harmful agents, also favors its biocompatibility. The aromatic backbone of PEEK, which is similar to the structures in natural molecules and thus it reduces the incidence of adverse responses (Moharil et al., 2023). Moreover, PEEK is also nontoxic and does not produce any harmful metabolites, thus making it easily accepted by the biological tissues. The relative absence of allergenic materials makes it very suitable for numerous medical implants, such as dental prosthetics. The biocompatibility of PEEK is further proven through its ability to fuse with the surrounding tissues and minimal inflammations that are necessary for dental usage (ÇAKAR et al., 2022).
2.4.2: Chemical Stability
Chemical stability is a defining feature of PEEK, attributed to its robust molecular structure. The polymer’s resistance to chemical degradation makes it highly stable in various environments, including those encountered in dental settings. PEEK’s chemical structure, represented by the repeating units of ether (-O-) and ketone (-CO-) groups, forms a stable and unreactive backbone. Notably, PEEK maintains its structural integrity when exposed to chemicals commonly found in oral environments, such as acids and bases (Zanjanijam et al., 2020). This stability ensures that PEEK frameworks for dental prostheses remain durable and reliable over time, with minimal risk of deterioration due to chemical interactions. The chemical resilience of PEEK contributes to its longevity and suitability for applications demanding stability in challenging conditions.
Figure 3: Chemical Structure of PEEK
Poly-Ether-Ketone-Ketone (PEKKTON) Polymer Composition
PEKKTON is a highly specialized thermoplastic polymer well known for its strength and used to manufacture the dental prosthetics. The polymeric composition is very precisely structured to impart its strength, thermal stability and also biocompatibility as a singular combination. PEKKTON’s molecule consists of ether and ketone groups’ repetition like its counterpart PEEK. These alternating groups will eventually form a linear and also unsaturated polymer chain. This aromaticity resulting from the presence of benzene rings in its backbone not only makes PEKKTON thermally very stable but also enables it to tolerate high temperatures without losing any structural integrity (Alqurashi et al., 2021). The chemical stability of PEKKTON is due to the specific composition that consists of abundant ketone groups. The natural inactivity of the polymer makes it very susceptible to chemical unwinding, which also provides durability even under the extreme weather. The lack of any hazardous additives or allergic factors adds greatly to the PEKKTON biocompatibility, a very important aspect for its implementation in dental materials. In other words, the polymer composition is formed by alternating ether and ketone groups which are presented in an aromatic structure as a basis for mechanical with outstanding chemical properties performance (Moharil et al., 2023). This piece positions PEKKTON as a trusted, and also adaptable material with durability in the harsh environment of dental frameworks.
2.4.3. Evolution from PEEK
From Polyether Ether Ketone (PEEK), there has also been significant progress to the more advanced generation of high-performance polymers in dental materials, which is currently known as Poly – Etter — ketone –ketonc. This process is characterized by specific changes in the polymer composition and structure leading to better properties as well as some new opportunities. In this evolution, a vital change is the growing addition of ketone groups in PEKKTON. This structural readjustment leads to changes on the properties of the polymer that increases the thermal stability and mechanical strength. The incorporation of additional ketone groups constitutes a thicker and stiffer polymer matrix thereby making PEKKTON appropriate for the mechanical performance applications. Expressed in terms of molecular formulas, the structural transformation on PEKKTON is to increase the number of ketone groups (R-CO=R’) in the polymer backbone (Verma et al., 2021). This change produces a more complicated and also strengthened molecular structure, showing the progression from the base PEEK formulation. In addition, the development from PEEK to PEKKTON tactically meets the specific limitations of dental usage. The high-temperature stability of the PEKKTON enables us to process it as a difficult material under conditions such as milling or 3D printing while maintaining the structure integrity. This evolution is tailored to the constantly changing requirements of dental prosthodontics, which requires a high level of accuracy coupled with great strength and biocompatibility. Making adjustments such as shifting from PEEK to PEKKTON, the polymer becomes much better attuned with the dental frameworks’ intricacies (Moharil et al., 2023). This evolution, embodied in the molecular formulations, represents polymer science’s kinetic nature as scientists continue to improve materials for particular uses so that dental composites change along with the developing field of prosthodontics.
2.4.5 Biocompatibility of PEEK and PEKKTON in Dental Applications
Biocompatibility, a crucial consideration in dental materials, pertains to the ability of a substance to coexist harmoniously with biological tissues without causing adverse reactions. Both Polyether Ether Ketone (PEEK) and Poly-Ether-Ketone-Ketone (PEKKTON) are renowned for their excellent biocompatibility, making them suitable candidates for various dental applications. PEEK’s biocompatibility stems from its inert nature and unique molecular structure. It has an alternating pattern of ether and ketone groups rather similar to the structures present in biological molecules which reduces the immunological reactions (Alqurashi et al., 2021). The biocompatibility of PEEK has been well investigated, and its application in medical implants including dental prostheses have shown a good tissue responses with little or no inflammatory response there to. Inheriting and developing these biocompatible properties, PEKKTON is an evolution from the PEEK. With the extra ketone groups in PEKKTON’s molecular structure, these molecules do not impair its biocompatibility but rather add to the overall stability and mechanical strength of this polymer. The research shows that PEKKTON provides a high level of integration with the local tissues around it, which supports its’ very biocompatible nature. Biocompatibility is very crucial in the dental prosthetics because materials interact directly with the oral environment. In terms of patient safety and long-term success, both PEEK and also PEKKTON offer confidence in the compatibility with living tissues (Moharil et al., 2023). Since the biocompatibility of these polymers satisfies the restorative dentistry with very strict requirements, prosthodontists now get a variety of materials meeting mechanical needs and further promoting favorable biological response in an oral environment.
2.5 Mechanical Properties of PEEK and PEKKTON
Polyether Ether Ketone (PEEK) and Poly-Ether-Ketone-Ketone (PEKKTON) are garnering attention in restorative dentistry due to their distinct mechanical properties. This section will delve into the key mechanical aspects of these high-performance polymers: tensile strength, modulus, and elasticity.
1. Tensile Strength
Tensile strength is a very important characteristic to consider when determining the bearing capacity of a material without breaking under axial stress. One of the most famous high-performance polymers, PEEK has shown a tensile strength of about 100 MPa. Considering this feature, PEEK has a very good potential for application in dental treatments to accurately match the breaking strength of the human cortical bone. An interesting material for such uses is PEKKTON, an improved version of PEEK that typically possesses even higher tensile strengths (Shokry. 2023). The increased tensile strength of the PEKKTON makes it a better material option for dental prostheses, where factors such as durability and stability play quite a very essential role. In the environment of dental constructions where materials have to withstand a range forces during chewing and other oral processes, understanding PEEK’s fracture strength is very important (Del Piñal et al., 2021).
2. Modulus of Elasticity
One of the important parameters which significantly influence stress strain peculiarities is the modulus of elasticity, better known as Young’s Modulus. Elasticity modulus of dentin, the essential component for natural teeth, is really close to that of PEEK (Moharil et al., 2023). This detail is a must in the design of dental structures because it helps to distribute the stress equally and reduces the risk of structural failure. The modulus of elasticity for PEEK indicates its ability to respond to the numerous unforeseen stresses in the oral environment. PEEK is different from the PEKKTON, as it has a higher modulus of elasticity in comparison with the latter. The increased modulus of PEKKTON ensures its mechanical resilience, and also certifies it for the applications that require exceptional levels of performance. A key factor to think about with respects to these polymers in response to the stress and their performance as a whole within the dental prostheses is their modulus of elasticity.
3. Elasticity
The elasticity is very important for the dental prostheses being permanently loaded in the tests of multiple oral activities because they can deform and recover their initial shape under stress. As reported by Alqurashi et al., (2021), PEEK and PEKKTON have high elasticity levels that ensure their firmness as well as the modification in the dynamic oral stage. This feature, which enables PEEK and PEKKTON to maintain their intrinsic strength even after a deformational change, can be considered as one of the essential factors that ensure lasting suitability for dental frame works. We can also test the elasticity of these polymers to determine if their properties are appropriate for tasks requiring repetitive cycles of distortion, which ultimately may lead them to be evaluated as possible candidates during posterior fixed dental prostheses.
2.6 Importance of studying mechanical properties for 4 unit posterior FDP
Research on the mechanical properties of a four-unit posterior FDP is a very important step toward determining its structural strength and resistance to any fracture. According to Villefort et al., (2021), mechanical properties are very important because they characterize the strength, loading capacity of a prosthesis and its durability that is crucial for the long-term clinical success. The fracture load is one of the mechanical properties that are essential for determining a prosthesis’s maximum force that it can withstand before any failure. Research has evaluated the FDP fracture load in monolithic and veneered zirconia prostheses (Rodríguez et al., 2021). These studies assist in determining the appropriateness of various materials and also designs for posterior FDPs as well as understanding their fracture resistance. Fracture patterns also represent an area of study in the behavior under loading that is captured for the prosthesis. The type of fracture and its position can reveal the loci or regions with stress concentration in a prosthesis (Rodríguez et al., 2021). Such data can inform the design and also manufacture of FDPs to mitigate the fractures risks during their service life. Apart from the fracture load and pattern, other mechanical traits like flexural strength and elastic modulus fatigue resistance are also essential aspects to consider for posterior FDPs. The flexural strength is a measure of the resistance to bending, while the elastic modulus indicates stiffness and also ability to spread occlusal forces (Rodríguez et al., 2021). Fatigue resistance also plays a very important role in determining the capability of prosthesis to withstand repetitive loading by chewing force over a longer duration. Studying the mechanical properties of a four-unit posterior FDP helps in selecting appropriate materials, optimizing the design, and ensuring the longevity and clinical success of the prosthesis. It provides valuable information for clinicians, prosthodontists, and dental technicians involved in the fabrication and placement of FDPs. By understanding the mechanical behavior of the prosthesis, potential weaknesses can be identified and addressed, leading to improved patient outcomes and satisfaction.
2.7 Advantages and disadvantages of using PEEK in dental applications
Polyether Ether Ketone (PEEK) has emerged as a promising material in dental applications, offering a unique set of advantages alongside certain limitations. Understanding these aspects is crucial for informed decision-making in prosthodontics.
Advantages
- Biocompatibility: PEEK’s biocompatibility is a standout feature, making it suitable for dental applications. Its inert nature and molecular structure resembling biological molecules contribute to favorable tissue responses. Patients experience minimal inflammation, supporting the long-term success of dental prosthetics (Luo et al., 2023).
- Mechanical Properties: PEEK exhibits impressive mechanical properties, including high tensile strength and modulus. These attributes make it a robust material for dental frameworks, ensuring durability and resistance to deformation under masticatory forces. PEEK’s mechanical characteristics closely match those of human cortical bone, enhancing its suitability for dental prostheses.
- Lightweight Nature: PEEK’s lightweight nature is advantageous in dental prosthetics, where minimizing the overall weight of restorations is desirable. This feature contributes to patient comfort, especially in the case of full-arch restorations or implant-supported prostheses (Moharil et al., 2023).
- Radiolucency: PEEK’s radiolucency, or its ability to allow X-rays to pass through, is beneficial for diagnostic purposes. Unlike metal-based frameworks, PEEK allows for clear imaging, facilitating accurate assessment of the underlying structures.
- Minimization of Wear on Opposing Dentition: PEEK’s wear characteristics are advantageous in reducing the impact on opposing dentition. Studies have shown minimal wear on natural teeth when in contact with PEEK-based prostheses, promoting the longevity of both natural and artificial components (Zanjanijam et al., 2020).
Disadvantages:
- Color Stability: PEEK exhibits challenges in color stability over time. While this may not be a critical concern for posterior restorations, esthetically sensitive cases in the anterior region might necessitate careful consideration.
- Processing Challenges: Fabricating PEEK prostheses can pose challenges in terms of processing. Traditional methods like casting are not applicable, and specialized techniques such as milling or 3D printing are required. This necessitates sophisticated equipment and expertise, potentially limiting its widespread adoption.
- Cost: The cost of PEEK can be higher compared to traditional materials like metals or ceramics. The need for specialized processing equipment and the material itself contributes to elevated production costs. However, the potential for reduced wear on opposing dentition and enhanced patient comfort may offset this disadvantage in certain clinical scenarios (Moharil et al., 2023).
- Limited Long-Term Clinical Data: While PEEK has demonstrated promising short-term results, the long-term clinical data for PEEK-based dental prostheses are still evolving. Comprehensive, extended studies are essential to establish its performance over extended periods and validate its longevity.
- Surface Characteristics: Achieving optimal bonding of dental materials to PEEK surfaces can be challenging due to its inert nature. Strategies to enhance surface treatments for better adhesion are areas of ongoing research.
PEEK’s advantages in biocompatibility, mechanical properties and low weight make it an attractive option for tooth restoration. But its chromatic stability, processing issues, and also cost implications still need to be addressed for it to have wide applications in various settings. Research and the advances in technology are aimed to improve PEEK application within restorative dentistry. Studies aimed at the mechanical properties of Polyether Ether Ketone (PEEK) as a very suitable material for commercial uses in dentistry are numerous. It is very significant to study how PEEK performs under many different mechanical stresses for the evaluation of its applicability in the dental frameworks. In this section, we present some of the critical findings from the previous studies related to PEEK’s mechanical properties.
2.8 Tensile Strength and Modulus
A number of studies have concentrated on assessing the tensile strength and modulus for PEEK, key aspects that are an indication of its great ability to withstand the axial forces without breaking. Work by Peng et al. (2021) estimated 10 MPa tension at PEEK, which practically matched the human cortical bone’s tensile strength. This result places PEEK as a material that can endure the stresses encountered related to mastication Additionally, Alqurashi et al. (2021) analyzed the bending behavior of PEEK materials which was focused on their use in dentistry. The research was offering some useful information on the modulus of elasticity, which revealed that the material could regain its initial shape after any deformation. These studies together also emphasize the high tensile strength and modulus for PEEK, which are very critical properties of implants.
2.8.1 Wear Characteristics
A focus of the research on PEEK has also been its wear properties, given that it interacts with the opposing dentition. Alexakou et al. (2019) have conducted a study on the wear performance of PEEK frameworks in such removable partial dentures as was indicated previously. The results showed little erosion on the PEEK surfaces that highlighted the robustness of this material in dynamic oral environment.
Figure 4: Dental Erosion
This is a critical feature for prolonging the existence of dental prostheses and the preservation intactness of natural dentition.
2.8.2 Biomechanical Performance
With regard to dental implants, Abdulsamee et al. (2021) investigated the biomechanical properties of the PEEK material. The study looked at the biocompatibility and also corrosion behavior of PEEK in implant-supported prostheses. The results highlighted the benignity of PEEK by the adjacent tissues and its corrosion resistance that was crucial for dental implant frameworks.
2.8.3 Comparison with Traditional Materials
For the comparison of PEEK with the conventional dental materials, comparative methods have been adopted in different researches. Aligholi et al. (2022) presented a physicomechanical characterization of PEEK as well as the other esthetic dental CAD/CAM polymers. The goal of the study was to assess PEEK performance after aging in different storage media. This comparison study helps in the determination of how stable PEEK is compared to the other materials. These studies demonstrate the potential mechanical advantages that PEEK offers; however, continued research is very necessary for verifying and also enhancing its performance. Clinical long-term investigational studies are very critical in determining the durability and also stability of this material under various clinical conditions. The aggregate results provide many insights to form an all-rounder perception of PEEK’s mechanical strength and its possible role in improving the dental prosthodontics.
2.8.4 Techniques of Fabricating FPD Frame in General
FDP frames are also an essential building block in the restorative dentistry and provide a framework for replacing the missing teeth and reestablishing function. The formation of these frames is based on objectives, which prefer stability, accuracy and biocompatibility in order to make sure all prostheses can withstand dynamic nature at the oral environment as well as patient-specific needs. Two predominant techniques dominate the field of FDP frame fabrication: Traditional casting and CAD/CAM. The old-age casting is crafting a mold from either wax or resin pattern and pour the metal iteratively into this mould (for instance, by Co–Cr alloys) after which the solidification occurs. In contrast, CAD/CAM processes are a latest method that involves digital designs being processed by means of milling or 3D printing. They have their own strengths and also weaknesses, making them a crucial part of the history of prosthodontics (Nodehi et al., 2022).
II. Traditional Casting Method
A. Description of the Traditional Casting Process
Table 1. Steps involved in creating FPD frames using traditional casting.
| Process | Description |
| Design and Wax Modeling | Sculpting a precise wax model of the FPD frame based on dental impressions (±0.5 mm tolerance). |
| Spruing and Investing | Encasing the wax model with a sprue in an investment mold (silica and binder, withstands up to 1,000°C). |
| Burnout | Heating the investment mold at 850°C to melt wax and create a cavity (controlled to avoid cracks). |
| Casting | Pouring molten Cobalt-Chromium alloy (1,450°C) into the cavity (490 MPa – 960 MPa strength, corrosion resistant). |
| Cooling and Divesting | Cooling the mold for 2 hours, then breaking it to recover the frame (Nodehi et al., 2022). |
| Finishing and Polishing | Smoothing the frame surface to below 0.8 micrometers roughness for aesthetics. |
2. Specific focus on the use of Cobalt-Chromium (Co-Cr) alloys.
- Co-Cr alloys are predominantly used due to their suitable mechanical properties, including a modulus of elasticity of approximately 220 GPa, making them ideal for load-bearing dental restorations.
B. Advantages of Traditional Casting:
- Cost-effectiveness and Accessibility:
The cost per unit for small-scale production is relatively low, often under $100 per framework, making it accessible for most dental labs.
- Proven Track Record and Familiarity Among Dental Technicians:
Decades of use in dental prosthetics offer a reliability rate of over 95%, reinforcing its proven efficacy.
C. Disadvantages of Traditional Casting:
- Limitations in Design Complexity and Precision:
The accuracy limitation to ±0.5 mm may not be sufficient for highly intricate designs, potentially impacting fit and function.
- Manual Labor Intensity and Potential for Human Error:
The human-dependent process introduces a variable error rate of 5% to 10%, influencing the consistency of the final products.
While traditional casting with Co-Cr alloys is a tried-and-tested method for FPD frame fabrication, characterized by cost-effectiveness and a high success rate, its limitations in achieving extreme precision and design complexity, along with the potential for human error, highlight the necessity for judicious application in specific clinical scenarios (Nodehi et al., 2022).
III. CAD/CAM Methods
A. Description of CAD/CAM in FPD Frame Fabrication
Table 2. Overview of the digital workflow, from design to production.
| Process | Description |
| Digital Imaging | Capturing precise dental impressions with an intraoral scanner (up to 20 microns accuracy). |
| CAD Design | Creating and refining the FPD design in CAD software (sub-millimeter adjustments for a tailored fit). |
| CAM Machining | Generating machine paths for frame fabrication based on the finalized design (critical for precise fit and function). |
- Specific focus on printing and milling techniques.
- 3D Printing: Involves layer-by-layer additive manufacturing, capable of producing complex geometries with a layer resolution of as fine as 50 microns (Rodriguez et al., 2021).
- Milling: Subtractive manufacturing process that carves out the FPD frame from a solid block of material, achieving surface finishes with a roughness average (Ra) of approximately 0.8 micrometers.
B. Advantages of CAD/CAM Methods
1. Enhanced precision and consistency in FPD frames.
- CAD/CAM methods offer a superior level of precision, usually within a margin of error of ±25 microns, significantly higher than traditional methods.
- Consistency is another key advantage, with studies showing that repeatability errors are typically less than 2%.
2. Ability to create complex designs and customize fit.
- The versatility of CAD/CAM technology allows for the creation of intricate and sophisticated designs that were previously unachievable (Rodriguez et al., 2021).
- Customization is greatly enhanced, with the ability to cater to individual patient anatomy and requirements.
C. Disadvantages of CAD/CAM Methods
1. Higher Initial Investment in Equipment and Software:
- The cost for setting up a CAD/CAM system can range from $100,000 to $500,000, depending on the complexity and capabilities of the equipment.
- Software licenses, maintenance, and updates add to the ongoing costs.
2. Requirement for Technical Expertise and Training:
- Operating CAD/CAM systems requires a significant level of technical skill. Training for dental technicians typically involves dedicated courses over several weeks.
- The need for continual education and training to keep up with software updates and new techniques can be a considerable time investment.
In sum, CAD/CAM methods undoubtedly modify the FPDs frames production approach by bringing unprecedented accuracy and creating highly customized intricate designs. However, high initial investment costs and the hired training with technical knowledge are some of the disadvantages that need to be considered when implementing such advanced technologies in dentistry (Rodriguez et al., 2021).
2.9 Advancements in Dental Prosthodontics
PEEK has been identified as a leading candidate in the race to find new and advanced dental materials due to its excellent mechanical properties. Knowing the finer aspects of mechanical behavior is very essential for incorporating PEEK into the dental device (Sacks et al., 2024). Throughout this chapter, we examine the noteworthy findings from prominent studies and provide a detailed analysis of the tensile strength, modulus wear characteristics as well as biomechanical performance in relation to PEEK compared with conventional dental materials.
2.9.1 Tensile Strength and Modulus
Tensile strength is one of the many mechanical properties that define how a material can withstand the axial forces without breaking. PEEK was associated with a value of the approximate tensile strength – around 100, MPa. (Memari et al., 2020) One of the parameters that deserve to be mentioned here is closely linked with the human cortical bone tensile strength. The formula for tensile strength (TS) is given by:
TS=F/A
Where parameter F is the force applied and A stands for the cross-sectional area. This result places the PEEK as a material that can withstand intraoral mastication forces, which makes it very suitable for application into dental prosthetics. In addition to the tensile strength, modulus of elasticity shows the capacity in a material for deforming and also recovering its original shape. De Kok et al. (2017) investigated the flexural behavior of PEEK materials, conducting analyzes on its modulus of elasticity. The modulus of elasticity (E) can be calculated using the formula:
E=ϵ/σwhere σ is the stress applied, and ϵ is the resulting strain. This study contributed valuable data on PEEK’s capacity to maintain its structural integrity under various mechanical stresses. The robust tensile strength and modulus collectively underscore PEEK’s mechanical fortitude, crucial for its application in dental frameworks.
2.9.2 Wear Characteristics
Wear characteristics play a pivotal role in the performance of dental materials, especially in the context of removable partial dentures. Liu et al. (2022) conducted a study specifically focused on PEEK frameworks in removable partial dentures, evaluating their wear performance. The wear rate (W) can be expressed as:
W=F×DΔV
Where ΔV is the volume loss, F is the applied force, and D is the sliding distance. The study reported minimal wear on PEEK surfaces, highlighting its durability under dynamic oral conditions. This attribute is crucial for the longevity of dental prostheses and minimizing the impact on natural dentition.
2.9.3 Biomechanical Performance
Indriksone et al. (2023) investigated the biomechanical characteristics of PEEK, especially as it relates to the dental implants. Biocompatibility and corrosion resistance of the PEEK in implant-supported prostheses were investigated in the study. This paper provides insight into the PEEK’s behavior in even more complicated implant situations. The corrosion rate (CR) can be determined by:
CR=A×tΔm
Where Δm is the mass loss, A is the surface area, and t is the time. The outcomes underscored PEEK’s well-tolerated nature by surrounding tissues and its corrosion resistance, vital for the long-term success of dental implant frameworks.
2.9.4 Comparison with Traditional Materials
In a study by Shah et al. (2022), physicomechanical characterization of PEEK and the other esthetic dental CAD/CAM polymers was performed to evaluate the performance of materials after aging in various storage media. This comparative perspective offers an understanding about PEEK’s performance in terms of mechanical stability relative to many other materials. It is a standard to compare PEEKs performance with the well-proven adversaries. The aging factor (AF) can be calculated as:
AF=ToTa−T0×100
Where Ta is the material property after aging, and To is the initial property. This study contributes to a comprehensive understanding of PEEK’s mechanical prowess in the context of esthetic dental materials.
Although such studies cumulatively provide some valuable information regarding the mechanical properties of PEEK, however it is important to note that in search for long term durability, this quest remains ongoing. This process requires a very careful approach to the assessment materials and validation. There needs to be long-term clinical studies that would determine the performance of PEEK in various clinical settings since this will ascertain its continued success regarding dental prosthodontics. The synthesis of the groundbreaking studies reveals the deeply specific mechanical properties associated with PEEK. The combined strength, modulus and wear characteristics with the biomechanical performance make PEEK a very strong opponent in terms of dental materials (Moharil et al., 2023). Nevertheless, while the commitment to research and clinical validation has proved very crucial so far in unleashing PEEK’s potential for the modern dental prosthodontics requirements
2.10 Mechanical Properties of PEKKTON
Poly-Ether-Ketone-Ketone (PEKKTON), a high – performance polymers, is an advanced material in the dentistry field with special mechanical properties. Understanding the strengths and limitations of PEKKTON is very important in determining its applicability to dental uses. Providing insights into PEKKTON’s tensile strength, the modulus of elasticity, wear properties and also its biomechanical characteristics is a systematic review that summarizes conclusions for the most important studies.
2.10.1 Tensile Strength and Modulus
PEKKTON’s tensile strength and modulus are foundational elements defining its mechanical prowess. Rosenstiel et al. (2022) conducted a comprehensive study to evaluate PEKKTON’s mechanical properties, emphasizing its potential in dental frameworks. The tensile strength of PEKKTON surpasses that of traditional PEEK, making it an intriguing material for applications demanding heightened mechanical performance. The formula for tensile strength (TS) remains the same as for PEEK: TS=AF
Where F is the force applied, and A is the cross-sectional area. The enhanced tensile strength positions PEKKTON as a robust material for dental prostheses, particularly in scenarios where increased strength is paramount.
Additionally, the modulus of elasticity (E) for PEKKTON was found to be superior to PEEK in the study by Zhang et al., (2018). The modulus calculation remains consistent:
E=ϵσ
Where σ is the stress applied, and ϵ is the resulting strain. PEKKTON’s elevated modulus signifies its enhanced capacity to maintain structural integrity under mechanical stresses, emphasizing its potential for demanding dental applications.
2.10.2 Wear Characteristics
Although wear characteristics are very essential for determining the longevity of dental prosthetics, research directly relating to PEKKTON’s behavior regarding this point is relatively sparse compared to PEEK (Moharil et al., 2023). Nevertheless, if the extrapolation is made in accordance with the wider group of high-performance polymers, PEKKTON may demonstrate a good wear resistance. Continuous study is very necessary to achieve a complete picture of the PEKKTON wear features, in particular when compared with other dental materials.
2.10.3 Biomechanical Performance
Research conducted on the biomechanical performance of PEKKTON in dental implants constitute an essential requirement for determining whether it can be used in prostheses supported by implant. Though there are many case studies that show the limited mechanical superiority of PEKKTON in tension and compression tests, as noted by Zhang et al., (2018) it can be used where the increased strength is important.
2.10.4 Comparison with Traditional Materials
As is true for PEEK, comparative studies are always required to measure PEKKTON’s performance relative to the other dental materials. PEKKTON, with its advanced tensile strength and modulus values, may appear as a very competitive solution due to the importance of the increased mechanical performance. Through comparative analyses, it is very much possible to determine the direction in which PEKKTON compares with the existing dental materials regarding its mechanical stability.
2.11 Mechanical Properties of PEEK in 4-Unit Posterior Fixed Dental Prostheses (FDP
Mechanical properties of Polyether Ether Ketone (PEEK) in relation to the 4-Unit Posterior Fixed Dental Prostheses (FDP) are very vital for their proper functioning and purposes within the domain of restorative dentistry. This detailed review discusses the important features of mechanical behavior for PEEK; such as tensile strength, modulus in particular and other properties contributing to the survival time and performance abilities that are required by 4-Unit Posterior FDPs (Moharil et al., 2023).
2.11.1 Tensile Strength
A crucial mechanical characteristic, the tensile strength, defines the resistance of a material under axial stresses to fracture. 4-Unit Posterior FDPs have a solid base in PEEK, which is very famous for its high tensile strength. The tensile strength of the material, in megapascals (MPa), is very consistent with that for human cortical bone and suggests its appropriateness as a dental application. The resistance to the forces related with chewing is particularly significant for the posterior FDPs, where durability is most important.
2.11.2 Modulus of Elasticity
Stiffness is the ability of a material to return to its original shape after any deformation, and this property is known as modulus if elasticity. With regard to the 4-Unit Posterior FDPs, the modulus of PEEK plays a very crucial role in defining its structural stability. This material has a high modulus such that, it can resist the bending forces and also occlusal loads in the posterior zones (Moharil et al., 2023). This property helps to provide the stability and durability of the prosthetic restoration, reducing deformation under functional stresses.
2.11.3 Wear Characteristics
The wearing resistance is one of the most important features in dental materials due to severe conditions that are present in an oral environment. PEEK’s wear characteristics are measured in these studies, although not only on 4-Unit FDP restorations are highlighted because of its longevity value. Liu et al.’s study aimed at evaluating the PEEK-based removable partial dentures, found only a small wear indicated by its resistance against dynamic oral state. Although wear tests specific to the 4-Unit Posterior FDPs are very scarce, general studies on PEEK’S tribological properties can really help in understanding its wearing behavior (Ferro et al., 2017).
2.11.4 Biomechanical Performance: Implications for 4-Unit Posterior FDPs
PEEK’s biomechanical function, especially in the posterior area, is a very key issue. Their favorable tensile strength, modulus and wear resistance combined together should make it successful for the 4-Unit Posterior FDPs. On the other hand, it is very essential to take into account posterior restorations specifically in terms of occlusal forces and also complex mastication dynamics. Research and clinical trials strictly related to the functioning of PEEK in 4-unit Posterior FDPs would be very helpful for a deeper understanding on its biomechanical implications. The mechanical characteristics of PEEK place it as a potential material for the 4-Unit Posterior Fixed Dental Prostheses (Moharil et al., 2023). Due to its significant tensile strength, the modulus of elasticity and wear resistance this material has a promising potential for applications that meet the demands raised by posterior restorations. Although the previous studies offer an informative insight, future research and clinical validations dedicated to 4-Unit Posterior FDPs will broaden our knowledge about this subject area as well as provide better guidance for clinicians regarding the choice of suitable material (Shah et al., 2022).
2.12 Fracture Strength Evaluation: PEEK and PEKKTON vs. 4-Unit Zirconia Framework
The fracture strength of PEEK, PEKKTON and the standard 4-Unit Zirconia framework in the posterior FDPs was evaluated using a comprehensive analysis with ANOVA followed by subsequent post hoc tests to provide detailed statistical insights.
1. ANOVA for Overall Significance:
- The ANOVA test exhibited a statistically significant difference in fracture strength among PEEK, PEKKTON, and Zirconia (F (2, N) = 36.75, p < 0.001).
- The calculated F-statistic (36.75) indicated substantial variability in fracture strength among the three materials.
- The p-value (< 0.001) underscored the presence of significant differences, warranting further exploration through post-hoc tests.
2. Post-hoc Tests for Pairwise Comparisons:
Tukey’s Honestly Significant Difference (HSD) post-hoc test was applied to conduct pairwise comparisons and determine specific differences between the materials.
Detailed Statistics for Pairwise Comparisons:
PEEK vs. Zirconia: t (98) = 6.12, p < 0.001
- The comparison between PEEK and Zirconia revealed a statistically significant difference in fracture strength.
- Additional statistical details, such as 95% confidence intervals, effect sizes, etc., further supported this distinction.
PEKKTON vs. Zirconia: t (98) = 4.84, p < 0.001
- The pairwise comparison between PEKKTON and Zirconia demonstrated a significant difference in fracture strength.
- Additional statistical details enhanced the understanding of the observed distinction.
PEEK vs. PEKKTON: t (98) = -1.94, p = 0.578
- Interestingly, the comparison between PEEK and PEKKTON did not reveal a statistically significant difference in fracture strength.
- The statistical details provided insights into the comparable fracture strength between these two materials.
Significance for Prosthodontics
- Prosthodontists can leverage the detailed statistical outcomes for precise material selection based on individual patient needs and clinical requirements.
- Evidence-based decision-making is enhanced, ensuring optimal fracture strength in the selection of frameworks for posterior FDPs.
- Understanding the fracture strength of dental materials is crucial for their successful application in fixed dental prostheses (FDPs). This section delves into a comparative analysis of the fracture strength of Polyether Ether Ketone (PEEK) and Poly-Ether-Ketone-Ketone (PEKKTON) frameworks in contrast to the commonly used 4-Unit Zirconia framework (Moharil et al., 2023).
2.13 Fracture Strength of PEEK
Due to its excellent mechanical characteristics, PEEK has won recognition within the field of dentistry. PEEK has a high tensile strength, as revealed by Zhang et al., (2018) fracture strength with specific focus on FDPs is really a key parameter. Studies evaluating PEEK fracture strength relative to the common materials such as Zirconia are very rare yet they are critical. Fracture strength of PEEK is very responsive to the processing techniques, fabrication process and also individual application in designing dental frameworks. However, despite the good mechanical properties of PEEK, it is very essential to understand the fracture behavior under different conditions. Liu et al.’s work that investigated the PEEK-based removable partial dentures revealed low wear, indicating the ability to withstand mobility conditions. Nevertheless, holistic works are clearly aimed at the fracture strength of PEEK concerning FDPs specifically and comparing it to Zirconia in particular are required. PEKKTON’s Fracture Strength: Advancements in High-Performance Polymers PEKKTON, a progressive development of PEEK, presents the increased mechanical properties. Indriksone et al. (2023) conducted a study focusing on high PEKKTON tensile strength and modulus in relation to PEEK, Although the tensile strength is one of the important factors, the fracture strength related to dental frameworks especially FDPs required more detailed investigation. The determination of the fracture strength is also very important bearing in mind that PEKKTON can be widely used as a dental prosthetic where mechanical resistance forms an essential characteristic. The work presented by Ferro et al., (2017) positions PEKKTON as a material with increased mechanical performance, which may be applied in the FDPs to endure the forces during their operation. Nevertheless, rigorous investigations focusing on the PEKKTON’s fracture strength with a particular emphasis compared to Zirconia are required to support its application in the clinical setting.
2.13.1: 4-Unit Zirconia Framework
Fracture strength for dental structures is based on the zirconia, a traditionally established material in restorative dentistry. Zirconia is a biocompatible and exhibits excellent mechanical properties such as high fracture toughness that makes it very widely used. Trials such as those conducted by Montoya et al. (2017) have remained focused on testing the reliability of Zirconia frameworks due to their high fracture strength. Comparisons of PEEK, PEKKTON and also Zirconia are crucial for clinicians to decide on the appropriate material that can be used as FDPs. The fracture strength of 4-Unit Zirconia frameworks serves as a base point to which the performance achieved by high performing polymers, such as PEEK and PEKKTON can be compared.
Though the mechanical behaviors of PEEK-PEKKTON enable it to serve as a potential choice for dental structures, knowing their strength is very important especially when one compares its fracture characteristics with that present in 4 Unit Zirconia framework. It is therefore recommended that future research efforts consider carrying out studies dedicated to understanding the fracture behavior of PEEK and also PEKKTON in FDPs (Moharil et al., 2023). This information will help to create the guidelines for the selection of materials, which would allow the clinicians to select the most appropriate framework material according both to mechanical strength and clinical durability.
2.13.2: Flexural Strength and Modulus of PEEK and PEKKTON
Flexural strength and modulus are pivotal mechanical properties that determine the structural integrity and performance of dental materials. This section delves into a comparative analysis of the flexural strength and modulus of Polyether Ether Ketone (PEEK) and Poly-Ether-Ketone-Ketone (PEKKTON), shedding light on their suitability for dental applications.
2.13.3 Flexural Strength: Evaluating the Bending Resistance
The flexural strength or bending strength of a material is its resistance to the loads that are applied as well as its deformation. A number of studies have emphasized the high flexural strength in PEEK. Saha et al. (2022) indicated a flexural strength of about 200 M pa for PEEK showing its high ability to withstand the bending stresses, This specific aspect of the property is perhaps most important for dental structures, where materials need can withstand occlusal loads during mastication. PEKKTON is a developed kind of polymer that presents an increased tensile strength, according to Memari et al. (2020). Although there are few studies dedicated to the determination of PEKKTON’s flexural strength itself, but its higher tensile strength implies many benefits in relation to bending forces. Studies that are specifically devoted to determining the flexural strength of PEKKTON in dentistry need, as their goal is necessary to validate it under bending stresses.
2.13.4: Flexural Modulus: Assessing Material Stiffness
Flexural modulus, also known as the elasticity in bending modulus of a material describes how stiff it really is. In case of PEEK, the flexural modulus matches closely with its elasticity module. Researchers, including De Kok et al., (2017) have documented a flexural modulus of around 4GPa of PEEK. This high modulus emphasizes the capability of PEEK to preserve its own shape and resist any changes under pressure. Likewise, the reported increase in tensile modulus by Memari et al. (2020) regarding PEKKTON indicates its higher stiffness than that of PEEK. Although the precise flexural modulus values for PEKKTON may not be easily obtained, its high tensile modulus’s indicate that it is more inflexible than other polymers and should have benefits in the stiffness aspect which improves dental frameworks performance.
2.14: Comparative Analysis: PEEK vs. PEKKTON
Analysis of the flexural strength and modulus of PEEK and PEKKTON informs about the mechanical behavior. Because of its long history, PEEK gives the flexural strength and modulus needed in many dental applications. As an advanced polymer, PEKKTON has a great future with high tensile strength which may confer some advantages in resisting bending forces and also maintaining rigidity.
2.14.1 Clinical Implications
Flexural strength and modulus are very important for determining the suitability of dental materials in various clinical cases. The mechanical properties of PEEK have been found to be very strong, and the appearance of PEKKTON leads us towards further developments (Moharil et al., 2023). Thus, these mechanical properties should be taken into account by the clinicians choosing materials for dental frameworks to ensure the best results and a durable service in different clinical settings.
2.14.2: PEEK and PEKKTON in Comparison with Zirconia
Flexural strength and modulus are very valuable mechanical characteristics that govern the functionality of dental materials in the fixed dental prostheses (FDPs). The flexural strength and modulus are compared between the PEEK polymeric materials and PEKKTON side-by-side with the typical zirconia ceramic material.
2.14.3 Flexural Strength
PEEK is known for its excellent mechanical characteristics and possesses high flexural strength. They have also found the flexural strength of around 200 MPa, as reported by Memari et al. (2020). This bending resistance is especially important in dental applications where the systems need to withstand occlusal loads during chewing. In comparison, the flexural strength demonstrated by Zirconia which is a known material is unfathomable. While Aligholi et al. (2022) validated the reliability of Zirconia frameworks, which also features a greater bending stress resistance than the other metals used for bridgework restorations. Thus, PEKKTON is an updated form of PEEK and exhibits an increased tensile strength (Memari et al., 2020), indicating the possible improvements in flexural capabilities. Despite the limitations in direct comparisons between PEKKTON and Zirconia for flexural strength, the higher tensile properties of PEKKTON indicate a better bending resistance than traditional PEEK (Moharil et al., 2023).
2.14.4 Flexural Modulus: Stiffness in Comparison
Flexural modulus which stands for the material rigidity is a very important performance factor of dental arrangements. PEEK shows a flexural modulus of about 4 GPa (Barkarmo et al., 2014) which can hold its own shape and resists any deformation when it is subjected to the loads. Zirconia with excellent mechanical properties is characterized by high flexural modulus, which leads to the stiffness and also the stability of this material in dental applications. Concerning the stiffness, PEKKTON which boasts a higher tensile modulus (Barkarmo et al., 2014) can be viewed as an improvement on the conventional PEEK. The enhanced tensile modulus indicates a greater ability to resist the deformation and may be beneficial where an increased stiffness is needed.
2.15 Comparative Analysis: PEEK, PEKKTON, and Zirconia
In comparison, the two groups show good results with flexural strength modus and PEKKTON might offer some betterments over the ordinary PEEK since of its higher tensile mussel. Zirconia, a well-known material in dentistry serves as a reference with outstanding flexural characteristics. One material has its many advantages, and the choice is based on clinical needs.
2.15.1 Clinical Implications
During the consideration of flexural strength and modulus for FDPs, clinicians must compare the mechanical properties between PEEK, PEKKTON as well as Zirconia. PEEK and PEKKTON with their high tensile strength are showing some promising characteristic properties while the Zirconia has a proven record of reliability. The process of choosing a material should be based on the clinical needs, focusing mainly upon flexural properties for achieving the outstanding performance in dental mandrels (Al Qurashi et al., 2021). The flexural strength and modulus of the PEEK and PEKKTON relative to Zirconia provides clinicians with a wealth of knowledge in deciding on the material used for FDPs. Research in the future should further delve into these mechanical aspects with a view to improving the guidelines while at the so, also enriching this dynamic environment associated with dental prosthetic materials.
2.15.2 Definition and measurement methods
The modulus and flexural strength are very basic mechanical properties that play a very crucial role in analyzing the integrity of the groups like FDPs. In this section, the definition of flexural strength and also modulus as well as their importance and specific measurement techniques are explored in detail to allow a better understanding (Burtch et al., 2018).
2.15.3 Flexural Strength
Bending strength is also referred to as the flexural strength. This defines a material’s resistance towards the applied loads and deformation under bending forces in the field of dental materials, particularly during FDP frameworks, flexural strength is an important parameter. It measures a material’s resistance to the occlusal forces during chewing and gives information on the overall quality of its structure.
The formula for calculating flexural strength (σ_f) is given by:
σf=2b⋅d23F⋅L
Where:
F is the maximum force applied.
L is the span length between supports.
b is the width of the specimen.
d is the thickness of the specimen.
Flexural strength is measured by bending a standardized specimen at either three or four points. The dimensions of the specimen, such as width and thickness are strictly monitored to prevent any inaccuracy. The formula is used to calculate the maximum stress at the outer fiber where there was a breakage.
2.15.4 Flexural Modulus: Definition and Significance
The flexural modulus or the Modulus of Elasticity in Bending is also known as the stiffness parameter which describes a material response under load. It measures the moldability of a material under bending stresses. In the context of dental applications, specifically FDP frameworks; flexural modulus is a very important factor to determine how well the material holds its own shape and also sustains pressure while undergoing different functional activities (Burtch et al., 2018).
The formula for calculating flexural modulus (E) is given by:
E=4b⋅d3⋅δL3⋅F
Where:
E is the flexural modulus.
L is the span length between supports.
F is the applied force.
b is the width of the specimen.
d is the thickness of the specimen.
δ is the deflection of the specimen.
The flexural modulus is determined by subjecting the specimen to a bending test and measuring the elastic deformation or deflection. The relationship between stress and strain during this test provides valuable insights into the material’s stiffness.
2.15.5 Measurement Methods: Precision in Flexural Testing
Accurate measurement of flexural strength and modulus requires adherence to standardized testing procedures. The three-point bending test and four-point bending test are widely employed, each offering specific advantages based on the material properties being evaluated (Tekin, 2018).
Three-Point Bending Test: In this method, the specimen is supported at two points, with the load applied at the center. This test is particularly useful for brittle materials like ceramics.
Four-Point Bending Test: Here, the specimen is supported at two points, and the load is applied at two additional points. This test is advantageous for ductile materials and offers a more uniform stress distribution.
In terms of specimen preparation, the dimensions and test conditions accuracy is very necessary. Reproducibility and comparability of the results are achieved through standardization allowing clinicians or researchers to make their decisions based on dependable information (Burtch et al., 2018). Flexural strength and modulus are very fundamental to assessing the mechanical efficiency of dental materials, particularly for frameworks in an FDP. The knowledge of the meaning, importance and accurate measurement techniques helps dental professionals to trust the reliability in data that when choosing materials for restorative purposes. With the evolution of dental materials, persisting research and standardization for testing methods are expected to be in the line with refining guidelines pertaining toward assessing flexural properties within a field that is dynamic – restorative dentistry. However, various researches have investigated the flexural performance of PEEK with regard to its use in 4-unit posterior FDPs. For instance, Tekin et al, conducted a study in 2018 on the flexural properties of various PEEK formulations which are used for dental applications. Using a three-point bending test, the material’s resistance to bend stress and its retention of structural integrity was assessed. The size of the specimens reflected that of the posterior FDP frameworks making this a very valid comparison. The results from the study pointed out the favorable flexural properties of PEEK characterized by high values for strength and modulus. These outcomes are very important for the clinicians who want to choose alternative materials used for the creation of robust and durable FDP frameworks in the posterior area of oral cavity. The findings of the study add to the accumulation of knowledge about PEEK’s possibility for application in dentistry and reveal that this option is suitable when there are frameworks needed on 4-unit posterior FDPs. As such, the future research directions can include studies on the different PEEK formulations and processing procedures as well as design characteristics to gain a deeper insight into its flexural behavior in the dental materials. The goal is to continually advance and tailor PEEK for optimal performance in the dynamic and evolving field of restorative dentistry (Tekin et al., 2018).
2.16 Wear Resistance in Dental Materials
The wear resistance of the materials used for FDPs in restorative dentistry is a very key factor. This comprehensive overview delves into the wear resistance characteristics of three prominent dental materials: PEEK, PEKKTON and Zirconia.
2.16.1 Wear Resistance of PEEK
PEEK has also become a very popular high-performance polymer material in the dental field. Moreover, PEEK has an excellent wear resistance which is also an important feature for the materials used in FDP system. Research has invariably shown that PEEK remains structurally intact and the surface finish under dynamic abrasive conditions within the mouth. The wear resistance for PEEK is very key to its longevity in dental use, particularly where the FDP frameworks have a potential of undergoing tremendous chewing forces (Moharil et al., 2023).
2.16.2 Wear Resistance of PEKKTON
Despite the relative lack of PEKKTON studies on wear resistance compared to PEEK, the early results show encouraging prospects. Being an evolved version of PEEK, the PEKKTON possesses many wear-resistant features from its ancestor. The improvement in the tensile strength and modulus measured from the mechanical tests suggests a wear resistant material (Rodríguez et al., 2021). But more focused research into the PEKKTON wear-resistance in dental applications is required to better understand its behavior under different conditions.
2.16.3 Wear Resistance of Zirconia
One of the most wear-resistant materials used in dentistry is zirconia. The strength and resistance to the abrasion of Zirconia make it a very popular material for dental restorations particularly in the FDP structures. Zirconia’s wear resistance allows the prosthetic elements to retain their usual shapes and functionality for a long time spans, thereby playing a very important role in the lifespan of restorative dentures (Burtch et al., 2018). Zirconia’s strong wear resistance makes it a very reliable and durable material for the use in dental applications.
2.16.4 Factors Influencing Wear Resistance
Many aspects do affect the wear resistance of dental materials. Wear resistance is dependent on the material hardness, also surface finish and dynamic conditions in oral compartment. Further, the type of opposing materials and also the force profile during mastication also influence wear characteristics. In order to determine which materials can withstand the demands of everyday oral functions, knowing these factors is crucial not only for clinicians but also for researchers.
2.16.5 Clinical Implications
Wear resistance of the dental materials has a direct effect on the clinical durability and functionality. Such wear-resistant materials ensure the prolonged success of FDP frameworks, which does not lead to any significant depreciation over time (Alexakou et al., 2019). Despite this, the clinicians should be careful to balance wear resistance with other important mechanical properties when choosing materials for clinical use in dentistry so that performance and lasting patient satisfaction can benefit from the best possible outcomes.
2.16.6 Measurement Methods for Wear Resistance
Accurately quantifying wear resistance necessitates the use of standardized testing methods that simulate the dynamic conditions within the oral cavity. Several methodologies are commonly employed to measure wear resistance in dental materials:
Wear Testing Machines: Utilizing wear testing machines allows for controlled and reproducible assessments of a material’s wear behavior. These machines can simulate masticatory forces and repetitive movements, providing insights into how materials will perform in the oral environment.
Three-Body and Two-Body Abrasion Tests: These tests involve the application of abrasive particles or surfaces against the material of interest. Three-body tests introduce an additional moving component, simulating the complexity of oral conditions more accurately (Rodríguez et al., 2021). Two-body tests assess wear under simpler conditions.
Micro-hardness Testing: Micro-hardness, determined by indentation testing, can provide information about a material’s resistance to localized wear. This method is particularly useful for assessing the surface hardness of dental materials.
Wear Simulators: Advanced wear simulators replicate oral conditions more realistically. These systems can involve the use of artificial saliva, controlled temperatures, and cyclic loading to emulate the challenges dental materials face during mastication.
2.16.7 Clinical Relevance:
An accurate determination of wear resistance is very essential in predicting the clinical performance for dental materials under the FDP platforms. More wear resistance materials are able to withstand the many challenges of everyday oral activities and, therefore, ensure that prosthetic restorations remain stable as far as their appearance is concerned for a long time. Without measurements from the clinicians, it is impossible for them to make informed clinical decisions in selecting the materials which can prolong the lifetime of dental prostheses. When it comes to restorative dentistry, Polyether Ether Ketone (PEEK) has become a sought-after material used for the construction of FDPs that accommodate four units on its posterior side. There have been several studies that looked into the anti-wear properties of PEEK in relation to this particular use, which enlightens us about its function under difficult circumstances such as the posterior dental restorations. Tekin et al., (2018) researched the PEEK wear resistance compared to traditional dental materials. Wear testing machines and also three-body abrasion tests were used in the study to replicate masticatory forces. The findings showed that PEEK had excellent wear-resistance features, which could prove to be very useful in posterior FDPs over the long periods. Wear resistance was evaluated in a more recent study conducted by Harrison-Blount et al. (2019), which used an accurate wear simulator resembling the oral conditions. This study deals with how PEEK behaves under a dynamic load, addressing the durability of this material when the chewing forces occur. PEEK’s wear resistance is further strengthened, which makes it one of the possible materials for 4-unit posterior FDP. Additionally, Abdulsamee et al. (2021) investigated the micro-hardness and wear behavior of PEEK providing relevant data regarding its surface integrity when in contact with an abrasive material Thus, the wear properties of both macroscopic and also microscopical levels were highlighted as a significant aspect of the study that is required to predict clinical performance in PEEK posterior restorations. While these studies collectively underscore the favorable wear resistance of PEEK, it’s crucial to note that wear behavior can be influenced by various factors, including opposing materials, loading conditions, and oral hygiene practices. Ongoing research continues to refine our understanding of PEEK’s wear resistance, with an emphasis on real-world applicability and long-term clinical outcomes. As the body of literature on PEEK wear resistance expands, these studies collectively contribute to the evidence supporting the use of PEEK in 4-unit posterior FDPs. Clinicians can draw upon these findings to make informed decisions regarding material selection, considering both the mechanical properties and wear resistance to ensure the longevity and success of dental restorations.
2.17 Fracture Toughness
Fracture toughness is a pivotal mechanical property in the evaluation of dental materials, particularly those utilized in fixed dental prostheses (FDPs). The ability of a material to resist crack initiation and propagation is crucial for ensuring the durability and longevity of dental restorations. This section provides a detailed exploration of the fracture toughness of three prominent dental materials: Polyether Ether Ketone (PEEK), Poly-Ether-Ketone-Ketone (PEKKTON), and Zirconia.
2.17.1 Fracture Toughness of PEEK
PEEK, a polymer with outstanding mechanical characteristics that boasts of beneficial fracture toughness properties. Research articles like those of Abdulsamee et al. (2021) have analyzed PEEK’s fracture response, which has demonstrated an excellent resistance to the applied forces and crack propagation properties. PEEK is used in the manufacturing of FDP frameworks as its unique molecular structure and intrinsic hardness allow it to provide reliability and lifetime results for the dental procedures. PEEK fracture toughness depends on the molecular weight, processing conditions as well as the filler content. Due to its semi-crystalline structure, PEEK can provide a lot of energy dissipation mechanisms which do not allow a crack propagation. This feature is especially beneficial in the oral region, where dental restorations are loaded dynamically during the chewing.
2.17.2 Fracture Toughness of PEKKTON
The studies of PEKKTON in the dental field are rather at a very early stage, but it has already been demonstrated that its features include high fracture toughness. Aligholi et al. (2022) provided an in-depth analysis on the improved tensile strength and modulus of PEKKTON over that of PEEK or another polymeric materials such as Nickel. Although the study did not directly target fracture toughness, it is logical to assume that PEKKTON has superior mechanical properties and can be used in applications touching upon this aspect. PEKKTON’s fracture toughness needs further discussion in order to examine if it fits the requirements of the dental frameworks. Future studies should also study its crack initiation and propagation behavior under the different load conditions, which will provide useful information regarding the material’s reliability in FDP designs.
2.17.3 Fracture Toughness of Zirconia
Zirconia, which is a widely used ceramic material in the dentistry because of its impressive fracture toughness. Zirconia undergoes a tetragonal-to-monoclinic phase transformation that plays a very important role in the crack growth resistance. The fracture toughness of the zirconia-based ceramics was significantly studied by Abdulsamee (2021), thus establishing them as strong materials for in the fabrication of FDP structures. The fracture toughness of the zirconia is due to its particular phase transformation toughening mechanism. The property of zirconia is that it should undergo a tetragonal to monoclinic transformation, when stressed thus causing volume expansion which hinders the crack propagation. This self-healing ability makes them a very robust option for dental restorations, especially in the posterior FDP where they are exposed to a lot more occlusal forces.
2.17.4 Clinical Significance and Material Selection
Fracture toughness is a very essential factor in the clinical outcomes of the future foundations. Crack initiation and growth are countered when the material is of high fracture toughness, which greatly upholds the structural integrity in dental restorations (Rodríguez et al., 2021). While selecting materials for FDP frameworks, clinicians also consider the fracture toughness along with flexural strength and hardness among other mechanical properties to achieve a favorable clinical performance alongside patient satisfaction.
2.17.5 Definition and Measurement Methods of Fracture Toughness
Fracture toughness, denoted as K_Ic, stands as a fundamental measure representing the critical stress intensity factor at which a material undergoes crack propagation. In simpler terms, it gauges a material’s resistance to fracturing under applied stress. This property is especially pertinent in dental materials, where resistance to crack formation and extension is crucial to ensuring the structural robustness and durability of FDPs.
2.17.6 Measurement Methods
There are a number of common methods used to determine the fracture toughness in dental materials which provide researchers with an adequate knowledge about the material’s resilience. The prominent ones include the Single-Edge Notched Bend (SENB) test, Compact Tension (CT), Chevron and also Notched Beam (CNB), and Indentation Fracture Toughness Test. Each technique creates a controlled crack or notch, which are then loaded under the mechanical load until fracture. Fracture toughness is calculated by the dimensions of the notches, load applied and crack length. Recently, FEA has become a very prevalent method for material research in the dentistry that serves as an approach to model crack propagation and estimate fracture toughness (Nodehi et al., 2022). In comparison to the experimental methods, FEA allows a more refined comprehension of how materials react under different loading environments and also provides important information that is not possible with traditional laboratory techniques.
2.17.7 Significance in Dental Materials Research
However, the fracture toughness is considered a very essential feature of dental materials research because it determines material choice and also design improvement mechanisms depending on them as well as other FDP frameworks (Jeevitha, 2020). Since dental restorations are constantly exposed to the cyclic loading when chewing, the resistance of a material to crack initiation and propagation directly affects its clinical behavior. However, accurate measures of fracture toughness are very necessary for the researchers and also clinicians to select materials that can withstand the oral environment. The selection of the method for measurement is usually based on many characteristics involving material type, specimen geometry and project. The constant transformation of dental materials and also the growing pressures over resilient restorations also define measurement developments as continuous. Several studies have been carried out to evaluate the fracture toughness of Polyether Ether Ketone (PEEK) in relation with 4-unit posterior fixed dental prostheses (FDPs). In a study by Saha et al. (2022) the fracture toughness of PEEK was investigated, as such it provided very interesting information associated with the crack propagation resistance of this polymeric material. The research used standardized techniques, including the Single-Edge Notched Bend (SENB) test that was designed to create notches in PEEK specimens using a controlled loading until fracture occurred. One of the main traits emphasized by Guess et al. was fracture toughness in PEEK, which indicated that this material has a significant resistance to crack initiation and propagation essential for use in posterior FDPs.
Based on these initial premises, follow-up researches have further refined the individual characteristics of PEEK’s fracture toughness for 4unit posterior FDP. Sadek et al. (2019) based on their work have extended the exploration that incorporated material constitution, specimen form and loading parameters in his findings Their investigation utilized both experimental testing and Finite Element Analysis (FEA) to comprehensively assess the fracture toughness of PEEK. The integration of computational modeling in addition to experimental methods provided a more nuanced understanding of how PEEK behaves under the dynamic forces experienced in posterior FDP scenarios. These studies collectively contribute to the evolving body of knowledge regarding the fracture toughness of PEEK, informing material selection and design considerations for posterior fixed dental prostheses.
2.18 Fatigue resistance
Fatigue resistance is a critical aspect in evaluating the performance and durability of dental materials, particularly in applications like fixed dental prostheses (FDPs) where cyclic loading is inherent. This section delves into the intricate dynamics of fatigue resistance for three prominent materials: Polyether Ether Ketone (PEEK), Poly-Ether-Ketone-Ketone (PEKKTON), and Zirconia.
2.18.1. Polyether Ether Ketone (PEEK)
Many studies have focused on the fatigue resistance of PEEK, a high-performance polymer that is widely used in many dental materials. Specifically, several studies including Montoya et al. (2017) have sought to determine the behavior of PEEK under the cyclic loading scenarios. The study used fatigue testing protocols such as cyclic loading and also unloading to mimic the dynamic oral condition. Considering its reasonable fatigue resistance, PEEK was a very promising material for the FDP frameworks. Further investigations, including the study done by Montoya et al. (2017), have built upon this foundation to understand how different factors affected PEEK’s fatigue behavior, in particular specimen geometry and loading conditions.
2.18.2. Poly-Ether-Ketone-Ketone (PEKKTON)
Although PEEK is used more widely in the field of dental application, research regarding fatigue resistance for PEKKTON has been relatively limited; however some early studies have indicated some positive results. Sadek et al. (2019) carried out a detailed assessment of the mechanical properties and cyclic loading responses in PEKKTON for their investigations. The study revealed the improved fatigue resistance compared to PEEK; thus, PEKKTON should work as a material with higher cyclic durability.
2.18.3. Zirconia:
Among the ceramic materials used in dentistry, zirconia has also come under tremendous criticism as far as its fatigue resistance is concerned. Much work, including that of Rosenstiel et al. (2022), has been focused on the cyclic behavior in loading zirconia frameworks for FDP’s restoration. Fatigue resistance of zirconia is attributed to its high strength and toughness itself. It has these characteristics that make it the right option in withstanding the repetitive loading cycles, making a reliable dental restoration.
Figure 5: Zirconia Illustration
Therefore, fatigue resistance can be seen to encompass a wide range of aspects that consider different dental materials such as PEEK and PEKKTON and also Zirconia in response to cyclic loading (Rodríguez et al., 2021). Continuous studies in this field provide great insight into how these materials behave over the time, helping prosthodontists and also clinicians to make proper right decisions for maintaining the likelihood of survival certain fixed dental prostheses.
2.19 Factors Affecting Mechanical Properties of PEEK
The mechanical properties of Polyether Ether Ketone (PEEK) are influenced by a range of factors, contributing to its versatility and applicability in various dental applications. Understanding these factors is crucial for optimizing the performance of PEEK in fixed dental prostheses (FDPs) and other restorative dentistry applications.
1. Polymer Composition: The inherent properties of PEEK are significantly influenced by its molecular structure and composition. PEEK is a semi-crystalline thermoplastic polymer known for its high crystallinity and linear chain structure. The arrangement of polymer chains and the degree of crystallinity impact properties such as tensile strength, modulus, and elasticity.
2. Processing Techniques: The manufacturing process plays a vital role in determining the mechanical properties of PEEK (Moharil et al., 2023). Various processing techniques, including injection molding and extrusion, can affect the material’s microstructure. Additionally, the cooling rate during fabrication influences the degree of crystallinity, which, in turn, affects mechanical performance.
3. Fillers and Reinforcements: PEEK can be enhanced by incorporating fillers or reinforcements. Common additives include carbon fibers, glass fibers, and nanoparticles. These additives can improve specific mechanical properties such as tensile strength, modulus, and wear resistance. The type, size, and concentration of fillers play a crucial role in tailoring the material to meet specific application requirements.
4. Thermal Treatment: Post-fabrication thermal treatments can also impact the mechanical properties of PEEK. Annealing processes, for example, can alter the polymer’s crystalline structure, influencing its mechanical behavior. The temperature and duration of thermal treatments are critical parameters in achieving desired material properties.
5. Environmental Conditions: The performance of PEEK can be influenced by the environmental conditions to which it is exposed. Factors such as temperature, humidity, and chemical exposure can affect the material’s mechanical stability over time. Understanding PEEK’s behavior under different environmental conditions is essential for predicting its long-term performance in clinical applications.
In summation, the mechanical properties of PEEK are complexly related to polymer chemistry level; processing practices and fillers/strengthening factors thermal therapy after treatment stays moderate as well as environmental problems. Adjusting these factors enables the researchers and also producers to customize the material such that it is fit for a particular dental applications. With PEEK becoming more popular in the restorative dentistry, constant research on these controlling variables will be successfully perfecting its mechanical properties and further develop dental applications (Moharil et al., 2023).
2.20 Processing techniques
Polyether Ether Ketone (PEEK) has become a material of significant interest in the field of dentistry, and understanding the processing techniques is crucial for harnessing its potential in dental applications. Two predominant processing techniques for PEEK include injection molding and additive manufacturing.
2.20.1. Injection Molding
Injection molding is a widely used manufacturing process for producing high volumes of complex components with precision. In the case of PEEK, the process involves melting the polymer granules and injecting the molten material into a mold cavity under high pressure. This results in the formation of the desired shape upon cooling and solidification.
Advantages of Injection Molding
- Mass Production: Injection molding is highly efficient for mass production, making it suitable for the fabrication of dental prosthetic components in large quantities (Saha et al., 2022).
- Complex Geometry: The technique allows for the production of intricate and complex shapes, essential for dental applications where precise fitting is crucial.
- Surface Finish: Injection molding produces components with a smooth surface finish, enhancing the aesthetics and comfort of dental prostheses.
Considerations:
High Initial Tooling Costs: The creation of molds for injection molding can be expensive initially. However, for large-scale production, the cost per unit decreases significantly.
2.20.2. Additive Manufacturing:
Additive manufacturing, often referred to as 3D printing, is an innovative and increasingly popular method for fabricating PEEK components. This technique builds the desired object layer by layer, directly from a digital model, offering design flexibility and customization.
Advantages of Additive Manufacturing:
- Design Freedom: Additive manufacturing allows for the production of highly customized and patient-specific dental components, catering to individual anatomical variations.
- Reduced Material Waste: Unlike traditional subtractive methods, 3D printing generates less material waste, making it a more sustainable option.
- Rapid Prototyping: Additive manufacturing enables rapid prototyping, allowing for quick iterations and adjustments in the design phase.
Considerations:
- Surface Finish: Depending on the specific 3D printing technology used, the surface finish of PEEK components may vary. Post-processing steps may be required to achieve the desired smoothness.
- Layer Adhesion: Ensuring strong layer adhesion is crucial for achieving the desired mechanical properties. Optimization of printing parameters is essential.
Injection molding and also additive manufacturing have some unique benefits and also limitations in the manufacture of PEEK components used as dental prostheses (Saha et al., 2022). This decision is based on the criteria like production volume, design intricacy and also customization required. As technology continues to develop, analyzing the convergence between these processing methods will allow for harnessing all the benefits PEEK could offer in restorative dentistry.
2.21 Reinforcement materials
Polyether Ether Ketone (PEEK) has garnered attention in dentistry due to its exceptional properties, and the choice of reinforcement materials further refines its mechanical characteristics. Carbon fibers and glass fibers, as common additives, play a pivotal role in augmenting PEEK’s mechanical performance, contributing to its suitability for dental applications.
2.21.1. Carbon Fibers:
Carbon fibers obtained from the carbonized precursors have been widely investigated as a source of influence on the PEEK. Saha et al. (2022) investigate the tensile strength and also modulus of PEEK enhanced with carbon fibers in their study. The research confirmed that both attributes increased substantially, attributing to the capability of CFR-PEEK in many use cases where optimal mechanical properties are necessary. The benefits of carbon fiber reinforcement are that it has a very high tensile strength and also stiffness. PEEK’s ability not to break under the axial forces is due to its carbon fibres (Moharil et al., 2023). This is especially important in the dental prosthetics, where structural stability is very essential. Nevertheless, it is crucial to evaluate the cost issues given that carbon fibers may be rather very expensive. The improved mechanical properties that CFR-PEEK provides may warrant the cost in some cases.
2.21.2. Glass Fibers:
However, the other typical reinforcement selection for PEEK is the glass fibers like E-glass or S-glass. Zhang et al. (2018) went further to investigate the flexural properties of GFR-PEEK in dental uses. Zhang et al. (2018) went further to investigate the flexural properties of GFR-PEEK in dental uses. It was emphasized by the research that the glass fibers increased the flexural strength and modulus which in turn made the material tough against bending forces. Some of the benefits that glass fiber reinforcement offers include the increased flexural strength and also improved dimensional stability. In terms of dental prostheses, where resistance to bending forces during the mastication stage is very essential, glass fibers are found to have many positive impacts. But it is very important to consider the potential fragility of the glass fibres. Both the carbon fibers and glass fibres act as reinforcement agents to PEEK in dental application, wherein getting an optimal balance between strength and toughness is very essential. These compounds contribute a lot to the mechanical properties of this material, thus expanding its application in the restorative dentistry. Despite the ongoing research, very little is known in terms of the best formulation for such composite materials.
2.22 Aging and degradation effects
Understanding the aging and degradation effects of Polyether Ether Ketone (PEEK) is essential for assessing its long-term performance in dental applications. Several factors, including temperature and moisture exposure, as well as chemical degradation, contribute to the aging process of PEEK (Moharil et al., 2023).
2.22.1. Temperature and Moisture Exposure
PEEK is known for its thermal stability at the high temperatures, making it suitable for diverse temperature applications. On the other hand, many years of high temperatures and humidity is able to change its mechanical properties. Sade, (2019) investigated how thermomechanical and the static loadings changed in the fracture strength of PEEK in a research study. The study focused on the need to assess temperature variations, largely in the case of oral milieu where these fluctuations can take place during a meal with hot or cold food. Moisture is a kind of potential exposure which might affect the PEEK either from the environmental conditions or under oral circumstances. Because PEEK is naturally resistant to the moisture absorption, but extended exposure may result in changes to the mechanical properties. Water absorption can be minimized by utilizing the adequate sealing and finishing methods when fabricating PEEK dental prostheses.
2.22.2. Chemical Degradation
PEEK has a good chemical resistance as one of its important properties. It is naturally resistant to various chemicals, acids and also bases. But some chemical exposures could definitely influence the substance even over a long period of time. Chemical degradation, especially in the oral cavity owing to the exposure of saliva and also different materials. The impact of storage media on the physicomechanical properties PEEK has been studied in many studies about the chemical stability of PEEK, for instance Rosentiel et al. (2022). The results point to the importance of interpreting PEEK as a long-term solution in dental prostheses based on chemical interactions and degradation.
2.22.3. Aging and Long-Term Stability
First, although the PEEK has outstanding mechanical characteristics, it is very significant to investigate its aging behavior and long term stability. The aging processes may consist of many modifications in the molecular structure, crystallinity and total material characteristics. The long-term behavior of PEEK in the dental applications, especially for use as frameworks in fixed dental prostheses and require a research to ensure its reliability over the same. It is necessary for the PEEK aging and degradation consequences expectations to understand the dynamics of temperature, moisture, and also chemical exposure. Optimal material selection, manufacturing approach and the surface treatment can all add to improving the resistance of this material to these challenges (Rodríguez et al., 2021). Continuous research in this field seeks to offer a broad information on the functionality of PEEK when subjected to different environmental factors that would guide clinicians and prosthodontists to place competent decisions concerning its application as a dental restoration.
Chapter 3.0 Methodology
This study is derived from its methodology which focuses on the general mechanical properties of the Polyether Ether Ketone (PEEK), Poly-Ether-Ketone (PEKKTON) and also a generally used 4 – unit Zirconia framework for posterior Fixed Dental Prostheses (FDPs). This study methodology covers the material selection, sample preparation, strength testing of fractures, comparative analysis and impact of span length determination on statistical analysis as well measures to verify validation reliability. Experimental COCR die model fabrication will be performed, which includes die design then Die milling (metal) after that digital framework design and finally Milling and printing for the frameworks designs (Padros et al., 2020). In previous studies 10 -15 specimens will be tested per group so my Adopted Policy will be 10 samples per group and the total is 80 specimens. Sample size calculation was done using G*Power software. For fracture load testing, the stress will be directed exactly at a 90ᵒ angle to the PEEK surface using universal testing machine until fracture. Then the fracture strength will be calculated.
3.1 Material Selection:
The basis is a very accurate choice of the analyzed materials. As for the PEEK and PEKKTON, they are chosen because of their high-performance polymer structure while Zirconia is a traditional ceramic material that has long been used in prosthodontics (Al Mortadi, 2022). This selection covers a wide range of material choices that are used in the production of dental prostheses, which is an very important base for the analysis (Chen et al., 2009).
3.2 Specimen Preparation:
With the standardization of the specimens for preparation, consistency and reliability are guaranteed in testing. The specimens depict a four-unit posterior FDP setup which is meant to replicate the true life experience. The fabrication process adheres to the established protocols in order to obtain a uniform and also representative specimen. A significant component of the experimental design is the production of a COCR die model. This process entails a sequence of precise steps: First, designing the die and then milling it from the metal. The next step involves developing a digital framework design, which is critical to the accuracy of specimens (Padrós et al., 2020). The final step in this process is the milling and the subsequent printing of framework design specimens that mirror real-life dental settings with extreme accuracy (Chen et al., 2009). When the specimens are being prepared, a uniform technique is always used. The samples are designed to mimic a posterior FDP, four-unit framework representing the clinical practice with such abutments. In all, 80 specimens are prepared and divided into groups of ten samples per each sample group. This construction is driven by a policy from the previous research in which 10 to 15 specimens were subjected per group. Following statistical validity and relevance, the size of the sample is calculated in the G*Power software.
3.3 Fracture Strength Testing:
For each material, the tensile testing method is used as the major procedure for calculating the fracture strength. These frameworks are then subjected to the axial forces through a universal testing machine until they fail using the process of Universal Testing Machine (Aligholi et al., 2022). The testing variables like force, displacement and finite strain are too closely controlled so as to achieve a thorough analysis. The core of the study is to test the fracture strength via tensile testing. The stress is applied with a 90-degree angle precisely on the PEEK surface, which results in fracture using a universal testing machine. This approach enables the accurate measurement of fracture strength, and the effect is closely monitored using load, deformation rate values comparison for a better analysis (Rodríguez et al., 2021).
3.4 Comparative Analysis:
The focus is made on the comparative analysis of the fracture strength for PEEK, PEKKTON and Zirconia. Statistical tools, such as the ANOVA and post-hoc tests are commonly used to discriminate between various materials with respect to their mechanical viability (Greuling et al., 2023). This comparative analysis is very vital to understand the behavior of each material under stress.
3.5 Impact of Span Length:
For evaluating the impact of span length on the fracture load, specimens having various spans are tested. This aspect of the analysis investigates whether longer periods indeed impact the fracture strength in any way at all. It aims to provide important information on enhancing the design of the posterior FDPs. This work is very essential in interpreting how the design characteristics influence the strength of posterior FDPs.
3.6 Statistical Analysis:
Statistical procedures such as ANOVA, correlation analyses and regression models are often used to get numeric values for the relations between span lengths on the fracture strength. These analyses provide a lot of detail on the aspects that influence the fracture load, and also any trends in the data (Greuling et al., 2023).
3.7 Validation and Reliability:
The methodology is supplemented with validity and reliability measures, namely the equipment calibration as well as randomized specimens and standard testing procedures. These steps are extremely important in enhancing the reliability and also generalizability of the results. Last of all, this method provides a systematic and rigorous approach to the mechanical behavior investigation of PEEKs, PEKKTON & also Zirconia prostheses fabricated as posterior FDPs. This combination of standardized tests, comparative studies and static methods is very precisely meant to provide significant insights into the restorative dentistry especially related to mechanical behavior on dental prostheses materials such as PEEK PEKKTON Zirconia, and COCR die models.
Chapter 4.0 Conclusion
In conclusion, the thorough analysis of the mechanical characteristics for 4-unit posterior Fixed Dental Prostheses (FDPs) made out of Polyether Ether Ketone (PEEK), offers critical information regarding this material’s applicability in dentistry. The research covered multiple facets such as tensile strength, modulus, fracture strength and flexural properties along with relatively to aging effects. The tensile strength of PEEK is quite very impressive, about 100 MPa presenting it in a positive light for the dental applications. In addition, reinforcement materials including carbon fibers and also glass fibers have also been investigated in order to increase the tensile strength and modulus which demonstrate the mechanical toughness of that particular material. A notable feature of the study is, however, to look at a comparison between PEEK fracture strength and that using the commonly used 4-unit zirconia framework. The purpose of the study is to provide a comparative analysis in terms of fracture strength, thus illuminating how PEEK performs compared with the other materials used for posterior FDPs. A preliminary analysis suggests that the PEEK, with superior mechanical characteristics appears to be a potentially very good substitute for the standard frameworks. Flexural strength and modulus are very indispensable characteristics of these materials especially in the regions where deflection loads prevail like mandibular prosthesis. PEEK flexural behavior studies for the unreinforced and reinforced establish its ability to resist the bending forces during chewing. Strengthening the validity of PEEK’s long-term stability, the aging and degradation effects are also mentioned along with temperature sensitivity, moisture exposure and chemical changes. Sealing and finishing, as well as the continued research into chemical resistance plays an important role in addressing the issues caused by aging. This research provides a basis for the further development of PEEK as a dental framework material. With further development of the restorative dentistry, the demand for biocompatible materials with the optimal mechanical properties and reliable long-term stability is heightening. Given its exceptional characteristics of mechanical strength, biocompatibility and also chemical degradation resistance PEEK can be considered an exciting option for the posterior FDPs. The results highlight the promising role of PEEK in restorative dentistry, both its strength and also how some concerns regarding performance are addressed in such hard conditions. However, additional studies and clinical tests are needed to prove the validity of these findings enabling prostate dentists and practitioner professionals with relevant knowledge about how to apply PEEK in the manufacturing posterior FDPs.
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