Polyether ether ketones (PEEK): Properties and applications as implants for alternative dentistry materials: A narrative review

Imam S Azhar; Rania G Syaharani; Vanya S Smeer; Multazan Multazan

doi:10.4103/jioh.jioh_10_22

REVIEW ARTICLE

Year : 2023 | Volume : 15 | Issue : 1 | Page : 28-33

Polyether ether ketones (PEEK): Properties and applications as implants for alternative dentistry materials: A narrative review

Imam S Azhar¹, Rania G Syaharani², Vanya S Smeer², Multazan Multazan²
¹ Department of Prosthodontics, Universitas Airlangga, Surabaya, Indonesia
² Faculty of Dental Medicine, Universitas Airlangga, Surabaya, Indonesia

Date of Submission	09-Jan-2022
Date of Decision	11-Oct-2022
Date of Acceptance	11-Oct-2022
Date of Web Publication	28-Feb-2023

Correspondence Address:
Mr. Imam S Azhar
Jl. Major General Prof. Dr. Moestopo No. 47, Surabaya 60132, East Java
Indonesia

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jioh.jioh_10_22

Abstract

Aim: Titanium has been a popular material for dental implants. However, there are several drawbacks to these materials, including the occurrence of allergies, bone resorption, surface damage, contamination linked to peri-implantitis, high modulus of elasticity, and less aesthetically pleasing hue. As a result, polyether ether ketone (PEEK) can be utilized as a substitute material in dentistry. The purpose of this review of the literature is to identify the attributes and uses of PEEK in dentistry, particularly for implant applications. Materials and Methods: The articles were independently evaluated during the screening procedures in accordance with the eligibility requirements. The criteria also include studies that are written in English and published on PubMed, ScienceDirect, ResearchGate, and Web of Science, as well as narrative reviews, research articles, and other studies. Articles published before 2014, case reports, case series, book chapters, and articles not related to PEEK in dentistry were excluded in the criteria. Strategy to find articles using PICO includes patients in needs of dental implants, PEEK, titanium, and PEEK as an alternative material for dental implant. The risk of bias was assessed using Cochrane Risk of Bias Tool 2 (RoB 2). Results: A total of 26 articles were identified, of which 16 were of particular relevance to the use of PEEK in dental applications, especially implants. Conclusion: Due to its low elastic modulus, good mechanical structures, and bone-contact biocompatibility when used as a bulk implant, PEEK can be a substitute material in oral implantology. It is possible to improve PEEK’s bone-contact biocompatibility and lessen its downsides by altering the material’s surface and mixing.

Keywords: Health Outcome, Implant, PEEK, Polyether ether ketone, Titanium

How to cite this article:
Azhar IS, Syaharani RG, Smeer VS, Multazan M. Polyether ether ketones (PEEK): Properties and applications as implants for alternative dentistry materials: A narrative review. J Int Oral Health 2023;15:28-33

How to cite this URL:
Azhar IS, Syaharani RG, Smeer VS, Multazan M. Polyether ether ketones (PEEK): Properties and applications as implants for alternative dentistry materials: A narrative review. J Int Oral Health [serial online] 2023 [cited 2023 Sep 22];15:28-33. Available from: https://www.jioh.org/text.asp?2023/15/1/28/370739

Introduction

Since its introduction by Brånemark, titanium and its alloys are still one of the materials of choice for dental implants, abutments, and partial denture frameworks.^[1] It is because titanium has good mechanical properties, low density, and good bone-contact biocompatibility.^[2] However, it has some drawbacks. For instance, although titanium is resistant to corrosion, it can cause bone resorption, implant fracture, and stress shielding. This happens because titanium has high elastic modulus (110 GPa), which is very different from cortical bone (14 GPa). Other than that, titanium could also cause allergies, peri-implantitis, and it has problems with its metallic appearance. The movement of titanium particles in tissues around dental and muscle inserts, as well as in local lymph nodes and pneumonic tissue, has been shown. After titanium implant placement, allergic reactions that may happen are orofacial swelling, erythema, and eczema.^[3]

Non-metallic dental materials are increasingly important due to various factors, one of them is the increasing patient aesthetic demands.^[4] Therefore, polyether ether ketone (PEEK) can be the alternative material used in dentistry. PEEK is a semi-crystalline linear polycyclic aromatic polymer. With various advantages, PEEK can be used as a material for implants, abutments, crowns, and denture frameworks. Some advantages of PEEK include being able to assist bone remodeling, resistance to chewing force, and higher bone-contact biocompatibility.^[5] The role of PEEK as an implant in dentistry has been depicted in a small number of papers. This narrative review elucidates the importance of PEEK in such a capacity.

Materials and Methods

Search strategy

A narrative literature review was conducted to study that dental implants may be made with PEEK as an alternate material. The articles ranged from 2014 to 2022 were searched in various search engines such as PubMed, ScienceDirect, ResearchGate, and Web of Science databases. Search terms used to find the articles are “polyether ether ketone,” “PEEK in dentistry,” “PEEK as dental implant,” and “PEEK modification.” This study is to find similar topics from several articles that will be reviewed and summarized. PICO was used as a strategy to find the articles:

A. Problem: Patients in needs of dental implants

B. Intervention: Polyether ether ketones

C. Comparison: Titanium

D. Outcome: PEEK as an alternative material for dental implants

Inclusion criteria

The inclusion criteria include the following: studies written in English; studies published in PubMed, ScienceDirect, ResearchGate, and Web of Science; narrative reviews, research articles, and other studies.

Exclusion criteria

The exclusion criteria are case reports/series, book chapters, articles published prior to year 2014, and articles that are not relevant to PEEK in dentistry.

Study selection

Eligibility criteria, databases, and search strategies were used to identify relevant studies. Reviewers independently evaluated the study titles and abstracts during the screening procedures, reading, analyzing, and selecting abstracts in accordance with the eligibility requirements. A total of 88 papers were retrieved during the selection process, which was reduced to 45 as 43 papers did not meet the inclusion criteria. After screening the full-text articles, 19 were excluded, 11 were found to be out of scope, and 8 were found to have insufficient details. A total of 26 articles were generated. This narrative review included these articles; crucial findings and judgments were taken out to construct the topics developed in this study [Figure 1].

Figure 1: PRISMA flow diagram of articles screening and selection

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Risk of bias

The risk of bias was evaluated utilizing Cochrane Risk of Bias Tool 2 (RoB 2). There are five domains rated by the authors, which are bias arising from the randomization process, bias due to deviations from intended intervention, bias due to missing outcome data, bias in measurement of the outcomes, and bias in selection of the reported result.^[6] The overall result showed low risk of bias and was presented in [Figure 2].

Figure 2: Risk of Bias

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Results

A total of 26 articles were identified, of which 16 were of particular relevance to the use of PEEK in dental applications, especially implants [Table 1].

Table 1: The review of articles

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Discussion

Dental implants

Dental implants are prosthetics that reconstruct missing teeth in jaws with partial dentition.^[8] Edentulous, dissatisfied with their current unstable and non-retentive full dental prosthesis, and keeping it in good condition are some indications for patients to use dental implants. This approach is considered effective because there is a biological and biophysical process called osseointegration, which is the primary goal of implants. According to Brånemark, osseointegration is the process by which an implant adheres directly and rigidly to the bone without the need for any connecting tissue. Clinically, osseointegration is a procedure for securing the implant in occlusal-susceptible bone. Several factors affecting osseointegration are bone quality and quantity, shape of the implant, implant surface, and surgical techniques.

Dental implant components consist of three: fixture, abutment, and superstructure. Fixture, or also called implant body, is the part that is surgically placed into the bone at the first stage of surgery. Abutment is a part of dental implant that supports a prosthesis or implant superstructure. Abutments have three main categories: (1) retaining the screw, (2) retaining cement, and (3) attachment abutments (prefabricated). A superstructure is a scaffolding that connects either the implant or the bone. Its function is to provide retention for a removable or a fixed prosthetic framework.^[27] There are some factors that determine dental implants have a high survival rate: (1) age, (2) implant’s length, (3) the implant diameter, (4) the quality of the bones, and (5) the region of implant.^[9] There are three kinds of dental implants: (1) endosteal, (2) subperiosteal, and (3) transosteal.^[10]

Polyether ether ketone

A semi-crystalline linear polycyclic aromatic polymer is identified as PEEK. It was developed in 1978 and later it was commercialized for industrial applications. PEEK had proven itself as a strong high-performance thermoplastic rival for replacing metal implant components by the late 1990s.^[11] This material is commonly used in medicine, especially in orthopedic and traumatic applications.^[12] In recent years, PEEK has been employed in cranioplasty, interbody fusion cages, total joint arthroplasty, and soft-tissue healing.^[13]

PEEK was certified as an implantable-grade material by the U.S. Food and Drug Administration.^[12] Hence, in the future of dentistry, PEEK could be used for oral implantology and prosthodontics, implantable devices, crowns, and also in fixed and removable partial dentures. High mechanical properties, exceptional wear and heat resistance, and remarkable chemical resistance are a few of its remarkable characteristics. In addition, PEEK is highly durable, has a high melting point, and is resistant to chemical and biological action.^[14]

PEEK properties as dental implants

Dental implants are a substitute for missing teeth. Titanium has been the dental implant material of choice since its introduction by Brånemark. However, apart from these, materials have a number of advantages, but they also have significant drawbacks though they occur very rarely, such as bone resorption and consequent implant loss, radiation-induced disintegration, responses of hypersensitivity, allergy symptoms, and outside damage associated with peri-implantitis.^[7] The disadvantages of titanium implants are expected to be mitigated by the use of non-metallic materials such as PEEK.

PEEK is a white, radiolucent, solid material with exceptional thermal stability and a melting point of above 280°C, resulting in low PEEK deformation. PEEK also has a low elastic modulus (3–4 GPa) which is lower than titanium but this material can be combined with others so that the elastic modulus can increase up to 18 GPa. Due to its elastic modulus similar to that of cortical bone, PEEK is an appropriate material for implants.^[15] Therefore, the stresses that arise on the bone can be decreased through force absorption. Owing to the ability to absorb shock, PEEK is claimed to be able to protect bone.^[5]

PEEK has no toxic or mutagenic properties and is hence safe for use by patients.^[1] Due to its radiolucent nature, PEEK will reduce the appearance of artifacts on magnetic resonance imaging (MRI). PEEK is very rigid with a flexural strength of 140–170 MPa and also light because of its low density so that the patient who wears it will feel comfortable. The other benefit is that PEEK does not cause tooth attrition and also could promote bone remodeling.^[4]

A study by Wang et al.^[16] compares PEEK and titanium framework. The survival rate at 5-year follow-up is almost the same. However, mechanical and biological complications of PEEK are lower than those of titanium. Mechanical complications include loose screw, fractures, and microcracks. The biological side effects include temporomandibular joint dysfunction, soft tissue irritation, and bleeding upon probing. Also, it was found that vertical bone loss and deeper peri-implant pocket are higher in the titanium group.^[16] Based on these good traits, PEEK is expected to become the alternative to titanium for the formation of abutment.^[1] However, PEEK also has several disadvantages such as lack of osseointegration and low wettability, and this material is difficult to produce.^[17] However, there are ways to modify this material so that the bone-contact biocompatibility could increase and the drawbacks could be reduced.

PEEK modification

Although PEEK is a bioinert material, survivability of unmodified PEEK for implant is still questionable because there is no evidence of osteoconductive effects.^[18] This could lead to severe implantitis and failure of the implant. Modification of the PEEK’s surface and mixing are methods to increase its bioactivity. Surface modification is divided into physical, chemical, and composite modification. Meanwhile, blending modification is using hydroxyapatite (HA), carbon fiber (CF), and zinc oxide (ZnO) to be mixed with PEEK.^[19]

Physical modification

The most widely used method of physical modification is plasma treatment. This method uses nitrogen, ammonia, oxygen, argon, hydrogen, or other gas plasma to improve PEEK’s surface morphology and hence bone-contact biocompatibility. Studies by Novotna et al. and Waser-Althaus et al. attempted to modify PEEK with argon and oxygen-ammonia plasma, respectively. Both managed to increase osteogenic differentiation, adhesion, and proliferation and also have improved bone binding around the dental implant.^[19]

Chemical modification

Chemical modifications can be carried out using UV irradiation or sulfonation. Zheng et al.^[20] tested a phosphate group added onto PEEK’s surface using UV grafting. The result showed that osteogenic and adhesion characteristics are enhanced, which indicates its potential application in dental implants. Furthermore, an in-vivo study resulted in bone-implant contact improvement and bone tissue compatibility. A study by Wang et al.^[21] developed sulfonation-modified PEEK. This sulfonation is using ambient temperature, 22°C. The results are porosity and roughness, and surface nanotopography is increasing. These are the most important things that affect osteoconduction.

Composite modification

Composite modification works by modifying composite-coated PEEK by chemical or physical method. A study by Wiacek et al. tried plasma modifying chitosan-coated PEEK. Chitosan has hemostatic and antibacterial properties, also enhancing the polymer biocompatibility for specific applications. PEEK’s surface roughness is increasing due to low temperature plasma modification, and therefore the adhesive characteristic is also improving. This causes chitosan to have stronger adhesion to the surface. Hydrophilicity is also enhanced which can increase the rate of osseointegration. It shows that this method is suitable, enhancing PEEK’s bioactivity.^[22]

Blending modification

One of the blending modifications is the use of nanoparticles such as hydroxyapatite (HA) crystals. HA-modified PEEK has antibacterial properties that can fight Streptococcus mutans. Therefore, it prevents gingival and periodontal diseases.^[23] A study by Ma and Guo showed that PEEK powders that were incorporated with HA are more hydrophilic than pure PEEK. This characteristic will help to speed up the healing process of implants.^[24] Also, in the study by Ma et al., HA-PEEK has better growth of bone cells and tissues.^[25]

HA is being developed alongside carbon fiber- and glass fiber-reinforced PEEK (CFR- and GFR-PEEK), respectively. CFR-PEEK can show elastic modulus values of up to 18 GPa, whereas GFR-PEEK has slightly lower values, at around 12 GPa. This elastic modulus can still be increased to be more like titanium by using CFR composites that vary in length and orientation. CFR-PEEK as an implant material has some useful properties, including bone-contact biocompatibility, appropriate mechanical properties, and suitability for use with contemporary imaging technologies.^[26]

Clinical recommendations

Most studies have been conducted in vitro, and more clinical research is required to establish just how acceptable PEEK and its derivatives are for use as dental implants.

Conclusion

PEEK can be an alternative material in dentistry for dental implantology. Some previously published literatures showed that PEEK has low elastic modulus, good mechanical structures, and bone-contact biocompatibility when used as a bulk implant. Surface and blending modifications can be applied to increase PEEK bone-contact biocompatibility and reduce its drawbacks. It is intended that more research will be conducted to determine the efficacy of using PEEK in dental implants, so that in the future, health professionals will be able to utilize PEEK in dental implants on a regular basis.

Acknowledgement

There is no acknowledgement to declare.

Financial support and sponsorship

Nil.

Conflicts of interest

The authors report no conflicts of interest in this work.

Authors’ contribution

Concept and design: ISA, RGS, VSS, MM; definition of intellectual content: ISA, VSS, MM; literature search, data acquisition, and data analysis: RGS, VSS, MM; manuscript preparation: ISA, RGS, VSS, MM; manuscript editing: RGS and MM; manuscript review: ISA and MDA; guarantor: ISA.

Ethical policy and Institutional Review Board statement

There is no ethical Policy and Institutional Review Board Statement.

Patient declaration of consent

Not applicable.

Data availability statement

Not applicable.

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