Dr. Arpit Sikri, Dr. Jyotsana Sikri
(Part 1 – Stay tuned for Part 2 – Applications of PEEK in real life case scenarios)
Polyetheretherketone (PEEK) is a vital dental material belonging to the family of polyaryletherketones (PAEKs). It is commonly categorized as “high-performance polymer”. The exceptional properties of PEEK has made this material “a wonder material” to be used for various applications not only in medicine but also in dentistry . In medicine, PEEK has been widely used in cardiology, orthopaedics and surgical procedures pertaining to maxillo-facial & spinal regions. In dentistry, PEEK has been used as the material of choice in field of restorative dentistry, orthodontics as well as implantology. This article reviews about PEEK as a material along with its multi-varied applications and various future perspectives in dentistry.
KEY WORDS: PEEK, polymer, PAEK, dental material, HPP, biomaterial, dental applications, thermoplastic polymer
Polyether-ether-ketone (PEEK) is a specialized novel type of plastic, which is thermoplastic engineered. It has a wide variety of properties namely excellent mechanical, chemical and biological . The fundamental properties and advantages of PEEK polymer [7-10] include:
- Thermal properties i.e. higher thermal stability. The melting point (Tm) of PEEK is around 334–343°C with a glass transition temperature (Tg) of 143°C;
- PEEK is known to have superb toughness and rigidity;
- As far as creep is concerned, PEEK exhibits the best creep resistance out of all biomaterials;
- A plethora of processing methods can be used for PEEK i.e. injection molding, additive manufacturing, subtractive manufacturing, compression molding, extrusion molding etc;
- PEEK has amazing wear resistance properties. The incorporation of carbon fibres (CF), graphite and polytetrafluoroethylene (PTFE) furthermore improves the abrasion resistance of the same;
- In addition to the abrasion resistance, the other important mechanical properties make use of inclusion of the carbon fibre (CF), glass fiber (GF) and barium sulfate (BaSO4), to meet various requirements;
- Cytotoxicity – PEEK is particularly known for its biocompatibility and least cytotoxicity;
- Stress shielding effect – PEEK is known to have elastic modulus closer to that of the human bone. This helps in prevention of stress shielding.
- Sterilization compatibility – PEEK has been quite sterilization friendly. Even at higher temperatures kept for sterilization, it has unaltered properties.
Synthesis & Structure
PEEK is generally synthesized with the help of step-growth polymerization  and is denoted as follows (Figure 1):
PEEK is known to exhibit excellent physical, mechanical, chemical and biological properties. The physical properties of PEEK  are depicted in Figure 2.
The mechanical properties of PEEK  are depicted in Figure 3.
The chemical properties of PEEK  are depicted in Figure 4.
The biological properties of PEEK  are depicted in Figure 5.
PEEK enjoys a plethora of applications in restorative dentistry due to its superior physical, chemical, mechanical and biological properties  (Figure 6)
PEEK has been actively used in restorative field, fixed prosthodontics, framework for cast partial dentures & implant-supported fixed prosthesis, and majorly as dental implant biomaterial. In addition to this, the incorporation of various fibres and surface modifications with coatings has further broadened the horizon of its use.
The PEEK materials are a boon to the dental field. This can be related to its phenomenal properties i.e. mechanical, chemical properties and biological. Based on these properties, PEEK has been known for the wide variety of applications in both medicine and dentistry. Inspite of the extensive review of literature on PEEK as a biomaterial, long term evaluations are still needed to prove the efficacy of PEEK as a biomaterial in dentistry. At the end, it can be rightly said “PEEK is a prodigious material in dentistry”.
1. Asgharzadeh Shirazi, H., Ayatollahi, M.R., Asnafi, A., 2017. To reduce the maximum stress and the stress shielding effect around a dental implant-bone interface using radial functionally graded biomaterials. Comput. Methods Biomech. Biomed. Eng. 20, 750–759.
2. Basgul, C., Yu, T., MacDonald, D.W., Siskey, R., Marcolongo, M., Kurtz, S.M., 2018. Structure–property relationships for 3d-printed peek intervertebral lumbar cages produced using fused filament fabrication. J. Mater. Res. 33, 2040–2051.
3. Chung, D.D.L., 2017. Processing-structure-property relationships of continuous carbon fiber polymer-matrix composites. Mater. Sci. Eng. R-Reports 113, 1–29.
4. Deng, Y., Zhou, P., Liu, X., Wang, L., Xiong, X., Tang, Z., Wei, J., Wei, S., 2015. Preparation, characterization, cellular response and in vivo osseointegration of polyetheretherketone/nano-hydroxyapatite/carbon fiber ternary biocomposite. Colloids Surf B Biointerfaces 136, 64–73.
5. Keul, C.; Liebermann, A.; Schmidlin, P.R.; Roos, M.; Sener, B.; Stawarczyk, B. Influence of PEEK surface modification on surface properties and bond strength to veneering resin composites. J. Adhes. Dent. 2014, 16, 383–392.
6. Stawarczyk, B.; Keul, C.; Beuer, F.; Roos, M.; Schmidlin, P.R. Tensile bond strength of veneering resins to PEEK: Impact of different adhesives. Dent. Mater. J. 2013, 32, 441–448.
7. Panayotov, I.V.; Orti, V.; Cuisinier, F.; Yachouh, J. Polyetheretherketone (PEEK) for medical applications. J. Mater. Sci. Mater. Med. 2016, 27, 118.
8. Cook SD, Rust-Dawicki A. Preliminary evaluation of titanium-coated PEEK dental implants. J Oral Implantol 1994;21:176–81.
9. Tetelman ED, Babbush CA. A new transitional abutment for immediate aesthetics and function. Implant Dent 2008;17:51–8.
10. Dawson JH, Hyde B, Hurst M, Harris BT, Lin W. Polyetherketoneketone (PEKK), a framework material for complete fixed and removable dental prostheses: a clinical report. J Prosthet Dent 2018;119:867–72.
11. Oh KC, Park J, Lee J, Moon HS. Treatment of a mandibular discontinuity defect by using a fibula free flap and an implant-supported fixed complete denture fabricated with a PEKK framework: a clinical report. J Prosthet Dent 2018;119:1021–4.
12. Srinivasan M, Kalberer N, Maniewicz S, Muller F. Implant-retained overdentures using an attachment with true-alignment correction: a case series. Int J Prosthodont 2019;32:482–96.
13. Amelya A, Kim J, Woo C, Otgonbold J, Lee K, Kim J, et al. Load-bearing capacity of posterior CAD/CAM implant-supported fixed partial dentures fabricated with different esthetic materials. Int J Prosthodont 2019;32:201–4.
14. Passia N, Ghazal M, Kern M. Long-term retention behaviour of resin matrix attachment systems for overdentures. J Mech Behav Biomed Mater 2016;57:88–94.
15. Bozini T, Petridis H, Garefis K, Garefis P. A meta-analysis of prosthodontic complication rates of implant-supported fixed dental prostheses in edentulous patients after an observation period of at least 5 years. Int J Oral Maxillofacial Implants 2011;26:304–18.
16. Purcell BA, McGlumphy EA, Holloway JA, Beck FM. Prosthetic complications in mandibular metal-resin implant-fixed complete dental prostheses: a 5 to 9 year analysis. Int J Oral Maxillofac Implants 2008;23:847–57.