Journal of Advanced Clinical and Research Insights

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Polyetheretherketone in prosthodontics - A review
  JCRI
REVIEW ARTICLE
Polyetheretherketone in prosthodontics - A review
Sushant A. Pai, Shubhangi Kumari, B. Umamaheswari, Mangala Jyothi, C. B. Shanthana Lakshmi
Department of Prosthodontics Including Crown and Bridge, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Bengaluru, Karnataka, India
Correspondence: Dr. Shubhangi Kumari, Department of Prosthodontics Including Crown and Bridge, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Bengaluru, Karnataka, India.
E-mail: shubhangikumari27@gmail.com
Received: 20 January 2019;
Accepted: 22 February 2019
doi: 10.15713/ins.jcri.252
 
ABSTRACT
Materials used in different fields of prosthodontics have evolved over the years. In recent years, patient more preferably demands a metal-free, lightweight, tooth-colored prosthesis. Polyetheretherketone (PEEK) can be used in various ways in prosthodontics. The aim of this article is to encapsulate the precedence of PEEK, compared to other restorative materials that have been used currently, based on various studies conducted on this material.
Keywords: Fixed partial dentures, implant, polyetheretherketone, polymer, prosthodontics, removable prostheses
How to cite this article: Pai SA, Kumari S, Umamaheswari B,Jyothi M, Lakshmi CBS. Polyetheretherketone in prosthodontics- A review. J Adv Clin Res Insights 2019;6: 24-26.
 
 

Introduction

Polyetheretherketone (PEEK) is a man-made, white-colored polymer. This has been used in various medical fields such as orthopedic, trauma, and spine implants as an active biomaterial for many years.[1,2] PEEK is a semi-crystalline material. It consists of two phases, namely amorphous and crystalline.[2] Injection molded PEEK in implants typically contains 30-50% of crystal. However, it may differ (0-40%) depending on its manufacturing process.[2] It is produced by the reaction between 4,4'-diflurobenzophenone and the disodium salt of hydroquinone in the presence of solvent like diphenyl sulfone at 300°C.[3] Since April 1998, PEEK has been used as implant material. Having an elastic modulus, similar to human cortical bone (3-4 GPa) makes it an excellent alternative of titanium (Ti) and other conventionally used metal in orthopedics and traumatology field. Table 1 shows the mechanical properties of PEEK.

PEEK can be modified by various surface treatments such as carbon reinforced and glass fiber reinforced. Carbon-reinforced PEEK has anelastic modulus up to 18 GPa comparable to dentine.[4,5]Thermal properties of PEEK are well suitable to be used in the oral environment. PEEK is a bioinert material. After the completion of polymerization reaction, it becomes extremely unreactive to any chemical, thermal, and post-irradiation changes.[2] Chemical solvents (except concentrated H2SO4) do not have any degrading effect on this polymer.[6] Considering the mechanical properties of PEEK, it can be used as a dental implant, in fixed partial dentures (FPD) and removable prostheses.

 
PEEK as an implant material

For spinal implants, PEEK has been used since 1996. Numerous studiesalso have been conducted to check the reliability of PEEK as a spinal implant material. However, for dental application, much more researches still required. Stress shielding is an important property for any implant material. It is a phenomenon of a decrease in bone density as a result of the removal of typical stress from the bone by an implant. To being an ideal implant material, stress shielding should be low to prevent further bone loss.

Benefits of PEEK over Ti as an implant material:
  1. PEEK may exhibit less stress shielding than Ti.
  2. It exhibits fewer hypersensitive and allergic reactions in compare to Ti.
  3. It does not have a metallic color as Ti, so esthetically more pleasing.
  4. It can be used as a core material by adding the bulk and modifying the surface properties.
  5. It has better wear and abrasion resistance.
  6. The friction coefficient of PEEK is low.
  7. It has shock absorption effect.

Victrex (now known as Invibio) is a leading manufacturer for medical grade PEEK. In 1999, they launched PEEK-OPTIMA for an implant.

PEEK Reinforcement

The pure PEEK has a very low elastic modulus compared to Ti, ceramics, and bone. To increase its elastic modulus, to make itmore suitable for dentistry, several reinforcements have beendone. Several experiments have been done to obtain PEEKcomposites, after reinforcing PEEK with other materials. Thesecomposites have improved mechanical properties than purePEEK.

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Polyetheretherketone in prosthodontics Pai, et al.

Table 2 shows the elastic modulus of these composites alongwith commercially used dental alloy for an implant.[7]

Surface modification of PEEK for osseointegration

Since PEEK is a bioinert compound, several customizationshave been tried in an attempt to make it more osteoconductive.The surface of the pure PEEK can be modified by variousprocesses such as plasma spraying, spin coating, acid etching,chemical modification, and ultraviolet irradiation. Severalnanoparticles can be coated on the surface of PEEK to makeit more bioactive for integration with bone. The primarilyused particles are titanium oxide, hydroxyfluoroapatite, andhydroxyapatite. The tensile properties of these composites aresuperior to pure PEEK.

Table 3 shows different surface modifications of PEEK.[7]

PEEK in fixed prostheses

PEEK can be used to make the framework of fixed dentureprostheses. It can also be used for the dental crown preparationwith a facial coating of veneering composites. Hence, manyprocedures have been illustrated to facilitate the bonding ofPEEK with resin composite crown. Bonding agent applicationincreases the tensile bond strength to composite resin. Etchingwith various acids such as sulfuric acid and piranha acid alsoincreases the bond strength to the resin.

Table 1: Mechanical properties of PEEK
Polyetheretherketone in prosthodontics � A review
PEEK: Polyetheretherketone

Table 2: Elastic modulus of pure PEEK, PEEK composites, anddifferent dental alloy
Polyetheretherketone in prosthodontics � A review
PEEK: Polyetheretherketone, Ti: Titanium, Cr-Co: Cobalt-chromium

 
Advantages of PEEK as an FPD material:
  1. Highly polished surface.
  2. Less plaque accumulation.
  3. Gum irritation is absent.
  4. Bond strength is sufficient to be veneered with any compositematerial.
  5. High fracture resistance.
  6. No discoloration, due to the absence of exchange of ions inthe mouth.

PEEK as a removable prosthesis material

Conventionally, metals (mainly cobalt-chromium [Cr-Co]) areused as the framework material, for a removable dental prosthesis.These are still in use due to its cheaper price. However, there arecertain drawbacks with these metal prostheses such as estheticalunacceptability by the patient, the heaviness of prosthesis,and metallic taste that lead to the search for newer material toovercome these drawbacks.

Initially, nylon and acetal resin were used as an alternative tothe metal framework. Several studies have been done on that.After these studies, they concluded that nylon is estheticallybetter, but it cannot be relined. Contrarily, acetal resin hasadequate mechanical strength, but it lacks liveliness of thenatural teeth.[8-11]

Panagiotis Zoidis did a clinical study on a 70-year femalepatient having a conventional Cr-Co mandibular distal extensionremovable denture. The patient complained of the metallic taste,the weight, and the unpleasant display of the metal clasps of herexisting Cr-Co prosthesis and demanded an alternative materialfor the fabrication of a new prosthesis. He treated the patient withmodified PEEK material (Bio-HPP) distal extension frameworkwith acrylic teeth and conventional heat cure resin denture base.Zoidis did 1 year of follow-up after completion of treatment. Inhis follow-up, he founded that there is no breakage of dentureframework, good clasp retention, and color stability of Bio-HPP.[12]

PEEK can be used to make the complete denture. Forcomplete denture fabrication, computer-aided design/computeraidedmanufacturing system is required. It is also used in theconstruction of a removable obturator. Costa-Palau et al. usedPEEK to make maxillary obturator in a patient with partialmaxillary and mandibular edentulism. After 6 months of followup,they found that strength and appearance of the bond weresatisfactory. There was no marginal leakage from the prosthesis.[13]

Advantages
  1. Esthetically more pleasing.
  2. Less density, so lighter in weight.
  3. Non-metallic.
  4. Less irritation and allergic reactions.
  5. Patient acceptance is more.
  6. The processing procedure is easy and less time consuming.

Journal of Advanced Clinical & Research Insights, January-February, Vol 6, 2019 25

Pai, et al. Polyetheretherketone in prosthodontics

Table 3: Surface modifications of PEEK
Polyetheretherketone in prosthodontics � A review
PEEK: Polyetheretherketone, UV: Ultraviolet, TiO2: Titanium oxide, HA: Hydroxyapatite, Ti: Titanium, PIII: Plasma immersion ion implantation,EBE: Electron-beam evaporation

Disadvantages
  1. High cost.
  2. Chemical processing is tough, due to its low surface energy.
  3. Specific machines (e.g., 5 axial milling machines) required forprocessing.

Conclusion

This article reviewed the applications of PEEK in different fieldsof dentistry. Although PEEK has various benefits overcurrentrestoratives, due to its higher cost and limitation in certainphysical properties, it is still under research. It can be a goodalternative to various dental restoratives, but sufficient studiesand clinical trials still required.

References
  1. Toth JM, Wang M, Estes BT, Scifert JL, Seim HB 3rd, Turner AS,et al. Polyetheretherketone as a biomaterial for spinalapplications. Biomaterials 2006;27:324-34.
  2. Kurtz SM, Devine JN. PEEK biomaterials in trauma, orthopedic,and spinal implants. Biomaterials 2007;28:4845-69.
  3. Najeeb S, Zafar MS, Khurshid Z, Siddiqui F. Applicationsof polyetheretherketone (PEEK) in oral implantology andprosthodontics. J Prosthodont Res 2016;60:12-9.
  4. Rees JS, Jacobsen PH. The elastic moduli of enamel and dentine.Clin Mater 1993;14:35-9.
  5. Skinner HB. Composite technology for total hip arthroplasty.Clin Orthop Relat Res 1988;235:224-36.

 
  1. Ha SW, Kirch M, Birchler F, Eckert KL, Mayer J, Wintermantel E,et al. Surface activation of polyetheretherketone (PEEK) andformation of calcium phosphate coating by precipitation.J Mater Sci Mater Med 1997;8:683-90.
  2. Rahmitasari F, Ishida Y, Kurahashi K, Matsuda T, Watanabe M,Ichikawa T. PEEK with reinforced materials and modificationsfor dental implant applications. Dent J 2017;5:35.
  3. Donovan TE, Cho GC. Esthetic considerations with removablepartial dentures. J Calif Dent Assoc 2003;31:551-7.
  4. Ito M, Wee AG, Miyamoto T, Kawai Y. The combination of a nylonand traditional partial removable dental prosthesis for improvedesthetics: A clinical report. J Prosthet Dent 2013;109:5-8.
  5. Fueki K, Ohkubo C, Yatabe M, Arakawa I, Arita M, Ino S,et al. Clinical application of removable partial dentures usingthermoplastic resin-part I: Definition and indication of nonmetalclasp dentures. J Prosthodont Res 2014;58:3-10.
  6. Arda T, Arikan A. An in vitro comparison of retentive forceand deformation of acetal resin and cobalt-chromium clasps.J Prosthet Dent 2005;94:267-74.
  7. Zoidis P, Papathanasiou I, Polyzois G. The use of a modifiedpoly-ether-ether-ketone (PEEK) as an alternative frameworkmaterial for removable dental prostheses. A Clinical report.J Prosthodont 2016;25:580-4.
  8. Costa-Palau S, Torrents-Nicolas J, Brufau-de Barbera M,Cabratosa-Termes J. Use of polyetheretherketone in thefabrication of a maxillary obturator prosthesis: A clinical report.J Prosthet Dent 2014;112:680-2.

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