Contribution of Peek in Dental Prothesis

Objective: Our work aimed to study the clinical contribution of Polyetheretherketone (PEEK) in dental prostheses.

Material and methods: A bibliographic search was carried out through the PubMed and Scopus search engines, using keywords. Initially, a reading of the titles and abstracts was performed to select articles that met the inclusion criteria. A reading of the full text of each reference was then performed.

Results: Of the selected articles, 12 articles were retained after reading the full text. The studies found confirmed the contribution of PEEK in prostheses due to its favorable mechanical, chemical, and physical properties.

Conclusion: The PEEK is a high-performance polymer that can be used in fixed and removable prostheses in different applications. However, further clinical and in vitro studies are needed to evaluate its long-term performance.

Introduction

The evolution of dentistry and the development of its technologies can be achieved by innovating or improving materials. Indeed, the possible allergies caused by nickel-chromium as well as the technical difficulties encountered in the use of titanium have justified the need to look for a more suitable material. New materials such as Polyetheretherketone (PEEK) have opened up a wide range of prosthetic therapies. PEEK appears in the medical literature as a non-metallic alternative to Titanium. It has mechanical properties close to those of the bone that allow it to be perfectly integrated on a biological level. Nevertheless, PEEK biointeresis is the main limitation of this material. Surface treatment or hybridization (PEEK-ceramics and CFR-PEEK) overcomes this problem by giving it a bioactive character [1]. PEEK is a high-performance, partially crystalline thermoplastic polymer used in a variety of applications:

• Framework for metal-free fixed dentures, removable dentures, implant-supported fixed and adjunctive dentures
• Endocrowns and fixed resin-bonded dentures
• Dental implants, implant abutments, healing abutments
• Occlusal splints

The literature presents the PEEK as a biocompatible material with good mechanical properties, good wear resistance, chemical stability, polish ability, good wear resistance, and low affinity to dental plaque. This material is a promising alternative to metal and zirconium alloys in the fabrication of various fixed and removable prosthetic devices. The objective of this study is to investigate the real contribution of PEEK in dental prostheses.

Methods

To meet our objective, we conducted research in the Pubmed and Science Direct search engines using 5 Anglo-Saxon keywords: PEEK, prosthodontics, dentistry, Polyetheretherketone; and dental prostheses.

An initial reading of titles and abstracts was performed to select articles that met the inclusion criteria listed below:

• Articles studying the use of PEEK in dental prostheses;
• In vivo, in vitro, literature reviews, systematic reviews, and meta-analysis studies;
• Articles published after 2015;
• Articles written in English.

A full content read of the selected references was performed to ensure inclusion criteria and to extract data relevant to Peek.

The following information was obtained from the included publications: author(s), year of publication, Field of application studied, and main outcomes/findings.

Results and Discussion

Among the 45 studies found, 23 works were selected after reading the titles and abstracts. In a second reading based on the whole text 12 articles were selected (Fig. 1) The summary of the results of the studies found is illustrated in Table I.

Fig. 1. Flowchart for articles selection process.

Table I. Summary of Data from Studies on the Use of PEEK

Authors	Field of application studied	Results
Papathanasiou et al. [2]	Removable prostheses by CAD-CAM	Colour stability, gloss and surface roughness, PEEK could be a promising material
	Prosthesis fixed by CAD-CAM
Najeeb et al. [3]	Peek as an implant	PEEK can be used in many areas of dentistry due to its mechanical and physical properties
	Fixed prosthesis
Blanch-Martínez et al. [4]	Implant-supported prosthesis	PEEK offers greater lightness, good aesthetics and biocompatibility.
Mazen et al. [5]	Fixed prosthesis	The pressed peek crown is more suitable than the crown made with Peek in CAD-CAM
Stawarczyk et al. [6]	Veneers	Despite the cracks in the pre-treatment, this did not affect the final result
Wachtel et al. [7]	Fixed prosthesis	PEEK implant crowns appear to be applicable as permanent implant-supported crowns compared to superstructures made of conventional materials.
Li et al. [8]	Inlay-core manufacturing	The manufacture of peek inlay-core has shown good retention
Gedeminas et al. [9]	Fixed prosthesis	The use of peek is recommended in fixed prosthesis
Liebermann et al. [10]	Studies of different computer-aided designs and manufacturing (CAD/CAM)	The hardness parameters of PEEK were comparable to those of PMMA
Taufall et al. [11]	Fixed prosthesis	The digital workflow showed the highest resistance to breaking load than the conventional method
Rocha et al. [12]	Surface treatment of PEEK-based fixed prostheses	Physical and chemical surface treatments have been effective in promoting a similar bond between PEEK, cement and dentin
Islam et al. [13]	Removable prosthesis	PEEK can be considered as a useful alternative reinforcement material for edentulous patients of Kennedy I class

The objective of our study was to evaluate the contribution of PEEK in dental prostheses. The use of this material in prosthetics has been widely documented in the various selected studies.

In fixed prosthesis, PEEK is a relatively new material, its favourable mechanical properties allow its use as a framework material for fixed dental prostheses such as crowns, endocrowns [2]–[5]. In implantology, PEEK can also be used for the fabrication of implant abutments, healing screws, custom healing abutments, and healing caps placed at the surgical stage for the creation and maintenance of the desired emergence profile [3], [5]. The use of PEEK by computer-aided design and fabrication can also result in the fabrication of occlusal splints, intra-radicular posts, and provisional restorations [6]–[9].

Research teams have justified the use of PEEK in prosthodontics by studying its properties. Papathanasiou et al. showed that PEEK could be a promising material given its colour stability, glossiness, and surface roughness [2], [12]. Najeeb et al. approved the mechanical and physical performances of PEEK [3]. For Blanch and al, the greater lightness offered by this material, and its biocompatibility justify its use [4]. As for hardness, the Liebermann team showed that this property was comparable to that of PMMA resin [10].

As regards multi-component prostheses, Papathanasiou et al. [2] has shown that a three-component PEEK framework deforms from 1200 N and with a connection failure at 1383 N. If 870 N is considered the maximum masticatory force in the posterior, PEEK could be considered an ideal material for use in posterior restorations. For the fabrication technique, the study of MAZEN and al showed that the pressed Peek crown is still more suitable than the crown fabricated with Peek in CAD-CAM [5]. Other studies revealed that three CAD-CAM machined fixed dental prostheses showed a decrease in deformation and a higher failure load (2354 N) than those pressed in granular form (1738 N). We also note that PEEK prosthetic appliances made by digital techniques are more mechanically resistant when compared with appliances made by conventional techniques [11].

For provisional restorations, the comparison of provisional crowns made of Peek CAD-CAM with provisional crowns made of different materials (VITA CAD Temp, Telio CAD-Temp, and Protemp) led to the conclusion that provisional restorations made of PEEK have a better fit and fracture resistance than conventional provisional crowns.

The comparison between provisional crowns made of Peek CAD-CAM and provisional crowns made of other materials (VITA CAD Temp, Telio CAD-Temp, and Protemp) led to the conclusion restorations made of PEEK have a better fit and fracture resistance than conventional provisional crowns.

In removable prostheses, this material has been proven, Islam et al. [13] showed that PEEK can be an interesting alternative for edentulous patients of Kennedy class 1. Papathanasiou et al. have confirmed the properties of PEEK for use in removable prostheses [2]. PEEK is also used as a framework in combination with acrylic resin and prosthetic teeth and thermosetting denture bases as an alternative to cobalt chrome frameworks. Peek is also used for composite prostheses that combine fixed crowns and removable prostheses. In the area of prosthetic restorations, ground PEEK can be used for the fabrication of maxillofacial restorations with an obturator. The use of modified PEEK for the fabrication of a prosthetic part combined with a PMMA base material has been documented. This modified PEEK polymer with 20% ceramic fillers (BioHPP; Bredent GmbH,) offers excellent biocompatibility, good mechanical behaviour, high temperature, strength, and chemical stability. With a modulus of elasticity of approximately 4 GPa, it has an elastic behaviour comparable to the bone, which could reduce the stresses transferred to the abutment teeth. Due to its white colour, it allows the fabrication of a prosthetic part with improved aesthetics compared to conventional reconstructions. Other advantages related to good polishing, wear resistance, and low affinity to plaque, have led to various applications in dentistry [10], [13].

The results of the in vitro studies confirm the remarkable properties of PEEK. This material has favourable properties such as excellent biocompatibility, good mechanical properties, and good thermal and chemical resistance. The selected studies in our literature review stated that PEEK could be a viable alternative for a wide range of manufactured fixed and removable dental prostheses, however, its long-term performance has not yet been tested.

Conclusion

Due to its biocompatibility, high mechanical and physical properties, and lightweight, PEEK remains a suitable material both as a framework in fixed prostheses and as a removable prosthesis in place of cobalt chromium in various applications. However, further clinical and in vitro studies with standard protocols are needed to evaluate its long-term performance.