05 September 2023

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Can polyetherketone replace titanium and zirconia in implant-supported prosthesis?

By Lorenzo Breschi and Annamaria Forte

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Introduction

A precise fit between the implant and prosthetic framework is crucial for successful and long-term integration of an implant-supported prosthesis (ISP). Any discrepancies may lead to stress-related issues like implant and abutment fractures, screw problems and bone loss.

The most used framework materials include: 

• titanium (Ti), commonly chosen for good biocompatibility and mechanical properties and the possibility to be produced with CAD-CAM techniques despite the gray color, difficulty bonding with certain materials, and milling challenges
• zirconia (Zir), which presents good toughness, strength, biocompatibility and aesthetics but its brittleness can lead to technical and biological problems due to stress transfer, and
• polyetherketone (PEEK), disclosing an elastic modulus close to that of the bone, transmitting minimal force to the abutment.

This in vitro study aimed to investigate the differences in terms of fit and fracture strength among these materials. 

Materials and methods

A total of 30 ISP epoxy resin casts were obtained from a typodont with one straight implant (Nobel Biocare) in the mandibular right canine region and one implant with a 30-degree distal tilt in the mandibular right first molar region. 

All frameworks (n=10) were fabricated on their own epoxy resin cast with multiunit abutment replicas by using a computer-aided design and computer-aided manufacturing system (exocad-Yenadent). The PEEK and zirconia frameworks were fabricated with Ti-bases. Primer (MKZ) and resin cement (DTK adhesive) were used to cement the frameworks to the Ti-bases under a static load of 10 N. 

After thermomechanical aging (1.2×106 cycles, 120 N, 5 °C-55 °C), marginal gaps between the Ti-bases and cemented frameworks and vertical and passive fits between the Ti-bases and framework and multi-unit abutments were measured by using a stereomicroscope (Euromex) at ×100 magnification. Fracture resistances and types were then determined by using a universal test machine and a stereomicroscope at ×40 magnification. 

Data were analyzed by using 1-way analysis of variance (ANOVA) and the Tukey HSD and Fisher-Freeman-Halton tests (α=.05). 

Results

The marginal gaps of the PEEK and zirconia frameworks were respectively 83.5 ±27.1 and 81.8 ±17.8 μm. PEEK (23.7 ±4.6) and zirconia (32.9 ±8.7) had a better vertical fit (μm) than Ti (52.5 ±10.6) (P<.001). Zir (49.3 ±16.2) (P<.001) and PEEK (70.9 ±19.6) (P>.05) frameworks had better passive fit (μm) than Ti (91.3 ±24.2). Ti had the highest mean fracture resistance (N) (14800.2 ±3442.3) followed by Zir (7318.7 ±1385.1) and PEEK (3448.9 ±486.6) (P<.001). Fracture types were different in distinct groups (P<.001). 

Conclusions 

Within the limitation of this study, the authors concluded that the PEEK and Zir frameworks with Ti bases had better vertical and passive fit than the Ti frameworks. All ISP frameworks represented mean marginal fit below 92 μm and withstood physiologic occlusal forces after thermomechanical aging. 

Atsu S, Erol U. "Marginal fit and fracture resistance of polyetheretherketone, zirconia, and titanium implant-supported prosthesis frameworks for a partially edentulous arch after thermomechanical aging." J Prosthet Dent. 2023 Aug 22: S0022-3913(23)00487-0. doi: 10.1016/j.prosdent.2023.07.015.