In-Vitro-Examination of Polyetheretherketone Fixed Partial Dentures with Different Core Designs

Objectives: The aim was to evaluate the influence of core design on the behaviour of 3-unit fixed partial dentures (FPD) made of unfilled polyetheretherketone (PEEK) during artificial ageing and fracture test.

Methods: Circularly prepared abutment teeth of defined size were made of PMMA (PalapressVario: Kulzer, G) and embedded pairwise (gap width: 10mm) after covering their roots with polyether (0.5mm; Impregum: 3m Espe, G) to simulate periodontal mobility. Four series of FPDs (n=8 per series) were made of unfilled PEEK (PEEK-Optima: Juvora; UK) in different denture designs: a) minimal core b) anatomically reduced core c) anatomically reduced core + unveneered basal pontic d) fully anatomic denture without veneering. Veneering (group a/b/c) was done with a micro hybrid composite (Sinfony: 3m Espe) after PEEK surface treatment (Rocatec Pre: 3m Espe; Clearfil Alloy Primer + Clearfil Opaque: Kuraray, Osaka, J). A silicon (Regofix: Dreve, G) mould was used for reproducible veneering thickness. Adhesive luting was done with dual curing composite cement (VariolinkII: Ivoclar-Vivadent, FL). Chewing simulation was performed with 1.2x10⁶ occlusal loadings (50N; antagonistic human molar) and 6000x5/55°C thermal cycles. Behaviour during TCML was recorded optically. Fracture strength was determined after TCML in a universal-testing-machine (crosshead speed: 1mm/min; failure determination: 10% loss of current force; UTM 1446: Zwick, G).

Results: FPDs showed wear signs but no decementation or damage during TCML. Fracture strength after TCML [N]:

Conclusions: Regarding 500N in posterior areas as a threshold level for needed fracture forces, all tested morphologies for veneered PEEK-Optima bridges showed sufficient fracture strengths. Optimised core designs should be preferred for veneered restorations.