The Performance of PEKK versus Zirconia Abutments for Screw-Retained Crowns in Two-Piece Zirconia Implants: an in vitro Study.

Objectives: This study aimed to compare the in vitro performance of anterior and posterior crowns with screw-retained polyetherketoneketone (PEKK) or zirconia abutments on two-piece zirconia implants.

Materials and methods: Monolithic incisor and molar zirconia crowns (n=8 per group) were cemented on either PEKK or zirconia screw-retained abutments on zirconia implants. Molar and incisor crowns were also cemented on screw-retained titanium abutments on titanium implants as control. All specimens were subjected to combined mechanical loading (1.2 × 106 cycles of 50N, f = 1Hz) and thermal cycling (2 × 3000 × 5°C/55°C cycles of 2 min). Complications, such as loosening of the crowns and fractures, were observed. The surviving specimens were subjected to a fracture test. Descriptive statistics were applied to complications, survival times, and fracture forces.

Results: The occurrence of complications depended significantly on location (anterior or posterior) and material (P<.0001). While the incisor test groups presented higher failure rates for both PEKK and zirconia abutments, the survival rates of the molar-shaped crowns of both test groups were comparable to those of the titanium control group. This highly significant interaction is caused by a highly significant difference in location for PEKK and zirconia (P<.05). The titanium control group showed uniform performance independent of the simulated site.

Conclusion: PEKK abutments showed high survival rates for in vitro simulated molar sites. Screw-retained zirconia abutments have shown higher complication rates, especially in simulated anterior sites. Neither zirconia nor PEKK abutments seem to be recommendable in clinical application for anterior indication.