The Performance of PEKK vs Zirconia Abutments for Screw-Retained Crowns in Two-Piece Zirconia Implants: An in vitro Study
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. 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 50 N, f = 1 Hz) and thermal cycling (2 × 3000 × 5°C/55°C cycles of 2 minutes). 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. 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 with those of the titanium control group. This highly significant interaction is caused by a substantial difference in location for PEKK and zirconia (P < .05). The titanium control group showed uniform performance independent of the simulated site. 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 are recommended in clinical application for anterior indication.
Differences in the nominative bone level after embedment related to the parallel shape of the implant.
Schematic drawing of the mechanical loading on 2 eccentric points.
Representative details of the complications: (a) abutment fracture, (b) and (c) zirconia implant fracture, (d) abutment loosening.
Survival in terms of cycles survived for titanium, zirconia, and polyetherketoneketone (PEKK) groups depending on the simulated location (incisors [I] and molars [M]). Crossed lines, eg, titanium vs PEKK, show strong interactions between location and abutment material.
Boxplots showing dependence on location (incisors [I] and molars [M]) and abutment material (titanium [T], zirconia [Z], polyetherketoneketone [PEKK]).
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