Mechanical Fatigue Analysis of PEEK as Alternative to Zirconia for Definitive Hybrid Abutments Supporting All-Ceramic Crowns

Purpose: The aim of this study was to inspect the mechanical fatigue behavior of an implant-supported restorative system using polyether ether ketone (PEEK) and yttria partially stabilized zirconia polycrystals (YZ) as materials for customized definitive implant-supported hybrid abutments, supporting two types of all-ceramic restorations: translucent zirconia (TZ) and lithium disilicate (LD) monolithic crowns. Materials and Methods: Forty Morse taper implants were included in epoxy resin. Titanium intermediary abutments were placed, and the specimens were randomly allocated into four groups (n = 10) according to the customized hybrid abutment material (PEEK or YZ) and the monolithic crowns (TZ or LD) representing a maxillary central incisor crown. The specimens were subjected to a mechanical fatigue test (step-stress analysis) by means of an initial 200-N load for 5,000 cycles and subsequent increase of 50 N (step-size) at each 10,000 cycles, until failure occurred. The load at failure and number of cycles until failure were recorded; survival probabilities and specimen displacement were calculated for each step. The failure pattern was evaluated, and the Weibull modulus was obtained for each condition. Results: Fatigue of both types of crowns was not influenced by the abutment material (LD-PEEK = LD-YZ; TZ-PEEK = TZ-YZ). In the PEEK abutment, the values obtained in the LD and TZ crowns showed no statistical difference; however, in the YZ abutment, the TZ crown presented a load at failure value that was statistically higher than that for LD. Failure pattern analysis revealed a higher prevalence of crown fracture for LD groups, while screw/implant platform fractures were shown for TZ groups. Conclusion: YZ and PEEK hybrid abutments promoted similar fatigue levels regardless of the crown materials, TZ crowns promoted a higher fatigue level than LD ones when associated with YZ abutments, and LD crowns promoted a similar fatigue level to TZ ones when associated with PEEK custom abutments. Higher prevalence of crown fractures was shown for LD and screw/implant platform fractures for TZ groups.