Fracture resistance of single-tooth implant-supported all-ceramic restorations after exposure to the artificial mouth

The purpose of this in vitro study was to evaluate the fracture resistance of single-tooth implant-supported all-ceramic restorations, composed of zirconium dioxide all ceramic restorations on different implant abutments, and to identify the weakest component of the restorative system. Forty-eight standardized maxillary central incisor zirconia crowns (Procera) were fabricated for two test groups and one control group (group Al: alumina abutments; group Zr: zirconia abutments; control group Ti: titanium abutments). All abutments were placed on the implants (Replace) using titanium screws. The crowns were adhesively luted using a resin luting agent (Panavia 21) and artificially aged through dynamic loading and thermal cycling. Afterwards, all specimens were tested for fracture resistance using compressive load on the palatal surfaces of the crowns. Pair-wise Wilcoxon rank tests were performed to test for differences in fracture resistance values with a global significance level of 0(.)05. All test specimens survived aging in the artificial mouth. No screw loosening was recorded. The median fracture resistance was 1251, 241 and 457 N for groups Ti, Al and Zr respectively. Statistically significant differences were found for the comparisons of group Ti with groups Al and Zr (P < 0(.)00001), and for the comparison of group Al with Zr (P < 0(.)00001). Results of this study showed that all tested implant-supported restorations have the potential to withstand physiological occlusal forces applied in the anterior region. Because of the low fracture resistance values of group Al, the combination of zirconia crowns and alumina abutments should carefully be considered before clinical application.