Implant angulation and fracture resistance of one-piece screw-retained hybrid monolithic zirconia ceramic restorations

Abstract

Objective This study aimed to investigate the fracture resistance of one-piece screw-retained hybrid monolithic zirconia ceramic restorations in different implant angulations. Materials and methods Three implant fixtures were embedded in acrylic resin blocks with 0｡, 15｡, and 25｡angulations. For each group of implant angulations, 11 screw-retained one-piece monolithic zirconia restorations were made and bonded to the titanium inserts with a dual-cure self-adhesive resin. The complexes were screwed to the implant fixtures with titanium screws. The samples were thermocycled, subjected to compressive load, and fracture modes were recorded. One-way ANOVA and post hoc Tukey’s test were used for statistical analyses (α = 0.05). Results One-way ANOVA showed the fracture resistance to be significanltly different among the study groups (P = 0.036). The 15｡group was significantly more resistant than 0｡ (P = 0.031). However, the 25｡ group was not significantly different from the 15｡ (P = 0.203) and 0｡ groups (P = 0.624). Fractures occurred only on the restorations, not at the screw levels. Conclusions Tilting the implant up to 15｡ improves the fracture resistance of one-piece screw-retained hybrid monolithic zirconia restorations; however, increasing the tilt to 25｡ would not yield restorations with significantly better fracture strength than the straight implants. Accordingly, when angulated implants are indicated in the esthetic zones, one-piece screw-retained hybrid monolithic zirconia ceramic restorations can be used with acceptable fracture strength.