Fracture Resistance of CAD/CAM Monolithic Zirconia Crowns Supported by Titanium and Ti-Base Abutments: The Effect of Chewing Simulation and Thermocyclic Aging

Purpose: To evaluate the effect of chewing simulation and thermocyclic aging on the fracture resistance of CAD/CAM monolithic zirconia crowns supported by titanium and Ti-base abutments. Materials and Methods: Two implant abutment groups-titanium (Ti) and titanium base (Ti-base; Medentika)-were used. A total of 40 mandibular first molar CAD/CAM monolithic zirconia crowns (Vita YZ T) were fabricated, then cemented onto the abutments with Panavia V5. Each abutment group was divided into two subgroups (n = 10). The Ti and Ti-base groups were subjected to a single load until fracture, and the Ti/CT and Ti-base/CT groups (CT: chewing simulation and thermocyclic aging) underwent chewing simulation (1.2 x 10(6) cycles x 50 N load, 1.4 Hz) and thermocylic aging (3,911 cycles/5 degrees C to 55 degrees C). The fracture resistances of the crowns were tested with a universal testing machine (1 mm/minute). Shapiro-Wilk and one-way ANOVA test were used for statistical analysis (P =.05). Results: The survival rates after chewing simulation and thermocyclic aging were 100% for both CT groups. The fracture resistance values (mean +/- SD) of the groups were as follows: Ti = 1,718.18 +/- 331.06 N, Ti-base = 1,713.53 +/- 233.24 N, Ti/CT = 1,664.82 +/- 188.62 N, and Ti-base/CT = 1,551.28 +/- 344.79 N. According to one-way ANOVA test results, there was no statistically significant difference between the four groups (P =.526). Conclusion: CAD/CAM monolithic zirconia crowns supported by Ti-base or titanium abutments were found to have sufficient fracture resistance in the treatment of an absent single posterior tooth. However, more in vitro and clinical studies are required to evaluate the long-term performance of Ti-base abutments and CAD/CAM zirconia crowns.