Effect of Vent Hole and Cement Type on Fracture Resistance of CAD-CAM Monolithic Zirconia Crowns

Purpose To assess the fracture resistance of monolithic zirconia crowns cemented with different types of cement on cement-retained implant abutments. Materials and methods Forty implant analogs were positioned in acrylic resin blocks, and cement-retained straight implant abutments were fastened to the analogs. Crowns were designed with/without occlusal vent holes and produced from monolithic zirconia blocks by the CAD-CAM technique. The two crown types were divided into two groups and cemented with resin and zinc-polycarboxylate cement under 5 kg weight. A universal testing machine applied compressive forces to the crowns until fracture. Fracture resistance values were analyzed using two-way ANOVA and the independent samples t-test with statistical significance set at p < 0.05. Results According to the two-way ANOVA results, although the crown design did not have a significant effect on fracture resistance (1417.65 +/- 337.39 N, 1565.16 +/- 517.12 N; crowns with and without vent holes, respectively), the main effect of the cement variable on the fracture resistance was significant. Zinc-polycarboxylate cement (1680.1 +/- 375.23 N) showed higher fracture resistance than resin cement (1302.71 +/- 420.64 N) in the crowns designed with vent holes (p < 0.005). Conclusion The use of cement-retained implant-supported monolithic zirconia crowns with an occlusal vent hole is safe, and zinc-polycarboxylate cement use may be an appropriate choice for cementation of these crowns.