Effect of screw access hole on the fracture load of implant-supported monolithic zirconia single crown

Implant-supported cement-screw-retained crowns combine the advantages of screw-retained and cement-retained crowns. However, the occlusal screw access hole interrupts porcelain integrity, which may result in porcelain cracks or fractures. There is insufficient scientific evidence to prove that screw access holes affect the fracture load of implant-supported monolithic zirconia crowns. In this study, we investigated the effects of the screw access hole and its preparation technique on the fracture load of implant-supported monolithic zirconia single crown. The crowns were designed for the maxillary right first premolar. Three techniques analysed for screw access hole preparations included computer-aided designed/computer-aided manufactured (CAD/CAM) before sintering, manually prepared after sintering, and then resintering. Our findings show that the screw access holes and preparation techniques have no significant effects on the fracture load of implant-supported monolithic zirconia single crown. On the other hand, the screw access hole preparation techniques affect failure initiation in implant-supported monolithic zirconia single crown.