Fracture resistance of computer-aided design/computer-aided manufacturing-generated composite resin-based molar crowns

摘要

The aim of this study was to investigate whether different fabrication processes,such as the computer-aided design/computer-aided manufacturing (CAD/CAM) systemor the manual build-up technique, affect the fracture resistance of compositeresin-based crowns. Lava Ultimate (LU), Estenia C&B (EC&B), and lithium disilicateglass-ceramic IPS e.max press (EMP) were used. Four types of molar crownswere fabricated: CAD/CAM-generated composite resin-based crowns (LU crowns);manually built-up monolayer composite resin-based crowns (EC&B-monolayercrowns); manually built-up layered composite resin-based crowns (EC&B-layeredcrowns); and EMP crowns. Each type of crown was cemented to dies and the fractureresistance was tested. EC&B-layered crowns showed significantly lower fractureresistance compared with LU and EMP crowns, although there was no significantdifference in flexural strength or fracture toughness between LU and EC&B materials.Micro-computed tomography and fractographic analysis showed that decreasedstrength probably resulted from internal voids in the EC&B-layered crowns introducedby the layering process. There was no significant difference in fracture resistanceamong LU, EC&B-monolayer, and EMP crowns. Both types of compositeresin-based crowns showed fracture loads of >2000 N, which is higher than themolar bite force. Therefore, CAD/CAM-generated crowns, without internal defects,may be applied to molar regions with sufficient fracture resistance.