Influence of material selection on the risk of inlay fracture during pre-cementation functional occlusal tapping

Objective: To evaluate in vitro the pre-cementation resistance of CAD/CAM inlays subjected to functional occlusal tapping. Methods: An extracted tooth model (molar and premolar) with simulated bone and periodontal ligament was used to make a medium-size mesio-occlusal inlay preparation (molar). Immediate dentin sealing was applied to the prepared tooth. The corresponding inlays were fabricated with Cerec either using composite resin (Paradigm MZ100) or ceramic (e.max CAD and Mark II) blocks (n = 14). A high marginal ridge was designed in order to generate hyper-occlusion. Pre-cementation occlusal tapping was simulated using closed-loop servo-hydraulics at 2 Hz, starting with a load of 40 N, followed by 80, 120, 160, 200, 240, and 280 N (10 cycles each). All samples were loaded until fracture or to a maximum of 70 cycles. Groups were compared using the life table survival analysis (p = 0.016, Bonferroni method). Results: Survival probability was e.max CAD > MZ100 > Mark II. None of the specimens survived the 70 cycles except for two e.max CAD inlays (survival: 14%). Significance: Material selection has a significant effect on the risk of Cerec inlay fracture during pre-cementation functional occlusal tapping.