In Vitro Failure of Crowns Produced by Two CAD/CAM Systems

Abstract - Previous laboratory studies have demonstrated satisfactory fracture resistance of all-ceramic crowns placed using a resin-composite luting material and a dentine bonding system. This study investigated the fracture resistance of teeth restored using CAD/CAM technology, namely, Zirconia Based crowns and Cerec® produced feldspathic porcelain crowns, both luted with a self adhesive resin luting material (RelyX™ Unicem Clicker™ 3M ESPE). Standardized preparations were carried out on two groups of ten sound, unrestored, maxillary premolar teeth. Ceramic crowns were constructed to have a thickness of 2mm at their midline fissure. Compressive fracture resistance was determined for each group using a Universal Testing Machine The failure modes were also examined visually and interpreted according to a chosen scale. Mean Compressive fracture resistance of 746 (147)N and 1630 (175)N were recorded for the Cerec® and Lava™ groups respectively; differences were statistically significant (p<0.001). The fracture resistance of teeth restored with Lava™ crowns is significantly greater than a similar group of teeth restored with Cerec® crowns.

KEY WORDS: All-ceramic, Self adhesively luted, CAD/CAM, Compressive failure