Fracture Resistance of Human Enamel and Three All-Ceramic Crown Systems on Extracted Teeth

This in vitro study measured the fracture resistance of intact extracted molars and three types of all-ceramic crowns: feldspathic porcelain, glass-ceramic, and glass-infilt rated alumina. All crowns were of a simplified three-cusp occlusal configuration, and were placed on prepared, extracted third molars. The ceramic crowns were bonded to dentin with a resin composite cement, except for 10 of the feldspathic crowns, which were luted with zinc phosphate cement. The fracture resistance was measured using a spherical steel indenter that contacted the occlusal surface at three points. A total of 40 ceramic crowns and 50 extracted maxillary third molars were tested. The Weibull distribution was used for data analysis. Intact extracted teeth were significan tly stronger than all-ceramic crowns. Of the ceramic restorations, the glass-infiltrated alumina crowns exhibited the highest fracture resistance.