Fracture resistance of teeth restored with dentin-bonded crowns: the effect of increased tooth preparation.

This investigation assessed the effect of variations in preparation on fracture resistance of teeth restored with all-ceramic crowns placed with a resin composite luting material after the dentinal surface had been treated with a dentinal bonding system. Four groups of 10 sound, unrestored, maxillary premolars were prepared. In group A, minimal preparations of 6-degree taper, 2-mm occlusal reduction, and a knife-edged margin were carried out. Preparations in group B received 6-degree taper, 3-mm occlusal reduction, and a 1-mm shoulder. Preparations in group C were as in group B, but with 2-mm occlusal reduction over buccal cusp and minimal cervical preparation buccally. Preparations in group D were as in group B, but with 2-mm occlusal reduction. The restored teeth were subjected to compressive loading. Mean fracture loads of 0.77 kN, 0.99 kN, 0.91 kN, and 0.78 kN were recorded for groups A, B, C, and D, respectively. Statistical analysis failed to reveal any difference among the groups.