STATEMENT OF PROBLEM: Controversy exists concerning the preferred cavity design for posterior ceramic restorations to improve their resistance to fracture under occlusal load. PURPOSE: The aim of this study was to assess the resistance to fracture of leucite-reinforced ceramic restorations placed on molars with different cavity preparation designs. MATERIAL AND METHODS: Ninety noncarious molars were selected, stored in 0.2% thymol solution, and divided into 9 groups (n = 10): IT, intact teeth; CsI, conservative inlay; ExI, extensive inlay; CsO/mb, conservative onlay with mesio-buccal cusp coverage; ExO/mb, entensive onlay with mesio-buccal cusp coverage; CsO/b, conservative onlay with buccal cusp coverage; ExO/b, entensive onlay with buccal cusp coverage; CsO/t, conservative onlay with total cusp coverage; ExO/t, extensive onlay with total cusp coverage. Teeth were restored with a Leucite-reinforced ceramic (Cergogold). The fracture resistance (N) was assessed under compressive load in a universal testing machine. The data were analyzed with 1-way and 2-way analyses of variance, followed by the Tukey HSD test (alpha = .05). Fracture modes were recorded, based on the degree of tooth structure and restoration damage. RESULTS: One-way analysis showed that intact teeth had the highest fracture resistance values. Two-way analyses showed no significant differences for the isthmus extention factor, but showed a significant difference for the preparation design type of fracture (P = .03), and also for the interaction between both factors (P = .013). The fracture mode observed in all groups tended to involve only restorations. CONCLUSION: Within the limitations of this study, it was observed that cuspal coverage does not increase fracture resistance of the posterior tooth-restoration complex restored with leucite-reinforced ceramics.
STATEMENT OF PROBLEM: Controversy exists concerning the preferred cavity design for posterior ceramic restorations to improve their resistance to fracture under occlusal load. PURPOSE: The aim of this study was to assess the resistance to fracture of leucite-reinforced ceramic restorations placed on molars with different cavity preparation designs. MATERIAL AND METHODS: Ninety noncarious molars were selected, stored in 0.2% thymol solution, and divided into 9 groups (n = 10): IT, intact teeth; CsI, conservative inlay; ExI, extensive inlay; CsO/mb, conservative onlay with mesio-buccal cusp coverage; ExO/mb, entensive onlay with mesio-buccal cusp coverage; CsO/b, conservative onlay with buccal cusp coverage; ExO/b, entensive onlay with buccal cusp coverage; CsO/t, conservative onlay with total cusp coverage; ExO/t, extensive onlay with total cusp coverage. Teeth were restored with a Leucite-reinforced ceramic (Cergogold). The fracture resistance (N) was assessed under compressive load in a universal testing machine. The data were analyzed with 1-way and 2-way analyses of variance, followed by the Tukey HSD test (alpha = .05). Fracture modes were recorded, based on the degree of tooth structure and restoration damage. RESULTS: One-way analysis showed that intact teeth had the highest fracture resistance values. Two-way analyses showed no significant differences for the isthmus extention factor, but showed a significant difference for the preparation design type of fracture (P = .03), and also for the interaction between both factors (P = .013). The fracture mode observed in all groups tended to involve only restorations. CONCLUSION: Within the limitations of this study, it was observed that cuspal coverage does not increase fracture resistance of the posterior tooth-restoration complex restored with leucite-reinforced ceramics.