Evaluation of fracture resistance of ceramic veneers with different preparation designs and loading conditions: An in vitro study

PURPOSE: The purpose of this study was to evaluate the effect of incisal butt joint and incisal overlap design on the fracture resistance of ceramic veneers under two different loading conditions, i.e., 125° and 60° representing protrusive and intercuspal movements, respectively. MATERIALS AND METHODS: Thirty-two maxillary central incisors were divided into two groups of sixteen specimens each and were prepared with incisal butt joint and incisal overlap design. Ceramic veneers were fabricated and cemented. Both the groups were further divided and mechanical testing to evaluate the fracture resistance were done using the universal testing machine. The values were recorded in Newton along with the assessment of the failure mode of both veneer and the tooth. RESULTS: Unpaired t-test showed a significant difference (P < 0.05) with butt joint design having higher fracture resistance than palatal overlap design with the mean value of 409.50N at 60° angle and 473.37N at 125° angle. Paired t-test depicted a significant difference for both the designs at 125° than at 60° angle (P < 0.05). Chi-square analysis showed more number of intact veneers with butt joint design; however, there was no significant difference (P > 0.05). Failure mode of teeth showed more number of coronal fracture followed by cervical fracture and root fracture, but there was no significant difference between the two groups (P > 0.05). CONCLUSION: Butt joint design had higher fracture resistance than palatal overlap design. Under functional loads for both designs, fracture resistance was higher at 125° than at 60° angle.