Laboratory study of fracture resistance and failure mode of porcelain laminate veneers with different preparation depths in endodontically treated teeth.

Purpose: To compare the fracture resistance and failure mode of porcelain laminate veneers with different preparation depths in endodontically treated teeth.

Methods: Root canal treatment was performed for 40 maxillary central incisors, and then the teeth were divided into four groups (n= 10). The preparation depths were as follows: Group A: 0.9 mm, Group B: 0.6 mm, Group C: 0.3 mm, and in all three groups, 2 mm butt joint incisal reductions were performed; Group D was a control group with no preparation. Then 30 lithium disilicate porcelain veneers were milled by CAD- CAM method and cemented. After that, all specimens were subjected to cyclic loading and thermal cycling and finally were tested by a universal testing machine until failure occurred.

Results: The mean failure loads (N) after exposure to continuous load were as follows: Group A: 625.70 (401.45-1037.77), Group B: 780.32 (222.93-1391.82), Group C: 748.81 (239.68-1241.87) and Group D (control) : 509.88 (84.42-1025.85) and P= 0.216. Analysis of failure mode in four groups showed that P= 0.469. There was no significant difference between the control and the other groups. In this study, 0.3, 0.6 and 0.9 mm depths of preparation for porcelain laminate veneers for endodontically treated teeth had no significant difference in fracture resistance and failure mode with non-prepared teeth.

Clinical significance: Reasonable consideration might be given to porcelain laminate veneer treatment for teeth that have become discolored and resistant to bleaching (such as instances where discoloration is severe following root canal treatment). This approach is considered to be on the conservative side, and has demonstrated that a labial preparation depth reduction of up to 0.9 mm does not have any impact on the failure mode or fracture resistance of endodontically-treated teeth.