Fracture resistance of class II preformed ceramic insert and direct composite resin restorations

Objectives. This study aimed to compare the fracture resistance of two different posterior restorations in class II cavities. Methods. In this study 24 extracted intact human mandibular molars (for testing) and 24 extracted intact human teeth (for achieving contact) were used. The test teeth were divided into two groups and then mounted in normal anatomic relationship with intact human teeth on the same holder. Thus 12 pairs of teeth were constituted in each group. Class II MO cavities were prepared on testing teeth in each holder. The other tooth was used for achieving contact. The cavities in group 1 were restored with direct composite resin with the manufacturerʹs flowable composite. The cavities in group 2 were restored with SONICSYS inlays (preformed ceramic insert) according to the manufacturerʹs instructions. The marginal ridges of the restorations were loaded at an angle of 13.5° to the long axis of the tooth in an Instron testing machine until failure occurred. Results. Analysis of mean failure loads indicated that class II SONICSYS inlay restorations (group 2) had a significantly greater fracture resistance than did class II direct composite resin restorations with flowable composite (P=0.000). Conclusions. The SONICSYS inlay system provided greater fracture resistance than direct composite resin with flowable composite.