Effect of a new resin inlay/onlay restorative material on cuspal reinforcement

Nine maxillary premolars were restored with composite resin inlays involving large intracoronal cavity preparations. Buccal and lingual bonded strain gauges measwed the cuspal flexure under a carefully controlled application of occiusal force. The intact tooth was compared with the corresponding preparation and final restoration. The preparation itself greatly reduced the coronal rigidity, but this was completely recovered in the restored tooth, within the functional force of 111 N. A stiffness ratio showed a 97% recovery. From the point of view of cuspat strength, this may mean that larger intracoronal restorations are feasible with this type of reitoration. However, other factors, such as ehairside time and complexity, and material properties, such as occiusal wear, have to be taken into consideration.