Fracture resistance of endodontically treated premolars restored with ormocer and packable composite

In this study, mesiodistocclusal (MOD) cavity preparations of endodontically treated maxillary premolars that were enlarged to size #50 were restored using three restorative materials (one ormocer, one packable composite, and one high-copper amalgam) and two application techniques (with or without coronal radicular technique). Copper rings were filled with self-curing polymethylmethacrylate resin and the teeth were placed into resin up to the level of the CEJ. The teeth were grouped according to the restorative material and technique, mounted in a Universal Testing Machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. The group restored with packable composite without radicular extension showed the highest resistance to fracture (p < 0.05). Both groups restored with amalgam were significantly weaker than all the other groups (p < 0.05).