Resistance to fracture of endodontically treated premolars restored with glass ionomer cement or acid etch composite resin.

MOD cavity preparations in 64 endodontically treated premolars were restored using four different methods. Copper rings were filled with commercial hard-setting cement and the teeth were placed into the cement up to the level of the cementoenamel junction. The teeth were grouped according to restorative method, mounted in an Instrom T.T. 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. All teeth fractured in a similar manner irrespective of the restorative method used. The resistance to fracture of the teeth was the same when they were restored with glass ionomer cement as a base over which an amalgam or composite resin was placed or with acid-etched resin. When the entire cavities were filled with glass ionomer cement the resistance to fracture of the teeth decreased significantly compared with the acid etch resin technique.