Resistance to fracture of restored endodontically treated premolars

Endodontically treated premolars were restored using 5 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 cemento‐enamel junction. The teeth were grouped according to restorative method, mounted in an Instron TT 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 increased significantly when MOD cavities in the teeth were acid etched prior to the restoration with a composite resin. The use of a bonding agent after acid etching did not further increase the resistance to fracture of the premolars restored with a resin. The acid etch composite resin technique was as effective in preventing fractures of the teeth when 2 mm of the resin was removed and replaced with an amalgam as when the entire cavities were filled with the resin material.