Fracture resistance of repaired Class II composite resin restorations.

The present study investigated the fracture resistance of repaired class II composite resin restoration repaired with similar and dissimilar types of composite resins. A standardized occluso-distal cavities were prepared on lower second molar teeth. Half of the cavities were restored with microfilled composite resin, while the other half were restored with hybrid type of composite resin. All restorations were subjected to a compressive load using an instron testing machine. The load at which composite fracture for each restoration was recorded in (kg.). The fractured specimens were then repaired with similar and dissimilar composite. Concerning the repair procedure and before the application of bonding agent, the fractured surfaces were divided into four groups according to the method of treatment which were no roughening or etching, roughening only, etching only and lastly roughening and etching. All the repaired samples were again subjected to compressive load. The fracture resistance values of repaired and unrepaired restorations were recorded and statistically analysed. Results concluded that, the repair of hybrid composites resin gave in general higher fracture resistance values than microfilled composite. Roughening and etching the surface of old restoration before bonding agent application gave the highest fracture resistance values. It was also found that bonding agent alone without roughening or etching gave the lowest fracture resistance values.