Introduction:Composite resins are widely used in dentistry because of the great demand for aesthetic restoration. In addition, it is a less expensive alternative to indirect restorative treatment. With time, however, composite resin restoration can show wear, discoloration, fractures, or defects which may require their replacement.Total replacement of the restoration can cause significant loss of sound dental tissues and consequently weaken dental structure and cause pulpal injuries.The repair is a conservative process, so that there is no need for removing entire restoration and the minimum cavity preparation is required.The aim of the study is to evaluate influence of various surface treatment on shear bond strength of repaired composites and its mode of failures