The effect of mechanical surface conditioning methods on the shear bond strength of repaired composites Dr. P. Alizadeh Oskuee* - Dr. N. Mohammadi* - Dr. S. Savadi Oskuee* - Dr. A. Hoseini** *- Assistant Professor of Operative Dentistry Dept. - Faculty of Dentistry – Tabriz University of Medical Sciences. **- Dentist. Background and Aim: Considering the cost and quantity of tooth loss in the process of cavity preparation, repairing composite restorations instead of replacing them would be much more efficient. The aim of this study was to evaluate and compare the effectiveness of different mechanical surface treatment methods on the shear bond strength (SBS) between old and new composites. Materials and Methods: In this experimental in vitro study, 80 cylindrical specimens were fabricated from Tetric Ceram Composite (A1, vivadent) and were preserved in 370c distilled water. They were divided into 4 groups according to the surface treatment method: control (no treatment), roughening by a diamond bur, polishing with Sof-Lex disks and air-abrasion. All specimens were thermocycled (0.5-550c, 500 cycles) prior to testing for SBS. An Instron Universal Testing Machine (5mm/min Cross head imm) was used to evaluate the SBS of the specimens. Data were analysed by one-way ANOVA and Duncan tests. Results: The highest to lowest shear bond strengths were seen in the Sof-Lex disk, air abrasion, diamond bur and control groups, respectively. A significant difference was observed between all three experimental groups (air abrasion, diamond bur, Sof-Lex disk) and the control group. There were no significant differences between the air abrasion and diamond bur groups, but the other groups revealed a significant difference when compared as pairs. Adequate wetting and induction of a microretentive surface, may explain the high SBS observed in the Sof-Lex group. Conclusion: The results of this study emphasize the importance of mechacinal surface conditioning prior to composite restoration repair. Key words: Bond strength - Surface treatment - Air abrasion - Sof-Lex disk | 
