EFFECT OF DISINFECTANTS ON THE BOND STRENGTH OF COMPOSITE TO DENTIN

Purpose: To investigate the effect of two cavity disinfectants, a 2% c hlorhexidine (Bisco) and a 0.11% iodine/potassium-iodide/copper sulfat e solution (ORA-5), on the shear bond strength of composite to dentin mediated by the dentin bonding agents (DBA), Syntac and Tenure. Materi als and Methods: The occlusal surfaces of 72 non-carious extracted hum an molar teeth were flattened to dentin using 500 grit sandpaper. They were randomly assigned (n=12) to three groups within each DBA system: Bisco/Tenure, ORA-5/Tenure, Tenure, Bisco/Syntac, ORA-5/Syntac and Sy ntac. Dentin disinfectants were applied for 20 seconds and dried. DBA was applied following manufacturer's instructions. A hybrid resin comp osite (Tetric) was then bonded to all treated samples. The samples wer e thermocycled and tested in shear until failure. Fracture analysis wa s performed on dentin surfaces with both light and scanning electron m icroscopy. Shear bond strength data was analyzed using ANOVA, Student- Neuman-Keuls and Dunnett tests at P< 0.05. Results: Shear bond values (Mean +/- SD, MPa) were: Syntac control 14.3+/-2.0, Bisco/Syntac 8.1+/ -4.9 and ORA-5/Syntac 5.7+/-5.1; Tenure control 15.0+/-1.9, Bisco/Tenu re 14.2+/-3.0 and ORA-5/Tenure 13.9+/-3.7. The only significant differ ence found between disinfectant treatment groups and the control group s was with Syntac. Fracture surface analysis revealed that with Tenure most failures were cohesive in resin but with Syntac, the disinfected samples displayed adhesive failures.