Effect of disinfectants on the bond strength of composite to dentin

To investigate the effect of two cavity disinfectants, a 2% chlorhexidine (Bisco) and a 0.11% iodine/potassium-iodide/copper sulfate solution (ORA-5), on the shear bond strength of composite to dentin mediated by the dentin bonding agents (DBA), Syntac and Tenure.

The occlusal surfaces of 72 noncarious extracted human 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 Syntac. Dentin disinfectants were applied for 20 seconds and dried. DBA was applied following manufacturer's instructions. A hybrid resin composite (Tetric) was then bonded to all treated samples. The samples were thermocycled and tested in shear until failure. Fracture analysis was performed on dentin surfaces with both light and scanning electron microscopy. Shear bond strength data was analyzed using ANOVA, Student-Neuman-Keuls and Dunnett tests at P < 0.05.

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/Tenure 14.2 +/- 3.0 and ORA-5/Tenure 13.9 +/- 3.7. The only significant difference found between disinfectant treatment groups and the control groups 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.