In vitro study of the effect of sodium hypochlorite and type of bonding on the shear bond strength of the composite to the bovine dentin

In vitro study of  the effect of sodium hypochlorite and type of bonding on the shear bond strength of  the composite to the bovine dentinDr. Kermanshah, H.* - Dr. Ghanbaripour H.** *Assistant Professor of Operative Dentistry Dept., Faculty of Dentistry, Tehran University / Medical Sciences. **Dentist. Abstract Background & Aim: Recent studies have reported the increase in bonding stability when collagen was removed from the dentin surfaces. This study was designed to investigate the effect of collagen removal on the shear bond strength of three single bond dentin bonding systems with structural differences. Materials & Methods: This laboratory experiment was performed on 100 intact bovine incisors. Smooth surfaces of dentin on the buccal aspects of teeth were prepared. The samples were then classified, according to dentin conditioning and bonding types, into 4 main groups A) The use of 3 adhesive systems, P&B NT, SB, and PLP, with no dentin treatment by sodium hypochlorite solution (control group). B) The use of adhesive system P&B NT with dentine treatment by sodium hypochlorite solution for 1 min, before, after and without etching. C) The use of adhesive system SB with dentine treatment by sodium hypochlorite solution for 1 min before, after and without etching. D) The use of adhesive system PLP with dentine treatment by sodium hypochlorite solution for 1 min before bonding system. A cylinder of Z100 (3M) dental composite with a 2-mm diameter and 3-mm height was placed on the adhesive covered dentin surface of all groups and light-cured (900 mW/cm2, for 40 sec).The specimens were kept in distilled water at room temperature for one week and then thermo cycled for 500 times (5-556). Shear bond strength of specimens was measured using a Zwick testing machine with cross-head speed of 0.5 mm/min and chisel from shearing blade. Data were analyzed by Two Way ANOVA, Tukey HSD and Dunnet T3 tests with P-value < 0.05 as the limit of significance. Results: 1) Bonding type, dentin conditioning and their combined effects had statistically significant effects on the shear bond strength (P<0.05). 2) The mean shear bond strength values were not the same in the PLP and P&B NT groups and were found to be higher in the PLP group (17.41±2.96mpa-12.77±1.51mpa). 3) In the P&B NT group, there were statistically significant differences in the mean shear bond strength among different dentin conditioning methods in all binary comparisons (except between control-H1). 4) In the SB group, there were statistically significant differences in the mean comparisons (except between control-H1 and H1-H2). 5) In the PLP group, statistically significant differences in the control-H1 groups in the mean shear bond strength values were found. Conclusion: Collagen removal from dentin surface caused a significant decrease in shear bond strength of alcohol, water and acetone-based bonding systems except when hypochlorite was used before etching in the acetone-based bonding system. Key words: Dentin bonding agents - Shear bond strength – Collagen - Hypochlorite Corresponding Author: Operative Dentistry Dept., Faculty of Dentistry, Tehran University / Medical Sciences. e.mail: kermanshah [email protected]