Effect of Chlorhexidine Application Methods on Microtensile Bond Strength to Dentin in Class I Cavities

Objective: To evaluate the influence of chlorhexidine with different application methods on the microtensile bond strength (mu TBS) to dentin in Class I cavities. Methods: Flat dentinal surfaces with Class I cavities (4 mm long, 4 mm wide, 2 mm deep) in 50 molars were bonded with Adper Single Bond 2 etch-and-rinse adhesive system after: 1) Chlorhexidine (CBX) + rinsing + etching; 2) CBX + no rinsing + etching; 3) Etching + CBX + rinsing; 4) Etching + CHX + no rinsing; 5) Etching only as a control group. Resin composite buildups were constructed with Z-350 (3M ESPE) using a bulk method and they were polymerized for 40 seconds. For each condition, half of the specimens were immediately submitted to microtensile bond strength and half of the same group was submitted to 10,000 cycles of thermocycling between 5 degrees C and 55 degrees C before testing. The data were analyzed using the two-way ANOVA and Student t-test at a 95% significance level. Results: Chlorhexidine pretreatment did not affect the bond strength of specimens tested at the immediate testing period, regardless of the application method used, compared to the control group. However, after 10,000 thermocycles, a significant bond strength reduction was found in the control group. In general, the chlorhexidine application method did not demonstrate a significant difference among the groups treated with chlorhexidine. However, there was a significant difference after thermocycling in the groups treated with chlorhexidine before etching and no significant difference in the groups treated with chlorhexidine after etching. Conclusion: Considering the amount of reduction in bond strength after thermocycling, the current study showed improved dentin bond strength with chlorhexidine when used after etching.