Comparison of the effect of two MMP inhibitors on microtensile bond strength to dentin in class I cavities

Aim: To compare the effects of pretreatment with doxycycline and chlorhexidine on microtensile bond strength to dentin in class I cavities restored with composite resin. Materials and Methods: Class I cavities were prepared on the occlusal surface of 30 freshly-extracted caries-free molars. In group 1, 2% chlorhexidine was applied to the acid etched surface, placed in contact for 20 seconds, and gently air dried without rinsing. In group 2, 2% doxycycline was applied to the acid etched surface, placed in contact for 20 seconds, and gently air dried without rinsing. In group 3, the control group, just the conventional bonding procedure was used without any pre-treatment. The cavities were restored with resin composite using a bulk method. After thermocycling, the specimens were serially sectioned to obtain resin dentin sticks with a rectangular cross-sectional area of approximately 1mm2 using microtome. The microtensile bond strength values were tested using Universal testing machine at crosshead speed of 0.5 mm/min until failure. The results obtained were analyzed by One-way ANOVA and Tukey's HSD tests for statistical significance. Results: The pre-treatment with chlorhexidine and doxycycline showed a significant effect in preserving the in vitro bond strength, when compared to the control group (p=0.000). Among the test groups, the chlorhexidine treatment resulted in a higher bond strength value than doxycycline group (p=0.000). Conclusion: Pre-treatment with MMP inhibitors resulted in higher bond strength values. Chlorhexidine group showed a significantly higher bond strength value compared to the Doxycycline group.