In vitro evaluation of different matrix metalloproteinase enzyme inhibitors usage effects on the bond strength obtained in universal bonding applications

The aim of this study is to evaluate the effects of using different Matrix Metalloproteinase (MMP) enzyme inhibitors on the microtensile bond strength of adhesive systems applied in etch and rinse mode in both short and long term. In this in vitro study, 63 caries-free, sound third molar human teeth were used. The teeth were randomly divided into three groups according to the adhesive system to be used (Adper Single Bond 2-ASB2, G-Premio Bond Universal-GPB, G2-Bond Universal-G2B). The created groups were further divided into three subgroups: control group and two MMP inhibitor groups (CHX and PA). Standardized flat dentin surfaces were prepared, and MMP enzyme inhibitors were applied for 60 seconds after acid etching, followed by the application of adhesive systems in etch and rinse mode according to the manufacturer's instructions. Control groups were prepared in the same way without MMP enzyme inhibitor application. Subsequently, composite restorations were completed, and 1 mm2 composite resin-dentin sticks were obtained for microtensile bond strength (μTBS) testing. The sticks obtained from each tooth were divided into two groups for evaluation: half were stored in distilled water for 24 hours, and the other half were subjected to 10,000 thermocycles before evaluation. The prepared sticks were evaluated for μTBS. Statistically significant differences were observed in the mean bond strength between adhesive systems used without any MMP enzyme inhibitor in both short and long-term evaluations (p<0.05). In evaluations conducted after 24 hours of water storage, the microtensile bond strength values in the groups where CHX was applied were higher than those in the control groups, and this result was statistically significant for all adhesives used except ASB2 adhesive. In evaluations conducted after 24 hours of water storage, no statistically significant difference was observed in the microtensile bond strength values in the groups where PA was applied compared to the control groups (p>0.05). In evaluations conducted after 10,000 thermocycles of aging, the microtensile bond strength values in the groups where CHX was applied were significantly higher than those in the control groups (p<0.05). Similarly, in evaluations conducted after 10,000 thermocycles of aging, the microtensile bond strength values in the groups where PA was applied were significantly higher than those in the control groups (p<0.05). Both CHX and PA applied groups showed a decrease in bond strength over time. However, this decrease was not as dramatic as in the control groups. As a result of this study, when comparing the bond strengths of the adhesives used, G2B˃GPB˃ASB2 were found respectively. It was observed that the decrease in microtensile bond strength over time in adhesive systems applied in etch and rinse mode could be reduced with MMP inhibitors. While PA did not affect the bond strength in short-term evaluations, it was found that CHX increased it. The discoloration caused by PA was not considered suitable for clinical practice. Keywords: MMP Enzyme Inhibitors, Chlorhexidine, Proanthocyanidin, Universal Adhesives, Etch and Rinse Adhesives, Microtensile Bond Strength Test.