Influence of Protease Inhibitors on Bond Degradation of Self-Etch Adhesive Systems to Caries-Affected Dentin: An in Vitro Study

Background: A decline in pH and dissolution of the inorganic content of the dental tissues are followed by exposure of the organic portion of the tooth, which, in dentin, is largely composed of collagen fibres. These unprotected fibres are then degraded by metalloproteinases and cysteine cathepsins, proteolytic enzymes present in dentin. We evaluated the influence of protease inhibitors on the bond strength of a self-etch adhesive system to caries-affected dentin. Eighty permanent third molars were selected for the study. Dentinal caries were induced artificially by the microbial method and the teeth were divided in four groups: G1—application of Clearfil SE Bond adhesive system (CL); G2—2% chlorhexidine (CLX) + CL; G3—sodium bicarbonate (BIC) + CL; G4—BI + CLX + CL. Bond strength was assessed immediately and at six months. During the six months, the specimens were stored in distilled water. Microtensile bond strength testing was performed. On immediate testing, there was no significant difference in bond strength across the control, BIC, and CLX groups. The combination of BIC + CLX, however, led to an immediate, significant reduction in bond strength. After six months, bond strength was reduced in all groups. The highest bond strength was obtained in the control group (P < 0.05). Most fractures were adhesive, both immediately and at six months. We concluded that the cavity pretreatment with 2% CLX or 2% BIC did not have an immediate negative impact on bond strength of the Clearfil SE Bond system. After specimens were stored for six months in water, their bond strength of specimens was reduced in all groups. This reduction was the greatest in the groups exposed to the inhibitors.