Influence of etching and application of adesive system in activation of gelatinase MMP-2 in dentin and the respective inhibitory effect chlorhexidine

• Grant number: 12/25423-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: May 01, 2013
• End date: December 31, 2013
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Carlos Eduardo Francci
• Grantee: Miname Araújo Rodrigues
• Host Institution: Faculdade de Odontologia (FO). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The emergence of adhesive systems revolutionized the dental practice offering new alternatives for restorative treatment. Adhesion in enamel is a process with proven effectiveness, but the process of adhesion in dentin is less predictable due to the presence of large amounts of organic matrix and to the intrinsic moisture in this tissue. Adhesive systems with hydrophilic characteristics were developed with the purpose of favoring the infiltration of monomers into the dentin tissue, however, still observed the degradation of the adhesive interface over time. Besides the hydrolytic degradation of the resin portion, we know that the organic constituents of the hybrid layer, especially the collagen undergo degradation due to the enzymatic activity of matrix metalloproteinases (MMPs) and other proteases present in the dentin matrix. The MMPs act during the formation of dentinal tissue and remain inactive after the mineralization of the substrate. However, when the pH of the environment considerably decreases, as occurs in the dentin surface conditioning performed during the bonding procedures, MMPs are exposed and activated, and thus act degrading the collagen which by chance has remained exposed in the hybrid layer formed. The etching of dental tissues performed with phosphoric acid (30-37%), besides exposing MMPs may denature them, due to its high acidity. Moreover, the acidic character of adhesive systems currently available can also induce activation of MMPs in dentin. It is imagined that although happen denaturation of part of MMPs is exposed by demineralization of dentin tissue, other metalloproteinases would be activated in the presence of adhesive systems. One of the techniques proposed to prevent the activation of MMPs, is the application of a solution of chlorhexidine on dentin after acid etching, due to its inhibitory effect on the enzymatic activity of MMPs. The purpose of this study is to evaluate the enzymatic activity of MMP-2 in different stages of the adhesive procedure and check the inhibitory effect of chlorhexidine in every step, by using zymograms and quantifying the content of collagen solubilized by the method of determining hydroxyproline after conditioning the dentin tissue with 37% phosphoric acid and after application of an adhesive system, etch-and-rinse simplified. (AU)