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Leo Sauli Tjaderhane | Institute of Dentistry/University of Helsinki - Finlândia

Grant number: 05/01246-7
Support type:Research Grants - Visiting Researcher Grant - International
Duration: November 20, 2005 - December 24, 2005
Field of knowledge:Health Sciences - Dentistry
Principal Investigator:Mario Fernando de Goes
Grantee:Mario Fernando de Goes
Visiting researcher: Leo Sauli Tjaderhane
Visiting researcher institution: University of Helsinki, Finland
Home Institution: Faculdade de Odontologia de Piracicaba (FOP). Universidade Estadual de Campinas (UNICAMP). Piracicaba , SP, Brazil

Abstract

The durability of resin-dentin bonds is controversial. In vitro and in vivo studies indicate that bond strengths gradually fall over time. Examination of hybrid layers in vivo or in vitro revealed a loss of collagen fibrils from resin-bonded dentin. Although previous studies suggested that resins were hydrolytically unstable, the latter observations indicated that the same applied to collagen matrix. Recent study demonstrated hydrolytic activity against mineralized dentin collagen, inhibited by protease inhibitors. It was speculated that endogenous metalloproteinases (MMPs) present in dentin-pulp complex are responsible for the slow destruction of the dentin matrix. Current knowledge indicates that collagenolytic activity of dentin powder may have been due to MMP-8 (collagenase-2) synthesized by mature odontoblasts and present in demineralized human dentin carious lesions, while gelatinolytic activity was due to MMP-2. Also in the mineralized dentin hundreds of micrometers beneath the hybrid layer, a lack of cross-banding has been observed. It is logical to speculate that matrix-bound MMPs may be involved in this process.Since dentin collagen is needed for the adhesion of composite fillings in dentin, this MMP-dependent degradation may be significant in terms of loss of dentin bonding with time. This new insight justifies the research examining the possibility of incorporation of MMP inhibitors into operative and endodontic procedures to prevent the potential detrimental effects of endogenous MMPs in dentin. In a recent study, we found evidences that chlorhexidine (CHX), which is known to non-selectively inhibit MMPs, may reduce the rate of resin-dentin bonds degrdadation. In the present study, the same procedure will be followed to examine the effect of another potent non-selective MMP inhibitor, chemically modified tetracycline 3 (CMT-3: CollaGenex Pharmaceuticals, Inc. Newtown, PA, USA). Based on the previous findings, the hypothesis is set that using CMT-3 will not affect the immediate bonding strength, but the time-dependent decrease will be lower in CMT-3-treated samples, with statistically significant differences observed after 6 months and 1 year. (AU)