The aim of this research is to evaluate the influence of dentin substrate (sound or carious) and the chorhexidine in marginal adaptation of composite resin restorations. Twelve third permanent molars without being erupted will be selected. The removal of the oclusal third will be realized to obtain flat dentin surfaces. Four cavities will be done in each teeth together with samples impermeabilization and restorations will be realized on sound (n=10) or carious (n=10) dentin. The cavities will be restored immediately in the control groups (sound dentin) following this routine: A: one bottle adhesive system + composite resin; B: self etching adhesive system + composite resin; C: chorhexidine 2% application + one bottle adhesive system; D: chlorhexidine 2% application + self etching adhesive system + composite resin. In the experimental group (carious dentin), dentin carious will be perfomed with a S. mutans strain and the cavities will be restored like the ones in the control group. All the specimens will be immersed in methilene blue solution 0.5% at 37°C during four hours and the teeth will be cut in the centre of restorations in order to evaluated the microleakage. To evaluated the calibration among the examiners, an intraclass correlation test will be promoted. Three examiners means evaluations will be submitted to Kruskal-Wallis test.
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