Incorporation of epigallocatechin gallate in etch-and-rinse adhesive system and its effect on flexural strength and bond durability to caries-affected dentin

Abstract

The present in vitro study aims to evaluate the incorporation of epigallocatechin gallate (EGCG), a metalloproteinase-MMP inhibitor, in etch-and-rinse adhesive system and its effect on flexural resistance (FR) and bond durability to caries-affected dentin, by means of microtensile bond strength testing (MBS). For MBS, forty dentin slabs will be submitted to a microbiological caries model to induce caries formation. After infected caries removal, caries affected dentin surface will be acid conditioned (37% phosphoric acid) for 15 seconds and randomly divided into four groups according to the application mode of the MMP-inhibitory solution on dentin surface (n=10): EGCG-PRE - EGCG solution (200¼g/mL) applied before adhesive system (as a pre-treatment); EGCG-INC - EGCG solution incorporated to the etch-and-rinse adhesive system at a ratio of 200¼g/mL; CLX-PRE - 2% chlorhexidine digluconate solution applied before adhesive system (as a pre-treatment) (positive control); NT - Any treatment will be performed (negative control). Adhesive system will be applied according to manufacture's instruction and composite restorative will be placed on dentin surface. Dentin-resin blocks will be sectioned into 8 beam-shaped specimens (0.8mm2 area) that will be allocated into two groups, according to the moment of microtensile bond strength evaluation: 24 hours or after a 6-months period of water storage. For FR analysis, bar-shaped specimens (7mm x 2mm x 1mm - length x width x thickness) will be obtained with the two-step adhesive system, containing or not the EGCG solution (200¼g/mL). Both MBS and FR tests will be performed in a universal testing machine, operating at a 0.5 mm/min speed. Data will be statistically analyzed considering its distribution. If there is normality of errors distribution and homogeneity of variance, parametric tests will be applied; on the contrary, non-parametric testes will be adopted, both with 5% significance level.