Efeito da doxiciclina na resistência de união à dentina de um sistema adesivo etch-and-rinse

Abstract

This study evaluated as overall purpose the influence of doxycycline used as a matrix metalloproteinase (MMPs) inhibitor on the microtensile bond strength (μTBS) of a total etching adhesive system to dentin, considering two formulations (different pHs) and two substrates (source and demineralized) of primary and permanent teeth. The study is divided into two articles, the aim of the first article was to evaluate the application s effect of acidic or neutral doxycycline on the μTBS to dentin. Twenty extracted noncarious third molars were divided into 4 groups (doxycycline acidic pH, doxycycline neutral pH, chlorhexidine and control - no treatment). A flat dentin surface was exposed, wet grinding and submitted to: acid etch, application of the substance corresponding treatment group, application of adhesive system and resin composite. The specimens were stored (24 h in distilled water) and sectioned to obtain sticks (cross-sectional area of approximately 0.9 mm2). The sticks were submitted to tensile test. The mean μTBS were submitted to a one-way ANOVA and Tukey s test (α = 0.05). No significant difference of immediate μTBS (MPa) was observed between the neutral and acidic doxycycline, furthermore the solutions of different pH values were statistically similar to control and chlorhexidine groups. For the second study 30 permanent molars and 30 second primary molars were divided into 12 experimental groups (n = 5) according to the surface treatment after etching: doxycycline, chlorhexidine and control, and the condition substrate: sound and demineralized (pH cycling). The specimens preparation, restorative procedures and tensile test were performed in the same way as in the previous study. The μTBS were subjected to a two-way ANOVA and Tukey's test (α = 0.05), considering separately primary and permanent teeth. For both teeth types the application of doxycycline did not affect the immediate μTBS, while the demineralized substrate values were statistically lower than the sound group. The doxycycline solution, even at acidic pH, does not seem to affect the immediate bond strength to dentin, while demineralized substrate needs attention by presenting μTBS immediately reduced compared to sound.