Influência da concentração de clorexidina em relação ao tempo e meio de armazenagem na resistência de união de sistemas adesivos

Abstract

Significant technological advances in dental materials and chemicals have occurred in recent decades, contributing to increased longevity of adhesive restorations. The aim of this study was to evaluate the influence of the chlorhexidine concentration, time and storage condition on the microtensile bond strength of adhesive systems. The study was conducted in two stages; for the first analysis of this study, thirty noncarious human molars were sectioned to expose middle-coronal dentin, which was etched with 37% phosphoric acid. Specimens were randomly assigned to the following treatments with chlorhexidine digluconate (CHX) (n=10): group C (control), not treatment was done; group 0.12Chx, aqueous solutions of 0.12% Chx; group 2CHX, aqueous solutions of 2% CHX. Each group was subdivided in accordance with adhesive systems (n=5): SC, Adper Scothbond Multi-Purpose; and XP, XP Bond. All were restored with resin composite Filtek Z350 XT. Resin-dentin sticks with cross-sectional area approximately of ±1.0mm2 were submitted to microtensile bond strength (μTBS) test immediately (T0) and after 4 months of storage in artificial saliva (T4). For the second analysis this study, a flat middle dentin surface was prepared on 15 extracted human molars and was etched with 37% phosphoric acid. Specimens were randomly divided according to the treatments with CHX (n=10): Np, no pretreatment; 0.12CHX, aqueous solutions of 0.12% CHX; 2CHX, aqueous solutions of 2% CHX. All specimens were bonded with Adper Scothbond Multi-Purpose and restored with resin composite Filtek Z350 XT. Resin-dentin sticks with cross-sectional area of approximately ±1.0mm2 were submitted to microtensile bond strength test immediately (T0) and after 4 months of storage (T4) in mineral oil. The results of this second analysis were compared with the results of the groups that used the Adper Scothbond Multi- Purpose adhesive system of the first evaluation. The data were submitted to statistical analysis by 3-way analysis of variance (ANOVA) and the Tukey Honestly Significant Difference (HSD) test (α=.05). Results of first evaluation showed statistically significant differences on bond strength values to aging factor (p<.001) and adhesive factor (p<.001). The failure mode was analyzed by Fisher s Exact Test, which demonstrated significant differences within the groups; prevalence of mixed in T0 and adhesive failure after aging to SC groups, except the groups treated with 2% CHX; and XP groups had a prevalence of adhesive failures at T0 and mixed failures in T4, except the groups treated with 2% chlorhexidine. For the second evaluation, was found statistically significant differences between the bond strength of storage media (p < .001) and between aging versus the storage media (p<.001). Fisher s Exact Test demonstrated significant differences between the failure mode within the groups; prevalence of mixed and adhesive failure. Therefore, the use of chlorhexidine did not influenced the bond strength values of the adhesive systems tested, however of 2% CHX showed influence in the dental structure. Differences in adhesives systems were detected, which 3-step etch-and-rinse adhesive presented higher bond strength values than 2-step etch-and-rinse adhesive; and after 4 months of aging, the bond strength values were lower, regardless of the adhesive system tested. Specimens stored in artificial saliva long-term showed interface degradation by hydrolysis and reduction on bond strength, unobserved characteristics in mineral oil storage.