Influence of substances with acid pH on composite resins microhardness

Resin composites are aesthetic restorative materials widely used in Dentistry and changes in pH can promote amendments in composite surface, compromising their initial characteristics. The aim of this study was to evaluate, in vitro, the effect of low pH beverages on two commercially available materials, the composite resins ICE (SDI) and Durafill VS (Heraeus Kulzer). The materials were evaluated for surface microhardness obtained by Vickers microhardness testing. Fifteen samples were prepared with 11 mm diameter and 2 mm thick, each restorative material. The samples were kept in storage conditions of the following substances: Gatorade ® (pH 2,9); Coca- Cola ® (pH 2,2) and distilled water (pH 6,0; control group) under temperature of 37 ° C, and the environment of immersing exchanged every 24 hours. Five samples of each material were immersed in the beverages tested and monitored for periods of 24 hours, 7, 14 and 21 days. The results were submitted to multifactorial analysis of variance and Tukey test. There were statistically significant differences (p 0.05) for factors environment, material and time, and for the interaction between them. The distilled water resulted in higher values of microhardness, followed by Coca-Cola® and Gatorade®. The highest values of microhardness were obtained at baseline, followed by 7, 14 and 21 days. There was no statistically significant difference (p 0,05) between the times of 14 and 21 days. It was concluded that the nanocomposite better results and that the acidic pH associated with progressive immersion time significantly alter the microhardness of the composites evaluated