Evaluation of the effect of citric and benzoic acids on the enamel morphology and wear resistance

Abstract

Dental erosion leads to dental tissue loss resulting in masticatory, phonetic and aesthetic problems. This work aims to evaluate the influence of benzoic and citric acid on enamel morphology and wear. Human enamel samples were prepared and exposed to acids with the same pH (3.2) using conditions that mimic food ingestion. Enamel morphology was analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM) before and after acids exposure. Vickers hardness tests were performed, and wear resistance was accessed using a nanotribometer with a reciprocating pin-on-plate configuration. The results show that the benzoic acid attacks more uniformly the surface, while citric acid attacks mainly the inter-rod area. Also, after exposure, a decrease of enamel hardness was observed, being the lowest value obtained for benzoic acid. A dramatic decrease on enamel wear resistance was observed, being the highest decrease observed for citric acid. The differences in wear resistance were attributed to the morphology of the samples' attacked surfaces.