In situ effect of enamel salivary exposure time and type of intraoral appliance before an erosive challenge.

OBJECTIVES: This study tested the effect of enamel salivary exposure time prior to an acid challenge (30 min, 1, 2, or 12 h) and type of intraoral appliance (palatal or mandibular) on initial erosion. METHODS: After initial surface hardness evaluation, enamel blocks (n = 340) were randomly divided into groups and volunteers (n = 20). The control group was not exposed to saliva previously to the erosive challenge. The volunteers wore palatal and mandibular appliances simultaneously. After salivary exposure, the blocks were subjected to acid exposure by immersion in hydrochloric acid (0.01 M, pH 2.3) for 30 s. Then, the enamel surface hardness was evaluated. Data were analyzed using ANOVA, Kruskal-Wallis and Tukey's test (p < 0.05). RESULTS: No difference was observed on percent surface hardness change (% SHC) in the enamel blocks between the types of intraoral appliances. Exposure to saliva for 30 min and 1 h promoted similar enamel resistance to the erosive attack, which was similar to the control group for both appliances. Blocks exposed to saliva for 2 h showed less hardness loss when compared to 30 min. Keeping the blocks in saliva during 12-h overnight resulted in similar percentage of enamel hardness loss compared to 2 h. CONCLUSIONS: A 2-hour in situ exposure to saliva is adequate to promote partial protection against initial erosive lesions, independently of the type of intraoral appliance used. CLINICAL SIGNIFICANCE: This finding will help researchers in the development of erosion studies, which will provide information for dentists to offer a better treatment for erosion.