An In Vitro Evaluation of Human Enamel Surfaces Subjected to Erosive Challenge After Bleaching.

OBJECTIVES: This study aimed to evaluate whether tooth enamel bleached with hydrogen peroxide (H2 O2 ) is more susceptible to erosion when compared with unbleached tooth enamel; and whether the presence of calcium (Ca) in the bleaching gel influenced this process. MATERIALS AND METHODS: Enamel blocks were prepared from human molars, and submitted to surface microhardness analysis (baseline). Blocks were prepared and randomly divided into four treatment groups (n = 20): G1 and G2-bleached with 7.5% H2 O2 , with and without Ca, respectively; G3 and G4-bleached with 35% H2 O2 , with and without Ca, respectively. After bleaching, these groups were submitted to an erosive challenge with 1% citric acid. G5 and G6 (n = 20, each) were the negative (without bleaching) and positive controls (without bleaching, but with erosion), respectively. The percentage of surface hardness loss (%SHL), the 3D non-contact profilometry and Scanning Electron Microscopy (SEM) analyses were performed. RESULTS: G2 showed the highest %SHL after bleaching. G1 presented the lowest %SHL in comparison with G2, G3, G4, and G6 after erosion (p < 0.05), which was confirmed only by the SEM analysis. CONCLUSION: It is suggested that low concentration of H2 O2 with calcium can be recommended for at-home bleaching agents, which may avoid the mineral loss of bleached enamel after an erosive challenge. CLINICAL SIGNIFICANCE: Low concentration of H2 02 with calcium can be recommended for at-home bleaching agents, which may avoid the mineral loss of bleached enamel after an erosive challenge. (J Esthet Restor Dent 29:128-136, 2017).

[The relationship between oral habits, oronasopharyngeal alterations, and malocclusion in preschool children in Vitória, Espírito Santo, Brazil]. / Relação entre hábitos bucais, alterações oronasofaringianas e mal-oclusões em pré-escolares de Vitória, Espírito Santo, Brasil.

The objective of this study was to estimate the prevalence of malocclusion and associated variables such as deleterious habits (DH) and oronasopharyngeal alterations (OA), mouth breathing, atypical phonation, and atypical swallowing in three-year-old children in Vitória, Espírito Santo State, Brazil. The sample included 291 children of both sexes enrolled in a Children's Educational Center and selected through probability sampling by conglomerates. Logistic regression indicated a high relative risk (RR) in children with altered overjet, open bite, and cross-bite to present mouth breathing (RR = 1.89; CI: 1.56-2.03), (RR = 2.46; CI: 2.00-3.02), (RR = 1.45; CI: 1.23-1.72); atypical swallowing (RR = 2.57; CI: 1.87-3.52), (RR = 3.49; CI: 2.53-4.81), (RR = 1.86; CI: 1.46-2.39); and atypical phonation (RR = 2.25; CI: 1.66-3.05), (RR = 3.18; CI: 2.38-4.25), (RR = 1.71; CI: 1.32-2.22), respectively. An association was shown between finger or pacifier sucking and altered overjet (p < 0.001), and between pacifier sucking and open bite (p < 0.001). Such results indicate that the prevalence of malocclusions is associated with DH and OA.