Evaluation of the effects of the bonding agent on acid-etched human enamel demineralization: in situ study

This in situ study evaluated the influence of the bonding agent on demineralization of acid-etched human enamel. Enamel blocks obtained from 20 human molars (four blocks per tooth) were divided into five groups. For the control groups, healthy control (HC, no treatment) and acid-etched control (EC, etching with 35 per cent phosphoric acid for 20 seconds), the specimens were obtained by sectioning in half, one block from each tooth. For the experimental groups, experimental etched group (EE), experimental Concise™ group (CE), and experimental Transbond™ group (TE), all specimens were etched with 35 per cent phosphoric acid for 20 seconds (EE) and treated with Concise™ enamel bond (CE) and Transbond™ XT primer (TE). Specimens from the experimental groups were fixed at intra-oral appliances wore by 10 volunteers and exposed to oral environment. After 28 days, the specimens were sectioned in the mesial-distal direction and the enamel cross-sectional Knoop hardness number (KHN, 50 g, 15 seconds) was measured at the cervical and occlusal regions at 25, 50, and 75 μm from the enamel surfaces. Data were analysed by analysis of variance (ANOVA) and Tukey honestly significantly different test for multiple comparisons (α = 0.05). Enamel KHN (P < 0.05) was recovered only in the Concise-treated group (CE; P < 0.05). When considering depth measurements, KHN results were 25 > 50 > 75 μm (P < 0.05). None of the groups exposed to the intra-oral environment for 28 days have recovered completely the enamel microhardness, but the order of improvement was better in the CE group than the TE group, the latter being only slightly better than the EE group.