Effect of the prism-interprisms three-dimension spatial microstructure on the enamel bond strength

The prism-interprisms level of the enamel hierarchical microstructure is the largest degree of structural variation and most sophisticated structural adaptation. We studied the effect of the prism-interprisms three-dimension spatial microstructure on the enamel bond strength. We prepared 11 groups of enamel segments: longitudinally sectioned segments with or without a 45-degree bevel (group = 2), horizontally sectioned segments with or without a 45-degree bevel of three regions (the incisal, middle, and cervical) (group = 6), and tangential (labial) sectioned segments of three regions (the incisal, middle, and cervical) (group = 3). The finished surface of each segment was observed by scanning electric microscopy (SEM) before treatment with four self-etch adhesive systems and applied with four corresponding composite resins. Resin-bonded enamel samples were prepared in beams for microtensile bond strength (MTBS) tests. The results were analyzed with a three-way ANOVA followed by Tukey's post-hoc HSD multiple comparisons procedure. SEM observations revealed complex arrangements of prisms and interprisms. MTBS measurement showed that the longitudinally sectioned group had the lowest value, without significant differences between the groups with or without 45-degree bevel. Combining SEM observations and MTBS measurements, the prism-interprisms microstructure varied with the incisor regions, and different prism-interprisms microstructures allowed diverse sectioned surfaces, which could affect the enamel bonding.