Efficacy of four preventive measures against enamel demineralization at the bracket periphery-comparison of microhardness and confocal laser microscopy analysis

The aim of this in-vitro study was to investigate the efficacy of four preventive measures against enamel demineralization and to compare the suitability of microhardness (MH) measurements and confocal laser microscopy (CLSM). A total of 80 teeth were randomly allocated into four groups. The effect against demineralization of two coating materials (group 1: resin-modified glass ionomer (RMGI) cement varnish (ClinproXT); group 2: composite sealant (ProSeal)) and that of two types of bracket-bonding material (group 3: amorphous calcium phosphate (ACP) composite (AegisOrtho); group 4: RMGI (FujiOrthoLC)) was compared after pH-cycling by MH and CLSM. Measurements were made at the edge of the coating/bracket as well as at 50, 100, 200, and 400 mu m distance. The data were converted into values of mineralization (Vol%) and analyzed by parametric (ANOVA and Tukey's post hoc) or non-parametric (Kruskal-Wallis and Games-Howell post hoc) tests. ClinproXT and ProSeal were proved to protect the bracket periphery. However, the area next to them showed demineralizations. The mean area of lesion (CLSM-data) was significantly different between the groups (p < 0.0001). The smallest lesions were revealed for the RMGI-based materials. MH identified only for group 4 a significant difference between the area next to the bracket base and that at 200 and 400 A mu m distance. There was nearly no lesion under both coatings. A stagnation of demineralization was identified particularly for the RMGI. ProSeal showed an inferior protection of the untreated enamel. MH and CLSM analysis were suitable to detect subsurface lesions. A diverse efficacy of materials against enamel demineralization at bracket periphery has to be noticed.