Effects of fluorosis on the shear bond strength of orthodontic brackets bonded with a self-etching primer

The aim of this study was to compare the shear bond strength (SBS) of brackets bonded to fluorosed and non-fluorosed teeth with self-etching primer (SEP) and phosphoric acid (PA). The study involved 40 mildly fluorosed [Thylstrup-Fejerskov (TFT) Index = 1-3] and 40 non-fluorosed human premolar teeth. The fluorosed and non-fluorosed teeth were randomly divided into two subgroups. In the first subgroup, 37 per cent PA was applied for 30 seconds and in the second, a SEP (Transbond Plus) was used. The brackets were bonded with light-cure adhesive paste (Transbond XT) and cured for 20 seconds. The SBSs were measured after 1000 thermocyclies. Two-way analysis of variance, Tukey's multiple comparison test, and Weibull analysis were used for the evaluation of SBS values. Bond failure locations were determined with the adhesive remnant index (ARI) and were compared with the Kruskal-Wallis and Mann-Whitney U-tests. The mean SBS was 9.01 MPa for the fluorosed teeth bonded with SEP. This value was significantly different from those of fluorosed teeth etched with PA (15.22 MPa) and non-fluorosed teeth conditioned with SEP (12.95 MPa) and PA (15.37 MPa). The ARI scores of the fluorosed teeth conditioned with SEP were significantly lower than those of non-fluorosed teeth conditioned with SEP or PA. The results of this in vitro study suggest that there are no differences in the SBS of orthodontic brackets between mildly fluorosed and non-fluorosed enamel etched with 37 per cent PA for 30 seconds. The SEP showed lower SBS values for orthodontic brackets bonded to mildly fluorosed enamel. The findings provide some evidence that routine clinical use of a SEP to bond brackets to mildly fluorosed teeth cannot be supported.