[Evaluation of shear bond strength of metal brackets to enamel after application of primers over bracket base: an in vitro study]

ABSTRACT

The aim of this study was to evaluate the effect of application of two types of primers over bracket bases on the shear bond strength [SBS] and mode of bond failure. In this study, 75 human premolar teeth were divided into three equal groups. In group 1 [control], after surface preparation of enamel by conventional method [acid etching+primer] brackets were bonded with Transbond XT composite. In group 2 [TX], brackets were bonded to enamel same as the first group but Transbond XT primer were used on bracket bases before placement of composite. In group 3 [PL], Transbond plus primer was applied on bracket bases before placement of composite. After 24 h, the SBS test was performed by universal testing machine at crosshead speed of 0.5 mm/min. Then, adhesive remnant index [ARI] scores and percentage of cohesive fracture were determined using stereomicroscopy. SBS data were analyzed by one-way ANOVA and Duncan tests. Kruskal-Wallis and Mann-Whitney tests were used to analyze ARI and cohesive fracture results. There was significant difference in SBS values among the groups [P<0.001]. The highest SBS was shown in TX group and the lowest was seen in PL group. There was no significant difference between control and TX groups in ARI scores [P=0.199]. No significant difference was found in cohesive fracture values between the groups [P=0.093]. Both the control and TX groups showed significant difference in ARI scores and cohesive fracture compared with the PL group in all of the comparisons [P<0.001]. Application of Transbond XT primer over bracket base affects the bond strength and failure mode. Transbond XT primer increased the bond strength but Transbond plus primer decreased it