Effect of primer application time on shear bond strength of orthodontic bracket with no-mix composite

Abstract

Achieving desirable bond strength in orthodontics is important; because bracket replacement is time-consuming and costly. Bond failure is related to different factors such as : etching procedure, primer application mode and forces of masticatory system. Aim: The aim of this study was to evaluate the influence of primer application time on shear bond strength of orthodontic brackets with no-mix composite. Materials and Methods: A hundred of sound bovine lower incisors were selected and after removing soft tissue, eath tooth was embedded in an acrylic resin on a mounting jig , where the tooth's facial surface was oriented in a way that it was prependicular to the floor of the jig. The samples were divided in to 4 groups. In the first group bracket bonding was done immediately after application of primer and in groups 2, 3 and 4 was carried out 5,15 and 30 minutes after it. Subsequently, termocycling was carried out and Universal Testing Machine was applied for debonding and measuring of shear bond strength. The final step was evaluation of ARI (Adhesive Remanant Index) under a stereomicroscope. Results: Statistical analyses of ANOVA and Tukey (for SBS) and Chi-square( for ARI) showed that: 1.The differences in SBS between the groups were statistically significant (P=0.001). 2.There were significant differences in SBS between groups one and two (P=0.011) and groups two and four (P=0.002). 3.Evaluation of ARI showed significant differences between the groups (P=0.032). Conclusions:Primer application time affected the SBS and ARI.