Comparing the Effect of Assure Plus and Transbond XT Bonding on Shear Bond Strength and Adhesive Remnant Index in Metal Brackets Bonded to Enamel

Background and purpose: Bracket debonding is a major problem during orthodontic treatment. This research aimed at studying shear bond strength (SBS) and adhesive remnant index (ARI) in two bonding systems (Assure Plus (adhesion booster) and control). Materials and methods: In this vitro trial, premolars (n=90) were divided into two groups. The brackets were bonded either with Transbond XT or Assure Plus. After aging and thermocycling, SBS was measured by universal testing machine. ARI scores were recorded using stereomicroscope. Data were analyzed in SPSS V20 applying One-way and two-way analysis of variance, Tukey test, and Kruskal-Wallis test. Spearman correlation coefficient was calculated to determine any correlation between bond strength and ARI scores. Results: Aging had no significant effect on SBS in Assure Plus samples (P=0.252) but in Transbond XT, samples with 6 months of aging had significantly lower bond strength compared to 24 hours (P=0.001) and 3 months (P=0.000) of aging. There were no significant differences between Transbond XT and Assure Plus when aged for 24 hours (P=0.280) or 3 months (P=0.114) but when aged for 6 months, Assur Plus had significantly higher bond strength (P=0.000). Spearman correlation test showed significant and direct relation between ARI score and SBS (r=0.834, P<0.001). Conclusion: Shear bond strength of Assure Plus was not affected by aging, so it could be useful when higher bond strength is needed for longer period of time.