Effect of Office Bleaching Agents on the Shear Bond Strength of Metallic Brackets Bonded Using Self-Etching Primer System at Different Time Intervals – An In-Vitro Study

Abstract

A common method of treating discoloured teeth is to bleach them using hydrogen peroxide. Many studies in the literature have concluded that bleaching reduces shear bond  strength of composite resin significantly and thus, to achieve clinically adequate shear bond strength of composite for bonding brackets to bleached enamel, it is important to find out the various methods of reducing adverse effects of bleaching. It has been proposed by some authors that a delay in bonding effectively reverses the effects of  bleaching on bond strength. OBJECTIVES- To test the null hypothesis that there is no statistical significance in (1) bond strength and (2) failure site location with bleached and unbleached enamel prepared with TransbondPlus Self-etching Primer between  different time intervals. MATERIALS AND METHODS- Sixty freshly extracted human premolar teeth were randomly divided divided into three groups of 20 teeth each Bleaching treatment was performed at two different time intervals (bleaching immediately before bonding and bleaching 30 days before bonding). All brackets were bonded with a self-etching primer system. The shear bond strength of these brackets was measured and recorded in MPa. Adhesive remnant index (ARI) scores were determined after the brackets failed. RESULTS- The mean shear bond strength of Group A (control) is found to be 20.4315 MPa (SD± 6.81041) which was reduced to 11.1955 MPa (SD ± 4.58041) when bonding was done immediately after bleaching (group B). The shear bond strength increased to 14.9910 MPa (SD ± 4.74545) when enamel was 14.9910 MPa (SD ± 4.74545) when enamel was Group C) Pair wise comparison of shear bond strength between the three groups  using Post hoc Tukey test showed that there is a very high statistically significant difference between shear bond strength of all three groups. CONCLUSION This study shows that bonding immediately after bleaching significantly reduces the shear bond strength , it can be reversed by a delay in the bonding by 30 days which shear bond strength , it can be reversed by a delay in the bonding by 30 days which improves the shear bond strength as reflected  in the results of the study ,So it is advisable to delay the orthodontic bonding procedure by an interval of 30 days to improve survival rates and prevent frequent breakages of brackets due to bond failure