The Effect of two Different Enamel Bleaching Techniques on the Bond Strength of Orthodontic Brackets (An In-Vitro Study)

Abstract

This study aimed at evaluating the effect of two different enamel bleaching techniques i.e., In-office and At-home bleaching techniques on the shear bond strength of stainless steel orthodontic brackets bonded to enamel surface. Through this study sixty upper human premolars extracted for orthodontic purposes were used. They were randomly divided into three equal groups and stored in distilled water. One group served as a control group where no bleaching procedures were done while the other two groups received two different bleaching techniques i.e., In-office technique and At-home technique. Each group was further subdivided into two subgroups to evaluate the effect of the bleaching procedures on enamel structure and the bond strength of orthodontic brackets. Twenty four hours after bleaching, premolar brackets were bonded to the buccal surfaces of the premolars using the light cured adhesive system. Three different tests were applied to the bonded premolars in all subgroups i.e., Shear bond strength testing, Adhesive Remnant Assessment and resin tags evaluation using scanning electron microscope. In addition, unbonded bleached enamel sections were examined using Scanning Electron Microscope to evaluate the effect of bleaching on enamel structure. Results showed a significant decrease in the shear bond strength of the bleached subgroups. A significant difference also existed between the two bleached subgroups. Also, the bleached subgroups showed the least ARI scores. The bleaching procedures affected the enamel structure and decreased the size of resin tags and their penetration.