A Comparative Evaluation of Shear Bond Strength of Metallic Brackets Bonded After 15 - 30, Or 60 Second Etching and Correlation Of Adhesive Remnant Index With Etch Time - An In Vitro Study.

Direct bonding of orthodontic attachments has become a clinical reality, with the application of the acid etch technique, using ortho phosphoric acid. Depth of the etch or the amount of surface enamel removed during the etching procedure depends on the concentration of the acid and the etching time. The present study was designed to evaluate the shear bond strength of metallic brackets at the various etch time of 15-30 or 60 seconds. Etching with phosphoric acid was known to produce dissolution of the outermost enamel layer and provides mechanical attachments for bonded orthodontic brackets. However, the debonding and subsequent cleanup procedure at the end of treatment may be rather time consuming. Also, care must be taken not to induce iatrogenic effects. Ideally in orthodontics a bond is said to be ideal when the bond failure occurs at the enamel composite interface because debonding and subsequent polishing of tooth would cause least damage to the enamel surface. Several recent reports have indicated that a traditional acid etching time of 60 seconds should be reduced to 15 seconds without causing damage to the enamel surface or decreasing shear bond strength (i.e. shear bond of 6-8 Mpa), the purpose of the study is to keep the factors such as the acid concentration at 37%, age of tooth 9 to 16 years and no pre treatment condition of tooth as constant and the etching time alone is varied and its influence on shear bond strength of metallic brackets and its correlation with Adhesive Remnant Index (ARI) are studied. The results have shown that clinically adequate bond strength can be achieved at the lower etching time of 15 seconds with minimal iatrogenic damage to natural tooth structure.