ABSTRACT
The purpose of this study was to determine the influence of microabrasion on shear bond strength of composite resin to dentin. Ninety noncarious recently extracted human molars were selected. The occlusal surface of teeth was ground, exposing flat dentin surface to accommodate bonded restorative material. The teeth were divided into nine groups of 10 teeth each. The dentin surfaces of the first group were conditioned with Total Etch for 10 seconds, then washed and dried to serve as control. Air abrasion conditioning of the remaining 8 groups was accomplished with "Micro Prep Director+" air abrasion device using 0.4mm nozzle tip perpendicular to sample surface and 1cm away from it. Surface abrasion was performed using a 27 micro m aluminum oxide particle stream at 60 psi for 10 seconds in two groups, and for 20 seconds in another two groups. Air pressure was then increased to 120 psi to abrade surfaces of another two groups for 10 seconds, and for 20 seconds in the remaining two groups. Additional conditioning with Total Etch was performed to the surfaces of the last four groups combined with air abrasion treatment. Three teeth from each of the nine groups were mounted in a profilometer and three Ra values were recorded for dentinal surface roughness before and after surface treatment. Remaining samples were prepared for bonded composite restorations, and shear bond strengths were determined using a testing machine. Results revealed significantly higher roughness of etched surface than air abraded dentin. Meanwhile acid etching created bond strengths to dentin that were almost twice as high as those achieved by air abrasion. It could be, thus, suggested that cavities prepared by air abrasion should also be acid etched to achieve adequate bonding with resinous materials