Evaluation of cutting patterns produced with air-abrasion systems using different tip designs.

This study assessed cavity preparations produced with different air abrasion tip parameters. Twelve test groups of extracted teeth were prepared to evaluate the parameters of 80 degrees or 45 degrees nozzle angles and 0.38 or 0.48 mm inner tip diameters. All other factors were held constant. A device was made to hold the specimen and air abrasion handpiece that standardized the distance and position relative to the tooth and time of application. The cavities were evaluated by assessing the rounding of the cavosurface margins and cavity floor. Measurements of cavosurface angles and the angle of concavity were made at the deepest portion of the abraded surface using scanning electron micrographs. The cavosurface angles were compared using paired t-test, and the effects of the tip design parameters were analyzed by ANOVA and Duncan's Multiple Range test. From the cavity patterns found in this study, the authors suggest that 80 degrees angle tips are more appropriate than 45 degrees angle tips for making narrow, deep cuts for preventive resin restorations. Conversely, when shallow preparations are needed, as in the case of Class V cavity preparations, cutting patterns of 45 degrees angle tips are more suitable.

Effect of handpiece tip design on the cutting efficiency of an air abrasion system.

PURPOSE: The aim of this study was to evaluate the effect of nozzle angle and tip diameter on the cutting efficiency of an air abrasion system. MATERIALS AND METHODS: Thirty-six extracted human third molars were air-abraded with the PrepStar microabrasion machine using a handpiece with either 80 degrees or 45 degrees nozzle angles with 0.38 or 0.48 mm tip orifice diameters. The following parameters were held constant: abrasive particle size (27 microm), air pressure (80 psi), distance (2 mm) and duration (15 seconds). The cutting efficiency was compared using enamel, dentin and cementum substrates. Width and depth of the cutting patterns were analyzed and measured using scanning electron micrographs. RESULTS: Statistical analysis using three-way ANOVA and Duncan's Multiple Range test revealed that the width of the cuts was significantly greater when the cavities were prepared using the 45 degrees nozzle angle. Significantly deeper cavities were produced with the 80 degrees nozzle angle. The tip orifice of the nozzle influenced the cutting efficiency in softer substrates, dentin and cementum. Precise removal of hard tissue is best accomplished using the 80 degrees angle nozzle tips for all types of tooth surfaces, enamel, dentin and cementum.