The objective of this study is to characterize the defects in the dentin surface after air polishing for three types of polishing powders and five different nozzle distances. Human teeth were embedded in acrylic resin and then polished until the dentin surface became exposed. The nozzle of the polisher was fixed at a specified distance (2, 3, 4, 5, or 6 mm) and orientation (45°) with respect to the dentin surface. The three powders were CLASSIC (NaHCO(3), 65 μm diameter), PERIO (glycine, 25 μm diameter), and SOFT (glycine, 65 μm diameter). With respect to nozzle distance, we find a significant difference in the mean defect depth only at 6 mm. The spray distance of 6 mm produced the shallowest defect depths. This variable had no effect on the defect volume. SOFT powder had significantly less depths and volumes of defects than the other two powders. The contact angle of the dentin increased significantly in all polishing tests, compared to an unpolished dentin surface (control). We find that spray distance of 6 mm from the nozzle of the polisher and orienting on 45° angle produced less dentin surface defects than any other distance in all powder systems used. At this distance, SOFT powder produced statistically significant smaller depth and volume defects than the other two powder groups.