Air polishing increases the surface roughness of dental restorations, enhancing bacterial adhesion. This in vitro study was the first, to the authors' knowledge, to evaluate the effect of sodium bicarbonate and glycine powders, at different application distances (2 and 7 mm) and times (5, 10, and 30 seconds), on the surface roughness of a nanocomposite material used in restorations. Untreated slides were used as controls. Surface roughness was measured using atomic force microscopy. Air polishing with glycine powder for 5 seconds, at both application distances, determined the lowest surface damage. Even with all the limitations of any in vitro analysis, this study further supports the safety of this method of air polishing.