The effect of an air-powder abrasive system on dental hard tissues was tested on 20 volunteers. Impressions of 150 randomly selected areas were taken before and after airpolishing and positive replicas were prepared for scanning electron microscopic examination (SEM). The amount of dental plaque on tooth surfaces was reduced by the treatment (P less than 0.001). The abrasive changes caused by airpolishing on enamel were greater on the surfaces covered by dental plaque before the airpolishing compared to the surfaces without plaque (P less than 0.01). The enamel and cemental surfaces were more abraded after the treatment compared with the initial condition. Despite the effectiveness of the dental airpolishing technique, the negative aspects should be considered in the decision to use airpolishing in routine prophylaxis, especially in patients with root surfaces exposed to the oral cavity.