An ideal prophylaxis paste should have both cleaning and polishing properties. Key elements would be abrasive particles that become less agressive under load. The abrasive perlite, a volcanic glass with a sheetlike gemoetry, is claimed to have these unique properties. This study evaluated the average particle size, size distribution, and morphology of perlite in raw form, in an unused prophylaxis paste, and a used prophylaxis paste. The su rface roughness induced on enamel and dentinal specimens was quantitated after paste application in either a rubber cup or a nylon brush. Flour of pumice, a standard prophylaxis paste, a polishing paste, and water were tested similarly. The luster induced by the tested pastes and controls was assessed. Perlite blunted and disintegrated under load. The perlite-containing prophylaxis paste acted as a fine or superfine prophylaxis paste, although it was ranked as medium, based on the mean particle size of its abrasive in the fresh, unused form. Perlite might provide the properties required for the abrasive material of an ideal prophylaxis paste.