Aim: To evaluate the effects of two air-polishing powders, during orthodontic treatment, on the surface roughness of sound and demineralised enamel. Materials and methods: Forty-two caries-free human molars were collected, and the enamel surfaces were flattened and polished. Teeth were assigned to two groups (n= 21 each), a sound- and a demineralised-enamel group (subjected to pH-cycling over 2 weeks to create artificially induced white spot-like lesions). Within each group, teeth were further assigned to three groups (n= 7 each), air polished with either sodium bicarbonate, erythritol, or a negative control (water). Each sample was treated for 5 and 150 s. The average surface roughness (Ra) for each sample was measured using white-light-sensor profilometry. Results: On sound enamel, the Ra was roughly 0.17 ± 0.07 μm. After 150 s of air polishing, the Ra increased with erythritol (by 0.28 μm), and even more so with bicarbonate treatment (by 0.68 μm) (p< 0.01). On demineralised enamel, the Ra was roughly 0.79 ± 0.56 μm. The Ra increased after 5 s of air-polishing treatment similarly with erythritol and bicarbonate powders (by 1.03 μm and 1.04 μm, respectively) (p= 0.025), and even more after 150 s (by 2.48 μm and 2.49 μm, respectively) (p< 0.001). Conclusions: On white spot lesions, one should be aware that enamel surface roughness will increase with both erythritol and bicarbonate air-polishing powders, especially with longer exposure times.