Analysis of the effects of air polishing powders containing sodium bicarbonate and glycine on human teeth

The aim of this study was an analysis of the root surface roughness caused by air polishing powders containing sodium bicarbonate or glycine. The roots of human molars were sectioned into dentin discs and irradiated with three different powders: (A) sodium bicarbonate (dv50 = 62 mu m), (B) glycine (dv50 = 49 mu m) and (C) glycine (dv50 = 21 mu m). Standardized conditions in terms of instrumentation time (5 and 10 s), pressure (1.8 bar), distance (2 and 5 mm) and angulation (45A degrees and 90A degrees) were applied. Surface roughness (DIN EN ISO 4287:1998) of the probes was analysed by means of the surface profile values "Pa" and "Pt" and the surface roughness value "Rz". The effect of treatment (treated vs. untreated) was studied on each disc. Geometric mean ratios (GMRs) from mixed effects models and confidence intervals (95 % CI) were calculated. For Pa, the comparison revealed significant differences between powders A and B (GMR 3.57, 95 % CI 2.87-4.43, p < 0.001) and powders A and C (GMR 2.72, 95 % CI 2.20-3.37, p < 0.001) for the overall effects. With respect to Pt, significant differences occurred between powders A and B (GMR 2.49, 95 % CI 2.11-2.94, p < 0.001) and powders A and C (GMR 2.39, 95 % CI 2.03-2.82, p < 0.001). Between powders B and C, there were no significant differences for Pa, Rz and Pt. Air polishing powders containing glycine caused significantly less alterations on human root surfaces compared to powders containing sodium bicarbonate. Powders containing glycine caused a significantly lower increase in root surface roughness compared to those containing sodium bicarbonate. Powders containing sodium bicarbonate may not be indicated for root surface treatment.