Adverse effects on PMMA caused by mechanical and combined methods of denture cleansing.

This study evaluated the abrasiveness of mechanical and combined methods of denture hygiene, by the analysis of mass loss and surface roughness. Acrylic resin specimens (Plexiglass) were brushed by a tooth brushing machine (Mavtec) with a soft brush (Tek) and water (control) or four dentifrices (Sorriso, Colgate, Polident and Corega) (Experimental groups) for 50 min, representing one year of brushing (mechanical method). After brushing, the specimens were immersed in 0.5% sodium hypochlorite simulating a daily cleaning of 20 min for one year (combined method). Distilled water (23 ºC) was employed as control. The mass loss (g) was analyzed by an analytical balance and the surface roughness (μm) by a rugosimeter. Data were subjected to ANOVA and Bonferroni test (α=0.05). Polident dentifrice showed lowest values of mass loss for both methods (mechanical: -0.0072±0.0017, combined:-0.011±0.002) and the combined method resulted in greater mass loss than the mechanical, except for Corega. For the surface roughness, after the mechanical method, the lowest values were registered for water (-0.007±0.016) and Polident (0.402±0.378); for the combined method, water (-0.063±0.013) showed the lowest values; there was no statistically significant difference between methods. It was concluded that Polident was the less abrasive dentifrice and the association between chemical and mechanical methods increased the mass loss but did not change the surface roughness of specimens.