Surface changes of dental PMMA related to different cleaning regimes

Objectives: The objective of this study was to evaluate surface roughness changes on a typical heat-polymerizing denture PMMA after brushing with dentifrices and a newly developed cleaning foam.

Methods: Eight specimens of Paladon 65 per treatment were fabricated according to manufacturer's instructions and polished. The treatment groups were brushing with two common family toothpaste-slurries (FT1 & FT2), a new cleaning foam (cf) and water as reference. A fifth group contained effervescent denture tablets (dt) without brushing. The brushing conditions simulated a product usage period of approximately 2 years. Surface roughness measurements were obtained from each specimen by mechanical profilometry. The differences “roughness after 90 minutes minus start values” were statistically analyzed. The surface roughness (in terms of Ra, Rrms, Rz) followed a normal distribution in each group. The one-factorial analysis of variance resulted in a significant (p = 0.000) treatment effect which was analyzed further by Student-Newman-Keuls-test (SNK). The specimen surfaces were further analyzed by SEM, AFM, and CLSM.

Results: All methods revealed statistically significant roughness changes only for the brushing treatments with dentifrices. In terms of Ra, Rrms and Rz the SNK test indicated homogeneous sub-groups with a statistically significant ranking (water=cf=dt) < FT2 < FT 1, i.e. water, cf and dt are statistically equivalent with statistically significant lower response compared to the two other treatments (FT1 and FT2).

Conclusions: Brushing of denture PMMA with toothpaste leads to a significant increased surface roughness that enhances bacterial adhesion and therefore should not be recommended. Such surface changes were not observed for brushing with water, the effervescent denture tablet and the new cleaning foam. Research funded by GlaxoSmithKline.