Effect of a continuous mechanical polishing protocol and toothbrushing on the surface roughness of acrylic resin teeth.

Purpose: To evaluate in vitro the effect of a continuous mechanical polishing protocol, performed in different periods, on the surface roughness of acrylic resin teeth subjected to toothbrushing (Br).

Methods: Artificial acrylic teeth (n=30) were randomly divided into three groups according to the polishing protocol and toothbrushing (Br): Br; Br+Pol15 (Br associated with a biweekly polishing); Br+Pol30 (monthly polishing). Br group was subjected to a total of 89,000 brushing cycles. Polishing was performed by applying aluminum oxide paste to the specimens with a felt wheel coupled to an electric motor (5 seconds, 3,000 rpm) after each 741 and 1482 brushing cycles for Br+Pol15 and Br+Pol30 groups, respectively. A contact profilometer and an analytical balance were used to measure surface roughness and mass changes before (T0) and after 1, 2, 3, and 5 years (T4) of simulated toothbrushing. Scanning electron microscopy (SEM) images were obtained. Differences among groups were tested by means of two-way ANOVA/Bonferroni tests (P= 0.05).

Results: Toothbrushing gradually increased surface roughness [T0 - 0.16 (0.01); T4 - 0.30 (0.10); P< 0.001]. The tested polishing promoted a significant roughness reduction (P< 0.001) for both biweekly [T4 - 0.09 (0.01) ] and monthly [T4 - 0.13 (0.02) ] regimes, and it did not influence the mass alterations caused by toothbrushing. SEM showed a smoother aspect of the material surface subjected to biweekly polishing with less defects caused by brushing abrasiveness.

Clinical Significance: In order to reduce the effects of various deleterious factors on the properties of acrylic resin for removable prostheses during their period of use, a frequent mechanical polishing protocol could increase clinical performance and extend the lifespan of these appliances. Furthermore, a polishing protocol by means of a simple technique could be employed by patients in a home environment.