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

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).

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).

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.

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.