A Comparative Assessment of the Surface Roughness of Thermoplastic Denture Base Resins Following Adjustment and Re-Polishing

ABSTRACT

This study assessed the roughness of two injection-molded, thermoplastic materials used for denture bases compared with a polyamide material and compression molded Polymethylmethacrylate (PMMA) after the adjustment and re-polishing with either a laboratory protocol or a chair side protocol. Methods: Forty specimens, each of PMMA, Valplast, DuraFlex, Dura Cetal were fabricated and finished according to individual manufactures' instructions. These materials were adjusted with tungsten carbide (TC) burs to mimic gross adjustments, and then re-polished either on a lathe or bonded silicon carbide (B-SC). Following instrumentation, the specimens were assessed using contact profilometry and scanning electron microscopy. Two-factor ANOVA was used to determine significant differences in mean surface roughness (Ra and Rmax), with included factors being material type and re-polishing regimen. Results: Mean Ra values ranged from 0.26 (DuraFlex control) to 1.82 (Valplast adjusted with TC burs). Mean Rmax values ranged from 1.88 (Dura Flex control) to 13.76 (Valplast adjusted with TC burs). Two-factor ANOVA revealed that interaction of both factors was significant (p < 0.05) for Ra and Rmax. There was a statistically significant increase in both Ra (p < 0.05) and Rmax (p < 0.05) for all material types following the gross adjustment. With the exception of DuraFlex, re-polishing of samples that were previously adjusted with TC burs, on the dental lathe produced surfaces that were comparable to control samples. Conclusion: Adjustment of DuraFlex should be kept to a minimum since the adjustment produced the significant surface detriment that could not be corrected with either of the polishing regimens.