Effect of use period and microwave disinfection on clinical performance and quantification of microbial of a hard chairside reline resin

This study evaluated the effect of disinfection method on the clinical performance and quantification of microbial of a hard chairside reline resin after 1-year service period. Forty adult patients aged between 30 and 75 years, who required denture reline treatment, participated in this study. Tokuyama Rebase II was used to reline complete maxillary dentures. Immediately after the reline, assessment of the flow and smoothness was rated by the clinician as satisfactory and unsatisfactory. The edentulous subjects were randomly divided into 2 groups (n=20) and dentures were cleansed according to two methods: CG (control group)- brushing with coconut soap and soft toothbrush; DG (disinfection group)- brushing according to previous methods and microwave disinfection once a week for 3 min at 650W. Furthermore, all dentures were immersed in water at night. Evaluations were conducted by two examiners working separately. Color stability, gloss, staining or material discoloration, irritation to oral tissue, detachment or frature of material and surface roughness were assessed at 7 and 15 days, 1, 3, 6 and 9 months and 1 year post-placement. Quantitative microbial cultures were taken from the tissue side of each maxillary denture at all experimental periods. The data were analyzed by ANOVA and Friedman and Tukey tests. A 95% confindence level was used. Flow and smoothness of the material during relining were considered to be good or satisfactory in all the cases. Values color alterations of DG were significantly lower than those of CG (P<0.05). Color change observed after 15 days are greater than values obtained at 7 days recall (P<0.05). All color changes observed for the CG were considered noticeable (between 1.5 and 3.0 NBS). In disinfection group, color change was slight (between 0.5 and 1.5 NBS). There were statistically significant differences between L* values obtained initially and over the 3 months, between 15 days and 3 months and between 15 days and 1 year (P<0.05). No significant differences were observed between group and time for the parameters a* and b*. There was a statistically significant increase of gloss values after 3 and 6 months compared with baseline (P<0.05). The results also revealed significant differences between 3 months and 7 days periods (P<0.05). Of the 40 cases, one case of each group received the Bravo ranking for discoloration and staining. All cases received Alfa rank for irritation and separation or fracture of the material. The roughness values obtained after microwave disinfection were statistically lower compared to control group (P<0.05). There were no significant differences between mean values of roughness of periods over the 3 months. Comparison among baseline, 7 days, 15 days and 1 month revealed that there were no significant differences on the surface roughness of evaluated material. Microwave irradiation for 3 minutes at 650W resulted in sterilization of complete dentures. For CG, no differences were observed for the log (CFU/mL) among the baseline, 9 months and 1 year. It can be concluded that the disinfection was effective for microwave sterilization of relining dentures. Microwave disinfection caused improvement on color stability and surface roughness of the reline material. Clinical perfomance of Tokuyama Rebase II was not negatively affected after microwave disinfection. Thus, microwave can be used for the relining denture disinfection. Moreover, Tokuyama Rebase can be conserved in the dentures by at least 1 year without replacement.