Effect of Post-polymerization Treatment on Cytotoxicity of a Denture Resin

Objective: To investigate the effects of different post-polymerization treatments of a heat-polymerized polymethyl methacrylate resin on in vitro cell viability. Methods: One, 2, 3 and 4 weeks-old eluates of 3 groups of disks (no-treatment, polished and warm water-stored), n=4, were added to a medium of 3T3 mouse fibroblasts. After 24 hours of incubation, optical density values (reflecting the amount of live cells) were obtained using the MTT assay. The test was repeated using the same 3 groups, n=9, after 24 and 48 hours of exposure. Medium without eluate was used as a control for both tests. Data were analysed using the Means procedure (0.01 probability level). Results: For the initial test, values of the 3 test groups were always lower than the control, except for the 2-week values, when the no-treatment group was the highest. For the repeat test, the values for the negative control were also the highest for both time periods. For all groups, values were higher at 48hrs compared to 24hrs, with a significant difference between the water-stored and polished group (p=0.0003), control and polished group (p<0.0001) and no-treatment and polished group (p=0.0081). For the 24hrs eluates, there was a significant difference in density readings between the following groups: water-stored and medium (p=0.0003), polished and medium (p<0.0001) and polished and no-treatment (p=0.0081). For the 48hrs eluates, the following groups differed: water-stored and medium (p=0.0006), medium and polished (0.0053), and medium and no-treatment (p=0.0002). Conclusion: Exposure to eluates of a polymethyl methacrylate resin had a negative effect on fibroblast viability, demonstrated by less live cells. For water-stored and polished disks, this effect was time-dependent, with a higher viability following exposure to 48hrs-eluates than to 24hrs eluates. Eluates from polished and water-stored disks did not have a less negative effect on fibroblast viability than eluates from untreated disks.