Toxicity of Acrylic Reline Resins submitted to Salivary Esterase

Methods: Disk-shaped specimens of Pro Base Cold (P), Kooliner (K) and Ufi Gel Hard (U), were incubated in medium with AChE (pH 7.4, 37ºC) (experimental group) or just medium (control group) for 72 hours. The cytoxicity of the resin eluates was measured in cultured human fibroblasts, using the MTT reduction assay. Furthermore, resin´s eluates allowed the quantification of potential toxic compounds by HPLC, including the residual monomers methylmetacrylate (MMA), isobutylmethacrylate (IBMA) and hexanodioldimethacrylate (HDMA), and their hydrolysis common product methacrylic acid (MA). Non-parametric Mann Whitney tests were performed between groups with a 5% significance level.

Results: The cell viability of cultures exposed to P specimens (control and experimental) was statistically similar to the non-cytotoxic negative control. Control K specimens decreased almost 90% in cell viability and control U specimens almost 30%. AChE changed these values only slightly (p<0.05), meaning that Kooliner maintained as a severely cytotoxic material and Ufi Gel Hard as slightly cytotoxic. Considering the quantification of potential toxic compounds, experimental P specimens showed a lower release of MMA and a higher release of MA than the control group. It was observed that there were no differences between K groups when IBMA was measured. MA was not found in K control group but it reached 840±145 µmol/L in K experimental group. Evaluating U eluates, differences were not obtained between groups in HDMA release but the amount of MA increased in the presence of AChE.

Conclusion: AChE effect on the hydrolysis of residual monomers depended on their chemical composition. No effect was detected on the viability study since AChE didn´t change the level of cytotoxicity of the materials.