Residual monomer content and its release into water from denture base materials

Objectives. The aim of this study was to determine the content and amount of residual monomer released from heat-cured and chemical-cured polymethyl methacrylate (PMMA) during storage in water. Methods. Residual monomer was extracted from ground PMMA with tetrahydrofuran and from the storage water with n-hexan. Samples were analyzed by using HPLC-chromatography. Duration of the storage period in water was up to 8 wk at temperatures of +22°C and +37°C. Results. Residual monomer content of chemical-cured PMMA was higher than that of heat-cured PMMA. The effect of storage temperature was significant (p<0.001). During the first day of storage at +37°C, the monomer release from chemical-cured PMMA was 1906.7 ppm and from the heat-cured PMMA 34.5 ppm and that release was higher at +37°C than at +22°C (p<0.001). Significance. This study suggests that the amount of released monomer can be diminished by storing the PMMA product in water for at least 1 d before use, preferably at +37°C.