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-hexane. Samples were analyzed by using HPLC-chromatography. Duration of the storage period in water was up to 8 wk at temperatures of +22 degrees C and +37 degrees 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 degrees 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 degrees C than at +22 degrees 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 degrees C.