Determination of homologous distributions of bisEMA dimethacrylates in bulk-fill resin-composites by GC-MS

Objectives: Ethoxylated bisphenol A dimethacrylate (bisEMA) is a basis monomer in several dental resin composites. It was the aim of the present study to develop a method allowing detection of bisEMA and its different degrees of ethoxylation eluted from polymerized resin composites.

Methods: High-temperature gas chromatography/mass spectrometry (HT-GC/MS) by direct on-column injection was used to identify ethoxylated bisEMA in ethanol/water (3:1) eluates from polymerized specimen of four bulk-fill resin composites - Venus(®) bulk fill, Surefil(®) SDR™ flow, Filtek™ Bulk Fill and Sonic Fill™. Additionally, the unpolymerised pastes were analysed.

Results: The developed method allowed identification of a homologous series of bisEMA up to twelve ethoxy groups in the unpolymerised materials. The molecular masses of the homologous bisEMA varied between 452 g/mol and 892 g/mol and were detected for retention times from 9.43 min to 13.36 min. Analysis of eluates from polymerised materials identified bisEMA monomers with less than 6 ethoxy groups. Chromatograms showed larger peak areas for the lower volatile bisEMA with 4-6 ethoxy groups compared with higher volatile bisEMA with 2 or 3 ethoxy groups, thus indicating that the amounts of these homologues in the pastes were higher.

Significance: Ethoxylated bisEMA with up to twelve ethoxy groups can be identified by HT-GC/MS. In all eluates bisEMA was found. The higher the number of ethoxy groups the lower are the peak areas from bisEMA in the gas chromatogram. These findings may be significant for toxicological analysis of resin-composites incorporating bis-EMA.