Qualitative and quantitative characterization of monomers of uncured bulk-fill and conventional resin-composites using liquid chromatography/mass spectrometry

Objectives The aim of this study was to assess the resin matrix monomer composition of selected bulk-fill and conventional resin-composite materials using reverse phase liquid chromatography coupled with electron spray ionization mass spectrometry. Material and methods Six bulk-fill (SureFil SDR, Venus Bulk Fill, X-tra base, Filtek Bulk Fill flowable, Sonic Fill, and Tetric EvoCeram Bulk Fill) and eight conventional resin-composites (Grandioso Flow, Venus Diamond Flow, X-Flow, Filtek Supreme XTE, Grandioso, Venus Diamond, TPH Spectrum, and Filtek Z250) were tested. For assessment of resin composition and relative monomer amounts, uncured resin-composites were analysed with reverse phase liquid chromatography/electron spray ionization mass spectrometry. log P values (a measure of hydrophobicity) of detected compounds were calculated and their correlation to reverse phase liquid chromatography retention time was explored. Data were analysed with one-way ANOVA, Tukey post hoc test, Pearson correlation and regression analyses at α = 0.05. Results The main monomers detected were BisGMA, UDMA, TEGDMA, and BisEMA. Monomers were detected at variable combinations in different materials with significantly different relative amounts. Other monomers were detected including HDDMA, DEGDMA, TCD-DI-HEA, and SDR-UDMA in Grandioso flow, X-flow, Venus Diamond, and SureFil SDR respectively. A positive correlation between log P and reverse phase liquid chromatography retention time was detected (r2 = 0.62, p = 0.004). Conclusions Resin composition of bulk-fill resin-composites is comparable to that of conventional materials with the exception of SureFil SDR. The relative hydrophobicity of dental monomers can be determined by their reverse phase liquid chromatography retention time.