Correlation of the degree of conversion with the amount of elutable substances in nano-hybrid dental composites

ObjectivesThis study's purpose was to measure and compare the degree of conversion (DC) and the amount of elutable substances from modern resin-based composites (RBCs) as function of polymerization time. One nano-hybrid RBC based on tricyclodecane-(TCD)-urethane (Venus® Diamond) and two conventionally formulated RBCs (TetricEvo Ceram®, Filtek™ Supreme XTE) were considered.MethodDC (n = 5) was investigated in real time for 5 min by Fourier transform infrared spectroscopy (ATR-FTIR) in a filling depth of 2 mm at varied irradiation times (5, 10, 20, 40 s). After storing the specimens in ethanol/water for 7 d at 37 °C the eluates were analyzed by gas chromatography/mass spectrometry. Results were statistically analyzed using a multivariate analysis (α = 0.05) an independent t-test (p < 0.05) and a Pearson correlation analysis.ResultsIn all groups increasing curing time resulted in a significant increase in DC. For TetricEvo Ceram® a high significant inverse correlation was found between DC and the amount of eluted camphorquinone (CQ, Pearson correlation coefficient = −0.88), ethylene glycol dimethacrylate (EGDMA, −0.73), 4-N,N-dimethylaminobenzoic acid ethylester (DMABEE, −0.87), triethylene glycol dimethacrylate (TEGDMA, −0.68), Tinuvin P (−0.71) and bisphenol-A-polyetheylene glycol dimethacrylate (BisEMA, −0.84). Unexpectedly DC and the amount of eluted methyl acrylate (MAA) correlated directly (0.72). In the specimens of Venus® Diamond a significant inverse correlation was found between DC and the amount of eluted CQ (−0.69) and TEGDMA (−0.50), whereas in the specimen of Filtek™ Supreme XTE DC correlated with CQ (−0.96), EGDMA (−0.70), DMABEE (−0.87), TEGDMA (−0.92) and MAA (−0.92).SignificanceThis study demonstrated a strong inverse correlation between DC and elutable substances in RBCs. Both evaluation methods emphasis the importance of an adequate polymerization (20, 40 s), since short curing-times (5, 10 s) resulted in lower DC and higher amount of eluted substances with toxic potential.