Direct and indirect monomer elution from an RBC product family

ObjectiveTo develop a model for quantitative comparison of elutable substances by direct elution from resin-bonded composite (RBC) test specimens versus indirect elutability of substances from RBC-restored teeth. Furthermore, it was to be investigated whether the different composites of the Tetric® RBC product family release different types and amounts of substances.MethodsFour different composite materials from the Tetric® product family were studied. For each material subgroup ten human third molar teeth were prepared with standard Class-I occlusal cavities. These ‘tooth group’ specimens were provided with a three-step adhesive system (incorporating TEGDMA) and the respective composite restoration. Same sized control specimens, of each RBC restorative material, were prepared (‘direct RBC’ groups). All specimens were placed in individual elution chambers such that the elution media (ethanol/water, 3:1) only came into contact with either the tooth root or ¾ height of the ‘direct RBC’ materials. They were incubated at 37 °C for up to 7 d. Samples of the eluant were taken after 1, 2, 4 and 7 d and were analysed by high-temperature gas chromatography/mass spectrometry.ResultsBisphenol A ethoxylate dimethacrylate (bisEMA), bisphenol A glycidyldimethacrylate (bisGMA), tetraethylene glycol dimethacrylate (TEEGDMA), decan-1,10-diol dimethacrylate (DDDMA) were mostly found in the eluates of the ‘direct RBC’ groups in statistically significantly greater amounts than in the eluates of the ‘tooth groups’. Such quantitative differences were also the case with eluates containing bisphenol A (BPA), dicyclohexyl phthalate (DCHP) and drometrizole, which are common in the environment. In contrast to the behavior found with all the other monomers, up to 3 orders of magnitude more triethylene glycol dimethacrylate (TEGDMA) was found in the ‘tooth groups’ compared to the ‘direct RBC’ groups, evidently released by the adhesive system.SignificanceThe release of most of the substances was clearly delayed in the ‘tooth groups’ indicative of their chronic, rather than acute, elution to the oral environment. A barrier function of the residual dentin layer and the adhesion layer can be inferred. The different release patterns of substances from the various composites of the RBC product family is a manifestation of their different and indication-specific compositions. Consideration of an overall restorative care (RBC plus adhesive) system, when assessing the total amount of released substances, is emphasized.     

Direct and indirect eluates from bulk fill resin-based-composites

ObjectivesTo compare elutable substances directly released from bulk-fill (BF) resin-based composites (RBCs) with indirect elution from teeth restored with a BF composite. In addition to (co)monomers, the analytical focus was on other potentially toxic ingredients or impurities. Furthermore, the barrier function of the residual dentin/adhesive layer was studied.MethodsSix BF-RBC materials were studied. For each material subgroup, ten human third molar teeth with standard Class-I occlusal cavities were prepared and provided with a three-step adhesive system and the respective composite restoration (tooth groups). Same sized control specimens of the restorative material were prepared (‘direct BF-RBC’ groups). Each specimen was placed in an elution chamber such that the elution media (ethanol/water, 3:1) only contacted the tooth root or ¾ height of each specimen. They were incubated at 37 °C for up to 7 d. Samples of eluate were taken after 1, 2, 4 and 7 d and were analysed by high-temperature gas chromatography/mass spectrometry.Results(Co)monomers such as Bisphenol A ethoxylate dimethacrylate (bisEMA) or tetraethylene glycol dimethacrylate (TEEGDMA) were mostly found in the eluates of the ‘direct BF-RBC’ groups in statistically significantly greater amounts than in the eluates of the ‘tooth groups’. The residual dentin and/or adhesive layers acted as a diffusion barrier for most of the substances except for triethylene glycol dimethacrylate (TEGDMA) or diethylene glycol dimethacrylate (DEGDMA). For TEGDMA up to 3 orders of magnitude more were found in the ‘tooth groups’ compared to the ‘direct BF-RBC’ groups, evidently released by the adhesive system.Substances of Very High Concern (SVHC) including TINUVIN® 328 and BPA were found mainly in the eluates of ‘direct BF-RBC’ groups.SignificanceFor estimation of biocompatibility, a total system, specifically BF-RBC + adhesive, should always be investigated since individual considerations, such as only elution from a BF-RBC, do not correctly reflect the total clinical situation. The focus of elution tests should not only be on the co(monomers), but also on other ingredients or impurities that may be released.