Abstract
The degree of conversion (DC) and the released bisphenol A diglycidyl ether dimethacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) monomers of bulk-fill composites compared to that of conventional flowable ones were assessed using micro-Raman spectroscopy and high performance liquid chromatography (HPLC). Four millimeter-thick samples were prepared from SureFil SDR Flow (SDR), X-tra Base (XB), Filtek Bulk Fill (FBF) and two and four millimeter samples from Filtek Ultimate Flow (FUF). They were measured with micro-Raman spectroscopy to determine the DC% of the top and the bottom surfaces. The amount of released monomers in 75% ethanol extraction media was measured with HPLC. The differences between the top and bottom DC% were significant for each material. The mean DC values were in the following order for the bottom surfaces: SDR_4mm_20s > FUF_2mm_20s > XB_4mm_20s > FBF_4mm_20s > XB_4mm_10s > FBF_4mm_10s > FUF_4mm_20s. The highest rate in the amount of released BisGMA and TEGDMA was found from the 4 mm-thick conventional flowable FUF. Among bulk-fills, FBF showed a twenty times higher amount of eluted UDMA and twice more BisGMA; meanwhile, SDR released a significantly higher amount of TEGDMA. SDR bulk-fill showed significantly higher DC%; meanwhile XB, FBF did not reach the same level DC, as that of the 2 mm-thick conventional composite at the bottom surface. Conventional flowable composites showed a higher rate of monomer elution compared to the bulk-fills, except FBF, which showed a high amount of UDMA release.
Highlights
The evolution led to contemporary resin-based composites (RBCs) showing high clinical success and survival rates [1,2,3,4]
The top and bottom surface degree of conversion (DC) values of the materials are presented in Figures 1 and 2
The mean DC values on the top surface of the materials were in the following order: SDR_4mm_20s > FBF_4mm_20s > FUF_4mm_2mm > FUF_4mm_20s > FBF_4mm_10s > XB_4mm_20s > XB_4mm_10s; the order of the mean DC values on the bottom surface was significantly different from the top surface: SDR_4mm_20s > FUF_2mm_20s > XB_4mm_20s > FBF_4mm_20s > XB_4mm_10s > FBF_4mm_10s > FUF_4mm_20s
Summary
The evolution led to contemporary resin-based composites (RBCs) showing high clinical success and survival rates [1,2,3,4]. Studies investigated the amount of eluted monomers; the biocompatibility and clinical performance of bulk-fill flowable RBC base materials are limited [20,21,22,24,26]. Biocompatibility depends on the quality and quantity of released monomers and their derivates, which can irritate the pulp, the soft tissues of the oral cavity and may lead eventually to a toxic reaction [27,28] Several factors, such as the DC, the specimen thickness, the chemical composition, the filler particle type and content, the porosity and the solvent can influence the amount of released monomers [29]
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