Cytotoxicity assessment of eluates from vacuum-forming thermoplastics.

OBJECTIVES: This study aimed to evaluate possible cytotoxic effects of thermoplastic materials commonly used for occlusal splints and orthodontic appliances. METHODS: Seven thermoplastics were included: three variants of the Essix sheets (C+, Plus, and Tray Rite; Dentsply Sirona), three thermoplastics (Bleach Heavy, Splint, and X-Heavy; Cavex Holland) and Invisalign (Align Technology). Cylindrical specimens (n = 24; 10 mm diameter) were incubated in cell culture medium for 24 h and 14 days. After incubation, the medium was collected, serially diluted, and dosed to primary human gingival fibroblasts in triplicate. Medium processed like the samples was used as negative control. Cell viability was evaluated by XTT and LDH assay to assess metabolic activity and membrane integrity, respectively. Next, cell cycle was assessed with flow cytometry after exposing HGFs to undiluted extracts. RESULTS: The 24-hour and 14-day extracts did not evoke cytotoxicity after 24-hour incubation. No significant differences in cell viability (one-way ANOVA, p > 0.05 ) in the XTT and LDH assays or in cell cycle distribution between the different materials (two-way ANOVA, p > 0.05 ). CONCLUSION: The thermoplastics tested in the study showed no evident in-vitro cytotoxic effects. Further investigation should focus on determining which compounds are released from thermoplastic materials and assessing potential toxicity related to exposure to these compounds. CLINICAL SIGNIFICANCE: Our study adds to the growing body of evidence on the biocompatibility of dental thermoplastics. This can aid clinical decision-making, as thermoplastics are expected to be safe to use in terms of cytotoxicity.

Level of BPA contamination in resin composites determines BPA release.

OBJECTIVES: Resin composites may release bisphenol A (BPA) due to impurities present in the monomers. However, there is a lack of knowledge regarding the leaching characteristics of BPA from resin composites. Therefore, experimental resin composites were prepared with known amounts of BPA. The objective of this study was (1) to determine which amount of BPA initially present in the material leaches out in the short term and, (2) how this release is influenced by the resin composition. METHODS: BPA (0, 0.001, 0.01, or 0.1 wt%) was added to experimental resin composites containing 60 mol% BisGMA, BisEMA(3), or UDMA, respectively, as base monomer and 40 mol% TEGDMA as diluent monomer. Polymerized samples (n = 5) were immersed at 37 °C for 7 days in 1 mL of water, which was collected and refreshed daily. BPA release was quantified with UPLC-MS/MS after derivatization with pyridine-3-sulfonyl chloride. RESULTS: Between 0.47 to 0.67 mol% of the originally added BPA eluted from the resin composites after 7 days. Similar elution trends were observed irrespective of the base monomer. Two-way ANOVA showed a significant effect of the base monomer on BPA release, but the differences were small and not consistent. SIGNIFICANCE: The released amount of BPA was directly proportional to the quantity of BPA present in the resin composite as an impurity. BPA release was mainly diffusion-based, while polymer composition seemed to play a minor role. Our results underscore the importance for manufacturers only to use monomers of the highest purity in dental resin composites to avoid unnecessary BPA exposure in patients.

Elution from direct composites for provisional restorations.

Purpose To assess elution from direct composite materials for provisional restorations and compare them with elution from direct restorative composites for permanent restorations.Methods Two dual-cure (Integrity Multi-Cure and Tempsmart DC) and two self-curing composites (Protemp 4 and Structur 3) were used, with Essentia serving as a reference. Cylindrical specimens (n=20) were cured according to the manufacturer's instructions; the dual-cure materials were prepared in both self- and dual-curing modes. Elution experiments were performed using water and absolute ethanol. The samples were incubated at 37 °C for either 24 h or four weeks; the extraction solvents were refreshed weekly. The eluted BisEMA (-3 / -6 / -10), BisGMA, CQ, UDMA, and TEGDMA were quantified using UHPLC-MS/MS.Results Monomer elution was detected in all provisional composites at 24 h and four weeks, but the amounts released did not exceed those released by the reference composite. When prepared in self-curing mode, Integrity Multi-Cure exhibited significantly higher elution of BisEMA-3, -6, and -10 in ethanol both after 24 h and cumulatively after four weeks. Self-cured Tempsmart DC released significantly more CQ, TEGDMA, and UDMA in both water and ethanol after immersion for 24 h and four weeks, along with significantly more BisGMA in ethanol both after 24 h and four weeks comparison to dual-cured Tempsmart DC (two-way ANOVA, post-hoc Tukey, P < 0.05).Conclusions Provisional composite materials did not elute higher amounts of monomers than a restorative composite. Dual-cured materials, prepared in the self-curing mode, show a trend towards higher monomer elution.