Temporal variability of global DNA methylation and hydroxymethylation in buccal cells of healthy adults: Association with air pollution

BACKGROUND: Epigenetic changes, such as DNA methylation, are observed in response to environmental exposure and in the development of several chronic diseases. Consequently, DNA methylation alterations might serve as indicators of early effects. In this context, the aim of this study was to assess the temporal variability of global DNA methylation and hydroxymethylation levels in buccal cells from healthy adult volunteers. METHODS: Global DNA methylation (%5mdC) and hydroxymethylation (%5hmdC) levels in human buccal cells, collected from 26 healthy adults at different time points, were quantified by UPLC-MS/MS. Associations between %5mdC and %5hmdC, respectively, and short-term exposure (1-7days) to air pollutants PM2.5 and PM10 were tested with mixed-effects models including various covariates. RESULTS/DISCUSSION: Dynamic short-term changes in DNA methylation and hydroxymethylation levels in buccal cells were observed, which were inversely associated with exposure to PM2.5 and PM10. An IQR increase in PM2.5 over a 7-day moving average period was significantly associated with a decrease of -1.47% (-1.74%, -1.20%) and -0.043% (-0.054%, -0.032%) in %5mdC and %5hmdC, respectively. Likewise, for PM10, a decrease of -1.42% (-1.70, -1.13) and -0.040% (-0.051%, -0.028%) was observed. CONCLUSION: Global DNA methylation and hydroxymethylatation varied over a time period of three weeks. The observed temporal variability was associated with exposure to ambient PM2.5 and PM10 levels. This should be taken into account when interpreting epigenetic alterations in buccal cells.status: publishe

Qualitative analysis of dental material ingredients, composite resins and sealants using liquid chromatography coupled to quadrupole time of flight mass spectrometry

Since 2011, the World Health Organization has encouraged a global phase-down of the use of dental amalgam and actively supported the use of alternative, resin-based dental materials. The resins consist of (meth)acrylate monomers derived from Bisphenol A (BPA), such as Bisphenol A glycidyl methacrylate (BisGMA) and Bisphenol A ethoxylate methacrylate (BisEMA) or triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) which lack the BPA backbone. Besides monomers, other compounds such as photoinitiators and stabilizing agents can be present in the dental resin matrices. The current study consists in the development of an analytical method for the separation and identification of dental material components using LC-QTOF-MS. The developed method was applied on several dental material ingredients, unpolymerized composite resins, and a common dental sealant. The acquired high resolution accurate-mass data was analyzed using suspect screening with an in-house developed library. Next to the main components, various isomers and impurities related to the production of the main component have been detected and identified in the dental material ingredients. In total, 39 chemicals have been identified in the analyzed dental materials. On average 15 chemicals have been identified. Major components, such as BisEMA, BisGMA and TEGDMA were identified although they were not always stated in the material safety data sheets. Minor components included photoinitiators, such as ethyl 4-dimethyl aminobenzoate (EDMAB) and (meth)acrylates impurities originating from production of main ingredients.status: publishe

Degradation products of resin-based materials detected in saliva in vivo

Abstract: ObjectivesDental composites remain under scrutiny regarding their (long-term) safety. In spite of numerous studies on the release of monomers both in vitro and in vivo, only limited quantitative data exist on the in vivo leaching of degradation products from monomers and additives. The aim of this observational study was for the first time to quantitatively and qualitatively monitor the release of parent compounds and their degradation products in saliva from patients undergoing multiple restorations.Materials and methodsFive patients in need of multiple large composite restorations (minimally 5 up to 28 restorations) due to wear (attrition, abrasion, and erosion) were included in the study, and they received adhesive restorative treatment according to the standard procedures in the university clinic for Restorative Dentistry. Saliva was collected at different time points, starting before the restoration up until 24 h after the treatment with composite restorations. Saliva extracts were analyzed by liquid chromatography-mass spectrometry.ResultsLeaching of monomers and degradation products was highest within 30 min after the placement of the restorations. The highest median concentrations of monomers were recorded for UDMA, BisEMA-3, and TEGDMA; yet, besides BisEMA-3 and TEGDMA, no monomers could be detected after 24 h. Mono- and demethacrylated degradation products remained present up to 24 h and concentrations were generally higher than those of monomers. In patients with multiple restorations, degradation products were still present in the sample taken before the next operation, several weeks after the previous operation.ConclusionsExposure to residual monomers and degradation products occurs in the first hours after restoration. Monomers are present in saliva shortly after restoration, but degradation products can be detected weeks after the restoration confirming a long-term release.Clinical significanceFuture research should focus more on the release of degradation products from monomers and additives from resin-based materials given their prolonged presence in saliva after restoration