A new approach to cure and reinforce cold-cured acrylics

Purpose: The low degree of polymerization of cold-cured acrylics has resulted in inferior mechanical properties and fracture vulnerability in orthodontics removable appliances. Methods: In this study, the effect of reinforcement by various concentrations of chopped E-glass fibers (0%, 1%, 2%, 3% and 5% by weight of resin powder) and post-curing microwave irradiation (800 W for 3 min) on the flexural strength of cold-cured acrylics was evaluated at various storage conditions (at room temperature for 1 day and 7 days; at water storage for 7, 14 and 30 days). Results: The data was analyzed by using 1-way and 2-way ANOVA, and a Tukey post hoc test (α = .05). The specimens with chopped E-glass fibers treated with post-curing microwave irradiation significantly increased the flexural strength of cold-cured PMMA. The optimal concentration might be 2% fibers under irradiation. Conclusions: The exhibited reinforcement effect lasted in a consistent trend for 14 days in water storage. A new fiber-acrylic mixing method was also developed. © 2012 The Author(s).published_or_final_versio

Methyl methacrylate and respiratory sensitization: A Critical review

Methyl methacrylate (MMA) is a respiratory irritant and dermal sensitizer that has been associated with occupational asthma in a small number of case reports. Those reports have raised concern that it might be a respiratory sensitizer. To better understand that possibility, we reviewed the in silico, in chemico, in vitro, and in vivo toxicology literature, and also epidemiologic and occupational medicine reports related to the respiratory effects of MMA. Numerous in silico and in chemico studies indicate that MMA is unlikely to be a respiratory sensitizer. The few in vitro studies suggest that MMA has generally weak effects. In vivo studies have documented contact skin sensitization, nonspecific cytotoxicity, and weakly positive responses on local lymph node assay; guinea pig and mouse inhalation sensitization tests have not been performed. Cohort and cross-sectional worker studies reported irritation of eyes, nose, and upper respiratory tract associated with short-term peaks exposures, but little evidence for respiratory sensitization or asthma. Nineteen case reports described asthma, laryngitis, or hypersensitivity pneumonitis in MMA-exposed workers; however, exposures were either not well described or involved mixtures containing more reactive respiratory sensitizers and irritants.The weight of evidence, both experimental and observational, argues that MMA is not a respiratory sensitizer

Abstract. Epigenetic marks at birth predict childhood body composition at age 9 years

Objective: While genomic variation explains only a modest proportion of the risk of cardiovascular and metabolic disease, animal models demonstrate that maternal environmental influences alter epigenetic processes in the offspring, with important effects on their later body composition and cardiometabolic function. Whether such processes operate in humans has not been examined.Methods: Using DNA extracted from stored umbilical cord tissue from healthy neonates who were subsequently extensively phenotyped, we related the DNA methylation status of specific CpGs 5’ from candidate genes to body composition measured by DXA scanning at age 9 years. Appropriate institutional ethics committee clearance and participants’ informed consent were obtained.Results: Methylation, measured by the Sequenom MassARRAY system, varied greatly at particular CpG sites. Of 68 CpGs studied, 31 had a median methylation >5% and a 5-95% range >10%. Independently of sex, there were strong correlations of the degree of methylation in specific CpGs in eNOS with childhood fat mass (Pearson correlation rp 50.42, n566) and trunk/limb fat ratio (rp 50.33, n566), and in RXRA methylation with fat mass and percentage fat mass (rp 50.32 and 0.29, respectively, n564) (all p,0.005, taking account of methylation at other CpG sites). Methylation at these sites was not linked to birth weight. Controlling for sex, perinatal epigenetic marks explained more than 40% of the variance in body composition at age 9 years.Conclusions: Epigenetic marks at birth predict a significant proportion of the variance in later childhood adiposity, indicating that substantial components of later metabolic disease risk are induced before birth. Perinatal epigenetic analysis may have utility in identifying individual vulnerability to later chronic non-communicable disease. MAH and JSJ are supported by the British Heart Foundation. PDG and AS are funded by the National Research Centre for Growth and Development (New Zealand). BSE is supported by the Agency for Science, Technology and Research (Singapore). This work was supported by the charity WellChild (previously Children Nationwide), by the University of Southampton, by the UK Medical Research Council and the EpiGen consortium