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Background: This in vitro study aimed to assess the ability and efficacy of HX-BGC, a novel bioactive glass-ceramic (SiO 2 -P 2 O 5 -CaO-Na 2 O-SrO), to reduce dentine tubule permeability. Methods: Dentine discs from human third molars were etched and randomly allocated into five groups: Group 1 -distilled water; Group 2 -Sensodyne Repair toothpaste (containing NovaMin®); Group 3 -HX-BGC toothpaste (containing 7.5% HX-BGC); Group 4 -control toothpaste (without HX-BGC); and Group 5 -HX-BGC powder. Specimens were treated daily by brushing with an electric toothbrush for 20 seconds. Between daily treatments (7 days total), specimens were immersed in artificial saliva for 24 hours. Dentine permeability was measured at baseline, after the first treatment, after the first 24-hour immersion in artificial saliva and at the end of day 7. Dentine morphology and surface deposits were observed by scanning electron microscopy after one day and 7 days of treatment, respectively. Results: Sensodyne Repair and bioactive glass-ceramic toothpaste significantly and immediately lowered dentine permeability. The HX-BGC powder group showed the highest reduction in dentine permeability after 7 days of treatment. Conclusions: The novel bioactive glass-ceramic material HX-BGC is effective in reducing dentine permeability by occluding open dentine tubules, indicating that HX-BGC may be a potential treatment for dentine hypersensitivity.

Dentine hypersensitivity (DH) is a common condition that is frequently encountered in dental practice. The aim of this multi-centre and cross-sectional study was to establish the prevalence of DH in the general population in China. A total of 6843 subjects were questioned and examined using a triple syringe with a blast of cold air to confirm the diagnosis of DH. The sensitive surface, loss of attachment and gingival recession of sensitive teeth were measured and recorded. Of the 2932 subjects reporting hypersensitive symptoms, 2363 subjects were further diagnosed as DH, giving an overall prevalence of 34·5%. The greatest number of subjects with DH were within the 50-59 years age group (P < 0·01). The most commonly affected teeth were the premolars and the most provoking factor was the presence of a cold stimulus. The prevalence of DH in a representative sample of the general population in China was 34·5%, indicating that DH is a common oral problem. Therefore, the recognition of the condition and subsequent treatment by the dentist is therefore essential if the condition is to be managed correctly.

Keywords:Bioavailability Polycyclic aromatic hydrocarbons (PAHs) Suspended sediment (SPS) Dams Water conservation project Water quality s u m m a r yThe water-sediment regulation of the Xiaolangdi Reservoir is conducted to control the relationship between riverine runoff and sediment transport of the Yellow River; however, there is no research about the effect of water-sediment regulation on the bioavailability and fluxes of hydrophobic organic compounds (HOCs). In this study, water and suspended sediment (SPS) samples were collected downstream of the Xiaolangdi Reservoir before, during, and after the water-sediment regulation in 2013. The 16 priority polycyclic aromatic hydrocarbon (PAH) concentrations of freely dissolved, total dissolved, and SPS-associated were determined. During water regulation, water discharged from the reservoir at a high flow rate led to the resuspension of downstream sediment. During sediment regulation, the sediment ejected from the reservoir resulted in higher SPS concentrations than that during water regulation. Both the freely and total dissolved PAH concentrations in river water during sediment regulation were the highest, followed by the concentrations during water regulation and before regulation. The freely dissolved PAH concentrations in river water during the water-sediment regulation were 2-11 times higher than those before water-sediment regulation. This was due to the fact that the resuspended sediment during water-sediment regulation could release PAHs into water phase, and more contaminants were released from the SPS during sediment regulation than during water regulation. The fluxes of sediment and the 16 priority PAHs (R 16 PAHs) during water-sediment regulation contributed to 32.4% and 35.7% of their annual fluxes, respectively, which were higher than the contribution (22.6%) of water discharge. This study suggested that the water-sediment regulation might reduce the long-term retention of sediment and PAHs in the reservoir. However, the environmental risk of PAHs as well as other contaminants downstream of the reservoir and in the estuary might increase during that period. Therefore, the effect of water-sediment regulation on the bioavailability and environmental risk of HOCs should be considered in the operation and management of the Xiaolangdi Reservoir in the future.