The prevalence of sleep bruxism and associated factors in children: a report by parents.

AIM: To evaluate the prevalence of sleep bruxism and associated factors among children aged 3-12 years as reported by parents via a questionnaire. METHODS: A cross-sectional study was conducted with a sample of 148 parents/caregivers of children aged 3-12 years treated at paediatric dentistry clinics. Parents/caregivers answered a questionnaire in the waiting room. Information on the gender and age of the child, age of parent/caregiver, meaning of bruxism and child's sleep (type of sleep, if he/she slept alone, hours of sleep per night and if nocturnal bruxism could affect his/her health) were collected. Descriptive statistics were performed and Poisson regression with robust variance was employed (p < 0.05). RESULTS: The prevalence of sleep bruxism was 32.4%. Most parents (64.2%) did not know the meaning of bruxism. In the final Poisson regression model, child's gender (PR 1.32; 95% CI 1.06-1.66) and restless sleep (PR 1.39; 95% CI 1.12-1.72) were significantly associated with sleep bruxism. CONCLUSION: The prevalence of sleep bruxism was high and was associated with gender and having restless sleep. Most parents/guardians did not know the meaning of bruxism.

Carbon dioxide and water vapor exchange in a warm temperate grassland.

Grasslands cover about 40% of the ice-free global terrestrial surface, but their contribution to local and regional water and carbon fluxes and sensitivity to climatic perturbations such as drought remains uncertain. Here, we assess the direction and magnitude of net ecosystem carbon exchange (NEE) and its components, ecosystem carbon assimilation ( A(c)) and ecosystem respiration ( R(E)), in a southeastern United States grassland ecosystem subject to periodic drought and harvest using a combination of eddy-covariance measurements and model calculations. We modeled A(c) and evapotranspiration (ET) using a big-leaf canopy scheme in conjunction with ecophysiological and radiative transfer principles, and applied the model to assess the sensitivity of NEE and ET to soil moisture dynamics and rapid excursions in leaf area index (LAI) following grass harvesting. Model results closely match eddy-covariance flux estimations on daily, and longer, time steps. Both model calculations and eddy-covariance estimates suggest that the grassland became a net source of carbon to the atmosphere immediately following the harvest, but a rapid recovery in LAI maintained a marginal carbon sink during summer. However, when integrated over the year, this grassland ecosystem was a net C source (97 g C m(-2) a(-1)) due to a minor imbalance between large A(c) (-1,202 g C m(-2) a(-1)) and R(E) (1,299 g C m(-2) a(-1)) fluxes. Mild drought conditions during the measurement period resulted in many instances of low soil moisture (theta<0.2 m(3)m(-3)), which influenced A(c) and thereby NEE by decreasing stomatal conductance. For this experiment, low theta had minor impact on R(E). Thus, stomatal limitations to A(c) were the primary reason that this grassland was a net C source. In the absence of soil moisture limitations, model calculations suggest a net C sink of -65 g C m(-2) a(-1) assuming the LAI dynamics and physiological properties are unaltered. These results, and the results of other studies, suggest that perturbations to the hydrologic cycle are key determinants of C cycling in grassland ecosystems.