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Background Gingivitis is the most prevalent form of periodontal disease in children and adolescents, being strongly associated to some socioeconomic factors and oral health behaviours. This study aimed to assess the prevalence of gingivitis and its association with socio-demographic factors and oral health-related behaviours in children aged 12–15 years in Guangdong, Southern China. Methods A total of 7680 children were sampled using an equal-sized, stratified, multistage, random sampling method and clinically examined between December 2015 and April 2016. A questionnaire on socio-demographic factors and oral health-related behaviours related to gingivitis was completed by each of the selected children. Gingival bleeding was recorded using the Community Periodontal Index probe, and children with a gingival bleeding positive score ≥ 10% were defined as having gingivitis. A multivariate logistic regression analysis was performed to assess the association between socio-demographic factors and gingivitis. All statistical tests were performed at a two-sided significance level of 0.05. Results The weighted prevalence of gingivitis among 12–15-year-old children was 29.6%, with 22.6% having localised gingivitis and 7.0% having generalised gingivitis. Age differences were observed in the prevalence of gingivitis, whereas urban-rural differences were not. According to the multivariate logistic regression analysis results, factors such as increasing age, being the only child, lack of regular annual dental check-up, and heavy dental calculus were significantly associated with higher prevalence of gingivitis. In addition, the association of gingivitis with these factors was inconsistent among the urban and rural areas. Conclusions Dental calculus and oral health behaviour were found to be important factors for maintaining the gingival health of children aged 12–15 years in Guangdong. Maintaining gingival health in children requires promoting positive oral health behaviours and regular dental prophylaxis.

This study aimed to investigate the effects of resveratrol (RES) on bone metabolism and bone turnover related indexes in ovariectomized osteoporosis rats. 48 clean grade adult healthy unmated female SD rats were randomly divided into 6 groups, including normal control group (NCG), osteoporosis model group (OP MG), estrogen treatment group (17β-E2 group), RES low dose group (RES-L), RES medium-dose group (RES-M) and RES high dose group (RES-H). The rats in NCG and OP MG were given distilled water once a day and the rats in the other two groups were given 17β-E2 and resveratrol respectively. The levels of serum calcium (S-Ca), serum phosphorus (S-P), urinary calcium (U-Ca/Cr) and urinary phosphorus (U-P/Cr) were measured with an automatic biochemistry analyzer. The levels of serum osteocalcin (BGP), alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP), type I amino front-end peptide (PINP), type I collagen strong carboxyl peptide (CTX-I), urine deoxypyridinoline (DPD) and serum estrogen were detected by enzyme-linked immunosorbent assay (ELISA). In the OP group, the serum estrogen levels, S-Ca and S-P decreased significantly and the expression of U-Ca/Cr and U-P/Cr increased significantly (P< 0.05). Compared with the OP group, the expression of S-Ca and S-P increased significantly and the expression of U-Ca/Cr and U-P/Cr decreased significantly (p< 0.05) after treatment. The levels of TRAP, BGP, DPD and CTX-I in the OP group increased significantly (P< 0.05). Compared with the OP group, the levels of TRAP decreased significantly (P< 0.05). The levels of PINP and ALP in OP MG increased significantly (P< 0.05). IP and ALP increased in the middle and lower levels (P< 0.05). The bone mineral density of the OP group decreased significantly (P< 0.05). Resveratrol can affect the changes in bone turnover in ovariectomized rats, promote bone formation in low estrogen state and inhibit bone resorption. Resveratrol may have a protective effect on the bone of ovariectomized rats.