AIM: The aim of the present study is to investigate changes of five biochemical markers of bone turnover during the formation of ovariectomized rat model. METHODS: Three-month-old female SD rats were divided randomly into ovariectomized (OVX) group, sham-operated (sham) group and control group. Five biochemical markers of bone turnover levels, including serum osteocalcin (OC), total alkaline phosphatase (ALP), bone-specific alkaline phosphatase (BALP), tartrate-resistant acid phosphatase (TRAP) and hydroxyproline (HYP) were measured before and at 1, 1.5, 2, 2.5, 3 and 4 months after surgery. The right proximal tibias of rats were excised at the same time point for histopathological observation. RESULTS: Serum OC, ALP, BALP, TRAP and HYP levels in OVX group were significantly higher than that in sham group. As regard to the time of peak level arrived, the sequence of changes was as follows: TRAP/HYP→OC→ALP/BALP. There was a significant positive correlation between five markers. The pathological changes of trabecular bone in OVX group were only observed 3 months after surgery. CONCLUSION: The results suggest that postmenopausal osteoporosis has a high bone turnover rate. During the formation of ovariectomized rat model, changes of bone resorption markers precede changes of bone formation markers. Serum OC, ALP, BALP, TRAP and HYP are sensitive to evaluate the bone loss in the earlier stage of postmenopausal osteoporosis.

Objective: To evaluate the caries status of a cohort of 3-year-old caries-free children from 2 kindergartens in Beijing in a period of 2 years by using Cariostat caries activity test and to assess the sensitivity and specificity of Cariostat score as a caries risk indicator for caries-free children. Methods: Totally 426 3-year-old caries-free children from 2 kindergartens in Beijing were recruited in the present study. Informed consents were obtained from the children's parents. Dental plaque samples of the children were collected and the Cariostat caries activity tests were conducted at baseline and once a year for 2 years. After two years, the caries status of the cohort children were re-evaluated and the caries incidences amongst children with high (2.0, 2.5, 3.0), medium (1.5) and low (1.0, 0.5, 0.0) levels of Cariostat scores were compared and analyzed. Results: Totally 864 3-year-old children from 2 kindergartens were screened before the study startedand 426 (49.3%) children were caries free. After 2-year follow-up, 312 out of 426 (73.2%) remained in the study. The overall caries incident rate was 46.5% (145/312). The caries incident rate of children with high level of Cariostat scores was 88.9% (88/99), while the caries incident rates of children with medium and low levels of Cariostat scores was 38.7% (36/93) and 17.5% (21/120), respectively. The sensitivity and specificity of the Cariostat test in assessing the caries risk of 3-year-old caries-free children in a period of 2 years were 60.7% and 93.4%, respectively. Conclusions Cariostat caries activity test can be used as an indicator to predict the caries risk of 3-year-old caries-free children. Comprehensive caries management could be conducted for children in kindergartens based on the caries risk assessment results of caries experience and the Cariostat score.