Objective:To study the effect of short exposure to high levels of fluoride on structure and the BMP-4 expression of ameloblasts of mouse molar and explore the possible formation mechanisms of dental fluorosis. Methods:32 4-day-old ICR mice were randomly divided into two groups. The experimental animals and the control animals were shared equal numbers in each group. The experimental animals were received a single intraperitoneal dose of 20 (n=8) and 10 (n=8) mg NaF/kg(body weight) respectively,equal doses of NaCl were given to the controls (n=8 for each group). The injected volume was kept constant (10 ?l/g). After 24 h all mice were sacrificed. HE and immunohistochemical stainings were used to observe the structural changes and the expression of BMP-4 in ameloblasts of mouse molar at different stages. SPSS 13.0 software package was used to analyze the data. Results:The early and late secretory/transitional ameloblasts were sensitive to a short-lasting but high dose of F-. The immunohistochemistry results demonstrated that in experimental animals,the expression of BMP-4 was weaker than that in control animals with the significant differences(P

Objective: To study the effect of short exposure to high levels of fluoride on cellular structure and the DSP expression of odontoblasts of mice molars. Methods: 32 4-day-old ICR mice were randomly divided into two groups. The experimental animals were received a single intraperitoneal dose of 20 mg(n =8) andlO(n=8) mg NaF/kg( body weight) respectively. Equal doses of NaCl were given to the controls (n = 8 for each group). The injected volume was kept constant (10 μ/g). After 24 hours all mice were sacrificed. HE staining and immunohistochemical staining were used to observe the structural changes and the expression of DSP in odontoblasts of mouse molar at different stages. SPSS 13.0 software package was used to analyze the results. Results: The secretory odontoblasts distorted and lost its normal column contour. The immunohistochemistry results demonstrated that the expression of DSP was more intense than that in control group. Results of statistics analysis showed there were significant differences between the two groups(P<0.01). No remarkable differences were found in mature odontoblasts. Conclusion: Short exposure to high concentration of fluoride can enhance the expression of DSP in the secretory odontoblasts,and inhibit differentiation of the odontoblasts and matrix secretion. This lead to the abnormal development of dentinogenesis.