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 transfect human osteoprotegerin( o pg) gene into Cos-7 cells.Methods:The primers were designed b ased on the human opg cDNA sequence,total mRNA was isolated from 293 cells and RT-PCR was performed.The fragment of opg cDNA was inserted into pSecTag 2/B vector and sequenced by automatic sequence analyzer. The recombined plasmid was transfected into Cos-7 cells by Lipofectamine 2000 and OPG protein expressi on in Cos-7 cells was determined by immunohistochemistry and Western blot. Results:The sequence of opg cDNA from 293 cells obtained by RT- PCR was identical to the sequence provided by GenBank [gi:33878056]. The fragm ents of the recombinant plasmid digested with Hind Ⅲ,EcoR I and BamH Ⅰ and exa mined by 10 g/L agarose electrophoresis were consistent with predicted size.OPG over-expressing Cos-7 cells was selected and confirmed by immunohistochemistry and Western blot.Conclusion:Human opg gene may be transfect ed into Cos-7 cells.

Objective:To study the relationship between genetic diversity within S.mutans and dental caries.Methods:Isolates of S.mutans were obtained from 10 caries active children and their mothers,and were originally isolated on mitis-salivarious-bacitracin agar.A total of 800 isolates were biochemically confirmed as S.mutans.Chromosomal DNA was extracted from those isolates with an extraction kit.By AP-PCR,the genetic diversities of S.mutans were examined respectively in 10 caries active children,10 caries-free children,and their mothers.DNA fingerprints were obtained by electrophoresis on 15 g/L agarose gel and analyzed for genotypics similarities.Results:The number of distinct genotypes of S.mutans harbored in caries active children were,on average,greater than that presented in children without caries(P

AIM The purpose of this study was to investigate the effect of immunosuppression on the periapical inflammation by estimating the expression of the cytokine IL-1? and TNF-? in periapical lesion of rat. METHODS Sixteen SD rats received cycolophosphamide injection weekly before pulp exposure for three weeks, another 16 animals received no medication as control group. The expressions of IL-1? and TNF-? mRNA in periapical lesion were detected by methods of in situ hybridization,and semi-quantified analyzed compared with control group. RESULTS IL-1? and TNF-? mRNA expressions in treated group increased progressively from 1 to 3 week, and declined somewhat at 4 week. There was a statistically significant positive correlation between the area of the periapical lesion and the number of positive stained cell for IL-1? and TNF-?(IL-1?:r=0 881,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.

Objective: To estalish a rat model system in which periapical lesions were induced by pulp exposure and infection from the oral environment. Methods: The pulps of mandibular molar of 16 SD rats were surgically exposed and kept open to be induced for infection from the oral environment. The rats were killed 1, 2, 3, 4 weeks after operation respectively. Radiographic image analysis was performed by means of computer linked to a video image digital analysis system. In addition, specimens were decalicified, sectioned, HE stained and examined under microscope. Results: Periapical lesions were readily detectable as early as 1 week after pulp exposure. A significant increase in lesion area was detected from 1 to 3 weeks in a time-dependent manner, the lesion declined a little bit in 4 weeks. Slight inflammatory cell infiltration and alveolar bone resorption were observed in the periapical tissue in the 1-week-samples, total pulp necrosis in the 2-week-samples, apical abscess and bone destruction in the 3-week-samples. Decreased infiltration and the matured osteoblasts were found on the surface of the bone in the 4-week-samples. Conclusion: Pulp exposure can induce periapical lesion in rat. A period of rapid lesion development occurs between day 7 and day 21 after pulp exposure (active phase), and a period of slower development follows thereafter (chronic phase).

Objective:To observe the accuracy of electronic method(EM), handing method(HM) and X-raying method(X-RM) in measuring root canal working length. Methods:Total 31 root canal in vivo were measured with HM, X-RM and EM(by the electronic apical locators-Root ZX and Raypex-5 respectively), and the data were compared with the actual root canal working lengths which were obtained from the sectional view's constrictions of the extracted teeth by magnifying glass. Results:Accuracy of working length measured by Raypex-5 was 93.55%, Root ZX was 87.10%, HM was 35.48%, and X-RM was 48.39%. Significantly statistical differences (P