Objective To investigate the characteristics of posterior tooth fracture and the risk factors preliminarily. Methods Analysis relevant indicators of cases that were diagnosed as posterior tooth fracture clinically and with X-ray from Department of Endodontic of Stomatological Hospital of Jiangsu Province during Sep. 2009 to Sep. 2011. Results 252 tooth（premolars 57 and molars 195）of 252 cases（males 130 and females 122）were involved. The numbers of people of 18～44、45～59 and ＞60 age group were close to each other(82，90，80). The fracture of posterior teeth most occurred on the maxillary first molar (88/252), and least on the mandibular first premolar (2/252). The numbers of crown fracture, root fracture and crown-root fracture were 89, 19 and 144 respectively. 53.97% cases clearly mentioned a history of biting hard objects. The number of the teeth with vital pulp was more than the teeth after root canal treatment (RCT) (P<0.05). Conclusion Molars and teeth with vital pulp took up high proportions of fracture, and fracture often involved crowns and with a history of biting hard objects. No significant relationship between gender, age and tooth fracture was found.

Abstract：Objective To elucidate the ability of porphyrmonas gingivalis (P.g) to modulate the expression of chemotatic factor interleukin-8 (IL-8) and the chemotactic function in human umbilical vein endothelial cells (HUVEC）. Methods The model of infection of HUVEC by P.g was established in vitro. HUVEC were infected with either Pg381 or Pg33277, then the expression of IL-8 in supernatant was tested by ELISA. Results The expression of IL-8 was signicantly upregualted in Pg381-infected and Pg33277-infected HUVEC at 6h and 24h（P＜0.01）. The upregualtion effect of Pg381 was significantly greater than Pg33277at 24h（P＜0.01）. Conclusions These data demonstrate that the infection of Pg can increase the expression of IL-8 and chemotactic function of HUVEC, which may be related to the development of AS.

[Abstract] Through the review in recent years methods of maxillary premolar root canal of anatomical configuration. Understanding of maxillary premolar root canal anatomical configuration and its root canal variations ，To provide theoretical support clinical research and treatment.