Objective:To survey the relation of different vertical skeletal facial type and the third molar agenesis.Methods:The vertical face type of 207 subjects was divided into high angle(n=45),average angle(n=99)and low angle(n=63)groups by the assessments of MP-SN angle.The assessment of the third molar was made from panoramic radiographs,then the third molar agenesis rate of different vertical skeletal facial types was analysed.Chi-square criterion examination was conducted with SPSS 17.0 software. Results:In the high angle group,whether in the maxillary or mandibular,unilateral or bilateral,the absent percentage of third molar was higher than that in low angle group(P<0.05).In the females the bilateral maxillary third molar absent percentage was higher than in the males(P<0.05).The absent percentage of maxillary third molar was higher than that of the mandibular third molar(P<0.05).Conclusion:The third molar absence depends on vertical skeletal facial type.The absent percentage of third molar in the in-dividuals with high angle type is higher than that in those with low angle type(P<0.05).

Objective To study the influence of local administration of Icariin on orthodontically induced inflammatory root resorption (OIIRR ).Methods After rat models of orthodontic root movement were successfully established,rats were injected with 200 mg/kg Icariin (Icariin group)or saline (positive control group), respectively.Left maxillary served as the negative control group.The resorption pit of root surface was measured using scanning electron microscopy (SEM), HE staining, and tartrate resistant acid phosphatase (TRAP ). Results The level of TRAP positive cells and root resorption score in Icariin group were significantly lower than those in the positive control group (P < 0.05 ).Each measured value differed significantly between thenegative control group and the positive control group (P <0.05).The level of TRAP positive cells was significantly different (P <0.05),while root resorption scores did not differ between Icariin group and the negative control group (P >0.05).Conclusion Local administration of Icariin may reduce the degree of orthodontically induced resorption.