Objective To evaluate the effects of calcitonin and 1, 25 vitamin D on the bone loss in experimental periodontitis in rats. Methods A total of 125 male Wistar rats were randomly allocated to five groups according to the treatments during 8 weeks: normal control (group A, n=25), periodontitis(group B, n=25), calcitonin (group C, prepared in sterile saline at 2 mg/L, and 2μg/kg was administered daily, s.c. , n=25), 1,25 vitamin D (group D, prepared in corn oil daily at a concentration of 2 mg/L, and 2μg/kg was administered daily, p.o. , n=25), 1,25 vitamin D plus calcitonin (group E, n=25). The experimental model of periodontitis was induced by ligating floss around mandibular first molars with orthodontic wires in B,C,D and E groups. Five rats from each group were sacrificed, and the specimens were prepared at 2, 4, 6 and 8-week. The probing depth (PD) and alveolar bone level were observed. The serum bone-specific alkaline phosphatase (BALP) and osteocalcin (OC) were measured by enzyme-linked immunosorbent assay (ELISA) at 8-week in each group. Results The values of PD were significantly lower after 4, 6 and 8 weeks in E group than those of B, C and D groups (P＜0.05). The alveolar bone loss was significantly lower after 6 and 8 weeks in group E compared with that of B, C and D groups (P＜0.05). The serum levels of BALP and OC were significantly higher after 8 weeks in E group than those of B, C and D groups (P＜0.05). Conclusion The present study suggests that 1, 25 vitamin D and calcitonin can partially inhibit the alveolar bone loss induced by periodontitis. Especially, the application of both is more effective than either drug treatment alone.

Objective To evaluate the effects of root canal cleanliness on the fracture resistance of roots filled with AH-Plus. Methods Eighty single canal premolars were instrumented using step-back technique, then were randomly di-vided into four groups (n=20 for each group). Group A was washed with distilled water for 10 min, group B1 was washed with 5%EDTA for 1 min, group B2 was washed with 5%EDTA for 5 min and group B3 was washed with 5%EDTA for 10 min. Ten samples of each group were observed by scanning electron microscope at the coronal, middle and apical thirds to exam-ine smear layer removal. The remaining samples of each group were fixed into a electronic universal testing machine and ver-tically loaded until fracture. Results The difference of coronal and middle thirds was significant between group B3 and group B2 (P<0.05). At the middle third, there was significantly improved efficiency in smear layer removal in group B2 than that of group B1(P<0.05). The mean fracture resistance was significantly higher in group B3 (391.91±12.82)N than that of group B2 (335.54±16.14)N, group B1(296.47±17.82) N and group A (264.77±16.64)N (P<0.05). Group B2 showed a signifi-cantly better fracture resistance than that of group B1 and group A (P<0.05). Conclusion The complete removal of root ca-nal smear layer can significantly improve the fracture resistances of roots filled with AH-Plus.