Objective To ostimate the distribution of microorganism strains isolated from hospital ward cir-curmstanee and clinical specimens, and then proceed to inquire into their interrelation to nosocomial infection, provi-ding evidence for preventing and reducing nosocomial infection. Methods Specimens were collected from hospital circumstance and each clinical laboratory, and then made a bacterial identification and pathogen strains survey. Re-sults There was a closed correlation between the microorganism strain isolated from hospital circumstance and clini-cal infection pathogen(86%). Conclusion A series of disinfection management measures should be made and for-mulated so as to reduce the hospital infection rate as far as possible.

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 investigate the effective endodontic irrigation protocols on smear layer removal from curved canals. Methods Forty extracted mandibular first molars with curved mesial root canal were selected and decoronat-ed. Mesiobuccal root canal was instrumented to F3 using handed ProTaper system, and randomly divided into four groups ac-cording to final irrigation protocols: syringe irrigation (group A), #30K file agitation (group B), passive ultrasonic irrigation (PUI, group C) and combination of #30K file agitation and PUI (group D). The ultrasonic file was located within 0.5 mm coro-nal from start of the curvature. All root canals were mesio-distally split, snicked at the start of the curvature and 2 mm apical-ly from the start of the curvature, and divided into three sections. They wereⅠ,ⅡandⅢfrom coronal to apical. The smear layer of each section of root canal was examined under scanning electron microscope (SEM). Results Group D presented small amounts of scattered or thin smear layers and obtained the lowest score at each section of root canal wall. At sectionⅠandⅡ, there was no significant difference in smear layer score between group D and group C. The smear layer scores were both significantly lower in group D and group C than those of group A and group B (P<0.05). At sectionⅢ, the smear layer score was significantly lower in group D than that of group A, group B and group C, and which was significantly lower in group B and group C than that of group A (P<0.05). Conclusion When ultrasonic file was located coronal from the start of the curvature, K file, which was the same size as dimension of apical portion preparation to agitate and PUI can remove smear layer from curved canals efficiently.

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.