[Application of micro-lecture in standardized training of endodontic residents].

PURPOSE: To apply micro-lecture in standardized training of endodontic residents, in order to improve training quality. METHODS: Twenty endodontic residents were randomly divided into 2 groups, 10 students in each group. One group were taught with micro-lecture while the other group with lecture-based learning (LBL). The teaching effect was measured with examination and questionnaire survey. The examination results were analyzed by Student's t test using SPSS 18.0 software package. RESULTS: Micro-lecture group was better than LBL group in practical test and total scores, there were significant differences between the two groups (P＜0.05). Micro-lecture group was better than LBL group in didactic test, but there was no significant difference between the two groups (P＞0.05). Questionnaire survey showed that micro-lecture was well accepted by residents for its novelty and flexibility, self-motivated learning ability was trained, communication between teachers and residents was enhanced, but the production level of micro-lecture video needs to be improved. CONCLUSIONS: Micro-lecture achieves satisfactory teaching effect, and can be applied in standardized training of endodontic residents.

[Effects of Porphyromonas endodontalis lipopolysaccharides on the expression of monocyte chemotactic protein-1 in mouse osteoblasts].

PURPOSE: To investigate the effects of lipopolysaccharide (LPS) extracted from Porphyromonas endodontalis (P.endodontalis) on expression of monocyte chemotactic protein-1 (MCP-1) mRNA and protein in MC3T3-E1 cells and the role of p38 mitogen-activated　protein　kinase (MAPK) and nuclear factor-kB(NF-kB）in the process. METHODS: MC3T3-E1 cells were treated with different concentrations of P.endodontalis LPS(0-50mg/L) and 20 mg/L P.endodontalis LPS for different hours (0-48 h). The expression of MCP-1 mRNA was detected by real-time reverse transcription PCR(RT-PCR) and protein was detected by enzyme-1inked immunosorbent assay (ELISA). MC3T3-E1 cells were pretreated with SB203580 (inhibitor of p38MAPK) and BAY11-7082 (inhibitor of NF-kB) for 1h, and then were treated with 20 mg/L P.endodontalis LPS for 24 h, the expression of MCP-1 mRNA was also detected by RT-PCR. Statistical analysis was performed using one-way ANOVA and Dunnett t test with SPSS 13.0 software package. RESULTS: The level of MCP-1 mRNA and protein increased significantly after treatment with different concentrations of P.endodontalis LPS (0-50 mg/L), which indicated that P.endodontalis LPS induced osteoblasts to express MCP-1 in a dose dependent manners. During the observation time (0-48 h), the impact of 20 mg/L P.endodontalis LPS on induction of MCP-1 in MC3T3-E1 cells exhibited a time-dependent manner. The expression of MCP-1 mRNA decreased significantly after pretreated with 10 mol/L SB203580 and BAY11-7082 for 1 h,and the inhibitory effect of SB203580 was stronger than BAY11-7082. CONCLUSIONS: P.endodontalis LPS may induce the expression of MCP-1 mRNA and protein in MC3T3-E1 cells through the signaling pathway of p38MAPK and NF-kB.

[Application of PBL combined with SP method in during-course practice of endodontics for undergraduate dental students].

PURPOSE: To apply problem-based learning (PBL) combined with standardized patients(SP) in during-course practice of endodontics for undergraduate dental students, in order to improve the teaching quality. METHODS: One hundred and four undergraduate dental students of China Medical University School of Stomatology were randomly divided into 2 groups, 52 students in each group. One group were taught with PBL combined with SP while the other group with lecture-based learning (LBL) alone. The teaching effect was measured with examination and questionnaire survey. The data were analyzed by Student's t test using SPSS 11.5 software package. RESULTS: Students in PBL combined with SP group was better than LBL group in case analysis, didactic tests, practical tests and total scores, and there was significant difference between the two groups (P<0.05). LBL group was better than PBL combined with SP group in basic theoretical knowledge scores, and there was significant difference between the two groups (P<0.05). SP and PBL combined with SP method were welcomed by undergraduate dental students. CONCLUSIONS: The abilities of undergraduate dental students can be improved by PBL combined with SP in different aspects. PBL combined with SP achieves satisfactory teaching effect, and can be applied in during-course practice of endodontics to undergraduate dental students.

[Application of problem-based learning in pre-job training of postgraduate students in department of endodontics].

PURPOSE: To apply problem-based learning (PBL) in pre-job training of postgraduate students in department of endodontics. METHODS: Thirty master degree postgraduate students of China Medical University were randomly divided into 2 groups, there were 15 students in each group. One group were taught with PBL method while the other group with lecture-based learning (LBL) method. The teaching effect was measured with examination and questionnaire survey. The data were analyzed by student's t-test using SPSS 11.5 software package. RESULTS: There was no significant difference in basic knowledge, medical records writing, oral examination between the two groups (P>0.05). There were significant differences in case analysis, dental operation, theory examination, practical examination and total scores between the two groups (P<0.05). The PBL method was welcomed by master degree postgraduate students. CONCLUSIONS: The abilities of postgraduate students can be developed by PBL method in different aspects. PBL achieves satisfactory teaching effect, and can be applied in pre-job training of postgraduate students.

[Effect of Carisolv on endodontic microleakage].

PURPOSE: To evaluate the effect of Carisolv on endodontic microleakage by establishing a fluid transport model using sodium nitrite as tracer. METHODS: Seventy extracted teeth were randomly divided into 5 groups, all the root canals were prepared with different chemical reagents, including Carisolv,3% hydrogen peroxide+ 2%tosylchloramide sodium,2.5% sodium hypochlorite,5% sodium hypochlorite(negative control)and distilled water(positive control),post spaces were prepared after cold lateral condensation, the samples were put on the model, concentration of sodium nitrite which penetrated from the coronal to the apical end was measured by diazo reaction at 1,2,4,7,10,15,20,25,30,35,40,45,50,55 and 60 day. The data were analyzed by ANOVA using SPSS 11.5 software package. RESULTS: Sodium nitrite was not detected in negative control group from 1 day to 60 days. High concentration of sodium nitrite was detected in positive control group at first day, concentration of sodium nitrite was higher than that of other four groups from 1day to 60 days(P<0.01). Concentration of sodium nitrite in Carisolv group was significantly lower than that of 3%hydrogen peroxide+ 2% tosylchloramide sodium group(P<0.01), also lower than that of 2.5% sodium hypochlorite group(P<0.05),except at 25,30,35 and 40 days. CONCLUSIONS: Carisolv can remove the smear layer, decrease the endodontic microleakage, seal the root canal better. The fluid transport model using sodium nitrite as tracer can be used to evaluate the endodontic microleakage objectively,sensitively and exactly.

[Effect of Carisolv on root canal cleanness in chemomechanical preparation].

PURPOSE: To evaluate the effect of Carisolv as chemical reagent on root canal cleanness in chemomechanical preparation. METHODS: Sixty extracted teeth which were dyed with methylene blue were randomly divided into 3 groups, different chemical reagents were applied in different groups. The optical density of methylene blue in irrigating solution were measured with UV-VIS spectrophotomer after preparation with each file, the root canal cleanness was evaluated under SEM. Two-way ANOVA and Kruskal-Wallis H test in SPSS 11.5 software package were used for statistical analysis. RESULTS: There were significant differences in the optical density between the root canals treated with Carisolv and those with 2% tosylchloramide sodium plus 3% hydrogen peroxide (P<0.05), no significant difference was found in optical density between the root canals treated with Carisolv and those with 2.5% sodium hypochlorite (P>0.05). The results of SEM were consistent with those of the optical density of methylene blue. CONCLUSIONS: As a chemical reagent, the cleaning ability of Carisolv was as effective as 2.5% sodium hypochlorite. Carisolv can remove the smear layer and debris, without causing excessive demineralization. Supported by Key Research Project of Science and Technology Committee of Liaoning Province(Grant No.00225001).

[Study of the relative factors of cure depths of light curing composite resin].

PURPOSE: To investigate the effect of different composite resin, different light curing units, different irradiation time, different irradiation distance on cure depths of light curing composite resin. METHODS: Designed by factorial experiment, 192 Cylindrical samples were made with 4mm internal diameter and 6mm high mold. The whole samples were scanned by Planmeca ProMax panoramic X-ray unit, cure depths were measured using a scoping method described in the ISO standard for resin-based composites. The data was statistically analyzed by SPSS11.5 software package for ANOVA. RESULTS: The differences of four factors-composite resin, light curing units, irradiation time, irradiation distance were significant (P<0.01), and the effects between-subjects were involved among four factors (P<0.01). CONCLUSIONS: From this study, we conclude that cure depths may be affected by two kinds of light curing units, two kinds of composite resin, four kinds of irradiation time and four kinds of irradiation distances, once each factor is strengthened, cure depths could reach a more ideal effect. Supported by Key Research Project of Science and Technology Committee of Liaoning Province (Grant No.00225001).