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Objective To investigate the effects of root canal preparation treated by endodontists of different levels in different difficulty associated with the root canal anatomy factors. Methods Totally 422 teeth with 901 root canals were randomly selected from the Conservative Dentistry Department, West China Stomatology Hospital, and these teeth were respectively treated by junior specialist postgraduates, senior specialist postgraduates and endodontic specialists. Grading criteria of root canal risk factor and root canal therapy difficulty assessment were found based on 6 items: Tooth type, working length, root curvature, calcification, number of canals, and the previous endodontic treatment. The effects of root canal preparation with different difficulty in different groups were analyzed with RxC Chi-square test. Results Success rates of root canal preparation in junior group and senior group during three difficulty groups were statistically different (P<0.05), and the root canal therapy difficulty group I >group II > group HI. The operator factors in root canal therapy difficulty group I and group II were not significantly different (P>0.05). But in root canal therapy difficulty group DI, the endodontic specialist group have highest success rate in root canal preparation. Conclusion The cases of root canal treatment should be treated by endodontist of corres-ponding level according to the difficulty. In difficult cases, endodontic specialist can provide better root canal prepa-ration result. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effects of root canal preparation treated by endodontists of different levels in different difficulty associated with the root canal anatomy factors., Methods: Totally 422 teeth with 901 root canals were randomly selected from the Conservative Dentistry Department, West China Stomatology Hospital, and these teeth were respectively treated by junior specialist postgraduates, senior specialist postgraduates and endodontic specialists. Grading criteria of root canal risk factor and root canal therapy difficulty assessment were found based on 6 items: Tooth type, working length, root curvature, calcification, number of canals, and the previous endodontic treatment. The effects of root canal preparation with different difficulty in different groups were analyzed with RxC Chi-square test., Results: Success rates of root canal preparation in junior group and senior group during three difficulty groups were statistically different (P < 0.05), and the root canal therapy difficulty group I > group II > group III. The operator factors in root canal therapy difficulty group I and group II were not significantly different P > 0.05). But in root canal therapy difficulty group III, the endodontic specialist group have highest success rate in root canal preparation., Conclusion: The cases of root canal treatment should be treated by endodontist of corresponding level according to the difficulty. In difficult cases, endodontic specialist can provide better root canal preparation result.

Objective: To evaluate the antibacterial efficacy of KaVo KEY laser on Enterococcus faecalis (E. faecalis) within infected root canals and roots surface in vitro., Methods: Fifty single-rooted teeth were selected, and infected root canals and roots surface vitro models were prepared. Then, these specimens were divided into three groups. First group were untreated as blank control. The other two groups were the laser groups: Irradiated 15 s and 30 s respectively with 80 mJ and 140 mJ in root canals and on roots surface. Microbiological samples were collected from root canals and roots surface at two time points (before irrigation and immediately after irrigation). The dentin chips from three different zone of part of root canals in each group were immediately collected and were cultured for 24 h in brain heart infusion (BHI)., Results: The number of E. faecalis in root canal and root surface in each of the groups were effectively reduced (P < 0.05), and there was no significant difference between each two groups (P > 0.05). Compared with the blank control, the bacterial number in 100 microm of dental tubules decreased after specimens treated with 80 mJ, and the experimental group irradiated 15 s was a significant decease (P < 0.05). The other groups were no changed in different zone of dental tubules., Conclusion: KaVo KEY laser is effective on sterilizing infected root canals and roots surface. It has also significant effect on bacterial in superficial dental tubules with low energy and short time.

Objective: To investigate the anatomic feature of the canal isthmus of mandibular permanent incisors by Micro-CT., Methods: Thirty-three mandibular permanent incisors with two canals were selected through the radiograph in proximal view. These teeth were then scanned using Micro-CT and reconstructed. The scanning layer thickness was 20 microm. We observed the apical 6 mm of the 33 roots, and 300 sections were gained each tooth, giving a total of 9900 sections. The numbers of canals at each level in the apical 6 mm were recorded. The numbers of sections showing isthmuses at each level of the root canals were recorded too. Data were analyzed using the Chi-square statistic to test the null hypothesis that location of the sections in each of the apical 6 mm and presence of the isthmus were independent. The minimum root canal wall thickness was measured in each of the apical 6 mm of the roots., Results: Isthmuses were found to be present at all levels with prevalence from 10.0% to 85.5%. The Chi-square test indicated a significant difference in the distribution of isthmuses with section (P = 0.0O1). The incidence of isthmuses was higher at the apical 3-6 mm level, and the highest incidence (85.5%) was at 5 mm level. There were many more sections containing complete isthmuses (49.7%) than those containing partial isthmuses (4.5%). The thickness of the minimum root canal was less than 0.5 mm., Conclusion: The mandibular incisors have a high incidence of isthmus and are narrow in proximal direction. Debridement of the isthmus is a major challenge during surgical and nonsurgical root canal treatment.