Tooth anatomy risk factors influencing root canal working length accessibility / 国际口腔科学杂志·英文版

The aim of this study was to analyze the specific influence of root canal anatomy on the accessibility of working length during root canal therapy. Four hundred seventy-six root canal therapy cases (amounting to a total of 1 005 root canals) were examined. The anatomy risk factors assessed in each case included: tooth type (tooth location), root canal curvature, and root canal calcification, as well as endodontic retreatment. The investigation examined the correlation between each of these anatomic factors and the working length, with statistical analysis consisting of Chi-square tests and multiple logistic regression analysis. In an independent factor analysis, tooth type (tooth location), root canal curvature, canal calcification, and endodontic retreatment were determined to be the primary risk factors. In a multiple-factor regression model, root curvature and canal calcification were found to most significantly influence root canal working length accessibility (P<0.05). Root canal anatomy increases the difficulty of root canal preparation. Appropriate consideration of tooth anatomy will assist in accurate determination of preparation difficulty before instrumentation. This study alerts clinical therapists to anatomical factors influencing the working length accessibility, and allows for a direct estimate of success rate given in situ measurements of tooth factors during the root canal treatment procedure.

The clinical analysis on the effects of different difficulty in root canal preparation / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of root canal preparation treated by endodontists of different levels in different difficulty associated with the root canal anatomy factors.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>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.</p>

Anatomic study of canal isthmuses of mandibular permanent incisors by micro-CT / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the anatomic feature of the canal isthmus of mandibular permanent incisors by Micro-CT.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>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.</p>

The antibacterial efficacy of KaVo KEY laser on Enterococcus faecalis within infected root canals and roots surface in vitro / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the antibacterial efficacy of KaVo KEY laser on Enterococcus faecalis (E. faecalis) within infected root canals and roots surface in vitro.</p><p><b>METHODS</b>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).</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>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.</p>