[Shaping ability of multi-taper nickel-titanium files in simulated resin curved root canal].

OBJECTIVE: To compare the shaping ability of ISO standard stainless steel K files and multi-taper ProTaper nickel-titanium files in simulated resin curved root canals. METHODS Thirty simulated resin root canals were randomly divided into three groups and prepared by stainless steel K files, hand ProTaper, rotary ProTaper, respectively. The amount of material removed from inner and outer wall and canal width after canal preparation was measured, while the canal curvature before and after canal preparation and canals aberrations were recorded. RESULTS: The stainless steel K files removed more material than hand ProTaper and rotary ProTaper at the outer side of apex and inner side of curvature (P < 0.05). The mean degree of straightening in stainless steel K files group was significantly bigger than in ProTaper group (P < 0.05). The canals prepared by ProTaper had no evident aberration. CONCLUSION: The shaping ability of ProTaper is better than stainless steel K files.

[Radiographic anatomy of pulp chamber of Chinese permanent anterior teeth].

OBJECTIVE: The aim of this study was to measure and analyze the anatomic characteristics of the pulp chamber of Chinese permanent anterior teeth radiographically. METHODS: There were 137 human permanent anterior teeth to be used. The crown length, crown width and crown thickness were measured by vernier caliper. Labial-lingual and mesial-distal radiographs were obtained by parallel technique and Photoshop 8.0 was adopted for measuring the largest labial-lingual length, the largest mesial-distal length, the pulp chamber height and the distance between the lingual surface of the crown and the corresponding wall of the pulp chamber; the ratios of the largest labial-lingual length to the crown thickness, the largest mesial-distal length to the crown width and the pulp chamber height to the crown length were calculated. Finally the coefficients of variance were caculated. RESULTS: (1) The ratios of the largest mesial-distal length to the crown width of maxillary and mandibular canines were statistically different from those of the other anterior teeth. There was not statistically significant difference for those ratios either between maxillary and mandibular canines or among incisors. (2) Indexes of the pulp chamber had higher variance than those of the external morphology. (3) The distance between the lingual surface of the crown and the corresponding wall of the pulp chamber had the smallest coefficient of variance. (4) The largest mesial-distal length of the pulp chamber had the largest coefficient of variance, except for the mandibular canines. CONCLUSION: This study provided anatomical basis for clinical work; the distance between the lingual surface of the crown and the corresponding wall of the pulp chamber could be used as a depth reference for the endodontic access, and the access should not be extended excessively in mesial-distal direction.

[Morphology of cross-sectioned root canal in Chinese mandibular permanent incisors].

OBJECTIVE: To identify morphological features of cross-sectioned root canal in Chinese mandibular permanent incisors. METHODS: Twenty mandibular permanent incisors were selected in this study. The tooth roots were embedded in resin and transversely sectioned with a low-speed diamond saw. The number of root canal and the morphology and isthmus of the root canal were observed under a stereo-microscope, which included the measure of the canal diameter. RESULTS: The double root canal comprised 22.5%, 30.0%, and 15.0% in crown third, middle third, and apical third root canals of the mandibular permanent incisors, respectively. The long oval canal comprised 44.8%, 77.0%, and 44.5% in crown third, middle third, and apical third root canals, respectively. The canal isthmus comprised 62.5%, 75.0%, and 48.7% in crown third, middle third, and apical third root canals, respectively. The diameter of buccal-lingual canal was at least 2 times of the diameter of mesial-distal canal. CONCLUSION: The cross-sectioned root canal morphology in Chinese mandibular permanent incisors varies considerably. But most have long oval and canal isthmus, which imposes a great challenge for root canal therapy.

[Difficulty assessment of root canal therapy in Chinese permanent maxillary anterior teeth].

PURPOSE: To assess the difficulty of root canal therapy in Chinese permanent maxillary anterior teeth by radiographic methods in vitro. METHODS: 80 maxillary anterior teeth including 27 maxillary central incisors, 22 maxillary lateral incisors and 31 maxillary canines were collected and X-rayed in 3 individual directions: labiopalatal projection, mesiodistal projection and the maximal angle shot. Three anatomic risk factors: root curvature, calcification and working length of root canal therapy were assessed by difficulty assessment standards and criterions. Kruskal-Wallis test was used to analyze the data. RESULTS: The results showed that the root canal therapy of 2 and 3 were significantly more difficult than 1, P < 0.05; while there was no significant difference between 2 and 3, P > 0.05. In 1, the results of difficulty assessment of root canal therapy were significantly different among 3 individual X-rays which were projected from 3 different directions (P < 0.05). The difficulty caused by root curvature was significantly greater than calcification and working length in labiopalatal X-ray in 1 (P < 0.05) and 2 (P < 0.01), while there was no significant difference among these 3 risk factors in 3 in labiopalatal projection (P > 0.05). CONCLUSIONS: The results suggest that the labiopalatal X-rays can be safely regarded as the reliable projection shot for difficulty assessment before endodontic procedures. Root curvature was by far the most important risk factor that affected the difficulty of root canal therapy in 1 and 2 while root curvature, calcification and working length played the same roles in root canal therapy of 3.