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.