Analysis of Apical Foramen and Root Canal Morphology in Maxillary Lateral Incisor Using Micro-CT

Abstract

 Purpose: The maxillary lateral incisor is considered as a type of tooth, but it is difficult to treat because the prognosis after root canal filling is poor. Effective treatment is also difficult because, even though it is a single-rooted canal anterior tooth, it is curved in the distal direction or in the lingual direction near the root apex. Recently, µ-CT has been introduced, which enables three-dimensional observation without destroying the specimen, and it is frequently used for the study of internal structure. In the present study, we performed a study on maxillary lateral incisors by using µ-CT.
 Materials and methods: Fifty human extracted maxillary lateral incisors with no dental caries were used. Based on images obtained by three-dimensional structuring, we observed the morphology of the apical foramen and apical constriction, and also the positional relation between the root apex and pulp chamber.
 Results: The distance from the root apex to the physiological apical foramen was 1.9mm at maximum and 0.2 mm at minimum, and 0.7 mm on average. The difference between the apical foramen and the center of the anatomical apical foramen was 0.55 mm when observed from the mesiodistal direction and 0.37 mm when observed from the labiolingual direction. Observation of the apical constriction showed apparent constriction on 22 teeth when seen from the mesiodistal direction and on 17 teeth when seen from the labiolingual direction. Also, extreme variation was found in the positional relation between the root apex and the upper end of the pulp chamber. Access lines to facilitate insertion of a file, crossing on the labial side, were found on 43 teeth, and a cutting margin was seen in 7 teeth.
 Conclusion: The results of the present experiments revealed that it is necessary to secure access lines to facilitate insertion of the file. Furthermore, it was clarified that the morphology of the root apex and file operation on the root apex side are complex. Because the root canal of maxillary lateral incisors is highly varied, sufficient anatomical knowledge and careful operation of instruments are required.