Abstract: Objective To study the positional relationship between the incisive canal and the maxillary central incisors, in order to provide reference for clinical treatment and subsequent research. Methods Seventysix adults undergoing orthodontic treatment were selected. Three measurement levels were defined on the CBCT image, and the measurement level paralleling to PP plane included:nasopalatine foramen level (N), root tip level (R), incisive foramen level (I). The following measuring projects were defined, the N level incisive canal lip side alveolar bone plate thickness (NT), R level incisive canal lip side alveolar bone plate thickness (RT), I level incisive canal lip side alveolar bone plate thickness (IT), N level incisive canal width (NW), R level incisive canal width (RW), I level incisive canal width (IW), the maxillary central incisor apex distance (RR), R level UR1 to incisive canal distance (RRD), R level UL1 to incisive canal distance RLD, I level UR1 to incisive canal distance (IRD), I level UL1 to incisive canal distance (ILD). The above projects were measured on CBCT images and the results were statistically analyzed. Results RRD was g reater than IRD, RLD was greater than ILD, and the difference was statistically significant (P<0.05). There was no significant difference between RRD and RLD, IRD and ILD (P>0.05). NW was less than RW; RW was less than IW, and there was a statistical difference (P<0.05). NT was greater than RT, with a statistical difference (P<0.05). There was no significant difference between NT and IT (P>0.05). There was no significant difference between RT and IT (P>0.05). Conclusion The average distance from the root tip of U1 to the incisive canal is only 3.5 mm, while the Ilevel average distance from the root of the U1 to the incisive canal is only 2.4 mm. It should be noted that the retraction of the maxillary anterior teeth may lead to the absorption of the root apex and the lateral side of the root. When the retraction of the maxillary anterior teeth is especially matched with the intrusion movement, attention should be paid to the possibility of the absorption of the mesial surface of the roots.

Key words: incisive canal, maxillary central incisors, maxillary anterior teeth retraction, cone beam computed tomography