[Research on cone-beam CT of mandibular foramen location in children aged 7-10 years]

Objective: Cone-beam CT (CBCT) images were used to investigate the relative position changes of mandibular foramen in the mandible of children and the relative position relationship with the occlusal plane, so as to provide clinical guidance for inferior alveolar nerve block (IANB) anesthesia of children. Methods: The CBCT data of 202 children aged 7-10 years in the image database of the First Affiliated Hospital of Zhengzhou University from March 2021 to February 2023 were included. Patients were divided into 4 groups according to age diffrences as 7-year-old, 8-year-old, 9-year-old and 10-year-old. There were 20 males and 22 females in the 7-year-old group, 31 males and 28 females in the 8-year-old group, 30 males and 26 females in the 9-year-old group, and 22 males and 23 females in the 10-year-old group, respectively. Forty-six adults aged 25-30 years were selected as control group, 24 males and 22 females included. The distance between the center point of mandibular foramen with the anterior edge of ascending ramus of mandible (MF-A), the posterior edge of the ascending ramus of mandible (MF-P) and the shortest distance between the center point of mandibular foramen with occlusal plane (MF-OP) were measured. The angle between the center point of the mandibular foramen with the sagittal plane of the mandibular first deciduous molar (or mandibular first premolar) and mandibular second deciduous molar (or mandibular second premolar) (∠A) was measured. The data of mandibular foramen were compared between the left and right sides and among different genders and different age groups. Results: The position of mandibular foramen in children aged 7-10 years maintained bilateral symmetry, and mandibular growth and development were relatively consistent between different genders (P>0.05). MF-A increased with age, from (15.83±1.28) mm in 7-year-old group to (17.10±1.60) mm in 10-year-old group gradually. There were significant differences in MF-A between the 10-year-old group with the 7-year-old group, the 8-year-old group [(15.98±1.53) mm] and the 9-year-old group [(16.43±1.49) mm] respectively (P<0.05). MF-P increased with age, from (9.12±1.17) mm in 7-year-old group to (11.25±1.60) mm in 10-year-old group. There were statistically significant differences in MF-P among all age groups (P<0.05). MF-OP increased with age, from below the plane (-0.24±2.31) mm in the 7-year-old group to above the plane (1.08±1.95) mm in the 10-year-old group. There were significant differences between the 10-year-old group with the 7-year-old group, the 8-year-old group [(-0.01±1.93) mm], and the 9-year-old group [(0.31±1.95) mm] (P<0.05). The ratio of MF-A to MF-P decreased as the age increased, from 1.77±0.30 in the 7-year-old group to 1.55±0.29 in the 10-year-old group. There were statistically significant differences in MF-A/MF-P among all age groups (P<0.05), except for between the 8-year-old group (1.66±0.19) and the 9-year-old group (1.65±0.28) (P>0.05). The ∠A of children in all age groups was significantly greater than the reference value (45°) (P<0.05), and there was no statistical significance among all groups (P>0.05). The differences of MF-A, MF-P, MF-OP, MF-A/MF-P and ∠A between children of all age groups and the control group were statistically significant (P<0.05). Conclusions: In children aged 7-10 years, the mandibular foramen is located behind the midpoint of the anteroposterior diameter of the mandibular ramus. With the increase of age, the mandibular foramen gradually moves from below the occlusal plane to above, and is flush with the occlusal plane at the age of 8 years. Compared with adults, the mandibular foramen in children is more backward and lower on the medial side of the mandibular ramus. When IANB is operated to children, the syringe can be moved distally from the contact area of the contralateral deciduous molars or premolars, so that the injection angle can be greater than the reference value 45° to improve the accuracy of IANB.