Three-Dimensional Mandibular Canal Changes in Adolescents

Objectives: Analyze mandibular canal changes in order to determine stable regions that can be used for future superimposition techniques by locating three-dimensional landmarks in the mandible using cone-beam computer tomography (CBCT) in adolescent patients.
Methods: CBCTs from fifty patients (ages 11-17 years) were used to locate anatomical landmarks in the mandible. Two CBCT reconstructions taken 1.5-2 years apart were analyzed for each patient. CBCTs were landmarked using AVIZO® and six core landmarks were placed relative to the right and left mandibular canals of each patient. Three-dimensional coordinates (x, y, z) were obtained from the landmarks. Average distances between paired landmark reference points were measured using a paired samples t-test. Mean distance differences <1.50mm were determined clinically insignificant and identified as stable regions. A reliability test was initially conducted to determine landmark position consistency. Repeat CBCTs from eleven subjects were landmarked 3 times 1 week apart to determine intra-reliability of the repeated landmarks.
Results: X and y-axis coordinates of all landmarks had an ICC of 1.00. Z-axis coordinates for landmarks had an ICC of 0.995 or higher. Measurement error was <1mm. From all the landmark pair distances measured, the largest mean distance change was 2.25mm±3.06mm between the right mandibular foramen and the landmark directly on the right canal, closest to the mesial root of the first molar. The smallest mean distance change was <0.01mm±1.7mm between the right and left mental foramina. Additionally, the bilateral mandibular foramina, bilateral distal and mesial roots of the first molar, and bilateral regions on the mandibular canal inferior to both distal and mesial roots of the first molar all had a mean distance change of <1.50mm.
Conclusions: All landmarks were determined reliable. In reference to the canal, the region between the right and left mental foramina was found most stable for this time period in adolescents.