Influence of Head Position on the CBCT Accuracy in Assessment of the Proximity of the Root Apices to the Inferior Alveolar Canal.

STATEMENT OF THE PROBLEM: The most important risk factor for inferior alveolar nerve (IAN) damage is the proximity of the mandibular root apices to the alveolar canal. Failure to position the patient's head at standardized orientation during cone beam computed tomography (CBCT) scans might adversely affect the relative position of the alveolar canal and mandibular root apices with subsequent treatment failure.

PURPOSE: The purpose of the present study was to investigate the influence of the orientations of the skull during the scanning procedure on the accuracy of CBCT images in determining the positional relationship of the mandibular tooth apices to the alveolar canal.

MATERIALS AND METHOD: CBCT scans of 7 human dry skulls were obtained by using NewTom VGi CBCT in standard, tilt, flexion, extension and rotation positions of the head. The shortest radiographic distance between the mandibular tooth apices and the IAN canal of 20 points were measured on cross sectional images of CBCT in all position scans. A sample t-test was used to compare the measurements at different head position with the standard position values.

RESULTS: Significant differences were found in the measurements of normal and tilt orientations. However, there was no statistically significant difference between the measurements in standard position and other deviated positions. The mean errors in all head positions were less than 0.5mm.

CONCLUSION: Alteration of patient head positioning during CBCT scanning does not affect the relative position of the IAN and the apices of posterior teeth.