Reliability of measuring dentoalveolar bone using cone beam CT

Introduction: Cone beam CT(CBCT)provided clinicians with the ability to investigate bony structures Threedimensionally.The accuracy of the machine (NewTom) in identifying minute thicknesses has been argued to be dependent on the size of the voxels.The dentoalveolar plates surrounding teeth are anatomically thin and difficult to identify using cephalograms or orthopantomograms.With the 3D CBCT, such measurements were hypothesized to be achievable.This may help identifying the commonly existing bony defects such as bone dehiscence and fenestrations.

Objective: To assess the accuracy and reliability of CBCT in measuring the dentoalveolar bone thicknesses around mandibular teeth (#3.4, #4.1, #4.4).

Methods: Nine images randomly selected, the approval for the secondary analysis was granted from the ethic committee.The axial slices were taken along the long axis of teeth from the tip to the apex. The buccal and lingual plates were measured at:the apparent radiographic bone crest near CEJ, midway from the alveolar crest to the apex and at the root tip. The measurments made at a right angle to the root and repeated three times at three different instances separated by a week difference and done by the same investigator (AA).

Results: reliability of measurements was assessed at all levels.The measurements were not repeatable at the site level as well as at the surface level (buccal versus lingual).On average, the difference in repeated measurements of dentoalveolar buccal and lingual plates around mandibular teeth on CBCT images was within 0.95mm.Detailed statistical analyses is to be presented at the meeting.

Conclusions:

1) Each measurement (crestal, middle, or apical) exhibited a characteristic pattern of error which contributed to measurement inaccuracy.

2) CBCT reliability in identifying minute bony thicknesses and defects seems to be limited by the size of the voxels.

3) More resolution will improve the accuracy and precision in measuring dentoalveolar bone thickness when using cone-beam volumetric imaging.