A method for measuring post-extraction alveolar dimensional changes with volumetric computed tomography.

The aim of this study is to present a predictable method for evaluating dimensional changes in the alveolar ridge through cone beam computed tomography (CT). Twenty subjects with single-rooted tooth extraction indication were selected for this preliminary report, which is part of a larger ongoing investigation. After extraction, two CT scans were performed; the first within 24 hours post-extraction (TC1) and the second 6 months (TC2) later. A radiographic guide with a radiopaque element placed along the tooth axis was developed to locate the same plane of reference in two different CT scans. For each patient, backtrack analysis was performed in order to establish the reproducibility error of a predetermined point in space between two CT scans. Briefly, an anatomical landmark was selected and its coordinates to the radiopaque marker were recorded. One week later, the coordinates were followed backwards in the same CT scan to obtain the position where the reference point should be located. A similar process was carried out between two different CT scans taken 6 months apart. The distance between the anatomical reference and the obtained point of position was calculated to establish the accuracy of the method. Additionally, a novel method for evaluating dimensional changes of the alveolus after tooth extraction is presented. The backtrack analysis determined an average within-examiner discrepancy between both measurements from the same CT scan of 0.19 mm. SD +/- 0.05. With the method presented herein, a reference point in a CT scan can be accurately backtracked and located in a second CT scan taken six months later. Taken together they open the possibility of calculating dimensional changes that occur in the alveolar ridge over time, such as post-extraction alveolar resorption, or the bone volume gained after different augmentation procedures.