Retrospective cone-beam computed tomography evaluation of temporary anchorage devices

Miniscrew implants as temporary anchorage devices (TADs) are becoming more popular in orthodontic treatment. Their ease of use allows orthodontists to place them in locations in the mouth that are convenient for orthodontic treatment mechanics. The aims of this study were to evaluate the location of TADs placed during orthodontic treatment and to relate the placement to the surrounding dentoalveolar structures.

Three-dimensional cone-beam computed tomography scans were taken before and after placement of the TADs over a 6-month period as part of routine clinical protocol. The following parameters were recorded: placement site, length of the TAD in the alveolar bone, amount of contact with the periodontal ligament, and interroot distance between TADs.

Thirty-five TADs (19 in the maxilla, 16 in the mandible) were evaluated. The mean lengths of the TADs in alveolar bone were 5.29 +/- 1.39 mm in the maxilla and 4.60 +/- 0.86 mm in the mandible. The amounts of contact with the periodontal ligaments were 2.54 +/- 0.81 mm (n = 13) in the maxilla and 2.72 +/- 0.49 mm (n = 10) in the mandible. The interroot distance measurements were 2.78 +/- 0.76 mm (n = 15) and 5.19 +/- 4.42 mm (n = 16) in the maxilla and the mandible, respectively. Paired t tests indicated a significant difference in the interroot distance for mandibular teeth.

Three-dimensional cone-beam computed tomography technology allows better visualization of TAD placement. Clinicians can expect 71.2% of the length of the screw section of the TAD to be embedded in the alveolar bone; the percentage is often higher in the maxilla than in the mandible. Of the 35 TADs, 65.2% were in contact with the periodontal ligament. There appears to be more space for TAD placement in the mandible than in the maxilla.