In vivo microcomputed tomography evaluation of rat alveolar bone and root resorption during orthodontic tooth movement

Abstract

Objective: To observe the real-time microarchitecture changes of the alveolar bone and root resorption during orthodontic treatment.

Materials and methods: A 10 g force was delivered to move the maxillary left first molars mesially in twenty 10-week-old rats for 14 days. The first molar and adjacent alveolar bone were scanned using in vivo microcomputed tomography at the following time points: days 0, 3, 7, and 14. Microarchitecture parameters, including bone volume fraction, structure model index, trabecular thickness, trabecular number, and trabecular separation of alveolar bone, were measured on the compression and tension side. The total root volume was measured, and the resorption crater volume at each time point was calculated. Univariate repeated measures analysis of variance with Bonferroni corrections were performed to compare the differences in each parameter between time points with significance level at P < .05.

Results: From day 3 to day 7, bone volume fraction, structure model index, trabecular thickness, and trabecular separation decreased significantly on the compression side, but the same parameters increased significantly on the tension side from day 7 to day 14. Root resorption volume of the mesial root increased significantly on day 7 of orthodontic loading.

Conclusions: Real-time root and bone resorption during orthodontic movement can be observed in 3 dimensions using in vivo micro-CT. Alveolar bone resorption and root resorption were observed mostly in the apical third on day 7 on the compression side; bone formation was observed on day 14 on the tension side during orthodontic tooth movement.

Figure 1.

The nickel-titanium spring was ligated between the incisors and the maxillary left first molar in rats.

Figure 2.

(A) Sagittal view of selected regions of interest in the alveolar bone adjacent to the apical third of the mesial root of the maxillary left first molar. (B) Horizontal view. (C) Axial cross-section images on day 0, (D) day 3, (E) day 7, and (F) day 14 of orthodontic loading.

Figure 3.

Bone volume fraction (BV/TV), structure model index (SMI), and trabecular separation (Tb.Sp) at different time points on the compression and the tension side. Error bars indicate standard deviations. *P < .05.

Figure 4.

The mesial root divided into three regions from the root furcation to the root apex: cervical third, middle third, apical third.

Figure 5.

Reconstructed three-dimensional images of the mesial root on (A) day 0, (B) day 3, (C) day 7, and (D) day 14. White arrows indicate root lacunae. (E) Root resorption crater volume and (F) root resorption crater volume in the apical third at different time points. Error bars indicate standard deviations. *P < .05.