3D quantification of in vivo orthodontic tooth movement in rats by means of micro-computed tomography

(1) To test the accuracy of split-mouth models in rats for the study of orthodontic tooth movement (OTM) and (2) to propose an improved 3D model for quantification of OTM in rats.

Eleven Wistar rats were split into group 1 (dental anchorage) and group 2 (skeletal anchorage). In both groups, no orthodontic force (OF) was applied on the contralateral hemi-maxilla. In vivo micro-CT images were taken before (T0) and 31 days (T1) after OF. OTM was compared between time-points and experimental sides using conventional 2D analysis and a novel 3D model.

Using incisors as anchorage leads to their distal displacement in both OF and no OF sides. In the OF side, movement of M1 is underestimated by incisor displacement. Mesial displacement of M1 was found in the no OF side of all groups 31 days after the application of OF.

The new 3D model yielded higher sensitivity for tooth displacement in planes other than sagittal and incisor displacement was reduced by using skeletal anchorage.

Studies following split-mouth designs in orthodontic research in rats might be systematically underestimating the effects of techniques and/or medication on OTM, since there is tooth displacement on the control side. 3D quantification of OTM with skeletal anchorage is more sensitive and avoids displacement of the dental units used as anchorage.