Micro-anatomical responses in periodontal complexes of mice to calibrated orthodontic forces on the crown.

Abstract

Correlating mechanical forces with quantifiable physical changes in the dentoalveolar complex. Male 6-week C57BL/6 mice (N=3), micro X-ray-computed tomography; post-analysis software to extract physical changes in periodontal ligament (PDL)-space. Silicone-elastic bands were placed between maxillary molars for 1week, with the contralateral side as internal control. Average displacements between crowns and roots, and changes in PDL-spaces were evaluated by registering X-ray tomograms of experimental and control hemi-maxillae. Histology illustrated mineral formation and resorption-related events within narrowed and widened volumes of the PDL-space. 3D maps of changes in PDL-space between molars illustrated coronal and root displacements of 640μm and 180μm, respectively, compared to 70μm in controls. Orthodontic tooth movement (OTM) specimens exhibited an average net change of -20μm in narrowed and +30μm in widened PDL-spaces. Bone and cementum were affected by the force on molars, and primary cementum was more affected than secondary cementum. This novel approach illustrates the importance of 3D-imaging and analysing 3D alveolar socket subjected to OTM otherwise omitted by 2D micrographs.A measured force on the crown elicits a response related to narrowed and widened regions in the 3D complex. OTM that exceeds PDL-space can illicit biological responses that attempt to restore physiologic PDL-space via remodelling of the periodontium. Regenerated weaker bone due to aseptic inflammation caused by orthodontics could leave patients at a higher risk of bone loss or root resorption if they later develop periodontitis, a form of septic inflammation.