Intermittent posterior displacement of the rat mandible in the growth period affects the condylar cancellous bone.

OBJECTIVE

To examine whether intermittent posterior condylar displacement causes changes in cancellous bone in the mandibular condyle during the growth period.

MATERIALS AND

METHODS

Sixteen 5-week-old male Wistar rats were divided into experimental and control groups. In the experimental group, an appliance was attached to the maxillary incisors to induce posterior displacement of the condyles in the occluded condition. Untreated rats served as the control group. Animals were sacrificed at 14 days, and the condyles were removed to analyze the three-dimensional cancellous bone structure by microcomputed tomography (micro-CT). Serial sagittal paraffin sections of the condyles were used for hematoxylin and eosin staining to investigate histomorphological changes and for tartrate-resistant acid phosphatase (TRAP) staining to identify osteoclastic cells.

RESULTS

Micro-CT analysis showed that in the experimental group, the bone volume fraction and the degree of anisotropy were significantly decreased compared with those in the control group in the anterior region of the condyle. Moreover, the number of TRAP-positive cells was significantly greater in the same region in the experimental group than in the control group.

CONCLUSION

Intermittent posterior displacement of the mandible can cause region-specific changes in the profile and microarchitecture of the condylar cancellous bone.