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It has been reported that both vascular endothelial growth factor (VEGF) and macrophage colonystimulating factor (M-CSF) can induce osteoclast recruitment. Thus, VEGF and M-CSF are considered to be closely involved in the bone remodeling process. The purpose of this study was to evaluate changes in VEGF and M-CSF expression during orthodontic treatment. The expression of VEGF and M-CSF mRNA in osteoblasts and fibroblasts was detected by in situ hybridization during experimental tooth movement in mice. Furthermore, the canine retraction side and the control side of orthodontic patients were compared, revealing a statistically significant increase in both VEGF and M-CSF concentrations in gingival crevicular fluid. These results suggest that orthodontic tooth movement causes an increase in VEGF and M-CSF levels. These factors may induce bone remodeling via osteoclastic bone resorption.

Previous studies have indicated that an injured condyle during adolescence is a causative factor for reduced mandibular growth and resulting asymmetry of the mandible. The aim of this study was to examine the nature of mandibular growth after unilateral condylectomy and to elucidate the effects of mandibular advancement. Sixty growing mice were subjected to unilateral condylectomy, and then one-half of them underwent treatment with a functional appliance. After 4 wks, a unilateral condylectomy produced reduced growth of the mandible and a subsequent lateral shift to the affected side. However, reduced growth and a lateral shift of the mandible were eliminated by a functional appliance, and prominent regeneration of the condyle was also demonstrated. It was shown that mandibular advancement provides for the regeneration of cartilaginous tissues on injured condyles and recovery of reduced mandibular growth, leading to correction of the lateral shift of the mandible.

The present study was designed to examine the expression of Sox 9 and type II and X collagens in regenerated condyle resulting from the use of a functional appliance. Ninety, 3-week-old, mice were divided equally into the following groups: two experimental groups (condylectomy group and condylectomy with functional appliance group) and the corresponding control group. In the condylectomy group, a unilateral condylectomy was performed on the right side. In the condylectomy with appliance group, the mandible was repositioned in a forward direction using a functional appliance after unilateral condylectomy. The expression of Sox 9 and type II and X collagens in the condyle was determined immunohistochemically 4 weeks after surgery. In mice with a condylectomy, the expression was minimal. On the other hand, these factors were highly expressed in the condylectomized side with the appliance. It is thus speculated that cartilaginous regeneration is due to the expression of chondrogenic factors, such as Sox 9 and type II and X collagens. It is also suggested that condyle regeneration results from an optimal intra-articular environment with appropriate joint spaces achieved by condylar repositioning.

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