Histological Alterations from Condyle Repositioning with Functional Appliances in Rats.

OBJECTIVE: This study was designed to assess the morphological and histological alterations of the condyle of rats undergoing forward mandibular repositioning via functional appliance. MATERIALS AND METHODS: Functional appliances were mounted onto the upper jaws of rats. Morphological analysis was conducted on micro-CT images of sacrificed animals. Histological changes in condyle were examined by immunohistochemistry using proliferating cell nuclear antigen (PCNA), matrix metalloproteases (MMPs), vascular endothelial growth factor (VEGF), tissue inhibitors of matrix metalloproteinases (TIMP-1), interleukin 1b (IL-1ß), Aggrecan and Type II collagen. Osteoclast activity was identified by tartrate-resistant acid phosphatase (TRAP) staining. RESULTS: Morphological analysis confirmed the forward positioning of the condyles of rats by the appliance, but the position gradually returned to normal on days 14 after treatment. An increase in PCNA positive cells was observed in the posterior region of the condyles on days 7, whereas PCNA positive cells decreased in the anterior region. Aggrecan and Type II collagen localization increased in the posterior region throughout the entire period, but decreased in the anterior region on days 14. In both regions, IL-1ß and VEGF localization was significantly increased for 14 days while MMPs localization was evident throughout the entire period. The TRAP positive cells were significantly elevated on days 3 and 7. CONCLUSIONS: These results suggest that the functional appliance therapy induces significant morphological and histological changes in the anterior and posterior regions of the condyle and subsequently causes adaptive cellular functions such as chondrocyte differentiation and cartilage matrix formation.

Localization of ODAM, PCNA, and CK14 in regenerating junctional epithelium during orthodontic tooth movement in rats.

OBJECTIVE: To identify the regenerating junctional epithelium (JE) during orthodontic tooth movement in rats. MATERIALS AND METHODS: Closed-coil springs were used to create a 20 g mesial force to the maxillary first molars. On days 1, 3, 7, 10, and 14 after force application, histologic changes in JE were examined by immunohistochemistry using proliferating cell nuclear antigen (PCNA), odontogenic ameloblast-associated protein (ODAM), and cytokeratin 14 (CK14). RESULTS: On day 1, JE was destroyed and lost attachment to the tooth surface. Cell division activity was rarely observed in JE, and ODAM localization was weakly detected in damaged JE. By day 3, regenerating JE had not fully recovered. High cell proliferation activity and CK14 expression started to appear in most basal cells of JE. ODAM expression was reduced and appeared in a small area. By day 7, JE had almost recovered. Cell proliferation activity was still observed in several basal cells of JE, and ODAM expression was detected among JE cells. CK14 was hardly observed in JE except in the basal cells. By days 10 and 14, regenerated JE appeared. ODAM, PCNA, and CK14 expression was similar to that of the control. CONCLUSIONS: Damaged JE might recover rapidly during orthodontic tooth movement because basal cells of the remaining JE, which show higher proliferation activity, are involved in JE regeneration. Reduced ODAM expression during proliferation of JE cells may increase again after JE regeneration is complete. Therefore, ODAM may be associated with the normal function of JE.