Confocal laser scanning microscopic studies on alveolar bone remodeling with orthodontic tooth movement and retention

Alveolar bone reconstruction in growing dog during the retention period following orthodontic tooth movement was studied. Three beagle dogs (8-10 kg body weight, about one-year-old) were used and two of the animals were subjected to histological observation. The upper 2nd and lower 3rd premolars on both sides were extracted prior to the orthodontic treatments. After a healing period of one month, the upper 3rd premolar and the lower 4th premolar on the right side were moved mesially with a conventional orthodontic force for 8 weeks, and then retained in their new position for 4 weeks. The contralateral corresponding premolars were used as control. The alveolar bone was double-labeled with tetracycline (TC) during the movement and calcein (Cal) during the retention period. Alveolar bone structure and labeling patterns were examined by contact microradiography, conventional fluorescence microscopy, and confocal laser scanning microscopy (CLSM). Optimizing the separation of TC and Cal labelings in the alveolar bone was attained by the simultaneous use of ultraviolet (364 nm) and argon (488 nm) laser sources for excitation of TC and Cal, respectively. Cal labeling, indicative of new bone deposition showed two distinct patterns: lamination at the periodontal surface and rings circumscribing the vascular canal. The cementum surface also exhibited active deposition during the experimental period. Bone formation was affected by slight changes in magnitude and direction of orthodontic or occlusal forces. CLSM is valuable in deciphering the process of alveolar bone remodeling.