This study was conducted to evaluate biologic responses of autogenous bone (particulate marrow and cancellous bone; PMCB) and beta-tricalcium phosphate ceramics (TCPC) to orthodontic stimuli. Nine dogs served as the experimental animals; three dogs underwent orthodontic tooth movement after grafting, three dogs received PMCB grafting without tooth movement, and three dogs received TCPC grafting without tooth movement. Immediately after extraction of the upper second and/or third incisors, the maxillary alveolar bone was resected bilaterally. Autogenous PMCB obtained from the iliac bone and TCPC were transplanted into each bone defect. Experimental tooth movement was initiated 2 to 4 weeks after the grafting and continued for 9 to 15 weeks. Sectional archwires with open-coil springs were used for distal movement of the upper first incisors into the extraction sites. Oxytetracycline and calcein were employed as bone markers. Sections of grafted areas including the teeth were prepared for light and fluorescence microscopy. The results revealed that both autogenous bone and TCPC presented similar adaptive changes to the original alveolar bone without any external stimuli. TCPC exhibited more prominent biodegradative responses to orthodontic force in association with new cementum formation. Root resorption was also less in the TCPC area than in the PMCB region. It Is shown that TCPC is biodegradative In nature and adaptive for remodeling during orthodontic tooth movement. This finding indicates that TCPC may be a better biocompatible alternative to autogenous bone transplanted into bone defects subjected to orthodontic tooth movement.

This study was conducted to investigate the nature of root resorption resulting from intrusive forces applied to the rat lower molars, by means of histological and histochemical techniques with tartrate resistant acid phosphatase (TRAP). Thirty-eight 13-week-old Wistar strain male rats were used. Intrusive force was created by a fixed appliance which was adjusted to exert an initial force of 50 g for the duration of 1, 2, and 3 weeks. The degree of root resorption and distribution of TRAP positive cells were evaluated. On the root surface, the TRAP positive scores were low in the apical regions. Significant differences in the scores were found in the inter-radicular region of the roots between the experimental and control groups for the 2- and 3-week groups. More active resorption of bone occurred during the experimental period, as denoted by greater TRAP positive scores on the bone than on the root surface. Root resorption scores in the apical root region were larger in the 2- and 3-week groups than in the 1-week group. Significant differences in the root resorption scores were also found between the 1- and 3-week groups in the inter-radicular region, indicating that intrusive force application of a longer duration may lead to a higher frequency of root resorption. It is shown that, irrespective of the level of TRAP positive cells and root resorption scores, the degree of root resorption activity is higher in the apical root region than in the inter-radicular area. These results indicate that cellular cementum may be resorbed more easily because of its richer organic components and low mineralized structure.

This study was conducted to evaluate biologic responses of autogenous bone (particulate marrow and cancellous bone; PMCB) and beta-tricalcium phosphate ceramics (TCPC) to orthodontic stimuli. Nine dogs served as the experimental animals; three dogs underwent orthodontic tooth movement after grafting, three dogs received PMCB grafting without tooth movement, and three dogs received TCPC grafting without tooth movement. Immediately after extraction of the upper second and/or third incisors, the maxillary alveolar bone was resected bilaterally. Autogenous PMCB obtained from the iliac bone and TCPC were transplanted into each bone defect. Experimental tooth movement was initiated 2 to 4 weeks after the grafting and continued for 9 to 15 weeks. Sectional archwires with open-coll springs were used for distal movement of the upper first incisors into the extraction sites. Oxytetracycline and calcein were employed as bone markers. Sections of grafted areas including the teeth were prepared for light and fluorescence microscopy. The results revealed that both autogenous bone and TCPC presented similar adaptive changes to the original alveolar bone without any external stimuli. TCPC exhibited more prominent biodegradative responses to orthodontic force in association with new cementum formation. Root resorption was also less in the TCPC area than in the PMCB region. It is shown that TCPC is biodegradative in nature and adaptive for remodeling during orthodontic tooth movement. This finding indicates that TCPC may be a better biocompatible alternative to autogenous bone transplanted into bone defects subjected to orthodontic tooth movement.