Histological evaluation of osseous defects combined with orthodontic tooth movement

The aim of this study was to histologically evaluate the effectiveness of different times of initiating orthodontic tooth movement on enhancement of bone formation in surgical bony defects.

In 18 male guinea pigs, 3-4 months of age, a bony defect was created in the alveolar process midway between the central incisor and mandibular 1st molar. These bony defects were implanted with bioactive glass particles and collagen membrane. According to the application of the orthodontic tooth movement, the animals were divided into three groups, each comprised of six guinea pigs. In Group I, the orthodontic tooth movement was initiated immediately after the surgical procedure. In Group II, the orthodontic tooth movement was applied 2 weeks after the surgical procedure, while in Group III no orthodontic tooth movement was applied. Section blocks for histology were made at 1, 3 and 6 weeks after the surgical procedure.

All experimental sites showed active bone formation with plump osteoblast and osteoid matrix deposition in the treated area. In Groups I and II a dense fibrous tissue formation and highly cellular coarse bone were seen at six weeks. The histomorphometric analysis showed that Group I revealed the greatest number of newly formed trabeculae: 2.4, 6.4 and 8.6 at 1, 3 and 6 weeks, respectively. In addition, Group I defects revealed a greater total surface area of newly formed bone than Groups I and III: 2.96 mm2 at the end of the study period.

The combined orthodontic/regenerative therapy seemed to enhance the process of bone formation. Bone formation was histologically observed in all test groups. Defects treated with immediate application of orthodontic tooth movement showed a statistically significant increase in trabecular count and total surface area of newly formed bone than the other experimental groups.