Effects of rhythm of distraction osteogenesi on sagittal mandibular lengthening

Objective: Frequency of activation during distraction can theoretically influence the process of distraction osteogenesis. The aim of the study is to evaluate the effect of two different frequencies of distraction in the amount and architecture of new bone using a tooth-borne distractor. Materials and Methods: Ten beagle dogs, weighing between 15-18kg, were used. Three remained as the control group and seven underwent a mandibular distraction protocol. Both hemi-mandibles were used for experimental purposes, with the following division: Group A: Six did not undergo any surgical procedure, remaining as a control group; Group B: Seven were subjected to two daily activations of 0.5 mm, with an interval of twelve hours; Group C: Seven received a single daily distraction of 1mm. After the distraction period, all devices were properly blocked and submitted to a consolidation period of 12 weeks. The mean distraction achieved was 9,8 mm. The evaluation of bone tissue was made radiographically and by Dual X-ray absorptiometry, and the values obtained were subsequently sent for statistical analysis. Results: Radiographic evaluation showed that a greater the consolidation period leads to a greater amount of bone tissue in the distraction gap. There were no statistically significant differences in bone mineral content and bone mineral density among groups A, B and C. There were statistically significant differences between the coefficient of variation in groups B and C (p=0,041). Conclusions: An increased in rhythm from one to two daily activations changed the quality of new bone present in the area created by distraction. Keywords: Distraction osteogenesis; Mandible; DEXA scan