Dentoalveolar response during distraction osteogenesis in a rat model

Abstract

In distraction osteogenesis, incremental traction of osteotomized bone edges is used to induce growth of new bone and other adjacent tissues such as gingival, skin, and muscle. This study evaluated histological periodontal changes in the surrounding distraction area to establish a rat model with an optimal distraction protocol. Nineteen left hemi-mandibles of Sprague-Dawley rats were osteotomized. Groups were as follows: Group 1, control group without mandible osteotomy; Group 2, sham group with mandibular osteotomy but without distraction device fixation; Group 3, experimental group with mandibular osteotomy, and mandibular distraction procedure. After 5 days of latency phase, 12 days of distraction phase was followed at a rate of 0.20 mm per day. The consolidation phase was 4 weeks. Distracted distance was measured on CT images obtained immediately after completing the latency period (T0), distraction period (T1), and consolidation period (T2) to confirm long edges were actually separated if the distracted gap was successfully maintained during consolidation. After the T1 and T2 periods all subjects were sacrificed for histological samples. A total of 2.4 mm was considered as the expected distracted length. However, at the and of T1 and T2, the actual lengths, obtained from the reference points in the micro-CT images, were 2.02 mm and 1.88 mm, respectively. Histologically, new bone formation occurred in shame and experimental groups. Endochondral ossification was observed at the center of distraction gap during the distraction period, while intramembranous ossification was predominant until the fourth week of consolidation. The root resorption with dentin extension observed in the experimental groups was partially repaired during the consolidation period by formation of a thicker layer of cementum. This model can be applied to various conditions and treatments related to distraction osteogenesis. However, considering that the effect of distraction osteogenesis on root resorption was located on the osteotomy line, surgical procedures should be minimized to reduce negative alveolar bone response.