Abstract: BACKGROUND: Long course of treatment and second operation limit the extensive application of alveolar distraction osteogenesis, and the distractor made by magnesium alloy as a biodegradable metal material can solve the problem of soft and hard tissue defects of alveolar bone. 
Objective: To explore the feasibility of establishing an experimental dog model of vertical alveolar distraction osteogenesis using the custom-made intraosseous distractor made by magnesium alloy. 
Methods: Nine adult mongrel dogs were provided. The bilateral mandibular premolars were extracted from experimental dogs to form models of atrophic alveolar ridge. The right mandible was selected as the experimental side and the left side as the control side. After 3 months, an alveolar segmental osteotomy was carried out in the right mandible and one intraosseous vertical distractor was placed. After a 7-day latency period, the alveolar bone was augmented at a rate of 0.5 mm per times, twice a day for 6 days. After a consolidation of 3 months, the dogs were sacrificed to dissect the mandibles for clinical, X-ray, micro-CT and histological examination. The experimental side was compared with the control side.
Results AND CONCLUSION: (1) Of the nine dogs, one dog died and was replaced. The rest of the experimental dogs obtained the predicted height and the average alveolar ridge was vertically increased for 4.94 mm measured by a vernier caliper as compared with the control side. (2) The X-ray showed that the distraction gap disappeared and the bone density increased. There were obvious cracks on surfaces of the distractor. (3) Histological examination revealed active osteoblasts and trabecular bone structures, as well as partially mature bone tissue. (4) Micro-CT showed that most of trabecular bone had the same distraction direction (P < 0.05); the trabecular thickness and trabecular number slightly increased (P > 0.05), trabecular separation decreased (P < 0.05) and percentage of bone volume (P < 0.05) and bone mineral density increased (P > 0.05) in the experimental side compared with the control side. (5) It is concluded that the custom-made intraosseous distractor made by magnesium alloy can increase the height of atrophy alveolar and obtain a mature new bone, which provides a good theoretical reference for development of alveolar distractor and clinical practice of the technique.

Key words: distraction osteogenesis, distractor, magnesium alloy, degradation, dog