| Distraction osteogenesis (DO), which was first used mainly to lengthen long bones, has a history of nearly 100 years. Since Snyder completed the first experimental study of mandibular distraction osteogenesis in 1973, it has been widely used in the correction of craniofacial deformities. In 1996, Chin and Toth and Block et al described the technique of alveolar ridge distraction, DO presented to be an alternative method for alveolar ridge augmentation. Compared with conventional techniques, it can not only correct severe alveolar bone defects, but also elongate the soft tissues such as muscle, vessel, nerve and skin simultaneously. A number of distraction devices are commercially available, which mainly include distraction implants, distraction screws. But there still exist defects in all the devices above such as: semi-buried, easily infection of residual wounds, uncomfortable and foreign body in patient's mouth, and so on.Titanium Nickel shape memory alloy (TiNi-SMA) has fine shape-memory function, biomechanical capability and biocompatibility. In this study, we developed a new completed-buried, self-activated distraction device with TiNi-SMA, established an experimental canine model for alveolar ridgeaugmentation using TiNi-SMA distractor, evaluated the quality of the augmented alveolar ridge, and tried to insert endosseous implants in the new bone. There are four parts in our study:Part 1: Height measurement of mandibular posterior area and the design of TiNi-SMA distractorObjective: To provide a quantity index for alveolar ridge augmentation at mandibular posterior area and to design a simple distractor with TiNi-SMA.Methods: The height of different points of mandibular posterior area was measured on panoramic radiographs of 90 patients and 89 adult mandibles.Results: (1)The height between superior margin of mental foramen and alveolar ridge crest, on panoramic radiographs, dentulous side 15.91±1.85mm, edentulous side 9.07±2.48mm, difference of mean value 6.84mm; on mandibles, dentulous side 13.95±2.45mm, edentulous side 8.77±2.75mm, difference of mean value 5.18mm. (2)Mandibular body height at mental foramen area, on panoramic radiographs, dentulous side 33.64±2.69mm, edentulous side 23.65±4.28mm, difference of mean value 9.99mm; on mandibles, dentulous side 31.65±3.09mm, edentulous side 24.67±3.88mm, difference of mean value 6.98mm. (3)Mandibular body height at posterior area, on panoramic radiographs, dentulous side 30.68±2.76mm, edentulous side 20.96±4.15mm, difference of mean value 9.72mm; on mandibles, dentulous side 29.15±2.91mm, edentulous side 23.03±4.11mm,difference of mean value 6.12mm.Conclusion: The mean loss of bone at mandibular posterior area is 6-10mm, which should be referrible for alveolar ridge augmentation andTiNi-SMA is suitable for making distractor.Part 2: Establishment of an experimental model for alveolar ridge augmentation by distraction osteogenesis & selection of osteotomy methodsObjective: To establish an animal model in canines for alveolar ridge augmentation at mandibular posterior area by distraction osteogenesis and to select the suitable osteotomy method.Methods: All of the mandibular premolars and the first molar were extracted from four adult mongrel canines. One-month later, partial or full-cutting box-shaped osteotomies of the alveolar bone were carried out and TiNi-SMA distractors were buried. The bone height was measured and the radiographs were taken before and 1, 5, 13 weeks after the operation. The animals were killed at one or three months after distraction and histological examination was taken.Results: The transport segments were lifted up immediately after the distractors inserted and the height achieved 7.5-11.5mm one week after the operation. One month after distraction, the radiographs showed the regenerating bone in distraction gap. The new bone and the normal bone could not be differentiated clearly three months after distraction. No bone resorption was found obviously during this period. In histological sections, there...
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