The use of intra-osseous versus extra-osseous distraction devices in atrophic mandibles.

To allow for implant placement in severe atrophic edentulous mandibles, distraction osteogenesis can be used to gain sufficient bone height. The efficacy of extra-osseous and intra-osseous devices is evaluated. In this retrospective study, 45 patients treated with an extra-osseous device (EOD) were compared with 43 patients treated with an intra-osseous device (IOD). From a statistical point of view, both patient groups were comparable for age and sex ratio. The IOD group gained more bone height (9.8 mm) than the EOD group (6.0mm). A significantly higher degree of backward tilting of the device was observed in the EOD group (12.1°), compared with the IOD group (3.0°). There were also significantly more fractures of the basal bone segment and sensory disturbances of the chin area in the EOD group than in the IOD group. The IOD group scored significantly better on bone height gained, backward tilting of the device, occurrence of fractures, and postoperative sensory disturbances. Despite the fact that the mean preoperative bone height for the IOD group was substantially higher (18.6mm) than for the EOD group (11.9 mm), it may be concluded that for augmentation procedures of the edentulous mandible, the IOD is more favourable.

[Sagittal splitting with screw fixation in patients with mesial bite wearing dentures--planning surgery and prosthetic design]. / Die sagittale Spaltung mit Verschraubung bei progenen Prothesenträgern--Operations- und Prothesenplanung.

In fully or partially edentulous patients with mesial bite undergoing surgical correction, the possibilities for avoiding intermaxillary fixation were studied. For stable osteosynthesis of mandibular osteotomies preoperative prostheses are needed in these patients to keep the jaws in their proper relation during surgery. This requires cephalic adjustment of the maxillary cast and articular adjustment of the mandibular cast in the articulator. The mandibular cast is shifted along an aluminum wedge designed to match the inclination of the occlusal plane until the alveolar rests are in proper relation to one another. If the occlusal plane is neglected, uncontrollable tilting of the mandible may occur. This may favor relapses. As Slavicek (1984) showed the mean inclination of the occlusal plane relative to the hinge axis-orbital plane to be 12.87 degrees (scatter 5.99 degrees) with dorsal convergence in 1,213 patients, 3 aluminium wedges with different inclinations were designed. These are suited for 92.5% of all cases with tolerances of +/- 3 degrees. Mandibular casts are pasted to geometric paper and shifted along the aluminium wedge to the desired position; the distance they are shifted is read from the paper. This distance is transferred to the teleradiograph and the changes in profile are checked. Preoperatively, prostheses can then be tailored to match the desired alveolar crest relation. During surgery, these prostheses serve as splints for setting the mandible as designed in the model. The osteotomy fragments are then screwed together transbuccally with miniscrews and clawed washers. The latter provide for a firm seat of the traction screws in the mandible at a safe distance from the mandibular canal. Postoperative intermaxillary fixation can thus be avoided.