Intraoral widening and lengthening of the mandible in baboons by distraction osteogenesis

The purpose of this study was to analyze the skeletal and dental positional changes and histomorphology of the distraction regenerates and mucogingival periosteal tissues that occurred after simultaneous widening and bilateral lengthening of the mandible in baboons by a miniaturized intraoral bone-borne distraction appliance.

Distraction appliances were activated 5 days after vertical ramus and symphyseal osteotomies at a rate of 0.9 mm/d for 10 days. The appliances were then stabilized for 8 weeks, after which the animals were killed. The distraction gaps and gingival tissues were analyzed clinically, histologically, and by standardized radiographic studies.

Positional changes of the canines and incisor apices were proportional to the skeletal movements. Tipping of both incisors toward the center of the distraction gap was observed. Proportionate movement of the superior and inferior portion of the distracted segments was noted. Newly formed longitudinal trabecular columns parallel to the vector of distraction originated from the intact margins of alveolar bone contiguous with the adjacent teeth. Active histogenesis occurred in the stretched mucogingival periosteal tissues located in the distraction gaps.

The results of this investigation support the clinical use of the miniaturized intraoral bone-borne distraction appliance to selectively widen and lengthen the mandible. The orientation of the mandibular distractors must be parallel to the common vector of distraction, which should be parallel to the maxillary occlusal plane. The formation of a bone regenerate in the alveolar region depends on the presence of an adequate bone interface on either side of the distraction gap.