[The possibility of midface skeleton protraction: an experimental study in dogs]

To probe the feasibility of a new technique of sutural distraction osteogenesis for midface hypoplasia repair.

A protraction system was developed, which consisted of three parts: a rigid external framework, a bone hook, and the elastic band. Four 12-week mongreal dogs were randomly assigned into two groups: the control (n = 1) and the experimental groups (n = 3). Four pairs of titanium bone markers were fixed on either side of the bone sutures of all animals. The experimental group was fitted with a distraction device, through which a forward elastic force was exerted for 1 month. Clinical observations and X-ray examinations were performed at the beginning and the end of distraction. New bone specimens were examined histologically.

All the animals in the experimental group showed progressively forward movement of the maxilla and manifested class II occlusion at the end of the experiment. The distance increase between each pair of bone markers showed that premaxilla advancement was more than that of the maxilla. The next was zygoma. There was no obvious difference between the control and the experimental group in terms of the basilar-maxillary angle and counterclockwise rotation. Theer was active osteogenesis in the sutures, especially in premaxilla-maxillary sutures. The number of osteoblasts and fibroblasts increased dramatically and new bone formation was found at the edge of the suture.

This technique can create effective advancement of the maxilla. The direct force can avoid counterclockwise rotation of the maxilla during distraction.