[Experimental study of growth and development of the dentofacial complex in the rat. Influence of anterior displacement of mandible].

The purpose of this study was to detect the influence on the growth and development of the maxillofacial cranium due to anterior crossbite in early childhood. The author observed the morphological changes of the maxillofacial cranium of rats in which of mandible was induced anterior crossbite artificially. Experimental animals used in this study were closed colony bred Wistar Crj rats. A total of 106 rats consisting of 65 in the experimental group and 41 in the control group were used. In the experiment, the appliance which was applied to the mandibular incisors of rats aged 30 days to induce anterior crossbite. X-ray photos of the head were taken in lateral and parietal at the age of 30, 60, 90 and 120 days and the soft X-ray photo of the right mandible isolated by sacrificing and decapitation of several animals at the respective ages. 1. The experimental rats have a tendency to lose weight in accordance with the appliance. The increase rate of weight in experimental group is similar to that in the control group and it was estimated that the appliance affected their weights a little. 2. The lateral cephalometric observation 1) The tip of the nasal bone was modified upwards in its position with advancing age. 2) In the mandibular angular region an inhibition of posterior growth was observed. 3) The dental arch length of maxilla was shorter and of mandibular was longer. 4) The molar changed its position upward, and the height of the upper facial region including the tooth and facial height had a lowering tendency. 3. The parietal cephalometric observation Parietal head X-ray photo showed a widening tendency of the width of anterior facial cranium and the anterior tip of zygomatic arch.