[Morphological changes of vascular network of the midpalatal suture and palate mucosa after rapid maxillary expansion].

Rapid maxillary expansion has been utilized for years in the treatment of transverse maxillomandibular discrepancies. It is important to understand the changes of the vascular network in midpalatal suture following rapid maxillary expansion. The reason is because it is critical to maintain the blood supply and circulation for the osteogenesis and bone remodeling after the expansion. The purpose of this study was to examine the morphological changes in the vascular network of the palate regions following rapid maxillary expansion. A total of 30 dogs were divided into 6 groups of 5 dogs each, of which one group was used as a control. A skeleton type rapid maxillary expansion appliance was utilized in the 5 experimental groups. Transverse expansion was accomplished by activating the appliances 0.4 mm each day for 10 days, achieving a total of 4.0 mm of width increase. The animals were sacrificed and injected with acrylic resin through the maxillary artery at 3, 7, 14, 21 and 28 days. The thin sections were examined with a light microscope and fine vascular corrosion specimens were examined with a scanning electron microscope. The results were as follows: 1. Vascular network in the midpalatal suture. 1) The suture appeared as an interdigitating bony processes separated by a relatively narrow gap. The blood vessels were running in the direction from the posterior to anterior in the control. 2) 3 days after the expansion, the suture had separated. The hemorrhage which accompanied the expansion was not observed, though hyperemia and enlargement of the blood vessels were observed. The stretched blood vessels from the bone walls observed along the stretched fiber bundles were remarkable. A few new blood vessels were observed in various places in the bone walls. 3) 7 and 14 days after the expansion, the number of new blood vessels increased significantly and anastomosed. The tube-shaped new bone formation was observed in parts of the bone walls along the stretched fiber bundles and surrounding the blood vessels. 4) 21 days after the expansion, the sutural area was filled by new bone and the new blood vessels were embedded in the bone and the number of those had decreased. The new bone had thickened and joined in various ways. 5) 28 days after the expansion, the number of blood vessels decreased further and the bone formation was more progressed than the 21 day group. Those new bones had matured respectively. 2. Vascular network in the palate mucosa.(ABSTRACT TRUNCATED AT 400 WORDS)