[Consideration to the experimental study on the rapid palatal expansion in the rat].

The purpose of this study is to clarify the most suitable position and method to investigate bone formation in the mid-palatal suture after rapid palatal expansion in the rat. 10 of 8 week-old Wistar rats were employed to observe the structure of the normal mid-palatal suture at the line connecting the incisors, the anterior end of the anterior palatine foramen, the line bisecting the anterior palatine foramina, and the line of the 1st molars. A mid-palatal suture of 8 week-old Wistar rats was expanded laterally for 6 days by means of maxillary incisor expansion apparatus with a spring of 60 g load. After beheading, soft X-ray picture of the skull was taken to observe the suture. The maxilla was removed and decalcified sections (frontal section) were prepared. They were stained with hematoxylin and eosin for microscopy. The mid-palatal suture was observed at 4 levels to the lines drawn as follows; the line running through the centers of incisors (A), the line running the anterior ends of the anterior palatine foramen (B), the line running through the center of the anterior palatine foramen (C), and the line running through the centers of the 1st molars (D). At the opposing margins of A and B, the suture was composed of two layers; the layer of osteoblasts and the layer of interconnecting Sharpey's fibers. At C, the suture was curved and the layer of Sharpey's fibers were made up with longitudinal as well as transverse fibers.(ABSTRACT TRUNCATED AT 250 WORDS)