An investigation of the histologic and radiographic changes that occur after the surgical separation and the orthodontic expansion of the midpalatal suture in the adult cat

Abstract

Although rapid palatal expansion is an accepted treatment procedure for the growing child, it is often difficult to expand the midpalatal suture in an adult (36,49,53,85,86, 97,107,132,135). As a consequence, the mature patient with a posterior skeletal crossbite is treated to a compromise result via tooth tipping (56, 57,132). A more logical (and possibly more stable) treatment would be one that is aimed at the correction of the skeletal disharmony. It was the purpose of this investigation to analyze the histologic adjustments and radiographic changes that occur during the orthodontic-surgical expansion of the midpalatal suture in an adult cat. Five cats ranging in age from two and one-half to three years were obtained for this study. In the three experimental animals a midline incision was made into the palatal mucosa. After reflecting this tissue, a small round surgical bur was used to open the suture along its entire length. The incision was closed with nonabsorbable suture material. Immediately after surgery, a hygienic maxillary expansion appliance was cemented onto the cuspids and third bicuspids bilaterally. The jackscrew was activated 13-16 one-quarter turns within five minutes. A cat was sacrificed three weeks, five weeks and nine weeks after surgery and expansion. The control was sacrificed in order to analyze the normal histologic appearance of the palatal sutures in the adult cat. The maxillary hard palate was separated from the skull and sectioned transversely into four blocks. Each block was decalcified, embedded in paraffin and sectioned coronally at eight micra. Alternate cut sections were stained with haematoxylin and eosin and trichome. Before and after study models and occlusal x-rays were also obtained for the purpose of qualitative analysis. The results of this study demonstrated that the midpalatal suture of a fully mature cat may be expanded a significant amount within only a few minutes after the suture has been surgically separated. The histologic response noted was similar to previous studies which dealt with conventional palatal expansion. Therefore, it appeared that the addition of surgery to rapid palatal expansion did not have a deleterious effect on the healing response. Although a considerable amount of new bone was observed along the sutural margins after nine weeks of retention, it was obvious that a longer period of time is necessary for the midpalatal suture to return to normal. Further studies should investigate the long term results of this procedure.