A comparative light microscopic study of human midpalatal suture and periodontal ligament

In order to provide information on the morphological features of both human midpalatal suture and periodontal ligament, bioptic samples were obtained from patients whose age was between 10 and 30 years. The samples were embedded in epoxy resin, sectioned, stained with toluidine blue and observed by light microscopy. The periodontal ligament and the midpalatal suture appeared very similar with regard to the histological characteristics of the connective tissue but differed in the nature of the bone tissue associated to it. The alveolar bone lining the periodontal ligament was a bundle bone whereas the bone lining the connective tissue of the sutures was both lamellar and bundle bone. The absence of osteoblasts, osteoclasts or undifferentiated cells in the sutures under examination suggests that they are subjected to a slow bone turnover during their life cycle. On the contrary, the presence of mesenchymal cells in the periodontal ligament supports the notion that these cells are precursors of osteogenic cells involved in the high rate of bone remodelling that characterizes the alveolar bundle bone. The present results are discussed taking into account physiologic and therapeutic aspects of the two structures under examination.