COLLAGEN FIBRILS IN THE ODONTOBLAST LAYER OF THE RAT INCISOR BY SCANNING ELECTRON-MICROSCOPY USING THE MACERATION METHOD

Background: There is not universal agreement on the existence of the e xtracellular pathway from the pulp along the odontoblast layer to the predentin. Method: To confirm this pathway, the architecture of collag en fibrils in the rat incisor dentin and pulp, especially in the odont oblast layer of the lateral (periodontal ligament) sides of the tooth, was demonstrated in the present investigation using scanning electron microscopy of the maceration method for collagen networks. Results: N umerous collagen bundles were observed in the odontoblast layer in the mature odontoblast region which, except for the young odontoblast reg ion, comprises the major portion of the incisor. The collagen bundles went from the pulp, through the odontoblast layer, and were woven into the collagen network of the predentin. The meshwork structure was com posed of fine secondary fibrils among these collagen bundles. The surf ace of the predentin contained many oval-shaped holes which were surro unded by collagen fibrils. Fracturing the dentin longitudinally relati ve to the dentinal tubules revealed that the arrangement of the collag en fibrils at the surface of the tubules was either circular or obliqu e. In the young odontoblast region, i.e., the thin portion from the ap ical end of the incisor where the mineralization of the dentin does no t occur and where the height of the odontoblasts was less than 30 mu m , many thick bundles composed of thick collagen fibrils ran straight f rom the pulp to the predentin through the odontoblast layer and fanned out into the collagen network of the predentin. These thick bundles m ight correspond to the so-called ''von Korff fibers.'' The distributio n of collagen fibrils in the pulp was random except on the surface of the blood vessels where the fibrils comprised two sheets of collagen: the inner sheet which coursed longitudinally to the long axis of the v essel, and the outer sheet which ran transversely. Conclusion: It was considered that the fluid in the pulp could flow to the predentin alon g the collagen fibrils through the tight junction between the odontobl asts. (C) 1994 Wiley-Liss, Inc.