Type III collagen is a major component of interodontoblastic fibers of the developing mouse molar root

Background: Recently, collagenous interodontoblastic fibers (IOF) were reported in some particular developmental stages and/or locations of the tooth. However, it remained unclear whether these fibers were identical to so‐called von Korff fibers. Methods: To clarify this issue, we examined the developing mouse molar by three‐dimensional reconstruction of 8 confocal images within a 6 μm‐thick section using laser scanning confocal microscopy, and confirmed our findings using immunoelectron microscopy. Results: In the root pulp during circumpulpal dentin formation, the IOF stained weakly for type I collagen, but stained strongly for type III collagen by a double‐staining technique. It could be clearly seen that many immunoreactive fibers ran spirally among the odontoblasts and entered the predentin. This distribution pattern of IOF was similar to that of the classical von Korff fibers. Furthermore, the existence of anti‐type III reactive collagen fibrils between odontoblasts was confirmed, whereas IOF were not observed in the coronal pulp during circumpulpal dentin formation. Conclusions: This study presents for the first time, immunohistochemical observations which demonstrate the presence of IOF at least during root circumpulpal dentin formation and which reveal that type III collagen is a major component of IOF. © 1994 Wiley‐Liss, Inc.