Positional and ultrastructural changes in peripheral pulp capillaries correlate with the active phase of dentin deposition and mineralization in rat molars

Abstract

ObjectivesThe mechanisms regulating positional and ultrastructural changes in peripheral pulp capillaries during dentinogenesis have yet to be fully elucidated. This study aimed to clarify the relationship between the spatiotemporal localization and ultrastructure of peripheral capillaries and the dentin deposition and mineralization rate. MethodsMaxillary first molars of 5- to 100-day-old Wistar rats were collected and prepared for transmission electron microscopy. The animals who had received multiple injections of lead disodium ethylenediaminetetraacetic acid were analyzed for dentin deposition rate. Non-demineralized maxillae were examined with an electron probe micro analyzer. ResultsThe dentin deposition rate at the coronal position where dentinogenesis began on day 5 reached a peak during days 10–30, gradually decreased, and ceased on day 60. The mineral content of enamel was low on day 10 (the secretory stage of amelogenesis), drastically increased on day 15 (the maturation stage of amelogenesis), and reached a maximum and persisted until day 30. The dentin underneath the maturing enamel exhibited a synchronous increase in mineral content. The distance between the mineralization front and peripheral capillaries remained almost constant, suggesting that the positional changes of capillaries into the odontoblast layer were not due to migration of capillaries but could be attributed to an increase in the height of the odontoblast layer. Endothelial fenestrations became prominent in the most active phase of dentin deposition and mineralization. ConclusionsThese results indicate that the positional and ultrastructural changes in peripheral capillaries correlate with the active phase of dentin deposition and mineralization.