Electron microscopic study on interodontoblastic collagen fibrils in amputated canine dental pulp

Location, arrangement and possible function of interodontoblastic collagen fibres in association with calcium hydroxide-induced hard tissue bridges

AIM

To assess the location, arrangement and possible function of interodontoblastic collagen fibres in association with calcium hydroxide-induced hard tissue bridges by using light and transmission electron microscopy techniques and immunohistochemical staining localization.

METHODOLOGY

Prior to the study, an animal use protocol form was reviewed and approved by the Screening Committee for Animal Research of the Tokyo Medical and Dental University. Exposed monkey pulps were capped with a hard-set calcium hydroxide and histopathologically evaluated at 3, 14, 21, 30 and 90 days, using light microscopy with silver staining and transmission electron microscopy to differentiate structural features of interodontoblastic collagen fibres. In addition, an attempt was made to identify and to differentiate between several types of collagen and fibronectin using immunohistochemical localization techniques.

RESULTS

At 14 days, interodontoblastic collagen fibres were observed extending from the original dentine, passing through the odontoblasts, and consisted of two portions: a thick fibril and a thin fibril. At 21 days, interodontoblastic collagen fibres were seen penetrating into the predentine and becoming incorporated into the mineralized dentine. At 30 days, interodontoblastic collagen fibres reached the cell process. Although interodontoblastic collagen fibres were no longer observed near the odontoblastoid cells at the area of the newly formed tubular dentine, interodontoblastic collagen fibres were observed embedded within the primary formed dentine bridge. Immunohistochemical staining demonstrated type I collagen and fibronectin within the interodontoblastic collagen fibres.

CONCLUSIONS

Interodontoblastic collagen fibres were routinely detected throughout early dentine bridges. Interodontoblastic collagen fibres are thought to be important for initial dentine bridging to induce and support a dentinogenesis framework.

A light and transmission microscopic study of mechanically exposed monkey pulps: dynamics of fiber elements during early dentin bridge formation

OBJECTIVE

The aim of this investigation was to assess the role of the von Korff-like fibers (VKF) during the process of dentin bridging.

STUDY DESIGN

The monkey pulps, exposed to a hard-set calcium hydroxide, were evaluated at 3, 7, 14, 21, 30, 90, and 180 days.

RESULTS

At 21 days, longitudinal and transverse collagen fibrils were organized as lamellar structures in close proximity to and subjacent to the newly formed predentin. VKF bundles were present between newly formed odontoblastoid cells. The VKF were bundles of thin collagen fibrils inserted into the predentin, which consisted of thick collagen fibrils. At 30 days, the exposure site was completely occluded with a new predentin matrix; lamellar structures and VKF were no longer present.

CONCLUSIONS

The VKF may play a role in the connective tissue attachment to the dentin bridge, early in its formation.