IMMUNOLOCALIZATION OF FIBRONECTIN DURING REPARATIVE DENTINOGENESIS INHUMAN TEETH AFTER PULP CAPPING WITH CALCIUM HYDROXIDE

Exposed dental pulp is known to possess the ability to form a hard-tis sue barrier (dentin bridge). The exact mechanisms by which pulp cells differentiate into odontoblasts in this process are unknown. Fibronect in has been demonstrated to play a crucial role in odontoblast differe ntiation during tooth development. This study tested the hypothesis th at fibronectin is involved in the initial stages of replacement odonto blast differentiation and reparative dentin formation. We observed its immunohistochemical localization during dentin bridge formation in hu man teeth, after pulp was capped with calcium hydroxide [Ca(OH)(2)]. O ne day after the capping, precipitation of crystalline structures was observed at the TEM level in association with cell debris at the inter face between the superficial necrotic zone and underlying pulp tissue. This layer of dystrophic calcification showed positive reaction for f ibronectin, and pulp cells appeared to be closely associated with this layer, seven to ten days post-operatively. At 14 days, an alignment o f cells, some of which were elongated and odontoblast-like, was observ ed adjacent to the fibronectin-positive irregular matrix. Between the cells, corkscrew fiber-like fluorescence was visible. At 28 days, the irregular fibrous matrix was followed by the formation of tubular dent in-like matrix lined with odontoblast-like cells. Therefore, it would seem that fibronectin associated with the initially formed calcified l ayer might play a mediating role in the differentiation of pulp cells into odontoblasts during reparative dentinogenesis, after pulp was cap ped with Ca(OH)(2).