The induction of reparative dentine in the amputated dental pulp of the dog by bone morphogenetic protein.

Reparative dentine was formed in the cavity of the amputated pulp when capped with crude allogeneic BMP. This began with a slight cell-mediated immune response and was followed by resorption of BMP and proliferation of migratory spindle-shaped mesenchymal cells, together with vascular invasion. Four weeks postoperatively, there were osteodentinoblasts embedded in forming matrix and/or osteodentinocytes trapped within osteodentine in some parts of the cavity. Other parts were filled with pulpal tissue. Eight weeks postoperatively, odontoblasts were forming tubular dentine next to the osteodentine. In albumin-implanted controls, a little osteodentine and no tubular dentine were seen. These findings suggest that dissolved BMP stimulates mitosis of mesenchymal cells and may induce differentiation of osteodentinocytes. The resultant osteodentine may play some role in the differentiation of odontoblasts.