The influence of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) on dental root resorption in the mouse

It has been hypothesized that phagocytosis of a layer of mineralized material which is sometimes deposited along the root surface following trauma is an important factor in the initiation of the resorption of teeth. To test this hypothesis, freezing of the mouse incisor periodontium was used as a model where deposition of mineral was prevented by the systemic administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP, 10 mg P/kg b.w.) for time periods varying from 2 to 31 days. The animals were killed either 24 hours or 1 month after the last injection and their mandibles were processed for light microscopy. In the HEBP-treated animals, killed 24 hours after the last injection, no mineralized material had been deposited along the root surface, and very little resorption was seen. Large amounts of bone matrix were deposited in the intraperiodontal space (often causing localized ankylosis). In HEBP-treated animals killed 1 month after the last injection, again no layer of mineralized material along the root surface was seen, but now root resorption had become manifest, occupying up to 40% of the cement surface. This occurred irrespective of the duration of HEBP administration. In the saline-treated animals, extensive resorption of the incisor was noted (up to 90% of its surface). It is concluded that the layer of mineralized material deposited after the periodontium is frozen does not play a decisive part in the onset of root resorption. HEBP treatment slows down root resorption but does not prevent it.