Fate of Subcutaneous Anorganic Bone Implants

¹ Loyola University School of Dentistry, Chicago, Illinois

Forty mice were used for the subcutaneous implantation of 40-mesh anorganic bone, heterologous boiled beef bone, and isologous mouse bone. Histologic study of undecalcified bone implant from 24 hours through 6 months was done. Special stains, von Kossa for calcium phosphates and P.A.S. for mucopolysaccharides, were used.

The anorganic bone was surrounded by a cellular and vascular capsule. Histiocytes were elaborated from undifferentiated connective tissue and came into immediate surface contact and enveloped the implant.

The mineral salts of the implant leached out into the tissue fluid, because of the reduced amount of anorganic matrix capable of binding the salts in a fluid system. In time, the periphery of the implant completely lost its mineral content, while the central areas still retained some. At 6 months, some implant particles were completely free of salts; yet the matrix remained surrounded by a syncytium of histiocytes and a capsule. Rarely was a surface defect in the implant resembling Howship lacunae seen. The capsule served to control the removal of leached-out salts and to wall off the matrix from the connective tissue of the implant site. In effect, the capsule was a physiologic barrier to regulate absorption of high concentration of minerals and a histologic barrier walling off foreign protein matrix.

Isologous mouse bone and heterologous beef bone induced a reaction similar to anorganic bone. The polymorphonuclear leukocytic infiltration which accompanied heterologous bone and persisted for 6 months appeared as a classic foreign-body reaction.

It was concluded that anorganic bone did not show any bone inducing properties. Moreover, it was not resorbed over a period of 6 months and therefore did not demonstrate any osteoclastic-inductive-property.