Histologic and elemental microanalytical study of anorganic bovine bone substitution following sinus floor augmentation in humans

Background: Histologic data regarding the use of anorganic bovine bone (ABB) in humans are scarce. This study was a histologic evaluation and an examination of the elemental composition of ABB particles and adjacent bone in humans. Methods: Ten biopsies were retrieved 20 months after maxillary sinus augmentation in five patients. The investigation was carried out using light microscopy in brightfield, fluorescence, and circularly polarized light and scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy. Results: The regenerated tissue consisted of 38% +/- 2.1% newly formed bone, 36% +/- 1.3% marrow spaces, and 29% +/- 1.8% residual ABB particles. Under polarized light, the newly formed bone was characterized by randomly oriented collagen fibers. Under fluorescence, the biomaterial showed close apposition to bone; under SEM, several projections of newly formed bone were seen penetrating the ABB particles. ABB and bone were distinguished by the lighter gray color of the biomaterial in back-scattered electron images; ABB particles were surrounded and linked by newly formed bone. Elemental analysis gave average calcium/phosphorus ratios (atomic %) similar to 1.9 for ABB and 1.4 for bone. Relatively high concentrations of calcium and phosphorus in the biomaterial decreased gradually toward the interface with bone. Conclusion: The persistence of ABB in the human tissue after 20 months might have been related to the relatively high calcium content of the biomaterial as well as the absence of proteins.