Foreign Body Giant Cell–Related Encapsulation of a Synthetic Material Three Years After Augmentation
Bone substitute materials of different origin and chemical compositions are frequently used in augmentation procedures to enlarge the local bone amount. However, relatively little data exist on the long-term tissue reactions. The presented case reports for the first time histological and histomorphometrical analyses of a nanocrystaline hydroxyapatite–based bone substitute material implanted in the human sinus cavity after an integration period of 3 years. The extracted biopsy was analyzed histologically and histomorphometrically with focus on the tissue reactions, vascularization, new bone formation, and the induction of a foreign body reaction. A comparably high rate of connective tissue (48.25%) surrounding the remaining bone substitute granules (42.13%) was observed. Accordingly, the amount of bone tissue (9.62%) built the smallest fraction within the biopsy. Further, tartrate-resistant acid phosphatase–positive and –negative multinucleated giant cells (4.35 and 3.93 cells/mm2, respectively) were detected on the material-tissue interfaces. The implantation bed showed a mild vascularization of 10.03 vessels/mm2 and 0.78%. The present case report shows that after 3 years, a comparable small amount of bone tissue was observable. Thus, the foreign body response to the bone substitute seems to be folded without further degradation or regeneration.
Representative images of the tissue reaction within the crestal region of the sinus biopsy 3 years after application of the synthetic hydroxyapatite-based bone substitute Nanobone (NB). (a) Within this region, low amounts of newly built bone (B) outgoing from the sinus ground were found related to the material granules (NB). The bone substitute granules were mainly surrounded by connective tissue (CT; hematoxylin and eosin staining, ×100 magnification, scale bar = 100 μm). (b) Low numbers of multinucleated giant cells were found at the granule surfaces from which most show tartrate-resistant acid phosphatase (TRAP) expression (red arrowheads), while lower numbers of these multinuclear cells were TRAP negative (black arrowheads). Mainly TRAP-negative mononuclear cells (black arrows) were found at the material-tissue interfaces, and only the minority of these cells were TRAP positive (red arrows; TRAP immunostaining, ×600 magnification, scale bar = 10 μm). (c) In the crestal biopsy region were relatively high amounts of vessels (blue arrows) ranging from microvessels up to vessels with bigger lumina (CD31 immunostaining, ×200 magnification, scale bar = 10 μm).
Representative images of the tissue reaction to the synthetic hydroxyapatite-based bone substitute Nanobone (NB) within the apical region of the sinus biopsy 3 years after its application. (a–c) Bone substitute granules (NB) were surrounded by connective tissue (CT), which built fiber-rich fibrous capsules (yellow asterisks). Only single mononuclear cells (green arrows) were detectable within the fibrous connective tissue at the granule surfaces, which did not show any signs of an involvement in a foreign body reaction (a: Masson-staining; b: hematoxylin-eosin [HE] staining, ×200 magnifications, scale bars = 100 μm; c: HE staining, ×600 magnification, scale bar = 50 μm). (d) The intergranular CT contained only low numbers of microvessels (blue arrows; CD31 immunostaining, ×200 magnification, scale bar = 10 μm).
Results of the histomorphometrical analyses. (a) Implant bed vascularization including vessel density (vessels/mm2) and percentage vascularization. (b) Total numbers of material-induced multinucleated giant cells and their tartrate-resistant acid phosphatase–positive and –negative subforms per mm2. (c) Tissue distribution within the implant area including the percentage area of bone tissue, remaining bone substitute, and connective tissue.
Contributor Notes