Abstract
The aim of this study is to evaluate the biocompatibility and osteoconductivity in surgical defects of sheep tibias filled with 1% strontium-containing nanostructured hydroxyapatite microspheres (SrHA), stoichiometric hydroxyapatite without strontium microspheres (HA), or blood clots. Santa Ines sheep were subjected to three perforations on the medial side of the left tibia. The biomaterials were characterized by X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) before implantation and by X-Ray Microfluorescence (µFRX) and Scanning Electron Microscopy (SEM) after sheep tibias implantation. Surgical defects were filled with blood clots (control), SrHA (Group 1) or HA (Group 2). After 30 days, 5-µm bone blocks were obtained for histological evaluation, and the blocks obtained from 1 animal were embedded in methylmethacrylate for undecalcified sections. Mononuclear inflammatory infiltrate remained mild in all experimental groups. Giant cells were observed surrounding biomaterials particles of both groups and areas of bone formation were detected in close contact with biomaterials. All groups showed newly formed bone from the periphery to the center of the defects, which the control, HA and SrHA presented 36.4% (± 21.8), 31.2% (± 14.7) and 26.2% (± 12.9) of newly formed bone density, respectively, not presenting statistical differences. In addition, the connective tissue density did not show any significant between groups. The SrHA showing a higher volume density of biomaterial (51.2 ± 14.1) present in the defect compared to HA (32.6 ± 8.5) after 30 days (p = 0.03). Microspheres containing 1% SrHA or HA can be considered biocompatible, have osteoconductive properties and may be useful biomaterials for clinical applications.
Highlights
Bone and joint degenerative and inflammatory problems affect millions of people worldwide
Characterization of the powders The X-ray Diffraction (XRD) patterns for the HA and strontium-containing nanostructured hydroxyapatite (SrHA) powders after sintering are depicted in Figure 2A, which shows that HA is a biomaterial with more crystallinity than SrHA
The HA group showed bone formation from the periphery toward the center of the defect and the presence of newly formed bone trabeculae with osteoblastic layers, but the central portion of the defect consisted of loose connective tissue with biomaterials, sparse chronic inflammatory infiltrate and few multinucleated giant cells (Figure 4A and 4B)
Summary
Bone and joint degenerative and inflammatory problems affect millions of people worldwide. They account for half of all chronic diseases in people over 50 years of age in developed countries. Various methods have been applied for the restoration of bone defects and preservation of bone morphology,[1,2] and several techniques for bone restoration have been developed and improved in recent years, including bone block grafts, guided bone regeneration, distraction osteogenesis, and the use of new biomaterials and growth factors.[3,4,5] autogenous bone. Especially the compounds hydroxyapatite (HA) and tricalcium phosphate (TCP), have been investigated as materials for bone regeneration for 80 years. Synthetic HA is usually employed in the form of coarse particles, with crystal morphology that is quite different from the biological apatite in bone.[9]
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