Calcium phosphates and hydroxyapatite, in particular, are used as substitute materials in experimental implantology. These materials are primarily used in hard tissue replacement because their chemical and crystallographic characteristics are considered to be similar to the mineral content, osteoconductivity and bioactivity of normal bone. Cytokines, such as interleukin (IL)-1, IL-6, IL-8, IL-10 and antimicrobial protein β-defensin-2 (βDef-2), are used as biomarkers of non-specific reactogenicity. Other biomarkers, including bone morphogenetic protein-2/4 (BMP-2/4), bone regeneration protein osteoprotegerin (OPG), bone matrix protein osteopontin (OP) and osteocalcin (OC), are regarded as specific factors of reactogenicity in bone substitution. The aim of our study was to assess the changes in the distribution and expression of the aforementioned proteins in the lower jaws of rabbits following implantation with pure hydroxyapatite (HAP), α-tricalcium phosphate (α-TCP) or a mix of the two (HAP/α-TCP) manufactured under different temperatures. Our results reveal osteoblast proliferation and regions of granulation tissue formation between biomaterial granules close to the original implantation site, but in the control tissue these changes were less noticeable. Our study showed low variability in the distribution of βDef-2, OPG and all of the tested interleukins and these proteins were less expressed than BMP2/4, OP and OC. But across all experiments, no statistically significant difference in mean βDef-2, IL-1, IL-6, IL-8, IL-10, OP, OC, BMP-2/4 and OPG expression in osteocytes was detected between experimental and control groups. We concluded that pure and mixed HAP and α-TCP sintered at different temperatures do not affect the production of cytokines and bone-specific proteins; regions with osteoblast proliferation and low levels of anti-inflammatory cytokines IL-6 and IL-10 indicates better biocompatibility for HAP/α-TCP and α-TCP-2 biomaterials and the moderate number of BMP-2/4- and a prevalence of OC- and OP-positive osteocytes in experimental tissues implanted with HAP at 3 months after implantation indicates potential bone regeneration stimulated by pure HAP.
Biphasic calcium phosphate ceramic granules (0.5–1.0 mm) with a hydroxyapatite and β-tricalcium phosphate ratio of 90/10 were used. Biphasic calcium phosphate ceramic granules produced in the Riga Technical University, Riga Rudolph Cimdins Biomaterials Innovation and Development Centre, were used for filling the bone loss on 18 patients with peri-implantitis. After 5 years at the minimum, clinical and 3D cone-beam computed tomography control was done. Clinical situation confirmed good stability of implants without any signs of inflammation around. Radiodensity of the previous gap and alveolar bone horizontally from middle point of dental implants showed similar radiodensity as in normal alveolar bone. This trial is registered with ISRCTN13514478.
Clinical, Radiographic and Pathohistological Outcomes of Hydroxyapatite (HAp) Ceramics and Dental Implants in Atrophic Posterior Maxilla Introduction. Implant based prosthodontic rehabilitation of patients with atrophic edentulous posterior maxilla has necessity in reinforcement of alveolar bone using different bone substitutes. It is important to evaluate late outcomes in integration of synthetic HAp as biomaterial in chemical composition close to main natural bone mineral component in elevated maxillary sinus floor and osseointegration of dental implants. Aim of the study. To evaluate clinical and radiological outcomes of one stage maxillary sinus floor augmentation with synthetic HAp granules and dental implant insertion, mineralization degree of residual bone and augmented sinus part, morphological analysis of biopsies from HAp/host tissue hybrid and residual alveolar bone was performed. Materials and methods. One stage maxillary sinus floor elevation with synthetic HAp granules and 147 SEMADOS (BEGO) dental implant insertions in 70 patients were included in this study. Clinical and radiograph analyzes by dental X-rays, digital orthopantomogramms, quantitative radiodensitometry after 3 and 5 years was done. Trephine biopsies of residual alveolar bone and elevated part of maxillary sinus 6 months after implantation was done in 30 cases. Results. During this period 6 implants (4.2%) were lost. We found the decrease of radiodensity in HAp augmentated maxillary sinus area and increase of radiodensity in the area of residual alveolar bone. In biopsies after 6 months biomaterial/host tissue hybrid consisted of small bone trabecules, fibrous tissue and granules of irregular shape without inflammatory cells. Slow degradation of HAp granules by activity of osteoclast like macrophages was observed. Conclusions. Osseointegration was lost in 4.2% of inserted in augmented maxillary sinus implants. Radiodensitometry showed decrease of optical density in augmented sinus part and increase in residual alveolar bone. In biopsies of host tissue/biomaterial hybrid was bone newformation, connective tissue and biodegradation of HAp granules by osteoclast like cells.
Calcium bone substitutes are successfully used for local recovery of osteoporotic bone and filling of bone defects. Previous studies revieled that biphasic calcium phosphate (BCP) show better bioactivity in compare to pure β-tricalcium phosphate or hydroxyapatite. Also increased porosity of material promotes better bone tissue response. Aim of this experiment was to evaluate immunohistologically response of osteoporotic bone of experimental animal to implantation of granules with hydroxyapatite/β-tricalcium phosphate (HAp/β-TCP) ratio of 90/10. Calcium phosphate (CaP) was synthesized by aqueous precipitation technique from calcium hydroxide and phosphoric acid. Bioceramic granules in size range from 1.0 to 1.4 mm were prepared with nanopore sizes around 200 nm. We used nine female rabbits with induced osteoporosis in this experiment. Six animals in study group underwent implantation of BCP in hip bone defect and three animals in control group left without BCP implantation. After 6 months animals were euthanized, bone samples collected and proceeded for detection of bone activity and repair markers: osteocalcin (OC), osteopontin (OP) and osteoprotegerin (OPG). Controls showed the presence of experimental bone osteoporosis. In experimental group bone showed partially resorbed bioceramic granules and in some samples new bone formation near the granuli was observed. Increase of OC and OPG up to twice as to compare to control group were detected as well. Implantation of BCP granules in osteoporotic rabbit bone increases expression of OC and OPG indicating the activation of osteoblastogenesis and bone mineralization in vivo.
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