Papers by Keyword: Calcium Phosphate

Abstract: The histomorphometry of the rabbit bone tissue from the lower jaw was done. Authors hypothesized that local enhancement with biphasic calcium phosphate ceramic materials in the femur trochanter major area increase the trabecular bone volume outside the implantation zone in vivo. Twenty-two California female rabbits were included in this study and were divided into four groups. Four healthy rabbits composed a control group (A group), while other eighteen underwent ovariectomy. Bone defects were created in femur trochanter major region. Sham surgery group (B group) consisted of four female rabbits with osteoporosis and bone defect, but no biomaterials were implanted. In C group (seven rabbits) created defects were filled with granules of biphasic calcium phosphate ceramic (hydroxyapatite (HAP) and tricalcium phosphate (TCP) 30/70); in D group (seven rabbits) defects were filled with the same granules (HAP/TCP 30/70) together with strontium (5% by mass). Twenty-two bone samples were taken from lower jaw premolar region. Trabecular bone area was measured using Image Pro Plus 7 program, where three equal fields (0.975 mm²) of view were at random chosen in all bone samples. Results have shown that the trabecular bone area in A group was 0.201 mm² (0.176-0.233), which is statistically significantly higher (p <0.0001) than in B group 0.127 mm² (0.118 – 0.149), C group 0.136 mm² (0.108 – 0.166) and D group 0.135 mm² (0.126 – 0.164), respectively. Statistically significant differences between B, C and D groups were not found (p > 0.05).

Abstract: From the last few decades, biodegradable composites have become best alternatives over the petro based polymer because these degrade in the simple compound in the natural environments. Among the available biodegradable polymers, polylactic acid (PLA) is more popular due to its biocompatibility and mechanical properties, that can be used in the biomedical application, such as sutures, bone and ligament fixation screws etc. In this study, synthesis of PLA was performed by ring opening polymerization and Calcium phosphate/Polylactic acid (PLA) bio-composites were prepared by melt mixing technique. Tensile properties of these composites are investigated to assess its feasibility in biomedical and food packaging application.

Abstract: Calcium phosphate biocomposites are candidate materials for bone tissue engineering due to their conductivity and biocompatibility. Calcium phosphate could be grown on collagen by precipitation method in long reaction time. Microwave irradiation is rapid method to assist precipitation by reducing reaction time. In order to study carbonated calcium phosphate precipitation on collagen and investigate the influence of microwave irradiation time, the carbonated calcium phosphate has been grown on collagen by microwave assisted precipitation method. The collagen sheets were soaked in carbonated calcium phosphate suspension prepared by using Ca(NO₃)₂.4H₂O, (NH₄)₂HPO₄, and NaHCO₃ as starting materials, then microwave irradiated at 270 Watt for 2 minutes, 8 minutes, and 16 minutes. X-ray powder diffraction (XRD) pattern shows the transformation of dicalcium phosphate dyhydrate to apatite crystal structure. Increase in irradiation time had increased crystallinity of carbonate apatite phase. FTIR spectrum had confirmed presence of collagen, phosphate, and carbonate functional group. Scanning electron micrograph showed the presence of collagen with pore, and the carbonated calcium phosphate could attach and be deposited onto collagen.

Abstract: Cotton-wool-like bioresorbable bone void fillers consisting of β-tricalcium phosphate (β-TCP), siloxane-containing vaterite (SiV) and poly (_L-lactic acid) (PLLA) was prepared by an electrospinning method. The fibers, which were 50 ~ 150 μm-width with 10 ~ 30 μm-thickness, were entwined. The resulting cotton-wool-like material showed mechanical flexibility and excellent shapability; it showed easy, excellent mechanical-fixation in defects. The in vivo performance of this material was examined in the distal femur in New Zealand white rabbits. It was evaluated using micro CT and histologic analyses at time points of 6 and 12 weeks. These analyses of the defect sites verified normal healing response and new bone formation. The in vivo testing with rabbits showed good biocompatibility and excellent osteogenic ability.

Abstract: 60CaO-30P₂O₅-(10 ̶ x)Nb₂O₅-xTiO₂ (x = 0 ~ 10, mol%) glasses were prepared in order to obtain biomaterials with high chemical durability and therapeutic ions releasability. Dissolution test of these glasses using Tris buffer solution showed the controlled release of niobate ions from Nb₂O₅-containing glasses and the formation of calcium titanate in some of them. These behavior might induce positive effects for bone regeneration.

Abstract: After successful application of the sitting drop vapour diffusion route to deposit calcium phosphate layers on mica muscovite sheets, in this work we have extended the method to mineralize polymer surfaces (OSTE+) and bidimensional materials (graphene), aimed to prepare implants or scaffolds for nonload bearing applications in the medical sector. Thin octacalcium phosphate/apatite layers have been deposited on mica muscovite sheets. Thin apatite/octacalcium phosphate layers deposited on OSTE+ polymer lames. When graphene nanoflakes where used as support, this technique yielded apatite/graphene nanocomposites.

Abstract: Calcium phosphate materials can be produced using a number of wet methods that are based on hydrothermal or co-precipitation methods that might use acidic or basic chemical environments. In our previously published works, we have investigated calcium phosphates such as monetite, hydroxyapatite, and whitlockite which were successfully produced by mechano-chemical methods and/or hydrothermal treatments from a range of marine shells and corals which were obtained from the Great Barrier Reef. The aim of the current work was to analyze and compare the mechanisms of conversion of one hard coral species and one calcified algae species from the Great Barrier Reef.

Abstract: Reconstruction of large maxillofacial bone defects remains challenging even with diverse current treatment modalities. Silica-calcium phosphate nano composite (SCPC) is a resorbable bioactive bone graft material with a strong stimulatory effect on osteogenic gene expression of osteoblasts and mineralized tissue formation. In a prospective experimental study we investigated the ability of SCPC scaffold seeded with human adipose derived stem cells (ADSCs) to regenerate bone in a critical-size canine calvarial defect. Porous SCPC discs were prepared by powder metallurgy method. ADSCs were isolated from human breast adipose tissue, expanded in vitro and differentiated along osteogenic lineage. Bilateral critical-sized defects, 2.5 cm in diameter each, were made in the calvaria of 12 adult dogs. One calvarial defect was filled by either SCPC disc alone (Group I) or SCPC disc seeded with 2.5 x10⁶ osteoblast-like cells (Group II) while other defect was left empty (ungrafted). Bone tissue regeneration and graft material resorption was evaluated 3 and 6 months postoperative using CT and histology. Calvarial defects grafted with SCPC alone or SCPC-Cell construct were grossly repaired while control ungrafted defect did not repair. Microscopically the newly formed bone in the grafted defects was compact and integrated with the surrounding host tissues. Near complete resorption of the graft material was observed. Histomorphometric analysis demonstrated higher bone surface area and more graft material resorption in defects grafted with SCPC-cell hybrid compared to SCPC alone.

Abstract: α-Tricalcium phosphate (α-TCP) is an important reactive component in calcium phosphate bone cements which are used for the bone tissue regeneration and augmentation. By thermally treating amorphous calcium phosphate (ACP) at relatively low temperatures (650–900 °C), it is possible to obtain sub-micrometre or nanosized α-TCP particles. In the current research, it is shown that the aqueous synthesis environment where ACP is precipitated has significant influence on the stability of ACP and the α-TCP content in the thermally treated products. During ACP synthesis pH must be kept basic. While it is possible to synthesize ACP if potassium hydroxide or sodium hydroxide is used to raise the pH of synthesis, ammonium ions also must be present in the solution to obtain α-TCP after thermal treatment of ACP. If sodium hydroxide is used, higher α-TCP content is obtained (compare 89 % and 66 %). Increase of Ca/P ratio stabilizes ACP and allows to obtain products with high α-TCP content. Increase of both calcium and phosphate ion concentration in the synthesis destabilizes ACP and reduces the amount of α-TCP in the product (twofold increase reduced α-TCP content from 89% to 2%).

Abstract: Calcium phosphate ceramics were substituted with several concentrations of zinc ions (0, 5, 10 and 15 mol%) using precipitation method. The effect of sintering temperature at 900 and 1000°C on zinc substituted calcium phosphate ceramics were observed. By increasing the sintering temperature, XRD peaks for zinc substituted calcium phosphate ceramics changed significantly. At sintering temperature of 900°C, hydroxyapatite phase was the major phase in the calcium phosphates containing 0 and 5 mol% zinc. However, at the sintering temperature of 1000°C, hydroxyapatite phase was partly transformed to another phase which was tricalcium phosphate. FESEM observations at sintering temperature of 1000°C exhibit that the particle size of the samples increased with addition of more zinc ions.