Papers by Keyword: Tricalcium Phosphate

Abstract: The importance of this work is development of two methods to try to improve the bone tissue regeneration. The surface of scaffold was modified in order to favor cell interaction, through adhesion and proliferation. PLA and gelatin were used. PLA has shown in literature good results in bone tissue engineering. The gelatin is used as coating in cell culture plates to improve cell attachment for a variety of cell types, including osteoblast. Hydroxyapatite (HA) and tricalcium phosphate (TCP) were used due to its known properties in tissue engineering. It was used the polymer foam replication technique to produce the scaffolds. For characterization were used: scanning electron microscopy (SEM), optical microscopy (OP), stereoscopy, transmission electron microscopy (TEM), X-ray microtomography (Micro-CT), X-ray diffraction (XRD) and X-ray fluorescence (XRF). The scaffolds showed morphology with adequate porosity for tissue engineering and the in vitro test showed evidence of not being cytotoxic.

Abstract: Albeit widely established in plastic and metal industry, additive manufacturing technologies are still a rare sight in the field of ceramic manufacturing. This is mainly due to the requirements for high performance ceramic parts, which no additive manufacturing process was able to meet to date.The Lithography-based Ceramic Manufacturing (LCM)-technology which enables the production of dense and precise ceramic parts by using a photocurable ceramic suspension that is hardened via a photolithographic process. This new technology not only provides very high accuracy, it also reaches high densities for the sintered parts. In the case of alumina a relative density of over 99.4 % and a 4-point-bending strength of almost 430 MPa were realized. Thus, the achievable properties are similar to conventional manufacturing methods, making the LCM-technology an interesting complement for the ceramic industry.

Abstract: β-tricalcium phosphate based ceramics (β-TCP) are resorbable biomaterials used as bone substitutive materials. Several ions can substitute specific Ca positions in the crystalline structure of TCP, so that general Me-TCP can be obtained. Particularly, magnesium can increase the temperature of β-α-TCP transformation while zinc stimulates the bone formation. In this work, the influence of magnesium or zinc ions on the sintering behavior of Me-TCP was investigated. The powders were produced through wet chemical synthesis with a freeze drying process. The powders were calcined and subsequently uniaxially pressed into pellets. The pellets were sintered up to 1300°C/1h. The influence of Mg or Zn doping was investigated by dilatometric studies, thermal analysis and XRD. The microstructure was evaluated through SEM. The results suggest that Mg increased temperature of β-α-TCP phase transformation. The Me-doped TCP samples can be considered as promising biomaterials, having stimulatory effect of Zn or suitable densification due to Mg addition.

Abstract: β-Tricalcium phosphate (β-TCP) ceramics are of interest for bone requirements implants due to resoption behavior. The mechanical properties of β-TCP, however, are not yet sufficient to allow load bearing application of implants. The aim of this work was to investigate the effect of Mg²⁺ substitution on the strength sintered TCP. Due to promotion of a liquid phase at 1200°C, Calcium pyrophosphate (CPP-C₂P₂O₇) was used to improve the sintering of the samples. The introduction of CPP was promoted by use of a Ca/P molar ratio of 1.45. The powders were synthesized using a mixture of Ca (OH)₂ suspension and diluted H₃PO₄ with addition of MgO and calcined at 750 °C, 900 °C and 1050 °C. The cold isostatic pressing compacts were sintered at 1200 °C and 1300 °C, respectively.It was shown that a small Mg content (1.5 mol%) increased both compressive strength and fractional density of the TCP material sintered at 1200 °C from 132 ± 39 MPa at 92.1 % of fractional density to 193 ± 29 MPa at 94.5 % of theoretical density. Higher amounts of Mg inhibited the grain growth provoking a increase of the boundary mobility activation energy. Abnormal grain growth (AGG) was observed after sintering at 1300°C, as result CPP - liquid phase formation. Increase of Mg content promoted AGG, due to inhibition of grain growth during normal grain growth resulting in a increase of the residual elastic energy of the system.

Abstract: In this work, the mechanical properties of magnesium doped tricalcium phosphate ceramics, considered a bioceramic for bone repair applications, were studied. Pure β-TCP and β-TCP doped with 2.25 mol% of Mg powders were synthesized through neutralization, freeze dried, uniaxially pressed and sintered at 1200°C/1h. The mechanical properties were evaluated through four points flexural and compression strength tests, fracture toughness and Young's Modulus. After the flexural strength test, the fracture's surface and their homogeneity were characterized by scanning electron microscopy. It was verified that Mg addition into β-TCP structure lead higher linear shrinkage, followed by higher residual stress, decreasing the mechanical properties compared to pure β-TCP ceramics. However, this behavior does not hinder the use of such bioceramics as bone substitutive materials, mainly in the sites that do not require high mechanical solicitations.

Abstract: Synthetic Polymers, both organic and inorganic, are used in a wide variety of biomedical applications. The polymers can be biodegradable or nondegradable. Chitosan (CH), which is a naturally biodegradable, non-toxic biopolymer obtained by the deacetylation of chitin, has been demonstrated to have an intrinsic activity against a wide spectrum of bacteria, filamentous fungi and yeast. Several investigators have studied reinforced tricalcium phosphate (TCP), Chitosan, polymethylmethacrylate (PMMA)/methyl methacrylate (MMA) as potential cement. In fact addition of TCP with chitosan to the cement can improve biocompatibility and also enhance the mechanical properties of the cement because of its both biocompatibility and osteoconductivity properties. Crystalline phase and microstructure of the cement with hydroxyapatite - poly (methyl-methacrylate) were characterized by scanning electron microscopy (SEM; FEI Company), with the purpose to draw solid conclusions about the influence of the particles size, form and uniform mixing on the chemical process. We acquired PMMA sorted according to granulometric size.

Abstract: In this study, effect of hydrolysis in simulated body environment on mechanical behavior oftricalcium phosphate (TCP)/Poly(L-lactic acid) (PLLA) composites were analytically characterized.In order to predict stress-strain behavior after hydrolysis, damage micromechanical analysis proposedby the authors were utilized. In this model, nonlinear behavior in stress strain relationship weresimulated considering interfacial debonding between TCP particle and PLLA matrix. For the purposeof deciding the interfacial strength, such as critical energy release rate, curve fitting was conducted onthe result of the composites with 15wt% TCP content. Theoretical results on 5wt% and 10wt%composites using the interfacial strength obtained were in good agreement with experimental results.This result indicated that interfacial strength was independent from TCP fraction.

Abstract: The aim of this research work was to investigate in vitro effect of the carbonate apatite/poly (ε-caprolactone) (CO₃Ap/PCL) on α-tricalcium phosphate (α-TCP) foam was produced by sintering CaCO₃ and CaHPO₄2H₂O at 1500°C for 5 h. It was then coated with carbonate apatite (CO₃Ap)/Poly-ε-caprolactone (PCL) (wt/wt=1/3) to improve both mechanical and biological properties. The initial cell attachment and proliferation of the bone marrow cells were carried out on the α-TCP and CO₃Ap/PCL-coated α-TCP foams. The cell proliferation was calculated by AlamarBlue assay. The cells were able to migrate and proliferate well on both α-TCP and CO₃Ap/PCL-coated α-TCP foams indicating an excellent biocompatibility. The incorporation of CO₃Ap on the coating layer improved cellular attachment and accelerated proliferation. Thus, CO₃Ap/PCL-coated α-TCP foam might be a promising candidate as implant material.

Abstract: Benign lytic lesions represent a frequent pathology in our clinic. Regarding therapy, we approach these benign tumors through curettage and filling the defects with bone grafting or bone substitutes like hydroxyapatite crystals and tricalcium phosphate.We want to evaluate the efficiency of both bone grafts and bone substitutes regarding bone consolidation, osseointegration and time until absorption for tricalcium phosphate and hydroxyapatite crystals combination. We analyzed 14 patients treated in our clinic through curettage and defect filling during the last three years: 9 patients’ beneficiated from bone grafting and for the other 5 we used a hydroxyapatite and tricalcium phosphate combination from the same supplier. Diagnoses were bone cyst, non-ossifying fibroma and giant-cell tumor. Therapeutic method was linked with bone graft availability. Follow-up was 24 months through periodical x-ray controls in our clinic. Bone consolidation was satisfactory in all cases with no defect collapse. In conclusion, bone substitutes like combinations of hydroxyapatite crystals and tricalcium phosphate are a useful and safe method for surgical treatment of strictly benign lytic tumors.

Abstract: Sucrose evaporation technique was applied to prepare porous ceramic scaffolds with multiphasic calcium phosphates. Compositions with Ca/P molar ratios of 1.67 with MgO were synthesized and subjected to a thermal treatment of up to 1050 °C to 1400 °C. The results show that various adjustable biphasic and multiphasic calcium phosphates can be prepared through vaporized filler amounts and controlled sintering temperature. The size of the pores in the final fabricated scaffolds with an interconnected network of pores ranged from several micro- to hundred micrometers of open pores. The phase amount of hydroxyapatite (HA) in the sintering process declined with elevated sintering temperature. The permeability of three-dimensional scaffolds used for tissue engineering was significant because it controlled the rate of cell migration and the diffusion of nutrients and waste products in and out of the scaffold.