Key Engineering Materials Vols. 493-494

Abstract: Bone matrix consists of organic and inorganic components. Organic phase mainly contributes to flexibility of bone while inorganic phase being responsible for the rigidity and hardness of the bone. Due to the biocompatibility of ceramics many forms of them have been used as the bone replacement and as the repair material. Hydroxyapatite which also exists in the natural structure of bone is one of those ceramics used as a component of bone cement. In order to modify the physical properties of prepared bone composite structures, some additives are included within the structure. In this study, a silicate material is included as an inorganic filler together with hydroxyapatite. Bis-GMA and HEMA were used as organic matrix. The prepared composites were than immersed in SBF and FTIR, SEM, hardness analyses were performed on the samples before and after the immersion. The results were reported in later part. It was observed that the precipitation of hydroxyapatite occurred after the immersion of samples in SBF and the hardness values were increased for each sample.

Abstract: The purpose of this study is to investigate whether calcite blocks with high mechanical property could be obtained for a short period from calcium hydroxide (Ca(OH)₂) compact using heat-treatment under carbon dioxide (CO₂) atmosphere. The Ca(OH)₂ disks compacted with different pressure was heated at different temperature ranging from 200°C to 800°C for an hour under CO₂ atmosphere. From the X-ray diffractometry, Ca(OH)₂ converted into calcite along with the rise of the heating temperature. Small amount of unreacted Ca(OH)₂ remained in samples heated at 600°C whereas samples treated at 800°C converted to calcite with very small amount of calcium oxide. The diametral tensile strength (DTS) value increased with the rise of heating temperature up to 600°C then decreased down to 800°C. Meanwhile, the porosity decreased with the rise of heating temperature up to 600°C then slightly increased up to 800°C. From the scanning electron microscope observation, grains grew bigger along with the rise of heating temperature. Intergranular space between grains decreased from 200°C to 600°C. The highest DTS value (14 MPa±1.3) at 600°C could be the result of lesser intergranular space due to sintering.

Abstract: We have shown that hydroxyapatite (HA), which characteristics were similar to those of bone’s inorganic components, had polarization capability and was possible to accumulate electricity under high temperature and pressure. Then, we presumed that bones had polarization capability which enabled electrical storage and conducted the experiment to measure the polarization capability of bones using rabbit’s femurs. After preparing and polarizing bone samples using KOH treatment (koh), KOH and baking treatment (koh+bake) and decalcification treatment (decalcification) as well as the bone without any treatment (untreat), quantitative amounts of stored charge in samples were determined by thermally stimulated depolarization current (TSDC) measurement of these samples. Under the condition of 400 °C for 1 h with the electric fields of 5kV/cm, samples of koh, koh+bake, and untreat showed polarization capability. In addition, under the polarization condition of 37 °C for 1 hour with the electric fields of 5kV/cm, all samples showed polarization capability. Those findings can be summarized that bones have the polarization capability which enables electrical storage and polarization of bones is possible even under the low temperature condition, which was at 37 °C in our experiment, where polarization is impossible for HA.

Abstract: Clinoptilolite mineral which is a member of zeolite family has been recently used in medical and dental applications. Until today, it has never been used as a graft material. In the present study tricalcium phosphate (TCP) imbued 90-95% pure clinoptilolite was used as graft in rabbit tibia. General anesthesia was accomplished using intra muscular (IM) injections of Xylazin and Ketamine HCL. TCP imbued clinoptilolite was placed in the defects created in the tibias of the subjects. Control group defects were left empty. One group was sacrificed on day 28 and the other group on day 56 to evaluate osteogenesis, residual graft material, inflammation and fibrosis. Histological evaluation revealed new bone formation at 28 days to be 14/7 at control group where as its 11/7 for the experimental graft group. At 56 days the values are as 18/7 for control and 14/7 for the experimental graft groups (n = 7). Our study group is the first to perform intrabony application of clinoptilolite. No evidence of abnormal inflammatory cell formation or fibrosis was witnessed in groups. When TCP, which can be used as a standalone graft material, was mixed with zeolite it was not as effective as expected. We believe that, TCP particles are absorbed and captivated in the initial phase and due to absorption strength of zeolite cannot be released back to the environment. We assume its effect can increase with longer time periods. Bone formation without infection is observed around graft particles. Based on the present study, since clinoptilolite does not provoke an inflammatory process, its use in unison with TCP can provide a supporting structure in defects.

Abstract: Cathodic deposition of nanocrystalline hydroxyapatite coatings on titanium surface was carried out under different magnetic field conditions. The electrolyte was prepared to maintain physiological pH and was agitated using a magnetic stirrer throughout the time of electrolysis. Silver was incorporated in the current coating because of its antibactericidal and cytotoxic nature. It was found that the silver concentration in HA coated titanium without magnetic field was higher than the coating formed under magnetic fields. This may be attributed to the diamagnetic nature of silver in different magnetic field conditions.

Abstract: Since 1985, HA granules were interposed on the interface between bone and bone cement at the cementation (Interface Bioactive Bone Cement : IBBC) in THA to prevent generation of connective tissue and osteolysis. To prevent infection, β-TCP impregnated with antibiotics along with HA granules was used. As TCP is resorbable, antibiotic release can be controlled. β-TCP granules were impregnated with antibiotics of folmoxef sodium (F), Vancomycine hydrochloride (V) cefortiam dihydrochloride (C) and cefozopran hydrochloride (CE). Three models of antibiotic release were assumed. Model [1] was antibiotic release from surroundings of β-TCP granules. Model [2] was the condition loaded under normal and reduced pressure. In Model [3], β-TCP was dissolved gradually in EDTA, as the model in the living body. In model [1], the amount of release of F, V and C was 3280, 300 and 3 µg, respectively and completed in 30 hours. In model [2], the amount of release of F, V, C and CE was 16, 8, 0 and 8000 µg in reduced pressure, respectively. The release of F, V and C completed within 24 hours and that of CE was in 6 days. In model [3], released amount of C and CE was 116 and 7100 µg, respectively and completed in 19 days.

Abstract: In this paper, a simple precursor thermolysis method is applied to prepare calcium phosphate crystals and macroporous ceramic. The phase composition of sample was determined by XRD and the morphology of sample was observed by TEM and SEM. The macroporous ceramic was observed by 3D digital microscope. Results show that 25-100 nm HAP nanocrystals were obtained at 500°C and HAP rod-like crystals with an equivalent diameter of about 0.50-1.6μm and a length of about 5-10μm were obtained at 700°C. In addition, about 100 nm β-TCP nanoparticles were also obtained at 900°C. The colloidal precursors can also be used to fabricate macroporous calcium phosphate ceramic. The size of pores is about 100-200μm. Pores are well opened and interconnected in three dimensions.

Abstract: A novel gallium-doped -tricalcium phosphate (-TCP) ceramics with rhombohedral structure (R3c space group) can be obtained by the addition of a Ga precursor in the typical reaction protocols used for the preparation of -TCP. It was found, from the refinement of their XRD patterns, that the incorporation of Ga in the -TCP network occurs by substitution of one of the five calcium sites, while occupation of another Ca site decreases in inverse proportion to the gallium content in the structure. A decrease of the unit cell volume is observed with increasing gallium content, together with improved mechanical properties. Indeed, the compressive strength of these new bioceramics is enhanced in direct proportion of the Ga content, up to a 2.6-fold increase as compared to pure -TCP.

Abstract: Pure hydroxyapatite (HA) was obtained by the calcination of calf femoral bone and was ground manually and by subsequent mechanical grinding to decrease the particle size. Micron-sized Al₂O₃, ZrO₂, and TiO₂ ceramics were added at different concentrations (5, 10 and 15 wt. %) to the obtained micron-sized HA powder. After adequate mixing cylindrical test specimen were prepared and sintered at 900, 1000 and 1100 °C. The specimen were tested for their compressive strengths and SEM observations and XRD analyses were conducted to determine the effect of different additives and sintering temperatures on the mechanical strengths, morphology and formed phases of the samples. TiO₂ addition to the HA at 15 wt. % powder resulted in highest compressive strength with good sintering behavior.

Abstract: The knowledge of the degradation process is an important role to understand and predict in vitro results. Granules of strontium-hydroxyapatite (Sr-HA) were submitted to a degradation process under dynamic conditions using a bioreactor system and using a solution with pH=5. The degradation process under dynamic conditions can be represented by a curve in which the calcium content firstly increases (dissolution part) followed by calcium decreasing (reprecipitation). The use of a low pH solution does not affect the curve’s shape but reduces the precipitation step.