Fabrication of macroporous carbonate apatite foam by hydrothermal conversion of alpha-tricalcium phosphate in carbonate solutions.

Bone consists of a mineral phase (carbonate apatite) and an organic phase (principally collagen). Cancellous bone is characterized by interconnecting porosity necessary for tissue ingrowth and nourishment of bone cells. The purpose of the present study was to fabricate macroporous carbonate apatite (CAP) blocks with interconnecting porosity as potential bone substitute biomaterials by hydrothermal conversion of alpha-TCP foam in carbonate solution. The fabrication of the macroporous CAP was accomplished in two steps: (1) preparation of alpha-TCP foams using polyurethane foams as templates, and (2) hydrothermal conversion at 200 degrees C of alpha-TCP foam in the presence of ammonium carbonate solutions of different concentrations. The maximum carbonate content of the resultant CAP foam was approximately 7.4 wt %. The mean porosity of the CAP foam was as high as 93 vol %. The macroporous CAP blocks or granules prepared in this manner has properties similar to that of bone in mineral composition and in having interconnecting macroporosity necessary for osteoconductivity and tissue ingrowth. On the basis of composition and interconnecting macroporosity, the CAP foam materials could be ideal biomaterials for bone repair and as scaffolds for tissue engineering.

MAS-NMR spectroscopy studies in the setting reaction of glass ionomer cements.

OBJECTIVES: The main objective is the characterisation of the setting reaction in glass ionomer cements based on experimental ionomer glasses with different fluorine content and a commercial glass ionomer cement liquid by using 13C CP/MAS-NMR, 29Si, 27Al and 31P MAS-NMR spectroscopy in order to receive information specifically about the cross-linking process. METHODS: Different fluorine containing glass compositions based on 4.5SiO2-3Al2O3-1.5P2O5-(5-z)CaO-zCaF(2) where z=0-3, were mixed with a commercially available polymer liquid to form glass ionomer cements. The cements were subjected to 27Al, 13C CP/MAS, 29Si, and 31P MAS-NMR analysis. RESULTS: The 27Al spectra showed clearly the formation of six-fold coordinate Al(VI), that may crosslink the carboxyl groups in the poly-acid molecules. A shift towards to more positive values of the carboxyl peak in the 13C CP/MAS-NMR spectra showed clearly the proton dissociation of the carboxyl groups. A shift towards more negative values was observed in the 29Si MAS-NMR spectra, suggesting formation of hydrated silica gel and consequently formation of additional Si-O-Si bonds. 31P MAS-NMR spectra also reflected changes in the coordination state around a PO4(3-) tetrahedron. Increasing the fluorine content of the glasses resulted generally in increased reactivity during setting, due to promoting cross-linking and repolymerisation of the silicate phase, followed by clear changes in the MAS-NMR spectra. CONCLUSIONS: The cross-linking process during the setting reaction of glass ionomer cements can be followed by MAS-NMR spectroscopy observing the conversion of Al(IV) to Al(VI). The acid base setting reaction is completed in 1 day and no further significant changes in the MAS-NMR spectra can be observed. Further study is required in order to understand the role of phosphorus.

Effects of hydrothermal treatment with CaCl(2) solution on surface property and cell response of titanium implants.

In order to obtain early and good osteointegration after implantation of a titanium implant in the human body, the surface modified treatments using NaOH or H(2)O(2) etc. were reported. In this study, titanium was hydrothermally treated with CaCl(2) solutions at 200 degrees C for 24hr (CaCl(2)-HT). Scanning electron microscope (SEM) observation clearly showed apatite deposition on the surface of CaCl(2) HT treated titanium faster than other chemical treated titanium immersion in simulated body fluid. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that Ti--O--Ca bonding was formed on titanium surface by hydrothermal treatment with CaCl(2) solution. And it was revealed that thickness of TiO(2), which was known to play important roles for the formation of bone-like apatite, became approximately three times thicker than as-polished titanium. The amount of initial attached MC3T3-E1 cells on as-polished and NaOH, H(2)O(2) and this CaCl(2) HT treated titanium were almost the same values. After 5 days incubation, the growth rate of MC3T3-E1 cells on CaCl(2)-HT treated titanium was significantly higher than that on other chemical treated titanium. The hydrothermal treatment with 10-20 mmol/L CaCl(2) solution at 200 degrees C was an effective method for the fabrication of titanium implant with good bioactivity and osteoconductivity.

The effect of Pt and Pd alloying additions on the corrosion behavior of titanium in fluoride-containing environments.

In this study, we examined the corrosion behaviors of pure titanium, the alloys Ti-6Al-4V and Ti-6Al-7Nb, and the new experimental alloys Ti-Pt and Ti-Pd using anodic polarization and corrosion potential measurements in an environment containing fluoride. Before and after immersion in the test solutions, we made observations using a scanning electron microscope. The test solutions included an artificial saliva containing 0.2% NaF (corresponding to 905 ppm F) and an artificial saliva with a low concentration of oxygen. Although the surfaces of the Ti-Pt and Ti-Pd alloys were not affected by an acidic environment containing fluoride, the surfaces of the pure titanium, the Ti-6Al-4V alloy, and the Ti-6Al-7Nb alloy were markedly roughened by corrosion. The surfaces of the pure titanium, the Ti-6Al-4V alloy, and the Ti-6Al-7Nb alloy were microscopically damaged by corrosion when they were immersed in the solution containing a low concentration of dissolved oxygen, even with a fluoride concentration included in the commercial dentifrices. In this situation, however, the surfaces of the new Ti-Pt and Ti-Pd alloys were not affected. These alloys are expected to be of use in dental work as new titanium alloys with high corrosion resistances.

Basic properties of apatite cement containing spherical tetracalcium phosphate made with plasma melting method.

Apatite cement (AC) can be injected through syringe and forms apatite mass. Therefore, AC is very useful for a minimally invasive surgical operation aimed for the reconstruction of bone defects. However, injectability of current AC is not satisfactory for its clinical use. In this investigation, therefore, spherical tetracalcium phosphate (s-TTCP) was prepared with plasma melting method and its effect on injectability were evaluated as well as other basic properties of AC. We found much better handling property and injectability when we used s-TTCP as a component of AC (s-AC). For example, cement spread area used as an index of consistency of the s-AC paste was 512 mm2 whereas that of ordinary AC with irregular TTCP (i-AC) was 158 mm2 when powder to liquid mixing ratio was 2.5. However, diametral tensile strength of set s-AC (1.4 MPa) was significantly lower than that of set i-AC (10.7 MPa) when the powder to liquid ratio was 4.0. X-ray powder diffraction analysis revealed limited formation of apatite in the case of s-AC. Although there are some drawbacks, we feel the use of spherical particle is very useful to improve the injectability of AC. Therefore, it is important to find suitable method to prepare spherical powder as the component of AC.

Observation of fluorapatite formation under hydrolysis of tetracalcium phosphate in the presence of KF by means of soft X-ray emission and absorption spectroscopy.

The effect of fluoride on the hydrolysis of tetracalcium phosphate (TTCP; Ca4(PO4)2O) in 0.1 mol/l KH2PO4 containing 62-83 mmol/l KF was studied with the help of X-ray fluorescence measurements. Fluorine X-ray emission and absorption spectra of the final product of hydrolysis and reference samples (CaF2 and Ca5(PO4)3F) were measured at Beamline BL-2C of Photon Factory (PF, Tsukuba). Based on these measurements we concluded that hydrolysis of TTCP in the presence of KF converts it into fluorapatite. Formation of CaF2, which is often found in the hydrolysis of hydroxyapatite at high fluoride concentration, was not observed.

[Successful combined therapy with ATG, cyclosporin and G-CSF for both liver dysfunction and bone marrow failure in hepatitis-associated aplastic anemia].

A 28-year-old man developed cryptogenic hepatitis in January 1999, and treatment with glycyrrhizic acid improved his liver function. From June, however, pancytopenia began to develop gradually. The patient received G-CSF against leukocytopenia (WBC 1,100/microliter, neutrophils 590/microliter) and was transferred to our hospital in August 1999. A diagnosis of hepatitis-associated aplastic anemia was made on the basis of liver dysfunction (AST 156 IU/l, ALT 386 IU/l), hypoplastic bone marrow, and pancytopenia (WBC 4,400/microliter, neutrophils 3,340/microliter under G-CSF administration, Hb 9.8 g/dl, platelets 2.4 x 10(4)/microliter, reticulocytes 4.7 x 10(4)/microliter). Immediately after starting combined therapy with ATG, cyclosporin, and G-CSF, his liver function began to improve and was normalized on day 7. Pancytopenia began to ameliorate on day 9, and blood parameters on day 60 were WBC 4,200/microliter (without G-CSF administration), Hb 12.0 g/dl, platelets 9.0 x 10(4)/microliter, and reticulocytes 4.1 x 10(4)/microliter. Although the prognosis of hepatitis-associated aplastic anemia is generally poor, immunosuppressive therapy was markedly effective for both pancytopenia and hepatic dysfunction in the present case.

Setting characteristics of five autopolymerizing resins measured by an oscillating rheometer.

STATEMENT OF PROBLEM: Ease of handling and the working time of autopolymerizing resins are directly associated with the setting characteristics during polymerization. PURPOSE: This study assessed the setting characteristics of autopolymerizing resins by measuring viscosity changes and tested the hypotheses that: (1) different products have different viscosity increase patterns during polymerization, and (2) the increased rate of viscosity is not proportional to the length of the setting time. MATERIAL AND METHODS: Viscosity change during polymerization was measured in 5 test materials (Unifast II, ADFA, META FAST, Miky, and Trim) with an oscillating rheometer. The working time was defined as the time required for a 5% reduction in the amplitude of the rheometer trace. The setting time was measured as the time required to reach zero amplitude on the rheometer trace. RESULTS: The order of working times from longest to shortest was Trim, Unifast II and META FAST, ADFA, Miky (ANOVA, P<.0001). The order of setting times from longest to shortest was Trim, META FAST, Miky, ADFA, Unifast II. Materials that had rapid setting times did not necessarily have short working times. Unifast II showed well-balanced setting properties that satisfied both longer working time and faster setting time. CONCLUSION: Autopolymerizing resins have setting characteristics specific to the brand. Knowledge of these characteristics is essential for selection of the appropriate resin product depending on the purpose of clinical usage and the individual dentist's technique.

The influence of calcium to phosphate ratio on the nucleation and crystallization of apatite glass-ceramics.

The nucleation and crystallization behavior of a series of glasses based on 4.5SiO2-3Al2O3-YP2O5-3CaO-1.51CaF2 was studied. The parameter Y was varied to give calcium to phosphate ratios between one and two. All of the glasses studied crystallized firstly to fluorapatite (Ca5PO4)3F). The glass with a calcium to phosphate ratio of 1.67, corresponding to apatite, bulk nucleated to give fluorapatite (FAP). The glasses with calcium : phosphate ratios either less than that of apatite, or greater than that of apatite all exhibited surface nucleation of FAP. However, following a nucleation hold of one hour at approximately 50 K above the glass transition temperature these glasses exhibited bulk nucleation of FAP.

Corrosion behavior of pure titanium and titanium alloys in fluoride-containing solutions.

The effects of fluoride concentrations and pH on the corrosion behavior of pure titanium, Ti-6Al-4V, Ti-6Al-7Nb alloys and a new Ti alloy adding palladium, which is expected to promote a repassivation of Ti were examined by anodic polarization and corrosion potential measurements. The amount of dissolved Ti was analyzed by inductively coupled plasma mass spectroscopy. The surface of the specimen was analyzed by X-ray photoelectron spectroscopy before and after the measurement. Pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloys were easily corroded even in a low fluoride concentration in an acidic environment. The corrosion resistance of Ti-0.2Pd alloy was greater than those of pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloys in the wide range of pH and fluoride concentrations. The high corrosion resistance of Ti-0.2Pd alloy was caused by the surface enrichment of Pd promoting a repassivation of Ti. The Ti-0.2Pd alloy is expected to be useful as a new Ti alloy with high corrosion resistance in dental use.

Origin of giant cells in osteoclast-like giant cell tumors of the pancreas.

To clarify the origin of giant cells in osteoclast-like giant cell tumors (OGCTs) of the pancreas, we performed microscopical, immunohistochemical, and K-ras gene mutation analyses with a microdissection approach in 3 cases, featuring 4 cellular components (osteoclast-like giant cells [OGCs], pleomorphic large cells [PLCs], mononuclear cells, and ductal carcinoma cells). Two cases had abundant OGCs, and 1 case contained large number of both OGCs and PLCs. In each, none of the microdissected OGCs contained any K-ras gene mutation while they were positive for a histiocytic marker (CD-68). In contrast, PLCs, when present, frequently harbored K-ras gene mutations and were negative for CD-68. In all cases, mononuclear cells, a mixture of histiocyte-like and atypical, from microscopic and immunohistochemical viewpoints, also frequently showed K-ras alteration. Histiocyte-like mononuclear cell was equipped with a regular and oval nucleus similar to those in OGCs and was positive for CD-68. Atypical mononuclear cell showed an irregular, pleomorphic, or sometimes bizarre nucleus similar to those in PLCs and was negative for CD-68. All of the K-ras gene mutations found in PLCs and mononuclear cells were the same as in the ductal carcinoma cells within the same tumor. Thus, OGCs differ in origin from ductal cells and are strongly suggested to be nonneoplastic and of mesenchymal origin, whereas PLCs, which harbor K-ras gene mutations, are neoplastic and presumably derived from ductal carcinoma cells. Moreover, mononuclear cells may be classified into 2 types, histiocyte-like and atypical.

Effect of mixing ratio and pH on the reaction between Ca4(PO4)2O and CaHPO4.

The reaction of Ca(PO4)2O (TTCP) and CaHPO4 (DCPA) in an aqueous solution has been shown to be responsible for the hardening of a calcium phosphate cement. This reaction was investigated by monitoring pH changes and composition of solid phases. In the first set of experiments (no attempt to control pH), 2.5 g each of mixtures of TTCP/DCPA, molar ratio from 0.25 to 2, was placed in 12.5 mL of 0.15 mol/L KCl solution, at initial pH about 7, and the pH was allowed to drift for 24 h. Results show that at any time up to 24 h, the pHs were higher for slurries with higher TTCP/DCPA molar ratios. For the slurries with TTCP/DCPA molar ratio of >/= 0.83, the 24 h pHs of the slurries were 9 to 11, whereas for those with TTCP/DCPA of

Effect of water temperature on the fit of provisional crown margins during polymerization.

STATEMENT OF PROBLEM: When fabricating a provisional crown with the direct technique, dentists are concerned with margin discrepancies that result from polymerization shrinkage. PURPOSE: This in vitro study examined the effect of water temperature on the fit of provisional crown margins during resin polymerization. MATERIAL AND METHODS: The experiment was designed to simulate a direct technique to fabricate provisional crowns. After mixing autopolymerizing methyl methacrylate resin, the material was placed in a preformed polycarbonate crown. The crown was seated on a prepared premolar-shaped die with a shoulder margin. After 1 minute and 50 seconds, the crown was removed and polymerization was continued under the following conditions: 20 degrees C air, and water at 0 degrees C, 10 degrees C, 20 degrees C, 30 degrees C, 40 degrees C, 60 degrees C, and 80 degrees C. Six minutes after polymerization, the crown was trimmed and reseated on the die. Discrepancy of crown margin was measured with a 3-dimensional digitizer. RESULTS: Margin discrepancy varied with the condition during resin-polymerization (ANOVA, P <.001). The crowns polymerized in 20 degrees C and 30 degrees C water revealed the best margin fit, showing 3 times more accurate margin fit than those polymerized in 20 degrees C air (Bonferroni/Dunn procedure, P <.01). CONCLUSION: Conditions during resin polymerization were significant factors that affected margin fit of provisional crowns using the direct technique. Water temperatures of 20 degrees C and 30 degrees C produced the best fit at the margin of the provisional crown.

Effect of fluoride concentration and pH on corrosion behavior of titanium for dental use.

Titanium is used as a metal for biocompatible materials such as dental implants or restorations because of its excellent chemical stability. However, the corrosion of Ti in the prophylactic fluoride-containing environment can become problematic. To clarify the effects of fluoride concentration and pH on the corrosion behavior of Ti, we conducted anodic polarization and immersion tests in NaF solution of various concentrations and pH values. The concentrations of dissolved Ti in the test solutions were analyzed by inductively coupled plasma mass spectroscopy. There were obvious limits of fluoride concentration and the pH value at which the corrosion behavior of Ti changed. The corrosion of Ti in the solution containing fluoride depended on the concentration of hydrofluoric acid (HF). When the HF concentration in the solution was higher than about 30 ppm, the passivation film of the Ti was destroyed. The results of this study revealed a relation between the fluoride concentrations and pH values at which Ti corrosion occurred and provided data on such corrosion in environments where the fluoride concentration and pH value are known.

Axonal and perikaryal involvement in chronic inflammatory demyelinating polyneuropathy.

OBJECTIVES: To assess the extent of loss of myelinated nerve fibres and spinal motor neuron loss in chronic inflammatory demyelinating polyneuropathy (CIDP), a clinicopathological study was conducted on biopsied sural nerves and necropsied spinal cords from patients with CIDP. METHODS: The myelinated fibre pathology of 71 biopsied sural nerves and motor neuron pathology of nine necropsied spinal cords at L4 levels in patients with CIDP were quantitatively and immunohistochemically assessed. RESULTS: Myelinated nerve fibre density was significantly diminished to 65.4% of the control values (p <0.0001), correlating inversely with the extent of segmental demyelination and remyelination (r = -0.43, p < 0.0005) and duration of illness (r = -0.31, p < 0.01). Numbers of large spinal motor neurons in CIDP were variably but significantly diminished (range from 46.0 to 97.6% of the age matched control value (p < 0.005)), and reactive astrogliosis was evident in the ventral horn in CIDP. The frequency of ventral horn neurons exhibiting central chromatolysis and the accumulation of phosphorylated high molecular weight neurofilament protein was significantly higher in CIDP than in controls (p<0.01 and p<0.05). CONCLUSIONS: The loss of nerve axons and spinal motor neurons is common in CIDP, and extensive in some cases. These neuronal and axonal losses may influence the functional prognosis in CIDP.

Effect of powder grinding on hydroxyapatite formation in a polymeric calcium phosphate cement prepared from tetracalcium phosphate and poly(methyl vinyl ether-maleic acid).

The primary aim of this study was to determine if cements based on poly(methyl vinyl ether-maleic acid) (PMVE-Ma) and tetracalcium phosphate resulted in hydroxyapatite formation. In addition, the mechanical strength of this type of polymeric calcium phosphate cement was evaluated. Cements were prepared by mixing, in a powder/liquid mass ratio of 3.0, an aqueous solution of PMVE-Ma (mass fraction = 25%) and tetracalcium phosphate powders ground for various periods of time. The tetracalcium phosphate powders and set cements were characterized by means of X-ray powder diffraction and scanning electron microscopy. Mechanical strengths of the cements were tested 24 h after mixing. Prolonged grinding of tetracalcium phosphate powder decreased particle size and/or crystallite size and increased lattice distortion. This enhanced the reactivity of the tetracalcium phosphate powder and elevated the extent of crosslinking between PMVE-Ma molecules, resulting in improved mechanical strength. Hydroxyapatite formation was detected in the cement prepared with the most finely ground tetracalcium phosphate powder. The conversion of residual tetracalcium phosphate particles to more thermodynamically stable hydroxyapatite crystals will reduce the solubility of the polymeric cement and increase its biocompatibility.

Structure of bioactive glass and its application to glass ionomer cement.

We prepared a new glass ionomer cement using bioactive CaO-P2O5-SiO2(-MgO) glass and investigated its setting process using FT-IR and MAS NMR analyses. The compressive strengths of the cements depended on the glass composition and a maximum strength of 33.3 +/- 4.7 MPa was obtained using cement with the glass composition of MgO:4.6, CaO:44.9, SiO2:34.2 and P2O5:16.3% in weight. FT-IR analysis showed that the COOH group in the polyacrylic acid decreased and carboxylate ion (COO-Ca2+) increased after the setting reaction. A broad signal appeared around -82 ppm in 29Si MAS-NMR spectra of the glass and a new signal corresponding to hydrated silica gel formation appeared around -102 and -111 ppm after setting. This suggests that Ca2+ was released from the glass powder to form carboxylate salt and that a degree of polymerization in the silicate network increased. The setting mechanism of the cement was found to be essentially the same as in conventional glass ionomer cement.

Formulation of glutaraldehyde disinfectant for alginate impressions.

The effect of buffer agents incorporated in glutaraldehyde disinfectants on the surface quality of dental models was examined by the measurement of surface roughness, X-ray diffraction analysis and SEM observation. Seven experimental glutaraldehyde disinfectants were prepared using two buffer agents, potassium acetate alone or potassium acetate and sodium hydrogen carbonate in combination. Four kinds of sulfate--zinc, calcium, potassium and magnesium sulfate--were added to these disinfectants in order to accelerate the hydration of calcium sulfate hemihydrate. The impressions treated with the experimental disinfectants for 1 h produced stone surfaces which had significantly lower surface roughness values than those treated with the commercial disinfectants (p < 0.05). The X-ray diffraction analysis and SEM observation showed that these superior surfaces were produced as a result of significant reductions in the amount of residual calcium sulfate hemihydrate. Replacement of buffer agents in commercial glutaraldehyde disinfectants with chemicals such as those studied in the present study will improve the surface quality of dental stone.

Sporadic amyotrophic lateral sclerosis resembling primary lateral sclerosis: report of an autopsy case and a review of the literature.

This report describes the clinicopathological findings of a case of sporadic amyotrophic lateral sclerosis (ALS) resembling primary lateral sclerosis (PLS). A Japanese man developed muscle weakness in the distal part of the right upper extremity at age 59. At age 60 he presented with bradycinesia and rigidity. A neurological examination revealed fasciculation and increased deep tendon reflexes in the extremities. He developed decubitus and vesicorectal disturbance 2 months before his death at age 61. The neuropathological examination revealed not only prom-inent degeneration of the pyramidal tracts, evident in the internal capsule, but also loss of Betz's cells in the motor cortex. There was relative preservation of the neurons in the hypoglossal nuclei and anterior horns of the cervical and lumbar cord. In the anterior horn of the first sacral cord, there were small aggregates of lipofuscin-laden macrophages in locations from which large cells had presumably been lost. Bunina bodies and ubiquitin-immunoreactive neuronal inclusions were present in the anterior horn cells of the spinal cord. On the basis of these clinicopathological findings, we concluded that this case was one of sporadic ALS with predominant involvement of the upper motor neuron system and exhibiting features of PLS.

[Mediastinal germ-cell tumor associated with AML (M7)--the syndrome of mediastinal germ-cell tumors associated with hematologic neoplasia?].

In October 1992, a 36-year-old man was diagnosed as having mediastinum mixed germ cell tumor (stage II), and was treated with surgical operation and combination chemotherapy including VP16 (total VP16 dose; 1,500 mg/m2). After that, remission had been sustained, but leukocytosis (15,700/microliter) with 37% of peroxidase-negative blasts and thrombocytopenia developed in September, 1995. Bone marrow showed remarkable reticulin fibrosis and increase of atypical immature cells that were immunophenotypically factor VIII+/CD42+/CD61+. Thus, we diagnosed acute megakaryoblastic leukemia (M7). Based on no abnormality of chromosome 11q23 and no rearrangements of MLL gene, we diagnosed the syndrome of mediastinal germ-cell tumors associated with hematologic neoplasia. Furthermore, the neuron-specific enolase level was elevated (95.9 ng/ml). Soon after complete remission was reached by combination chemotherapy, the leukemia was relapsed, and the he died 3 months after the onset of leukemia. To our knowledge, this is the third case report of this syndrome in Japan and the first one of leukemia with high level of serum neuron-specific enolase.