Development of bone-bonding hafnium metal and titanium-hafnium alloys by chemical surface modification

Hafnium (Hf) has attracted considerable attention as a component of biomedical titanium (Ti) alloys with low Young\u27s moduli and/or shape‐memory functionalities, because its cytotoxicity is as low as that of Ti. The drawback of metals is that their bone‐bonding ability is generally low. It is known that apatite formation in the body is a prerequisite for bone‐bonding. Although several chemical treatments have been proposed for preparing Ti for bone‐bonding, there have been no similar investigations for Hf. In the present study, NaOH‐ and heat‐treatments were applied to pure Hf and Ti‐Hf alloys and their bone‐bonding ability was assessed in vitro with the use of simulated body fluid (SBF). After NaOH‐ and heat‐treatments, anatase formed on alloys with low Hf content (20–40% (atom%) Hf); mixtures of sodium titanate and hafnium titanate formed on alloys with similar Ti and Hf content (60% Hf); and hafnium oxide formed on alloys with high Hf content (80% Hf and pure Hf). Precipitates of apatite were observed on all the metals in SBF, except for the alloy with 60% Hf. We speculated that the hafnium titanate formed on this alloy had a low apatite‐forming ability owing to its high negative surface charge, which inhibited P adsorption. The apatite‐forming abilities of the Ti‐Hf alloys strongly depended on their Hf content. The present results indicate that Hf‐based materials have good potential for bone‐bonding

Ion release from experimental Au-Pt-based metal-ceramic alloys.

OBJECTIVE: The aim of the study was to assess the effect of individual metallic elements within experimental Au-Pt-based dental alloys for porcelain veneering on ion release. METHODS: A binary Au-10at% Pt alloy (AP10) was designed as a parent alloy. Six ternary AP10-X (X=In/Fe/Sn/Zn) and four quaternary (AP10-In2)-Y (Y=Fe/Sn/Zn) alloys containing oxide-forming elements, X and Y, up to 2at% were prepared and ion release from the experimental alloys in deionized water and commercial soft drink was examined. For ion release determination samples with size 10 mm x 10 mm x 0.5mm were immersed in 20 ml of deionized water for 5 min. Samples were then removed and immersed in 20 ml of Sprite Light for a further 5 min, and 2h at 37 degrees C. The amounts of ions released in the test solutions were analyzed by inductively coupled plasma-mass spectrometry. RESULTS: When looking at individual elemental ion release, the order of the amount of dissolved ions was Fe>Zn>In>Sn. Among the base metal elements examined, Fe showed significantly higher levels of ion release than the other base metal elements for all three testing conditions (P<0.05). When looking at the effects of test solution on ion release from the alloys, Sprite Light caused significantly higher level of ion release than deionized water, with the exception of In in the ternary AP10-In1.0 and AP10-In1.7 alloys and the quaternary (AP10-In2)-Sn1.0 alloy, which showed similar or slightly greater amounts of ion release into deionized water. SIGNIFICANCE: Significant ion release was only observed from the Fe element. Sn and In elements showed less ion release than the Fe and Zn elements. Accordingly, Sn and In elements should be recommended as oxide-forming elements in Au-Pt-based metal-ceramic systems

Compositional dependence of the apatite formation ability of Ti–Zr alloys designed for hard tissue reconstruction

Ti–Zr alloys are expected to be novel biomaterials with low stress shielding owing to their lower Young’s moduli than pure Ti. The drawback of metallic biomaterials is that their bone-bonding abilities are relatively low. NaOH and heat treatments have been performed to provide Ti–50Zr with apatite-forming ability in the body environment, which is essential for bone bonding. However, the systematic compositional dependence of apatite formation has not been revealed. In the present study, NaOH treatment of Ti–Zr alloys with various compositions and bone-bonding abilities was assessed in vitro by apatite formation in simulated body fluid (SBF). The corrosion current density in NaOH aqueous solution and the amount of Na incorporated into the surface tended to decrease with increasing Zr content. The apatite-forming ability of the treated alloy significantly decreased when the Zr content was ≥60 atom%. This phenomenon is attributed to the (1) low OH content on the surface, (2) low Na incorporation into the treated alloy surface, which enhances apatite formation, and (3) low ability of P adsorption to the Ti–Zr alloy in SBF following Ca adsorption to trigger apatite nucleation. Although the adhesion of the titanate/zirconate layer formed on the surfaces to the substrates increased as Zr content increased, the adhesion between the apatite and the substrate was still low

Optical properties of base dentin ceramics for all-ceramic restorations.

The study was conducted to compare the optical parameters of VM7(®) M-shade base dentin ceramics (VITA, Germany) for all ceramic restorations to the chemical composition across the 3D-MASTER(®) shade system

Effect of Laser Emission Parameters on Mechanical and Physical Properties of Cast Pure Titanium

The objective of this study was to investigate the effect of laser beam parameters on the mechanical and physical properties of cast commercially pure titanium. Dumbbell-shaped test specimens (ISO6871) were cast with ASTM grades 2 and 3 Ti. The cast surfaces were laser-treated with various laser emission parameters (current: 200, 220, and 240 A; spot diameter: 1.0, 1.6 mm; pulse duration: 10, 1 ms) under argon shielding. Tensile testing was conducted at a crosshead speed of 1.0 mm/min. Data of tensile strength and elongation were statistically analyzed using ANOVA/Tukey\u27s test (=0.05). Hardness depth profiles were made with cross sections of rod-shaped specimens after laser treatments. Control specimens without laser treatment were also prepared. The laser-treated specimens showed significantly higher tensile strengths than those of control specimen for both grades 2 and 3 Ti. The specimens treated with 1.0 mm spot diameter indicated higher tensile strengths than those treated with 1.6 mm spot diameter for both currents (200 A and 240 A). The laser treatment decreased the subsurface hardness and increased the hardness between 75 m and 400 m in depth when compared to the hardness of control specimens. Laser surface treatment for cast commercially pure titanium modified integrity of cast surface and significantly improved mechanical and physical property

The effect of magnesium oxide supplementation to aluminum oxide slip on the jointing of aluminum oxide bars

The purpose of this study was to investigate the effect of modifying aluminum oxide slips with magnesium oxide (MgO) tocreate a jointing material for In-CeramR Alumina. Jointed In-CeramR Alumina bars with In-CeramR Alumina slips containing0－1.0 mass％ MgO were examined by a three-point bending test. Joint-free bars were also tested as controls.Fracture surfaces were evaluated by scanning electron microscopy. In addition, linear shrinkage and fracture toughnesswere assessed.　　The 0.3 mass％ MgO group showed the highest flexural strength among the jointed groups, and there were no statisticaldifferences between the joint-free control groups. The fracture surface of 0.3 mass％ MgO group showed increasedsintering densification with reduced micropore size. No linear shrinkage was observed with the addition of MgO to thealumina slip. Added MgO was also effective in boosting fracture toughness. The present findings indicate that the MgOsupplementedbinding material is useful for clinical applications

Ion release from experimental Au-Pt-based metal-ceramic alloys

Objective. The aim of the study was to assess the effect of individual metallic elements within experimental Au-Pt-based dental alloys for porcelain veneering on ion release. Methods. A binary Au-10 at% Pt alloy (AP10) was designed as a parent alloy. Six ternary AP10-X (X = In/Fe/Sn/Zn) and four quaternary (AP10-In2)-Y (Y = Fe/Sn/Zn) alloys containing oxide-forming elements, X and Y, up to 2 at% were prepared and ion release from the experimental alloys in deionized water and commercial soft drink was examined. For ion release determination samples with size 10 mm x 10 mm x 0.5 mm were immersed in 20 ml of deionized water for 5 min. Samples were then removed and immersed in 20 ml of Sprite Light (R) for a further 5 min, and 2 h at 37 degrees C. The amounts of ions released in the test solutions were analyzed by inductively coupled plasma-mass spectrometry. Results. When looking at individual elemental ion release, the order of the amount of dissolved ions was Fe > Zn > In > Sn. Among the base metal elements examined, Fe showed significantly higher levels of ion release than the other base metal elements for all three testing conditions (P < 0.05). When looking at the effects of test solution on ion release from the alloys, Sprite Light (R) caused significantly higher level of ion release than deionized water, with the exception of In in the ternary AP10-In1.0 and AP10-In1.7 alloys and the quaternary (AP10-In2)-Sn1.0 alloy, which showed similar or slightly greater amounts of ion release into deionized water. Significance. Significant ion release was only observed from the Fe element. Sn and In elements showed less ion release than the Fe and Zn elements. Accordingly, Sn and In elements should be recommended as oxide-forming elements in Au-Pt-based metal-ceramic systems. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved

Hyperreactivity of lymphocytes to streptolysin O and lack of plasma inhibitory factor (s) in patients with mucocutaneous lymphnode syndrome.

Lymphocyte activation by streptolysin O (SLO) and factors in the plasma which inhibit the response to SLO were examined in 19 patients with mucocutaneous lymphnode syndrome (MCLS), 54 age-matched (6 months-6 years) normal children, 41 normal children older than 6 years and 10 normal adults. In normal children younger than 6 years, the response to SLO was weak and in many cases no response was seen. On the other hand, in the patients with MCLS, the response of lymphocytes to SLO was high and comparable to the response in adults and children older than 6 years. The DNA synthesis of lymphocytes stimulated by SLO was inhibited almost completely by autologous or allogeneic plasma of many of the normal children and adults. The plasma of patients with MCLS did not inhibit, but rather enhanced the response to SLO. These results suggest that the increased response of lymphocytes to SLO and the lack of plasma inhibitory factors in patients with MCLS may be due to the immune response to the pathogen of MCLS, as yet undiscovered.</p