How useful is SBF in predicting in vivo bone bioactivity

Ceramics used for the repair and reconstruction of diseased or damaged parts of the musculo-skeletal system, termed bioceramics, may be bioinert (alumina, zirconia), resorbable (tricalcium phosphate), bioactive (hydroxyapatite, bioactive glasses, and glass-ceramics), or porous for tissue ingrowth (hydroxyapatite-coated metals, alumina). Applications include replacements for hips, knees, teeth, tendons, and ligaments and repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jaw bone, spinal fusion, and bone fillers after tumor surgery. Carbon coatings are thromboresistant and are used for prosthetic heart valves. The mechanisms of tissue bonding to bioactive ceramics are beginning to be understood, which can result in the molecular design of bioceramics for interfacial bonding with hard and soft tissues. Composites are being developed with high toughness and elastic modulus match with bone. Therapeutic treatment of cancer has been achieved by localized delivery of radioactive isotopes via glass beads. Development of standard test methods for prediction of long-term (20-year) mechanical reliability under load is still needed.

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Bioceramics: From Concept to Clinic

Bioceramics : from concept to clinic

High-strength bioactive glass-ceramic A-W was soaked in various acellular aqueous solutions different in ion concentrations and pH. After soaking for 7 and 30 days, surface structural changes of the glass-ceramic were investigated by means of Fourier transform infrared reflection spectroscopy, thin-film x-ray diffraction, and scanning electronmicroscopic observations, in comparison with in vivo surface structural changes. So-called Tris buffer solution, pure water buffered with trishydroxymethyl-aminomethane, which had been used by various workers as a "simulated body fluid," did not reproduce the in vivo surface structural changes, i.e., apatite formation on the surface. A solution, ion concentrations and pH of which are almost equal to those of the human blood plasma--i.e., Na+ 142.0, K+ 5.0, Mg2+ 1.5, Ca2+ 2.5, Cl- 148.8, HCO3- 4.2 and PO4(2-) 1.0 mM and buffered at pH 7.25 with the trishydroxymethyl-aminomethane--most precisely reproduced in vivo surface structure change. This shows that careful selection of simulated body fluid is required for in vitro experiments. The results also support the concept that the apatite phase on the surface of glass-ceramic A-W is formed by a chemical reaction of the glass-ceramic with the Ca2+, HPO4(2-), and OH- ions in the body fluid.

Solutions able to reproduce in vivo surface-structure changes in bioactive glass-ceramic A-W.

Titanium and titanium alloys are widely used in biomedical devices and components, especially as hard tissue replacements as well as in cardiac and cardiovascular applications, because of their desirable properties, such as relatively low modulus, good fatigue strength, formability, machinability, corrosion resistance, and biocompatibility. However, titanium and its alloys cannot meet all of the clinical requirements. Therefore, in order to improve the biological, chemical, and mechanical properties, surface modification is often performed. This article reviews the various surface modification technologies pertaining to titanium and titanium alloys including mechanical treatment, thermal spraying, sol–gel, chemical and electrochemical treatment, and ion implantation from the perspective of biomedical engineering. Recent work has shown that the wear resistance, corrosion resistance, and biological properties of titanium and titanium alloys can be improved selectively using the appropriate surface treatment techniques while the desirable bulk attributes of the materials are retained. The proper surface treatment expands the use of titanium and titanium alloys in the biomedical fields. Some of the recent applications are also discussed in this paper.

/pdf/surface-modification-of-titanium-titanium-alloys-and-related-176rvxu9wp.pdf

Surface modification of titanium, titanium alloys, and related materials for biomedical applications

Silica glass fibers were prepared from mixed solutions of tetraethylorthosilicate (TEOS) and hexamethyldisiloxane (HMDS). An addition of HMDS improves spinnability since the increase in the viscosity of spinnable solutions becomes moderate and the range of the amount of added water for the occurrence of spinnability is widened. Spinnable solutions are obtained when the ratio of silicon in HMDS to total silicon, r, ranges from 0 to 0.6. It is assumed that the fibers drawn from this system consist of linear polymeric particles with double or triple siloxane chains capped with trimethylsilyl groups. Gel fibers from the solutions of r≤0.5 were converted to visually colorless and transparent silica glass fibers by rapidly heating them at 600°C.

https://www.jstage.jst.go.jp/article/jcersj1988/97/1123/97_1123_208/_pdf

Preparation of silica glass fibers from tetraethylorthosilicate and hexamethyldisiloxane

Changes in Light Absorption Spectrum of the Cobalt-Containing Glasses Subjected to High Pressure

Sol‐Gel‐Derived TiO2 Film Semiconductor Electrode for Photocleavage of Water. Preparation and Effects of Postheating Treatment on the Photoelectrochemical Behavior.

The distribution of Ag + ions in the Ag 2 OB 2 O 3 and Na 2 OAg 2 OB 2 O 3 glasses was investigated by X-ray diffraction on the basis of electron radial distribution (ERD) analysis. There appeared peaks at about 3.5 and 6.5 A in the ERD curves of both glasses, which were ascribed to Ag + Ag + distances. It was suggested that Ag + ions formed pairs or clusters in both glasses. The distribution of Ag + ions in Na 2 OAg 2 OB 2 O 3 glasses was considered to be somewhat different from that in Ag 2 OB 2 O 3 glasses at higher concentrations of Ag 2 O.

X-ray diffraction study on Na2OAg2OB2O3 glasses

Generally, on the repeating of lithia-silica glass, it starts to crystallize at the temperatures near or below the softening point to convert into the polycrystalline material without deformation (M. A. Matveev, V. V. Velya. Steklo i Keramika, 16 [10] 14 (1959)).In the present study, various oxides were added as the third component to a lithia-silica glass of the composition, Li2O 25, SiO2 75mol%, and their effects on the crystallization of the base glass on repeating were investigated.It was found that there is a limit in the amount for each oxide, and the addition over the limit inhibits the crystallization of the glass giving rise to the deformation or surface crazing of the sample during repeating (Fig. 2 and Fig. 3). The limit of the amount of addition in mol%, for each of the oxides varied with the own property of the oxides as follows:(1) For each of the series of alkali- and alkaliearth-oxide, which acts as the glass network modifier in the glass structure, the limit decreases with the increase of the size of cation, i.e., The value of limit: NaO0.5>KO0.5>RbO0.5, MgO>CaO>SrO>BaO.For the oxides with the cation of about the same size but of the different valency, the oxide with the cation of the higher valency has always the higher limit, i.e., The value of limit: CaO>NaO0.5, SrO>KO0.5, BaO>RbO0.5(Fig. 6 and Table 8).(2) For the glass network formers (BO1.5, AlO1.5, PO2.5 and AsO2.5) and also for the imtermediates (BeO, PbO, CdO, ZrO2, CeO2, LaO1.5) the limit was generally low compared with that for the glass network modifiers, with the exception for the oxides of transition element (TiO2, MnO1.5, VO2.5, CrO1.5, FeO1.5, CoO, NiO) (Fig. 7 and Table 8).The structural explanations were made of the above results in terms of the polarizing power, and the ability of strengthening the glass network, of the cation in the oxides introduced.

Sumio Sakka

Papers

Preparation of silica glass fibers from tetraethylorthosilicate and hexamethyldisiloxane

Changes in Light Absorption Spectrum of the Cobalt-Containing Glasses Subjected to High Pressure

Sol‐Gel‐Derived TiO2 Film Semiconductor Electrode for Photocleavage of Water. Preparation and Effects of Postheating Treatment on the Photoelectrochemical Behavior.

X-ray diffraction study on Na2OAg2OB2O3 glasses

Effects of the Addition of Various Oxides on the Crystallization of Lithia-Silica Glass