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Highly crystalline samples of cellulose triacetate (CTA) were prepared from cellulose I by heterogeneous acetylation in an equal amount mixture of acetic anhydride and toluene. Highly crystalline and oriented films of cellulose I from green alga Cladophora sp. was used as a starting material. Prepared samples were studied by FT-IR, solid-state ¹³C NMR, and X-ray diffraction. Spectroscopic data indicate a complete degree of acetylation. In the solid-state ¹³C NMR spectrum, each carbon atom appears only as a single resonance, indicating that the asymmetric unit in the CTA I crystal includes only a single chemical repeat unit. This behavior is in contrast with the currently accepted crystal structure of CTA I, in which the unit cell includes two parallel polymer chains. In the fiber X-ray diffraction, prepared samples show high crystallinity and good orientation. A new unit cell is proposed, and the crystalline structure was refined using molecular modeling. Possible conformations of the acetate side chains are also considered. The proposed models include a single polymer chain in a 21 helical conformation placed in a monoclinic unit cell with a = 0.5939 nm, b = 1.1431 nm, c = 1.046 nm, and γ = 95.4°. Agreement between observed and predicted diffraction intensities, compared both by visual methods and in terms of the crystallographic reliability index R, is good with R = 0.22.

Abstract:  Kraft lignins modified by radical sulfonation or alkaline oxygen treatment were rich in acidic groups, such as sulfonic acid, carboxylic acid, and phenolic hydroxyl groups, and were effective as soil-conditioning agents, especially because of their ability to trap aluminum ions eluted from soil under acidic conditions. Formation of complexes between aluminum ions and modified lignins was examined using potentiometric titration and 27Al nuclear magnetic resonance (NMR) spectroscopy. Changes in the titration curve of a modified lignin by the addition of aluminum ions suggest the release of protons after the formation of complexes between them. Disappearance of 27Al-NMR signals assigned to various aluminum ions by the addition of kraft lignin treated with alkaline oxygen was also attributed to the formation of complexes. The relative ease of proton release because of complex formation between a modified lignin and metal ions was as follows: Fe3+ > Al3+ > Cu2+ > Pb2+ > Mn2+ > Ca2+. This indicates that aluminum complexes are quite stable, and the aluminum ion is not exchanged with cations other than Fe3+.

In order to study adhesiondecalcification mechanisms of acid interactions with human hard tissues such as bones and teeth, the chemical interaction of five carboxylic acids acetic, citric, lactic, maleic, and oxalic and two inorganic acids hydrochloric and nitric with enamel and two synthetic hydroxyapatite HAp powders with, respectively, a high and a low crystallinity were analyzed using Xray photoelectron spectroscopy XPS, atomic absorption spectrophotometry AAS, and spectrophotometry S. Xray diffraction revealed that the crystallinity of the highly crystallized HAp was considerably higher than that of enamel while the crystallinity of the poorly crystallized HAp was similar to that of dentin and bone. XPS of acidtreated enamel demonstrated for all carboxylic acids ionic bonding to calcium of HAp. AAS and S showed for both HAps that all carboxylic and inorganic acids except oxalic acid extracted Ca significantly more than P, leading to a CaP ratio close to that of synthetic HAp 2.16 ww. Oxalic acid extracted hardly any Ca, but substantially more P, leading to a significantly smaller CaP ratio than that of HAp. AAS showed that the calcium salt of oxalic acid hardly could be dissolved, whereas the calcium salts of all the other acids were very soluble in their respective acid solution. These results confirm the adhesiondecalcification concept ADconcept previously advanced. Depending on the dissolution rate of the respective calcium salts, acids either adhere to or decalcify apatitic substrates. It is concluded that the ADconcept that originally dictated the interaction of carboxylic acids with human hard tissues can be extended to inorganic acids, such as hydrochloric and nitric acid. Furthermore, HAp crystallinity was found not to affect the adhesiondecalcification behavior of acids when interacting with apatitic substrates, so that the ADconcept can be applied to all human hard tissues with varying HAp crystallinity. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 56–62, 2002

This study examined the effect of tannic acid solution on dissolution of dentine collagen and morphological aspects of tendon collagen. Using root dentine, which was cut off from bovine anterior tooth, dentine powders were obtained by the pulverization and lyophilization. They were subject to an application of 1, 3, 5 or 10% tannic acid (TA) solution for 1, 3, 6, 12 or 24 h. TA-treated dentine powders were treated with 40% phosphoric acid (PA) for 30 s at 20 °C and additionally with trypsin. Released hydroxyproline in Woessner's assay after a hydrolysis in 6 N HCl at 110 °C for 20 h was assumed to be dissolved dentine collagen. Released hydroxyproline in a control sample without acid treatment decreased from 100 to about 60% with increased TA concentration of 1 to 10%, and decreased with increased incubation times of 1 to 24 h when applied by 5% TA solution. Scanning electron microscopy results established the morphological effect of their surface characteristics due to such treatments as 40% PA for 30 s and 5% TA for 6 h, or 40% PA after 5% TA treatment, yielding collagen structures protected by TA to attack from phosphoric acid.

The effect of filler content and size to property of composite resin using high purity spherical silica particles on microwave curing was examined by mechanical means and electron microscope observation to develop microwave-curing composite resin inlay. Increasing filler content in three kinds of filler particles (0.45, 0.96 and 1.46 μm) resulted in increasing compressive strength, diametral tensile strength and knoop hardness and indicated the highest values at the operative mixing limit. The effect of particle size was that the mechanical property of the 0.96 μm filled resin was highest, followed by 1.46 μm and 0.45 μm on the same filler content. The 0.96 μm filled resin had about the same knoop hardness on both surfaces of the cured sample, which means that uniform polymerization occurred in the cured sample. With electron microscope observation, the bubbles of about 1.0 μm and the cracks between the fillers and the matrix were observed in each cured resin. This is caused by the excessive absorption of microwave energy in fillers and surface treatment materials of fillers. Therefore, improvement of the composition of filler and surface treatment material of filler are needed, which makes it harder to absorb the microwave energy. ©©1999©Kluwer Academic Publishers

This experiment was designed to study the internal colour change of five experimental visible light-cured (VLC) resins and to deduce the relationship between staining and the physicochemical properties of the resins and a glass. The staining of the materials was measured colorimetrically, with immersion in two types of staining solution (Oil Orange or Food Red 3) for 70 days at 37°C. The water sorption, contact angle and zeta-potential of these samples were also measured. With the Oil Orange dye a positive relationship was observed only between staining and the contact angles, whereas with Food Red 3 dye a positive relationship was observed between staining and the zeta-potential and between staining and the water sorption. The results could allow a comparison of the relative contributions to staining made by physicochemical forces for the samples tested.

This study was to examine water uptake, contact angle and colour change vector in relation to the staining on the optically smooth surface in five experimental visible light-cured (VLC) bis-GMA-based resins. They were formulated from bis-GMA-based resins including 25 to 45 wt% TEGDMA which were accelerated by CQ/DMAEMA/BHT = 0.5/2/0.05 (wt%) to bis-GMA/TEGDMA resin matrix. Of the set resins including more than 25 wt% of TEGDMA, the resins including 30 to 45 wt% had less than 1.0% as bis-GMA residual monomer. Water uptake and solubility in bis-GMA-based resins including 35 wt% TEGDMA were the minimum of the resins tested. Contact angle decreased with increasing time over 70 days, from 67 to 62 degrees. Using the hydrophilic staining solution (food red 3), the values of colour change vector were 6 to 9 after immersing them for 70 days at 37 °C, whereas hydrophobic oil orange staining test had a range of 12 to 19. The change of water uptake with time of immersion correlated with that of the colour change vector. With the accelerated test, the minimum value was 4.55 in 65/35 (bis-GMA/TEGDMA) resin. Of the bis-GMA-based resins (25 to 45 wt% fraction of TEGDMA) the minimum value of water uptake and contact angle were obtained.

Kinetic analysis of thermogravi metric data in visible-light-cured composite restoratives has been carried out and a comparison was made with that for a conventional chemically-cured composite. The results reveal that the thermal decomposition of polymers as the base resin in the composites rnay be governed by a single process, and the value of activation energy is different in decomposing the base resins thermally. The different values suggest that the kinds of base resins and the catalysts may have an effect on the thermal decomposition.

New ceramic/resin composites were prepared by filling the intercrystal spaces of a porous-CaO·SiO2-based machinable ceramic with [methyl methacrylate (MMA) + triethylene glycol dimethacrylate (TEGDMA) + Bis-phenol A glycidyl dimethacrylate (Bis-GMA)] copolymers. The composites exhibited a hardness, smaller and analogous to that of bovine enamel. Weight-load cutting tests were performed on the composites and bovine enamel, employing diamond points driven by an air-turbine handpiece. While the applied load was increased stepwise, we measured the rotational cutting speed and the cutting volume. With the addition of the applied load, the rotational cutting speed decreased and the cutting volume increased. With incrementing applied load, the degrees of the decrease in the rotational cutting speed and the increase in the cutting volume for bovine enamel were well simulated by those for the composites. It was therefore speculated that the porous-ceramic/resin composites are suitable for typodont teeth in the dental preclinical cutting exercise, and that another potential use of the composites might be in the production of future machined dental prostheses.

For the analysis of blood urea, the author used several kinds of columns such as conventional ion exchange chromatographic column, ion ehromatographic column and reverse phase columns. The result of comparison for separation efficiency will be discussed and conventional ion exchange chromatographic column indicated a best separation efficiency. Prior to application to the columns, blood urea was treated with solid phase extraction (SPE) with a strong cation exchange column with SO3H functional group.

In this paper, we discuss two subjects concerned with solid phase extraction (SPE) and HPLC analysis of toxic compounds eluted to serum from materials used for medical devices. SPE and liquid-liquid extraction for serum toxic compounds were compared. Firstly, an analysis of a toxic and carcinogenic compound, 4,4'-methylenedianiline (MDA), from polyurethane sterilized by gamma-ray irradiation was studied. Serum MDA was analyzed to assess the potential MDA risk to patients exposed to PU medical devices. MDA was determined by reverse-phase HPLC using an eluent of a mixed solution of ammonium acetate and acetonitrile. An ODS column was used. Detection was carried out by an electrochemical detector (ECD). As liquid-liquid extraction was complex due to deproteinization followed by centrifuge separation and concentration, we substituted SPE. Serum MDA was satisfactorily recovered using Bond Elut C-18, Phenyl and Cyclohexyl columns. The recovery of serum MDA from Bond ElutR C-1, C-2, C-8 and Silica was unsatisfactory. Elution was carried out using methanol containing lM NH4.OH. SPE was superior to a liquid-liquid extraction due to an unnecessary of denroteinization, centrifuge separation and concentration.Secondly, we analyzed the toxic compounds, methyl methacrylate (MMA), N, N-dimethyl p-toluidine (DMPT), and benzoylperoxide (BPO), all of which are components of the dental material of polymethyl methacrylate (PMMA). PMMA is widely used as the composite resin. for the dental plate. BPO was converted to benzoic acid (BA) when in contact with DMPT or serum, therefore BA analysis is necessary for BPO determination. As these compounds exhibit a potential for residue as well as toxicity, determination method and safety evaluation are required. Analysis was by HPLC combined with SPE using a C-18 column in both methods.

Adherent bacterial cells on the surfaces of two dental porcelain ceramics, three composite resins and human enamel were examined using four types of bacteria strains. Their adherent cells were counted on saliva-coated and uncoated material surfaces after sonication, and contact angle and ζ potential were measured for each adherent cell tested. A correlation between contact angle and bacterial cells on an uncoated surface was found to be higher in two Streptococcus sanguis cells than in S. mutans Ingbritt and S. sobrinus OMZ 176, whereas there appeared to be a higher correlation between S. mutans Ingbritt or S. sobrinus OMZ 176 and ζ potential on the uncoated surface. On the saliva-coated surface, a significantly high correlation was found between the adherent cells, with the exception of S. sanguis ATCC 10 557, and the ζ potential. Contact angle and ζ potential values were small when the surfaces of the materials were coated with saliva, as compared with those on the uncoated surface. The sonication condition (120 s) of adherent cells on the surface of the material significantly depended on the types of bacteria cells, showing that S. mutans Ingbritt (>50–60%) had a greater removal percentage than the others (<50%). © 1998 Chapman & Hall

Urethane monomer/diluent monomer mixtures were used in dental composite resin veneering materials filled with various ratios of powder (filler)/liquid (comonomer), P/L. Hardness values of unfilled resins containing benzoyl peroxide only (BP0; 0.5 wt%), and filled resins (included trimethylol propane trimethacrylate (TMPT) composite filler) were tested. Significant increases in hardness were obtained with the use of TMPT composite filler in the resins. Also, their modulus values measured by bend test showed an increasing trend, compared to a commercial composite resin veneering material (a control sample; CONT) with a lower filler content (50 wt%). The DME–DPMDC/HPDM comonomer (dimethacryloxyethyl diphenylmethane-4,4′-dicarbamate/hydroxypropyl dimethacrylate), which showed a smaller fraction of surface porosity, gave greater mechanical strength values at P/L ratios of 0.55 (17.8 wt% filler content) to 1.20 (27.3 wt%) than a CONT resin. The coefficient of thermal expansion was smaller in urethane-based filling materials than a CONT resin. Also, greater activation energy of thermal decomposition was observed in the resin samples with P/L ratio 0.75 to 1.20 than in a CONT resin. Thermally-induced decomposition occurred with smaller weight loss in the experimental filled resins than in a CONT resin.

Elution of starting compounds as well as artifact compounds from medical-use polymer material was studied. Artifact formation during medical polymer fabrication, as well as the artifact formation during contact of medical polymer with body fluids, has been so often overlooked. The analysis of starting compound residue in medical-use polymer has previously only been discussed. In this paper, the author studied the importance of recognizing the artifact formation to attain reproducible recovery of compound of interest from complicated matrix; an appropriate pretreatment method to make compounds of interest free from admixtures in body fluids and to attain reproducible HPLC analysis. Artifact compounds must be identified prior to determination. In order to attain reproducible analysis in complicated matrix, appropriate recovery and isolation methods as a pretreatment method, are required. Chemical structure identification of newly found toxic compounds from dental material was carried out by high performance liquid chromatography (HPLC) - mass spectrometry (MS)-MS.Determination of these compounds to saliva was by HPLC combined with solid phase extraction. Selection of appropriate eluent was studied. The eluent selected was opposite from the conventionally speculated eluent, but the selected eluent has reproducibility and a scientific rationale.

Solid phase extraction (SPE) is an efficient pretreatment method to separate a compound of interest in complicated matrix such as body fluid, food, or in soil. Ultrafiltration is also a suitable pretreatment method to remove higher molecular weight compounds such as protein in body fluid. The latter method is also useful for differential analysis of free type from protein-bound type compound in body fluid. Free type compound after ultrafiltration will exist in filtrate. Previously ultrafiltration and SPE were carried out off-line and the former was done manually, which was troublesome for routine analysis. In this paper these pretreatment methods were successfully on-line combined and controlled by computer first by the author. Unfortunately this kind of equipment is not currently available in the market yet due to patent restriction.

Methyl methacrylate polymer, polysulphone, polycarbonate and CleafilR are widely used as the dental plate. During fabrication, there is a potential for toxic compound residue of methyl methacrylate, N,N-dimethyl p-toluidine, benzoylperoxide, benzoic acid, bisphenol A, 4,4'-dichlorodiphenylsulfone, triethyleneglycol dimethacrylate and bis phenol A diglycidylmethacrylate. This raises a safety concern as these compounds exhibit carcinogenicity and mutagenicity. The elution of these compounds to water, organic solvents and serum is determined to evaluate a risk to the patients. Analysis is by HPLC using a newly developed and sufficiently endocapped ODS column combined with UV detection. The eluted amount is generally proportional to the hydrophobicity of the organic solvent. Serum extracts hydrophilic compounds as well as hydrophobic compounds. Risk to the patients exposed by these compounds is not so significant.

Solid phase extraction (SPE) of blood urea is described. Differential analysis of free type and bound type blood urea analysis for diagnosis is important because free type urea is more essential causing symptom of uremia. The differential analysis is attained by ultrafiltration by centrifugation using a cellulose membrane with cut-off molecular weight of 10,000 daltons from native and acidified blood. Compared with SPE, liquid-liquid extraction is more problematic due to the formation of artifacts during extraction and condensation by evaporation. Artifacts were observed in solvent extraction as a result of reactions between the extraction solvent and the target compounds.

This study was designed to evaluate the bacterial adhesion to five types of experimental composite-based resins and a commercial composite resin used as a control. Physicochemical surface characteristics of composite resins with and without an artificial saliva coating were measured. The relationship between the numbers of adhering cells (Streptococcus sanguis, S. mutans and S. sobrinus) and surface characteristics was analysed. The values of contact angles and the number of adhering cells were small with saliva coating. S. sanguis ATCC 10557 showed a positive correlation (r=0.835, p<0.05) with the contact angles of uncoated resins, whereas no relationship was observed for saliva-coated resins. With S. mutans Ingbritt the cell numbers adhering to resins correlated strongly (p<0.01) with the values of zeta potential of resins for either saliva coated or uncoated. Electrical repulsion forces had a strong contribution to adherence of cells such as S. mutans and S. sobrinus which show a high absolute zeta potential.

We examined the curing behaviour by visible-light (VL) and by heat of three commercial VLC inlay composite resins and three commercial VLC direct-filling composite resins by isothermal differential scanning calorimetry (DSC) thermal analysis and DTA thermal analysis, respectively. It became evident that heat of curing with VL irradiation and activation energy for photo-polymerization differed among the composite specimens. The activation energies for VL curing of inlay composites tended to slightly exceed those of direct-filling composites. It also became clear that the activation energy for heat curing of one direct-filling composite was considerably larger than those of the other five composites. There was, however, no systematic difference in the activation energies for heat curing between inlay and direct-filling composites.

The response evaluation of the Compton suppression system is usually conducted in controlled experiments with specific radiation sources. However, such sources alone cannot be used to evaluate the advanced system designs to be used in the high background radiation field of a nuclear power plant. A computational code is required to evaluate such a system. We experimentally determined the responses of a Ge detector, a scintillation detector, and a Compton suppression system; and we evaluated the validity of the results using the EGS-4 Monte Carlo Simulation code. Results showed that when the Compton suppression system is simulated, high accuracy cannot be achieved without spending at least 100 hours developing the model for the peripheral structures of the detector and for the /spl gamma/-ray scattering. However, the experimental results agreed closely with the simulation results, and the EGS-4 code was validated to be applicable to the advanced system design.

Bromination of (I) in carbon disulfide yields 3,10‐dibromo‐9‐phenanthrol (III) via (II).