Satou N

In vitro color change of composite-based resins

The adsorption of staining materials to resin restoratives was considered to be influenced by the physico-chemical properties of the resin-based monomers. To study the effects of the surface characteristics of resins on staining, we prepared five visible-light-cured experimental resins without fillers. Staining of these resins was colorimetrically measured. The staining solutions used were the Oil Orange and the Food Red 3 solutions. With the Oil Orange solution, the materials with higher hydrophobicity showed higher staining. With the Food Red 3 solution, the materials with higher water sorption showed higher staining.

Effects of various finishing methods on staining and accumulation of Streptococcus mutans HS-6 on composite resins

Abstract Microfilled and conventional composite resins, polished by different methods were tested for their staining and for bacterial accumulation in vitro. All 4 composite resins showed their characteristic staining tendencies for either Tobacco or Oil orange depending on their physicochemical properties and surface roughness. The effect of these factors seemed to depend on the substance adsorbed and the nature of the resins. Thus, in Tobacco solution immersion test, white point-polished surface showed the highest value of staining, which was followed by smooth surface and finished surface in this order, except one (Clearfil), in which the order was reversed. In the Oil orange solution immersion test, staining tendencies showed little correlation with surface roughness, but the hydrophobicity of the resin seemed to be an important factor. Polished surface accumulated more bacteria than smooth surface in the in vitro test of bacterial accumulation. However, no appreciable difference was observed among these 4 resins having an equal roughness.

Streptococcal Adherence on Various Restorative Materials

The adherence of Streptococcus sanguis ATCC 10556, S. sanguisATCC 10557, S. mutans Ingbritt, and S. mutans OMZ 176 to the surfaces of composite resins, amalgam alloys, and a Au-Ag-Pd alloy was measured. Adhesion was correlated with values for hydrophobicity and ζ-potential of the bacteria and the restorative materials. The hydrophobicity of the restoratives showed a positive correlation between the numbers of adherent S. sanguis cells, suggesting that hydrophobic interactions are important for the adherence of this bacterial species. In contrast, the numbers of adherent S. mutans cells showed a positive correlation with the ζ-potential of the restoratives, suggesting that electrostatic interactions are important in adherence of this bacterium.

Clinical evaluation of two posterior composite resins retained with bonding agents

Two hundred thirteen carious cavities were restored with two brands of chemically adhesive posterior composite resins by totally etching both the enamel and dentin walls after removing only the caries detector-stainable tissue and with no mechanical retention form in the cavity preparation. Most cavities were extensive, involving more than two surfaces in 74%. The dentin floor was not covered with cement although a spot lining was placed when the cavity was deep. All restorations were examined, usually after 4 years, by photographs and scanning electron microscope observation of replicas, and by criteria established by the U.S. Public Health Service. The materials and the technique proved to be clinically useful.

Curing performances of four experimental bis-GMA based binary monomer mixtures for dental visible-light-cured composite resin inlays

Visible-light-cured (VLC) composite resins have been widely accepted in dental clinics because of their aesthetic merit and ease in handling [1]. Visible light (VL) irradiation of composite resins at intraoral temperature is, however, said to be insufficient for maximum polymerization, leading to wear and discoloration problems [2-4]. To offset these drawbacks, a method for post-curing by heat has been introduced. These composites are now used as V L C inlay composite resins [5]. For the purpose of providing VLC inlay composite resins with improved clinical performances, it seems necessary to study the monomer mixture suitable for both VL and heat curing. Bisphenol A glycidyl dimethacrylate (bis-GMA) has been proven to be a useful base monomer for various dental composite resins [6]. Due to its high viscosity, however, bis-GMA has to be added with diluent monomers to render the handling and incorporation of filler easier [7]. Although some attempts have been made to examine the influence of diluent monomers on the curing behaviour of bis-GMA based binary monomer mixtures [8], such effects are still not well clarified. Therefore, the objectives of this study were, firstly, to prepare four bis-GMA based binary monomer mixtures and evaluate their curing performance by VL and by VL plus heat with residual monomer measurements and mechanical strength (diametral tensile strength) measurements and, secondly, to assess the effects of post-curing by heat on the properties of the once photo-cured copolymers. Table I shows the formulation of four bis-GMA (D-GMA, Shin Nakamura Co., Japan; lot no. 1105K) based binary monomer mixtures, in which one of the following four monomers was used as the diluent monomer: triethyleneglycol dimethacrylate

DENTAL APPLICATION OF POLYFUNCTIONAL URETHANE COMONOMERS TO COMPOSITE RESIN VENEERING MATERIALS

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.

Adhesion of streptococci to saliva-coated and uncoated composite-based resins

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.

Surface characteristics and staining of experimental visible light-cured unfilled resins

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.

Artificial Production and Natural Breeding of the Endangered Frog Species Odorrana ishikawae, with Special Reference to Fauna Conservation in the Laboratory

Odorrana ishikawae is listed as a class IB endangered species in the IUCN Red List and is protected by law in both Okinawa and Kagoshima Prefectures, Japan. Here, in an effort to help effectively preserve the genetic diversity of this endangered species in the laboratory, we tested a farming technique involving the artificial breeding of frogs, and also promoted natural breeding in the laboratory. Field-caught male/female pairs of the Amami and Okinawa Island populations were artificially bred using an artificial insemination method in the 2004, 2006, and 2008 breeding seasons (March to April). Although fewer than 50% of the inseminated eggs achieved metamorphosis, approximately 500, 300, and 250 offspring from the three respective trials are currently being raised in the laboratory. During the 2009 and 2010 breeding seasons, second-generation offspring were produced by the natural mating activities of the first offspring derived from the two artificial matings in 2004. The findings and the methods presented here appear to be applicable to the temporary protection of genetic diversity of local populations in which the number of individuals has decreased or the environmental conditions have worsened to levels that frogs are unable to survive by themselves.

Effect of tannic acid solution on collagen structures for dental restoration

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 Woessners 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.