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Citric Acid Solutions (citric + acid_solution)
Selected AbstractsBioadhesive Properties of a Polyaminoacidic Hydrogel: Evaluation by ATR FT-IR SpectroscopyMACROMOLECULAR BIOSCIENCE, Issue 7 2005Filippo Saiano Abstract Summary: The bioadhesive properties of a novel chemical hydrogel based on a polymer of protein-like structure, have been investigated by using ATR FT-IR spectroscopy. In particular, the copolymer PHG obtained by partial derivatization of PHEA with GMA was chemically crosslinked by UV irradiation at 313 nm. Crosslinked PHG was treated with water to obtain a swelled sample, named PHG-UV gel, that was brought into contact with a phosphate buffer/citric acid solution at pH 7.0 in the absence or in the presence of mucin at various concentrations (0.01, 0.1 and 1 wt.-%). Preliminary dynamic swelling studies have evidenced the occurrence of an interaction between the PHG-UV gel and the glycoprotein. This result was confirmed by ATR FT-IR measurements. A diffusion model using a solution of Ficks' second law was employed to determine the diffusion coefficient of water into PHG-UV gel as a consequence of adsorption and/or interdiffusion which occur at the PHG-UV gel/mucin solution interface. Experimental results suggest a potential use of PHG-UV gel to prepare bioadhesive devices. [source] Enamel dissolution in citric acid as a function of calcium and phosphate concentrations and degree of saturation with respect to hydroxyapatiteEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2003Michele E. Barbour The aim of this study was to investigate enamel dissolution in citric acid solutions as a function of solution calcium and phosphate concentrations and degree of saturation with respect to hydroxyapatite (DSHA). The primary relevance of the study is the development of soft drinks with reduced erosive potential. Nanoindentation was used to investigate changes in the hardness of polished human enamel surfaces after 120 s and 300 s exposure to solutions with pH 3.30 and a range of calcium and phosphate concentrations. All solutions were undersaturated with respect to hydroxyapatite, with 0.000 , DSHA , 0.295. A complex dependence of enamel softening on calcium concentration was observed. Substantial enamel softening occurred in solutions with calcium concentrations equal to or less than 120 mm (DSHA , 0.104), but there was little or no statistically significant softening of the enamel for calcium concentrations over 120 mm. This condition may be applicable to soft drink formulation. Furthermore, solutions with DSHA = 0.101 and different calcium/phosphate ratios resulted in different degrees of softening of the enamel. Hence, contrary to assumptions made in many models, enamel dissolution is not simply a function of DSHA, and individual calcium and phosphate concentrations are critical. [source] Human enamel dissolution in citric acid as a function of pH in the range 2.30,pH,6.30 , a nanoindentation studyEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2003Michele E. Barbour The objective of this study was to investigate the dissolution of human enamel in citric acid solutions over a wide range of pH. The in vitro conditions are considered to be relevant to soft drink-induced enamel erosion. Nanoindentation was used to investigate changes in the nanomechanical properties of polished enamel surfaces after exposure to citric acid solutions. Solutions used had 38.1 mmol l,1 citric acid and pH greater than 2.3 but less than 6.3 (2.30 pH 6.30). Samples were exposed to rapidly stirred, constant composition solutions for 120 s. Statistically significant changes in enamel hardness and reduced elastic modulus were observed after exposure to all solutions. There was an approximately linear dependence of enamel hardness on solution pH for 2.90 pH 6.30. Below pH 2.90, enamel is thought to have reached the lowest possible hardness value. The reduction in enamel dissolution caused by an increase in pH of a soft drink is likely to be small. Product modification to reduce the erosive potential of drinks may require additional methods such as addition of calcium salts. [source] Cytotoxicity analysis of EDTA and citric acid applied on murine resident macrophages cultureINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2007K. F. Amaral Abstract Aim, To assess the ex vivo cytotoxicity of EDTA and citric acid solutions on macrophages. Methodology, The cytotoxicity of 17% EDTA and 15% citric acid was evaluated on murine macrophage cultures using MTT-Tetrazolium method [3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide]. A total of 5 × 105 cells were plated in medium culture with 17% EDTA or 15% citric acid. Fresh medium was used as a control. Toxicity values were analysed statistically by anova and Tukey's test (P < 0.05) at short (0, 6, 12, 24 h) and medium periods (1, 3, 5, 7 days), using ELISA absorbance. Results, On the short term, both EDTA (0.253 nm) and citric acid (0.260 nm) exhibited cytotoxic effects on macrophage cultures (P < 0.05). On the medium term, statistical differences were observed (P < 0.05) between the groups. EDTA (0.158 nm) and citric acid (0.219 nm) were cytotoxic when compared with the control group; EDTA-reduced macrophage viability significantly more than citric acid (P < 0.05). Conclusions, Both EDTA and citric acid had effects on macrophages cells ex vivo, but citric acid was less toxic in periods from 1 to 7 days of use. [source] Human enamel erosion in constant composition citric acid solutions as a function of degree of saturation with respect to hydroxyapatiteJOURNAL OF ORAL REHABILITATION, Issue 1 2005M. E. BARBOUR summary, The objective of this study was to investigate human enamel erosion under constant composition conditions, as a function of solution degree of saturation (DS) with respect to hydroxyapatite. The experimental conditions were relevant to the initial stages of enamel erosion by soft drinks. Nanoindentation was used to compare enamel surface softening caused by a control mineral water and two citric acid solutions with DS = 0·000 and DS = 0·032, both having pH 3·30. Enamel hardness and reduced elastic modulus were measured after 0, 30, 60, 120, 300 and 600 s exposure. A statistically significant change in enamel hardness was detected after 30 s exposure to both citric acid solutions, indicating that nanoindentation is extremely sensitive to the initial stages of erosion. There was a statistically significant difference between the mechanical properties of enamel exposed to the two citric acid solutions after 30, 60 and 120 s. At these times, the solution with DS = 0·000 caused twice as much enamel softening as that with DS = 0·032. This demonstrates that it may be possible to design a soft drink with a low erosive potential and a good taste by a small change in DS, at a typical drink pH. [source] Salty and Sour Taste Characteristics and Risk of AlcoholismALCOHOLISM, Issue 6 2003Kristen A. Sandstrom Background: This study examined gustatory measures (intensity and hedonic values of salt and citric acid solutions) that have been reported to differentiate nonalcoholics who are at risk of alcoholism by virtue of having an alcoholic father (PHP) from those with no such paternal history (PHN). The study tested the hypothesis that PHPs perceive salty and sour solutions to be more intense and less pleasurable than do PHNs. Methods: A total of 112 nonalcoholic subjects (44.7% male and 40.2% PHP) provided intensity and pleasantness ratings for a series of salty and sour solutions in varying concentrations. Results: PHP subjects rated salty solutions as more unpleasant than PHN subjects. PHP subjects also showed higher mean sour intensity ratings and less preference for sour solutions than PHN subjects. Conclusions: This study replicates and extends prior findings of salty and sour taste differences as a function of paternal history of alcoholism. Further research is needed to replicate these findings in other populations and to examine their implications for the transmission of alcoholism risk. [source] | ||||||||||