Numerical comparison of artificial saliva recipes

Abstract no. 1276published_or_final_versio

Stability of tooth minerals in plaque fluid and saliva

Abstract no. 265published_or_final_versio

Detecting anions of human saliva by ion chromatography

Abstract no. 3007published_or_final_versio

Hydroxyapatite solubility in simple inorganic solutions using solid titration

Abstract no. 0082published_or_final_versio

Artificial salivas for in vitro studies of dental materials

OBJECTIVES: An artificial saliva (AS) of defined composition is necessary for testing the performance of materials that serve in the mouth as natural saliva is too variable. The chemistry involved is critically important. Many AS recipes can be found in the literature, but the stability of tooth material, i.e. hydroxyapatite (HAP), in most of these has not been addressed. In fact, few contain all major ionic components with concentrations in the physiological range. The aim of the present study was (a) to review reported AS formulae from their inception in 1931 to date, (b) to compare the stability of HAP in various reported AS, and (c) to investigate the individual effects of ionic components present in the reported formulae on the stability of HAP. METHODS: A computer algorithm, RAMESES, for solving multiple equilibrium equations, was employed for all calculations. RESULTS: There was a marked difference between two groups, i.e. those with and without the presence of Ca; those with Ca were supersaturated with respect to HAP in the physiological pH range, the saturation pH ranging from about 4.5 to 6.0. There was also an approximately 180-fold range in solubility at pH 7, due to the individual effects of components such as phosphate, carbonate and citrate. Acetate, lactate and sulphate showed smaller effects, others have no appreciable effect. CONCLUSIONS: All components and equilibria of relevance to saliva must be included in the system for detailed models. Continued systematic development of a standardized AS is essential

A mechanistic study on the photodegradation of Irgarol-1051 in natural seawater

The kinetics of the photoinduced degradation and transformation of the antifouling booster biocide, Irgarol-1051, in natural coastal seawater was studied. The measured first-order rate constant for the degradation of Irgarol-1051 was 4.02 ± 0.1 × 10-4 h-1, while the rate constant for the formation of 2-methylthio-4-tert-butylamino-6-amino-s-triazine (M1), the most dominant degradation product of Irgarol-1051, was 4.6 ± 0.1 × 10-5 h-1. This considerably slower rate suggested that the transformation of Irgarol-1051 to M1 may not be the predominant pathway of the photodegradation process. During the photodegradation study, a new s-triazine species was observed in the degradation mixtures which, together with M1, appeared immediately upon photolysis and continued to accumulate in the degradation mixture throughout the entire study duration. This is in contrast to the behaviour of the recently identified degradation product of Irgarol-1051, 3-[4-tert-butylamino-6-methylthiol-s-triazin-2-ylamino]- propionaldehyde (M2), which was only detected in the degradation mixture after a long induction period. High-resolution tandem mass spectrometric analysis hinted that the new degradation product (M4) may possess a terminal alcohol and is likely to be an N-allylic alcohol derivative of M1. This suggests that M4 may, indeed, be a precursor of M2 via redox transformation at its N-allylic alcohol functionality. © 2008 Elsevier Ltd. All rights reserved.link_to_subscribed_fulltex

A study of the partitioning behavior of Irgarol-1051 and its transformation products

Partitioning behavior of the antifouling booster biocide, Irgarol-1051 (2-methythio-4-tert-butylamino-6-cyclopropylamino-s-triazine), its production by-product, M3, and its environmental transformation products, M1 and M2, were studied. Octanol-water partition coefficients, log KOW, and organic matter-water partition coefficients, log KOC, of these s-triazines were measured by reversed-phase HPLC and a triphasic SPME equilibrium model, respectively. The average log KOW (±SD) of the four s-triazine species were: 4.39 ± 0.07 (M3); 3.38 ± 0.12 (Irgarol-1051); 2.92 ± 0.12 (M2) and 2.54 ± 0.11 (M1), while mean log KOC (±SD) of these species were: 2.47 ± 0.03 (M3); 2.16 ± 0.03 (Irgarol-1051); 1.97 ± 0.03 (M2) and 1.79 ± 0.04 (M1). These results were compared to reported physicochemical parameters of Irgarol-1051 in the literature. Partitioning behavior of these s-triazine species in the coastal environment revealed by their KOW and KOC were also discussed. © 2005 Elsevier Ltd. All rights reserved.link_to_subscribed_fulltex

Solid-phase extraction-fluorimetric high performance liquid chromatographic determination of domoic acid in natural seawater mediated by an amorphous titania sorbent

The feasibility of using sol-gel amorphous titania (TiO 2) as a solid-phase sorbent for the pre-concentration of domoic acid (DA), a potent amnesic shellfish poisoning (ASP) toxin, directly from seawater was explored. The sol-gel titania material is able to adsorb DA from seawater, via the formation of ester-linkage between the carboxylic moieties of DA and the Ti-OH groups on the sorbent surface, at low pH and desorb it at high pH. The chemisorption process is not significantly interfered by the seawater matrix. The optimum pH values for the adsorption and desorption of DA were found to be pH 4 and 11, respectively. The optimal sorbent loading for the batch-type solid-phase extraction of DA was 0.67 mg-TiO 2 ng-DA -1 and adsorption equilibrium was achieved in 2 h at room temperature. The desorbed DA in 500 μL of 0.1 M alkaline borate buffer can be directly derviatized by 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) in aqueous media for fluorimetric HPLC quantification. Analyte recovery, repeatability and detection limit of this titania SPE-fluorimetric HPLC determination are 89%, 6.2% and 120 pg-DA mL -1 (n = 7, P < 0.05), respectively, for a sample volume of 30 mL. This titania SPE technique should also be applicable to the pre-concentration of other polar carboxylate- and phosphonate-containing biomolecules and pharmaceuticals in complex and interfering environmental sample matrices. © 2006 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Radioembolization with yttrium-90 microspheres for inoperable advanced hepatocellular carcinoma (HCC)

Objective: Inoperable hepatocellular carcinoma (HCC) confers a grave prognosis. Radioembolization with yttrium-90 microspheres as selective internal radiation therapy (SIRT) was shown to a have favorable outcomes for HCC. We reported our series of patients with inoperable advanced HCC treated in a single institution. Materials and methods: Patients with inoperable HCC and evaluable target lesions were evaluated by hepatic angiography and macroalbumin aggregate (MAA) scan for feasibility for SIRT. Dose of yttrium-90 was decided by Body Surface Area (BSA) method with an aim to achieve dose to tumour ³200Gy and dose to normal liver <80Gy. Treatment outcomes including best local response rate, best local disease control rate, best overall objective response, disease control rate, progression-free survival (PFS), overall survival (OS) and toxicity were assessed. Univariate and multivariate analysis were also performed for any prognostic factors for PFS and OS. Results: 48 inoperable advanced HCC patients, majority of whom with tumour size ³8cm or portal vein invasion, were evaluated for SIRT. After pre-treatment hepatic angiography and macroalbumin aggregate (MAA) scan, 26 patients (54.2%) with a mean age of 61.6 years (range 36-84) were considered feasible and treated with SIRT and 24 patients had evaluable lesions for response assessment. Previous treatment for their HCC was performed in 15 patients (62.5%), including 11 patients (45.8%) who had received transarterial chemoembolization (TACE) before. Mean alpha-feto protein (AFP) was 1187.5ng/ml (range 2.0 to 10389.0 ng/ml). Mean radioactivity of yttrium-90 prescribed was 1.43 GBq (range 0.85 to 2.30 GBq). After a median follow up of 13.9 months, the best local response rate was 33.3% and the best local disease control rate was 54.2%. Median local PFS, overall PFS and OS survival was 3.3 months, 3.2 months and 11.6 months respectively. Patients belonging to Pugh-Child Class A enjoyed longer median OS survival (15.0 months) than those belonging to Pugh-Child B (4.3 months, p=0.014). Similarly, patients whose duration of AFP response ³9 months survived longer (median OS 19.9 months) than whose duration of AFP response <9 months (median OS 8.2 months, p=0.001). Four patients (16.7%) developed grade ³3 toxicity including 1 patient who had persistent radiation peptic ulcer requiring gastrectomy. Univariate analysis showed that radioactivity of yttrium-90 prescribed was prognostic of local progression-free survival (p=0.004), whereas portal vein invasion (p=0.018) and radioactivity of yttrium-90 prescribed (p=0.000) were prognostic of overall progression-free survival and radioactivity of yttrium-90 prescribed (p=0.005), portal vein invasion (p=0.021), dose to tumour (p=0.028) was prognostic factors of OS. Multivariate analysis revealed that duration of AFP response (p=0.011) was prognostic of overall progression-free survival and duration of AFP response (p=0.033) and Pugh-Child Class A (p=0.015) were prognostic of OS. Conclusion: SIRT with yttrium-90 microspheres for inoperable HCC patients produced promising treatment response

An in vitro comparison of nickel and chromium release from brackets

This study aimed at comparing amounts of nickel (Ni) and chromium (Cr) released from brackets from different manufacturers in simulated oral environments. 280 brackets were equally divided into 7 groups according to manufacturer. 6 groups of brackets were stainless steel, and 1 group of brackets was made of a cobalt-chromium alloy with low Ni content (0.5%). International standard ISO 10271/2001 was applied to provide test methods. Each bracket was immersed in 0.5 ml of synthetic saliva (SS) or artificial plaque fluid (PF) over a period of 28 days at 37ºC. Solutions were replaced every 7 days, and were analyzed by spectrometry. The Kruskal-Wallis test was applied. Amounts of Ni release in SS (µg L-1 per week) varied between groups from "bellow detection limits" to 694, and from 49 to 5,948.5 in PF. The group of brackets made of cobalt-chromium alloy, with the least nickel content, did not release the least amounts of Ni. Amounts of Cr detected in SS and in PF (µg L-1 per week) were from 1 to 10.4 and from 50.5 to 8,225, respectively. It was therefore concluded that brackets from different manufacturers present different corrosion behavior. Further studies are necessary to determine clinical implications of the findings