A blue arsenomolybdic acid-crystal violet ion-associate pair paving the way for the field detection of arsenic in groundwater.

A simple visual colorimetric method based on arsenomolybdic acid-crystal violet ion-associate pair formation is described for the detection of As in groundwater at about 10, 25 and 50 µg L-1 levels. The pair exhibits light green coloration at ≤5 µg L-1 and blue colorations of distinctly different intensities at about 10, 25 and 50 µg L-1 concentrations of arsenic. High sensitivity is achieved by the preconcentration of As that entails simultaneous sorption of both As(III) and As(V) from groundwater on covellite (CuS) and, later, their elution as As(V), which subsequently participates in the formation of arsenomolybdic acid. The interference in the color development from PO43-ions that are as efficiently sorbed on CuS and eluted as the oxyanions of As is eliminated by their selective removal by Ce4+ ions under basic (pH ∼ 8.5) conditions. The removal is caused by the formation of cerium phosphate and its co-precipitation with calcium hydroxide. SiO42- ions do not interfere in the process as they are not sorbed by CuS. Groundwater containing ≤0.5 mg L-1 P and ≥200 mg L-1 total dissolved solid can be conveniently analysed by the method. The direct sensing of As(III) as well as As(V), the use of benign and easily available chemicals, the absence of any hazardous by-product, undiminished applicability in sunlight, the testing procedure lasting only for about 30 min, and rapidity are the major advantages of the method. Thus, the method is potentially well-suited for the on-site testing of groundwater potability under different regulations.

Effect of calcium hydroxide mixed with preservatives on physicochemical characteristics and sensory shelf-life of corn tortilla.

BACKGROUND: The objective of the study was to evaluate the physicochemical characteristics and shelf-life of corn tortilla stored at room temperature (25 °C) using aw modifiers (propylene glycol and glycerol) and pH modifiers (fumaric acid and sodium benzoate) as preservatives combined with calcium hydroxide. Detection thresholds were used to determine the maximum preservative concentration and calcium hydroxide. Physicochemical characterization and sensory evaluation were used to determine the stability and sensory shelf-life of tortillas. RESULTS: Control, calcium hydroxide, calcium hydroxide + fumaric acid, calcium hydroxide + glycerol, calcium hydroxide + propylene glycol, and calcium hydroxide + sodium benzoate treatments had rounded half-lives of 1, 2, 1, 2, 2, and 2 days respectively. Glycerol combined with calcium hydroxide resulted in tortillas with lower pH variations over time. Mold presence was the critical attribute causing tortilla rejection. CONCLUSION: The use of aw modifiers had a better effect in preserving corn tortilla, as the concentration of pH modifiers at detection threshold levels was not able to reach an optimum performance when combined with calcium hydroxide. © 2021 Society of Chemical Industry.

Remoción de hidróxido de calcio del canal radicular con irrigación manual, sónica y ultrasónica / Calcium hydroxide removal from the root canal by manual, sonic and ultrasonic irrigation

Introducción: Resulta fundamental la remoción por completo del hidróxido de calcio previo a la obturación del canal radicular que podría impedir la penetración de los selladores en los túbulos dentinarios. Objetivo: Determinar la efectividad de la eliminación de la medicación con hidróxido de calcio del canal radicular de dientes utilizando diferentes sistemas de irrigación. Métodos: Se irrigaron con hipoclorito de sodio 148 conductos radiculares rectos de dientes humanos. Se utilizó Ca(OH)2 mezclado con tinta negra para rellenar los canales radiculares y facilitar la visualización. Los dientes se dividieron en 5 grupos de acuerdo al protocolo de eliminación. En cada uno de los grupos, la extrusión apical se midió durante la etapa de irrigación por el método Huang X, después de la eliminación del Ca(OH)2, se seccionaron longitudinalmente y luego, en un portaobjetos, se observaron las muestras bajo un microscopio óptico. Finalmente, se analizó el contenido para cuantificar el grado de extrusión causado durante el procedimiento clínico. Se utilizó el test de ANOVA para el análisis estadístico Resultados: Se encontró diferencias significativas entre los grupos 1-2, 1-3, 1-4 y 1-5. El promedio de remanecía fue superior (66,4 por ciento). Los grupos 2 (41,6 por ciento) y 5 (34,8 por ciento) obtuvieron mayor eficacia en la remoción. ANOVA (α = 0,05) determina que no existieron diferencias significativas entre los 5 grupos. Conclusiones: Los dispositivos de activación ultrasónica mostraron una mayor eliminación de la medicación con hidróxido de calcio desde las paredes dentinarias a las técnicas manuales, sin embargo, demostró ser una terapia más invasiva debido a una mayor extrusión de detritus(AU)

Introduction: Root canal sealing should indispensably be preceded by complete calcium hydroxide removal, otherwise the latter might prevent the penetration of the sealers into the dentinal tubules. Objective: Determine the effectiveness of eliminating calcium hydroxide medication from the root canal of teeth using various irrigation systems. Methods: Preparation was conducted of 148 straight root canals of human teeth irrigating with sodium hypochlorite. The root canals were filled with Ca(OH)2 mixed with black ink to facilitate visualization. The teeth were divided into 5 groups in compliance with the removal protocol. Apical extrusion was measured in each group during the irrigation stage using the Huang X method. After Ca(OH)2 removal they were sectioned longitudinally and placed on a slide for observation of the samples under an optical microscope. Finally the content was analyzed to quantify the degree of extrusion obtained during the clinical procedure. The ANOVA test was used for statistical analysis. Results: Significant differences were found between the groups 1-2, 1-3, 1-4 and 1-5. Average remanence was above 66.4 percent. Groups 2 (41.6 percent) and 5 (34.8 percent) displayed higher removal efficacy. ANOVA (α = 0.05) did not determine any significant differences between the 5 groups. Conclusions: Ultrasonic activation obtained greater calcium hydroxide removal from the dentinal walls than manual techniques. However, it proved to be a more invasive therapy due to the greater detritus extrusion(AU)

Efeito antibiofilme e citotoxicidade do hidróxido de cálcio associado ao óleo essencial de Melaleuca alternifolia / Antibiofilm effect and cytotoxicity of calcium hydroxide associated with the Melaleuca alternifolia essential oil

Objetivo: Avaliar e comparar os efeitos antimicrobiano e antibiofilme, e a citotoxicidade promovida pela associação do hidróxido de cálcio ao óleo essencial de Melaleuca alternifolia (MA), em diferentes concentrações, e ao propilenoglicol (PG). Métodos: As seguintes medicações compuseram os grupos experimentais: G1) HC/MA 1%; G2) HC/MA 5%; G3) HC/MA 10%; G4) HC/MA 20%; e G5) HC/PG. Solução salina 0,85% e meio DMEM serviram como controle nos testes antimicrobianos e de citotoxidade em fibroblastos do ligamento periodontal humano (FbLP), respectivamente. A atividade antimicrobiana (n = 12) foi avaliada por meio do teste de difusão em ágar. O efeito antibiofilme (n = 12) imediato das medicações foi avaliado por meio do teste de viabilidade bacteriana em biofilmes de 72 horas de E. faecalis, formados sobre discos de dentina e tratados por sete dias com as medicações. Após a coleta microbiológica do biofilme remanescente, os discos de dentina foram imersos em meio estéril e armazenados por mais sete dias, para a análise do efeito antibiofilme residual das medicações, quando nova coleta microbiológica foi realizada. A atividade metabólica de FbLP foi avaliada por meio do ensaio colorimétrico MTS (n = 9). Os valores médios dos halos de inibição, em mm, das unidades formadoras de colônia, e o percentual de atividade metabólica celular foram analisados pelos testes Kruskal-Wallis e post hoc Dunn (α = 5%). Resultados:Todas as medicações experimentais apresentaram superior ação antimicrobiana e antibiofilme comparadas ao controle, solução salina (p < 0,05), e mantiveram viáveis os FbLP, semelhante ao controle DMEM (p > 0,05). Conclusão: A associação do óleo essencial de Melaleuca alternifolia, nas concentrações de 1%, 5%, 10% e 20%, ao hidróxido de cálcio promoveu excelente ação antimicrobiana, antibiofilme e biocompatibilidade com fibroblastos, de forma semelhante à associação com propilenoglicol.

Aim:To evaluate and compare the antimicrobial and antibiofilm effect, as well as the cytotoxicity of calcium hydroxide (CH) associated with the Melaleuca alternifolia (MA)essential oil, in different concentrations, and with propylene glycol. Methods: The following medications composed the experimental groups: G1) CH/MA 1%; G2) CH/MA 5%; G3) CH/MA 10%; G4) CH/MA 20%; and G5) CH/PG. Saline solution and culture medium DMEM were used as a control in antimicrobial and cytotoxicity tests in human periodontal ligament fibroblasts (PDLF), respectively. The antimicrobial activity (n = 12) was evaluated by the disk-diffusion agar method. The immediate antibiofilm effect (n = 12) of the medications was evaluated for bacterial viability in 72 hours-biofilms of E. faecalis, formed on the dentin disc surface and treated for seven days with medications. After microbiological sampling of the remaining biofilm, the dentin discs were immersed in sterile culture medium and stored for another seven days, for analysis of the residual antibiofilm effect of the medications, when a new microbiological sampling was performed. PDLF viability was evaluated by MTS colorimetric assay (n = 9). The mean values of the inhibition halos, in mm, the colony forming units, and the metabolic cell activity percentage were analyzed by means of Kruskal-Wallis and post hoc Dunn (α = 5%) tests. Results:All of the experimental medications presented higher antimicrobial and antibiofilm effects, when compared to the saline solution control (p < 0.05), and maintained the PDLF feasible, similar to the DMEM control (p > 0.05). Conclusions:The association of the Melaleuca alternifolia essential oil, at concentrations of 1%, 5%, 10%, and 20%, with calcium hydroxide promoted an excellent antimicrobial and antibiofilm activity, and biocompatibility with fibroblasts, similarly to the association with propylene glycol.

Graduate and Undergraduate Teaching of Primary Tooth Pulpectomy: A Comparison among Brazilian Dental Schools

Objective: To compare the teaching of the pulpectomy in primary teeth among graduate and undergraduate Brazilian dental schools. Material and Methods: From August 2015 to July 2016, an 11-question survey was sent to 44 graduate and 207 undergraduate dental schools. Data obtained were summarized using descriptive statistics. Results: The response rate was higher from graduate (56.8%) than undergraduate (41.1%) courses. Pulpectomy was taught by all participating schools. More than 90% of the undergraduate and graduate courses recommend the use of hand instruments for canals debridement, but the widening of root canals was advised in 69.4% of undergraduate and in 84% of graduate schools. Regarding the irrigatings, 1% sodium hypochlorite as a single irrigating solution was the most taught for both biopulpectomy and necropulpectomy. The iodoform-based Guedes-Pinto paste as the single indication was the preferred root canal filling material in undergraduate schools (30.6%), while the zinc oxidethickened calcium hydroxide paste as the single option was the most recommended in graduate courses (36%). Endodontic hand file associated with lentulo drill for filling root canals was recommended by most courses. Overall, biopulpectomy was performed in one session, while necropulpectomy led two sessions. Periapical radiograph for diagnosis and final obturation was the most adopted conduct by undergraduate (68.2%) and graduate (72%) schools. Gutta-percha and glass ionomer cement were preferred materials to seal the entrance of the pulp chamber. Conclusion: There was variability in the techniques and materials taught to perform pulpectomy in primary teeth among Brazilian graduate and undergraduate dental schools. Calcium hydroxide paste has been used in similar proportion to iodoform-based paste.

Efficacy of Needle, Ultrasonic, and Endoactivator Irrigation and Photon-Induced Photoacoustic Streaming in Removing Calcium Hydroxide from the Main Canal and Isthmus: An In Vitro Micro-Computed Tomography and Scanning Electron Microscopy Study.

OBJECTIVE: The aim of this in vitro study was to use high-resolution micro-computed tomography (micro-CT) and scanning electron microscopy (SEM) to compare the efficacy of four irrigation techniques [needle, ultrasonic, EndoActivator, and photon-induced photoacoustic streaming (PIPS)] in removing calcium hydroxide (Ca[OH]2) from the root canal and isthmus of maxillary premolars. METHODS: Twenty-four maxillary first premolars were selected based on the presence of isthmus regions on micro-CT scans. Root canals were instrumented with an F2 file using ProTaper rotary instruments and filled with Ca(OH)2 paste. Samples were stored at 37°C and 100% humidity for 1 week and randomly divided into four groups (n=6 each), according to irrigation technique. Samples were scanned with micro-CT before instrumentation, after Ca(OH)2 filling, and after irrigation. Ca(OH)2 reduction in the coronal, middle, and apical thirds and in the isthmus were assessed with three-dimensional image analysis. Next, specimens were split longitudinally, and canal walls were examined with SEM for Ca(OH)2 residues. Data were statistically evaluated with the Kruskal-Wallis and Mann-Whitney tests (p=0.05). RESULTS: The PIPS and ultrasonic groups showed greater Ca(OH)2 reduction in the apical third and higher cleanliness of the isthmus than the EndoActivator and needle irrigation groups (p<0.05). Ca(OH)2 residue scores in the PIPS and ultrasonic groups were significantly lower than those in the EndoActivator and needle groups in all regions of the root canals (p<0.05). There was no significant difference between PIPS and ultrasonic groups (p>0.05), or between EndoActivator and needle groups (p>0.05). CONCLUSIONS: PIPS and ultrasonic irrigation more effectively removed Ca(OH)2 from the main canal and isthmus in maxillary premolars than did EndoActivator or needle irrigation.

Efficacy of 3 different irrigation systems on removal of calcium hydroxide from the root canal: a scanning electron microscopic study.

INTRODUCTION: The purpose of this study was to evaluate the effectiveness of different irrigation systems on removing calcium hydroxide (Ca[OH]2) from the root canal by using a scanning electron microscope. METHODS: Forty extracted single-rooted teeth were divided randomly into 4 groups. Canal instrumentation was done, and the teeth were filled with Ca(OH)2 paste. One week later, 4 techniques were used for Ca(OH)2 removal. In the first group, the canals were cleaned with a master apical file. The second, third, and fourth groups were irrigated using the EndoVac (Discus Dental, Culver City, CA), EndoActivator (Dentsply Tulsa Dental Specialties, Tulsa, OK), and ProUltra (Dentsply Tulsa, Tulsa, OK) systems, respectively. All the groups were irrigated with 3 mL (18%) EDTA and 3 mL (1%) NaOCl for 1 minute. The canal walls were viewed, and the remaining amount of Ca(OH)2 was evaluated using a scanning electron microscope. A scoring system was used to assess the amount of residue Ca(OH)2 on each third of the canal. The obtained data for comparisons between the conventional irrigation needle and each device were statistically analyzed using the Mann-Whitney U test. RESULTS: To compare the 4 devices, the results were statistically analyzed using the analysis of variance test. CONCLUSIONS: None of the investigated techniques removed the Ca(OH)2 dressing completely. However, the EndoActivator System showed better results in removing Ca(OH)2 in each third of the root canals in comparison with the other techniques.

Análise da variação do pH de três pastas à base de hidróxido de cálcio, quando associadas ao PMCC, clorexidina e aloe vera / Analysis of the pH variation of three calcium hydroxide-based pastes, when associated with CMCP, chlorhexidine and aloe vera

O objetivo deste estudo, in vitro, foi analisar a variação do pH de três pastas à base de Ca(OH)2 e de cada um de seus componentes. Foram formados quatro grupos teste: GI: Ca(OH)2 + propilenoglicol (PG) + Aloe vera; GII: Ca(OH)2 + PG + paramonoclorofenol canforado (PMCC); GIII: Ca(OH)2 + PG + clorexidina 2% e grupo controle (água destilada). As pastas foram depositadas em frascos contendo 15 ml de água destilada e estes armazenados em estufa a 37° C. A mensuração do pH foi realizada em 7 intervalos de tempo. Os grupos testados apresentaram crescimento exponencial dos valores de pH registrados até 24 h e estabilização em 14 dias. Os controles apresentaram valores de pH inferiores em relação aos demais grupos (p<0,05 ­ ANOVA). A partir de t = 24 h, GII e GIII apresentaram maiores valores de pH em relação a GI (p<0,05 ­ Bonferroni). Numa segunda etapa, foram formados cinco grupos com os componentes individuais de cada pasta: GIc ­ clorexidina líquida 2%; GIIc ­ PG; GIIIc ­ PMCC; GIVc ­ hidróxido de cálcio P.A.; GVc ­ Aloe vera. GIVc e GVc apresentaram, respectivamente, os maiores e menores valores de pH registrados até o final do experimento (12,63 e 5,54). Conclui-se que o pH das pastas de Ca(OH)2 pode variar em função da sua composição, porém sempre se mantendo alcalino, mesmo quando associada à Aloe vera, cujo pH ácido foi registrado no presente estudo. No entanto, uma maior alcalinidade foi apresentada pelas pastas contendo clorexidina ou PMCC em sua composição.

The objective of this study, in vitro, was to analyze the variation of the pH of threeCa(OH)2 - based pastes and each of its components. There were four groups test: GI: Ca(OH)2 + propylene glycol (PG) + Aloe vera; GII: Ca(OH)2 + PG + camphorated paramonochlorophenol (CMCP); GIII: Ca(OH)2 + PG + 2% chlorhexidine and control group (distilled water). The pastes were deposited in vials containing 15 ml of distilled water and stored in a 37° C incubator. The measurement of pH was performed in 7 time intervals.The groups tested showed exponential growth of pH values recorded up to 24 h and stabilization in 14 days. The controls showed pH values lower than the other groups (p<0.05 ­ ANOVA). From t = 24 h, GII and GIII had higher levels of pH compared to GI (p<0.05 - Bonferroni). Subsequently, five groups were formed with the individual components of each paste: GIc - 2% chlorhexidine liquid; GIIc - PG; GIIIc - CMCP; GIVc - calcium hydroxide; GVc - Aloe vera. GIVc and GVc showed, respectively, the highest and lowest pH values recorded by the end of the experiment (12.63 and 5.54). It was concluded that the pH of Ca(OH)2 pastes may change depending on their composition, but always remained alkaline, even when associated with Aloe vera, whose acidic pH was recorded in this study. However, a higher alkalinity was presented by pastes containing chlorhexidine or CMCP in its composition.

Effect of temperature on short chain fatty acids (SCFAs) accumulation and microbiological transformation in sludge alkaline fermentation with Ca(OH)2 adjustment.

The effects of temperatures (15-55 °C) on the alkaline fermentation of sewage sludge were investigated in semi-continuous stirred tank reactors (semi - CSTR) at the pH of 10. The highest soluble chemical oxygen demand (SCOD) yield was obtained at 55 °C (764.2 mg/(gVS L d)), while the highest short chain fatty acids (SCFAs) yield was observed at 35 °C (319.8 mg/(gVS L d)), 1.5 times higher than SCFAs yield at 55 °C (209.5 mg/(gVS L d)). The proportion of the intercellular organic substances being transferred to the slime layer of sludge flocs increased from 29% at 15 °C to 54% at 55 °C. But only a small part of soluble organic substances in the slime layers was converted to SCFAs at 55 °C. The dewaterability of sludge was better at 35 °C than that at 55 °C. Microbiological community analysis showed the acid-producing microorganisms at the medium temperatures (25 °C and 35 °C) were more diverse and abundant than those at the low (15 °C) and high temperatures (55 °C). Clodtridium and Bacillus in Firmicutes and Gamma proteobacterium in Proteobacteria were the dominant functional bacterial species for high SCFA accumulation.

Detection of para-chloroaniline, reactive oxygen species, and 1-chloro-4-nitrobenzene in high concentrations of chlorhexidine and in a mixture of chlorhexidine and calcium hydroxide.

INTRODUCTION: Chlorhexidine (CHX) is likely to decompose into reactive by-products. This study evaluated the generation of 4-chloroaniline (pCA), reactive oxygen species (ROS), and 1-chloro-4-nitrobenzene in high concentrations of CHX and in a mixture of CHX and calcium hydroxide at different time points. METHODS: A gas chromatography method was developed to detect pCA and CHX by-products. Mass spectroscopy was used to elucidate the structure of compounds. The samples, which were kept at 36.5°C and 95% relative humidity during the study, were analyzed immediately and 7 days after preparation. RESULTS: pCA was detected in the 2% CHX solution and in the mixture of CHX and calcium hydroxide at all time points. pCA concentrations increased after storing under those conditions. The 2% CHX solution alone and the mixture of CHX and calcium hydroxide released ROS at all time points, but 1-chloro-4-nitrobenzene was not found. CONCLUSIONS: pCA and ROS were identified as by-products of the 2% CHX aqueous solution alone and as ointment base of calcium hydroxide paste.

Comparative evaluation of different chelators in removal of calcium hydroxide preparations from root canals.

BACKGROUND: This study compared the efficacy of 10% citric acid, 17% EDTA and 7% maleic acid (MA) with ultrasonic agitation in the removal of calcium hydroxide (CH) from root canals. METHODS: Seventy maxillary anterior teeth were enlarged to F3 using protaper files. Teeth were then divided into two groups: A and B. Group A was filled with (CH + iodoform + silicone oil) mixture and group B with CH and propylene glycol (PG). Ten teeth were divided into positive and negative control groups. The volume of CH preparations was estimated using spiral CT. After seven days, teeth in groups A and B were further divided into three subgroups based on irrigants used and CH was retrieved along with ultrasonic agitation. Volume analysis was undertaken using spiral CT. Mean percentage of CH removed was analysed using one-way ANOVA followed by Tukey's Honestly Significant Difference test. RESULTS: All irrigants removed (CH + PG) completely without any difference between them (p = 0.17). Removal of (CH + iodoform + silicone oil) was significantly higher for MA and citric acid than EDTA (p < 0.001). There was no difference between MA and citric acid. CONCLUSIONS: Concentrations of 7% MA and 10% citric acid were found to be superior to 17% EDTA in the removal of (CH + iodoform + silicone oil). (CH + PG) preparation was completely removed by all the irrigants.

Reductive dechlorination of chlorinated hydrocarbons as non-aqueous phase liquid (NAPL): preliminary investigation on effects of cement doses.

The reactivities of various types of iron mixtures to degrade chlorinated hydrocarbons (PCE, TCE and 1,1,1-TCA) in the form of non-aqueous phase liquids were investigated. The iron mixtures included a mixture of Fe(II) and Portland cement (Fe(II)-C), a mixture of Fe(II), Fe(III) and Ca(OH)(2) (Fe(II/III)-L), and a mixture of Fe(II), Fe(III), Ca(OH)(2), and Portland cement (Fe(II/III)-C). When the same amount of Fe(II) was used, Fe(II)-C was more reactive with chlorinated ethylenes (i.e. PCE and TCE) than Fe(II/III)-L. The reductive pathway for high concentrations of total PCE (i.e. above solubility) with Fe(II)-C was determined to be a combination of two-electron transfer, ß-elimination and hydrogenolysis. Increasing the cement dose from 5% to 10% in Fe(II)-C did not affect PCE dechlorination rates, but it did favor the ß-elimination pathway. In addition, when Fe(II/III)-C with 5%C was used, PCE dechlorination was similar to that by Fe(II)-C, but this mixture did not effectively degrade TCE. A modified second-order kinetic model was developed and shown to appropriately describe degradation of TCE at high concentrations. Fe(II/III)-L effectively degraded high concentrations of 1,1,1-TCA at rates that were similar to those obtained with Fe(II)-C using 10% C. Moreover, both increasing cement doses and the presence of Fe(III) increased dechlorination rates of 1,1,1-TCA, which was mainly through the hydrogenolysis pathway. The reactivity of Fe(II/III)-L was strongly dependent on the target compound (i.e. less reactivity with TCE, more with 1,1,1-TCA). Therefore, Fe(II/III)-L could be a potential mixture for degrading 1,1,1-TCA, but it should be modified to degrade TCE more effectively.

Characterization and analyses of acid-extractable and leached trace elements in dental cements.

AIMS: Determination of the elemental constitution and investigation of the total and leachable arsenic, chromium and lead in Portland cement, pure tricalcium silicate, Biodentine, Bioaggregate and mineral trioxide aggregate (MTA) Angelus. METHODOLOGY: The chemical composition of Portland cement, MTA Angelus, tricalcium silicate cement, Biodentine and Bioaggregate was determined using X-ray fluorescence (XRF). Measurements of arsenic, lead and chromium were taken with inductively coupled plasma-mass spectrometry (ICP-MS), following acid digestion on the hydrated material and on leachates of cements soaked in Hank's balanced salt solution (HBSS). RESULTS: All the cements investigated had a similar oxide composition with the main oxide being calcium and silicon oxide. Both the Portland cement and MTA Angelus had an additional aluminium oxide. The dental cements included a radiopacifying material. All the materials tested had higher acid-extractable arsenic content than the level set by ISO 9917-1 (2007) and an acceptable level of lead. Regardless these high levels of trace elements present in the materials, the leaching in HBSS was minimal for all the dental material tested in contrast to the high levels displayed by Portland cement. CONCLUSIONS: Dental materials based on tricalcium silicate cement and MTA Angelus release minimal quantities of trace elements when in contact with simulated body fluids. The results of acid extraction could be affected by nonspecific matrix effects by the cement.

The effect of calcium hydroxide on the steroid component of Ledermix and Odontopaste.

AIM: To investigate the chemical interaction of calcium hydroxide with the corticosteroid triamcinolone acetonide in Ledermix Paste and in Odontopaste, a new steroid/antibiotic paste. METHODOLOGY: Validated methods were developed to analyse the interaction of calcium hydroxide in two forms, Pulpdent Paste and calcium hydroxide powder, with triamcinolone acetonide within Odontopaste and Ledermix Paste. High-performance liquid chromatography (HPLC) was used to analyse the mixed samples of the pastes and calcium hydroxide. The concentration of triamcinolone acetonide within the pastes was determined over 0, 2, 6, 24 and 72-h time-points. All tests with the HPLC involved the testing of the standard with triplicate injections alongside the samples. All samples were tested in duplicate with each injected twice; therefore, four tests were performed for each investigation. Linearity, precision and specificity of the testing procedures and apparatus were validated. Descriptive statistics are provided. RESULTS: In both pastes, there was a marked rapid destruction of the triamcinolone acetonide steroid upon mixing with calcium hydroxide. Odontopaste suffered a lower rate of destruction of the triamcinolone acetonide component than Ledermix Paste, but both pastes showed very similar degrees of steroid destruction after 72 h. When using calcium hydroxide powder with Ledermix Paste, the triamcinolone was destroyed entirely and immediately. CONCLUSION: The addition of calcium hydroxide to Odontopaste or Ledermix Paste results in the rapid destruction of the steroid.

Morphological and chemical analysis of different precipitates on mineral trioxide aggregate immersed in different fluids.

The purpose of this study was to analyze the ultrastructures and chemical compositions of precipitates formed on mineral trioxide aggregate (MTA; White ProRoot MTA) immersed in distilled water (DW) or phosphate buffered saline (PBS), based on the attribution that MTA's bioactivity and sealing ability are influenced by its interaction with the external fluid environment. After 1 and 14 days of immersion, precipitates formed on MTA disks were analyzed using wavelength-dispersive X-ray spectroscopy electron probe microanalyzer with image observation function (SEM-EPMA; EPMA1601, Shimadzu, Kyoto, Japan), and Fourier transform-infrared (FT-IR) spectroscopy. On DW specimens, cubic-like crystals containing Ca, O, and C (17, 66, and 17 at% respectively) were produced. State analysis of calcium k(ß)spectrum also revealed calcium hydroxide. On PBS specimens, acicular-spherical and lath-like crystals with Ca/P molar ratios of 1.42 and 1.58 respectively were produced. In conclusion, the precipitates formed on DW specimens were identified as calcium carbonate and calcium hydroxide primarily, whereas the precipitates on PBS specimens were inferred to be amorphous calcium phosphate.

[Effect of calcium hydroxide concentration and cooking time of corn grain (Zea mays L.) nixtamalized, over physicochemical and rheological nixtamal characteristics]. / Efecto de la concentración de hidr6xido de calcio y tiempo de cocción del grano de maíz (Zea mays L.) nixtamalizado, sobre las caracteristicas fisicoquímicas y reológicas del nixtamal.

The effect of calcium hydroxide (Ca(OH)2) concentration and cooking time on physicochemical and pasting properties of maize, during traditional nixtamalization was evaluated. It was observed that the higher the Ca(OH)2 concentration and cooking time the higher the gelatinization temperature. Grain samples treated with 2 g/100 g of Ca(OH)2 and 60 min of cooking time presented higher calcium absorption (0.152 g/100 g) showing a significant increment (approximately 500 g/100 g). Results of X-ray diffraction showed that all the samples had X-ray diffraction pattern of starch type A, showing differences in the intensity of the diffraction as indicated by the percentage of cristallinity. The apparent viscosity of the nixtamal considerably decreased when the processes conditions were higher. Water retention capacity increased with temperature.

Dust exposure in indoor climbing halls.

The use of hydrated magnesium carbonate hydroxide (magnesia alba) for drying the hands is a strong source for particulate matter in indoor climbing halls. Particle mass concentrations (PM10, PM2.5 and PM1) were measured with an optical particle counter in 9 indoor climbing halls and in 5 sports halls. Mean values for PM10 in indoor climbing halls are generally on the order of 200-500 microg m(-3). For periods of high activity, which last for several hours, PM10 values between 1000 and 4000 microg m(-3) were observed. PM(2.5) is on the order of 30-100 microg m(-3) and reaches values up to 500 microg m(-3), if many users are present. In sports halls, the mass concentrations are usually much lower (PM10 < 100 microg m(-3), PM2.5 < or = 20 microg m(-3)). However, for apparatus gymnastics (a sport in which magnesia alba is also used) similar dust concentrations as for indoor climbing were observed. The size distribution and the total particle number concentration (3.7 nm-10 microm electrical mobility diameter) were determined in one climbing hall by an electrical aerosol spectrometer. The highest number concentrations were between 8000 and 12 000 cm(-3), indicating that the use of magnesia alba is no strong source for ultrafine particles. Scanning electron microscopy and energy-dispersive X-ray microanalysis revealed that virtually all particles are hydrated magnesium carbonate hydroxide. In-situ experiments in an environmental scanning electron microscope showed that the particles do not dissolve at relative humidities up to 100%. Thus, it is concluded that solid particles of magnesia alba are airborne and have the potential to deposit in the human respiratory tract. The particle mass concentrations in indoor climbing halls are much higher than those reported for schools and reach, in many cases, levels which are observed for industrial occupations. The observed dust concentrations are below the current occupational exposure limits in Germany of 3 and 10 mg m(-3) for respirable and inhalable dust. However, the dust concentrations exceed the German guide lines for work places without use of hazardous substances. In addition, minimizing dust concentrations to technologically feasible values is required by the current German legislation. Therefore, substantial reduction of the dust concentration is required.

Characterization of hydration products of mineral trioxide aggregate.

OBJECTIVE: To characterize the hydration products of white mineral trioxide aggregate (MTA). METHODOLOGY: Mineral trioxide aggregate, white Portland cement and bismuth oxide were evaluated using X-ray diffraction (XRD) analysis and Rietveld XRD. The cements were tested un-hydrated and after hydration and curing for 30 days at 37 degrees C. Analysis of hydrated cement leachate was performed weekly for five consecutive weeks from mixing using inductively coupled plasma atomic emission spectroscopy after which the cements were viewed under the scanning electron microscope to evaluate the cement microstructure. Quantitative energy dispersive analysis with X-ray was performed and atomic ratios were plotted. RESULTS: Both Portland cement and MTA produced calcium silicate hydrate (C-S-H) and calcium hydroxide (CH) on hydration. The tricalcium aluminate levels were low for MTA which resulted in reduced production of ettringite and monosulphate. On hydration the bismuth level in the hydrated MTA decreased; bismuth oxide replaced the silica in the C-S-H and was leached out once the C-S-H decomposed with time. Both MTA and Portland cement released a high amount of calcium ions which decreased in amount over the 5-week period. CONCLUSIONS: The hydration mechanism of MTA is different to that of Portland cement. In MTA the bismuth oxide is bound to the C-S-H and is leached out from the cement with time as the C-S-H decomposes. MTA produces a high proportion of calcium ions from CH a by-product of hydration and also by decomposition of C-S-H. The release of calcium ions reduces with time.

Influence of glass-ionomer cement on the interface and setting reaction of mineral trioxide aggregate when used as a furcal repair material using laser Raman spectroscopic analysis.

The prolonged setting time of mineral trioxide aggregate (MTA) is the main disadvantage of this material. This study analyzes the influence of glass-ionomer cement on the setting of MTA using laser Raman spectroscopy (LRS). Forty hollow glass molds were taken in which MTA was placed. In Group I specimens, MTA was layered with glass-ionomer cement after 45 minutes. Similar procedures were done for Groups II and III at 4 hours and 3 days, respectively. No glass ionomer was added in Group IV, which were then considered as control samples. Each sample was scanned at various time intervals. At each time interval, the interface between MTA and glass-ionomer cement was also scanned (excluding Group IV). The spectral analysis proved that placement of glass-ionomer cement over MTA after 45 minutes did not affect its setting reaction and calcium salts may be formed in the interface of these two materials.

Sewage sludge stabilisation with calcium hydroxide: effect on physicochemical properties and molecular composition.

Raw primary sewage sludge (Wastewater Treatment Plant of Krotoszyn, SW Poland) and its mixtures with 3%d, 6%d, 9%d, 12%d and 24%d of calcium hydroxide were stabilised for 1 and 35 days. Changes of the sludge physicochemical properties and molecular composition, caused by alkaline agent in course of stabilisation process, are recognised. A basic physicochemical data on the sludge cake and filtrate after 1 and 35 days of stabilisation process are given. Soxhlet extracts from the sludge cakes stabilised for 35 days as well pyrolysis and pyrolysis in situ methylation (using tetramethylammonium hydroxide-TMAH) products of respective pre-extracted cake residues were analysed by gas chromatography-mass spectrometry (GC-MS). Increase of calcium hydroxide concentration in the sludge mixture causes enhanced ammonia release, preferential hydrolyses of fats and proteins from the sludge macromolecular network and transformation of free fatty acids contained in the sludge lipids, as well as these released hydrolytically, to their calcium salts. The sewage sludge stabilisation with calcium hydroxide has no effect on homological assemblage and content of unbound stanol and sterol compounds in the sludge lipids and these bound into macromolecular network. Biogenic n-alkanes and anthropogenic linear alkylbenzenes were detected as minor components in the lipids and pyrolytic products from the pre-extracted cake residue, respectively. The alkaline agent used for the sludge stabilisation accelerates equilibration of the process and reduces content of pathogenic microorganisms.