Influence of radiopacifying agents on the solubility, pH and antimicrobial activity of Portland cement

The aim of this study was to evaluate the interference of the radiopacifiers bismuth oxide (BO), bismuth carbonate (BC), bismuth subnitrate (BS), and zirconiun oxide (ZO) on the solubility, alkalinity and antimicrobial properties of white Portland cement (WPC). The substances were incorporated to PC, at a ratio of 1:4 (v/v) and subjected to a solubility test. To evaluate the pH, the cements were inserted into retrograde cavities prepared in simulated acrylic teeth and immediately immersed in deionized water. The pH of the solution was measured at 3, 24, 72 and 168 h. The antimicrobial activity was evaluated by a radial diffusion method against the microorganisms S. aureus (ATCC 25923), P. aeruginosa (ATCC 27853), E. faecalis (ATCC 29212) and C. albicans (ATCC 10231). The zone of microbial growth inhibition was measured after 24 h. The addition of BS and BC increased the solubility of the cement. The pH values demonstrated that all materials produced alkaline levels. At 3 h, BS showed lower pH than WPC (p<0.05). At 168 h, all materials showed similar pHs (p>0.05). The materials did not present antimicrobial activity for S. aureus, P. aeruginosas and E. faecalis (p>0.05). With regards to C. albicans, all materials formed an inhibition zone, mainly the mixture of WPC with ZO (p<0.05). The type of radiopacifier incorporated into WPC interfered with its physical and antimicrobial properties. ZO was found to be a viable radiopacifier that can be used with WPC.

Viscosity, pH, and moisture effect in the porosity of poly(furfuryl alcohol)

The poly(furfuryl alcohol) is highly indicated to obtain advanced carbonaceous materials due mainly to its good carbon yield (around 50%) and a controllable cure reaction. In the processing of some carbonaceous materials, such as monolithic vitreous carbon, it is necessary to make sure that the material has the smallest porosity to be used in nobler applications such as heart valves and aerospace integrated systems. In this manuscript, a design of experiments was used to study the influence of viscosity, pH, and moisture in the porosity of the cured material. This study shows that the moisture exerts a significant influence on the porosity and the trend of the results lead to conclude that lower viscosity and moisture, and the use of non-neutralized poly(furfuryl alcohol) resins lead to obtain materials with better quality. © 2012 Wiley Periodicals, Inc.

Antibiofilm activity, pH and solubility of endodontic sealers

Aim: To evaluate antibiofilm activity against Enterococcus faecalis, pH and solubility of AH Plus, Sealer 26, Epiphany SE, Sealapex, Activ GP, MTA Fillapex (MTA-F) and an experimental MTA-based Sealer (MTA-S). Methodology: Sealer samples were manipulated and stored for 2 or 7 days. Prepared sealers were evaluated by a modified direct contact test (DCT) for 5 h, 10 h or 15 h with biofilm previously induced on bovine dentine for 14 days. In the control group, the biofilm was not exposed to the sealers. The number of colony-forming units (CFU mL-1) in the remaining biofilm was determined. Sealer solubility was assessed by the percentage of mass loss after 15 h of immersion in distilled water. Sealer pH was measured at 5 h, 10 h and 15 h. Statistical analysis was performed using Kruskal-Wallis and Dunn or anova and Tamhane's T2 tests, at 5% significance. Results: At 2 days post-manipulation, the DCT showed that Sealapex and MTA-F were associated with a reduction in the number of bacteria in all 3 contact periods evaluated, compared with the control group (P < 0.05). At 7 days, Sealapex had the greatest antibiofilm action at 10 h and 15 h. Sealapex had the highest pH values 2 and 7 days post-manipulation. Regarding the solubility, at 2 days the highest values were observed for MTA-F, MTA-S, Sealapex and Activ GP (P < 0.05). At 7 days, MTA-S and MTA-F had greater solubility than the other materials (P < 0.05). AH Plus had the lowest solubility for both post-manipulation periods (P < 0.05). Conclusion: Sealapex and MTA-F were associated with a reduction in the number of bacteria in biofilms and had greater solubility. The high solubility and pH may be related to the antibacterial activity of these materials. © 2012 International Endodontic Journal.

New method to assess the pozzolanic reactivity of mineral admixtures by means of pH and electrical conductivity measurements in lime:pozzolan suspensions

A very simple method based on electrical conductivity and pH measurements was proposed for assessing reactivity of pozzolans. Calcium hydroxide: pozzolan water suspensions were monitored by means of measurements of electrical conductivity and pH values. In these suspensions, Ca(OH)(2) in solid state was initially present, being them, thus, saturated in this reagent. Three testing temperatures were selected (40, 50 and 60 degrees C). In the experiments carried out, calcium hydroxide was suspended in deionized water for yielding a lime saturated suspension. The addition of siliceous pozzolan (two types of rice husk ash RHA and two types of densified silica fume DSF were tested) to the saturated lime suspension can produce the unsaturation of the system, depending on the testing time, testing temperature and reactivity of pozzolan. When unsaturation was reached, the loss of electrical conductivity was higher than 30% and the variation of pH was higher than 0.15 units. These threshold values were selected for characterizing the reactivity of pozzolans by means of a proposed template, classifying the pozzolan in three different reactivity levels.

Radiopacity, pH and antimicrobial activity of Portland cement associated with micro- and nanoparticles of zirconium oxide and niobium oxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Correlation between pH and surface structural changes on human enamel submitted to different tooth whitening agents

The intense valuation of an esthetic pleasant smile guided the dentistry to bleached tooth due the popularity of whitening treatments. The consequence of it is an increasing interest in searching the effect of peroxides in hard dental tissues. The aim of this work was to analyze qualitatively in vitro the human enamel after three different bleaching treatments: Opalescence PF 10%, White Class 7.5% and Opalescence Xtra Boost 38%, correlating the structural changes in the surface of the enamel with its respective pH. A total of 40 sound human pre-molars were randomly divided into four groups of 10 elements, which had been immersed in artificial saliva during all the experiment. Bleaching protocols followed the recommendations of the respective manufacturers. Each bleached sample and control group were submitted to a scanning electronic microscopy analysis and compared with one another. Bleaching agents used in this experiment had modified the morphologic aspect of the surface of the dental enamel; however, it did not have correlation between the degrees of severity of the alterations and pH. There is a correlation between hydrogen peroxide concentration and changes in the enamel, where G4 showed more severe alterations, followed for G3 and G2.

Ph and antimicrobial activity of portland cement associated with different radiopacifying agents

The aim of this study was to evaluate the antimicrobial activity and pH changes induced by Portland cement (PC) alone and in association with radiopacifiers. Methods. The materials tested were pure PC, PC + bismuth oxide, PC + zirconium oxide, PC + calcium tungstate, and zinc oxide and eugenol cement (ZOE). Antimicrobial activity was evaluated by agar diffusion test using the following strains: Micrococcus luteus, Streptococcus mutans, Enterococcus faecalis, Pseudomonas aeruginosa, and Candida albicans. After 24 hours of incubation at 37°C, inhibition of bacterial growth was observed and measured. For pH analysis, material samples (n=10) were placed in polyethylene tubes and immersed in 10 mL of distilled water. After 12, 24, 48, and 72 hours, the pH of the solutions was determined using a pH meter. Results. All microbial species were inhibited by the cements evaluated. All materials composed of PC with radiopacifying agents promoted pH increase similar to pure Portland cement. ZOE had the lowest pH values throughout all experimental periods. Conclusions. All Portland cement-based materials with the addition of different radiopacifiers (bismuth oxide, calcium tungstate, and zirconium oxide) presented antimicrobial activity and pH similar to pure Portland cement.

Use of nanoparticulate zinc oxide as intracanal medication in endodontics: pH and antimicrobial activity

The aim of this study was to evaluate the pH and antimicrobial activity of micro or nanoparticulate zinc oxide (ZnO) pastes with or without calcium hydroxide (CH). The following medications were evaluated: microparticulate ZnO + polyethylene glycol (PEG) 400; nanoparticulate ZnO + PEG 400; PEG 400; CH + microparticulate ZnO + PEG 400 and CH + nanoparticulate ZnO + PEG 400. The pH was assessed between 12 hours and 28 days, using a digital pH meter. The antimicrobial activity against Enterococcus faecalis (ATCC-9212), Candida albicans (ATCC-10231), Pseudomonas aeruginosa (ATCC-27853), Staphylococcus aureus (ATCC-6538) and Kocuria rhizophila (ATCC-9341) was determined in triplicate using agar diffusion test. The results were submitted to Kruskal-Wallis/Dunn and ANOVA/Tukey tests with 5% significance. The highest pH values were found for CH+ZnO, with higher values for nanoparticulate ZnO after 12 hours and 21 days (p<0.05). CH+ZnO medication promoted higher growth inhibition against P. aeruginosa and lower against E. faecalis. Calcium hydroxide pastes have higher pH and antimicrobial activity when associated with either micro- or nanoparticulate zinc oxide.

Effect of inulin and oligofructose on the physicochemical, microbiological and sensory characteristics of symbiotic dairy beverages

The aim of this study was to verify the effect of inulin and oligofructose on the physicochemical, microbiological and sensory characteristics of symbiotic dairy beverages. Four formulations were made: 1) a control (C); 2) a sample with added Lactobacillus paracasei (P); 3) a sample with added L. paracasei and inulin (PI); and 4) a sample with added L. paracasei and oligofructose (PO). The probiotic population, pH, and acidity of the products were evaluated once a week for 21 days while refrigerated (5 +/- 1 degrees C). Possible contaminating microorganisms (coliforms, E. coli, and Salmonella spp.) were investigated after three days of storage. Sensorial acceptance and purchase intention were evaluated seven days after manufacture. Dairy beverages presented with L. paracasei populations above 8.50 log CFU/mL during the whole storage period. Significantly (p<0.05) lower pH values were observed in P and PI, and higher acidity values were found in all formulations throughout storage. The dairy beverages were considered to be a promising matrix for the probiotic microorganism L. paracasei. The prebiotic additions (inulin and oligofructose) did not interfere with the overall acceptance and intention to purchase the beverages.

Effects of pH and fluoride concentration of dentifrices on fluoride levels in saliva, biofilm, and biofilm fluid in vivo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Características físico-químicas de amidos modificados com permanganato de potássio/ácido lático e hipoclorito de sódio/ácido lático

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influência do banho de aspersão ante-mortem na eficiência da sangria e em parâmetros bioquímicos da carne bovina

To determine the effects of the pre-slaughter showering on some meat quality parameters, the biochemical changes in the Longus colli muscle and the bleeding efficiency were studied. Thirty-six Nelore steers were slaughtered in a commercial slaughterhouse. Eighteen animals were submitted to pre-slaughter showering; a control group of eighteen animals were slaughtered without showering. Samples were collected for evaluations in the muscle depth, in the anterior portion of longus colli muscle,just before chilling. Bleeding efficiency was evaluated through the ratio of muscle haemoglobin/blood haemoglobin using blood samples taken five seconds after bleeding, and muscle sample taken before chilling. Longus colli muscle samples were also used to determine glycogen, glucose, pH and acidity, 5, 24 and 48 hours after slaughtering. Multivariate methods were used to evaluate biochemical data and the bleeding efficiency data analysis followed the randomized block design. Haemoglobin retained in the muscle and bleeding efficiency were not affected (P > .05) by pre-slaughter showering. The pre-slaughter showering did not affect (P > .05) the glycolysis. There was a significant effect of time in glycogen, glucose, pH and acidity, in the first 24 hours.

Desenvolvimento e avaliação em simulador do ecossistema microbiano humano de uma bebida simbiótica à base de extratos aquosos de quinoa (chenopodium quinoa willd) e de soja

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Caracterização química da farinha de vísceras de avestruz e seu valor nutritivo para tilápia-do-Nilo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Atividade antimicrobiana de microrganismos probióticos em bebidas lácteas fermentadas

Pós-graduação em Microbiologia - IBILCE