Chemical process to separate iron oxides particles in pottery sample for EPR dating

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

Determination of the antimutagenicity of an aqueous extract of Rhizophora mangle L. (Rhizophoraceae), using in vivo and in vitro test systems

An aqueous extract of Rhizophora mangle L. bark is used as raw material in pottery making in the State of Espirito Santo, Brazil. This extract presents large quantities of tannins, compounds possessing antioxidant properties. Tannin antioxidant activity, as a plant chemical defense mechanism in the process of stabilizing free radicals, has been an incentive to studies on anti-mutagenicity. The present work aimed to evaluate possible antimutagenic activity of a R. mangle aqueous extract, using the Allium cepa test-system and micronuclear (MN) assay with blockage of cytokinesis in Chinese hamster ovary cells (CHO-K1). The Allium cepa test-system indicated antimutagenic activity against the damage induced by the mutagenic agent methyl methanesulfonate. A reduction in both MN cell frequency and chromosome breaks occurred in both the pre and post-treatment protocols. The MN testing of CHO-K1 cells revealed anti-mutagenic activity of the R. mangle extract against methyl methanesulfonate and doxorubicin in pre, simultaneous and post-treatment protocols. These results suggest the presence of phyto-constituents in the extract presenting demutagenic and bio-antimutagenic activities. Since the chemical constitution of Rhizophora mangle species presents elevated tannin content, it is highly probable that these compounds are the antimutagenic promoters themselves.

Confocal Laser Microscopic Analysis of Biofilm on Newer Feldspar Ceramic

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

Surface degradation of glass ceramics after exposure to acidulated phosphate fluoride

Objective: This study evaluated the surface degradation effect of acidulated phosphate fluoride (APF) gel exposure on the glassy matrix ceramics as a function of time. Material and methods: Disc-shaped ceramic specimens (N = 120, 10/per ceramic material) were prepared in stainless steel molds (inner diameter: 5 mm, height: 2 mm) using 6 dental ceramics: 3 indicated for ceramic-fused-to-metal (Vita Omega 900, Carmen and Vita Titankeramik), 2 for all-ceramic (Vitadur Alpha and Finesse (R) Low Fusing) and 1 for both types of restorations (IPS d. SIGN). The specimens were wet ground finished, ultrasonically cleaned and auto-glazed. All specimens were subjected to calculation of percentage of mass loss, surface roughness analysis and topographical description by scanning electron microscopy (SEM) before (0 min) and after exposure to 1.23 % APF gel for 4 min and 60 min representing short-and long-term etching effect, respectively. The data were analyzed using two-way ANOVA with repeated measures and Tukey` s test (alpha=0.05). Results: Significant effect of the type of the ceramics (p=0.0000, p=0.0031) and exposure time (p=0.0000) was observed in both surface roughness and percentage of mass loss values, respectively. The interaction factor between both parameters was also significant for both parameters (p=0.0904, p=0.0258). Both 4 min (0.44 +/- 0.1-0.81 +/- 0.2 mu m) and 60 min (0.66 +/- 0.1 - 1.04 +/- 0.3 mu m) APF gel exposure created significantly more surface roughness for all groups when compared to the control groups (0.33 +/- 0.2-0.68 +/- 0.2 mu m) (p<0.05). There were no significant differences in percentage of mass loss between the ceramics at 4 min (p>0.05) but at 60 min exposure, IPS d. SIGN showed the highest percentage of mass loss (0.1151 +/- 0.11). The mean surface roughness for Vita Titankeramik (0.84 +/- 0.2 mu m) and Finesse (R) Low Fusing (0.74.+/- 0.2 mu m) was significantly higher than those of the other ceramics (0.59 +/- 0.1 mu m - 0.49 +/- 0.1 mu m) and Vita Titankeramik (p<0.05) regardless of the exposure time. A positive correlation was found between surface roughness and percentage of mass loss for all ceramic materials [(r=0.518 (Vitadur Alpha), r=0.405 (Vita Omega 900), r=0.580 (Carmen), r=0.687 (IPS d. SIGN), r=0.442 (Finesse (R) Low Fusing), r=0.572 (Vita Titankeramik), Pearson's correlation coefficient)]. The qualitative SEM analysis showed evidence of corrosive attack on all of ceramics at varying degrees. Conclusions: The ceramics indicated for either metal-ceramic or all-ceramic restorations were all vulnerable to surface texture changes and mass loss after short-term and long-term APF gel exposure.

Polishing methods of an alumina-reinforced feldspar ceramic

The purpose of this study was to test the hypothesis that mechanical polishing methods of ceramic surfaces allow similar superficial roughness to that of glazed surfaces. Twenty-five Vitadur Alpha ceramic discs (5 mm x 2 mm) were prepared according to the manufacturer's specifications. All specimens were glazed and randomly assigned to 5 groups (n=5), according to finishing and polishing protocols: G1: glazed (control); G2: diamond bur finishing; G3: G2 + silicon rubber tip polishing; G4: G3 + felt disc/diamond polishing paste; G5: G3 + felt disc impregnated with fine-particle diamond paste. Next, surface roughness means (Ra - μm) were calculated. Qualitative analysis was made by scanning electron microscopy. Surface roughness data were submitted to ANOVA and Tukey's test at 5% significance level. G1 and G4 were statistically similar (p>0.05). G2 presented the highest roughness means (p<0.05) followed by groups G3, G5, G4 and G1 in a decreasing order. The hypothesis was partially confirmed as only the mechanical polishing (G4) produced similar superficial roughness to that of surface glazing, although finishing and polishing are technically critical procedures.

SEM evaluation of in situ early bacterial colonization on a Y-TZP ceramic: A pilot study

This study aimed to evaluate the effect of surface glazing and polishing of yttrium-stabilized tetragonal zirconia polycrystal ceramic on early dental biofilm formation, as well as the effect of brushing on the removal of adhered bacteria. Two subjects used oral appliances with polished and glazed samples fixed to the right and left sides. After 20 minutes, 1 hour, and 6 hours, the subjects manually brushed the samples on the right side. The samples were analyzed using scanning electron microscopy. Granular material was verified on the samples, especially on irregular surfaces. After 1 hour, there was no significant difference between glazed and polished surfaces in terms of bacterial presence. However, glazed surfaces tended to accumulate more biofilm, and brushing did not completely remove the biofilm. Polished surfaces seem to present a lower tendency for biofilm formation. Int J Prosthodont 2007;20:419-422.

SEM analysis of the in situ early bacterial colonization on two novel feldspathic ceramics submitted to different types of glazing

Aim: The aim of this study was to evaluate in situ, the early bacterial colonization on feldspar-ceramics submitted to different glazing. Methods and Materials: Fourteen standardized disc specimens (diameter: 5 mm, thickness: 1.5 mm) of each of two micro-particulate feldspathic ceramics (VM7 and VM13, Vita) were produced according to manufacturers' specifications for a total of 28 specimens (24 for the analysis of biofilm and 4 for topographic analysis analyzing the ceramic surfaces). Specimens from each type of ceramic were submitted to two different glazing methods composing four groups: VM7 glazed using glazing liquid Vita Akzent® 25 (G1) and glaze firing (G2), VM13 glazed using glazing liquid (G3) and glaze firing (G4). Six individuals (n=6) wore oral appliances with four ceramic specimens, fixed on the buccal face of the appliances. After 8 hours, each sample was evaluated for the presence (1) or absence (0) of bacterial colonization under a scanning electron microscope (SEM) on five randomly selected fields. The value for each sample was cumulative of the results observed in the fields. One sample from each group was evaluated under a SEM to verify the topographic pattern. Results: There was no difference with regard to bacterial colonization between the feldspar-ceramics and between the glazing types (Kruskal-Wallis non-parametric test). Conclusion: Feldspar-ceramics submitted to firing or glaze firing with Vita Akzent® 25 present a similar condition for in situ bacterial colonization. The similar topographic pattern of the ceramic surfaces seems to have influenced the bacterial colonization.

Influence of polishing procedures on the surface roughness of dental ceramics made by different techniques

The aim of this study was to evaluate the influence of 2 different surface polishing procedures - glazing (GZ) and manual polishing (MP) - on the roughness of ceramics processed by computer-aided design/computer-aided manufacturing (CAD/CAM) and conventional systems (stratification technique). Eighty ceramic discs (diameter: 8 mm, thickness: 1 mm) were prepared and divided among 8 groups (n = 10) according to the type of ceramic disc and polishing method: 4 GZ and 4 MP. Specimens were glazed according to each manufacturer's recommendations. Two silicone polishing points were used on the ceramic surface for manual polishing. Roughness was measured using a surface roughness tester. The roughness measurements were made along a distance of 2 mm on the sample surface and the speed of reading was 0.1 mm/s. Three measurements were taken for each sample. The data (μm) were statistically analyzed using analysis of variance (ANOVA) and Tukey's test (α = 0.05). Qualitative analysis was performed using scanning electron microscopy (SEM). The mean (± SD) roughness values obtained for GZ were: 1.1 ± 0.40 μm; 1.0 ± 0.31 μm; 1.6 ± 0.31 μm; and 2.2 ± 0.73 μm. For MP, the mean values were: 0.66 ± 0.13 μm; 0.43 ± 0.14 μm; 1.6 ± 0.55 μm; and 2.0 ± 0.63 μm. The mean roughness values were significantly affected by the ceramic type (P = 0.0001) and polishing technique (P = 0.0047). The SEM images confirmed the roughness data. The manually polished glass CAD/CAM ceramics promoted lower surface roughness than did the glazed feldspathic dental ceramics.

Effect finishing and polishing procedures on the surface roughness of IPS Empress 2 ceramic

Objective. To evaluate the surface roughness of IPS Empress 2 ceramic when treated with different finishing/polishing protocols. Materials and methods. Sixteen specimens of IPS Empress 2 ceramic were made from wax patterns obtained using a stainless steel split mold. The specimens were glazed (Stage 0-S0, control) and divided into two groups. The specimens in Group 1 (G1) were finished/polished with a KG Sorensen diamond point (S1), followed by KG Sorensen siliconized points (S2) and final polishing with diamond polish paste (S3). In Group 2 (G2), the specimens were finished/polished using a Shofu diamond point (S1), as well as Shofu siliconized points (S2) and final polishing was performed using Porcelize paste (S3). After glazing (S0) and following each polishing procedure (S1, S2 or S3), the surface roughness was measured using TALYSURF Series 2. The average surface roughness results were analyzed using ANOVA followed by Tukey post-hoc tests (α = 0.01) Results. All of the polishing procedures yielded higher surface roughness values when compared to the control group (S0). S3 yielded lower surface roughness values when compared to S1 and S2. Conclusions. The proposed treatments negatively affected the surface roughness of the glazed IPS Empress 2 ceramic. © 2013 Informa Healthcare.

Caracterização de terras pretas arqueológicas no sul do Estado do Amazonas

The Archaeological Dark Earth (ADE) soils are characterized by its high fertility, dark color, and presence of pottery fragments. Regarding the formation of ADE, the most widely accepted hypothesis is that anthropogenic processes involving pre-Columbian populations made them. The purpose of this study is to characterize ADE units located in the Southern Amazon Region, in the cities of Apuí and Manicoré. Seven ADE sites were selected, trenches opened and the soil profiles characterized morphologically. Then, samples of each horizon were collected for analyses of the following physical and chemical properties: particle size, water-dispersible clay, flocculation, soil bulk density, particle density, total porosity, pH in water and KCl solutions, Ca2+, Mg2+, K+, Al3+, available P, H+Al, and organic C. Also, total oxides, free oxides and amorphous forms were analyzed. The texture of the anthropic A horizon ranged from sandy loam to clay loam. The pottery fragments and lithic material were found in similar quantities and at similar depths in the A horizons of the studied soil profiles, suggesting some similarity between the anthropogenic factors of formation. The anthropic horizons of profiles P3, P4, and P7 had a eutrophic character and high to very high levels of available phosphorus, compared to P1, P2, P5, and P6, indicating the heterogeneity of the ADEs.

Celeida Tostes: o barro como elemento integrativo na Arte Conteporânea

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise rugosimétrica de duas cerâmicas odontológicas submetidas a diferentes tratamentos de superfície

Pós-graduação em Reabilitação Oral - FOAR

Efeito da escovação na formação in situ de biofilme dentário inicial e na rugosidade superficial em cerâmica de y-tzp após vitrificação e polimento

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da toxicidade oral de 90 dias(doses repetidas)do lodo de estação de tratamento de esgoto(LETE) em ratos wistar

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Propriedades multifuncionais do CaCu3Ti4O12: estudo dos mecanismos e suas aplicações

Pós-graduação em Ciência e Tecnologia de Materiais - FC