Intercalation and dynamics of hydrated Fe2+ in the vermiculites from Santa Olalla and Ojén

Although the intercalation of Fe3+ into layered phyllosicilicates-especially into smectites-attracted much attention in the past two decades, the information about Fe2+ loaded phyllosilicates is sparse. Here we present an investigation of the Fe2+ exchanged vermiculites from Santa Olalla and Ojén (Andalusia, Spain) by means of Mössbauer spectroscopy. The room temperature Mössbauer spectra are very similar to those of the starting compounds (Na forms) except for a decrease of the contribution of structural Fe3+ and a concomitant increase of the contribution of Fe2+ sites, indicating an internal redox process. The extent of this redox reaction is different for the two vermiculites. Thus, the intercalated Fe2+ acts as an electron mediator from the external medium to the structural Fe3+ ions. A new component attributable to intercalated Fe2+ is practically invisible in the room temperature Mössbauer spectra, but increases strongly and continuously during cooling to 4.2 K, where it is the dominant feature of the Mössbauer patterns. At 4.2 K, its quadruple splitting amounts to 3.31 mm/s, which is in excellent agreement with the quadrupole slitting of Fe2+ coordinated to six water molecules in a highly symmetric octahedral arrangement. The strong decrease of the Mössbauer-Lamb factor of this component with increasing temperature indicates a weak bonding of the Fe 2+ in the interlayer space

Thermal stability of Trancos montmorillonite pillared by alumina and alumina-lanthana

Se ha investigado el efecto de diversos tratamientos térmicos sobre la estructura porosa de una montmorillonita denominada Trancos que dan lugar a pilares de óxido de aluminio una, y óxido de aluminio-lantano, la otra. Para ello, se han usado las técnicas de difracción de rayos X, adsorción de nitrógeno, microscopía electrónica de barrido y espectroscopia infrarroja de transformada de Fourier. Los diagramas de difracción de rayos X de las muestras iniciales presentan espaciados basales ligeramente superiores a 18 Â. £1 óxido de lantano posee un efecto negativo sobre la estabilidad térmica de los pilares, pero aumenta la acidez de tipo Brönsted en la muestra no tratada.The effect of various thermal treatments on the porous structure of Trancos montmorillonite which give rise to pillars of alumina and alumina-lanthana was investigated by X-ray diffraction (XRD), nitrogen adsorption measurements, scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The XRD patterns of the original samples correspond to a basal spacing slightly higher 18 Â. The lanthana causes a negative effect on the thermal stability of the pillars but it enhances the Brönsted acidity of the fresh sample

Génesis, constitución y propiedades de yacimientos de caolín de Sierra Morena occidental

Se ha estudiado la mineralogía y génesis de seis yacimientos de caolín situados en las provincias de Huelva y Sevilla. En dos de estos yacimientos el de Riotinto y Traslasierra (Huelva) el caolín se ha originado a partir de rocas volcánicas en el primer caso por un lixiviado sulfúrico y en el segundo por actividad hidrotermal. En los yacimientos de S. Telmo y Sta. Barbara (Huelva) y en el de el Alamo (Sevilla) la alteración a caolín se ha efectuado sobre pizarras paleozoicas asignándose al primero un origen meteórico y al segundo un origen hidrotermal. En el yacimiento de Almonaster el material caolinítico se ha originado por alteración meteórica de una diorita estando constituido por una caolinita de baja cristalinidad. Se dan también en este estudio datos tecnológicos para el mejor aprovechamiento cerámico de los materiales de estos yacimiento

Efecto de la motivación sobre la higiene oral: valoración mediante el índice de placa de Quigley-Hein modificado por Turesky

Objetivo. Estudiar el efecto de una intensa motivación sobre la higiene oral de los pacientes. Pacientes. Cuarenta y seis alumnos del primer curso del ciclo superior “Higiene Bucodental” del IES Santa Aurelia de Sevilla, 10 hombres (21,73%) y 36 mujeres (78,26%), con edades comprendidas entre los 18 y 30 años.Material y métodos. Se ha utilizado como índice de higiene oral el índice de placa de Quigley-Hein modificado por Turesky (IPQHT). La motivación se mantuvo de forma muy intensa (al menos 3 horas diarias) a lo largo de todo el estudio. Los alumnos estuvieron 48 horas sin cepillarse antes del primer registro y, tras éste, utilizaron su técnica habitual de cepillado durante todo el estudio. Resultados. El IPQHT medio basal fue de 3,11 +- 0,54. A las 48 horas del inicio de la motivación el QHT se había reducido hasta 1,50 +- 0,50 (p <0,05 vs basal), a los siete días había caído hasta 1,31 +- 0,49 (p <0,05 vs basal) y a los 21 días el QHT medio era de 1,40 +- 0,54 (p <0,05 vs basal). Conclusiones. Una buena motivación, incluso sin la introducción de nuevas técnicas de cepillado dental, puede reducir de forma muy significativa los niveles de placa, estimulando las prácticas habituales de higiene oral en los pacientes.The purpose of this study was to investigate the effect of an intense motivation on the oral hygiene of 46 dental hygienist students. To assess oral hygiene the Turesky modification of the Quigley-Hein plaque index was used. After 48 h without any oral hygiene procedure, baseline scores of the plaque index of the patients were registered. Then, strongly motivation was maintained during three hours/day and the patients used their normal toothbrushing practices. The plaque index was determined after 2, 7 and 21 days. The mean baseline score of plaque index was 3,11 +- 0.54. After 2 days the mean plaque index decreased to 1.50 +- 0,50 (p< 0.05 vs basal), after 7 days still reduced to 1.31 +- 0.49 (p< 0,05 vs basal), and after 21 days the mean plaque index was 1.40 +- 0.54 (p<0.05 vs basal). We conclude that intense and maintained motivation can reduce significantly plaque index without introducing any new toothbrushing technique

Placa bacteriana: conceitos básicos para o higienista bucodental

La placa bacteriana es el factor etiológico principal de las dos enfermedades bucodentales de mayor prevalencia, la caries y la enfermedad periodontal. El higienista bucodental y colaborador del odontoestomatólogo en la aplicación del programa de control de placa, debe conocer en profundidad la microbiología de la placa bacteriana dental, así como los mecanismos implicados en su patogenicidad cariogénica y periodontal, aspectos que se revisan a continuación.Dental plaque is the main etiologic factor in caries and periodontal disease. The dental hygienist must to know to the microbiology of dental plaque and the mechanisms implicated in its patogenicity, topics that are reviewed.La plaque bacteriene est le facteur tiologique principal des deux maladies buccales de plus grande prevalence, la caries et la maladie parodontale. L’higieniste dentaire en tant que professionel de la prevention bucco-dentaire et collaborateur de l’odonto-estomatologiste dans l’application de promgramme de controle de plaque, doit connaitre en profondeur la microbiologie de la plaque bacterienne dentaire, de meme que les mecanismes de la pathogenicité carlogenique et parodontale, aspects qui sont revisés par la suite.La placa batterica è il fattore eziologico principale delle due malettie buccodentali di maggiore prevalenza, la cariee la malattia parodontales. L’igienista buccodentale, in quanto profesionista sanitario specializzato nella prevenzione buccodentale e collaboratore dell’odontostomatologo nell’apllicazione del programa di controllo della placa, debe conoscere in profondità la microbiología della placa batterica dentale, così come i meccanisimi implicati nella sua patogenicità cariogenica e periodontale, aspettiche verranno revisati in seguito.A pplaca bacteriana é factor estológico principal das doencas buccodentais de maior prevalencia, a cárie e a doenca periodontal. O higienista bucodental, como profissional sanitário especializado na prevencazo bucodental e colaborador do odontoesmatólogo na aplicacao do progama de controle de placa, debe conhecer em profundidade a microbiología da placa bacteriana dentária, bem como os mecanismos envueltos na sua patogenicidade cariogénica e periodontal, aspectos esses que a seguir se revêm

High prevalence of apical periodontitis amongst type 2 diabetic patients

The aim of this work is to study the prevalence of AP in patients with and without type 2 diabetes mellitus. In a retrospective cohort study, the records of 38 subjects with diabetes and 32 control subjects were examined. All participants underwent a full-mouth radiographic survey incorporating 14 periapical radiographs. The periapical region of all teeth, excluding third molars, was examined. Periapical status was assessed using the periapical index score. Statistical analyses were conducted using the Cohen’s j test, analysis of variance and logistic regression. Apical periodontitis in at least one tooth was found in 81.3% of diabetic patients and in 58% of control subjects (P ¼ 0.040; OR ¼ 3.2; 95% CI ¼ 1.1– 9.4). Amongst diabetic patients 7% of the teeth had AP, whereas in the control subjects 4% of teeth were affected (P ¼ 0.007; OR ¼ 1.8; 95% CI ¼ 1.2–2.8). Type 2 diabetes mellitus is significantly associated with an increased prevalence of AP.Sin financiación1.606 JCR (2005) Q2, 21/49 Dentistry, oral surgery & medicineUE

High prevalence of apical periodontitis amongst smokers in a sample of Spanish adults

Our aim was to study the prevalence of apical periodontitis in smoker and nonsmoker patients. In a cross-sectional study, the records of 180 subjects, 109 smokers and 71 nonsmokers, were examined. All participants underwent a fullmouth radiographic survey incorporating 14 periapical radiographs. The periapical region of all teeth, excluding third molars, was examined. Periapical status was assessed using the Periapical Index score. Statistical analyses were conducted using the Cohen’s Kappa test, analysis of variance and logistic regression. Apical periodontitis in at least one tooth was found in 74% of smokers and in 41% of nonsmokers (P < 0.01; odds ratio ¼ 4.2; 95% C. I. ¼ 2.2–7.9). Amongst smoker patients 5% of the teeth had apical periodontitis, whereas in nonsmoker subjects 3% of teeth were affected (P ¼ 0.008; odds ratio ¼ 1.5; 95% C. I. ¼ 1.1–2.1). The percentage of root filled teeth in smoker and nonsmoker patients was 2.5% and 1.5%, respectively (P < 0.05; odds ratio ¼ 1.7; C. I. 95% ¼ 1.0–2.6). In conclusion, in this study population, smoking was significantly associated with a greater frequency of root canal treatment and with an increased prevalence of apical periodontitis.Sin financiación2.465 JCR (2008) Q1, 8/55 Dentistry, oral surgery & medicineUE