Bacteriologic investigation of the effects of sodium hypochlorite and chlorhexidine during the endodontic treatment of teeth with apical periodontitis

SIQUEIRA JR. et al. Bacteriologic investigation of the effects of sodium hypochlorite and chlorhexidine during the endodontic treatment of teeth with apical periodontitis. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod., v. 104, n. 1, p. 122-130, 2007.Objective. This clinical study was undertaken to compare the effectiveness of 2.5% sodium hypochlorite (NaOCl) and 0.12% chlorhexidine digluconate as irrigants in reducing the cultivable bacterial populations in infected root canals of teeth with apical periodontitis. Study design. According to stringent inclusion/exclusion criteria, 32 teeth with primary intraradicular infections and chronic apical periodontitis were selected and followed in the study. Bacterial samples were taken at the baseline (S1) and after chemomechanical preparation using either NaOCl (n 16) or chlorhexidine (n 16) as irrigants (S2). Cultivable bacteria recovered from infected root canals at the 2 stages were counted. Isolates from S2 samples were identified by means of 16S rRNA gene sequencing analysis. Results. At S1, all canals were positive for bacteria, and the median number of bacteria per canal was 7.32 105 for the NaOCl group and 8.5 105 for the chlorhexidine group. At S2, the median number of bacteria in canals irrigated with NaOCl and chlorhexidine was 2.35 103 and 2 102, respectively. Six of 16 (37.5%) canals from the NaOCl group and 8 of 16 (50%) canals from the chlorhexidine group yielded negative cultures. Chemomechanical preparation using either solution substantially reduced the number of cultivable bacteria in the canals. No significant difference was observed between the NaOCl and chlorhexidine groups with regard to the number of cases yielding negative cultures (P .72) or quantitative bacterial reduction (P .609). The groups irrigated with NaOCl or chlorhexidine showed a mean number of 1.3 and 1.9 cultivable species per canal, respectively. The great majority of isolates in S2 were from gram-positive bacteria, with streptococci as the most prevalent taxa. Conclusions. The present findings revealed no significant difference when comparing the antibacterial effects of 2.5% NaOCl and 0.12% chlorhexidine used as irrigants during the treatment of infected canal

Mejoremos los procesos de enseñanza-aprendizaje mediante la investigación-acción

Se ha realizado una investigación-acción para mejorar la práctica educativa mediante el análisis de los procesos de enseñanza-aprendizaje de las escuelas La Bressola, tomando como muestra alumnos de diferentes ciclos. Para poder llevar a cabo la investigación, hemos analizado la filiación de ciento cincuenta secuencias de treinta segundos cada una, extraídas de actividades consideradas exitosas por los docentes. A partir del análisis de éstas se han podido extraer puntos comunes que también pueden ser de utilidad por otras escuelas y/o centros educativos. Podemos destacar como puntos comunes la realización de rutinas previas a la actividad para que los niños interaccionen entre ellos y estén predispuestos a realizarla; el trabajo autónomo haciendo que los niños sean los protagonistas de sus aprendizajes; la experimentación y actividades manipulativas para favorecer un aprendizaje vivencial; la organización del espacio del aula para favorecer el intercambio entre los alumnos y con la maestra; la organización vertical de los alumnos para que grandes y pequeños aprendan mutuamente; la relación de las actividades con la realidad a través de unos aprendizajes funcionales y significativos; la verbalización posterior a la actividad para compartir impresiones; el trabajo en pequeño grupo para fomentar la cooperación; la autoevaluación que hacen los alumnos para incentivar la reflexión y la autocrítica y por último, la realización de asambleas para conseguir la participación de los alumnos y llegar a decisiones conjuntas. Con esta investigación se pretende contribuir a la formación permanente de los/las maestras, así como intercambiar recursos y estrategias utilizadas por los docentes de las diferentes escuelas

A New Method to Extract Dental Pulp DNA: Application to Universal Detection of Bacteria

BACKGROUND: Dental pulp is used for PCR-based detection of DNA derived from host and bacteremic microorganims. Current protocols require odontology expertise for proper recovery of the dental pulp. Dental pulp specimen exposed to laboratory environment yields contaminants detected using universal 16S rDNA-based detection of bacteria. METHODOLOGY/PRINCIPAL FINDINGS: We developed a new protocol by encasing decontaminated tooth into sterile resin, extracting DNA into the dental pulp chamber itself and decontaminating PCR reagents by filtration and double restriction enzyme digestion. Application to 16S rDNA-based detection of bacteria in 144 teeth collected in 86 healthy people yielded a unique sequence in only 14 teeth (9.7%) from 12 individuals (14%). Each individual yielded a unique 16S rDNA sequence in 1-2 teeth per individual. Negative controls remained negative. Bacterial identifications were all confirmed by amplification and sequencing of specific rpoB sequence. CONCLUSIONS/SIGNIFICANCE: The new protocol prevented laboratory contamination of the dental pulp. It allowed the detection of bacteria responsible for dental pulp colonization from blood and periodontal tissue. Only 10% such samples contained 16S rDNA. It provides a new tool for the retrospective diagnostic of bacteremia by allowing the universal detection of bacterial DNA in animal and human, contemporary or ancient tooth. It could be further applied to identification of host DNA in forensic medicine and anthropology

Community Analysis of Chronic Wound Bacteria Using 16S rRNA Gene-Based Pyrosequencing: Impact of Diabetes and Antibiotics on Chronic Wound Microbiota

Background: Bacterial colonization is hypothesized to play a pathogenic role in the non-healing state of chronic wounds. We characterized wound bacteria from a cohort of chronic wound patients using a 16S rRNA gene-based pyrosequencing approach and assessed the impact of diabetes and antibiotics on chronic wound microbiota. Methodology/Principal Findings: We prospectively enrolled 24 patients at a referral wound center in Baltimore, MD; sampled patients' wounds by curette; cultured samples under aerobic and anaerobic conditions; and pyrosequenced the 16S rRNA V3 hypervariable region. The 16S rRNA gene-based analyses revealed an average of 10 different bacterial families in wounds-approximately 4 times more than estimated by culture-based analyses. Fastidious anaerobic bacteria belonging to the Clostridiales family XI were among the most prevalent bacteria identified exclusively by 16S rRNA gene-based analyses. Community-scale analyses showed that wound microbiota from antibiotic treated patients were significantly different from untreated patients (p = 0.007) and were characterized by increased Pseudomonadaceae abundance. These analyses also revealed that antibiotic use was associated with decreased Streptococcaceae among diabetics and that Streptococcaceae was more abundant among diabetics as compared to non-diabetics. Conclusions/Significance: The 16S rRNA gene-based analyses revealed complex bacterial communities including anaerobic bacteria that may play causative roles in the non-healing state of some chronic wounds. Our data suggest that antimicrobial therapy alters community structure-reducing some bacteria while selecting for others

Polymorphism of the aryl-hydrocarbon receptor gene in intron 10 of human cancers

Polychlorinated dibenzo-p-dioxins (PCDDs) and related halogenated aromatic hydrocarbons (e.g., PCDFs), often called "dioxins", are ubiquitously present environmental contaminants. Some of them, notably 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are among the most toxic synthetic compounds known. The biological effects of dioxins are mediated via the aryl hydrocarbon receptor (AhR). Mutations in the AhR transactivation domain are linked to sensitivity to the acute lethality of TCDD. We present here a study of AhR gene polymorphism in normal and cancer human tissues affecting pre-mRNA splicing in the AhR gene-coding transactivation domain region (exon 10, intron 10, exon 11 region), previously shown to be associated with AhR dysfunction. We tested 126 pairs of normal and cancer tissue samples from liver, lung, stomach, kidney, mucous, breast, and pancreas of 49 males and 77 females (45-70 years of age). We used in vitro splicing assay, RT-PCR and sequencing methods. Our results showed that in an in vitro system it is possible to reconstitute cellular pre-mRNA splicing events. Tested cancer tissues did not contain mutations in the AhR transactivation domain region when the DNA sequences were compared with those from normal tissues. There were also no differences in AhR mRNA splice variants between normal and malignant breast tissues and no polymorphisms in the studied regions or cDNA

Modification of silver surface with palladium and chlorine. The effect on the state of adsorbed oxygen and its interaction with hydrogen

Thermodesorption and hydrogen titration were used to study the effect of additives (palladium and chlorine) to a silver surface on the state of sorbed oxygen. Palladium(O) is distributed throughout the 8-nm subsurface layer, while Cl- mainly accumulates on the silver surface (X-ray photoelectron data). The dissociation of the primary Pd clusters and the uniform distribution of the palladium over the Ag surface are followed by the formation of a new mobile form O(2)I, which is more firmly bound to the silver surface and is most reactive toward hydrogen. The modifiers substantially increase the amount of form OI, preventing the formation of OII from absorbed oxygen at surface centers. The effect of Pd0 and Cl- on the state of adsorbed oxygen was explained by an increase in the electron density of the silver surface in the vicinity of Pd0 atoms and Cl- ions and by complexation between oxygen and palladium adatoms