Flocculation behaviour of hematite-kaolinite suspensions in presence of extracellular bacterial proteins and polysaccharides.

Cells of Bacillus subtilis exhibited higher affinity towards hematite than to kaolinite. Bacterial cells were grown and adapted in the presence of hematite and kaolinite. Higher amounts of mineral-specific proteinaceous compounds were secreted in the presence of kaolinite while hematite-grown cells produced higher amounts of exopolysaccharides. Extracellular proteins (EP) exhibited higher adsorption density on kaolinite which was rendered more hydrophobic. Hematite surfaces were rendered more hydrophilic due to increased adsorption of extracellular polysaccharides (ECP). Significant surface chemical changes were produced due to interaction between minerals and extracellular proteins and polysaccharides. Iron oxides such as hematite could be effectively removed from kaolinite clays using selective bioflocculation of hematite after interaction with EP and ECP extracted from mineral-grown cells.

Comparative evaluation of the surface tension and the pH of calcium hydroxide mixed with five different vehicles: an in vitro study.

AIM: The aim of this study was to evaluate the surface tension and pH of five different vehicles that are used as potential agents to mix calcium hydroxide in root canal treatments and to compare them with the final surface tension and pH of calcium hydroxide mixed with these vehicles. MATERIALS AND METHODS: The study was carried out in two phases. In Phase I, the surface tension and pH of five vehicles (distilled water, saline, anesthetic solution, chlorhexidine, and glycerin) were evaluated using a Du Nuoy Tensiometer and a pH Meter. In Phase II, a predetermined amount of calcium hydroxide was mixed with the individual vehicles and the surface tension and pH was determined. In each group, seven samples were evaluated. RESULTS: Among the individual vehicles, chlorhexidine had the least surface tension values (39.8+1.1 dynes/cm). Among the various calcium hydroxide mixtures, calcium hydroxide with chlorhexidine showed the least surface tension values (36.4+1.1 dynes/cm). All the vehicles showed an acidic pH ranging from 5 to 6.5. There was a significant increase in the pH values with the addition of calcium hydroxide to the respective vehicles. The calcium hydroxide mixtures had an alkaline pH ranging from 9 to 11.5; the highest pH was observed for calcium hydroxide mixed with distilled water and saline (11.5+0.2). CONCLUSION: The surface tension and pH of the vehicles directly influenced the surface tension and pH of the calcium hydroxide mixtures. Chlorhexidine was found to be a better vehicle for calcium hydroxide when used as an intracanal medicament.

Canal complexity of a mandibular first molar.

The endodontic treatment of a mandibular molar with aberrant canal configuration can be diagnostically and technically challenging. This case report presents the treatment of a mandibular first molar with five root canals, of which three were located in the mesial root. A third canal was found between the mesiobuccal and mesiolingual root canals. The morphological pattern of separate apical terminations of three mesial root canals with separate orifices, as manifested in this case, is a rare one.

Tobacco use among school children in Chennai city, India.

AIMS: The present study was done to build a database on prevalence of tobacco use among students of grade 8 to 10 in Chennai city, for the purpose of advocacy of tobacco control and planning tobacco control interventions and evaluation. MATERIALS AND METHODS: A two-stage stratified probability sample of students in grades 8-10 corresponding to 13 to 15 years of age were selected from private/government aided private schools and purely government aided corporation schools. Data was collected by a pretested, closed-ended self-administered questionnaire. RESULTS: A total of 1255 students participated in this survey. Among them 64.4 boys and 35.6% were girls. Ever tobacco use was reported by 37.6% of the students (41.6 males and 30.2% females). Current users of tobacco (any products) were reported by 41.1% of the students. Prevalence was more among boy students (46.3%) when compared to that of girl students (31.6%). There existed no significant difference between current users of tobacco based on the zones of the school. Tobacco users prevalence was found more in corporation schools when compared to that of private schools. Parental and friends tobacco use was reported more often by tobacco users compared to never users. Purchasing tobacco products in a store was reported by 82.5% and almost no one was refused because of age. Almost everyone reported watching a lot of cigarette advertisements on TV, whereas about half reported watching advertisements on other medias like outdoor hoardings (45.7%), newspapers (65.3%) and social events (67.4%). CONCLUSION: This study demonstrates that among the 13 to 15-year old school going children (corresponding to grades 8 to 10) in Chennai city, the current tobacco use is high.