Search

Here, we assess the effects of gypsum and local organic waste as amendments to non-weathered, filter-pressed bauxite residue (BR) to improve its properties and support plant growth. In addition, we monitored the leachate quality of the amended BR under progressive leaching that simulated precipitation conditions in Northern Brazil. Free-draining column tests consisting of BR amended with gypsum and organic waste, at 5% and 10% w/w, respectively, were leached for 8 weeks to assess the effects on the chemical composition of BR and the leachates. Adding gypsum to BR reduced the exchangeable sodium (Na) percentage (ESP) from approximately 79%–48%, whereas adding only organic waste had smaller effects on ESP (from ∼79% to ∼ 70%). The mean leachate pH ranged from 8.7 to 9.4 for the gypsum, and organic waste amended BR, while this was 10.3 in the leachate of the unamended BR. The treatments had similar trends of electrical conductivity throughout the experiments and were below 2 dS/cm after 8 weeks, when ∼1.700 mm simulated precipitation had leached. Aluminium (Al), Arsenic (As), and Vanadium (V) concentrations in leachates of BR with gypsum, either alone or in combination with organic waste, were significantly lowered than in leachate of non-amended BR. By contrast, metal concentrations increased if organic waste was added to BR. We conclude that amending BR with gypsum, in combination with organic waste, significantly improves the chemical properties of the solid phase and achieved rehabilitation goals for SAR and EC of the leachates after 8 weeks of leaching. However, despite high leaching rates, rehabilitation goals for pH and ESP were not achieved with gypsum either alone or combined with organic waste. [Display omitted] • Bauxite residue has physicochemical properties which are not suitable for plant growth. • Different remediation strategies were assessed in leaching column experiments. • Gypsum and organic waste promoted suitable physicochemical conditions for plant growth. • Al, As and V concentrations decreased substantially due to gypsum amendment. • Rehabilitation goals were hardly achieved in non-weathered bauxite residue. [ABSTRACT FROM AUTHOR]

Background Failed restorations in primary teeth are not always re-restored. Is re-restoration not required anymore? Objective To compare survival rates of primary molars with intact and defective amalgam and ART restorations. Methods A total of 649 restored primary molars, of which 162 were assessed with defective restorations for mechanical reasons, from a cluster-randomised controlled clinical trial, were followed up over a period of 3.5 years. Restored primary molars, extracted because of dental sepsis or toothache, were considered a failure. Primary molars with defective restorations were followed up from the time they were assessed defective. Data were analysed using PHREG model with frailty correction, Wald test, t-test, and jackknife procedure. Results The survival rate of primary molars with intact restorations (96.3%) was statistically significantly higher than that of primary molars with defective restorations (75.9%) over a 3-year period ( P < 0.0001). Neither the effect of treatment protocol (amalgam or ART) ( P = 0.05) nor the type of surface (single or multiple) ( P = 0.73) was observed with respect to the survival rate of restored primary molars. Conclusions Survival rates for primary molars with intact and defective amalgam and ART restorations were high. The 3-year survival rate of primary molars with intact restorations was significantly higher than that of primary molars with defective restorations. [ABSTRACT FROM AUTHOR]

Objective The aim of the study was to evaluate the exfoliation pattern of primary molars treated according to three treatment protocols. The hypothesis tested was that there is no difference in the exfoliation pattern of primary molars treated according to conventional restorative treatment using amalgam ( CRT), atraumatic restorative treatment using high-viscosity glass-ionomer ( ART), and ultraconservative treatment ( UCT). The latter consisted of restoring small cavities with ART and cleaning medium/large nonrestored cavities daily with toothpaste/toothbrush under supervision. Methods A sample of 302 children aged 6-7 years from a suburban area of Brasilia was followed up for 3.5 years. The numbers of treated molars were 341 ( CRT), 244 ( ART), and 275 ( UCT). Exfoliation rates were obtained using the PHREG procedure. Differences between the three treatment protocol groups were tested using the Wald test. Results After 3.5 years, there was no difference over the exfoliation rates of all primary molars as 51.0% ( CRT), 48.7% ( ART), and 48.1% ( UCT) had exfoliated at the overall period ( P = 0.37). Teeth with multiple-surfaces treatment had exfoliated in a higher proportion than teeth with single-surface treatments for all the three treatment groups ( P = 0.04). Conclusion The three treatment protocols led to similar exfoliation patterns of all primary molars after 3.5 years. [ABSTRACT FROM AUTHOR]

The aim of the present study was to assess the caries experience of children aged 6 to 7 years old in a socially deprived suburban area of Brazil's Federal District, using the ICDAS II system and to investigate determinants of dental caries. The survey was carried out in six public schools by three calibrated examiners, on a sample of 835 children. ICDAS II codes had to be converted into dmf/DMF components at surface and tooth levels, resulting in unfamiliar caries variables, to enable some meaningful reporting of the findings. The prevalence of dental caries, including enamel and dentinal carious lesions, in primary teeth was 95.6% and in permanent teeth it was 63.7%. Mean values of dmf-t (enamel and dentinal lesions), dmf-t (dentine lesions), DMF-T and DMF-T indices were 6.9 ± 3.8, 3.2 ± 3.4, 1.7 ± 1.6 and 0.2 ± 0.5, respectively. Enamel carious lesions predominated in the dmf-t/s and DMF-T/S indices. Seven-year-old children had statistically significantly more enamel and dentine carious lesions in permanent teeth than 6-year-old children had. Using ICDAS II, the prevalence of dental caries in both dentitions was very high. In both dentitions, the decay component predominated, with hardly any restorations or extractions observed. The new ICDAS II system leads to overvaluation of the seriousness of dental caries experience and made reporting of outcomes cumbersome. Guidelines on analysing data and reporting results should be agreed upon before this system can be used in epidemiological surveys globally. [ABSTRACT FROM AUTHOR]

The aim of the present study was to assess the caries experience of children aged 6 to 7 years old in a socially deprived suburban area of Brazil's Federal District, using the ICDAS II system and to investigate determinants of dental caries. The survey was carried out in six public schools by three calibrated examiners, on a sample of 835 children. ICDAS II codes had to be converted into dmf/DMF components at surface and tooth levels, resulting in unfamiliar caries variables, to enable some meaningful reporting of the findings. The prevalence of dental caries, including enamel and dentinal carious lesions, in primary teeth was 95.6% and in permanent teeth it was 63.7%. Mean values of d(2)mf(2)-t (enamel and dentinal lesions), d(3)mf(3)-t (dentine lesions), D(2)MF(2)-T and D(3)MF(3)-T indices were 6.9 ± 3.8, 3.2 ± 3.4, 1.7 ± 1.6 and 0.2 ± 0.5, respectively. Enamel carious lesions predominated in the dmf-t/s and DMF-T/S indices. Seven-year-old children had statistically significantly more enamel and dentine carious lesions in permanent teeth than 6-year-old children had. Using ICDAS II, the prevalence of dental caries in both dentitions was very high. In both dentitions, the decay component predominated, with hardly any restorations or extractions observed. The new ICDAS II system leads to overvaluation of the seriousness of dental caries experience and made reporting of outcomes cumbersome. Guidelines on analysing data and reporting results should be agreed upon before this system can be used in epidemiological surveys globally.