Impact of socioeconomic inequalities on dental caries in deprived children: a multilevel analysis.

OBJECTIVES: Inequalities have been reported between high, middle and low socioeconomic position (SEP) children. However, the effect of contextual and individual SEP on existing inequalities among socioeconomically deprived children varies between local contexts. The aim of this study was to assess the impact of contextual and individual SEP on individual caries experience among socioeconomically deprived children in Chile. METHODS: Cross-sectional multilevel analysis of data from the 2015 electronic register of the National Board of School Aid and Scholarships (JUNAEB) of Chile. The contextual variables were the municipality Human Development Index (HDI) and rurality index. Individual variables included gender, living in extreme poverty and school grade. Multilevel negative binomial models assessed their impact on DMFT/dmft. RESULTS: 112,429 children in 255 municipalities were included. Overall, contextual SEP (HDI) was not associated with caries experience in the primary or permanent dentition. Individual SEP (living in extreme poverty) was associated with caries experience in both dentitions. The proportion of children living in extreme poverty with caries experience in the primary teeth was 17% higher than children not living in extreme poverty (PR 1.17; 95% CI 1.15-1.19), while for children with permanent teeth it was 9% higher (PR 1.09; 95% CI 1.08-1.11). CONCLUSION: These findings could support the development of health strategies focused on individual SEP to efficiently reduce oral health inequalities among socioeconomically deprived children.

Evaluation of substantivity of hypochlorous acid as an antiplaque agent: A randomized controlled trial.

BACKGROUND: Hypochlorous acid (HOCl) is a non-antibiotic antimicrobial substance with significant effects on pathogenic oral micro-organisms. The effects of HOCl as an antiplaque agent have not been studied. OBJECTIVE: The aim of this study was to evaluate the substantivity of HOCl mouthwashes compared with chlorhexidine (CHX) rinses and a placebo. MATERIALS AND METHODS: A double-blind randomized controlled trial with 75 participants was conducted. Participants were divided into five groups using block randomization: 0.025% HOCl, 0.05% HOCl, 0.12% CHX, 0.2% CHX, and sterile water as a placebo. Participants were instructed to use each rinse solution for 30 seconds after dental prophylaxis. Samples of saliva were taken at baseline and after 30 seconds, 1, 3, 5 and 7 hours to assess substantivity, and bacterial viability was established by the fluorescence method. Visible plaque in all participants was assessed with the Turesky index at baseline and at 7 hours, and adverse events were also assessed. RESULTS: HOCl led to a 33% reduction in bacterial counts in the saliva after 30 seconds compared with a 58% reduction by CHX. HOCl has no substantivity, and bacterial counts returned to baseline after 1 hour. Placebo treatment led to the highest plaque count after 7 hours compared with the CHX and HOCl groups, although the differences were not significant. HOCl rinsing induced the highest percentages of unpleasant taste and dryness sensations. CONCLUSIONS: HOCl rinses have an initial effect on bacterial viability in saliva but have no substantivity. Other mechanisms may explain its antiplaque effect.

Validity and reliability of the T-Scan(®) III for measuring force under laboratory conditions.

Although measuring bite force is an important indicator of the health of the masticatory system, few commercially available transducers have been validated for routine clinical use. T-Scan(®) III Occlusal Analysis System allows to record the bite force distribution, indicating its relative intensity and occlusal timing. Nevertheless, even fewer studies have evaluated the validity and reliability of the latest generation of the T-Scan(®) occlusal analysis system. To determine the validity and reliability of the T-Scan(®) III system when measuring total absolute bite force under laboratory conditions. Known forces were applied to 18 T-Scan(®) III sensors, which were classified into two groups differentiated by their production series. Both Lin's concordance correlation coefficient (CCC) and the intra-class correlation coefficient (ICC) were used to assess the system's reliability and validity. Considering all the sensors studied, a substantial level (Lin's CCC 0·969) and a very good level of reliability (CCI 0·994) were obtained. When evaluating the validity of the system, a poor (Lin's CCC 0·530) and moderate (ICC 0·693) agreement were also obtained. The main factor that negatively influenced the validity of the T-Scan(®) III under these study conditions was the significant difference in the behaviour of the two sensor groups. The T-Scan(®) III showed a high degree of reliability when used to perform consecutive measurements. However, the system showed an insufficient degree of validity for measuring absolute force when estimating total occlusal force under laboratory conditions.

Long-term evaluation and clinical outcomes of children with dental transplants in Temuco city, Chile.

AIM: To assess the clinical and radiographic outcomes of 36 transplanted teeth and the possible factors affecting the results. MATERIALS AND METHODS: In 26 children, 36 teeth transplants were performed. The main reason for transplantations was the loss of anterior teeth due to trauma; 80.5% of transplanted teeth were immature bicuspids. The transplants were clinically and radiolographycally monitored in respect of pulp vitality, root canal obliteration, periradicular changes and root formation. Fisher Exact Test and Kaplan-Meier analyses were performed to determine the association between the variables and estimation of survival rates, respectively. RESULTS: Thirty (83.3%) of the transplantations were recorded as successful and six as unsuccessful (16.7%). The survival rate was 97.2% during average time of 47.5 months ± 27.8 SD. Only one tooth had been extracted and 5 had survived in not ideal conditions. The majority of immature transplanted teeth developed pulp canal obliteration. CONCLUSION: Factors associated to successful outcome were immature root formation of donor tooth and short flexible splinting period. The main factor associated to failure was replacement resorption. The surgical technique did not present statistical significance in the clinical outcome. Tooth transplantation has shown high success and survival rates, and should be considered as a real option in growing patients.

BTX abatement using Chilean natural zeolite: the role of Brønsted acid sites.

In wastewater treatment facilities, air quality is not only affected by conventional unpleasant odour compounds; toxic volatile organic compounds (VOCs) are also found. In this study, the adsorptive capacity of Chilean natural zeolite toward VOC removal was evaluated. Moreover, the influence of zeolite chemical surface properties on VOC elimination was also investigated. Three modified zeolite samples were prepared from a natural Chilean zeolite (53% clinoptilolite, 40% mordenite and 7% quartz). Natural and modified zeolite samples were characterised by nitrogen adsorption at 77 K, elemental analyses and X-ray fluorescence (XRF). Chemical modifications of natural zeolite showed the important role of Brønsted acid sites on the abatement of VOCs. The presence of humidity has a negative effect on zeolite adsorption capacity. Natural zeolites could be an interesting option for benzene, toluene and xylene vapour emission abatement.

Methylene blue removal from contaminated waters using heterogeneous catalytic ozonation promoted by natural zeolite: mechanism and kinetic approach.

This paper presents experimental results of a methylene blue removal system based on heterogeneous catalytic ozonation in the presence of natural zeolite. The effect of pH (2-10) and the presence of radical scavengers (acetate ions) on homogeneous and heterogeneous ozonation systems are assessed at laboratory scale. Results show that heterogeneous catalytic ozonation using natural zeolite increases methylene blue removal rate with respect to the single ozonation process at all pH values. The inhibitory effect of free-radical scavengers is impaired by zeolite, suggesting that methylene blue oxidation reactions take place mainly on the zeolite surface. The increase in methylene blue removal rate could be related to ozone interaction with hydroxyl groups present on the zeolite surface (S--OH2(+), S--OH, S--O(-)), which plays a key role in the reaction mechanism.

[Cutaneous mucormycosis in an immunocompromised patient]. / Mucormicosis cutánea en un paciente inmunocomprometido.

Mucormycosis is an increasingly emerging life-threatening infection and is an important cause of morbidity and mortality in patients with leukemia. We present the case of a 4-year-old boy with an acute lymphoblastic leukemia complicated by severe and prolonged neutropenia during induction chemotherapy, who developed cutaneous mucormycosis of the elbow. Direct microscopy with KOH and the histopathologic observation of the skin revealed fungal hyphae without septations. The cultures were positive for Rhizopus microsporus var oligosporus. The patient was treated succefully with amphotericin B during 40 days, surgical debridement and dermoepidermic graft. Early recognition and prompt intervention with combined medical and surgical treatment may improve the outcome. The most common management strategy in survivors involves a combination of antifungal therapy with amphotericin B and surgical debridement.

Arsenic mobilization by epilithic bacterial communities associated with volcanic rocks from Camarones River, Atacama Desert, northern Chile.

The arsenic biogeochemical cycle is greatly dependent on microbial transformations that affect both the distribution and mobility of arsenic species in the environment. In this study, a microbial biofilm from volcanic rocks was characterized on the basis of its bacterial composition and ability to mobilize arsenic under circumneutral pH. Biofilm microstructure was analyzed by scanning electron microscopy (SEM)-energy-dispersive spectroscopy (EDS). Strains were isolated from biofilms and identified by 16S rDNA sequences analysis. Arsenic oxidation and reduction capacity was assayed with high-performance liquid chromatography coupled to gaseous formation performing the detection by atomic absortion in a quartz bucket (HPLC/HG/QAAS), and polymerase chain reaction was used to detect aox and ars genes. Bacterial communities associated with volcanic rocks were studied by denaturing gradient gel electrophoresis (DGGE). The SEM-EDS studies showed the presence of biofilm after 45 days of incubation. The relative closest GenBank matches of the DNA sequences, of isolated arsenic-resistant strains, showed the existence of four different genus: Burkholderia, Pseudomonas, Erwinia, and Pantoea. Four arsenite-resistant strains were isolates, and only three strains were able to oxidize >97% of the As(III) present (500 uM). All arsenate-resistant isolates were able to reduce between 69 and 86% of total As(V) (1000 uM). Analysis of 16S rDNA sequences obtained by DGGE showed the presence of four bacterial groups (∝-proteobacteria, γ-proteobacteria, Firmicutes, and Actinobacteria). Experiments demonstrate that epilithic bacterial communities play a key role in the mobilization of arsenic and metalloids speciation.

Heterogeneous catalytic ozonation of cationic dyes using volcanic sand.

This work aims to present experimental results on the treatment of methylene blue contaminated waters using heterogeneous catalytic ozonation promoted by volcanic sand. The effect of pH (2-8), and the presence of radical scavengers (acetate ions) in homogeneous and heterogeneous systems are evaluated at laboratory scale. Heterogeneous catalytic ozonation using volcanic sand increases methylene blue removal rate. In the presence of free radical scavengers, only a 37% reduction on methylene blue removal rate is observed in the heterogeneous system, as compared with 70% when homogeneous ozonation is used. The results obtained here indicate the importance of chemical surface properties on methylene blue oxidation reactions, suggesting that acid surface sites of volcanic sand play a key role on the reaction mechanism.

Root morphology of mandibular molars: a cone-beam computed tomography study.

BACKGROUND: The aim of the study was to assess the number and anatomical classification of roots and root canals of first and second mandibular molars using cone-beam computed tomography (CBCT) in a Chilean population. MATERIALS AND METHODS: This study evaluated the CBCT scans of 289 patients aged between 14 and 86 years, obtaining a sample of 1022 mandibular first and second molars. The number of roots and root canals was evaluated according to the anatomical classification proposed by Ahmed in 2016. Data were analysed using Pearson's chi-squared test and ANOVA. RESULTS: Nine hundred fifty-one (93.05%) molars had two roots, while the remaining 71 (6.95%) molars had one root. The most frequent root and root canal morphologies found were: ²MM M² D¹ (29.65%), ²MM M²â»¹ D¹ (22.3%) and ²MM M¹ D¹ (13.4%) (M - mesial, D - distal), with a total of 32 different anatomical distributions. C-shaped canals were present in 56 molars and were more frequently found in women than in men (7.1% vs. 3.88%; p = 0.024). CONCLUSIONS: The analysis of internal anatomy using CBCT revealed a highly variable distribution of root canals. The most frequent morphology found in mandibular molars in a Chilean population was two roots and three canals.

Isolation of arsenite-oxidizing bacteria from a natural biofilm associated to volcanic rocks of Atacama Desert, Chile.

Arsenic is naturally present in rocks, soil, water, and air. It is released to the environment by natural processes such as volcanic eruptions, and rock erosion. In this study, two arsenite-oxidizing strains were isolated from volcanic rocks obtained from the Camarones Valley, Atacama Desert, Chile. Strains were isolated from biofilms and identified by 16s ARNr sequences analysis. aox genes were detected by RT-PCR. The arsenic oxidation ability was assayed with silver nitrate and HPLC-HG-AAS. Four arsenite-resistant strains were isolated (8 mM). RT-PCR analysis showed the presence of aox genes in UC-2 and UC-6 strains. In addition, UC-2 and UC-6 strains were able to oxidize 90 and 95% arsenite present in the medium to arsenate, at a rate of 9.3 and 9.8 microg ml(-1) h(-1 )respectively. Bicarbonate (HCO(3) (-)) was used as unique carbon source. Finally, the significative oxidation capacity shown by both strains opens the way to further studies aimed at implementing biological systems to treat arsenic rich wastewater.

Methylene blue removal from contaminated waters using O3, natural zeolite, and O3/zeolite.

This paper compares experimental results on methylene blue (MB) removal systems based on ozone oxidation, zeolite adsorption, and simultaneous adsorption-oxidation using ozone in the presence of natural zeolite. The effect of pH (2-8), and the presence of radical scavengers (sodium acetate) on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1 L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with zeolite adsorption increases the overall MB oxidation rate with respect to ozonation process and zeolite adsorption. In presence of free radical scavenger, only a 25% of reduction on MB removal rate are observed in the simultaneous treatment, as compared with 70% when ozonation treatment is used, suggesting that MB oxidation reactions take mainly place on the zeolite surface.

Isolation of arsenite-oxidizing bacteria from arsenic-enriched sediments from Camarones river, Northern Chile.

In Northern Chile, high arsenic concentrations are found in natural water, both natural and anthropogenic sources, a significant health risk. Nine bacterial strains were isolated from Camarones river sediments, located in Northern Chile, a river showing arsenic concentrations up to 1,100 microg/L. These strains were identified as Pseudomonas and they can oxidize arsenite (As(III)) to the less mobile arsenate (As(V)). The arsenite oxidase genes were identified in eight out of nine isolates. The arsenite oxidizing ability shown by the nine strains isolated from arsenic enriched sediments open the way to their potential application in biological treatment of effluents contaminated with arsenic.

Arsenic resistant bacteria isolated from arsenic contaminated river in the Atacama Desert (Chile).

In this study, arsenic resistant bacteria were isolated from sediments of an arsenic contaminated river. Arsenic tolerance of bacteria isolated was carried out by serial dilution on agar plate. Redox abilities were investigated using KMnO4. arsC and aox genes were detected by PCR and RT-PCR, respectively. Bacterial populations were identified by RapID system. Forty nine bacterial strains were isolated, of these, 55 % corresponded to the reducing bacteria, 4% to oxidizing bacteria, 8% presented both activities and in 33% of the bacteria none activity was detected. arsC gene was detected in 11 strains and aox genes were not detected. The activity of arsenic transforming microorganisms in river sediment has significant implications for the behavior of the metalloid.

Heterogeneous catalytic ozonation of benzothiazole aqueous solution promoted by volcanic sand.

This paper presents experimental results on the catalytic effect of volcanic sand on benzothiazole ozonation. Experiments were assessed at laboratory scale, in a differential circular flow reactor composed of a volcanic sand fixed bed column of 19 cm3 and a 1 dm3 storage tank, operated in batch mode at 20 degrees C and pH 2-7. Experimental results show that ozone self-decomposition is enhanced by the presence of volcanic sand at all pH. At pH>pH(PZC), the increase in aqueous ozone decay could be related to ozone interaction with strong Lewis acid on metal oxide surface sites of the volcanic sand. Ozone self-decomposition reactions occurring on the volcanic sand are less affected by the presence of radical scavengers. Benzothiazole removal by ozonation is also enhanced by the presence of volcanic sand. Moreover, the inhibitory effect of free radical scavengers is also impaired by volcanic sand, suggesting that strong Lewis acid surface sites play a key role on the reaction mechanism.

Effect of temperature on Imidacloprid oxidation by homogeneous photo-Fenton processes.

This paper presents experimental results on the effect of temperature on the rate of Imidacloprid removal from waste water using homogeneous photo-Fenton processes. Experiments were conducted in a 2 L photo reactor set at 15-42 degrees C, initial concentrations in the range of 10 to 40 mg L(-1) Fe(II) and 100-450 mg L(-1) H(2)O(2); 30 150 min processing times. Initial H(2)O(2) concentration determined the extent of the oxidation process, whereas iron concentration played a key role in the process kinetics. Homogeneous photo-Fenton showed a fast initial reaction leading to 50% Imidacloprid degradation after less than 1 min of treatment, followed by a slower process until full removal was achieved. Rapid Fe(II) oxidation to Fe(III) seems responsible for the initial Imidacloprid removal. Imidacloprid removal fitted well a pseudo-first order kinetic scheme, with apparent activation energy of approximately 31.6 kJ/mole. Untreated Imidacloprid samples showed significant acute toxicity to Daphnia magna and genotoxic effects on Bacillus subtilis. Acute toxicity and genotoxicity remained detectable even after complete pesticide removal, showing that toxic by-products were present. The design and operation of photo Fenton processes should focus on toxicity removal rather than on specific target pollutants.

Coupling of photocatalytic and biological reactors to remove EDTA-Fe from aqueous solution.

Degradation of 2.5 mM EDTA-Fe solution was performed in a coupled photocatalytic-biological reactor. The system consists of a photochemical annular reactor filled with TiO2 immobilized on glass Raschig rings coupled with an activated sludge continuous reactor. Around 50% of EDTA degradation was reached after 150 min irradiation. Simultaneously a four-fold increase in biodegradability, measured as BOD5/COD ratio, was observed. The activated sludge is not capable to degrade the complex EDTA-Fe but it removed partially the COD and efficiently the BOD5 of the photochemically treated solution.

Effects of pulp and paper mill effluents on the microplankton and microbial self-purification capabilities of the Biobío River, Chile.

Most studies focus on the ecotoxicity of pulp and paper mill effluents, rather than on how they affect the physicochemical and biological structure and the intrinsic ecological capabilities of the receiving watercourses. We investigated the impact of such effluents on the water quality, microplankton system and microbial self-purification capacity (degradation of polymeric organic compounds via extracellular enzymes) of the Biobío River in Chile. The physicochemical impact on the water quality was indicated by raised conductivity, by the pollution of the water body with nitrate, nitrite and soluble reactive phosphorus, by the appearance of tannin and lignin, and by the steady accumulation of inorganic and organic suspended matter (SPM) along the river. From the biological structure of the microplankton system, very low and declining concentrations of chlorophyll a and heterotrophic flagellate densities were determined. The pulp and paper mill effluents introduced high bacterial abundances and biomass concentrations into the river water. This reflects the effective use made of the abundantly available inorganic and organic nutrients within this industrial and municipal process water by bacteria adapted to these extreme environments, additionally supported by concomitant low grazing pressure derivable from low heterotrophic flagellate abundances. Indeed, in one section of the river affected by a pulp mill, the plant was found to significantly contribute to the self-cleaning capacity of the river. However, this elevated degradation capacity was not enough to compensate for the additionally discharged organic material which, together with the toxic effects of the paper plant effluents, significantly interferes with the ecological status of the Biobío River.

Environmental evidence of fossil fuel pollution in Laguna Chica de San Pedro lake sediments (Central Chile).

This paper describes lake sediment spheroidal carbonaceous particle (SCP) profiles from Laguna Chica San Pedro, located in the Biobío Region, Chile (36 degrees 51' S, 73 degrees 05' W). The earliest presence of SCPs was found at 16 cm depth, corresponding to the 1915-1937 period, at the very onset of industrial activities in the study area. No SCPs were found at lower depths. SCP concentrations in Laguna Chica San Pedro lake sediments were directly related to local industrial activities. Moreover, no SCPs were found in Galletué lake (38 degrees 41' S, 71 degrees 17.5' W), a pristine high mountain water body used here as a reference site, suggesting that contribution from long distance atmospheric transport could be neglected, unlike published data from remote Northern Hemisphere lakes. These results are the first SCP sediment profiles from Chile, showing a direct relationship with fossil fuel consumption in the region. Cores were dated using the 210Pb technique.

Ozonation of benzothiazole saturated-activated carbons: influence of carbon chemical surface properties.

The combined or sequential use of ozone and activated carbon to treat toxic effluents has increased in recent years. However, little is known about the influence of carbon surface active sites on ozonation of organic adsorbed pollutants. This paper presents experimental results on the effect of metal oxides and oxygenated surface groups on gaseous ozonation of spent activated carbons. Benzothiazole (BT) was selected as a target organic compound in this study due to its environmental concern. Activated carbons with different chemical surface composition were prepared from a Filtrasorb-400 activated carbon. Pre-treatment included: ozonation, demineralisation, and deoxygenation of activated carbon. Ozonation experiments of BT saturated-activated carbons were conducted in a fixed bed reactor loaded with 2 g of carbon samples. The reactor was fed with an O2/O3 gas mixture (2 dm3/min, 5 g O3/h), for a given exposure time, in the range 10-120 min, at 298 K and 1 atm. Results show that extended gaseous ozonation of activated carbon saturated with BT led to the effective destruction of the adsorbate by oxidation reactions. Oxidation of BT adsorbed on activated carbon seemed to occur via both direct reaction with ozone molecules, and by oxygen radical species generated by catalytic ozone decomposition on metallic surface sites.