Toxicity assessment of binary mixtures of BP3 with 4-MBC (UV-filters), and BP3 with DEET (insect repellent) using the aquatic midge Chironomus riparius.

Personal care products have various organic ultraviolet filters (UV filters) in their composition to increase protection against ultraviolet radiation. Some of these products also contain insect repellents in their formulations. Consequently, these compounds reach freshwater ecosystems, exposing aquatic organisms to a cocktail of anthropogenic contaminants. In this study, the joint effects of two most frequently detected UV filters (Benzophenone - 3 (BP3) and Enzacamene (4-MBC)) and joint effects of BP3 combined with an insect repellent (N, N diethyl-3-methylbenzamide - DEET) were evaluated using life-history traits of the aquatic midge Chironomus riparius such as emergence rate, time to emergence and imagoes body weight. The results showed synergistic effects between BP3 and 4-MBC for C. riparius emergence rate. Regarding the effects of BP3 and DEET mixture, our analysis suggests synergism in the case of males but antagonism in the case of females' time to emergence. Our results imply that the effects of UV filters present in sediments within chemical mixtures are complex and that the evaluation of effects using different life-history traits can yield different patterns of responses. This study demonstrates the importance of assessing the combined effects of pollutants used/found concomitantly in aquatic systems for a more accurate risk assessment, as individual chemical testing can underestimate the toxicity of organic UV filters.

Combined effects of polyethylene microplastics and natural stressors on Chironomus riparius life-history traits.

Several studies have shown that ingestion of microplastics causes adverse effects in aquatic organisms, including sediment-dwelling invertebrates. Most studies focus on evaluating the effects of plastic particles alone without testing the mediating effects of different natural stressors and thus lacking realistic exposure scenarios. The present study addresses the interactive effects of exposure to polyethylene microplastics (PE-MPs; 2.5 g/kg) in the midge Chironomus riparius life history traits under different temperatures (15, 20 and 25 °C), a salinity gradient (0, 1 and 3 g L-1 sodium chloride - NaCl) and different levels of food (0.5, 0.25 and 0.125 mg macerated fish food larva-1day-1). By the analyses of linear models and independent action models applied to different life-history traits, such as larval growth, development time and imagoes body weight, the present work reveals that under temperatures lower than 20 °C or severe food shortage (<0.25 mg macerated fish food larva-1day-1), microplastics' effects can be stronger than those observed at standard toxicity test conditions (20 °C and 0.5 mg food larva-1day-1). Additionally, we also found that, in general, toxicity induced by PE-MPs to C. riparius larvae was reduced under warmer temperature (25 °C) and salinity. As observed, MPs toxicity can be mediated by natural stressors, which underlines the importance of co-exposure studies. In this sense, these results contribute to a more accurate risk assessment of microplastics. Despite the complex interactions between microplastics and natural factors here tested, were not found evidence that the deleterious effects of PE-MPs on C. riparius life cycle history are aggravated under increased temperature, food shortage, or salinisation of freshwaters.

Differential accumulation of PAHs within planarian cephalic and posterior body parts.

It has been observed that freshwater planarians can accumulate cadmium in their head portions, with neurotoxicity and head loss accompanying this phenomenon. Since planarians exhibit head loss and symptoms of neurotoxicity in response to PAHs, we investigated the differential accumulation of pyrene and B[a]P in the body and head portions of Girardia tigrina, a freshwater planarian. It is evidenced that planarian head fragments present higher amounts of pyrene- and B[a]P-equivalents than body fragments, indicating a differential distribution of these compounds within planarian tissues.

Responses of benthic macroinvertebrate communities to a Bti-based insecticide in artificial microcosm streams.

Bioinsecticides based on the bacterium Bacillus thuringiensis subsp. israelensis (Bti) are increasingly being applied directly into aquatic compartments to control nuisance mosquitoes and blackflies and are generally considered environmentally friendly alternatives to synthetic insecticides. Bti-based insecticides are considered highly selective, being Diptera-specific, and supposedly decompose rapidly in the environment. Nevertheless, their safety to non-target species and freshwater ecosystems has been questioned by recent studies, which in fact document possible indirect effects in aquatic food webs such as the decrease of prey availability to predators. This work aimed to evaluate the potential effects of a Bti-based insecticide (VectoBac® 12AS) on a freshwater macroinvertebrate community and on stream ecological functions by using artificial microcosm streams. Artificial microcosm streams were colonized with a macroinvertebrate community plus periphyton collected in a stream together with Alnus glutinosa leaf packs. They were exposed for 7 days to different Bti treatments (0, 12, 120, 1200 µg/L), which are within the recommended concentrations of application in aquatic compartments for blackfly and mosquito control. Besides invertebrate community structure and abundance, effects were evaluated regarding leaf decomposition and primary production as measures of ecosystem functioning. Community structure was significantly altered in all Bti treatments after 7 days of exposure, mostly due to a decline in chironomids, followed by oligochaetes, which both belong to the deposit-feeders' functional group. Direct effects on oligochaetes are surprising and require further research. Also, reductions of leaf decomposition due to Bti-induced sublethal effects on shredders (reduced feeding) or mortality of chironomids (that can also feed on coarse organic matter) observed in our study, represent potential indirect effects of Bti in aquatic ecosystems. Our short-exposure experiment evidenced some negative effects on stream benthic invertebrate communities and on ecosystem functioning that must be considered whenever Bti is used in water bodies for blackfly or mosquito control programs.

Oxidative damage and decreased aerobic energy production due to ingestion of polyethylene microplastics by Chironomus riparius (Diptera) larvae.

Riverine sediments are major sinks of microplastics from inland anthropogenic activities, imposing a threat to freshwater benthic invertebrates. This study investigated the ingestion of three size-classes (SC) of irregularly shaped polyethylene microplastics (PE-MPs; SC I: 32-63 µm; II: 63-250 µm; III: 125-500 µm) after 48 h by dipteran larvae (detritivore/collector) Chironomus riparius, and the consequent effects on neurotransmission, energy allocation and oxidative stress. The tested PE-MPs concentrations (1.25; 5; 20 g kg-1) were within the range of concentrations reported in riverbanks from highly urbanised areas (1 - 9 g kg-1), except for 20 g kg-1 representing the worst-case scenario. After exposure to SC I, larvae presented high amounts (up to ∼2400 particles/organism) of PE-MPs in their guts, with an average size-range of 30-60 µm. In the SC II and III, larvae presented PE-MPs of higher diameter (up to 125 µm) and a visible gut obstruction. The high number of particles in the larval gut (SC I) and/or difficulties for their egestion (SC I, II and III) induced oxidative damage and reduced aerobic energy production. In addition, larvae exposed to SC II and III revealed depletion in their total lipid reserves as a consequence of lacking nutrients, and the ones exposed to SC III presented a decrease in their detoxification capacity. These results highlight that freshwater detritivores with low selective feeding behaviour (e.g., chironomids) are more prone to ingest microplastics, with potentially adverse effects on cellular metabolism, redox status and antioxidant-detoxification defences. These harmful effects at lower levels of the biological organisation may ultimately affect organisms' physiology and fitness.

Effects of the organic UV-filter, 3-(4-methylbenzylidene) camphor, on benthic invertebrates and ecosystem function in artificial streams.

In the last decades, the use of organic ultraviolet-filters (UV-filters) has increased worldwide, and these compounds are now considered emerging contaminants of many freshwater ecosystems. The present study aimed to assess the effects of 3-(4-methylbenzylidene) camphor (4-MBC) on a freshwater invertebrate community and on associated ecological functions. For that, artificial streams were used, and a natural invertebrate benthic community was exposed to sediments contaminated with two concentrations of 4-MBC. Effects were evaluated regarding macroinvertebrate abundance and community structure, as well as leaf decomposition and primary production. Results showed that the macroinvertebrate community parameters and leaf decomposition rates were not affected by 4-MBC exposure. On the other hand, primary production was strongly reduced. This study highlights the importance of higher tier ecotoxicity experiments for the assessment of the effects of low concentrations of organic UV-filters on freshwater invertebrate community structure and ecosystem functioning.

Lipid Nanoparticles as Carriers for the Treatment of Neurodegeneration Associated with Alzheimer's Disease and Glaucoma: Present and Future Challenges.

Glaucoma constitutes the second cause of blindness worldwide and it is considered a neurodegenerative disorder. In this sense, Alzheimer's disease, which is the most common type of dementia, also causes neurodegeneration. The association between both diseases remains unknown although it has been hypothesised that a possible connection might exist and it will be analysed throughout the review. In this sense, nanoparticulate systems and specially, lipid nanoparticles could be the key for effective neuroprotection. Lipid nanoparticles are the most recent type of drug nanoparticulate systems. These nanoparticles have shown great potential to encapsulate hydrophobic drugs increasing their bioavailability and being able to deliver them to the target tissue. In addition, they have shown great potential for ocular drug delivery. This review explores the most recent strategies employing lipid nanoparticles for AD and glaucoma.

Life history and behavior effects of synthetic and natural dyes on Daphnia magna.

Azo dyes are the largest class of dyes extensively used by industries despite their mutagenic potential for humans. As such, natural dyes have been reemerging as an important alternative to human safety. However, limited studies have focused on the effect of dyes on the environment, thus their ecotoxicological investigation is imperative. Here, we aimed to evaluate toxic effects induced by the synthetic azo dye Basic Red 51 (BR51) in comparison with natural dye erythrostominone (Ery) in the microcrustacean Daphnia magna, a standard organism used to assess the risk of chemicals to aquatic organisms. The colorless product formed after the photodegradation of Ery (DEry) was also evaluated, addressing an easy and low cost alternative for industrial effluent treatments. The results showed that both dyes are acutely toxic to D. magna. BR51 and Ery reduced the intrinsic rate of D. magna population increase, which generated fewer neonates per brood. BR51 also increased daphnids respiration rates. In contrast, DEry did not alter any of the analyzed parameters. No locomotor changes were observed when daphnids were exposed to sub-lethal concentrations of Ery or BR51. These results indicate that both dyes can induce deleterious consequences for daphnids including population level effects, but the natural dye Ery presents 100-fold lower toxicity in comparison with the azo dye BR51. Also, that photodegradation of Ery is an efficient method to reduce and prevent previously observed toxic effects, suggesting an inexpensive, fast and easy alternative for treatment of effluents containing this natural dye.

Seasonal time-series reveal the impact and rapid recovery in richness, abundance and community structure of benthic macroinvertebrates following catchment wildfire.

Catchment wildfire can decimate freshwater benthos when burnt material washes through river channels. We conducted detailed seasonal surveys over the course of one-year at N = 9 sites following summer-time wildfire in 2009 and N = 3 sites following summer-time wildfire in 2010 (constituting one-year time-series of 9 ∗ 5 and 3 ∗ 5 samples, respectively). Basic one-year-on surveys were conducted at an additional 12 sites following 2009 wildfires (Sumpostfire:Sum+one.yr; N = 12 ∗ 2). Burnt sites were compared with 6 reference sites surveyed seasonally between autumn and summer, 2009-2010 (N = 6 ∗ 4), supplemented by 6 additional sites surveyed in summer 2004 (total reference samples: N = 6 ∗ 5). While benthic macroinvertebrates were largely unaffected by the fire event, richness and abundance were decimated during the winter, yet recovered to initial survey levels by the following summer. The differential response of assemblages in the exceptionally wet winter of 2009-10 versus 2010-11 highlighted the catalytic role of rainfall as a driver of benthic disturbance. Ecological disturbance was proportionally greater for less abundant taxa with community evenness peaking at the time of maximum disturbance. Seasonal dynamics in fire-impacted and reference sites followed a similar pattern, implying that despite the major reduction in macroinvertebrate standing crop the general character of benthic processes was sustained. One year after the wildfire event community structure was similar to the immediate post-fire assemblages and generally indistinguishable from reference samples. The statistical importance of habitat parameters at the landscape and local scale (catchment size, landuse, slope, bank management and benthic substrate) were indicative of mechanistic processes underlying wildfire disturbance-recovery and define the scope for mitigation management. The remarkable resilience of community structure in these Mediterranean streams marks an emphatic contrast to the response of benthic macroinvertebrates to comparable disturbance processes in temperate regions. Given the increasing geographic scale and frequency of fires accompanying global warming wildfire-risk may become a leading issue for river management.

Invasive Species Mediate Insecticide Effects on Community and Ecosystem Functioning.

Anthropogenic activities increase pesticide contamination and biological invasions in freshwater ecosystems. Understanding their combined effects on community structure and on ecosystem functioning presents challenges for an improved ecological risk assessment. This study focuses on an artificial stream mesocosms experiment testing for direct and indirect effects of insecticide (chlorantraniliprole - CAP) exposure on the structure of a benthic macroinvertebrate freshwater community and on ecosystem functioning (leaf decomposition, primary production). To understand how predator identity and resource quality alter the community responses to chemical stress, the mediating effects of an invasive predator species (crayfish Procambarus clarkii) and detritus quality (tested by using leaves of the invasive Eucalyptus globulus) on insecticide toxicity were also investigated. Low concentrations of CAP reduced the abundance of shredders and grazers, decreasing leaf decomposition and increasing primary production. Replacement of autochthonous predators and leaf litter by invasive species decreased macroinvertebrate survival, reduced leaf decomposition, and enhanced primary production. Structural equation modeling (SEM) highlighted that CAP toxicity to macroinvertebrates was mediated by the presence of crayfish or eucalypt leaf litter which are now common in many Mediterranean freshwaters. In summary, our results demonstrate that the presence of these two invasive species alters the effects of insecticide exposure on benthic freshwater communities. The approach used here also allowed for a mechanistic evaluation of indirect effects of these stressors and of their interaction on ecosystem functional endpoint, emphasizing the value of incorporating biotic stressors in ecotoxicological experiments.

Occupational risks associated with the use of pesticides in the green belt of Córdoba, Argentina / Riesgos ocupacionales asociados al uso de plaguicidas en el cinturón verde de Córdoba, Argentina

Horticulture is an activity with high occupational risk and few studies have addressed this problem in Argentina. We studied groups of horticultural workers in the Green Belt of Córdoba City (GBCC) (Argentina) and identified some determinants of occupational accidents caused by the use of pesticides. An observational study was conducted, examining demographic, productive and labor issues in 101 workers. A Multiple Correspondence Analysis (MCA) enabled distribution and covariance patterns to be visualized and typologies of individuals to be established. Logistic regression models were used to identify occupational accidents with pesticides. The MCA identified the more vulnerable groups: those using backpacks to apply pesticides, those who sprayed a great variety of pesticides, those working in small production units, and those living in their place of work. Accidents caused by the use of pesticides were associated with subjects who handle a large number of pesticides and work in small establishments. Determining factors for the occurrence of accidents were found to be higher levels of education (OR 4.23; p = 0.046), the greater number of pesticides used (OR 5.44; p=0.013) and lower PPE level (OR 4.92; p= 0.021). This characterization identifies features of vulnerability to pesticide exposure in certain groups of horticulturists as well as determinants of accidents with pesticides.

La horticultura constituye una actividad de elevado riesgo ocupacional y en Argentina son escasos los estudios que aborden esa problemática. Se identificaron grupos de trabajadores agrícolas en el cinturón hortícola de Córdoba (Argentina) y algunos condicionantes de accidentes laborales con estos productos. Se llevó a cabo un estudio observacional descriptivo mediante encuestas a 101 horticultores indagando aspectos sociodemográficos, productivos y laborales. Un Análisis Factorial de Correspondencias Múltiples (AFCM) permitió visualizar la distribución y covariación de modalidades y establecer tipologías de individuos. La identificación de los accidentes laborales con plaguicidas se llevó a cabo mediante modelos de regresión logística. El AFCM identificó grupos considerados como vulnerables y dados por sujetos que utilizan mochila para aplicar los plaguicidas, aplican una gran variedad de ellos, trabajan en pequeñas unidades de producción y viven en donde trabajan. Asimismo, los accidentes causados por el uso de plaguicidas se asociaron a sujetos que manipulan mayor número de plaguicidas y trabajan en pequeños establecimientos. Como factores condicionantes de la ocurrencia de accidentes se encontró al mayor nivel de escolaridad (OR 4,23 p=0,046), al mayor número de plaguicidas utilizados (OR 5,44; p=0,013) y al bajo nivel de protección personal (OR 4,92; p=0,021). Esta caracterización identifica atributos de vulnerabilidad frente a la exposición a plaguicidas en determinados grupos de horticultores así como también los condicionantes de accidentes laborales con plaguicidas.

Synthesis, antifungal evaluation and optical properties of silver molybdate microcrystals in different solvents: a combined experimental and theoretical study.

In this study, we investigate the structure, antifungal activity, and optical properties of ß-Ag2MoO4 using experimental and theoretical approaches. ß-Ag2MoO4 samples were prepared by a co-precipitation method using different solvents (water, ethanol and ammonia), and their antifungal activity against Candida albicans was investigated. The samples were characterized by X-ray diffraction, micro-Raman spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy with energy dispersive spectroscopy. The optical properties were investigated by UV-Vis spectroscopy and photoluminescence measurements at room temperature. The thermodynamic equilibrium shape of the ß-Ag2MoO4 crystals was determined based on the surface energies calculated using Wulff construction. The (011) orientation was the predominant surface in the morphology. The experimental morphology was obtained by varying the surface energy ratio for each facet. A large decrease in surface energy for the (111) surface provided the experimental morphology for crystals synthesized using water and ethanol as solvents; when the surface energies for both (011) and (001) surfaces increased, the crystal morphology obtained using ammonia as a solvent was reproduced. A correlation between the exposed surfaces and antifungal activity was revealed, and an explanation to this behavior that arises from different morphologies and structural data was provided. Theoretical calculations confirm the rationality of the experimental scheme and elucidate the underlying reason for the fungistatic and fungicidal activity against Candida albicans.

Effect of surface roughness on the hydrophobicity of a denture-base acrylic resin and Candida albicans colonization.

AIM: The aim of the present study was to evaluate the effect of surface roughness (roughness average [Ra] µm) on the hydrophobicity of a denture-base acrylic resin and the initial adherence and biofilm formation of Candida albicans (C. albicans). METHODS: Disk-shaped specimens were divided into six groups: Ra 0.05, Ra 0.2, Ra 0.4, Ra 0.8, Ra 1.5, and Ra 3.0. Water contact angles (WCA) were measured, and the specimens incubated with C. albicans for 90 min (initial adherence, n = 108) or 48 h (biofilm formation, n = 108). Adhered and biofilm cells were evaluated by c.f.u./mL and 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT), and the correlation between the two methods was evaluated. The surface of the specimens and cells (adhered and biofilm) were also analyzed by scanning electron microscopy (SEM). RESULTS: Groups Ra 0.05 and 3.0 exhibited the lowest (~75°) and the highest (~100°) WCA mean values, respectively. For both initial adherence and biofilm formation, no statistically-significant differences were observed among all groups, as determined by c.f.u./mL and XTT. A positive correlation between these two methods was found. SEM analysis showed the presence of scratches and valleys on the acrylic specimens and densely-packed yeast cells covering the entire surface. CONCLUSIONS: Roughness significantly increased hydrophobicity (WCA), but had no effect on the number and metabolic activity of adherent and biofilm cells of C. albicans.

Biological effects of soft denture reline materials on L929 cells in vitro.

Soft denture reline materials have been developed to help patients when their oral mucosa is damaged or affected due to ill-fitting dentures or post-implant surgery. Although reports have indicated that these materials leach monomers and other components that do affect their biocompatibility, there is little information on what cell molecules may be implicated in these material/tissue interactions. The biocompatibility of six soft liners (Ufi Gel P, Sofreliner S, Durabase Soft, Trusoft, Softone and Coe Comfort) was evaluated using a mouse fibroblast cell line, L929. Within 2 h of material disc preparation, each of the materials was exposed by direct contact to L929 cells for periods of 24 and 48 h. The effect of this interaction was assessed by alamarBlue assay (for cell survival). The expression of integrin α5ß1 and transforming growth factor ß1 was also assessed using plate assays such as enzyme-linked immunosorbent assay. Trusoft, Softone and Coe Comfort showed significantly reduced cell survival compared with the other soft lining materials at each incubation period. Furthermore, there were significant differences with these same materials in the expression of both integrin α5ß1 and transforming growth factor ß1. Soft liner materials may affect cell viability and cellular proteins that have important roles in wound healing and the preservation of cell viability and function in the presence of environmental challenges and stresses.

Potentiated electron transference in α-Ag2WO4 microcrystals with Ag nanofilaments as microbial agent.

This study is a framework proposal for understanding the antimicrobacterial effect of both α-Ag2WO4 microcrystals (AWO) synthesized using a microwave hydrothermal (MH) method and α-Ag2WO4 microcrystals with Ag metallic nanofilaments (AWO:Ag) obtained by irradiation employing an electron beam to combat against planktonic cells of methicillin-resistant Staphylococcus aureus (MRSA). These samples were characterized by X-ray diffraction (XRD), FT-Raman spectroscopy, ultraviolet visible (UV-vis) measurements, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM). The results reveal that both AWO and AWO:Ag solutions have bacteriostatic and bactericidal effects, but the irradiated sample is more efficient; i.e., a 4-fold of the MRSA planktonic cells as compared to the nonirradiated sample was observed. In addition, first principles calculations were performed to obtain structural and electronic properties of AWO and metallic Ag, which provides strong quantitative support for an antimicrobacterial mechanism based on the enhancement of electron transfer processes between α-Ag2WO4 and Ag nanoparticles.

Effect of human whole saliva on the in vitro adhesion of Candida albicans to a denture base acrylic resin: a focus on collection and preparation of saliva samples.

OBJECTIVE: In studies on Candida albicans adhesion to surfaces, diverse protocols have been used for collection and preparation of saliva samples. Thus, this study investigated whether variations in the centrifugation parameters and number of donors of saliva would influence the adhesion of C. albicans to a denture base resin. METHODS: Resin acrylic samples (n = 72) were made and then divided into four groups: (a) control - specimens were left without preconditioning in saliva; (b) three experimental groups, in which the specimens were preconditioned with saliva collected from 15 volunteers and centrifuged at 12 000 g for 5 min (G1 ); from 15 volunteers and centrifuged at 18 000 g for 30 min (G2 ); and from one volunteer and centrifuged at 12 000 g for 5 min (G3 ). Candida adhesion was evaluated by both the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) reduction method and crystal violet staining. Data were analyzed by one-way analyses of variance (P = 0.05). RESULTS: For XTT reduction assay, groups G2 , G3 , and control were not significantly different, whereas group G1 showed significantly higher absorbance value than control. For crystal violet staining there were no significant differences among all groups. CONCLUSION: Variations in the centrifugation parameters and number of donors of saliva may influence C. albicans adhesion to denture base resins.

Clinical evaluation of failures in removable partial dentures.

The aim of this clinical study was to evaluate the effects of removable partial dentures on the support tissues and changes occurring in lower tooth-supported and bilateral distal-extension dentures, 5 years after placement. The study involved analysis of a total of 53 patients who received prosthetic treatment for removable partial dentures. The patients were divided into two groups. In group 1, the patients had a completely edentulous maxilla and an edentulous area with natural teeth remaining in both the anterior and posterior regions. In group 2, the patients had a completely edentulous maxilla and partially edentulous mandible with preserved anterior teeth. Tooth mobility, prevalence of caries, fracture of the abutment teeth, fracture and/or deformation of the removable partial denture components and stability of the denture base were evaluated. The use of a removable partial denture increased tooth mobility, reduced the prevalence of caries, and did not cause loss or fracture of the abutments or damage to their components, when compared with the baseline. It was concluded that there was no difference between the groups as evaluated in terms of tooth mobility, prevalence of caries, loss and fracture of the abutments or damage to the components of the removable partial denture.

Impact strength of denture base and reline acrylic resins: An in vitro study.

This study evaluated the impact strength of a denture base resin (Lucitone 550-L) and four reline resins (Tokuyama Rebase II-T; Ufi Gel Hard-U; New Truliner-NT, and Kooliner-K), both intact and in a reline combination (L/L, L/T, L/U, L/NT, and L/K). For each group (n = 20), half of the specimens were thermocycled before testing. Charpy tests were performed, and the impact strengths were calculated. Data were analyzed by two-way analyses of variance and Tukey's test (p = 0.05). For the intact groups, mean impact strength values for L (1.65 and 1.50) were significantly higher than those of the reline resins (0.38-1.17). For the relined groups, the highest mean impact strength values were produced by L/T (5.76 and 5.12), L/NT (6.20 and 6.03), and L/K (5.60 and 5.31) and the lowest by L/U (0.76 and 0.78). There were no significant differences between L and L/L. Thermocycling reduced the impact strength of T (from 0.73 to 0.38) and L/L (from 1.82 to 1.56).

Prevalence of Candida spp. associated with bacteria species on complete dentures.

OBJECTIVE: This study evaluated the prevalence of Candida spp., Streptococcus mutans and Staphylococcus aureus isolated from complete upper dentures. BACKGROUND: Factors that may increase the number of microorganisms in the oral cavity include denture-wearing and deficient denture hygiene. MATERIALS AND METHODS: Ninety denture wearers participated in this study. Collection of biological material from each denture was performed on all denture surfaces. Conventional biochemical methods were used to identify the microorganisms. Descriptive statistical analysis was performed on percentage data. RESULTS: Candida spp. were the most frequent microorganisms found on dentures (65.5%), while Strep. mutans and Staph. aureus were present in 53.3 and 34.4%, respectively. CONCLUSION: Candida species were the most frequent microorganisms on dentures, followed by Strep. mutans and Staph. aureus.

Evaluation of the occlusion vertical dimension of complete dentures after microwave disinfection.

OBJECTIVES: An increase in occlusal vertical dimension (OVD) after microwave disinfection may result in the need for adjustments in the complete dentures. This in vitro study evaluated the increase in OVD of maxillary complete dentures submitted to microwave disinfection protocols. MATERIAL AND METHODS: Thirty sets of complete dentures were evaluated as follows: Group 1-15 sets had the maxillary complete dentures submitted to microwave disinfection (650 W/3 min), once a week, for 4 weeks. Group 2-15 sets had the maxillary complete dentures submitted to microwave disinfection (650 W/3 min), three times a week, for 4 weeks. The vertical dimension was measured with a micrometre (in mm) before disinfection protocols (baseline readings) and after each week of disinfection. Data were analysed using Wilcoxon and Friedman tests (α = 0.05). RESULTS: For Group 1, no significant difference was found between the increases in OVD and zero, and no significant difference was found between the weeks. For Group 2, the increases in OVD were significantly greater than zero, and the Friedman test showed that weeks 3 and 4 had significantly greater changes than week 1 and that week 4 had significantly greater change than week 2. CONCLUSION: Microwave disinfection only promoted significant increase in OVD in Group 2, in which the values increased progressively.