Direct Exposure Test Research Articles

Insecticidal activity of <i>Ricinus communis L.</i> seed extract against <i>Spodoptera frugiperd</i>a J.E. Smith under laboratory and field conditions

Insecticidal activity of the aqueous extract of the castor seed (Ricinus communis L.) against the Fall Armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), one of the worst pests of maize crop, was assessed under laboratory and field conditions. In laboratory, the larvicidal activity of three concentrations of the extract that are 150 g/l, 200 g/l and 250 g/l and their effects on the development of FAW were evaluated through direct exposure and ingestion tests. The field experiment consisted of a randomized block design with two extract concentrations – 200 g/l and 250 g/l – and negative control consisted of untreated plots and positive control plots were treated with Emacot (Emamectin benzoate). Results of the laboratory experiments revealed considerable larvicidal activity of the extract through the ingestion test, inducing the larvae mortality of 75.8%, 60.3% and 46.5% for the extract concentrations of 250 g/l, 200 g/l and 150 g/l respectively, whereas positive (Emacot) and negative controls (emulsified water) recorded 100% and 3.3% of the larvae mortality, respectively. The field results showed 10% and 11% of infested plants in plots treated with 200 and 250 g/l, respectively, whereas Emacot-treated plots recorded 9.5% of infested plants. Untreated plots recorded the highest infested plants of 22.5%. The two- castor seed extract concentrations 200 g/l and 250 g/l reduced about 50% of maize plant infestation by FAW, thus could be a good candidate as alternative to chemical pesticides in controlling the pest.

FIRE BEHAVIOR OF PLASTER COMPOSITE MATERIALS LIGHTENED WITH PERLITE AND SUPER-ABSORBENT POLYMERS

The effects of fire on construction materials and systems can affect buildings in many different aspects, ranging from minor surface damage to severe effects that can affect their dimensional stability and load-bearing capacity. The aim of this research is to characterise the effects of fire on a new plaster material specially designed for the manufacture of prefabricated elements. This plaster composite is made by incorporating superabsorbent polymers and perlite, which reduces its density and thermal conductivity. In the study, real direct fire exposure tests were carried out, in order to subsequently carry out a mechanical characterisation of the new plaster composites and check the effects that a fire would have on them. The incorporation of sodium polyacrylate and potassium polyacrylate as superabsorbent polymers together with the addition of perlite has been shown to improve the fire resistance of the plaster composites. Keywords: fire behavior, lightweight plaster, perlite, superabsorbent polymers.

Observational extinction reduces fear and its retention among adolescents and adults

Observational fear learning has been notably understudied in fear learning research, especially the potential benefits of observational extinction. Additionally, no studies have investigated observational extinction during adolescence, a key developmental stage for the emergence of anxiety disorders. This study compared observational and direct fear extinction following observational fear acquisition among adolescents and adults. Participants underwent differential observational fear acquisition. Next, participants underwent one of three fear extinctions: (1) observational extinction, (2) direct extinction, (3) no-extinction. Thereafter, participants underwent a US reminder and finally, a direct exposure test. Skin conductance response (SCR), self-reported fear, and risk assessment were measured. Differential observational fear acquisition was demonstrated by both age groups across all measures. During extinction, the observational and direct extinction groups did not differ in differential extinction, however, during the US reminder the observational group exhibited higher SCR compared to the direct group, but not the no-extinction group. Finally, during the direct exposure test, the no-extinction group showed greater differential risk assessment and higher SCR compared to the observational and direct groups. Additionally, adolescents showed poorer discrimination between the CSs compared to adults. Observational extinction successfully reduced fear and its retention amongst youth and adults pointing to the potential benefit of vicarious exposure therapy.

Metabolome and transcriptome analyses of plants grown in naturally attenuated soil after hydrogen fluoride exposure

Accidental chemical leaks and illegal chemical discharges are a global environmental issue. In 2012, a hydrogen fluoride leak in Gumi, South Korea, killed several people and contaminated the environment. This leak also led to a significant decline in crop yield, even after the soil concentration of hydrogen fluoride decreased to below the standard level following natural attenuation. To determine the cause of this decreased plant productivity, we designed direct and indirect exposure tests by evaluating the metabolome, transcriptome, and phenome of the plants. In an indirect exposure test, soil metabolomics revealed downregulation of metabolites in vitamin B6, lipopolysaccharide, osmolyte, and exopolysaccharide metabolism. Next-generation sequencing of the plants showed that ABR1 and DREB1A were overexpressed in response to stress. Plant metabolomics demonstrated upregulation of folate biosynthesis and nicotinate and nicotinamide metabolism associated with detoxification of reactive oxygen species. These results demonstrate impaired metabolism of soil microbes and plants even after natural attenuation of hydrogen fluoride in soil. The novel chemical exposure testing used in this study can be applied to identify hidden damage to organisms after natural attenuation of chemicals in soil, as well as biomarkers for explaining the decline in yield of plants grown in soil near pollutant-emitting industrial facilities.

Volatiles mediated an eco‑friendly aphid control strategy of Chrysanthemum genus

The chrysanthemum aphid Macrosiphoniella sanborni is one of the most severe crop pests for the cultivated chrysanthemum. It is urgent to find efficient and eco‑friendly control strategies to promote the chrysanthemum industry's sustainable development. In this study, an aromatic wild species Chrysanthemum aromaticum were introduced to hybrid with Chrysanthemum nankingense to breed aphid-resistant offspring, and the role of the constitutive volatiles was revealed. Fifty interspecific hybrids were obtained and identified by morphology and SSR test. The aphid resistance of 28 robust hybrids was evaluated by combining the greenhouse test with the field test. Then, chrysanthemum aphids were exposed to the volatiles of two parents and ten hybrids to ensure volatiles influenced their choice. Sixty-five major compounds were detected in the parent and hybrid leaves using solid phase micro extraction-gas chromatography-mass spectrometry (SPME-GC–MS). Nineteen featured compounds of aphid resistant lines were selected by PCA analysis. Cis-4-thujanol was confirmed to be an effective repellent by the Y tube choice experiment and direct exposure tests. These findings have important implications for more eco-friendly control options of chrysanthemum aphids. C. aromaticum and these aphid-resistant hybrids can be used as breeding materials directly. Cis-4-thujanol has excellent potential to formulate natural insecticides.

Antibacterial effect of mouthwashes against Streptococcus mutans, Staphylococcus aureus and Enterococcus faecalis

Mouthwashes are one of the resources for controlling oral microbiota. They can reduce microorganisms, because they have antibacterial action and can access microorganisms even in areas of greater difficulty in the oral cavity. Objective: Antibacterial effect of some mouthwashes commonly used–0.12% chlorhexidine gluconate, 0.07% cetylpyridinium chloride, a solution based on essential oils (Listerine Zero), a solution of 1.33 mg benzethonium chloride / 25 mg hydrochloride lidocaine, a solution-based essential oils (Malvatricin) and 0.12% chlorhexidine + cetylpyridinium (Noplax)–was evaluated by means of agar diffusion and direct exposure tests. Material and methods: Strains of Streptococcus mutans (ATCC 27853), Staphylococcus aureus (ATCC 6538) and Enterococcus faecalis (ATCC 29212) were used in this study. For the agar diffusion test, Petri dishes with brain heart infusion agar (BHIA) were inoculated with the microbial suspensions. Sterile paper disks were immersed in the experimental for 1 min and then placed on the surface of BHIA. After incubation at 37ºC for 48 h, the diameters of the microbial inhibition halos were measured. For direct exposure test, no. 50 sterile absorbent paper points were immersed in the bacterial suspension for 5 min and then placed in Petri dishes and covered with 10 Ml of one of the tested solutions. At intervals of 1, 5, 10 and 30 min, absorbent paper points were removed from contact with substances and immersed in 7 mL of Letheen Broth and incubated at 37ºC for 48 h. Microbial growth was assessed by the turbidity of the culture medium. Results: The agar diffusion test showed inhibition halos greater than 10 mm for all substances against bacteria. In the direct exposure test, 0.12% chlorhexidine gluconate, 0.07% cetylpyridinium chloride, and 0.12% chlorhexidine associated with cetylpyridinium showed antibacterial effect on all the tested microorganisms after 10 min. Conclusion: The tested solutions showed antimicrobial effect on the biological indicators. The solutions of 0.12% chlorhexidine gluconate, 0.07% cetylpyridinium chloride and 0.12% chlorhexidine associated with cetylpyridinium showed antimicrobial effect on all biological indicators after 10 min.

Using a novel paradigm to examine observational fear-learning across development.

Fear-learning through observing others begins early in life. Yet, most observational fear-learning research has focused on adults. The current study used a novel developmentally appropriate observational fear conditioning paradigm to examine differences in observational fear-learning among children, adolescents, and adults. Thirty-six typically developing children, 41 typically developing adolescents, and 40 adults underwent differential observational fear conditioning followed by a direct exposure test. Skin conductance response (SCR) and self-reported fear were measured. Successful differential observational fear-learning was demonstrated in all three age groups as indexed by SCR, yet developmental differences emerged. Children showed overall higher physiological arousal during acquisition compared to adolescents and adults. Additionally, children reported less differential fear and were less successful at reporting the conditioned stimulus-unconditioned stimuluscontingency compared to adolescents and adults. Finally, adolescents tended to overgeneralize their fear compared with adults. This is the first study to compare observational fear-learning among children, adolescents, and adults. The novel task effectively induced observational fear-learning, particularly among adolescents and adults. Findings revealed developmental differences that have both theoretical and clinical implications.

The Antibacterial Effect of QMix, a Novel Root Canal Irrigant (Ex vivo Study)

Aims: To evaluate the antibacterial effect of a novel root canal irrigant, QMix, by evaluating its effect against E. faecalis and comparing it to 17% EDTA and 2% Chlorhexidine digluconate. Materials and Methods: Minimum Inhibitory Concentration (MIC), Minimum bactericidal concentration (MBC) and direct exposure test were the techniques used. In the MIC and MBC technique, the irrigants (QMix, 17% EDTA, 2% CHX) were serially diluted in BHI broth and 0.2 mL of the tested bacterial suspensions was added. Results were obtained on the basis of turbidity and growth on agar plates. In the direct exposure test, Enterococcus faecalis were exposed to QMix, 2% Chlorhexidinedigluconate and 17% EDTA for 5 seconds, 30 seconds and 3 minutes. Following exposure, samples were taken and serially diluted and incubated anaerobically on E. faecalis selective media for 24 hours to count the resistance of the bacteria. Results: In the MIC and MBC technique, CHX showed to be more effective against E. faecalis than both QMix and EDTA, as lower dilutions were required to inhibit growth of both bacteria. Ethylene diamine tetra acid (EDTA) was the least effective. In the direct exposure test, QMix was more effective than CHX and EDTA as it was the only solution to be able to kill all bacteria. Few E. faecalis cells remained even after exposure of bacteria to 3 minutes of EDTA and CHX. There was significant difference between QMix and both EDTA and CHX in killing of E. feacalis at 5 seconds exposure (p<0.05). QMix killed more than 95% of bacteria, whereas CHX and EDTA killed fewer than 20% (p<0.05). There was no statistical significance between the irrigant solutions at 3 minutes of exposure. Conclusions: In the MIC and MBC techniques, Chlorhexidinedigluconate was found superior to both QMix and EDTA. In the Direct Exposure Test, QMix showed the best performance as it was the only irrigant solution to kill all E. faecalis cells, as well as killing more than 95% of all bacteria at 5 seconds exposure.

Smear Layer Removal from Root Canal Dentin and Antimicrobial Effect of Citric Acid-modified Chlorhexidine.

Objective:To study the effectiveness of various concentrations of citric acid (CA) added to 2% chlorhexidine (CHX) on smear layer removal from the root canal wall and antimicrobial efficacy against Enterococcus faecalis (E. faecalis) and Candida albicans (C. albicans).Methods:Fifty-three single-rooted mandibular premolars were decoronate and the root canals underwent mechanical instrumentation using MTwo rotary files to size 40/0.06. The samples were then randomly divided into 5 groups according to the root canal irrigants to be used: 17% ethylenediaminetetraacetic acid (EDTA), 2% CHX, 1%, 6%, and 10% citric acid-modified 2% chlorhexidine (CAmCHX). Three teeth irrigated with phosphate-buffered saline (PBS) were used as a negative control. The smear layer removal effectiveness was evaluated under scanning electron microscopy (SEM). Images were randomly taken at the apical, middle, and coronal third level. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U tests. Disc diffusion and direct exposure tests were performed along with three additional control groups consisting of 1%, 6%, and 10% CA groups to assess and compare the antimicrobial efficacy of irrigants against E. faecalis and C. albicans. Statistical analysis was conducted using one-way ANOVA and Dunnett’s T3 tests.Results:Smear layer removal effectiveness in 17% EDTA group and 6% and 10% CAmCHX groups were not significantly different in the coronal and apical third of the root canal (P>0.05), however at the middle third of the root canal, the 10% CAmCHX group had significantly less remaining smear layer than all of the other experimental groups (P<0.05). There was significantly more smear layer remnant in the CHX group (P<0.01). For antimicrobial efficacy, the largest growth inhibition zone against E. faecalis was recorded in the 10% CAmCHX group (P<0.05). For planktonic E. faecalis, 1%, 6%, and 10% CAmCHX demonstrated an insignificant difference in antimicrobial efficacy compared to CHX (P>0.05). CA demonstrated no antifungal effect against C. albicans. Whereas, 6% and 10% CAmCHX resulted in the largest growth inhibition zone. Also, adding CA to CHX resulted in an insignificant difference in antifungal effect against planktonic C. albicans compared to CHX (P>0.05).Conclusion:When CA was added into CHX, the mixed irrigant demonstrated smear layer removal ability. Additionally, its antimicrobial effect remained the same.

Genotoxicity response of Vicia faba seedlings to cadmium in soils as characterized by direct soil exposure and micronucleus test.

To overcome the drawbacks of the Vicia faba root tip micronucleus test in soil using the solution extract method, we conducted a potting experiment by direct soil exposure. Cadmium was spiked into 3 typical soils (brown soil, red soil, and black soil) to simulate environmental concentrations (0.625, 1.25, 2.5, 5, and 10 mg kg-1). Multiple Vicia faba tissues (primary root tips, secondary root tips, and leaf tips) were sampled, and mitotic index (MI), chromosome aberration frequency (CA), and micronucleus frequency (MN) were used as endpoints after a seedling period of 5 days. The results showed a response between Cd concentrations and multiple sampling tissues of Vicia faba, and the secondary root tips responded to Cd stress the most, followed by primary root tips and leaf tips. Soil physicochemical properties (e.g., pH, total phosphorus, total organic carbon, etc.) influenced the genotoxicity of Cd, and pH was the dominant factor, which resulted in the genetic toxicity response of Cd in soils in the order: red soil > brown soil > black soil. The lowest observable effect concentration (LOEC) of Cd was 1.25 mg kg-1 for both brown soil and red soil and 2.5 mg kg-1 for black soil. In view of this, we suggested that soil properties should be considered in evaluating genotoxicity risk of Cd in soil, especially with soil pH range, and the secondary root tips should be taken as suitable test tissues in the MN test due to its more sensible response feature to Cd stress in soil.

Fire-resistant behaviour of some cellular materials treated with intumescent solutions

Cellular materials are a very wide range of materials characterized by a hollow structure. These materials exhibit various thermo-mechanical properties, which recommend them for the creation of ultra-light structures, both singular and as part of complex systems. In this paper we have studied the possibility of providing fire resistance properties of some cellular materials, using them together with intumescent solutions. A good response of these systems to the direct flame exposure tests conducted under laboratory conditions has been observed, which recommends them for further investigations.

Toxicological assessment of additively manufactured methacrylates for medical devices in dentistry

The paucity of information on the biological risks of photopolymers in additive manufacturing is a major challenge for the uptake of the technology in the construction of medical devices in dentistry. In this paper, the biocompatibility of methacrylates for denture bases, splints, retainers and surgical guides were evaluated using the innovative zebrafish embryo model, which is providing a high potential for toxicity profiling of photopolymers and has high genetic similarity to humans. Toxicological data obtained confirmed gradations of toxicity influenced by ethanol treatment, exposure scenarios and extraction vehicles. In direct exposure tests, juvenile fish exposed to non-treated methacrylates in ultrapure water showed accelerated toxicity endpoints compared to fish in transparent E3 medium. Similarly, toxic extracts induced mostly acute responses (embryonic mortality) in contrast to cumulative chronic (sublethal and teratogenic effects) in direct exposure. Methacrylates composed of >60% Ethoxylated bisphenol A dimethacrylate produced a relatively lower conversion rate in FTIR spectroscopy, but were safe in zebrafish bioassays after ethanol treatment. The study affirms that biocompatibility was influenced primarily by physico-chemical characteristics of the materials, which subsequently influenced their residual monomer content before and after immersion in ethanol. Given the precautionary implications of the study, we propose a 3-tiered approach i.e. using approved materials, apposite manufacturing parameters and post-processing techniques that together guarantee optimal results for medical devices. Statement of SignificanceThis study is timely and relevant since there is limited published literature that precisely describes the toxicological properties of additively manufactured methacrylates despite their increased popularity for medical devices. While it is generally accepted that the zebrafish excels as a model system for developmental toxicity, a further examination of its utility in this study using different protocols provides basis for its consideration and adoption at a crucial time when there is a lack of consensus regarding the most suited biological assessment methods for medical devices.

Cytotoxicity evaluation of orthodontic miniscrews

O objetivo deste estudo foi determinar a citotoxicidade induzida por mini-implantes ortodônticos conforme recebidos pelo fabricante, após a exposição a fluoretos, e após a exposição ao meio bucal. Oitenta e quatro mini-implantes de fabricantes brasileiros (SIN, INP e Neodent) foram divididos em sete grupos (n = 12): G1 - SIN como recebido do fabricante; G2 - SIN imerso durante quinze dias em NaF 0,05%; G3 - SIN exposto ao meiobucal; G4 - INP como recebido do fabricante; G5 - INP imerso durante quinze dias em NaF 0,05%; G6 - Neodent como recebido do fabricante; G7 - Neodent imerso por quinze dias em NaF 0,05%. Sua citotoxicidade foi avaliada por testes de exposição direta e indireta usando a levedura S. cerevisiae. O estresse oxidativo também foi avaliada por meio de teste de coloração de colônias. Os resultados mostraram não haver redução significativa da viabilidade celular sobre a exposição direta ou indireta a mini-implantes.

Trophic transfer and individual impact of nano-sized polystyrene in a four-species freshwater food chain

This study investigated the trophic transfer, individual impact, and embryonic uptake of fluorescent nano-sized polystyrene plastics (nanoplastics) through direct exposure in a freshwater ecosystem, with a food chain containing four species. The alga Chlamydomonas reinhardtii, water flea Daphnia magna, secondary-consumer fish Oryzias sinensis, and end-consumer fish Zacco temminckii were used as test species. In the trophic transfer test, algae were exposed to 50 mg/L nanoplastics, defined as plastic particles <100 nm in diameter; higher trophic level organisms were exposed through their diet. In the direct exposure test, each species was directly exposed to nanoplastics. Microscopic analysis confirmed that the nanoplastics adhered to the surface of the primary producer and were present in the digestive organs of the higher trophic level species. Nanoplastics also negatively affected fish activity, as measured by distance traveled and area covered, and induced histopathological changes in the livers of fish that were directly exposed. Additionally, nanoplastics penetrated the embryo walls and were present in the yolk sac of hatched juveniles. These observations clearly show that nanoplastics are easily transferred through food chain, albeit because of high experimental dosages. Nevertheless, the results strongly point to the potential health risks of nanoplastic exposure.

SUSCEPTIBILITY OF SPOTTED WING DROSOPHILA (Drosophila suzukii (Matsumura, 1931)) PUPAE TO ENTOMOPATHOGENIC FUNGI

Spotted wing drosophila (Drosophila suzukii (Matsumura, 1931), Diptera, Drosophilidae) management is difficult mainly because of its short generation time, polyphagy and serrated ovipositor, but also because its larvae can pupate in the orchard soil and are thus protected from insecticide applications. We hypothesized that insect-pathogenic soil fungi could successfully infect Drosophila suzukii pupae in soil environment. We tested several entomopathogenic or soil fungi against pupae in a) conidia-spiked soil, b) via direct applications of conidia, and c) by dipping pupae into conidial suspensions. Metarhizium brunneum Petch strain H.J.S. 1154 significantly reduced fly emergence in conidia spiked soil and bioinsecticide Naturalis (based on entomopathogenic fungus Beauveria bassiana (Bals.-Criv.) Vuill. in direct exposure tests. Our attempt to determine IC50 of pupal hatching rate by dipping D. suzukii pupae into conidial suspensions was unsuccessful. We conclude that the pupal stage is probably too brief to allow entomopathogens to cause a significant reduction of fly emergence. According to our results and published articles, the fungal biocontrol potential would probably best be evaluated in spray applications against adult flies.

Germicidal activity of plant extracts of Origanum vulgare and Rosmarinus officinalis against Sporothrix schenckii complex

The literature shows that is a resistance by the microorganisms against commercial products used for the disinfection of contaminated environments. Due to this, the aim of this study was to evaluate the activity of the tincture, aqueous extract (decoction and infusion) and hydroalcoholic extract of Origanum vulgare and Rosmarinus officinalis, as an alternative to disinfectants, using the technique of direct exposure, against Sporothrix schenckii complex. For this, the direct exposure tests, with fungal isolates from clinical cases pertaining to dogs and cats with sporotrichosis, were used to evaluate the sensitivity of Sporothrix spp. against plants extracts, with the action evaluated in the times of 5, 10 and 15 minutes of exposure . As a positive control, it was used a sterile water solution containing innocuous and disinfectants used to control was sodium hypochlorite alcohol and 70°GL. As a result, it can be shown the sensitivity of the fungal isolates front to tincture of Origanum vulgare and Rosmarinus officinalis and hydroalcoholic extract of Origanum vulgare at all times of exposure, in 10% concentration of the extract.

Inhibition of Enterococcus faecalis by Calcium Peroxide.

To investigate the inhibition of Enterococcus faecalis by calcium peroxide (CaO₂). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Enterococcus faecalis by CaO₂ and calcium hydroxide (Ca(OH)₂) were determined by direct exposure tests (n = 10). The inhibition zone of E. faecalis mycoderm treated with CaO₂ and Ca(OH)₂ paste (53% w/w) was observed using agar diffusion tests (n = 20). The inhibition of E. faecalis biofilms by CaO₂/phosphate-buffered saline (PBS) and Ca(OH)₂/PBS suspensions were observed using confocal laser scanning microscopy and the percentages of live bacteria in the biofilms calculated. The MIC of Ca(OH)₂ (4.5 to 5.5 mg/ml) was higher than the MIC of CaO₂ (2.0 to 2.5 mg/ml) (P < 0.05), and the MBC of Ca(OH)₂ (14.5 to 15.5 mg/ml) was higher than that of CaO₂ (3.0 to 3.5 mg/ml) (P < 0.05). No inhibition zone was observed for Ca(OH)₂ in agar diffusion tests, while the diameter of the inhibition zone around CaO₂ was 8.6 ± 0.4 mm. There were significant differences between groups in the percentages of surviving bacteria in E. faecalis biofilms after treatment (P < 0.05): group CaO₂ < group Ca(OH)₂ < group PBS < group BHI. The inhibition of E. faecalis by CaO₂ was greater than that by Ca(OH)₂.

Calcium Enriched Mixture and Mineral Trioxide Aggregate Activities against Enterococcus Faecalis in Presence of Dentin.

The purpose of this in vitro study was to compare the antibacterial activity of Calcium Enriched Mixture (CEM) with ProRoot Mineral Trioxide Aggregate (MTA) against Enterococcus faecalis (E. faecalis) in the presence/absence of dentin powder. Two series of freshly mixed (10, 50, and 100 mg), set crushed powder (10, 50, and 100 mg), and pieces of uncrushed set (50, 100 mg) of CEM and MTA were prepared (n = 32 groups). All samples were suspended in normal saline for direct exposure test against E. faecalis; in the second series, 50 mg of the dentin powder was also added to the solution. Dentin powder suspension and bacterial suspension served as negative and positive control groups, respectively (n = 2). The suspensions were incubated at room temperature for 1, 60, and 240 min; each group was tested five times and survival of the bacteria in test solutions was assessed by 10-fold serial dilutions and cultured on Brain Heart Infusion (BHI) plates. The plates were incubated at 37ºC. The mean values of log10 CFU were calculated and compared in all tested groups. The total number of tests added up to 510 times. In presence of dentin powder, freshly mixed powder from set materials, and pieces of uncrushed set materials of both tested cements killed > 95% of the bacterial cell in 1 min. Adding dentin powder caused an increase in antibacterial activity of freshly mixed powder from crushed set CEM and MTA but no acceleration in bacterial killing was observed, when dentin was mixed with set or uncrushed cements. Dentin powder alone reduced the number of viable bacteria in the 4-hour duration. There were no significant differences between different weights of freshly mixed, crushed set powder and uncrushed set of CEM cement and MTA at different times. Under the conditions of this in vitro study, CEM cement as well as MTA have antibacterial effects against E. faecalis. The addition of equal amounts of dentin powder to the suspension of CEM or MTA resulted in swifter elimination of bacteria.

The antimicrobial activity of alpha-bisabolol and tea tree oil against Solobacterium moorei, a Gram-positive bacterium associated with halitosis

ObjectiveTo investigate the antimicrobial effect of alpha-bisabolol and tea tree oil alone and in combination against the halitosis-associated Gram-positive bacillus Solobacterium moorei. DesignThe inhibitory activity of alpha-bisabolol and tea tree oil against the reference strain S. moorei CCUG39336 and four clinical S. moorei isolates was investigated by a direct exposure test. Additionally, the ability of alpha-bisabolol to increase the sensitivity of S. moorei was tested by pretreating the bacteria with sublethal concentrations prior to the administration of tea tree oil. ResultsA dose-dependent killing was observed for the antimicrobial agents in a direct exposure test with the reference strain S. moorei CCUG39336. Concentrations of ≥0.5% tea tree oil caused decreases in viability of >5 log colony forming units/ml even after short incubation periods, while bacterial viability was less affected by alpha-bisabolol. The combination of 0.1% alpha-bisabolol plus 0.05% tea tree oil showed a synergistic effect on S. moorei strain CCUG39336 and on two of the four clinical S. moorei isolates tested. However, incubation of S. moorei with a sublethal concentration of 0.1% alpha-bisabolol for three days prior to the administration of 0.05% tea tree oil did not enhance the antibacterial effect of tea tree oil. ConclusionHalitosis-associated bacterium S. moorei is susceptible to the antimicrobial agents tea tree oil and alpha-bisabolol, suggesting that these compounds might be beneficial in oral healthcare products.

Study of Effect on Cell proliferation and Hemolysis of HAP and TCP Nanometer Particles

Hydroxyapatite (HAP) and tricalcium phosphate (TCP) nanoparticles (NPs) are in current use covering a wide range of medical applications, hence, it is indispensable to study the potential side effect acting on living organism, and to figure out the biocompatibility evaluation model of nanoparticles for standardization and methodology. In the present study, HAP and TCP NPs were selected and their diameters were within 30-80nm. Cytotoxicity in vitro was analyzed by agar overlay and direct contact exposure test was conducted to evaluate potential toxicity to SD rat macrophages, and hemolysis test of NPs was performed in compliance with ISO 10993-12 guidelines. The results showed that both HAP and TCP NPs could inhibit proliferation of macrophages when their concentration was reached to 20 µg/ml, and the extent of haemolysis would be increased more than 5% while 1000µg/ml NPs were contacted with rabbit blood cells. Furthermore, TCP NPs could induce obvious hemolysis reaction and inhibit proliferation of macrophages compared with group of HAP NPs at the same concentration.