Estrogenic activity of tissue conditioners in vitro

An Innovative Approach for Management of Unfavorable Bilateral Mandibular Lingual Undercuts With Collapsible Type Complete Denture: A Case Report

Advanced and uneven residual ridge resorption in mandibular edentulous arches leads to non-retentive and unstable dentures. The hardness of traditional heat-cured acrylic resin makes extending the denture base into bilateral lingual undercuts challenging. This can cause supporting tissue damage, pain, and ulcerations during denture insertion and removal. Although clinical challenges related to limited mouth opening were addressed by modifying the impression technique, incorporating hinges, swing lock attachments, and stainless-steel posts to form collapsible denture bases, there are no documented case reports with proper follow-up regarding the use of such type dentures in cases of mandibular lingual undercuts. A 68-year-old male patient reported, with the chief complaint of missing teeth in the upper and lower jaws for five years and wanting replacement. The intraoral clinical examination yielded findings of a severely compromised mandibular ridge (ACP Class IV) and a moderately compromised maxillary ridge (ACP Class II). In the maxillary arch, the presence of anterior labial undercut, and bilateral undercuts lateral to tuberosity were evident. The patient reported pain on palpation bilaterally in the tuberosity region. Prolonged mandibular edentulism and uneven bone resorption resulted in unfavorable bilateral lingual undercuts, with class III (M.M. House) border tissue attachment in the labial and buccal aspects of the basal tissue area. After enumerating the treatment options, the patient opted for a removable prosthesis for the maxillary and mandibular arch. Pre-prosthetic surgery was done to eliminate tuberosity undercuts. Since the patient was unwilling to take up pre-prosthetic surgical corrections for the mandibular lingual undercuts, a significant challenge emerged: creating a retentive mandibular complete denture without compromising the peripheral seal and retention. A conventional complete denture was fabricated after blocking the unfavorable undercut and reducing the height of the flange. On the recall appointment, the patient complained of reduced retention and food lodgment in the intaglio surface of the denture and pain due to denture movement on mastication. In this case report, stainless steel hinges have been added to the lingual flange of the mandibular complete denture to make it collapsible. The resultant denture facilitated reduced tissue trauma and discomfort during denture removal and insertion and had satisfactory retention and stability compared to the former denture. These collapsible type dentures can be used as an alternative to flexible dentures, wherein patients can't afford surgeries or flexible dentures.

Polymeric Denture Base Materials: A Review

An ideal denture base must have good physical and mechanical properties, biocompatibility, and esthetic properties. Various polymeric materials have been used to construct denture bases. Polymethyl methacrylate (PMMA) is the most used biomaterial for dentures fabrication due to its favorable properties, which include ease of processing and pigmenting, sufficient mechanical properties, economy, and low toxicity. This article aimed to comprehensively review the current knowledge about denture base materials (DBMs) types, properties, modifications, applications, and construction methods. We searched for articles about denture base materials in PubMed, Scopus, and Embase. Journals covering topics including dental materials, prosthodontics, and restorative dentistry were also combed through. Denture base material variations, types, qualities, applications, and fabrication research published in English were considered. Although PMMA has several benefits and gained popularity as a denture base material, it has certain limitations and cannot be classified as an ideal biomaterial for fabricating dental prostheses. Accordingly, several studies have been performed to enhance the physical and mechanical properties of PMMA by chemical modifications and mechanical reinforcement using fibers, nanofillers, and hybrid materials. This review aimed to update the current knowledge about DBMs' types, properties, applications, and recent developments. There is a need for specific research to improve their biological properties due to patient and dental staff adverse reactions to possibly harmful substances produced during their manufacturing and use.

Comparison of Mechanical Properties of Three Tissue Conditioners: An Evaluation In Vitro Study

Introduction: Tissue conditioners have been widely used in various clinical applications in dentistry, such as treating inflamed alveolar ridges, temporarily relining partial and complete dentures, and the acquisition of functional impressions for denture fabrication. This study aimed to investigate the mechanical properties of the most prevalent tissue conditioner materials on the market, including Tissue Conditioners (TC), Visco Gel (VG), and FITT (F). Materials and Methods: The three tissue conditioners, TC, VG, and F, were assessed based on the parameters mentioned above. The following tests were performed based on the ISO 10139-1 and ISO 10139-2 requirements: Shore A hardness, denture plate adhesion, sorption, water solubility, and contraction after 1 and 3 days in water. Additional tests are described in the literature, such as ethanol content and gelling time. The tests were carried out by storing the materials in water at 37 °C for 7 days. Results: The gel times of all tested materials exceeded 5 min (TC = 300 [s], VG = 350 [s]). In vitro, phthalate-free materials exhibited higher dissolution in water after 14 days (VG = -260.78 ± 11.31 µg/mm2) compared to F (-76.12 ± 7.11 µg/mm2) and experienced faster hardening when stored in distilled water (F = 33.4 ± 0.30 Sh. A, VG = 59.2 ± 0.60 Sh. A). They also showed greater contractions. The connection of all materials to the prosthesis plate was consistent at 0.11 MPa. The highest counterbalance after 3 days was observed in TC = 3.53 ± 1.12%. Conclusions: Materials containing plasticizers that are not phthalates have worse mechanical properties than products containing these substances. Since phthalates are not allowed to be used indefinitely in medical devices, additional research is necessary, especially in vivo, to develop safe materials with superior functional properties to newer-generation alternatives. In vitro results often do not agree fully with those of in vivo outcomes.

Evaluation of Placental Toxicity of Five Essential Oils and Their Potential Endocrine-Disrupting Effects

Pregnant women may use EOs in case of morning sickness, nausea, stress management, etc. Little is known about the potential danger that EOs represent for the placenta and therefore for the pregnancy. Our aim was to explore and compare the placental toxicity and potential endocrine disrupting effects of niaouli, orange, tea tree, wintergreen and ylang-ylang EOs, and their key compounds: 4-terpineol, 1,8-cineol, limonene, methyl salicylate and benzyl salicylate. We studied the release of four hormones and the activation of P2X7 receptor in JEG-Tox human placental cells as key biomarkers for endocrine toxicity. We observed that niaouli, orange, tea tree, wintergreen and ylang-ylang EOs and their key components disrupted at least one of the studied hormones but none of them activated the P2X7 cell death receptor. The tested EOs appear then to be more hormonal modulators rather than EDCs in human placental cells. The hormonal effects observed with the key components were very different from those observed with the EOs. EOs are very complex mixtures, and it is essential to study whole EOs rather than their components individually in safety assessment.

A critical assessment of the estrogenic potency of benzyl salicylate

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Benzyl salicylate (BS) is on priority lists for evaluation of estrogenic effects.

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New data in both MCF7 (E-screen) and luciferase transactivation assays.

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Potency of BS is 21′000′000-fold lower than estradiol in transactivation assay.

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Potency of BS is 36′000′000-fold lower than estradiol in E-screen.

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Potency is > 1000-fold below human relevant potency threshold.

Benzyl salicylate (BS) is a natural ingredient of essential oils and a widely used fragrance chemical. A number of in vitro screening studies have evaluated the estrogenic potential of BS with ambiguous results. Lack of dose-response information for the positive control 17β-estradiol (E2) in most studies makes an assessment of the relative potency and efficacy challenging. Notwithstanding this difficulty, BS has been added as the only fragrance ingredient to the list of the first 14 substances to be screened as potential endocrine disruptors by the European Scientific Committee for Consumer Safety (SCCS) and it is included in the Community rolling action plan (CoRAP) of the European REACH regulation to be assessed for the same property. Here we review all literature evidence and present new data to quantify the in vitro potency and efficacy of BS vs. E2 with full dose response analysis in both an estrogen response element (ERE) depending reporter gene assay and in the MCF7 cell proliferation (E-screen) assay. In both assays, very similar results for BS were found. BS is a partial agonist exhibiting 35–47 % maximal efficacy and it is active only close to the cytotoxic concentration. The extrapolated concentration to achieve 50 % efficacy is 21′000′000 higher as compared to E2 in the reporter gene assay. A ca. 36′000′000 higher concentration of BS as compared to E2 is required to reach equivalent partial cell proliferation stimulation in the MCF7 proliferation assay. This potency is significantly below the agonistic activity of known chemicals which cause estrogenic effects in in vivo assays. Importantly, in this study the weak agonistic activity is for the first time directly related to the activity of E2 in a full quantitative comparison in human cell lines which may help ongoing evaluations of BS by regulatory bodies.

Estrogenic activity of capsule coffee using the VM7Luc4E2 assay

Coffee brewed from capsule machines may contain estrogenic chemicals migrated from plastic, but the estrogenic activity of capsule coffee has not been evaluated. This study evaluated the estrogenic activity of capsule coffee using the VM7Luc4E2 estrogen receptor transcriptional activation assay. Estrogenic potentials of six capsule coffee samples were calculated using relative maximum amplitude response of E2 (>15%RME2 indicative of estrogenic activity) and estradiol equivalent factor (EEF). Estrogenic chemical content was determined using ultra-performance liquid chromatography with tandem mass spectrometry. All capsule coffee samples possessed estrogenic activity (48-56%RME2). EEFs were 6-7 orders of magnitude lower than that of E2, (1.2 × 10-7-1.7 × 10-6), indicating substantially weaker estrogenic potencies. Bisphenol A, bisphenol F, benzophenone, 4-nonylphenol, dibutyl phthalate, and dimethyl terephthalate were detected in capsule coffee. Capsule coffee exhibited estrogenic activity in vitro, and its estrogenic chemical content is likely driving its estrogenicity, warranting further investigations to fully understand the degree to which they are related and to predict the estrogenic potential based on the concentration of estrogenic chemicals.

Influence of monomer type, plasticizer content, and powder/liquid ratio on setting characteristics of acrylic permanent soft denture liners based on poly(ethyl methacrylate/butyl methacrylate) and acetyl tributyl citrate

We evaluated the influence of monomer type, plasticizer content, and powder/liquid (P/L) ratio on the setting characteristics of light-cured acrylic permanent soft denture liners based on poly(ethyl methacrylate/butyl methacrylate). Two monomers, iso-butyl methacrylate (i-BMA) and 2-ethylhexyl methacrylate (2-EHMA), that contained various concentrations of the plasticizer acetyl tributyl citrate (ATBC) and trace amounts of the photo initiator and reducing agent were used. The P/L ratio was 1.0 or 1.2. The gelation time was measured using a controlled stress rheometer. Materials with i-BMA had shorter gelation times than those for materials with 2-EHMA. The gelation time increased exponentially with increasing plasticizer content. A higher P/L ratio led to a shorter gelation time. The effects of monomer type and plasticizer content were larger than that for the P/L ratio. These results show that 2-EHMA is a suitable monomer for soft denture liners and that the setting characteristics can be controlled via ATBC content.

Reproductive toxic potential of phthalate compounds - State of art review

Phthalates are pervasive compounds, and due to the ubiquitous usage of phthalates, humans or even children are widely exposed to them. Since phthalates are not chemically bound to the plastic matrix, they can easily leach out to contaminate the peripheral environment. Various animal and human studies have raised vital health concern including developmental and reproductive toxicity of phthalate exposure. The present review is based upon the available literature on phthalates with respect to their reproductive toxic potential. Common reproductive effects such as declined fertility, reduced testis weight, variations in accessory sex organs and several female reproductive disorders appeared to be largely associated with the transitional phthalates. Among the higher molecular weight phthalates (≥ C7), di-isononyl phthalate (DINP) produces some minor effects on development of male reproductive tract and among low molecular weight phthalates (≤C3), di-methyl (DMP) and di-isobutyl (DIBP) phthalate produce some adverse effects on male reproductive system. Whereas transitional phthalates such as di-butyl phthalate, benzyl butyl phthalate, and di-(2-ethylhexyl) phthalate have shown adverse effects on female reproductive system. Owing to these, non-toxic alternatives to phthalates may be developed and use of phthalates could be rationalized as an important issue where human reproduction system is involved. Though, more epidemiological studies are needed to substantiate the reported findings on phthalates.

The Dynamic Viscoelasticity of Dental Soft Polymer Material Containing Citrate Ester-Based Plasticizers

The aim of this study was to investigate the dynamic viscoelasticity of dental soft polymer material containing citrate ester-based plasticizers. Three kinds of citrate ester-based plasticizer (Citroflex^® C-2: TEC, Citroflex^® A-2: ATEC, and Citroflex^® A-4: ATBC), with the combination of 5 wt% ethyl alcohol, were used as the liquid phase. The dynamic viscoelastic properties of nine ethyl methacrylate polymers: (A, B, C, D, E, F, G, H, and I) were immersed in 37 °C distilled water for 0, 1, 3, 7, 14 and 30 days, respectively. The dynamic viscoelastic properties were measured at 37 °C with an automatic dynamic mechanical analyzer. The shear storage modulus (G′), shear loss modulus (G″), and loss tangent (tan δ) were determined at 1 Hz. These parameters were statistically analyzed by two-way and one-way ANOVA and Tukey’s multiple comparison test at a predetermined significance level of 0.05. A significant difference was found among the materials in terms of the dynamic viscoelasticity. The materials containing citrate ester-based plasticizer ATBC showed the most stable dynamic viscoelasticity. Considering the limitations of this study, the results suggest that the inclusion of citrate ester-based plasticizer can improve the durability of dental soft polymer materials.

TCDD-induced antagonism of MEHP-mediated migration and invasion partly involves aryl hydrocarbon receptor in MCF7 breast cancer cells

Evidence has shown that the activation of AhR (aryl hydrocarbon receptor) can promote cancer cell metastasis. However, limited studies have been carried out on mixed exposure to endocrine-disrupting chemicals (EDCs), especially in human breast cancer. Therefore, using MCF7 human breast cancer cells, we investigated the effects of coexposure to MEHP (mono 2-ethylhexyl phthalate) and TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) on cell migration and invasion, as well as the roles of AhR and the MMP/slug pathway. Our data suggest that MEHP or TCDD can induce migration and invasion in MCF7 cells, and the promotion is partly AhR dependent. We also observed that MEHP antagonized TCDD to reduce AhR-mediated CYP1A1 expression. Subsequently, we revealed that MEHP recruited AhR to dioxin response element (DRE) sequences and decreased TCDD-induced AhR-DRE binding in CYP1A1 genes. Overall, MEHP is a potential AHR agonist, capable of decreasing TCDD-induced AhR-DRE binding in CYP1A1 genes. The antagonizing effect of coexposure led to the inhibition of the epithelial-mesenchymal transition (EMT) in MCF7 cells. Our study provides new evidence for the potential mechanisms involved in EDCs exposure and their interactions in EMT.

Safety Assessment of Benzyl Alcohol, Benzoic Acid and its Salts, and Benzyl Benzoate

Benzyl alcohol, benzoic acid and its salts, and benzyl benzoate function mostly as fragrance ingredients/preservatives in cosmetic products. The Cosmetic Ingredient Review Expert Panel previously established concentration limits for benzyl alcohol, benzoic acid, and sodium benzoate in cosmetics and determined that the available data were insufficient to support the safety of these ingredients during inhalation exposure. After reviewing newly available data, it was concluded that benzyl alcohol, benzoic acid and its salts, and benzyl benzoate are safe in the present practices of use and concentration described in this safety assessment.

The effect of crude drugs on the angiogenic property and dynamic viscoelasticity of PEMA-based soft polymer materials

This study aimed to determine the effect of crude drugs on the dynamic viscoelasticity and angiogenic property of soft polymer materials, in vitro. Two kinds of polyethyl methacrylates, and crude drugs (Astragalus membranaceus Bunge [HQ] and Salvia miltiorrhiza Bunge [DS]) were used in their powdered forms. And, acetyl tributyl citrate and ethyl alcohol were used in the liquid form. The dynamic viscoelasticity of each specimen was measured after 0, 1, 3, 7, 14 and 28 days of immersion in distilled water. The CellPlayer angiogenesis PrimeKit assay was used to test angiogenesis. Significant differences in dynamic viscoelasticity were observed among the materials. Specimens containing 1 wt% HQ showed higher angiogenic activity than those containing 5 wt% and 10 wt% HQ, and DS. Our results suggest that the addition of low amounts of crude drugs to soft polymer materials may promote angiogenesis in human tissues.

Estrogenic endocrine disruptors: Molecular mechanisms of action

A comprehensive summary of more than 450 estrogenic chemicals including estrogenic endocrine disruptors is provided here to understand the complex and profound impact of estrogen action. First, estrogenic chemicals are categorized by structure as well as their applications, usage and effects. Second, estrogenic signaling is examined by the molecular mechanism based on the receptors, signaling pathways, crosstalk/bypassing and autocrine/paracrine/homeostatic networks involved in the signaling. Third, evaluation of estrogen action is discussed by focusing on the technologies and protocols of the assays for assessing estrogenicity. Understanding the molecular mechanisms of estrogen action is important to assess the action of endocrine disruptors and will be used for risk management based on pathway-based toxicity testing.

The dynamic viscoelasticity and plasticizer leachability of tissue conditioners

OBJECTIVES

Dynamic viscoelasticity is one of the most important characteristics of tissue conditioners. Leaching of plasticizer from tissue conditioners may cause changes in the dynamic viscoelasticity of these materials. The purpose of this study was to determine the dynamic viscoelasticity and plasticizer leachability of commercial tissue conditioners.

MATERIALS AND METHODS

Five commercial tissue conditioners were used in this study: COE Comfort (CC), Fit Softer (FS), Hydro-Cast (HC), Soft Conditioner (SC) and Visco-Gel (VG). Five specimens of each material were stored in 37°C distilled water. The dynamic viscoelasticity and plasticizer leaching of each specimen were measured at 0, 1, 3, 7 and 14 days after immersion using a dynamic mechanical analyzer and high performance liquid chromatography. Data were analyzed using one-way anova and Student-Newman-Keuls test (α = 0.05).

RESULTS

Significant differences in dynamic viscoelasticity and plasticizer leaching were found among the materials. The dynamic viscoelasticity of all materials increased or decreased significantly with time. Rapid changes in dynamic viscoelasticity were evident on day 1 after water immersion. The material CC recorded the highest level of plasticizer leaching.

CONCLUSION

These results suggest that the dynamic viscoelasticity of commercial tissue conditioners is affected by plasticizer leaching. However, these effects are limited.

The dynamic viscoelasticity and water absorption characteristics of soft acrylic resin materials containing adipates and a maleate plasticizer

The purpose of this study was to investigate the use of different plasticizers in soft acrylic resin materials to reduce leaching of the plasticizer and thus increase the durability of tissue conditioners. Samples were prepared containing different combinations of three types of polymer/copolymer powder and four types of plasticizer liquid (DEHM, DIBA, DAA and DINA). The dynamic viscoelasticity of each sample was measured after water immersion using a dynamic mechanical analyzer. Water absorption, solubility and weight change were also measured. A significant difference was found among the materials regarding dynamic viscoelasticity, water absorption and solubility. The samples containing P-n-BMA had the most stable G' and G'' scores throughout the immersion. P-n-BMA is the most suitable powder together with DEHM as the most suitable liquid component for a tissue conditioner. These results suggest that it is possible to improve the durability of tissue conditioners by combining different polymers and plasticizers.

Development of an orthodontic elastic material using EMA-based resin combined with 1-butanol

For the development of new orthodontic elastic material, 1-butanol was added to PEMA-TA/HX resin. In the present study, basic experiments to reveal the mechanical properties of the materials were conducted. FT-IR spectroscopy showed that addition of 1-butanol did not cause any chemical changes to the PEMA-TA/HX resin. After addition of 1-butanol to PEMA-TA/HX resin, the modulus of elasticity, instantaneous modulus elasticity, retarded elasticity and viscosity were lowered in a concentration-dependent manner, whereas the elastic strain was increased in a concentration-dependent manner. Moreover, on the application of heat a shape-memory effect was observed. These results suggest that the modulus of elasticity of this material can be adjusted. Additionally, this material has the ability to restore force as a function of its shape-memory effect in cases of plastic deformation at the insertion of appliances. This new orthodontic elastic material has the potential to be clinically effective in orthodontic treatment.

High-dose dibutyl phthalate improves performance of F1 generation male rats in spatial learning and increases hippocampal BDNF expression independent on p-CREB immunocontent

Dibutyl phthalate (DBP), an important representative of endocrine disrupting chemical, is suspected of affecting the cognitive function of humans and animals. In this study, effects of DBP on maze performance in male rats were evaluated by spatial learning tasks; the effects of DBP on the expression of brain-derived neurotrophic factor (BDNF) were also analyzed in both mRNA and mature protein levels in the hippocampus, with intent to investigate the possible mechanism underlying the behavioral findings. Pregnant Wistar rats were treated orally by gavage with 0, 25, 75, 225 and 675mgDBP/kgBW/day from gestational day (GD) 6 to postnatal day (PND) 21, and then the weaned offspring continued receiving the same treatment till PND 28. We found that male pups treated with high-dose DBP showed enhancement in spatial acquisition in a Morris water maze during PNDs 30-33, and displayed better retention of spatial memory in a probe trial after a reverse trail during PNDs 60-62. Real-time PCR and western blotting analysis of the hippocampus from DBP-treated male rats on PND 21 revealed an increase in BDNF expression, compared to the vehicle-matched control. BDNF variant III, a transcription promoted by active CREB (i.e. p-CREB), as well as the immunocontent of p-CREB, was scarcely altered by the treatment. Our results suggest that developmental treatment with high-dose DBP improves spatial memory in male rats, and this effect may be related to an increase in BDNF expression in the hippocampus in a p-CREB independent route.

Differential cytotoxic effects of mono-(2-ethylhexyl) phthalate on blastomere-derived embryonic stem cells and differentiating neurons

Potential applications of embryonic stem (ES) cells are not limited to regenerative medicine but can also include in vitro screening of various toxicants. In this study, we established mouse ES cell lines from isolated blastomeres of two-cell stage embryos and examined their potential use as an in vitro system for the study of developmental toxicity. Two ES cell lines were established from 69 blastomere-derived blastocysts (2.9%). The blastomere-derived ES (bm-ES) cells were treated with mono-(2-ethylhexyl) phthalate (MEHP) in an undifferentiated state or after directed differentiation into early neural cell types. We observed significantly decreased cell viability when undifferentiated bm-ES cells were exposed to a high dose of MEHP (1000 microM). The cytotoxic effects of MEHP were accompanied by increased DNA fragmentation, nuclear condensation, and activation of Caspase-3, which are biochemical and morphological features of apoptosis. Compared to undifferentiated bm-ES cells, considerably lower doses of MEHP (50 and 100 microM) were sufficient to induce cell death in early neurons differentiated from bm-ES cells. At the lower doses, the number of neural cells positive for the active form of Caspase-3 was greater than that for undifferentiated bm-ES cells. Thus, our data indicate that differentiating neurons are more sensitive to MEHP than undifferentiated ES cells, and that undifferentiated ES cells may have more efficient defense systems against cytotoxic stresses. These findings might contribute to the development of a new predictive screening method for assessment of hazards for developmental toxicity.

Establishment of a transgenic yeast screening system for estrogenicity and identification of the anti-estrogenic activity of malachite green

Endocrine disruptors refer to chemical compounds in the environment which interfere with the endocrine systems of organisms. Among them, environmental estrogens pose serious problems to aquatic organisms, in particular fish. It is therefore important and necessary to have a fast and low-cost system to screen the large number of different chemical compounds in the aquatic environment for their potential endocrine disrupting actions. In this study, a screening platform was developed to detect xenoestrogens in the aquatic environment using the fission yeast Schizosaccharomyces pombe, and applied for compound screening. The aim was to demonstrate any significant potential differences between the fish screening system and the human screening system. To this end, a yeast expression vector harboring a fish estrogen receptor alpha and a reporter vector containing the estrogen responsive element fused with the Escherichia coli LacZ gene were constructed. After transformation with these two vectors, the transformed yeast clones were confirmed by Western blotting and selected on the basis of the beta-galactosidase activity. In this transgenic yeast system, the natural estrogen (estradiol) and other known xenoestrogens such as diethylstilbestrol, bisphenol A, genistein and dichloro-diphenyl-trichloroethane exhibited dose-dependent activities. Using this system, more than 40 putative endocrine disruptors including phytoestrogens, pesticides, herbicides, industrial dyes and other industrial chemicals were screened. Ten of them were demonstrated to exhibit estrogenic actions. Industrial dyes such as malachite green (MG) that disrupt thyroid hormone synthesis are extensively used and are widely distributed in the aquatic environment. Using this system, MG did not show any estrogenic action, but was demonstrated to exhibit anti-estrogenic activity.

Cytocompatibility of a tissue conditioner containing vinyl ester as a plasticizer

In the current study, we examined the cytocompatibility of eight vinyl esters as candidate plasticizers for producing phthalate- and ethanol-free tissue conditioners. We measured the estrogenic activity and cytotoxicity of vinyl esters in human fibroblasts and keratinocytes using an E-screen assay and a mitochondrial dye conversion assay, respectively. We also assessed the cytotoxicity of three prototype materials and commercially available tissue conditioners on human fibroblasts grown in collagen gels. Finally, we measured the effects of these materials on the expression of cytokines in three-dimensional cultures by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assays. None of the tested vinyl esters had estrogenic activity. Vinyl octanoate and vinyl pivalate were the least cytotoxic of the eight tested vinyl esters. In the same vein, a prototype tissue conditioner containing vinyl octanoate had equivalent or weaker cytotoxicity and induction of cytokine expression than conventional materials.

Immobilization of simulated reducing agent at the surface of SiO2 fillers in dental composite resins

To reduce the leachability of reducing agents from composite resins, immobilization of a simulated reducing agent at the surface of SiO2 fillers was examined. SiO2 plates were immersed in 2% 3-aminopropyltriethoxy silane/ethanol solution, and then immersed in dimethyl sulfoxide with 0.25 wt% 4-dimethyl amino benzoic acid (DMABA), 2.0 wt% 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, and 0.5 wt% N-hydroxysuccinimide. Wide-scan spectrum of X-ray photoelectron spectroscopy did not detect carbon contamination. However, narrow scan detected an O=C-N peak at 399.8 eV, suggesting that DMABA could be immobilized on silane-coupled SiO2 plates. Further, surface plasmon resonance analysis indicated the adsorption of MMA at the surface of reducing agent-immobilized plate.

Trace phthalate and adipate esters contaminated in packaged food

A method for trace analysis of two plasticizers, di-2-ethylhexyl phthalate (DEHP) and di-2-ethylhexyl adipate (DEHA), contaminated in packaged curry paste were investigated by gas chromatography with flame ionization detector (GC-FID). Curry paste samples were extracted by ultrasonic and solid phase extraction using Florisil(R) cartridge. Analysis by the GC-FID system provided limits of detection for DEHA and DEHP at 12 and 25 microg L(- 1) and a linear dynamic range between 25 microg L(- 1) to 60 mg L(- 1) with a coefficient of determination (R(2)) greater than 0.99. High recoveries were obtained, ranged from 91 to 99% and 88 to 98% for DEHP and DEHA with RSD lower than 7 and 10% respectively. The method detection limit and limits of quantitation were ranged from 27 to 30 and 90 to 100 microg L(- 1). The analysis of curry paste samples showed concentrations of DEHP and DEHA in the range of 4.0 ng g(- 1) to 0.61 microg g(- 1).

Productive degradation of the biocide benzylbenzoate by Acinetobacter sp. strain AG1 isolated from the River Elbe

From water sampled in the River Elbe, we isolated a bacterial strain able to use the biocidal compound benzylbenzoate as its sole source of carbon and energy under aerobic conditions. This isolate was tentatively assigned to the genus Acinetobacter due to its morphological, physiological and partial SSU rRNA gene sequence properties. The productive bacterial degradation of the biocide benzylbenzoate was demonstrated, and the catabolic sequence was elucidated biochemically. Growth experiments, along with enzymatic studies, demonstrated that strain Acinetobacter sp. AG1 hydrolyzed benzylbenzoate enzymatically to yield benzylalcohol and benzoate. Benzylalcohol was further transformed to benzoate via benzaldehyde. Benzoate was subsequently channeled via catechol into the oxoadipate pathway for further degradation.

Estrogenic activity of phthalate esters by in vitro VTG assay using primary-cultured Xenopus hepatocytes

Estrogenic activity of phthalate esters in dental soft resins was evaluated with an amphibian system consisting of a vitellogenin (VTG)-detecting Enzyme-Linked Immunosorbent Assay and a primary-cultured hepatocyte assay using adult male Xenopus laevis. In particular, phthalate esters--Di-n-butyl phthalate (DBP), Butyl phthalyl butyl glycolate (BPBG), Benzyl butyl phthalate (BBP), and Benzyl benzoate (BB)--were investigated. Bisphenol A (BPA) was prepared for comparison with these chemicals, and 17beta-estradiol (E2) was used as a positive control. The chemicals were diluted in dimethyl sulfoxide (DMSO) to obtain final concentrations ranging from 10(-11) to 10(-4) mol/l. BPA induced estrogenic activity at a concentration of 1.1x10(-6) mol/l, while E2 showed at 4.1x10(-11) mol/l. DBP, BBP, BB, and BPBG showed no estrogenic activity at concentrations between 4x10(-7) mol/l and 1x10(-4) mol/l. The latter result indicated that these phthalate esters might be metabolically transformed into non-estrogenic substances in Xenopus hepatocytes. Furthermore, this study demonstrated that through in vitro metabolism assessment, the estrogenic activity of chemical substances could be directly detected in terms of VTG secretion in primary-cultured Xenopus hepatocytes.

[Estrogenic activity of ultraviolet absorbers and the related compounds]

The estrogenic activities of ultraviolet absorbers and their related compounds were investigated using MCF-7 cell proliferation assay. Nine of 33 chemicals (benzophenone, 2,4-dihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 4-hydroxybenzophenone, 3-(4-methylbenzylidene) camphor, ethyl 2-cyano-3,3-diphenylacrylate (etocrylene) and 2-ethylhexyl-2-cyano-3,3-diphenylacrylate (octocrylene)) were positive compared with the vehicle control. Benzhydrol, ethyl cinnamate and 2,2'-dihydroxy-4-methoxybenzophenone were weakly active. When each xenoestrogen was added to the cells along with ICI 182780, an estrogen receptor (ER) antagonist, the cell growth was reduced according to its doses. Therefore, the cell proliferation was suggested to generate through ER. Most of these chemicals were also positive using CHOOSER assay, a new method of testing estrogenic activity of xenoestrogen. Each xenoestrogen was also confirmed to bind to ERalpha and ERbeta using a human ER competitive binding assay against 17beta-estradiol. The concentration order of the strength of its inhibitory effect using both ERalpha and ERbeta was similar to that of MCF-7 cell proliferation assay, except for benzyl 4-hydroxybenzoate (B4HB). B4HB showed a stronger activity on CHOOSER assay and the competitive binding assay using both ERalpha and ERbeta, although there was no activity observed on MCF-7 cell proliferation assay. Our findings were to detect the estrogenic activity of etocrylene and octocrylene in vitro, in addition to confirming the activities of some ultraviolet absorbers as previously reported.

Temporary restorative resins using non-phthalate ester plasticizers

OBJECTIVE

This study examined temporary restorative resins that use non-phthalate ester plasticizers.

METHODS

Three non-phthalate plasticizers were tested: tri-ethyl citrate (TEC), tri-butyl citrate (TBC), and di-butyl sebacate (DBS). The experimental resins were compared with resins that use a phthalate ester plasticizer (di-butyl phthalate, DBP) and commercial products (Dura Seal, Plast Seal, and Fit Seal). For the experimental resins, the ratio of plasticizer to PMMA/MMA resin was varied from 30 to 60% (wt). The mechanical properties of the experimental resins were evaluated using a modified diametral compressive strength and the resistance to explorer insertion.

RESULTS

The strengths of the experimental resins with plasticizer concentrations ranging from 40 to 50% (TEC, TBC, and DBP) or from 30 to 40% (DBS), by weight, were equivalent to the strengths of commercial temporary restorative resins. A similar tendency was seen for the resistance to explorer insertion.

CONCLUSIONS

The results suggest that new temporary restorative resins can be prepared by choosing the appropriate proportions of resin monomer and non-phthalate ester plasticizer.

Transcriptional signatures of environmentally relevant exposures in normal human mammary epithelial cells: benzo[a]pyrene

Changes in gene expression in a panel of primary normal human mammary epithelial cell strains, developed from healthy breast tissue obtained at reduction mammoplasty from different donors, in response to benzo[a]pyrene exposure have been investigated. It was expected that both gene expression changes common to cell strains derived from different donors as well as inter-individual variation would be observed. Therefore, the strategy that has been adopted is to identify potentially important changes, or useful changes from a biomonitoring perspective, using gene-array technology and a small number of donors; then investigate selected transcription responses using a large number of tissue donors and a cheaper method of transcript detection (real-time polymerase chain reaction). Here we report results from four primary normal human mammary epithelial cell strains that were treated with benzo[a]pyrene in vitro for either 6 or 24 h. Transcription was monitored using high-density oligonucleotide arrays (Affymetrix HuGeneFL). Total RNA was used for the preparation of labeled targets that were hybridized to microarrays containing probes representing more than 6800 human genes and expressed sequence tags. Gene expression data were analyzed using the GeneChip software (MAS 5.0). Altered gene expression patterns were observed in response to benzo[a]pyrene in human mammary epithelial cell strains from different donors. Specifically, the dioxin inducible cytochrome P450 CYP1B1 was consistently induced in response to 6 and 24 h exposure to benzo[a]pyrene in cell strains from all four donors. Two other genes that were relatively consistently induced were IL1beta and MMP1. Less consistent changes in other metabolism genes (CYP1A1, CYP11B2, and NQO1) and certain cell cycle control genes GOS2 and AF1Q were also induced, while EGR1 was suppressed. Although no change in p53 transcription was observed, an accumulation of p53 protein was detected using antibodies. A similar accumulation of Waf1 (p21) was also observed using immunohistochemistry, this was expected since p53 is p21's transcription factor. Significant inter-individual variations in both the levels and patterns of gene expression were observed, in response to benzo[a]pyrene exposure. These studies provide a complementary approach to molecular epidemiology for the investigation of differential susceptibility to chemical carcinogens, and specifically polycyclic aromatic hydrocarbons.

Plasticizers in denture soft-lining materials: leaching and biodegradation

The leaching from soft lining materials into an aqueous buffer with the same esterase activity as that of saliva was compared to leaching into buffer without esterase activity. The buffer contained 0.1% non-ionic detergent, giving the medium a capacity to dissolve phthalates to the same degree as saliva. The hypothesis that esterase in the immersion medium will increase the rate of diffusion of plasticizers from denture soft-lining material was confirmed by the results. The average leaching of phthalates from 5.5 g of one of the materials was 4.5 mg kg(-1) d(-1) within the first 2 d and 1.1 mg kg(-1) d(-1) within the first 28 d. These levels may be compared to a LOAEL (lowest observed adverse effect level) of 52 mg kg(-1). It is concluded that an esterase activity, equivalent to that in saliva, in the immersion medium for soft lining materials increased the rate of diffusion of plasticizer from the materials. The measured levels of phthalates leaching from these materials might in vivo only be slightly less than 1/10 of the LOAEL given above.

Phthalates inhibit tamoxifen-induced apoptosis in MCF-7 human breast cancer cells

Environmental estrogens represent a class of compounds that can mimic the function or activity of the endogenous estrogen 17 -estradiol (E2). Phthalates including butyl benzyl phthalate (BBP), di(n-butyl) phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP) are used as plasticizers, and also widely used in food wraps and cosmetic formulations. Phthalates have been shown to mimic estrogen and are capable of binding to the estrogen receptor (ER). It has been demonstrated that estrogen promotes drug resistance to tamoxifen (TAM) in breast cancer. In order to further evaluate the potential role of the phthalates as environmental estrogens, the effect of phthalates was investigated on TAM-induced apoptosis in MCF-7 human breast cancer cells. Our results show that phthalates, BBP (100 M), DBP (10 M), and DEHP (10 M), significantly increased cell proliferation in MCF-7, but not in MDA-MB-231 cells. In addition, BBP, DBP, and DEHP mimicked estrogen in the inhibition of TAM-induced apoptosis in MCF-7 cells. Our data suggest that the inhibitory effect of phthalates on TAM-induced apoptosis involves an increase in intracellular Bcl-2 to Bax ratio. Given that the phthalates are widely used in cosmetics mainly for women, our findings that revealed the promoting effect of BBP, DBP, and DEHP on chemotherapeutic drug resistance to TAM in breast cancer may be of biological relevance.

Estrogenic and anticarcinogenic properties of kurarinone, a lavandulyl flavanone from the roots of Sophora flavescens

Kurarinone, a lavandulyl flavanone, was isolated from a polyphenolic extract of the roots of Sophora flavescens using fractionation guided by estrogenic activity, which was determined by recombinant yeast and Ishikawa Var-I bioassays. Kurarinone showed weak estrogenic activity both in the yeast screen and in the Ishikawa Var-I assay with EC(50) values of 4.6 and 1.66 microM, respectively. Furthermore, kurarinone was found to have potent cytotoxic activity (IC(50) value = 22.2 microM) against human MCF-7/6 breast cancer cells in the sulforhodamine-B assay.

Leachability of plasticizer and residual monomer from commercial temporary restorative resins

OBJECTIVES

This study was performed to determine the compositions of commercial temporary restorative resins and to evaluate the leachability of plasticizer and residual monomer from them.

METHODS

The chemicals in four commercial temporary restorative resins (Dura Seal, Fit Seal, Plast Seal Quick, and Poly Seal) were detected by GCMS and HPLC. The amounts of plasticizers and residual monomers that leached from cured resin samples immersed in ethanol for 1 h to 14 d were determined by HPLC.

RESULTS

Phthalate esters used as plasticizers contained 40-55 wt% either di-n-butyl phthalate (DBP) or butyl phthalyl butyl glycolate. The resin monomer included methyl methacrylate (MMA) or a mixture of MMA and 2-hydroxyethyl methacrylate (HEMA); 1,3-butanediol dimethacrylate was added as a cross-linking agent. Each resin contained 40-60 wt% monomer. The amounts of phthalate esters leached increased with immersion time up to 7 d, reaching 120-190 microg/mg, and did not change subsequently. The residual monomers leached gradually for up to 3d and did not change subsequently. The amount of leached residual monomer (MMA, HEMA) was 20-90 microg/mg after 3d storage. More than 50% of the leachable plasticizers and monomers were eluted from the cured resins within 24 and 3 h, respectively.

CONCLUSIONS

The amounts of leached plasticizers and residual monomers were extremely large compared with the concentrations of endocrine disrupters and their potentially genotoxic effects. Therefore, it is very important to evaluate the leachability of these compounds from temporary restorative resins.

Leaching of plasticizers from temporary denture soft lining materials

The loss of the plasticizers dibutylphthalate, butylphthalylbutyl glycolate, benzylbenzoate, methylsalicylate, and benzylsalicylate from four soft lining materials was measured. A 0.1% aqueous solution of triton X-100, reduced was used as immersion medium, since the solubility of plasticizer in this medium was close to that of saliva. The loss of plasticizer was monitored up to 30 d after mixing. For two of the materials, the average amount of leached dibutylphthalate within the first day exceeded the proposed tolerable daily intake (TDI) by about 11 and 32 times, respectively, for an average adult person. Similarly, for these two materials, the average daily amount within the first 30 d of leached dibutylphthalate was 2.2 and 6.6 times larger, respectively, than the TDI limit. The cumulative amount leached over 30 d for each of the four materials was 128-253 mg plasticizer g(-1). The results indicate the need for further biological evaluations of these products.