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Cytotoxicity of dental composite components and mercury compounds in pulmonary cells

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Cytotoxicity of dental composite components and mercury compounds in pulmonary cells

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Abstract

The cytotoxic potentials of the dental composite components triethyleneglycoldimethacrylate (TEGDMA) and 2-hydroxy-ethylmethacrylate (HEMA) as well as mercuric chloride (HgCl2) and methyl mercury chloride (MeHgCl) were investigated. Proliferating A549 and L2 cell monolayers were cultured in the absence or presence of composite components or mercurials. Twenty-four hours later the tetrazolium salt XTT (sodium 3'-[1-phenyl-aminocarbonyl)-3,4-tetrazolium]bis(4-methoxy-6-nitro)benzenesulphonic acid) was added. Formazan formation was quantified using a microtiter plate reader. EC50 values were obtained as half-maximum-effect concentrations from fitted curves. EC50 values were in A549 cells (mean values +/- standard deviation; n = 12; micromol/l); HEMA 8854+/-1882; TEGDMA 1821+/-529; HgCl2 41+/-7 and MeHgCl 27+/-3. EC50 values in L2 cells were: HEMA 191+/-28; TEGDMA 112+/-16; HgCl2 25+/-6 and MeHgCl 8+/-6. All tested substances induced a dose-dependent loss of viability in A549 and L2 cells after 24 h. The EC50 values of both mercurials were significantly (p < 0.05) lower compared to the values of both composite components. TEGDMA was about 5-fold (A549 cells) and about 2-fold (L2 cells) more toxic compared to HEMA. It is to be assumed that the risk of lung cell damage by dental composite components is even more unlikely.

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... Esterases originating in human saliva, water and other solvents in the dissolving of the polymer network caused by the formation of oligomers and monomers, lead to a softening of the organic matrix and easier penetration of the solvents. It has been determined that as a result of insufficient polymerisation with the effect of oral fluids, Bis-GMA (bisfenol-A glycidyl methacrylate), HEMA (Hidroxyethyl methacrylate), UDMA (urethane dimethacrylate) ve TEGDMA (triethylene glycol dimethacrylate) monomers are expressed from the organic matrix [28][29][30][31][32][33]. ...
... caused expression of inflammatory mediators in the pulp tissue [12,13,28,30,[33][34][35][36][37]. ...
... Due to hydrophyllic properties, TEGDMA can penetrate membranes and enter intra-cellular molecular reactions by mixing with oral tissues and it thus stimulates mitochondrial damage, prevents cell growth and total polar lipid synthesis, causes large DNA delesions (genotoxicity) in breast cells and it has been emphasised that it is 2-5 times more toxic than HEMA for lung cells. In addition, dermatitis and some allergic reactions (bronchospasm, urticaria etc) have been seen on the face and different body areas following treatment with resins containing TEGDMA [15,30,36,[40][41][42][54][55][56][57]. ...
... Anwendungsmöglichkeiten hat sich laufend erweitert. werden, deren Funktion darin besteht, die freie radikalische Polymerisation der Methacrylate in Gang zu setzen (Buonocore 1970; Eick et al. 2002) Viskosität zu verbessern (Vankerckhoven et al. 1982; Kehe et al. 2001). ...
... Mehrere Studien aus der Vergangenheit belegen, dass nach Exposition mit Komonomeren bei verschiedenen in-vitro-Zellkulturen sowohl antiproliferative als auch zytotoxische Effekte auftreten können (Kehe et al. 2001; Issa et al. 2004). Über die genauen Mechanismen, welche zur Induktion solcher Zellschäden führen, ist hingegen noch relativ wenig bekannt. ...
... Alle Versuche wurden erst nach Vorliegen eines konfluenten und homogenen Zellrasens durchgeführt.Geurtsen 1998; Reichl et al. 1999; Geurtsen 2000; Geurtsen et al. 2001). Bei zahlreichen in-vitro-Studien konnten für diese beiden Kompositkomponenten bereits zytotoxische Wirkungen nachgewiesen werden (Kehe et al. 2001; Emmler et al. 2002; Walther et al. 2002) Entzündungen hervorrufen (Goldberg et al. 1992; Nayebzadeh et al. 2000). Zudem haben Vergangenheit bereits häufiger genotoxische Wirkungen postuliert worden waren (Moore et al. 1988; Schweikl et al. 1998; Schweikl et al. 1999), erschien ein Vergleich regulatorischer Vorgänge nach einer Zellexposition mit diesen beiden Substanzen sinnvoll. ...
... In addition the present work found that, there was a highly significant decrease in the number of apoptotic cells induced by composite filling after 15min of filling insertion when compared with amalgam while after 1 week of insertion, they had proximately the same cytotoxic effect. The higher toxicity of amalgam than composite through one day of insertion was observed by Kehe et al [16] and Reichl et al [24] who found a higher toxicity of mercury compounds when compared with the composite components after 24 hr of exposure. This may be explained by the interaction of mercury with critical proteins in the cells [16,35]. ...
... The higher toxicity of amalgam than composite through one day of insertion was observed by Kehe et al [16] and Reichl et al [24] who found a higher toxicity of mercury compounds when compared with the composite components after 24 hr of exposure. This may be explained by the interaction of mercury with critical proteins in the cells [16,35]. An important reaction was the enzyme catalyzed reaction with reduced glutathione. ...
... After binding of metal ions (e.g., Hg) to glutathione, inorganic mercury can be detoxificated, leading however, to a decrease of intracellular glutathione level. Furthermore, the cellular energy metabolism can be impaired rapidly and can lead to cell death [16]. On the other hand, a lower number of apoptotic cells labeled with monoclonal anti CD95 antibody indicates that, the cells were died through intrinsic pathway rather than extrinsic pathway and this is in agreement with the results of Guo et al [12], Lefeuvre et al [18] and Shenker et al [31]. ...
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Background and Objective: There has been a growing concern of the potential health hazards imposed by use of dental filling materials that include toxic compounds. So this study was designed to evaluate the percentage of apoptotic cells in the epithelium of buccal and labial mucosa after applying amalgam and composite filling materials. Materials and Methods: The epithelial cells were stained with fluorescence dyes; ethidium bromide, propidium iodide and monoclonal antiFas-1 antibody then examined under fluorescent microscope. Results: The cytotoxicity of amalgam was decreased with aging time while that of composite was increased. On the other hand, using antifas-1 antibody, it was found that the apoptotic cells were died through mitochondrial pathway. [Nature and Science 2010;8(10):48-53]. (ISSN: 1545-0740).
... According toSpagnuolo et al. [126]the release of HEMA from polymerized dental adhesives ranges from 1.5 mmol/L to 8 mmol/L. In terms of cytotoxicity, HEMA has been found to be far less toxic, as compared to the bifunctional monomers[102,104,[106][107][108][109][110][111]116]. However, the TC50 concentration varied significantly with different cell lines and among the same types of cells obtained from different donors, ranging from 3.6 mmol/L to 10 mmol/L in various studies[63,112,117,126]. ...
... Of significant importance are also the long term effects of HEMA at subtoxic concentrations, which are able to disturb physiological pulp homeostasis and repair.The basic bifunctional resinous monomers BisGMA (2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane) and UDMA (urethane dimethacrylate) have been also studied for cytotoxicity and genotoxicity in a considerable number of studies. In general, the aromatic monomer BisGMA has been found to be slightly more cytotoxic than the aliphatic monomer UDMA[102,104,[106][107][108][109][110]112,116,152]. Despite the fact that BisGMA is not readily soluble in water and available only in small amounts in a hydrophilic environment it has been used as a representative acrylate compound for studying the toxic mechanisms of resin monomers on biological tissues[155,156]. ...
Article
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Resin-based dental restorative materials are extensively used today in dentistry. However, significant concerns still remain regarding their biocompatibility. For this reason, significant scientific effort has been focused on the determination of the molecular toxicology of substances released by these biomaterials, using several tools for risk assessment, including exposure assessment, hazard identification and dose-response analysis. These studies have shown that substances released by these materials can cause significant cytotoxic and genotoxic effects, leading to irreversible disturbance of basic cellular functions. The aim of this article is to review current knowledge related to dental composites' molecular toxicology and to give implications for possible improvements concerning their biocompatibility.
... Existen trabajos " in vivo " que aplican los sistemas adhesivos en contacto directo con el tejido pulpar con resultados variables (Hebling et al., 1999; Akimoto et al., 1999). Ahora, si bien es conocido el efecto citotóxico de estos materiales cuando se ponen en contacto directo con la pulpa dental, estudios recientes (Bouilaguet et al., 2000; Kehe et al., 2001) afirman que los mecanismos específicos de muerte celular no son del todo claro. El efecto citotóxico de los sistemas adhesivos dentales constituye por ello una limitación todavía no resuelta en este tipo de terapia odontológica. ...
... En este sentido algunos autores que han trabajado en dientes de primates o roedores, afirman que los sistemas adhesivos dentales estimulan la dentina terciaria reparadora en la exposición pulpar contribuyendo a formar puente dentinario (Akimoto et al., 1999; Cox et al., 1998; Murray et al., 2002; Kitasako et al., 2000químicos carcinogénicos o por radiaciones y constituyen el modelo experimental mas utilizado para evaluar la citotoxicidad a xenobióticos (Zucco, 1992). Las líneas celulares que se han utilizado en estudios experimentales de citotoxicidad de sistemas adhesivos dentales han sido de distinta naturaleza y origen, destacando entre ellos los fibroblastos de ratón 3T3 (Ratanasathien et al., 1995) y L929 (Kaga et al., 2001 ), las células odontoblástoides MDPC- 23 (), los monocitos-macrófagos humano THP-1 (Bouillaguet et al., 2000), las células neuronales (Kraemer et al., 1999) las células pulmonares A549 y L2 (Kehe et al., 2001), las células epiteliales de ratón (RK13) (Schuster et al., 2000),las células de pulpa humana (Spagnuolo et al., 2004a) y los fibroblastos humanos (Spagnuolo et al. 2004b) et al., 1999). adhesivos dentales actúan sobre las células es desconocido, aunque existe alguna __________________________________________________________________________________ evidencia según la cual los monómeros resinosos de los sistemas adhesivos dentales se incorporarían a la bicapa lipídica de la membrana celular, la cual sería solubilizada por los propios monómeros y provocaría la muerte (Fujisawa et al., 1998; Caughman et al., 1999; Shuster et al., 2000)(Kerr et al., 1972; Kerr, 2002). ...
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Tesis Univ. Granada. Departamento de Histología. Leída 23 de septiembre de 2005
... Ahora, si bien es conocido el efecto citotóxico de estos materiales cuando se ponen en contacto directo con la pulpa dental, estudios recientes afirman que los mecanismos específicos de muerte celular no son del todo claro. El efecto citotóxico de los adhesivos dentales constituye por ello, una limitación todavía no resuelta en este tipo de terapia odontológica (Bouilaguet et al., 1996; Kehe et al., 2001).Olio, 1991; Six et al., 2000; Souza et al., 2006).de nutrientes o de iones. ...
... En este trabajo y con el objeto de evaluar la citotoxicidad de los ionómeros de vidrio hemos utilizado como modelo experimental los fibroblastos gingivales humanos extraídos mediante biopsia. Las líneas celulares que se han utilizado en estudios experimentales de citotoxicidad de sistemas adhesivos dentales han sido de distinta naturaleza y origen, destacando entre ellas a los fibroblastos de ratón 3T3 (Ratanasathien et al., 1995), las células odontoblastoides MDPC-23 (), L929 (Kaga et al., 2001), células pulmonares A549 y L2 (Kehe et al., 2001), células de pulpa humana (Spagnuolo et al., 2004aSpagnuolo et al., , 2004b) y la línea celular monoblástica humana U937 (Cimpan et al., 2000; Rodríguez et al., 2008), 2009; Lekic et al., 1997; Ratanasathien et al., 1995) y, por otro lado, por la posibilidad de comparar los ensayos bioquímicos de citotoxicidad efectuados en dicho modelo (Issa et al., 2004) con los datos microanalíticos que resultan de aplicar la metodología microscópica microanalíticia cuantitativa desarrollada en el grupo de investigación en ingeniería tisular del departamento de Histología de Granada (Arrebola et al., 2005; Fernández Segura et al., 1997b;1999a; 1999b).de cultivo indica que la estabilidad de las membranas se ha visto dañada posiblemente por alteraciones oxidativas (Thomas et al., 1993; Yildiz et al., 1999). ...
... Notwithstanding the improvements Cortoss Ò offers, there remains a number of drawbacks associated with its use in skeletal applications including an excessively high exothermic reaction (63°C) relative to the threshold associated with thermal necrosis of healthy bone tissue (56°C) [24,25]. Many studies have also documented a cytotoxic potency of BIS-GMA and triethyleneglycol-dimethacrylate (TEG-DMA) [26][27][28][29][30]. These components have also been associated with decreased recruitment of leukocytes to sites of inflammation as well as inducing deletions in DNA sequences resulting in increased mutation frequency [31]. ...
Article
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Conventional polymethylmethacrylate (PMMA) cements and more recently Bisphenol-a-glycidyl dimethacrylate (BIS-GMA) composite cements are employed in procedures such as vertebroplasty. Unfortunately, such materials have inherent drawbacks including, a high curing exotherm, the incorporation of toxic components in their formulations, and critically, exhibit a modulus mismatch between cement and bone. The literature suggests that aluminium free, zinc based glass polyalkenoate cements (Zn-GPC) may be suitable alternative materials for consideration in such applications as vertebroplasty. This paper, examines one formulation of Zn-GPC and compares its strengths, modulus, and biocompatibility with three commercially available bone cements, Spineplex, Simplex P and Cortoss. The setting times indicate that the current formulation of Zn-GPC sets in a time unsuitable for clinical deployment. However during setting, the peak exotherm was recorded to be 33 degrees C, the lowest of all cements examined, and well below the threshold level for tissue necrosis to occur. The data obtained from mechanical testing shows the Zn-GPC has strengths of 63 MPa in compression and 30 MPa in biaxial flexure. Importantly these strengths remain stable with maturation; similar long term stability was exhibited by both Spineplex and Simplex P. Conversely, the strengths of Cortoss were observed to rapidly diminish with time, a cause for clinical concern. In addition to strengths, the modulus of each material was determined. Only the Zn-GPC exhibited a modulus similar to vertebral trabecular bone, with all commercial materials exhibiting excessively high moduli. Such data indicates that the use of Zn-GPC may reduce adjacent fractures. The final investigation used the well established simulated body fluid (SBF) method to examine the ability of each material to bond with bone. The results indicate that the Zn-GPC is capable of producing a bone like apatite layer at its surface within 24 h which increased in coverage and density up to 7 days. Conversely, Spineplex, and Simplex P exhibit no apatite layer formation, while Cortoss exhibits only minimal formation of an apatite layer after 7 days incubation in SBF. This paper shows that Zn-GPC, with optimised setting times, are suitable candidate materials for further development as bone cements.
... Cytotoxicity of amalgam in comparison to composites SCENIHR compare the toxicity of amalgam with composites. However, in most experiments, even inorganic mercury, which is much less toxic than mercury vapor (because inorganic mercury is not able to penetrate easily into the cells), was proven to be much more toxic than any composite compound: Mercury was shown to be 100-800-fold more toxic than composite components for human cells [110][111][112][113][114]. ...
Article
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It was claimed by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR)) in a report to the EU-Commission that "....no risks of adverse systemic effects exist and the current use of dental amalgam does not pose a risk of systemic disease..." [1, available from: http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_016.pdf]. SCENIHR disregarded the toxicology of mercury and did not include most important scientific studies in their review. But the real scientific data show that: (a) Dental amalgam is by far the main source of human total mercury body burden. This is proven by autopsy studies which found 2-12 times more mercury in body tissues of individuals with dental amalgam. Autopsy studies are the most valuable and most important studies for examining the amalgam-caused mercury body burden. (b) These autopsy studies have shown consistently that many individuals with amalgam have toxic levels of mercury in their brains or kidneys. (c) There is no correlation between mercury levels in blood or urine, and the levels in body tissues or the severity of clinical symptoms. SCENIHR only relied on levels in urine or blood. (d) The half-life of mercury in the brain can last from several years to decades, thus mercury accumulates over time of amalgam exposure in body tissues to toxic levels. However, SCENIHR state that the half-life of mercury in the body is only "20-90 days". (e) Mercury vapor is about ten times more toxic than lead on human neurons and with synergistic toxicity to other metals. (f) Most studies cited by SCENIHR which conclude that amalgam fillings are safe have severe methodical flaws.
... allergen and moderate cytotoxic compound222324. Although previously no genotoxic effect for HEMA was found [2,4,25], it tested positive in our umu-tests. ...
Article
The glass ionomer cement Vitrebond showed a clear genotoxic effect in the in vitro Mammalian Cell Gene Mutation Test (HPRT Test) with CHO cells as well as in the bacterial umu-test with Salmonella typhimurium TA1535/pSK1002. Both DMSO and Ham's F12 cell culture medium extracts according to ISO 10993-12 (Biological evaluation of medical devices-Part 12: sample preparation and reference materials, Geneva, Switzerland) exhibit a clear genotoxic effect in the umu-test. The effect is independent of the extraction volume in a range from 0.5 to 4 ml Ham's F12 cell culture medium. Subsequent extractions of Vitrebond showed no significant difference in the genotoxic response although weight loss and content of 2-hydroxyethyl-methacrylate dropped significantly. In vivo conditions of Vitrebond were simulated by extractions with artificial and collected human saliva. These extracts showed a clear genotoxic effect in the umu-test, even if only a few seconds of extraction time were applied. In conclusion, sample preparations for genotoxicity testing according to ISO 10993-12 reflect the in vivo conditions of Vitrebond applications. This seems to be mostly due to the hydrophilic nature of the genotoxic ingredients.
... It could be demonstrated that HEMA and TEGDMA were excreted via the urine [8] and that the kidney is the target organ for both composite components [9]. Cytotoxic responses to dental composite resins and their components have been described [10][11][12][13]. Genetical and/or iatrogenous damage of the (anti)oxidative system and/or increased oxidative stress in cells can lead to endogenous increase of H 2 O 2 and then some diseases can occur in human beings [14][15][16]. ...
Article
No data are available about (toxic) effects of dental materials administered in combination with H2O2 from dental bleaching compounds. The effect of dental composite components triethyleneglycol dimethacrylate (TEGDMA) and hydroxyethylmethacrylate (HEMA) as well as mercuric chloride (HgCl2) and methylmercury chloride (MeHgCl), each in combination with H2O2, was investigated on gluconeogenesis in kidney cells. From rats kidney tubules were prepared. Every 10 min up to 60 min 1-ml samples were drawn from the cell suspension for quantitating the glucose content. Glucose formation in controls was 3.5+/-0.3 nmol/mg.per min (mean+/-SEM, n = 21). Relative rates of glucose formation were obtained by expressing individual rates as percentage of the corresponding control. X-Y concentration curves (effective concentration, EC) of the substances were calculated by fitting a four-parametric sigmoid function to the relative rates of the glucose formation at various test concentrations. At the end of the incubation period cell viability was assessed by trypan blue exclusion. Cell viability decreased within the 60 min interval from 90% to approx. 80% (controls), < 25 (HEMA), < 20 (TEGDMA), < 20 (H2O2) < 10 (MeHgCl), and < 10 (HgCl2). Values of 50% effective concentration (EC50) were calculated from fitted curves. EC50 values were (mmol/l; mean+/-SEM; n = 4): HEMA, 17.2+/-2.8; TEGDMA, 1.9+/-0.2; H2O2 0.22+/-0.03, MeHgCl, 0.016+/-0.0005; and HgCl2, 0.0017+/-0.0005. No significant decrease of the EC50 values was found when kidney cells were exposed to HEMA, HgCl2, or MeHgCl in addition with H2O2 (1-100 mum), compared to those EC50 values of each compound without H2O2 addition. A significant decrease of the TEGDMA EC50 values to about 0.25 or 0.04 (mmol/l) was found when cells were exposed to TEGDMA in combination with H2O2 (75 or 100 mum), compared to that TEGDMA EC50 value without H2O2 addition. The addition of H2O2 (75 and 100 mum) resulted in a synergistic toxic effect of TEGDMA.
... Based on the HPLC results, it can be presumed that the cytotoxicity of the materials could be related to the amount of TEGDMA that was leached from the flowable composites compared with their non-flowable traditional composite. Indeed, TEGDMA has been reported to be toxic in different cell lines [6,10,22,27]. Moreover, the levels of TEGDMA that had leached from all the materials -Not detected except Admira and Z250 were above the ED 50 values (effective doses that decreased the number of viable cells to 50% of the control assays) for permanent 3T3 fibroblasts, although the levels of the other leached components did not reach the reported ED 50 values for these cells [6]. ...
Article
The release of components from dental composite into surrounding tissue may cause an adverse tissue reaction. Thus, this study investigated the cytotoxicity of three types of dental composites with their flowable derivatives and determined the compounds released from these materials by high-performance liquid chromatography (HPLC) analysis. Fifteen specimens from each composite (Admira, Z250, Tetric Ceram) with fifteen of their flowables (Admira Flow, Tetric Flow, Feltik Flow) were prepared in the form of discs and divided into two groups of 10 and 5 for each material. The first group (10 discs) was used to evaluate the cytotoxicity of the material on balb/c 3T3 fibroblasts by measuring cellular metabolic activity (3{4,5-dimethylthiazol-2-yl}-2,5-diphenyltetrazolium bromide [MTT] assay) relative to Teflon controls, while the second group (5 discs) was used to determine the leached components from each material into culture medium by HPLC analysis. The results revealed that Z250 and Tetric Ceram were less cytotoxic than their flowable derivatives. However, the ormocer, Admira, was significantly more cytotoxic than Admira Flow. Among the standard composites, Tetric Ceram was the least cytotoxic and Admira the most. Furthermore, Tetric flow was the most cytotoxic and Admira flow was significantly the least cytotoxic among the flowable materials tested. HPLC analysis revealed bisphenol A glycerolate dimethacrylate (bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) in the eluates of all the materials, while urethane dimethacrylate (UDMA) was present in all eluates except that of Feltik Flow. In conclusion, the flowable derivatives are more cytotoxic than the traditional composites whereas the ormocer Admira Flow is less cytotoxic than the Admira composite.
... Furthermore, salivary pseudocholinesterase (PCE) has been shown to preferentially degrade TEG-DMA and its derivatives and cholesterol esterase (CE) is reported to increase the breakdown of BIS-GMA components in composite dental resins [1]. Many studies have documented a cytotoxic potency of BIS-GMA and TEG-DMA [2][3][4][5][6][7][8]. Indeed, both resin components are reported to be highly cytotoxic in primary and immortal cell cultures, such as fibroblasts derived from the human pulp, the periodontal ligament or the gingiva [4][5][6][7][8]. ...
Article
The current study evaluated the effect of bisphenol A glycerolate dimethacrylate (BIS-GMA) and triethyleneglycol dimethacrylate (TEG-DMA) on female mouse fertility. Adult female mice were exposed to BIS-GMA or TEG-DMA (0, 25 and 100 microg/kg) intragastrically daily for 28 d and then mated with sexually mature untreated male mice and after mating their fertility was assessed. In females exposed to BIS-GMA at both doses significant increases in the total number of resorptions out of the total number of implantations were observed, with a significant increase in the number of animals with resorptions at the higher dose. Significant reductions in body weights and significant increases in ovary weights were also observed. Exposure to TEG-DMA at a dose of 100 microg/kg resulted in significant reductions in pregnancy rates and a significant increase in the total number of embryonal resorptions. Significant reductions in body and uterine weights were also observed in females exposed to TEG-DMA. The results suggest that both BIS-GMA and TEG-DMA have reproductive toxic effects in female mice.
... The cytotoxic potentials of the dental composite components TEGDMA and HEMA as well as mercuric chloride (HgCl2) and methyl mercury chloride (MeHgCl) were investigated by Kehe et al. (2001) and Reichl et al. (2001). Proliferating A549 (human bronchoalveolar carcinoma derived) and L2 cell (rat bronchoalveolar) monolayers were cultured in the absence or presence of composite components or mercurials. ...
... 28 The now for vertebroplasty available glass ceramic particle reinforced bis-GMA (bisphenol-a-glycidyl dimethacrylate) composite materials show a high degree of monomer conversion and stimulation of bone apposition at the interface, but the reaction is exothermic and several authors describe a possible cytotoxicity. 35,60,68 Also still experimental materials like Zn-GPC (zinc based glass polyalkenoate cement) with low heat evolution, bioactivity, adherence to the mineral phase of the bone and mechanical properties comparable to bone might be future alternative cements for kyphoplasty, 11 but further studies of all these materials will be necessary. ...
Article
Traumatic thoracolumbar spine fractures are frequently classified as burst fractures Magerl type A3. There still are many controversies regarding the treatment of this fracture. The therapeutic spectrum ranges from conservative to invasive operative methods with attendant morbidities. The minimal-invasive technique of kyphoplasty has established itself as a common treatment of osteoporotic vertebral compression fractures and is associated with a low complication rate. The aim of this study is to evaluate the functional and radiological results after kyphoplasty of traumatic thoracolumbar burst fractures. Patients with traumatic thoracolumbar fractures type A3.1, A3.2 and A3.3, who were treated with kyphoplasty, were included in this study. The clinical outcome was measured at follow up with a neurological assessment, the visual analogue pain scale (VAS), the Oswestry Disability Score (ODI) and the SF-36 Health Survey. The radiological measurements, performed on preoperative, postoperative and follow up radiographs, included the sagittal index, the wedge angle and the modified Cobb angle of Daniaux. 26 patients with 23 A3.1, one A3.2 and five A3.3 fractures were treated between 2004 and 2007, including five patients with multiple vertebral fractures. At follow up the Oswestry Disability Score (26.2%) and the SF-36 score (60.1%) assessed a moderately limitation of functional outcome and quality of life without any neurological deficits. Radiological measurements showed a postoperative height restoration and reduction of kyphosis, but at follow up a secondary loss of correction except in five cases. Six minor ventrocranial cement leakages without further clinical consequence were observed. The present study showed that kyphoplasty is a safe and feasible method for the treatment of burst fractures. It allowed the correction of the kyphosis, stabilisation of the facture, pain reduction and early mobilisation.
... The higher toxicity of BisGMA compared to the other residual monomers (TEGDMA, DMAEMA and HPMA) can be explained by BisGMA's higher liposolubility, which makes it able to enter cells more effectively [24]. The toxicity of TEGDMA might be explained by its ability to interact with cell membranes' lipid bilayer in a surfactant-like manner and/or cause lipid peroxidation [25]. TEGDMA has higher liposolubility than HEMA because HEMA's octanol/buffer section is about 20-fold lower than that of TEGDMA, In this way, hydrophobic TEGDMA is more able to penetrate cell membranes than HEMA and has more effective cellular properties [8,26,27]. ...
Article
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Objectives: The aim of the present study is to evaluate the released residual monomers from composite resins that contain different proportions of bioactive glass (BAG). Methods: Experimental resin composites were prepared by a resin matrix (50% BisGMA and 50% TEGDMA) and inorganic filler with BAG (5, 10 and 30%). Each resin composite was placed in the tooth cavity (n = 5). After polymerisation, samples were immediately immersed in 75% ethanol and 25% deionised water (6 ml) at 37 °C. Residual monomers (Bis-GMA, TEGDMA, HEMA and UDMA) that were eluted from the composites for 10 m, 1 h, 1 d, 7 d and 30 d were analysed by high-performance liquid chromatography (HPLC). The data were analysed with one-way ANOVA and Tukey HSD at a p < 0.05 significance level. Results: Among the time periods, the fastest released residual monomer was observed in the 10 m elution. The highest amount of released residual monomer from all groups (except the control group) was TEGDMA, whereas this was HEMA for the control group. The amounts of residual monomers eluted from BAG30 were significantly higher than other groups (p < 0.05). Conclusions: The release of the monomer increases in accordance with the increased BAG addition to the composite resins.
... The exposure time and interactions between dentinbonding components are important parameters depending on the type of cells studied. TEGDMA is about twofold to fivefold more toxic than HEMA for pulmonary cells [41]. Intracellular glutathione level is decreased by TEGDMA within the first 2–6 h after setting [18]. ...
Article
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In vitro and in vivo studies have clearly identified that some components of restorative composite resins, adhesives, and resin-modified glass ionomer cements are toxic. The mechanisms of cytotoxicity are related firstly to the short-term release of free monomers occurring during the monomer-polymer conversion. Secondly, long-term release of leachable substances is generated by erosion and degradation over time. In addition, ion release and proliferation of bacteria located at the interface between the restorative material and dental tissues are also implicated in the tissue response. Molecular mechanisms involve glutathione depletion and reactive oxygen species (ROS) production as key factors leading to pulp or gingival cell apoptosis. Experimental animal approaches substantiate the occurrence of allergic reactions. There is a large gap between the results published by research laboratories and clinical reports.
... Several studies have reported that uncured resin monomers such as HEMA, Bis-GMA and TEGDMA showed cytotoxicity against mammalian cell [42][43][44] . The experimental bonding agents used in the present study contained 2-HEMA and Bis-GMA. ...
Article
The purpose of this study was to evaluate pulpal healing and reparative dentin formation after 14 and 28 days in exposed rat pulp directly capped with an experimentally developed all-in-one adhesive containing surface reaction-type pre-reacted glass-ionomer (S-PRG) filler. The four experimental groups and the control group were compared using the Kruskal-Wallis test, followed by the Steel-Dwass post-hoc test to compare the histopathological score. The Mann-Whitney U test was used to compare the histopathological score at 14 and 28 days for each observation item. All experimental adhesives containing S-PRG fillers developed for direct pulp capping showed no pulpal inflammation. After 14 days, the experimental adhesives containing S-PRG fillers and the control group formed tertiary dentin around the exposed pulp. After 28 days, the experimental adhesives containing 13 and 27 wt% of S-PRG fillers formed dentin bridge equal to the control.
... Major criteria for success of the materials used in composite resins include good biocompatibility and no harmful effects on the teeth and surrounding tissues [34,35]. Despite advances in the field of resin composites, leaching of unpolymerized monomers or release of residual monomers after polymerization cause several problems in a living organism [34,36]. Such problems associated with composite materials sparked a debate on their safety. ...
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The aim of this study was to investigate the effect of different light curing units and light modes on the amount of residual monomers eluted from different resin-based composites. Initially, a total of 96 composite samples (N=24/group) were prepared from 3 bulk-fill composites with different characteristics and a nanohybrid composite using a mold (diameter: 5 mm, height: 4 mm). Then, each group was divided into 4 subgroups (n=6). Polymerization of the resin composites was performed using a halogen light source (Hilux 250), a 2nd generation LED device (Elipar DeepCure –S) and a 3rd generation LED device (Valo, standard and ultra modes). Samples were stored in 75% ethanol solution and residual monomers eluted in the solution were analyzed with HPLC after 1 day and 1 month. Monomer concentrations corresponding to the peak areas in chromatograms were calculated in ppm to obtain data for statistical analysis. The study data were analyzed using One Way ANOVA (p=0.05) and post-hoc Tukey tests. The type of the light-curing unit significantly affected the amount of residual monomer released in all composite groups (p<0.05). Except the Fill-Up composite groups, the least monomer elution was detected in the groups cured with Elipar DeepCure-S. Residual monomer amounts detected after 30 days were significantly increased in comparison to those eluted after 1 day in all groups. In light of these findings, it was concluded that the light curing units might have an impact on the monomer elution from different composites.
... En el área odontológica se emplean numerosos materiales, los cuales dependiendo de su aplicación estarán en contacto con diversos tejidos como mucosa, tejido gingival, tejido pulpar, tejido dental duro, tejido óseo, etc. Pero todos tienen en común que van a estar en contacto de una u otra forma con células vivas, de esta forma son similares los test empleados para operatoria y estética (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16), endodoncia (17)(18)(19)(20)(21), periodoncia y cirugía oral (22)(23)(24)(25)(26)(27)(28), ortodoncia (29), o rehabilitación (30)(31)(32)(33)(34)(35). En la mayoría de los trabajos revisados utilizan poblaciones celulares para evaluar la citotoxicidad, sin embargo en el estudio in vitro de los biomateriales dentales también se han utilizado organismos completos como las larvas de camarón brineshrimplarvae, mejor conocidas como Artemia salina (36,37). ...
Article
Background: The dental materials are subjected to various tests for consistency, bioactivity, and demonstrate that they can remain in the oral environment without producing an adverse response. Currently for this purpose worldwide are employed different techniques such as cell culture, techniques of molecular biology and the use of shrimp larvae (brineshrimplarvae) better known as Artemia salina. Objective: Characterize five dental materials using a cytotoxicity test with larval shrimp Artemia salina. Materials and methods: A cytotoxicity study was performed on samples of Titanium Type IV, Silicone Heavy, Auto-cured acrylic resin and photo-curing and Eugenolatousing the method of Artemia salina. Results: The cytotoxicity assay for Artemia Salina showed no viability foreugenolato because all the larvaes were eliminated, and other products showed biocompatibility in the following percentages. Titanium type IV 100%, the silicone 46%, acrylic 62% and resin 72%. Conclusions: The method of brine shrimp is a simple and economical method for studies of cytotoxicity, requires greater infrastructure technology, and combined with other techniques of cell biology can become as specific method as desired. There is viability for the artemiasalina larvae with type IV titanium of 100% and with eugenolato of 0%.
... It has been reported that mercury dichloride induces DNA damage even at low concentrations that do not show a cytotoxic effect, suggesting carcinogenic relevance for mercury. The proportion of salivary gland tumors among head and neck cancers is increasing and the parotid gland is mostly affected in such cases [9][10][11] . The specific factors involved in the increasing incidence of salivary gland tumors are not yet in the oral mucosa [12] . ...
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NNK (4-(methylnitrosamino)―1-(3-pyridyl)-1-butanone) is a major form of nitrosamine abundant in cigarette smoke and is a powerful carcinogen. Mercury is a major component of the amalgam that is widely used as dental filling material. Concurrent exposure to these two agents may result in their interaction and alter their carcinogenic potential. The present study used an immortalized human epithelial cell system that allows continuous exposure to potential carcinogens, in an attempt to elaborate the carcinogenic potential of mercury and NNK in humans. Cytotoxicity of mercury chloride and NNK was measured by an MTT assay. Parameters of neoplastic cellular transformation such as cell saturation density, soft-agar colony formation, and cell aggregation were analyzed to examine the carcinogenic potential of mercury chloride and NNK. The study showed that exposure to mercury chloride with NNK resulted in increased soft agar colony formation and cell aggregation. ROS generation by mercury chloride was further enhanced by treatment with NNK. The apoptosis that was observed following mercury chloride exposure was further increased upon co-treatment with NNK. The interaction between these two agents was also observed in cytokine mRNA induction. In the present study, mercury alone did not seem to pose a significant threat as a carcinogen, but it may have potential to enhance the carcinogenic potential of a known carcinogen from cigarette smoke. The present study provides valuable data regarding the evaluation of potential carcinogenic risk of mercury chloride and NNK on concurrent exposure.
... Resin composites are used in clinical dentistry not only as restorative materials but also as dentin adhesives or as luting agents for inlays, crowns, veneers, and orthodontic brackets. 1 With the increasing use of these resin-based restorative materials over the past decade, public interest in the local and systemic adverse effects caused by these dental materials has increased. Each resin-based material releases several components into the oral environment; these substances may be systemically distributed and could cause adverse systemic effects. 2 The hypothesis of this study was that the chemical composition of various composites may affect component release and their cytotoxic properties. ...
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To investigate the toxicity of 4 types of resin-based dental composites with different compositions and to determine the components released from them using high-performance liquid chromatography (HPLC). Resin composite disks (Z100, Solitaire 2, Filtek P60, and Synergy) were prepared, and cytotoxicity was tested on Balb/C 3T3 fibroblasts. In the first part of the study, cells were exposed to the composites for 72 hours (direct method), and in the second part to ethanolic extracts of the composites for 24 hours (indirect method), both at 37 degrees C. Cell viability was then determined by the MTT (3[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) method. The dental composites and their ethanolic extracts had adverse effects on the viability of Balb/C 3T3 fibroblasts. ANOVA revealed highly significant differences in cytotoxicity between the groups (P <.001) for both the direct and indirect methods. Follow-up comparison by Tukey test (alpha = .05) showed that Synergy was significantly less toxic than the other resin composites and Solitaire 2 was significantly more cytotoxic when the materials were tested by the direct method. However, using the indirect method, the extract of Synergy was significantly more toxic than all the other extracts. Bis-GMA, TEGDMA, UDMA, bis-EMA, and bisphenol A were detected by HPLC analysis; however, their presence and concentrations varied from one composite to another. The cytotoxicity level of resin-based dental composites depends on their chemical composition, leaching medium, and the amount and type of the components that can be extracted from the materials.
... The underlying concept of the XTT cell proliferation assay is that metabolically active mitochondrial dehydrogenase enzymes reduce the yellow, water-soluble tetrazolium salt XTT to orange, soluble compounds of formazan. 25 This is measured by their absorbance at 450 nm. For these assays, cells cultured under normal conditions (monolayer) without any material were used as the control. ...
Article
Statement of problem: Although the physical and mechanical properties of hydroxyapatite-filled dental restorative composite resins have been examined, the biocompatibility of these materials has not been studied in detail. Purpose: The purpose of this in vitro study was to analyze the toxicity of acrylate-based restorative composite resins filled with hydroxyapatite and a silica/hydroxyapatite combination. Material and methods: Five different restorative materials based on bisphenol A-glycidyl methacrylate (bis-GMA) and tri-ethylene glycol dimethacrylate (TEGDMA) were developed: unfilled (H0), hydroxyapatite-filled (H30, H50), and silica/hydroxyapatite-filled (SH30, SH50) composite resins. These were tested for in vitro cytotoxicity by using human bone marrow mesenchymal stromal cells. Surface morphology, elemental composition, and functional groups were determined by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), and Fourier-transformed infrared spectroscopy (FTIR). The spectra normalization, baseline corrections, and peak integration were carried out by OPUS v4.0 software. Results: Both in vitro cytotoxicity results and SEM analysis indicated that the composite resins developed were nontoxic and supported cell adherence. Elemental analysis with EDX revealed the presence of carbon, oxygen, calcium, silicon, and gold, while the presence of methacrylate, hydroxyl, and methylene functional groups was confirmed through FTIR analysis. Conclusions: The characterization and compatibility studies showed that these hydroxyapatite-filled and silica/hydroxyapatite-filled bis-GMA/TEGDMA-based restorative composite resins are nontoxic to human bone marrow mesenchymal stromal cells and show a favorable biologic response, making them potential biomaterials.
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Oral and mucosal adverse reactions to resin-based dental materials have been reported. Numerous studies have examined thebiocompatibility of restorative dental materials and their components, and a wide range of test systems for the evaluation of the biological effects of these materials have been developed. This article reviews the biological aspects of resin-based dental materials and discusses the conventional as well as the new techniques used for biocompatibility assessment of dental materials.
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Glass ionomer cements are widely used in dentistry as restorative materials and adhesives for composite restorations. However, the results of genotoxicity studies using these materials are inconclusive in literature. The goal of this study was to examine the genotoxic and cytotoxic potential of three different glass ionomer cements available commercially (Ketac Cem, Ketac Molar and Vitrebond) by the single cell gel (comet) assay and trypan blue exclusion test, respectively. For this, such materials were exposed to Chinese hamster ovary (CHO) cells in vitro for 1 h at 37( composite function)C. Data were assessed by Kruskall-Wallis nonparametric test. The results showed that the powder from Ketac Molar displayed genotoxicity only in the maximum concentration evaluated (100 microg/mL). In the same way, the liquid from Vitrebond at 0.1% dilution caused an increase of DNA injury. Significant differences (P<0.05) in cytotoxicity provoked by all powders tested of glass ionomer cements were observed for exposure at 1,000 microg/mL concentration. With respect to liquids of glass ionomer cements evaluated, the major toxic effect on cell viability was produced at 10%, beginning at the dilution of 0.5% for Vitrebond. Taken together, we conclude that some components of glass ionomer cements show both genotoxic and cytotoxic effects.
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This study investigated the effect of extracts of different composites, glass ionomer cement (GIC)s and compomers on the viability of brine shrimp larvae. Ethanolic extracts of four dental composites (Z-100; Solitaire 2; Filtek P60 and Synergy), a conventional GIC (Ketac-Fil), a resin-modified glass ionomer cement (Vitremer), two compomers (F2000; Dyract AP), and a flowable compomer (Dyract Flow) were prepared from each material. Following evaporation of the ethanol, the extracts were resuspended in distilled water, which was then used to test the effects on the viability of brine shrimp larvae. For the composites, the extract of Synergy was the least toxic (88% viability) followed by the extracts of Solitaire 2, Z100 and P60 (75%, 67.5% and 50% viability, respectively). One-way ANOVA revealed highly significant differences between the resin composite materials (p<0.001). Follow-up comparison between the composite groups by Tukey's pairwise multiple-comparison test (alpha =0.05) showed that the extract of Synergy was significantly less toxic than the extracts of all the other materials except that of Solitaire 2. The compomers showed 100% lethality, while the percentage of viable larvae for the extracts of Ketac-Fil, and Vitremer were 32.3%, and 37.0%, respectively. One-way ANOVA revealed highly significant differences between the groups of materials (p<0.001). Follow-up comparison between the groups by Tukey's test (alpha = 0.05) showed that the toxic effect of the extracts of the compomers were significantly greater than that of Ketac-Fil, and Vitremer. The differences in the toxic effects of Vitremer and Ketac-Fil were not statistically significant. In conclusion, the toxicity of composite materials varied according to their chemical composition. Compomers were the most lethal materials to brine shrimp larvae followed by GICs and then composites.
Article
Toxicity potentiation of two monomers [bisphenol-A-glycidyldimethacrylate (BisGMA) and urethanedimethacrylate (UDMA)] as well as two comonomers [triethyleneglycoldimethacrylate (TEGDMA) and 2-hydroxyethylmethacrylate (HEMA)], each in combination with H(2)O(2), was investigated on the viability on human gingival fibroblasts (HGF) and human pulpal fibroblasts (HPF). The applied concentration of H(2)O(2) was 0.06 or 0.1 mmol/l, respectively, corresponding to the EC(0) of H(2)O(2) in HGF or HPF. The cell viability was assessed by the XTT test. From this test the half maximum effect concentrations (EC(50)) were calculated from fitted sigmoidale curves. EC(50) values were (HGF; mmol/l; mean +/- s.e.m.; n = 5): HEMA 11.9 +/- 0.9, TEGDMA 3.7 +/- 0.3, H(2)O(2) 0.36 +/- 0.04, UDMA 0.27 +/- 0.08, and BisGMA 0.11 +/- 0.03. No significant (P < 0.05) differences in the EC(50) values were observed when HGF was exposed to substances, as compared to HPF. No significant decrease of the EC(50) values was found when HGF or HPF, respectively, was exposed to HEMA or BisGMA in addition with H(2)O(2) up to the concentration of 0.1 mmol/l, as compared to those EC(50) values of each compound without H(2)O(2) addition. A significant decrease of the TEGDMA EC(50) value from 3.7 to 2.1 or 0.4 mmol/l, respectively, was found when cells were exposed to TEGDMA in combination with H(2)O(2) (0.06 or 0.1 mmol/l), as compared to that TEGDMA EC(50) value without H(2)O(2) addition. A significant decrease of the UDMA EC(50) value from 0.27 to 0.11 or 0.08 mmol/l, respectively, was found when HGF or HPF was exposed to UDMA in combination with H(2)O(2) (0.06 or 0.1 mmol/l), as compared to that UDMA EC(50) value without H(2)O(2) addition. The addition of H(2)O(2) (0.06 or 0.1 mmol/l) resulted in a toxicity potentiation of TEGDMA and UDMA, but not of HEMA and BisGMA, on HGF or HPF.
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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. 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. 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. 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.
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Amalgam is still one of the most frequently used dental filling materials. However, the possible adverse effects especially that of the mercuric component have led to continued controversy. Considering that mercury may be released from amalgam fillings into the oral cavity and also reach the circulating blood after absorption and resorption, it eventually may contribute to tumorigenesis in a variety of target cells. The present investigation focuses on genotoxic effects below a cytotoxic dose level of mercuric dichloride (HgCl(2)) in human samples of salivary glands and lymphocytes to elucidate a possible role in tumor initiation. DNA migration due to single strand breaks, alkali labile sites and incomplete excision repair was quantified with the aid of the single cell microgel electrophoresis (Comet) assay. The concepts of Olive Tail Moment, percentage of DNA in the Tail and Tail Length were used as measures of DNA damage. To control for cytotoxic effects, the trypan blue exclusion test was applied. Human samples of the parotid salivary gland and lymphocytes of ten donors were exposed to HgCl(2)concentrations from 1 to 50 microM. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and dimethyl sulfoxide (DMSO) served as controls. Increasing dose-dependent DNA migration could be demonstrated after exposure to HgCl(2) in cells of the salivary glands and lymphocytes. In both cell types a significant increase in DNA migration could be shown starting from HgCl(2)concentrations of 5 microM in comparison to the negative control. The viability of the cell systems was not affected except at the highest concentration (50 microM) tested. These data indicate genotoxic effects of mercuric dichloride in human salivary glands and lymphocytes at concentrations not leading to cytotoxic effects or cell death. Consequently, a contributory role in oral salivary gland tumor initiation warrants further investigation.
Article
Unpolymerized resin (co)monomers or mercury (Hg) can be released from restorative dental materials (e.g. composites and amalgam). They can diffuse into the tooth pulp or the gingiva. They can also reach the gingiva and organs by the circulating blood after the uptake from swallowed saliva. The cytotoxicity of dental composite components hydroxyethylmethacrylate (HEMA), triethyleneglycoldimethacrylate (TEGDMA), urethanedimethacrylate (UDMA), and bisglycidylmethacrylate (Bis-GMA) as well as the amalgam component Hg2+ (as HgCl2) and methyl mercury chloride (MeHgCl) was investigated on human gingival fibroblasts (HGFs) at two time intervals. To test the cytotoxicity of substances, the bromodeoxyuridine (BrdU) assay and the lactate dehydrogenase (LDH) assay were used. The test substances were added in various concentrations and cells were incubated for 24 or 48 h. The EC50 values were obtained as half-maximum-effect concentrations from fitted curves. Following EC50 values were found [BrdU: mean (mmol/l); SEM in parentheses; n=12]: (24 h/48 h) HEMA 8.860 (0.440)/6.600(0.630), TEGDMA 1.810(0.130)/1.220(0.130), UDMA 0.120(0.010)/0.140(0.010), BisGMA 0.060(0.004)/0.040(0.002), HgCl2 0.015(0.001)/0.050(0.006), and MeHgCl 0.004(0.001)/0.005(0.001). Following EC50 values were found [LDH: mean (mmol/l); SEM in parentheses; n=12]: (24 h/48 h) HEMA 9.490(0.300)/7.890(1.230), TEGDMA 2.300(0.470)/1.950(0.310), UDMA 0.200(0.007)/0.100(0.007), BisGMA 0.070(0.005)/0.100(0.002), and MeHgCl 0.014(0.006)/0.010(0.003). In both assays, the following range of increased toxicity was found for composite components (24 and 48 h): HEMA BrdU assay, Hg2+ was about fourfold less toxic than MeHgCl but Hg2+ was about fourfold more toxic than BisGMA. In the BrdU test, a significantly (P2+ at 48 h, compared to the 24 h Hg2+-exposure. A time depending decreased toxicity was observed only for Hg2+ which can then reach the toxic level of BisGMA.
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Mercury is a widespread environmental and industrial pollutant that induces serious adverse effects in both humans and the environment. However, the toxicities and its mechanisms have not been fully elucidated. Among the proposed mechanisms of biological toxicities, the intracellular level of thiol group (-SH) and oxidative stress have been widely studied. In this study, production of reactive oxygen species (ROS) by mercuric chloride (2, 4, 6, and 8 ppm as of mercury) was investigated in cultured human bronchial epithelial cells (BEAS-2B cell line). Exposure of cultured cells to mercuric chloride led to cell death, ROS increase, and cytosolic caspase-3 activation. The ROS increase was related to the decreased level of GSH. Chromatin condensation evaluated by 4',6-diamidino-2-phenylindole (DAPI) staining were also shown in mercury-treated cells and this suggest the apoptotic process of cells by mercuric chloride.
Article
In order to test the hypothesis that released dental restorative materials can reach toxic levels in human oral tissues, the cytotoxicities of the resin-based dental (co)monomers hydroxyethylmethacrylate (HEMA), triethyleneglycoldimethacrylate (TEGDMA), urethanedimethacrylate (UDMA), and bisglycidylmethacrylate (BisGMA) compared with methyl mercury chloride (MeHgCl) and the amalgam component mercuric chloride (HgCl2) were investigated on human gingival fibroblasts (HGF) using two different test systems: (1) the modified XTT-test and (2) the modified H 33342 staining assay. The HGF were exposed to various concentrations of the test-substances in all test systems for 24 h. All tested (co)monomers and mercury compounds significantly (P50 values in the XTT assay were obtained as half-maximum-effect concentrations from fitted curves. Following EC50 values were found (mean [mmol/l]; s.e.m. in parentheses; n=12; * significantly different to HEMA): HEMA 11.530 (0.600); TEGDMA* 3.460 (0.200); UDMA* 0.106 (0.005); BisGMA* 0.087 (0.001); HgCl2* 0.013 (0.001); MeHgCl* 0.005 (0.001). Following relative toxicities were found: HEMA 1; TEGDMA 3; UDMA 109; BisGMA 133; HgCl2 887; MeHgCl 2306. A significant (P2 2 induced mainly necrotic cell death. The results of this study indicate that resin composite components have a lower toxicity than mercury from amalgam in HGF. HEMA, BisGMA, UDMA, and HgCl2 induced mainly necrosis, but it is rather unlikely that eluted substances (solely) can reach concentrations, which might induce necrotic cell death in the human physiological situation, indicating that other (additional) factors may be involved in the induction of tissue (pulp) inflammation effects after dental restauration.
Article
Previous in vivo studies have shown that the comonomers triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) from dental materials can be metabolised to CO(2) by two postulated pathways: an epoxide and a valine pathway. In the epoxide pathway the formation of pyruvate is postulated and in valine pathway the formation of l-malate. The aim of this investigation was to quantify the formation of the intermediates pyruvate and l-malate to show which pathway may be preferred in A549 cells. Therefore A549 cells were incubated with TEGDMA or HEMA (with a tracer dose 14C-TEGDMA or 14C-HEMA) and afterwards 14C-TEGDMA or 14C-HEMA, 14C-methacrylate, 14C-l-malate and 14C-pyruvate were identified and quantified by thin layer chromatography at different time intervals from the extracellular and intracellular fluid. Our results show that in the metabolism of both comonomers more 14C-pyruvate was formed compared to 14C-l-malate for 14C-HEMA metabolisation during 0.5 up to 6h after 14C-HEMA exposure and for 14C-TEGDMA metabolisation >4h after 14C-TEGDMA exposure. Therefore the epoxide pathway with formation of the epoxy-intermediate 2,3-epoxymethacrylic acid is the main route of metabolisation of HEMA and TEGDMA.
Article
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International rules must be followed for testing biosecurity in dental materials. A new brand of restorative material appeared in the market and regulations indicated that it should be tested for toxicity. The aim of this study was to determine the 90-day sub chronic toxicity of one triethylene glycol dimethacrylate containing composite (MEDENTAL Light-Cure Composite™) orally administered to rats according to Organization for Economic Co-Operation and Development no. 48 guidelines and the requirements specified in the ISO 10993-11. Wistar rats ate the polymerized composite during 90 days and were observed to determine changes in their behavior, eye and skin signs and other attitudes such as aggressiveness, posture, walking and response to handling. After 90 days were sacrificed to ascertain blood alterations, we did special hematological tests and assessed microscopic slides from 33 different organs. We recorded no significant changes in clinical behavior of the animals. Microscopic review of the H&E stained slides obtained from the analyzed organs showed no abnormal inflammatory or cytological changes and all hematological special tests were within normal limits. Results of this study show that under our experimental conditions the MEDENTAL Light-Cure Composite™ does not produce inflammatory or cytological changes suggestive of toxicity. Key words:Dental materials, composite resin, toxicity, inflammation, TEGDMA.
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The main aim of this study was to perform an integrative review on the release of bisphenol A (BPA) from resin‐matrix composites and potential toxic effects. A bibliographic search was performed on the PubMed platform using the following keywords: “Bisphenol A" OR “BPA” AND “resin composite” OR “composite resin” AND “toxicity” OR “cytotoxicity” OR “release”. Inclusion criteria involved in vitro and in vivo studies on the release and toxicity of BPA. Results highlighted the release of BPA from resin‐matrix composites due to insufficient polymerization and/or degradation of the polymeric matrix. BPA is part of the organic matrix of resin‐matrix composites and may be hydrolysed in human saliva, although studies report that low doses might not be detected by traditional chemical analysis. Studies exposing zebrafish embryos to different concentrations of Bis‐GMA, showed 55% mortality at 10 μM Bis‐GMA while 30% mortality was recorded at 1 μM Bis‐GMA. In patients, a BPA concentration of around 2.09 × 10−2 μg/ml was found in the saliva after placement of lingual orthodontic retainers with resin‐matrix composites. Also, the BPA molecule can be swallowed and absorbed by the oral/gastrointestinal mucosa, which might result in systemic toxicity. The degradation of resin‐matrix composites and release of BPA in oral environment are dependent on the organic matrix content and on the polymerization method. A increased release of BPA can lead to the absorption into oral and gastrointestinal mucosa with high risks of local and systemic toxicity. https://onlinelibrary.wiley.com/doi/10.1002/jbm.b.34843
Thesis
Amaç: Bu çalışmanın amacı farklı ışık kaynakları ile farklı kalınlıkta polimerize edilmiş ve yapay yaşlandırma işlemine maruz bırakılmış 5 farklı bulk-fill kompozit rezinden (Filtek Bulk Fill Flowable, Sonic Fill 2, Surefil SDR Flow, Venus Bulk Fill, Tetric N-Ceram Bulk Fill) ve 1 adet konvansiyonel kompozit rezinden (Filtek Z250) açığa çıkan monomer miktarının incelenmesi ve elde edilen monomerlerin kompozit materyaller arasında karşılaştırılmasıdır. Materyal ve Metot: LED (Light Emitting Diode) ya da QTH (Quartz Tungsten Halogen) ışık cihazı kullanılarak 5 mm çapında hem 2 mm hem de 4 mm kalınlıkta kompozit diskler hazırlandı. Üretilen kompozit örnekler %75 etanol/su solüsyonu içeren cam viyallere aktarıldı ve sonra cam viyaller iki gruba ayrıldı. Kontrol grubunda olan cam viyaller üç farklı zaman diliminde (0-1 gün, 1-3 gün ve 3-7 gün) 37 0C'de etüvde bekletildi. Termal siklus grubunda bulunan örnekler kontrol grubunda belirlenen üç zaman dilimine denk gelecek süre kadar termal siklusa maruz bırakıldı (0-1 gün: 1500; 1-3 gün: 3000; 3-7 gün: 6000). Her bir zaman diliminde alınan ekstraksiyon örneklerindeki monomerler HPLC cihazında ölçüldü. Elde edilen veriler tekrarlanan ölçümlü varyans analizi ve tukey çoklu karşılaştırma testi (p<0,05) ile analiz edildi. Bulgular: Bis-GMA, TEGDMA, UDMA ve Bis-EMA monomerleri sırasıyla Tetric N Ceram Bulk Fill, Sonic Fill 2, SDR ve Venus Bulk Fill kompozitlerinden en fazla miktarda açığa çıktı. 1. gün en yüksek seviyede monomer elüsyona uğrarken, zamanla monomer elüsyonunun azaldığı tespit edildi. Termal siklus uygulaması artık monomer elüsyonunu artırdı ve bazı zaman periyotlarında monomerlerin sitotoksik düzeye ulaştığı belirlendi. İlk 24 saat hariç ışık kaynakları arasında anlamlı bir farklılık görülmedi. Artan kalınlıkla birlikte açığa çıkan Bis-GMA, TEGDMA, Bis-EMA monomer miktarındaki en fazla artış Sonic Fill 2 kompozitte, UDMA monomer miktarındaki en fazla artış ise Filtek Z250 kompozitinde tespit edildi. Sonuç: Monomer elüsyonunun büyük bir kısmı ilk 24 saatte gerçekleşti ve zamanla açığa çıkan monomer miktarı azaldı. Kompozit örneklerin kalınlığı 2 mm’den 4 mm’ye çıkartıldığı zaman açığa çıkan monomer miktarının oranı kullanılan kompozite göre değişkenlik gösterdi. Termal siklus işleminden sonra elde edilen monomer miktarı kompozit materyalin kalınlığı ve yapısına bağlıydı. Farklı ışık kaynakları kompozitlerden açığa çıkan monomer miktarını genellikle etkilemedi. Anahtar Kelimeler: Artık monomer, Bulk-fill kompozit, HPLC, Termal siklus
Article
Resin‐based biomaterials are widely used in medical and dental treatment, and both clinicians and patients are exposed to the materials. The knowledge of toxicity is mainly based on in vitro studies at exposure concentrations that induce cell death. However, severe cell damage and cell‐death signaling may overshadow essential cellular events caused by a possible toxicant. For dental resins, the knowledge of interaction with living cells at more clinical relevant exposure doses is sparse. 2‐Hydroxyethylmethacrylate (HEMA) is a commonly used monomer in dental resins. Measuring cellular adaptation to HEMA at concentrations that did not reduce cell viability were the main focus of the current study. Stable isotope labeling with amino acids in cell culture (SILAC) was used to measure proteome changes in cultured THP‐1 cells exposed to HEMA. Western blotting verified the results. Cells exposed to HEMA increased their level of several cytoprotective proteins. The observed adaptation is compatible with increased oxidative burden caused by GSH‐depletion and the electrophilic characteristic of HEMA. The present approach to analyzing the toxic potential of HEMA yielded information on interactions with living cells is not previously reported. This detailed information is of great value to make better predictions of possible side effects in the clinic. This article is protected by copyright. All rights reserved.
Chapter
All dental amalgam fillings contain approximately 50 % elemental mercury by weight. Concerns about health risks due to continual emissions of mercury vapor from this tooth restorative material have been addressed by dentists, scientists, and government authorities worldwide and have resulted in a range of recommended practices and regulations. By reviewing articles collected by a literature search of the International Academy of Oral Medicine and Toxicology (IAOMT) database and the PubMed database, we identify health risks associated with dental mercury amalgam. We present the science of potential harm as applicable to the general population, pregnant women, fetuses, children, and dental professionals. We specifically address genetic predispositions, mercury allergies, Alzheimer’s disease, multiple sclerosis, amyotrophic lateral sclerosis, and other health conditions pertinent to dental mercury exposure. We conclude that reviews and studies of dental amalgam mercury risk should assess biocompatibility with special consideration for all populations and all risk factors.
Article
With rapid industrialization, China is now facing great challenges in heavy metal contamination in the environment. Human exposure to heavy metals through air, water and food commonly involves a mixture consisting of multiple heavy metals. In this study, eight common heavy metals (Pb, Cd, Hg, Cu, Zn, Mn, Cr, Ni) that cause environmental contamination were selected to investigate the combined toxicity of different heavy metal mixtures in HL7702 cells. Toxicity (24 h LC50 ) of each individual metal on the cells ranked Hg > Cr = Cd > Cu > Zn > Ni > Mn > Pb; toxicity of the different mixtures ranked: M5 > M3PbHgCd > M5+Mn > M5+Cu > M2CdNi > M4A > M8-Mn > M8 > M5+Zn > M4B > M8-Cr > M8-Zn > M8-Cu > M8-Pb > M8-Cd > M8-Hg > M8-Ni > M3PbHgNi > M3CuZnMn. The cytotoxicity data of individual metals were successfully used to build the additive models of two- to eight-component metal mixtures. The comparison between additive model and combination model or partly additive model was useful to evaluate the combined effects in mixture. Synergistic, antagonistic or additive effects of the toxicity were observed in different mixtures. These results suggest that the combined effects should be considered in the risk assessment of heavy metal co-exposure, and more comprehensive investigations on the combined effects of different heavy metal mixtures are needed in the future. Copyright © 2016 John Wiley & Sons, Ltd.
Chapter
Biocompatibility testing of novel biomaterials employs a wide spectrum of various in vivo and in vitro tests. As in vitro testing can respond to the urgent need for screening the huge amount of new materials produced nowadays, the present chapter is focusing on the cell-based assay systems used for such tests and introduces briefly the most common in vitro methods for the evaluation of the cell response to biomaterials, with an emphasis on testing of cell death and cell proliferation. Advantages and disadvantages of these methods, some hints for the setup of the tests, as well as, novel trends in assay methodologies are also here discussed.
Article
Objectives: The aim of this study was to evaluate the cytotoxicity of four low-shrink composites with new monomer technology on the bovine dental pulp-derived cells (bDPCs). Materials and methods: Ten samples were prepared for each group composites, and the samples were immersed in 7 mL of culture medium for 72 h at 37°C to extract residual monomer or cytotoxic substances. The culture medium containing the material extracts was sterile filtered for use on the cell cultures. Materials were incubated in medium with serum for 72 h. bDPCs were maintained in a medium with serum. A real-time cell analyzer was used to evaluate cell survival. After seeding 200 mL of the cell suspensions into the wells (10,000 cells/well) of the E-plate 96, bDPCs were treated with bioactive components released by the composite materials (1:1 and 1:2 dilutions) and monitored every 15 min for 50 h. Results: According to analysis of variance, there were significant differences between the cell indexes of the control and GC kalore (p < 0.05) and Bisco Reflexions (p < 0.001) groups for the 1:1 dilutions at 25 h. When evaluated at 50 h, 1:1 dilutions of GC Kalore (p < 0.01) and Bisco Reflexions (p < 0.001) reduced cell survival significantly. Conclusions: Although composites resins are being advanced, their cytotoxic effects have been proceeding till this time. However, two of the four materials tested significantly reduced cell viability when compared with control. Clinical relevance: Research should focus on the cytotoxicity of composites in addition to their mechanical properties.
Article
It has long been believed that heavy metals possess many adverse health effects. Uncontrolled industrialization has released heavy metal pollution in the world. Heavy metal pollutants damage organ functions and disrupt physiological homeostasis. Diabetes mellitus is growing in prevalence worldwide. Several studies have indicated that the deficiency and efficiency of some essential trace metals may play a role in the islet function and development of diabetes mellitus. Some toxic metals have also been shown to be elevated in biological samples of diabetes mellitus patients. In the present work, we review the important roles of heavy metals in islet function and diabetes development in which the in vitro, in vivo or human evidences are associated with exposure to zinc, arsenic, cadmium, mercury and nickel. Through this work, we summarize the evidence which suggests that some heavy metals may play an important role in diabetes mellitus as environmental risk factors.
Article
Novel organic–inorganic hybrid membranes composed of poly(vinyl alcohol) (PVA) and γ-(glycidyloxypropyl)trimethoxysilane (GPTMS) were prepared through in situ sol–gel approach. The chemical structure and reaction mechanism for PVA–GPTMS hybrid membranes were tentatively proposed based on FTIR and solid-state 29Si NMR spectra. The free volume characteristics of PVA–GPTMS hybrid membranes were revealed by positron annihilation lifetime spectroscopy (PALS), and the apparent fractional free volume (fapp) were calculated according to free volume cavity size and intensity of o-Ps. The unusual pervaporation properties of PVA–GPTMS hybrid membranes for separating benzene/cyclohexane mixtures were discovered. The permeation flux increased from 20.3g/(m2h) for GPTMS-free membranes to 137.1g/(m2h) for PVA–GPTMS-04 membrane, while separation factor increased from 9.6 to 46.9 simultaneously. The correlation between fapp and permeation flux was established and the improvement in permeability reflected hybridization-induced disruption of polymer chain packing and an accompanying elevated free volume available for molecular diffusion.
Article
The aim of this review article is to summarize the recent in vitro and in vivo evidence in the field of degree of conversion and the monomer leaching from orthodontic adhesive resins. Analysis of the material is structured around the presentation of evidence summarizing the current status in this field. The degree of cure of polymer adhesives modulates the physical and mechanical properties of the material, particularly solubility and degradation and for these reasons are of scientific interest. The leached components from resinous materials, which are related to the degree of cure of the resin, is of important biological interest and has raised serious concern for the possible biological adverse effects in different systems and organs. This paper includes a presentation of techniques used to study the degree of cure and monomer leaching, currently available data from in vitro and in vivo research approaches and the potential clinical impact of in vivo findings.
Article
The toxicity of monomers like bisphenol-A-glycidyldimethacrylate (BisGMA) and urethane-dimethacrylate (UDMA) to cells is well studied. In these studies solubilizers, which have a toxic potential, are used to dissolve the basic monomers in the aqueous medium. In these experiments it is not possible to confidently exclude a synergistic effect of basic monomers and solubilizers in cells. Moreover, less is known about the synergistic interaction between basic- and comonomers (triethyleneglycoldimethacrylate (TEGDMA); 2-hydroxyethylmethacrylate (HEMA)) in cells. We dissolved the basic monomers in the comonomers and incubated human gingival fibroblasts (HGFs) with these binary mixtures in different concentrations. Proliferating HGFs monolayers were cultured in the absence or presence of mixtures of BisGMA/TEGDMA, BisGMA/HEMA, UDMA/TEGDMA and UDMA/HEMA. Twenty-four hours later XTT was added and the formazan formation was quantified. EC(50) values were obtained at half-maximum-effect concentrations from fitted curves. EC(50) values were (mmol/l; mean±sem; n=5): 0.01 BisGMA/0.48 TEGDMA; 0.04 BisGMA/4.99 HEMA; 0.04 UDMA/1.60 TEGDMA and 0.02 UDMA/2.26 HEMA. All tested mixtures induced a dose-dependent loss of viability in HGFs after 24h. The EC(50) values of binary mixtures were significantly (p<0.05) lower compared to the EC(50) values of the pure substances indicating a synergistic interaction of the mixtures on the HGFs. The widely used (co)monomers BisGMA and TEGDMA have the lowest EC(50) values. The highest decrease of EC(50) values, compared with the pure substances, were found in the mixture UDMA/HEMA. Worst case calculations show that the EC(50) values from binary mixtures are at least 6 fold lower compared with known amounts of elutable (co)monomers from polymerized composites.
Article
The cytotoxicity of dental composites has been attributed to the release of residual monomers from polymerized resin-based composites due to the degradation processes or the incomplete polymerisation of materials. 2-Hydroxyethyl methacrylate (HEMA) is one of the major components released from dental resin-based composites. It was shown in vitro that HEMA was released into the adjacent biophase from such materials during the first days after placement. In this study uptake, distribution, and excretion of 14C-HEMA applied via gastric tube or subcutaneous administration at dose levels well above those encountered in dental care were examined in mice to test the hypothesis that HEMA can reach cytotoxic levels in mammalian tissues. 14C-HEMA was taken up rapidly from the stomach and intestines after gastric administration and was widely distributed in the body following administration by each route. Most 14C was excreted within one day as 14CO2. Two metabolic pathways of 14C-HEMA can be described. The peak HEMA levels in all tissues examined after 24 h were lower than known toxic levels. Therefore the study did not support the hypothesis.
Article
This paper surveys the most important developments in resin-based dental composites and focuses on the deficits (e.g. polymerization shrinkage) and strengths of the materials and their clinical implications. Moreover, differences between composite categories, such as hybrid, nanohybrid, microfilled, packable, ormocer-based, silorane-based, polyacid-modified composites (compomers) and flowable composites are highlighted, especially in view of their mechanical behaviour. In addition to the classical dimethacrylate-based composites, special attention is given to alternative monomers, such as siloranes, ormocers or high-molecular-weight dimethacrylate monomers (e.g. dimer acid-based dimethacrylates and tricyclodecane (TCD)-urethane), analysing their advantages, behaviour and abilities. Finally, the paper attempts to establish the needs and wishes of clinicians for further development of resin-based composites.
Article
The diagnosis and treatment of the diseases in a certain coordination is a subject that has been emphasized in recent years. Theragnostics approaches allow simultaneous diagnosis and treatment of chronic diseases such as cancer. An ideal theragnostic should be biocompatible and can be used safely in humans. Although several types of theragnostics have been developed, none of yet satisfied these criteria. Bioinspired materials with noble metal centers encapsulating therapeutic and imaging agents were shown to possess theragnostic activities. In this study, it was aimed to synthesize, characterize, and evaluate the cytotoxic and genotoxic effects of self-assembly of diphenylalanine (Phe–Phe) dipeptides presence of mercury (Hg²⁺) ions to be used for theragnostic. Cytotoxicity and genotoxicity studies were done in mouse fibroblast (NIH/3T3) cells by 3-(4,5-Dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT) and single cell gel electrophoresis (Comet) assays, respectively. It was found that cell viability decreased in a dose-dependent manner in 24-, 48-, and 72-h treatment. Also, Phe–Phe dipeptides did not cause any significant changes in DNA damage at the concentrations of 1, 2, and 5 mg/mL in 4- and 24-h exposures. In the 48-h exposure, Phe–Phe peptide exposure at concentrations of 2 and 5 mg/mL caused a significant increase in DNA damage and in the 72-h of exposure, a significant increase in DNA damage was observed at all studied concentrations. According to the results of the study, it can be said that Phe–Phe dipeptides presence of Hg²⁺ ions are biocompatible and can be used safely for theragnostic purposes.
Article
To analyze the cytotoxic effects of 2-hydroxyethylmethacrylate (HEMA) in human gingival fibroblasts using quantitative x-ray microanalysis (EXPMA) and two classical methods (DNA and LDH release in culture medium). Different concentrations of HEMA (5, 10, 20, 30, and 40 mM) in DMEM medium were used and the effects on human gingival fibroblasts after 6, 12, and 24 h were determined. As controls, fibroblasts cultured with DMEM culture medium (negative control) and fibroblast incubated in 1% triton X (positive control) were used. The results showed that correlation between the concentrations of HEMA and the amount of LDH and DNA released to the medium were statistically significant for all times analyzed. LDH and DNA released from cells incubated in the lowest concentrations of HEMA (5 and 10 mM) were not significantly different to negative controls. In contrast, cells incubated in the highest HEMA concentrations (20, 30, 40 mM) showed a significant increase of both LDH and DNA released to the culture medium at 6, 12, and 24 h. On the other hand, the ionic concentration of the different elements analyzed in this work revealed that the contents of P, S, Cl, and K were significantly higher in the controls than in samples incubated for 6 h in 5 mM or 10 mM HEMA (p < 0.01). K/ Na index (an excellent marker of cell viability) showed a significant decrease, and therefore, viability was significantly reduced. The results suggest that EXPMA is a sensitive method that is able to detect early cell damage even before the cell membrane is altered.
Article
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The toxicity of composite resin on rabbit dental pulp was investigated biochemically. A microsomal fraction of rabbit dental pulp was incubated with each of the components of composite resins, and the formation of peroxide was determined by the thiobarbituric acid reaction. Benzoyl peroxide (BPO), the most widely used catalyst, was the most effective on peroxidation, but monomers were not. Cations such as Cu2+ or Fe2+ were required for acceleration of this reaction. Authentic polyunsaturated fatty acids and phospholipids were extensively converted into their peroxides by BPO, but amino acids and carbohydrates were not. Among the active oxygens, hydroxyl radicals were thought to be responsible for BPO-dependent peroxidation. The results presented in this paper indicate that the lipid portion of the cells may be attacked by hydroxyl radicals produced by BPO and copper or iron. Therefore, BPO is considered to be the major factor responsible for the toxicity of composite resins.
Article
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In previous work, the diffusion of monomers from composite and bonding resins through dentin was demonstrated in vitro. The monomers triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) were identified in samples from the pulp space. In the current study, we examined the effects of two levels of positive hydrostatic pressure on the passage of resin monomers through dentin in vitro from a composite-resin/bonding-resin combination to test the hypothesis that monomer diffusion is prevented by such pressure. An occlusal cavity prepared in the tooth crown was restored with the resins. Distilled water samples from the pulpal space were removed over time and analyzed for monomer content by high-performance liquid chromatography and mass spectrometry. Positive pulpal pressure reduced but did not prevent pulpward movement of diluent monomers that leach from bonding agents and from resin composites through dentin in vitro. The degree of reduction of diffusion was greater with TEGDMA than with the lower-molecular-weight monomer HEMA.
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We tested some resin-based composites used in dentistry for their estrogenic activity. A sealant based on bisphenol-A diglycidylether methacrylate (bis-GMA) increased cell yields, progesterone receptor expression, and pS2 secretion in human estrogen-target, serum-sensitive MCF7 breast cancer cells. Estrogenicity was due to bisphenol-A and bisphenol-A dimethacrylate, monomers found in the base paste of the dental sealant and identified by mass spectrometry. Samples of saliva from 18 subjects treated with 50 mg of a bis-GMA-based sealant applied on their molars were collected 1 hr before and after treatment. Bisphenol-A (range 90-931 micrograms) was identified only in saliva collected during a 1-hr period after treatment. The use of bis-GMA-based resins in dentistry, and particularly the use of sealants in children, appears to contribute to human exposure to xenoestrogens.
Article
Cells of an alveolar type II cell-line (A549) were exposed to ozone, using an in vitro exposure model. In this study, attention was focussed on the cellular glutathione system. It was demonstrated that cellular levels of both reduced (GSH) and oxidized glutathione (GSSG) were significantly reduced after exposure of the cells to ozone. When A549 cells were incubated with methionine sulfoximine and diethylmaleate, glutathione levels were depleted, and the cells showed a marked increase in sensitivity towards ozone. Some of the possible mechanisms by which the observed effects might be explained were investigated. It was shown that glutathione lost from the cells was not incorporated into “mixed disulfides”, but could be detected in the surrounding medium. Furthermore, it was shown that A549 cells do not contain any detectable glutathione peroxidase activity. Therefore it was concluded that glutathione peroxidase-catalysed reduction of lipid peroxides could not be responsible for the observed protective role of glutathione. Finally some other mechanisms by which glutathione might accomplish its antioxidant effect are discussed.
Article
Mercury chloride (HgCl2) has a potent nephrotoxic effect. Most of Hg2+ existing in plasma following HgCl2 exposure forms a complex with sulfhydryl-containing ligands such as albumin and glutathione (GSH). The Hg(2+)-GSH complex is filtered in the glomeruli of the kidney and degraded into Hg(2+)-cysteine in the proximal tubules by the combined action of gamma-glutamyl transpeptidase and dipeptidase present in the epithelial cells. The degradation product is then incorporated and accumulated into the proximal tubule epithelial cells. The accumulated Hg2+ in the epithelial cells finally causes acute tubular necrosis (ATN) by its cytotoxic effect. At present, it is believed that tubular obstruction resulting from ATN triggers the onset of HgCl2-induced acute renal failure (ARF). A progressive fall in glomerular filtration rate (GFR) contributes to the progression of HgCl2-induced ARF. The fall in GFR may be caused by an increment in afferent arteriole resistance (RA) and a decrement in the ultrafiltration coefficient (Kf) due to mesangial cell contraction. These changes in RA and Kf may be attributed to the increased action of the vasoconstrictors, angiotensin II and endothelin-1 and to the decreased action of the vasodilator, nitric oxide observed at the glomerulus level of HgCl2-induced ARF. Accordingly, the imbalance between these vasoactive substances appears to play an important role in the progression of HgCl2-induced ARF due to reducing GFR. Further studies, however, remain to elucidate the mechanisms involved.
Article
Mounting evidence indicates that apoptosis rather than necrosis predominates in many cytolethal toxic injuries. Associated cell death models of apoptosis and necrosis are either: (1) totally separate death modes, (2) a continuum whereby they are extremes of biochemically overlapping death pathways, or (3) essentially distinct processes with only limited molecular and cell biology overlap. We conclude that the current balance of evidence favours the third of these options. The established axiom that, even when considering the same toxicant, injury amplitude (dose) is a primary determinant of whether cells die via active cell death (apoptosis) or failure of homeostasis (necrosis) remains valid. Tissue selectivity of toxicants can stem from the apoptotic or necrotic thresholds at which different cells die, as well as targeting factors such as toxicokinetics, receptor recognition, bioactivation, and cell-specific lesions.
Article
A 36-year-old dental technician for 14 years developed paraesthesia and numbness in her legs. Neurophysiological studies revealed absent sensory nerve action potentials (SNAPs) from her lower limbs and normal upper limb SNAPs on presentation. Motor nerve studies were normal. Repeat studies 2 months after leaving her job showed some improvement in the lower limb SNAPs. It is suggested that her symptoms were caused by occupational exposure to methyl methacrylate monomer.
Article
A laboratory technician developed allergic contact dermatitis to hydroxyethylmethacrylate associated with nausea, diarrhoea and persistent paresthesiae of the fingertips. The gastrointestinal symptoms were reproduced by patch testing. Hydroxyethylmethacrylate was demonstrated to pass through vinyl gloves. Cross reactions occurred to methyl-, ethyl-, propyl- and isopropylmethacrylate but not to butyl- or isobutylmethacrylate.
Article
A series of 16 epithelial cell lines derived from human carcinomatous and nonmalignant epithelial tissues were characterized for markers known to correlate with neoplasia in various model systems. The goal of these studies was to determine which in vitro transformation properties were relevant to human epithelial malignancy. The parameters tested were 1) colony formation in Methocel and on confluent monolayers of normal human epithelial cells and fibroblasts and 2) tumor induction in immunosuppressed mice. Cell lines derived from normal tissue and nonmalignant tissue peripheral to cancerous lesions were generally negative for these properties, whereas the carcinoma-derived lines varied in their expression (some lines being more abnormal than others). In most cases, the lines derived from metastatic lesions had more abnormal properties than did those derived from primary carcinomas.
Article
Paraquat (PQ) is a widely used herbicide that causes acute adult respiratory distress syndrome (ARDS) and chronic lung damage (diffuse fibrosis). One of the earliest biochemical effects induced by PQ is damage to type II pneumocytes with consequent depletion of surfactant. With the aim of counteracting the toxic effects of PQ, a series of investigations were performed into the possible protective effect of the drug ambroxol, which induces the synthesis of surfactant in lung alveolar type II cells. The number of survivors and survival time of rats treated ip with 35 mg PQ/kg was significantly increased by 3 days of ambroxol pretreatment and by ambroxol treatment 30 min or 2 hr after PQ. Total phospholipid content in lung and bronchoalveolar lavage fluid (BALF) was significantly reduced 30 hr after treatment with PQ alone. The association of ambroxol with PQ significantly antagonized this reduction. In BALF the ratio between palmitic acid and stearic acid concentrations was significantly lower in animals treated with PQ alone but was returned to normal by the association with ambroxol. The cell line A549, exposed in vitro to PQ concentrations from 0.5 x 10(-4) to 2 x 10(-3) M, showed a significant dose-dependent loss of viability. Cells pretreated with ambroxol (10 mg/ml) were more resistant to PQ and their viability started to decrease significantly only from a PQ concentration of 0.8 x 10(-3) M. Membrane microviscosity was measured on the same cells. Cells treated with PQ alone showed a reduction of membrane microviscosity, which was significantly counteracted by ambroxol pretreatment. The curves of modification of membrane microviscosity of cells treated with PQ and with ambroxol plus PQ paralleled those of cell viability, indicating that the stimulation of surfactant synthesis in vitro may be a prerequisite for counteracting some of the early effects of PQ.
Article
The present study investigated the effectiveness of treating dentin with 2-hydroxyethyl methacrylate (HEMA) prior to application of an adhesive resin. The adhesive resin was 5% 4-methacryloxyethyl trimellitate anhydride (4-META) in methyl methacrylate (MMA) combined with poly-MMA powder. Polymerization of this resin was initiated by tri-n-butyl borane (TBB). Bovine dentin samples were ground with 600-grit Carbimet paper discs, and demineralized with either an aqueous solution of 10% citric acid/3% ferric chloride (10-3) or an aqueous solution of 10% citric acid (10-0). Improved bond strengths were achieved with HEMA treatment of bovine dentin samples, and improvement of bond strengths was dependent upon the time period of HEMA application. Scanning electron microscope (SEM) examination revealed the formation of a transitional zone of resin-reinforced dentin, termed the "hybrid" layer, in those specimens receiving 10-3 pre-treatment. The adhesive resin impregnated the exposed collagen bundles with which it entangled to create the "hybrid", essential in the attainment of high tensile bond strengths. Specimens pre-treated with 10-0 did not readily form "hybrid" layers. However, if HEMA application followed the 10-0 pre-treatment, "hybrids" were demonstrated on SEM, and bond strength increased to 13 MPa. The ferric ions in the 10-3 effectively improved the diffusivity of dentinal substrates, as did HEMA. This study indicates that HEMA applied to dentinal substrates enhances monomer diffusion and entanglement with dentinal components, and facilitates the formation of a "hybrid" layer.
Article
A study was designed to test the outcome of the deposition of particles of plastic composite dental restorative material in rabbit lungs. Grinding and polishing these restorations in situ produces some particles in the 0.5- to 10-microns size range that easily enter and remain in human lungs and are associated with industrial lung disease. Dental restorative plastic material was ground in the laboratory, suspended in saline solution, and injected transtracheally into four New Zealand white rabbits. Two control rabbits were similarly injected with saline solution transtracheally. Twenty-four hours later, the rabbits were injected with 1 mCi of 67Ga citrate intravenously and subsequently reanesthetized for scanning. Baseline scans were obtained in the six animals prior to the injection of the test particles. Positive gallium scans were obtained 72 h after the administration of particulate material in the four test rabbits. The gallium scans of the control rabbits remained no different from baseline. The study was repeated one month later. The animals were killed seven days after the last gallium scan. Light microscopy and transmission electron microscopy of the lungs of the test animals showed foci of chronic inflammation around particles of the restorative material. Particles were in vacuoles within alveolar macrophages and also free in interstitium. Control animals had normal histologic conditions. Silver amalgam and gold dental restorations have years of clinical use but the new plastic composite restorative materials are rapidly being introduced into human clinical dental practice. Normal use involves polymerization, grinding, and polishing of the material within the mouth. The chronic inflammation in the lungs of rabbits indicates a need to test dental restorative material for lung biocompatibility before further, extensive clinical use.
Article
A tetrazolium compound, XTT, bioreducible to a water-soluble formazan was used to develop a simplified cellular cytotoxicity assay. Most (13/15 melanoma and 2/3 colon carcinoma cell lines tested metabolized XTT greater than 50 times more efficiently than the lymphoid effector cells, and thus the test could be performed without separation of the effector from the target cells. The XTT assay (XTT-A) was compared to the standard 51chromium-release assay (51CrA) in terms of sensitivity as well as intra- and interassay variability using low effector to target cell (E:T) ratios and both short and long incubation periods. The correlation coefficient (r) for percent specific lysis (%SL: 35.0 +/- 15.0 versus 30.2 +/- 15.8) or lytic units (LU20/10(7) effector cells: 405 +/- 208 versus 357 +/- 227) between XTT-A and 51CrA was 0.86 for 4 h XTT-A and 51CrA (n = 37). Due to a poor performance of the 51CrA after 24 h incubation of effector and target cells, the correlation coefficient for 24 h assays was reduced to 0.79 (n = 44,%SL = 63.3 +/- 23.9 versus 55.5 +/- 26.6, and LU = 1267 +/- 982 versus 1017 +/- 691). Inter- and intra-assay variability of XTT-A were significantly lower than those for 51CrA. The total background values for XTT-A and 51CrA were similar in 4 h cytotoxicity assay and lower for XTT-A in assays with 24 h incubation. The sensitivity, in terms of discrimination between effector cells with different lytic capacity and targets with different susceptibility, was identical. The XTT-A was simpler, cheaper, and safer to perform than the 51CrA. Furthermore, the XTT-A was suitable for long-term assays and allowed experiments without requiring trypsinization of tumor cells grown in 96-well plates prior to testing.
1. Organic xenobiotic metabolism often results in oxidative stress, involving GSH depletion, alteration of thiol/disulphide balance and peroxidation of membrane lipids. These events can lead to the disruption of Ca2+ homeostasis, through impairment of the Ca2+ translocases present in cellular membranes. Inhibition of the activity of Ca,Mg-ATPases due to oxidation of their SH groups would lead to uncontrolled rises in cytosolic Ca2+ levels resulting in loss of cell viability. 2. These observations seem to be of interest when interpreting the biochemical mechanisms of heavy metal cytotoxicity. Since these cations (such as Hg2+, Cu2+, Cd2+ and Zn2+) have an extremely high affinity for SH groups, they may affect the function of SH containing proteins, such as the Ca,Mg-ATPases, as in the case of oxidative stress. 3. Results are reported indicating that Hg2+ may stimulate Ca2+ influx through voltage-dependent channels in different experimental systems. Moreover, evidence is presented that heavy metals can inhibit Ca,Mg-ATPase activity and affect mitochondrial functions in the cells of different organisms. 4. The possibility that heavy metal cytotoxicity is mediated through disruption of Ca2+ homeostasis is discussed.
Article
The behaviour of amalgam beam specimens subjected to a sub-modulus of rupture load at 37 degrees C was compared in static and cyclic modes. Testing was performed using identical equipment, with cyclic testing conducted by intermittent load application for both tests. The specimens tested exhibited varying degrees of deformation and times to fracture in both tests. The mode of load application, either cyclic or static, did not appear to have a significant effect on the degree of amalgam deformation or time to fracture. The most important factors relating to deformation are time of total load application, creep of the specific amalgam and temperature of testing.
Article
A new tetrazolium salt XTT, sodium 3'-[1-[(phenylamino)-carbonyl]-3,4-tetrazolium]-bis(4-methoxy-6- nitro)benzene-sulfonic acid hydrate, was evaluated for use in a colorimetric assay for cell viability and proliferation by normal activated T cells and several cytokine dependent cell lines. Cleavage of XTT by dehydrogenase enzymes of metabolically active cells yields a highly colored formazan product which is water soluble. This feature obviates the need for formazan crystal solubilization prior to absorbance measurements, as required when using other tetrazolium salts such as MTT. Bioreduction of XTT by all the murine cells examined was not particularly efficient, but could be potentiated by addition of electron coupling agents such as phenazine methosulfate (PMS) or menadione (MEN). Optimal concentrations of PMS or MEN were determined for the metabolism of XTT by the T cell lines HT-2 and 11.6, NFS-60 a myeloid leukemia, MC/9 a mast cell line and mitogen activated splenic T cells. When used in combination with PMS, each of these cells generated higher formazan absorbance values with XTT than were observed with MTT. Thus the use of XTT in colorimetric proliferation assays offer significant advantages over MTT, resulting from reduced assay time and sample handling, while offering equivalent sensitivity.
Article
The uptake of solvent and the elution of molecules from a dental composite and an unfilled resin were monitored with time during soaking in either water or an ethanol/water mixture. The results showed that approximately 50% of the leachable species were eluted from the composite within three hours of soaking in water, while 75% of the leachable molecules were eluted into the ethanol/water mixture. Elution of nearly all of the leachable components was complete within a 24-hour period in either solvent. The study lends support to the view that dental composites do not provide a chronic source of unreacted monomer to the pulp or other oral tissues, due to a rapid and complete elution of the molecules.
Article
Rats were injected intraperitoneally with HgCl2 at doses of 2.5, 5, 7.5, and 10 mumol of Hg/kg. Urine was collected over a 24-hr period. At this time, plasma samples were taken and kidney damage was assessed by histological examination. Urinary gamma-glutamyltransferase levels were significantly elevated at Hg2+ doses of 7.5 and 10 mumol/kg, consistent with the detection of acute tubular necrosis by light microscopy. Resonances for a large number of low molecular weight metabolites were assigned in high resolution 1H NMR spectra of rat urine. Spectra from small volumes of urine (about 0.5 ml) were obtained in less than 5 min with no pretreatment. Significant Hg2+ dose-related decreases in the excretion of creatinine and citrate and increases of glucose, glycine, alanine, alpha-ketoglutarate, succinate, and acetate were detected. Elevated levels of lactate and creatinine in plasma of rats receiving the two highest doses were found by 1H NMR. There was a good correspondence between the histopathology, enzyme excretion, and 1H NMR urinary metabolite fingerprints in the assessment of Hg2+-induced renal damage. 1H NMR provided a sensitive measure of mercury-induced nephrotoxic lesions, and information on the molecular basis of mercury cytotoxicity was derived from the abnormal patterns of metabolite excretion. These suggested that primary metabolic effects of mercury were upon mitochondrial metabolism, in particular inhibition of certain citric acid cycle enzymes leading to decreased utilization of alpha-ketoglutarate and succinate by the renal tubular cells. The decrease in urinary citrate associated with Hg2+ dosing was attributed to intracellular, tubular acidosis with concomitant enhanced citrate reabsorption. The acidosis was assumed to arise from a combination of the inhibition of tubular carbonic anhydrase and a mild metabolic lactic acidosis due to increased activity of anaerobic pathways in the kidney. The possible extension of the 1H NMR techniques to the investigation of the nephrotoxic potential of other compounds and drugs is discussed.
Article
Depletion of cellular glutathione (GSH) has been shown to sensitize A549-T27 human tumor cells to the cytotoxic effects of Cd2+. In this study the temporal and quantitative relationships between reduced cellular GSH levels and cadmium cytotoxic response in these cells were further investigated. Exposure of A549-T27 cells to 10 mM buthionine sulfoximine (BSO) for 8 h decreased their GSH level by 65%. This GSH level remained relatively constant for 8 h in the presence or absence of BSO, but recovered to 83% of the normal cellular level 24 h after removal of BSO. Exposure to 5 microM Cd2+ for 8 h did not significantly change cellular GSH levels. Pretreatment of the A549-T27 cells with 10 mM BSO for 8 h and subsequent exposure of the cells to Cd2+ for 10 days, with or without concurrent treatment of 10 mM BSO during the first 8 h of Cd2+ exposure, resulted in disappearance of the 5 microM Cd2+ threshold for cytotoxic response and reduction of the LC50 from 31 microM Cd2+ to 21 microM. Similar results were obtained when BSO pretreated cells were exposed to Cd2+ for 8 h. The threshold for cytotoxic response of 10 microM Cd2+ disappeared and the LC50 was reduced from 60 microM to 29 microM Cd2+ (with concurrent BSO treatment) and 30 microM (BSO pretreatment only). The results show that GSH plays an important role in early cellular protective responses to Cd2+.
Article
The well known inferential statistical procedures only take into account the test of a single hypothesis or the estimation of a single parameter. In practical drug research the scientist in most cases is interested in multiple tests of several hypotheses or a simultaneous estimation of several parameters. After introducing the principal problems of simultaneous statistical inference several statistical methods are discussed. These methods can be applied to a variety of problems in drug research.
Article
Mono-, di-, and trimethacrylates (monomers) are widely used in dentistry as restorative materials, adhesives, prosthetic devices, etc. It is known that the residual monomers released from the cured resin have been implicated in toxicological effects. In order to monitor the biological actions at the membrane level induced by monomers, we studied the changes in the phase transition temperature (T) and enthalpy (delta H) of dipalmitoyl-phosphatidylcholine liposomes induced by 37 different monomers using differential scanning calorimetry (DSC). The monomers that caused large changes in the T and delta H were vinyl monomers; acrylates; monomethacrylates that contain hydroxy, carbonyl, amino and phenyl groups; dimethacrylates with short-chain substituents; and aliphatic trimethacrylates. It is suggested that the changes in the T and delta H values may be due not only to hydrophobic interactions, but also to interactions induced by the double bonds or the functional groups in the monomers. On the other hand, methacrylates with simple alkyl ester linkage and dimethacrylates with bisphenol A groups exhibited the smallest changes. The changes in the T and delta H induced by highly hydrophobic methacrylates were small due to their slower interaction. These changes in transition properties of liposomes seem to be related to biological activities.
Article
Triethylene glycol dimethacrylate (TEGDMA) is a component of some resin composites which contributes to their cytotoxicity. The presence of dentine between resin composite and test cells reduces the cytotoxicity in vitro. To determine why dentine has this protective effect, the diffusion of TEGDMA from a composite resin through dentine to the pulp space was compared with release directly into aqueous solution in vitro. Both release rate and total cumulative release of TEGDMA for the two groups, at times up to 100 days, were determined using reversed-phase HPLC. Release rate directly into water was highest in the minutes immediately after immersion and declined thereafter. However, in the tooth model, using an equivalent mass and surface area of composite resin, no TEGDMA was detectable in the pulp space until 43 min after restoration placement. The rate of diffusion through dentine from that time until day 1 was less than 1% of the highest (initial) direct release rate. The rate declined thereafter. It is relevant, however, that by day 3 the total cumulative release of TEGDMA through dentine was 60% of the direct release. Dentine therefore appears to exert its protective effect principally by retarding or 'damping' the initial high release of TEGDMA to a substantial degree.
Article
A significant amount of residual monomer or short chain polymers remain unbound in set composite material. Due to its potential impact on both the biocompatibility and the structural stability of the restoration, many investigators have studied the elution of these unbound molecules into aqueous media. The results of these studies suggest that elution of leachable components from composites is rapid, with the majority being released within a matter of hours. Weight losses of up to 2% of the mass of the composite have been reported under certain conditions. The studies have also shown that the extent and rate of elution of components from composites is dependent upon several factors. The quantity of leachables has been correlated to the degree of cure of the polymer network. The composition and solubility characteristics of the extraction solvent influence the kinetics and mechanism of the elution process. Elution is generally thought to occur via diffusion of molecules through the resin matrix, and is therefore dependent upon the size and chemical characteristics of the leachable species.
Article
The effect of mercury as Hg2Cl2 and HgCl2 on the antioxidant enzyme levels and its toxicity was investigated in an insect model comprised of adult females of the common housefly, Musca domestica, and fourth-instar larvae of the cabbage looper moth, Trichoplusia ni. HgCl2 was found to be more toxic than Hg2Cl2 to both M. domestica and T. ni. The LC50s for M. domestica were 1.17% and 0.38% w/v concentration for Hg2Cl2 and HgCl2, respectively. For the more tolerant T. ni, the LC50S were 5.15% for Hg2Cl2 and 0.96% w/w concentration for HgCl2. The minimally acute LC5 dose of both oxidation states of Hg was approximately 0.005% for both insects (w/v for M. domestica and w/w for T. ni). At the LC5, both forms of Hg significantly induced the activity of superoxide dismutase in both insect species. Catalase was induced by both Hg2Cl2 and HgCl2 in M. domestica but was only induced by HgCl2 in T. ni. Glutathione-S-transferase, its peroxidase activity, and glutathione reductase activities were also significantly altered in most cases by Hg in both insects although the pattern of alternation was different between the two insects. It is evident that mercury induces oxidative stress in insects as it does in vertebrates. Our findings suggest that insects may serve as a valuable, non-mammalian model species to assess Hg-induced oxidative stress as a component of environmental toxicity.
Article
The purpose of this study was to compare a methylthiazole tetrazolium (MTT) dye colorimetric method with the standard 51Cr assay as methods of assessing cytotoxicity of dental materials. Two MTT-based colorimetric formats, test tube and 96-well microplate methods, were compared to the 51Cr release assay. A series of eight dental materials were evaluated. Cytotoxicity profiles were determined for each test material. A TC50 value (Toxic Concentration required to kill 50% of the cells) was determined for each biomaterial, and these results were used to make statistical comparisons between the methods. The three methods were statistically correlated (p<0.005) by comparison of the eight samples tested. That is, the same rank in toxicity was given by the two tetrazolium sample formats and the 51Cr method. The MTT assay was found to have several advantages in comparison to the current standard 51Cr release assay. Optimized in the 96-well format, complete dose response curves and greater sample comparisons can be made rapidly, making the MTT method more economical in time and cost. Furthermore, the MTT method is based on intracellular biochemical changes, measuring cell viability rather than cell morbidity, and has lower detectable limits than the 51Cr release method. There is also less detector chemical binding interference than encountered in the 51Cr release method.
Article
This study was performed to characterize the (possible) DNA-damaging properties of dental materials and to identify specific compounds that contribute to this genotoxicity. For screening, three tests that assay for different aspects of genotoxicity (i) the bacterial umu-test; (ii) the eucaryotic DNA synthesis inhibition test; and (iii) the in vivo alkaline filter elution technique were chosen. This investigation gives several lines of evidence that most dental materials tested (14 chemical monosubstances present in dental devices and 7 extracts of dental materials) yield 'positive' results in at least one of the genotoxicity tests, however, with effects ranging from 'borderline' to 'strong positive'. The extracts of the widely used dental materials Vitrebond and AH26 elicited clear concentration-related genotoxic responses in all test systems. On the basis of these data and public concern, more attention has to be given to local or systemic complications which may be associated with the use of dental materials.
Article
This paper describes a probabilistic assessment of neurological risks incurred from consuming fish containing methylmercury (MeHg), focusing on the incremental effects of Hg deposited from local coal combustion. A Monte Carlo model is used to simulate a "worst case" scenario in which a population of 5000 fish eaters in the upper midwestern United States derive the freshwater fish portion of their diet from local waters near a hypothetical large coal-fired power plant. This population is characterized by distributions of body mass, half-life of MeHg, and the ratios of blood to body burden and hair to blood MeHg. Each person's diet consists of varying amounts of tuna fish, freshwater sportfish, and marine fish and shellfish, the MeHg contents of which are characterized by national distribution statistics, as are the consumption rates for marine fish. The consumption rates for freshwater fish are specific to the region. The fish portion size is linked to body mass by a variable correlation. Each meal is assumed to be an independent sample; thus, as metabolic equilibrium is approached, each person's body burden of MeHg tends to approach the value corresponding to the mean MeHg intake for the population. Predictions of MeHg levels in hair by this model compared well with an observed distribution of 1437 women. Two neurological endpoints were examined: adult paresthesia, as related to MeHg body burden, and congenital neurological effects, as associated with average concentrations of MeHg in maternal hair during pregnancy. Two exposure scenarios are considered: a "baseline" in which the source of the mercury in fish is from background atmospheric deposition, and an "impact" scenario, in which local Hg deposition and concentrations in fish are roughly doubled to represent additional deposition from the hypothetical nearby power plant. For both scenarios, the 99th percentile of MeHg body burden was more than an order of magnitude below the lowest level at which increased transient adult paresthesia was experienced in an acute MeHg poisoning incident in Iraq. We thus conclude that neurological risks to adults from MeHg resulting from atmospheric Hg deposition are trivial. Based on three epidemiological studies of congenital neurological risks, we find that fetal effects appear to be more critical and that there is a smaller margin of safety for pregnant consumers of freshwater sportfish. However, the margin of safety is still considerable and may have been diminished by uncertainties in the relationships between maternal hair Hg and the actual fetal exposures.
Article
Chemical components of many materials used in dental practice can move into the local biophase, where they can have beneficial or adverse effects. The strongest indirect evidence that components of resin-based materials used in dentistry can move into the biophase are the many reports of allergic dermatitis in dental personnel. Direct measurement of component release has shown that triethylene glycol dimethacrylate (TEGDMA), hydroxyethyl methacrylate (HEMA), and, in the case of some orthodontic cements, bis-glycidyl methacrylate and benzoyl peroxide can move into an aqueous medium from a range of resin-based materials which are applied to teeth as part of oral care. In the case of resin composite restorations, HEMA and TEGDMA are available in microgram quantities via the salivary surface in the minutes and hours after clinical placement and via dentin and pulp in the hours and days after placement. Fortunately, moderate thickness of dentin protects pulp tissue against local toxicity. There are no data which suggest that systemic toxicity is a risk with any of these materials. There are some case reports of allergic responses to the monomers in patients, but the incidence of such responses appears at present to be much lower than that in dental personnel.
Article
Effects organic mercurials (PCMBS, PCMB, mersalyl) an alkylating reagent (NEM), disulphide reagents (DTP, CPDS) and the dithiocarbamate agent DSF (disulfiram) were studied in hepatocyte culture. Cytotoxicity, was on a high level (organic mercurials), moderate (NEM, DTP), or none (DSF, CPDS). The organic mercurials and NEM induced glutathione depletion. Disulphide compounds were detoxified by metallothionein binding. Organic mercurials inhibited the cellular glucose uptake. The most prominent effect of NEM, DTP and DSF was an inhibition of the TCA-cycle. The hepatocellular BSP metabolism was delayed by all tested compounds. Albumin synthesis was stimulated by pyruvate and blocked by PCMB and PCMBS, by inhibiting the hepatocellular amino acid uptake. Phase I and II biotransformation reactions were inhibited by PCMBS and PCMB by direct binding to Cyt. P450 cysteinyl-residues and active sites of UDP-glucuronyltransferases. DSF probably reacts by diminishing the availability of the cofactor NADPH. Isolated ALDH (EC 1, 2, 1.3) was inhibited by all studied compounds. In cellular systems, DSF and the organomercurials inhibited ALDH, thereby reducing the cell's capacity of ethanol catabolism. All tested compounds showed, in low doses, the anabolic ability of insulin mimicking, as demonstrated in a balanced endocrine in vitro testsystem. Morphology, Exposure to NEM, DTP, CPDS, DSF did not result in any morphological alterations in the cell cultures. However, an exposure to PCMBS and PCMB, resulted in extensive bleb-formation, as a result of SH group blocking at the cell's outer membrane. It can be concluded, that cultured hepatocytes from human or rat origin, resist an exposure to alkylating and disulphide SH-reagents up to relatively high dose (1.0 mM). However, organic mercury compounds triggered an extensive bleb formation, as a result of SH-blocking, thereby disturbing the osmotic balance by blocking Na+/K+ carriers. Of all tested reagents, organic mercury compounds arose as the most toxic reagents.
Article
The mutagenic potential of glutaraldehyde-containing dentin bonding agents was shown in previous studies using a bacterial gene mutation assay, the Ames test. However, current strategies of genotoxicity testing and regulatory requirements for the biological evaluation of medical devices recommend a battery of tests that indicate induced mutations in prokaryotic and eukaryotic cells. Accordingly, the mutagenicity of three glutaraldehyde-containing bonding agents (Syntac adhesive, Prisma Universal Bond 3 adhesive, and Gluma 3) was investigated using a quantitative mammalian cell gene mutation assay (V79/HPRT test) in the present investigation. The materials were extracted in dimethyl sulfoxide (0.1 g/2 mL) for 24 h and original extracts were then serially diluted in cell culture medium before exposure to V79 cells. Cytotoxic and mutagenic effects were observed with identical concentrations of extracts of the different test materials. There was a moderate decrease of the number of surviving cells immediately after the end of exposure. Mutagenicity at the hprt locus in V79 cells was found with all materials tested, and the increases in the absolute numbers of mutants were dose dependent. The mutant frequencies were about 15- (Syntac adhesive and Gluma 3) to 20-fold (Prisma UB3 adhesive) higher than solvent control values. Since other substances than glutaraldehyde may be responsible for the mutagenic effects in mammalian cells in this study, work is currently in progress to identify the individual mutagenic compounds of dentin adhesives and related composite materials.
Article
Dentistry uses a variety of different polymer materials. Dental polymer materials are based on methacrylate, its polymer, and polyelectrolytes. The setting of restorative materials and adhesives is initiated chemically by mixing two components or by light. In both cases, polymerisation is incomplete and monomers, not reacted, release. Studies have documented that monomers may cause a wide range of adverse health effects such as irritation to skin, eyes or mucous membranes, allergic dermatitis, asthma, parenthesise in the fingers, and disturbances from central nervous system such as; headache, pain in the extremities, nausea, loss of appetite, fatigue, sleep disturbances, irritability, loss of memory and changes in blood parameters. Dental personnel are occupationally exposed when handling the non reacted monomers. The use of gloves do not give enough protection as monomers, released from the material, easily penetrate all gloves used in dentistry. Face masks do not prevent inhalation of monomers. Ordinary glasses do not protect the eyes against vapor from monomers. The result from this study demonstrate the need for the development of ergonomic procedures and practices for safe handling of such materials in dental clinics.
Article
The effect of zinc on various pulmonary cell lines has been studied by measuring the depletion of total cellular glutathione after exposure to zinc(II) chloride at different concentrations. Total cellular glutathione (cGS) was measured at 31 ± 3 nmol/mg, 3.8 ± 0.6 nmol/mg, and 3.7 ±1.2 nmol/mg protein in A549, L2, and 11Lu cells, respectively. After treatment with buthionine sulfoximine (BSO), the cGS levels decreased by 20% in A549 cells and below 0.2 nmol/mg in L2 and 11Lu cells. Exposure of A549 cells to 25–200 μM ZnCl2 for 4 h alone decreased the cGS content to 60–80%. There was little additional effect in BSO-pretreated cells. In L2 and 11Lu cells, the decrease of cGS was 70–85% following exposure to 15–150 μM ZnCl2 for 2 h. If BSO was also used, the decrease in cGS was 85–95% in L2 cells and 75–85% in 11Lu cells. Exposure to 25–250 μM ZnCl2 for 2 h diminished protein synthesis as determined by radiolabeled methionine incorporation, with half-maximum inhibition (EC50) from 40–160 μM ZnCl2. To attain similar EC50 values in BSO-pretreated cells, only about half the zinc concentrations were required as compared to cells without pretreatment. The decrease of cGS was accompanied by an increased ratio of oxidized : reduced glutathione that was more pronounced in cells with low glutathione content.
Article
A 36-year-old dental technician for 14 years developed paraesthesia and numbness in her legs. Neurophysiological studies revealed absent sensory nerve action potentials (SNAPs) from her lower limbs and normal upper limb SNAPs on presentation. Motor nerve studies were normal. Repeat studies 2 months after leaving her job showed some improvement in the lower limb SNAPs. It is suggested that her symptoms were caused by occupational exposure to methyl methacrylate monomer.
Article
The effect of dental composite components triethyleneglycoldimethacrylate (TEGDMA) and hydroxyethylmethacrylate (HEMA) as well as mercuric chloride (HgCl(2)) and methylmercury chloride (MeHgCl) on gluconeogenesis was investigated in isolated rat kidney tubules. From starved rats kidney tubules were prepared and isolated by digestion with collagenase. Every 10 min up to 60 min 1-ml samples were drawn from the cell suspension for quantitating the glucose content. Glucose formation in controls was 3.3 +/- 0.2 nmol/mg. per min (mean +/- SEM, n=21). Relative rates of glucose formation were obtained by expressing individual rates as a percentage of the corresponding control. X-Y concentration curves (effective concentration, EC) of the substances were calculated by fitting a four-parametric sigmoid function to the relative rates of glucose formation at various test concentrations. At the end of the incubation period cell viability was assessed by trypan blue exclusion. Cell viability decreased within the 60 min interval from 90 to approx. 80% (controls), <25 (HEMA), <20 (TEGDMA), <10 (MeHgCl), and <10% (HgCl(2)). Values of 50% effective concentration (EC(50)) were calculated from fitted curves. EC(50) values were (mmol; mean +/- SEM; n=4): HEMA, 17.7 +/- 2.9; TEGDMA, 1.8 +/- 0.2; MeHgCl, 0.018 +/- 0.0005; and HgCl(2), 0. 0016 +/- 0.0005. The toxic effect of HgCl(2) was approximately 1000 or 10 000 higher than that of the dental composite components TEGDMA or HEMA, respectively.
Article
The effect of dental composite components triethyleneglycoldimethacrylate (TEGDMA) and hydroxyethylmethacrylate (HEMA), as well as mercuric chloride (HgCl2) and methylmercury chloride (MeHgCl) was investigated on the release of lactatedehydrogenase (LDH) from alveolar epithelial lung cell lines in vitro. The confluent cell layers from the A549 (human, malignant) and the L2 cells (rat) were incubated with various concentrations of HEMA, TEGDMA, MeHgCl and HgCl2 at 37 degrees C in 2% (v/v) CO2 atmosphere for 8h. In further experiments the L2 cells were incubated with the same compounds for 6-48 h. LDH release was measured and the values were expressed as percentage of the LDH content. The values were plotted on a concentration log-scale and the substance concentration at the maximum slope was assessed as effective concentration (EC50). A significant (p<0.05) increase in the LDH release was found in the L2 cells after 8-h incubation with HEMA (4 mmol/l), TEGDMA (2 mmol/l), MeHgCl (0.01 mmol/l) and HgCl2 (0.015 mmol/l), and in A549 cells with HEMA (14 mmol/l), TEGDMA (15 mmol/l), MeHgCl (0.15 mmol/l) and HgCl2 (0.05 mmol/l), compared to controls. The EC50 values from compounds in the L2 cells are shown in the following table (mean; sem in parentheses; n=3-6; #n=1): [see text]. The toxic effect of HgCl2 and MeHgCl from the L2 cells was about 100-700-fold higher than of the dental composite components. A significant (p<0.05) time dependent increase of toxicity was observed with TEGDMA, HEMA and MeHgCl.
Heavy metals and heavy-metals antagonists Goodman & Gilman's. The pharmacological basis of therapeutics
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  • J Hardman
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  • P Molino
  • Goodman Gil
Klaassen C. Heavy metals and heavy-metals antagonists. In: Hardman J, Limbird L, Molino! P, Ruddon R, Goodman Gil-man A, editors. Goodman & Gilman's. The pharmacological basis of therapeutics. New York: McGraw-Hill, 1998. p. 1649}71.
Amalgam im Spiegel kritischer Auseinandersetzung. Interdisziplinäre Stellungnahmen zum ‘Kieler Amalgam Gutachten
  • S Halbach
  • R Hickel
  • H Meiners
Halbach S, Hickel R, Meiners H. Amalgam im Spiegel kritischer Auseinandersetzung. InterdisziplinaK re Stellungnahmen zum &Kieler Amalgam Gutachten'. Ko K ln: Deutscher A G rzte, 1999.
ZahnfuK llungen aus Amalgam*tickende Zeitbomben? MuK nch
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Reichl FX. ZahnfuK llungen aus Amalgam*tickende Zeitbomben? MuK nch Med Wschr 1994;136:31.
Modern restaurative materials
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Hickel R. Modern restaurative materials. Dtsch ZahnaK rztl Z 1997;52:572}85.
Probleme des multiplen Schätzens in der Arzneimittelforschung [Problems of multiple tests and evaluations in drug research]
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Forst HT. Probleme des multiplen SchaK tzens in der Arzneimittelforschung [Problems of multiple tests and evaluations in drug research]. Arzneimittelforschung 1985;35:563}9.
Amalgam im Spiegel kritischer Auseinandersetzung. InterdisziplinaK re Stellungnahmen zum &Kieler Amalgam Gutachten'. Ko K ln: Deutscher A G rzte
  • S Halbach
  • R Hickel
  • H Meiners
Halbach S, Hickel R, Meiners H. Amalgam im Spiegel kritischer Auseinandersetzung. InterdisziplinaK re Stellungnahmen zum &Kieler Amalgam Gutachten'. Ko K ln: Deutscher A G rzte, 1999.
Zahnrestaurationsmaterialien
  • Reichl
Zahnfüllungen aus Amalgam—tickende Zeitbomben?
  • Reichl
An insect model for assessing mercury toxicity
  • Zaman