Study of cellular toxicity in vitro of two resins for orthodontic use.

OBJECTIVE: The objective of this work is to compare cellular toxicity in vitro of two resins for orthodontic use: an auto-polymerizable composite and a photo-polymerizable composite. MATERIALS AND METHODS: Samples were obtained by joining a couple of steel orthodontic brackets by using auto-polymerizing or photo-polymerizing resin. We used a halogen lamp, a mini LED lamp and a fast LED lamp used for orthodontics cure for 40 seconds. The 3T3 Swiss cellular line of fibroblasts was used. The samples obtained were used to determine the cellular toxicity in vitro using the Neutral Red Up-take (NRU) and the 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RESULTS: Toxicity of the extract appraised at a low level at MTT and NRU assays. There were statistically relevant differences between the toxicity induced by the auto-polymerizing material and the toxicity induced by the photo-polymerizing composite material, polymerized with the blue-light lamp (p < 0.001) and with the mini LED lamp (p < 0.05). CONCLUSIONS: From the data collected in this study, we can conclude that both resins show a low level of cytotoxicity that, in the case of photochemical polymerizing resin, depends on the characteristics of the lamp.

Comparison of Various Implant Provisional Resin Materials for Cytotoxicity and Attachment to Human Gingival Fibroblasts.

PURPOSE: The aim of this study was to evaluate the responses of human gingival fibroblast (HGF-1) in contact with provisional materials with various chemical compositions and fabricated using different methods. MATERIALS AND METHODS: A total of 210 specimens in eight experimental groups were used. Groups were divided by chemical compositions (poly[ethyl methacrylate], poly[methyl methacrylate], bis-acryl, and hybrid ceramic) and fabricating methods (direct, indirect, and computer-aided design/computer-aided manufacturing [CAD/CAM]). To evaluate the surface characteristics of each group, roughness, water contact angle, and degree of conversion were measured. The responses of HGF-1 to provisional materials were evaluated with cytotoxicity and cell attachment assay. The roughness, surface energy, degree of conversion, level of cytotoxicity, and cell attachment were compared between groups using one-way analysis of variance (ANOVA) and Tukey's multiple comparison (α = .05). RESULTS: The poly(ethyl methacrylate)-direct/indirect and poly(methyl methacrylate)-direct/indirect groups showed higher roughness than the bis-acryl-direct/indirect, poly(methyl methacrylate)-CAD/CAM, and hybrid ceramic-CAD/CAM groups with statistical significance (P < .05). The poly(ethyl methacrylate)-direct group showed the significantly highest water contact angle, and the hybrid ceramic-CAD/CAM group showed the lowest water contact angle (P < .05). The groups that used indirect fabrication methods showed a higher degree of conversion than those that used direct fabrication methods, regardless of chemical composition (P < .05). The poly(ethyl methacrylate) groups showed significantly lower cell viability than the other groups regardless of fabricating methods (P < .05). The poly(ethyl methacrylate)-direct method group showed the lowest cell attachment, and the hybrid ceramic-CAD/CAM method group showed the highest cell attachment (P < .05). CONCLUSION: Poly(methyl methacrylate) and bis-acryl have lower cytotoxicity to HGF-1 than poly(ethyl methacrylate). Indirect fabrication and CAD/CAM are recommended to prevent residual monomer and achieve high cell attachment. To use direct fabrication methods, the auto-mix system is beneficial for the favorable cell response, as it derives a smooth surface.

Biological Effects of Provisional Resin Materials on Human Dental Pulp Stem Cells.

OBJECTIVES: This study investigated the in vitro cytotoxicity as well as the proinflammatory cytokine expression of provisional resin materials on primary cultured human dental pulp stem cells (hDPSCs). METHODS: Five commercially available provisional resin materials were chosen (SNAP [SN], Luxatemp [LT], Jet [JE], Revotek LC [RL], and Vipi block [VB]). Eluates that were either polymerizing or already set were added to hDPSCs under serially diluted conditions divided into three different setting times (25% set, 50% set, and 100% set) and incubated for 24 hours with 2× concentrated culture media. Cell cytotoxicity tests were performed by LDH assay and live and dead confocal microscope images. The expression of proinflammatory cytokines in SN and VB was measured using cytokine antibody arrays. Data were analyzed using repeated measures analysis of variance (ANOVA) or ANOVA followed by the Tukey post hoc test at a significance level of p<0.05. RESULTS: Cytotoxicity greater than 30% was observed in the 50% diluted culture in SN, LT, and JE in the already set stage (p<0.05), while it was detected in SN and LT in early or intermediate stage samples. The cytotoxicity of SN, JE, and LT was greater with eluates from the polymerizing phase compared to that from already set samples (p<0.05), as observed by live and dead images. On the other hand, RL and VB did not exhibit cytotoxicity greater than 30%. Proinflammatory cytokines were not detected in 12.5% diluted culture with eluates from VB and early set stage SN. CONCLUSIONS: The eluates from chemical-activated provisional resin materials during polymerization (SN, LT, and JE) were cytotoxic to hDPSCs and may adversely affect pulp tissue.

Cytotoxicity and bioactivity of various pulpotomy materials on stem cells from human exfoliated primary teeth.

AIMS: To investigate the cytotoxicity and bioactivity of several pulpotomy materials: Biodentine (Septodont, Saint-Maur-des-Fosses, France) MTA (Angelus, Londrina, PR, Brazil), Theracal LC (Bisco Inc., Schamburg, IL, USA) and IRM (Dentsply DeTrey GmbH, Konstanz, Germany), after contact with stem cells isolated from human exfoliated primary teeth (SHEDs). METHODOLOGY: SHEDs were cultured in the presence of the eluates of various pulpotomy materials for 24, 48 and 72 h. Cell viability was determined by mitochondrial dehydrogenase enzymatic (MTT) assay. Apoptosis and changes in cell phenotype were evaluated by flow cytometry. Also, an in vitro scratch wound-healing assay was used to determine their effects on cell migration. To assess cell morphology and attachment to the different pulpotomy materials, SHEDs were directly seeded onto the material surfaces and analysed by scanning electron microscopy (SEM). Finally, the deposition of a calcified matrix in presence of these materials was verified by Alizarin Red staining. Statistical analysis was performed with analysis of variance and Bonferroni or Tukey post-test (α = 0.05). RESULTS: Cell viability in the presence of Biodentine eluates was significantly higher to that obtained using complete medium alone (control; P < 0.01) and was also significantly higher than using MTA Angelus from 48 h of incubation (P < 0.01). However, Theracal LC and IRM were associated with low rates of cell viability (P < 0.001). Similar results were obtained in an apoptosis assay. In addition, SHEDs maintained their mesenchymal phenotype in all conditions although their capacity to migrate was higher in the presence of Biodentine. SEM studies revealed a suitable proliferation rate, cell spreading and attachment, especially when using Biodentine and MTA Angelus discs. Finally, Biodentine eluates significantly induced calcified matrix deposition from 7 days of culture (P < 0.01). CONCLUSIONS: Biodentine exhibited better cytocompatibility and bioactivity than MTA Angelus, Theracal LC and IRM.

Cytotoxicity of soft denture lining materials depending on their component types.

PURPOSE: To evaluate the difference in cytotoxicity of soft denture lining materials depending on their component types. MATERIALS AND METHODS: Ten commercially available soft denture lining materials (SDLM) consisting of five silicone-based materials and five acrylic-based materials were evaluated. For the MTT test, cured SDLM samples were extracted in a culture medium for 24 hours, and L-929 cells were incubated in the extracted medium for 24 hours. Cell viability was determined using a microplate reader and compared with those of the negative control, which were cultured in a culture medium without test material. Agar overlay test was performed for the cured SDLM samples according to International Organization for Standardization (ISO) 7405. RESULTS: Among silicone-based lining materials, GC Reline Soft, Mollosil plus, and Dentusil showed a cell viability of 107.2% ± 4.5%, 102.3% ± 2.84%, and 93.0% ± 8.0%, respectively, compared with the control. Mucopren and Sofreliner Tough displayed significantly lower cell viability (86.4% ± 10.3% and 81.5% ± 4.3%,respectively) compared with the control (P < .05). Among acrylic-based materials, Kooliner, Visco-gel, Soft liner, Dura Base, and Coe-Soft displayed cell viability of 99.2% ± 14.6%, 93.1% ± 9.5%, 89.1% ± 9.8%, 87.6% ± 7.9%, and 75.9% ± 15.7%, respectively, compared with the control. Dura Base and Coe-Soft displayed significantly lower cell viability compared to the control. However, for all tested materials, cell viability exceeded the requirement limit of 70% specified in ISO 10993-5. In the agar overlay test, all five silicone-based materials and acrylic-based Kooliner were ranked as "noncytotoxic." However, Visco-gel was ranked as "mildly cytotoxic," and Soft liner, Coe-Soft, and Dura Base were ranked as "moderately cytotoxic." CONCLUSION: When an acrylic-based soft denture lining material is used, the possibility of a cytotoxic effect should be considered.

In vitro biocompatibility and oxidative stress profiles of different hydraulic calcium silicate cements.

INTRODUCTION: MTA Plus is a new calcium silicate cement with unknown cytotoxicity characteristics. The objectives of this study were to examine the effect of MTA Plus on the viability, apoptosis/necrosis profile, and oxidative stress levels of rat odontoblast-like cells. METHODS: MDPC-23 cells were exposed to gray and white MTA Plus (GMTAP, WMTAP), gray and white ProRoot MTA (GMTA, WMTA) cements, or their eluents. The cells were evaluated for (1) cell viability by using XTT assay, (2) apoptosis/necrosis by using flow cytometry and confocal laser scanning microscopy, and (3) oxidative stress by measuring reactive oxygen species. RESULTS: XTT assay showed that all test cements exhibited marked initial cytotoxicity that decreased with time. By the end of the third week, GMTAP and GMTA were comparable to untreated cells (negative control) in terms of cell viability, whereas WMTAP and WMTA were significantly lower than the untreated cells. Apoptosis/necrosis profiles of cells exposed to WMTAP and GMTAP were not significantly different from untreated cells, whereas cells exposed to WMTA and GMTA showed significantly less viable cells. All experimental groups exhibited reduction of intracellular reactive oxygen species formation compared with untreated cells, although cells exposed to WMTA were not significantly different from untreated cells. CONCLUSIONS: Both the gray and white versions of MTA Plus possess negligible in vitro cytotoxic risks that are time and dilution dependent. They enrich the spectrum of hydraulic calcium silicate cements currently available to clinicians for endodontic applications.

Effects of ProRoot MTA, Bioaggregate, and Micromega MTA on odontoblastic differentiation in human dental pulp cells.

INTRODUCTION: The aim of this study was to compare the biocompatibility and odontogenic potential of newly developed Bioaggregate (BA) and Micromega MTA (MMTA) with ProRoot MTA (PMTA) and intermediate restorative material (IRM) by using human dental pulp cells. METHODS: Biocompatibility was assessed by an 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide assay and scanning electron microscopy. Differentiation was evaluated by alkaline phosphatase (ALP) activity, alizarin red staining, and reverse transcriptase-polymerase chain reaction for the maker genes. The levels of inflammatory mediators and cytokines were measured by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay. RESULTS: PMTA, BA, and MMTA exhibited equally good biocompatibility, whereas IRM showed cytotoxicity compared with these materials. PMTA, BA, and MMTA increased the ALP activity, promoted mineralization nodule formation, and enhanced the mRNA expression level of the osteogenic/odontogenic markers (ALP, osteopontin, osteocalcin, dentin sialophosphoprotein, and dentin matrix protein-1) compared with IRM. The levels of proinflammatory mediators and proinflammatory cytokines were lower in PMTA, BA, and MMTA compared with the IRM group. CONCLUSIONS: Collectively, the biocompatibility, odontogenic potentials, and inflammatory response of BA and MMTA are equal to those of PMTA and superior to those of IRM.

Evaluation of methyl methacrylate monomer cytotoxicity in dental lab technicians using buccal micronucleus cytome assay.

Methyl methacrylate (MMA) monomer, a primary component of dental resins, is known to induce cytotoxicity, dermatitis, and neuropathy. The objective of this study was to assess the incidence of micronuclei (MN) in buccal mucosal cells of dental technicians exposed to MMA using Buccal Micronucleus Cytome (BMCyt) assay. The Risk Group (RG=13) consisted of all the technicians working in the prosthetic production laboratory of KKU-College of Dentistry. The Control Group (CG=14) consisted of healthy students and doctors matching the age of RG subjects. Buccal mucosa scrapes obtained from all the 27 RG and CG subjects were stained with Papanicolaou stain and observed under oil immersion lens (100×) for the presence of MN. There were no significant differences in the incidence of MN between RG and CG (p>0.05).

Effect of 2-hydroxyethyl methacrylate on antioxidant responsive element-mediated transcription: a possible indication of its cytotoxicity.

BACKGROUND: The resin monomer 2-hydroxyethyl methacrylate (HEMA) is known to be more cytotoxic than methyl methacrylate (MMA). Using a luciferase reporter assay system, we previously showed that MMA activates the glutathione S-transferase alpha 1 gene (Gsta1) promoter through the anti-oxidant responsive element (ARE). However, it is not known whether HEMA induces ARE-mediated transcription. METHODOLOGY/PRINCIPAL FINDINGS: We further developed the reporter system and studied the concentration-dependent effect of HEMA on ARE enhancer activity. The revised system employed HepG2 cells stably transfected with a destabilized luciferase reporter vector carrying 2 copies of the 41-bp ARE region of Gsta1. In this system, MMA increased ARE activity by 244-fold at 30 mM; HEMA augmented ARE activity at 3 mM more intensely than MMA (36-fold versus 11-fold) and was equipotent as MMA at 10 mM (56-fold activation); however, HEMA failed to increase ARE activity at 30 mM. In HepG2 cells, HEMA detectably lowered the cellular glutathione levels at 10 mM and cell viability at 30 mM, but MMA did not. CONCLUSIONS: These results suggest that the low-concentration effect of HEMA on ARE activity reflects its cytotoxicity. Our reporter system used to examine ARE activity may be useful for evaluating cytotoxicities of resin monomers at concentrations lower than those for which cell viabilities are reduced.

Iodinated glycidyl methacrylate copolymer as a radiopaque material for biomedical applications.

Polymeric biomaterial was synthesized by copolymerizing 50:50 mol% of monomers, glycidyl methacrylate and methyl methacrylate. Iodine atoms were then grafted to the epoxide groups of glycidyl methacrylate units, rendering the copolymer radiopaque. The percentage weight of iodine in the present copolymer was found to be as high as 23%. The iodinated copolymer showed higher glass transition temperature and thermal stability in comparison with unmodified polymer. Radiographic analysis showed that the copolymer possessed excellent radiopacity. The iodinated copolymer was cytocompatible to L929 mouse fibroblast cells. The in vivo toxicological evaluation by intracutaneous reactivity test of the copolymer extracts has revealed that the material was nontoxic. Subcutaneous implantation of iodinated copolymer in rats has shown that the material was well tolerated. Upon explantation and histological examination, no hemorrhage, infection or necrosis was observed. The samples were found to be surrounded by a vascularized capsule consisting of connective tissue cells. The results indicate that the iodinated copolymer is biocompatible and may have suitable applications as implantable materials.

Cytotoxicity of hard and soft denture lining materials.

The cytotoxicity of nine soft and hard lining materials (Mollosil Plus, Ufi Gel SC, Visco-gel, Molloplast-B, GC Tissue Conditioner, Vertex Rapid Simplified, GC Reline Hard, Vertex Self-Curing, Ufi Gel hard C) was evaluated using human gingival fibroblasts (HGFs). Twelve disk samples per lining material were prepared and incubated for 24, 48, 72, and 96 h. Cytotoxicity of each lining material's extract on cultured HGFs was measured using XTT assay. Data were analyzed using one-way ANOVA, post hoc Dunnett's T3 and Bonferroni tests at a significance level of p<0.05. At all incubation periods, all the hard lining materials (Vertex-SC, GC Reline Hard, Vertex-RS, and Ufi Gel hard C) showed cell viability higher than 90%. Among the soft lining materials, although there were no significant differences in cell viability among the different incubation periods for each lining material (p>0.05), autopolymerized acrylic-based GC Tissue Conditioner showed significantly lower cell viability than the other soft lining materials at each incubation period. Among the hard lining materials, there were no significant differences both among the materials and across all incubation periods for each lining material (p>0.05). In conclusion, all soft and hard liners exhibited good biocompatibility regardless of incubation time, except for GC Tissue Conditioner.

Cytotoxicity of newly developed ortho MTA root-end filling materials.

INTRODUCTION: Various materials have been advocated for use as root-end filling materials. The purpose of the present in vitro study was to compare the cytotoxicity of 4 root-end filling materials: glass ionomer cement (GIC; Fuji II, GC Corp, Tokyo, Japan), reinforced zinc oxide-eugenol cement (IRM; Dentsply Tulsa Dental, Tulsa, OK), and 2 types of mineral trioxide aggregate. METHODS: This study used MG-63 cells derived from a human osteosarcoma. To quantitatively evaluate the cytotoxicity of test materials, the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay was used. The cells were exposed to the extracts and incubated. Cell viability was recorded by measuring the optical density of each test well in reference to controls. Each specimen was examined by scanning electron microscopy for the observation of cell morphology. RESULTS: The XTT assay showed that the cell viability of ProRoot MTA (Dentsply Tulsa Dental) was higher than that of GIC and Ortho MTA (BioMTA, Seoul, Republic of Korea) at all time points. IRM showed significantly lower cell viability than the other groups. The scanning electron microscopic analysis revealed that elongated, dense, and almost confluent cells were observed in the cultures of GIC, Ortho MTA, and ProRoot MTA specimens. In contrast, cells on the surface of IRM were rounded in shape, and the numbers and the density of the cells were smaller than that in the other groups. CONCLUSIONS: ProRoot MTA and GIC showed good biocompatibility in this study. However, Ortho MTA showed lower biocompatibility compared with ProRoot MTA and GIC.

Cytotoxicity evaluation of methacrylate-based resins for clinical endodontics in vitro.

This study examines the cytotoxicity of Super-Bond C&B (SB-C&B), Super-Bond RC Sealer (SB-RC), MetaSEAL (Meta), and AH Plus Sealer (AH+). Freshly mixed and set materials (100 mg) were prepared in vitro and placed in cell culture medium (1 mL) for the working time and for 6 h, respectively. L929 cells seeded into 96-well plates at 5,000 cells/well were incubated with the eluted medium (200 µL) for 24 h. Cells cultured with medium alone served as the control. Cytotoxicity was evaluated by MTS assay and analyzed with ANOVA. In the freshly mixed group, the average ± SD (%) for cell viability were 66.0 ± 13.6, 55.5 ± 15.6, 10.6 ± 0.7, and 8.9 ± 2.2 for SB-C&B, SB-RC, Meta, and AH+, respectively. In the set group, the average ± SD (%) for cell viability were 100 ± 21.9, 81.8 ± 38.5, 24.9 ± 7.9, and 23.6 ± 10.0 for SB-C&B, SB-RC, Meta, and AH+, respectively. SB-C&B and SB-RC are less cytotoxic than are Meta and AH+.

Effect of water storage and heat treatment on the cytotoxicity of soft liners.

OBJECTIVE: To evaluate the effect of water storage time on the cytotoxicity of soft liners. METHODS: Sample discs of soft liners Dentusoft, Dentuflex, Trusoft, Ufi-Gel-P and denture base acrylic resin Lucitone-550 were prepared and divided into four groups: GN: No treatment, G24: Stored in water at 37°C for 24 h; G48: Stored in water at 37°C for 48 h, GHW: Immersed in water at 55°C for 10 min. To analyse the cytotoxic effect, three samples of each group were placed in tubes with Dubelcco's Modified Eagle Mediums and incubated at 37°C for 24 h. During this period, the toxic substances were leached to the culture medium. The cytotoxicity was analysed quantitatively by the incorporation of radioactivity (3)H-thymidine checking the number of viable cells (synthesis of DNA). The data were statistically analysed using two-way anova and Tukey's honestly significant difference tests (α = 0.05). RESULTS: Treatments did not reduce the cytotoxicity effect of the soft liners (p > 0.05). It was found that Ufi-Gel-P had a non-cytotoxic effect, Trusoft had a slightly cytotoxic effect, Dentuflex had a moderated cytotoxic effect, Dentusoft alternated between slightly and non-cytotoxic effect, and Lucitone-550 had non-cytotoxic effect when stored in water for 48 h. CONCLUSION: The effect of water storage and the heat treatment did not reduce the cytotoxicity of the soft liners.

Real-time cell analysis of the cytotoxicity of the components of orthodontic acrylic materials on gingival fibroblasts.

INTRODUCTION: The aim of this study was to evaluate the cytotoxicity of 3 orthodontic acrylic materials and 2 manipulation methods. METHODS: The orthodontic acrylic materials Orthocryl EQ (Dentaurum, Ispringen, Germany), Orthoplast (Vertex Dental, Zeist, The Netherlands), and O-80 (Imicryl, Konya, Turkey) were prepared with 2 polymerization methods (doughing and spray on). Totally, 60 cylinders (5 × 2 mm), fabricated by using a different acrylic and method, were divided into 6 groups. Gingival fibroblasts were isolated from gingival connective tissue of systemically healthy subjects. Materials were incubated in Dulbecco's modified eagle's medium culture medium (Biological Industries, Beit Haemek, Israel) for 72 hours according to ISO 10993-5 standards (surface area to volume ratio of the specimen to cell-culture medium: 3 cm(2)/mL). Gingival fibroblasts were maintained with Dulbecco's modified eagle medium containing 10% fetal bovine serum. A real-time cell analyzer (RT-CES, xCELLigence; Roche Applied Science, Mannheim, Germany, and ACEA Biosciences, San Diego, Calif) was used to evaluate cell survival. After seeding 200 µL of the cell suspensions into the wells (20,000 cells/well) of the E-plate 96, gingival fibroblasts were treated with bioactive components released by the acrylic materials (1/1 and 1/2 dilutions) and monitored every 15 minutes for 121 hours. For the proliferation experiments, the statistical analyses used were 1-way analysis of variance (ANOVA) and Tukey-Kramer multiple comparisons tests. RESULTS: There was no significant difference between the cell indexes of the control and study groups for the 1/1 and 1/2 dilutions at 21 and 32 hours. When evaluated at 68 hours, all 1/2 dilutions of acrylic materials showed statistically insignificant differences (P >0.05) except for Orthoplast (P <0.05). But all acrylic materials were different from the control group in the 1/1 dilutions (P <0.001). At 121 hours, all test groups were significantly different from the untreated control group (P <0.001). CONCLUSIONS: The results indicate that the long cycle increased the cytotoxicity of the tested materials, and there was no significant difference between the spray-on and doughing methods on cytotoxicity.

Characterisation and toxicological behaviour of Basic Methacrylate Copolymer for GRAS evaluation.

Basic Methacrylate Copolymer is a fully polymerised cationic copolymer with taste-masking and moisture protection properties. It is used as a pharmaceutical excipient and has potential use as a glazing/coating agent to solid food supplements. This article describes available information on the safety of the substance. Oral administration of radiolabelled copolymer to rats showed the major route of excretion to be via the faeces. Minor absorption may occur at <0.02%. Safety studies revealed no adverse toxicity following repeated administration at up to 2000 mg/kg/day in a sub-chronic study in the rat or 750 mg/kg/day in a sub-acute study in the dog. No reproductive toxicity occurred at up to 1000 mg/kg/day in the rat. The substance shows no evidence of genotoxicity, has low acute toxicity and no irritation or sensitisation potential. As per the FDA approach an ADI of 20 mg/kg bw can be concluded. Daily exposure from use as a food additive is estimated as up to 11.7 mg/kg bw in adults and 13.3 mg/kg bw in children. In view of the high molecular weight of the substance, its lack of absorption and its low toxicity profile, the ADI is deemed adequate.

Methyl methacrylate and respiratory sensitization: a critical review.

Methyl methacrylate (MMA) is a respiratory irritant and dermal sensitizer that has been associated with occupational asthma in a small number of case reports. Those reports have raised concern that it might be a respiratory sensitizer. To better understand that possibility, we reviewed the in silico, in chemico, in vitro, and in vivo toxicology literature, and also epidemiologic and occupational medicine reports related to the respiratory effects of MMA. Numerous in silico and in chemico studies indicate that MMA is unlikely to be a respiratory sensitizer. The few in vitro studies suggest that MMA has generally weak effects. In vivo studies have documented contact skin sensitization, nonspecific cytotoxicity, and weakly positive responses on local lymph node assay; guinea pig and mouse inhalation sensitization tests have not been performed. Cohort and cross-sectional worker studies reported irritation of eyes, nose, and upper respiratory tract associated with short-term peaks exposures, but little evidence for respiratory sensitization or asthma. Nineteen case reports described asthma, laryngitis, or hypersensitivity pneumonitis in MMA-exposed workers; however, exposures were either not well described or involved mixtures containing more reactive respiratory sensitizers and irritants. The weight of evidence, both experimental and observational, argues that MMA is not a respiratory sensitizer.

Prediction of the reduced glutathione (GSH) reactivity of dental methacrylate monomers using NMR spectra - Relationship between toxicity and GSH reactivity.

It has been established that the toxicity of acrylate and methacrylate monomers is driven by their reactivity towards glutathione (GSH). With this relationship, the objective of this study was to predict the GSH reactivity of dental methacrylate monomers, and hence their toxicity, using the (13)C-NMR chemical shifts of beta-carbon (delta(Cbeta)) and the (1)H-NMR shifts of the protons attached to beta-carbon (delta(Ha), delta(Hb)). The different nucleophiles were chosen to compare the different nucleophilic reactions involving acrylate and methacrylate monomers. In conjunction with the use of literature data for monomer/GSH reactivity, significant linear relationships between GSH reactivity (log K) and delta(Cbeta )or delta(Ha )were observed (p<0.001). As for the oral LD(50 )values of some dental dimethacrylates in mice, they were estimated using linear regression curve fitting of GSH reactivity-toxicity response data. Results revealed an acceptable correlation between the oral LD(50 )values of acrylates and methacrylates and GSH reactivity (p<0.05, outlier: HEMA). In conclusion, the present findings suggested that NMR spectra might be useful for predicting the toxicity of dental methacrylates.

In vitro genotoxicity of root canal sealers.

AIM: To evaluate the effect of leakage on differences in genotoxicity of root canal sealers ex vivo according to their main components using two different cytogenetic assays. METHODOLOGY: Six materials of different composition (GuttaFlow, Epiphany, Diaket, IRM, SuperEBA and Hermetic) were tested on human peripheral blood lymphocytes using the comet assay and chromosomal aberration analysis. Prepared materials were eluted in physiological solution for 1 h, 1 day, 5 and 30 days. Thereafter cultures were treated with 8 microg, 4 microg and 2 microg of each sealer. Frequencies of chromatide and chromosome breaks and accentric fragments were determined. Comet assay was used to evaluate primary DNA damage by measuring tail length and tail intensity. Chi-square, Fisher's PLSD (Protected Least Significant Difference) and Kruskall-Wallis non parametric tests were used for statistical analysis. RESULTS: After 1-h elution only the highest dose of Diaket, Hermetic and SuperEBA significantly (P = 0.035, P = 0.048, P = 0.037 respectively) affected the measured cytogenetic parameters. The migration ability of DNA was more strongly affected than induction of chromosomal aberrations. After elutions longer than 24 h none of the tested sealers exhibited a genotoxic effect. CONCLUSION: Under the conditions used in the study all sealers had acceptable biocompatibility in terms of genotoxicity.

Effect of microwave postpolymerization treatment and of storage time in water on the cytotoxicity of denture base and reline acrylic resins.

OBJECTIVES: To evaluate the effect of microwave postpolymerization heat treatment and water storage time on the cytotoxicity of denture base and reline acrylic resins. METHOD AND MATERIALS: Sample disks of 6 acrylic resins were fabricated under aseptic conditions (Kooliner, GC; Tokuyama Rebase II, Tokuyama Dental; New Truliner, Bosworth; Acron MC, GC; Lucitone 550, Dentsply; QC 20, Dentsply). The denture base acrylic resin samples were stored in water for 24 and 48 hours at 37 degrees C. The fabricated samples were further subdivided into 2 groups: (1) samples without heat treatment and (2) samples treated in a microwave. The 3H-thymidine incorporation test was used to determine the cytotoxicity of the materials. The data were statistically analyzed using the incomplete 3-way ANOVA and Tukey HSD tests (P < .05). RESULTS: Microwave postpolymerization heat treatment improved the biocompatibility of Tokuyama Rebase II. Tokuyama Rebase II without heat treatment and Acron MC in both experimental groups were graded as slightly cytotoxic in the group without water storage. The other resins were graded as noncytotoxic. After 24 hours of immersion in water, all materials were graded as noncytotoxic. After water storage for 48 hours, Acron MC without heat treatment and QC 20 in both experimental groups were graded as slightly cytotoxic. Lucitone 550 was graded as noncytotoxic in all experimental groups. CONCLUSION: Microwave irradiation may be considered an alternative to reduce the cytotoxicity of Tokuyama Rebase II. Dental practitioners should choose Lucitone 550 processed with terminal boiling stage.