Cytotoxicity and reactive oxygen species production induced by different co-monomer eluted from nanohybrid dental composites.

BACKGROUND: Safety issues for dental restorative composites are critical to material selection, but, limited information is available to dental practitioners. This study aimed to compare the chemical and biological characteristics of three nanohybrid dental composites by assessing filler particle analysis, monomer degree of conversion (DC), the composition of eluates, and cytotoxicity and reactive oxygen species (ROS) production in fibroblasts. METHODS: Three nanohybrid composites (TN, Tetric N-Ceram; CX, Ceram X Sphere Tec One; and DN, DenFil NX) were used. The size distribution and morphology of the filler particles were analysed using scanning electron microscopy (n = 5). The DC was measured via micro-Raman spectroscopy (n = 5). For the component analysis, methanol eluates from the light-polymerised composites were evaluated by gas chromatography/mass spectrometry (n = 3). The eluates were prepared from the polymerised composites after 24 h in a cell culture medium. A live/dead assay (n = 9) and Water-Soluble Tetrazolium-1 assay (n = 9) were performed and compared with negative and positive controls. The ROS in composites were compared with NC. Statistical significance in differences was assessed using a t-test and ANOVA (α = 0.05). RESULTS: Morphological variations in different-sized fillers were observed in the composites. The DC values were not significantly different among the composites. The amounts of 2-hydroxyethyl methacrylate (HEMA) were higher in TN than DN (p = 0.0022) and triethylene glycol dimethacrylate (TEGDMA) in CX was higher than in others (p < 0.0001). The lowest cell viability was shown in CX (p < 0.0001) and the highest ROS formation was detected in TN (p < 0.0001). CONCLUSIONS: Three nanohybrid dental composites exhibited various compositions of filler sizes and resin components, resulting in different levels of cytotoxicity and ROS production. Chemical compositions of dental composites can be considered with their biological impact on safety issues in the intraoral use of dental restorative composites. CX with the highest TEGDMA showed the highest cytotoxicity induced by ROS accumulation. DN with lower TEGDMA and HEMA presented the highest cell viability.

Preparation and Characterization of Novel Dental Material with High Shear Bond Strength.

HPMA (hydroxypropyl methacrylate) and Bis-GMA (bisphenol A glycerolate dimethacrylate), the main ingredients, and styrene, TEGDMA (triethylene glycol dimethacrylate), BPO (benzoyl peroxide) and camphoroquinone, the photo-initiators, and BHT (butylated hydroxytoluene), the photocatalyst were mixed by different ratios and stirred to investigate the compatibility of dental materials with photoinitiators. The degree of polymerization was checked and determination of the most ideal ratio for photopolymerization was followed by establishing the basic combination of styrene, HPMA, Bis-GMA, BHT, TEGDMA and HEMA. The mixture made in accordance to the predetermined ratio was stirred for 24 hours and was polymerized at a wavelength of 440 to 480 nm for 40 secs. The physical properties of each combination were also evaluated to analyze the functionality of the prepared resin cement. And also, the cytotoxicity of the samples was tested, and as a result, the cell lysis rate was 0% in negative control and 100% in positive control and 0% in S-1 combination which indicates that it does not possess cytotoxicity against cultured cells. It is considered suitable for commercializing and will be highly applicable as high quality dental resin cement.

Qualitative and Quantitative Evaluation of Cytotoxicity of Five Different One-Step Self-Etching Adhesives.

PURPOSE: To qualitatively and quantitatively compare the cytotoxic potentials of five different one-step self-etching adhesives: Prime&Bond One-Select (PB-OS), Optibond All-in-One (OB-AIO), G-Bond (GB), Clearfil Universal Bond (CUB), Single Bond Universal (SBU). MATERIALS AND METHODS: During the first stage of the study, the cytotoxic activities of the test materials were evaluated qualitatively using the direct contact method. In this method, the test materials were placed directly into a monkey kidney epithelial cell culture medium. Reaction zones which occurred in the culture medium were evaluated, in addition to the density and changes in the morphology of the cells. During the second stage, the cytotoxic potential of four different dilutions (1%, 0.1%, 0.01%, 0.001%) of the test materials on L929 rat fibroblast cells was quantitatively evaluated at three different time periods (24 h, 48 h, 72 h) with the MTT tetrazolium-based assay. RESULTS: In the first stage, a zone exceeding 1 cm was observed around or below SBU, CUB, GB and OB-AIO. In PB-OS, the zone borders were approximately 1 cm. In the second stage after the MTT assay, CUB was the most cytotoxic after 24 h, GB and SBU after 48 h, and OB-AIO after 72 h. CONCLUSION: All adhesives tested showed different degrees of cytotoxicity, which statistically significantly increased with dose. Changes were seen related to time.

Cytotoxic Effects of One-step Self-etching Dental Adhesives on Human Periodontal Ligament Fibroblasts In Vitro.

PURPOSE: To evaluate the potential cytotoxic effects of four one-step self-etching dental adhesives [Adper Easy One (AEO), iBond (IB), Clearfil S³ Bond (CSB), and G-Bond (GB)] on cultured human periodontal ligament fibroblasts. MATERIALS AND METHODS: Cured adhesives were immersed in complete DMEM or deionized water and maintained at 37°C for 24 h, followed by sterilization. The deionized water-based extract was used for Fourier transform infrared spectroscopy analysis. The DMEM-based extract was diluted into various concentrations for cytotoxicity tests. The viability, integrity, and apoptosis of cultured human periodontal ligament fibroblasts upon treatment with the extracts were determined using the CCK-8 assay, microscopy, and flow cytometry. RESULTS: All of the four adhesives induced cell viability loss, cell morphology alteration, and cell death. GB showed the greatest cytotoxicity by inducing cell apoptosis and necrosis, while IB had the weakest cytotoxic effect on the cultured cells. CONCLUSION: All tested dental adhesives have significant adverse effects on cell viability. Therefore, precautions should be taken to protect the periodontal tissues when dental adhesives are applied in the clinic.

BisGMA-induced cytotoxicity and genotoxicity in macrophages are attenuated by wogonin via reduction of intrinsic caspase pathway activation.

Bisphenol-A-glycidyldimethacrylate (BisGMA) is a frequently used monomer in dental restorative resins. However, BisGMA could leach from dental restorative resins after polymerization leading to inflammation in the peripheral environment. Wogonin, a natural flavone derivative, has several benefits, such as antioxidative, anti-inflammatory and neuroprotective properties. Pretreatment of macrophage RAW264.7 cells with wogonin inhibited cytotoxicity which is induced by BisGMA in a concentration-dependent manner. BisGMA induced apoptotic responses, such as redistribution of phosphatidylserine from the internal to the external membrane and DNA fragmentation, were decreased by wogonin in a concentration-dependent manner. In addition, BisGMA-induced genotoxicity, which detected by cytokinesis-blocked micronucleus and single-cell gel electrophoresis assays, were inhibited by wogonin in a concentration-dependent manner. Furthermore, wogonin suppressed BisGMA-induced activation of intrinsic caspase pathways, such as caspases-3 and -8. Parallel trends were observed in inhibition of caspase-3 and -8 activities, apoptosis, and genotoxicity. These results indicate wogonin suppressed the BisGMA-induced apoptosis and genotoxicity mainly via intrinsic caspase pathway in macrophages.

Transdentinal cytotoxicity of resin-based luting cements to pulp cells.

OBJECTIVES: The aim of this study was to evaluate the transdentinal cytotoxicity of components released from different resin-based luting cements to cultured MDPC-23 odontoblast-like cells and human dental pulp cells (HDPCs). MATERIALS AND METHODS: Artificial pulp chamber (APC)/dentin disc sets were distributed into four groups according to the materials tested (n = 10), as follows: G1, control (no treatment); G2, resin-modified glass-ionomer cement (RelyX Luting 2); G3, self-adhesive resin cement (RelyX U200); and G4, conventional resin cement (RelyX ARC). The materials were applied to the occlusal surfaces (facing up) of the dentin discs adapted to the APCs. The pulpal surfaces of the discs were maintained in contact with culture medium. Then, an aliquot of 400 µL from the extract (culture medium + resin-based components that diffused through dentin) of each luting cement was applied for 24 h to HDPCs or MDPC-23 cells previously seeded in wells of 24-well plates. Cell viability analysis was performed by the MTT assay (1-way ANOVA/Tukey test; α = 5 %). RESULTS: For MDPC-23 cells, RelyX ARC (G4) and RelyX Luting 2 (G2) caused greater reduction in cell viability compared with the negative control group (P < 0.05). Only the HDPCs exposed to RelyX ARC (G4) extract showed a tendency toward viability decrease (9.3 %); however, the values were statistically similar to those of the control group (G1) (P > 0.05). CONCLUSIONS: In accordance with the safe limits of ISO 10993-5:1999 (E) recommendations, all resin-based luting cements evaluated in this study can be considered as non-toxic to pulp cells. CLINICAL RELEVANCE: Cytotoxicity of resin-based luting cements is material-dependent, and the different protocols for the application of these dental materials to dentin may interfere with their cytotoxicity.

Effect of dentin bonding agent diffusing through dentin slices on the reactive oxygen species production and apoptosis of pulpal cells.

BACKGROUND/PURPOSE: Dentin bonding agents (DBAs) are cytotoxic to dental pulp cells. This study aimed to evaluate the effects of three DBAs (Optibond Solo Plus, Op; Clearfil SE Bond, SE; and Xeno III, Xe) after diffusion through 0.2-mm or 0.5-mm dentin slices on reactive oxygen species (ROS) production and apoptosis in dental pulp cells. METHODS: The amounts of DBAs diffusing through 0.2-mm or 0.5-mm dentin slices were quantified using a UV-Vis spectrophotometer. The effects of diffused DBAs on ROS production and viability of dental pulp cells were investigated using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay on Days 1 and 2. Flow cytometric analysis and double staining of treated dental pulp cells with Annexin V-fluorescein isothiocyanate (V-FITC) and propidium iodide (PI) were performed on Day 2. RESULTS: Xe showed greatest diffusion through dentin slices after 8-hour period, followed by SE and Op. Dental pulp cells produced a lesser amount of ROS, when treated with DBAs diffusing through a 0.5-mm dentin slice than through a 0.2-mm dentin slice for the same period of time. A small proportion of cells were TUNEL-positive after treatment with any of the three diffused DBAs. Annexin V-FITC/PI staining identified apoptotic cells; cell survival was higher in those cells treated with DBAs diffusing through a 0.5-mm dentin slice than through a 0.2-mm dentin slice. CONCLUSION: The three DBAs after diffusion through 0.2- or 0.5-mm dentin slice still exhibit cytotoxicity to dental pulp cells. However, the 0.5-mm dentin slice is found to be a better barrier than the 0.2-mm dentin slice to protect dental pulp cells from DBA-induced cytotoxicity.

The effects of cytotoxicity and genotoxicity induced by 2,2-bis[4-(acryloxypropoxy)phenyl]propane via caspases in human gingival fibroblasts.

The toxicity of dental materials has raised public concern over the past years. One of the most commonly used methacrylic monomers for building the three-dimensional structure of the dental resin composites is 2,2-bis[4-(acryloxypropoxy)phenyl]propane (BAPP). The purpose of this study is to evaluate the potential toxicological implication of BAPP on human gingival fibroblasts (HGFs). Flow cytometric, fluorometric, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assays were used to detect the mode of cell death, caspase activities, and cell viability, respectively. In addition, alkaline single-cell gel electrophoresis (COMET) and cytokinesis block micronucleus (MN) assays were applied to evaluate the genotoxicity. According to the results BAPP demonstrated a cytotoxic effect on HGFs in a dose- and time-dependent manner. With increasing concentrations of BAPP, the mode of cell death shifted from apoptosis to necrosis, and the activities of caspases 3, 8, and 9 were also significantly induced. Moreover, a dose-related increase in the number of micronucleus and DNA strand breaks hinted at the expression of genotoxicity by BAPP. In conclusion, the results gathered from this study had demonstrated that BAPP-induced cytotoxicity and genotoxicity on HGFs were mediated by DNA damage and the activation of caspases 3, 8, and 9.

In vitro detection of DNA damage in human leukocytes induced by combined effect of resin composites and adhesive systems.

PURPOSE: To simultaneously evaluate the genotoxicity of dental composites and adhesive systems in vitro using a cytogenetic assay, with respect to the influence of composite shade. METHODS: Genotoxicity assessment was carried out in human peripheral blood leukocytes using the comet assay. Three resin composite materials, two microhybrids and one nano-hybrid, in shade A1 and A3.5 were used with manufacturer-recommended four adhesive systems. Cultures were treated for 48 hours with samples after elusion for 1 hour, 1 day, 7 days or 30 days, in two different concentrations (4.16 mg/mL, 8.33 mg/mL). Kruskall-Wallis test was used for the statistical analysis (alpha = 0.05). RESULTS: For combinations of micro-hybrid composite (A3.5) with two self-etch adhesives (16.1 +/- 5.50 and 16.2 +/- 9.52) after exposure to samples eluted for 1 day, the incidence of primary DNA damage was significantly higher than for the corresponding negative control (14.7 +/- 2.85). Genotoxicity was also higher after treatment with samples eluted for 1 hour (15.3 +/- 4.70) and 1 day (15.3 +/- 9.10), comprised of nano-hybrid composite (A1) with self-etch adhesive in relation to the control (13.1 +/- 1.70). There was no clear trend of increased DNA damage in material combinations with darker shades of composites. Material composition and higher material concentrations showed greater influence on the genotoxicity.

Toxicity and cytokine release from human dental pulp stem cells after exposure to universal dental adhesives cured by single peak and polywave LEDs.

OBJECTIVES: to assess the impact of universal adhesives, cured with single-peak and polywave LEDs, on the metabolic activity and cytokine release of human dental pulp stem cells (hDPSCs). In addition, analyze the degree of conversion (DC) of the adhesives cured with the different LEDs. METHODS: Discs (5 mm diameter, 1 mm thick) were prepared using three universal adhesives: Single Bond Universal (SBU, 3 M ESPE), Optibond Universal (OBU, Kerr), and Zipbond Universal (ZBU, SDI). These discs were cured for 40 s using a single-peak (DeepCure, 3 M ESPE) or a polywave light-emmiting diode (LED) curing unit (Valo Grand, Ultradent). After 24 h, the specimens were placed in 24-well culture plates, each containing 1 mL of culture medium for 24 h. hDPSCs (1.8 ×104) were seeded in 96-well plates and allowed to grow for 24 h. Subsequently, the cells were exposed to the extracts (culture medium containing eluates from the adhesive discs) for an additional 24 h. Cells not exposed to the extracts were used as a control group. The mitochondrial metabolism was assessed using the MTT assay and the cytokine release evaluated through MAGPIX. The degree of conversion of the adhesives was analyzed using FTIR (n = 5). The results were analyzed by ANOVA two-way and Tukey's test. RESULTS: OBU and ZBU eluates caused a statistically significant reduction in mitochondrial metabolism, regardless of the LED used, indicating their cytotoxicity. In contrast, SBU did not significantly affect the MTT results, resembling the control group. A higher release of cytokines IL-1, IL-6, IL-10, and TNF-α were found in association to ZBU. SBU, on the other hand, increased the release of IL-8. OBU did not influenced the cytokine release. SBU presented the higher DC, while OBU and ZBU had similar DC, lower than SBU. SIGNIFICANCE: In conclusion, universal adhesives exhibit toxicity towards hDPSCs, but the extent of toxicity varies depending on the adhesive material. ZBU was associated with increased cytokine release, particularly pro-inflammatory mediators, from hDPSCs. The different LEDs did not influenced the cytotoxicity of the evaluated adhesives.

Reproductive toxicity evaluation of the dental resin monomer bisphenol a glycidyl methacrylate (CAS 1565-94-2) in mice.

The reproductive toxicity potential of the dental resin monomer bisphenol A glycidyl methacrylate (BisGMA; CASRN 1565-94-2) was investigated in male and female Crl: CD1(ICR) mice, 4 dosage groups, and 25 mice/sex/group. Formulations of BisGMA (0, 0.008, 0.08, or 0.8 mg/kg/d) in 0.8% ethanol in deionized water were intubated once daily beginning 28 days before cohabitation and continuing through mating (males) or through gestation day 17. The following parameters were evaluated: viability, clinical signs, body weights, estrous cyclicity, necropsy observations, organ weights, sperm concentration/motility/morphology, cesarean sectioning and litter observations, and histopathological evaluation of select tissues. No deaths or clinical signs related to BisGMA occurred. No significant changes in male and female body weights and body weight gains were recorded at any of the administered dosages of BisGMA. All mating and fertility parameters, and all litter and fetal data, were considered to be unaffected by dosages of BisGMA as high as 0.8 mg/kg/d. Gross or histopathologic tissue changes attributable to the test article were not observed. Reproductive and developmental no observed effect levels (NOAELs) for BisGMA were 0.8 mg/kg/d, the highest dose tested. Comparison of this NOAEL value to published probabilistic estimates of human BisGMA exposure from dental products suggests a margin of safety of at least 280- to nearly 2000-fold. Under the conditions of this study, BisGMA is not a reproductive toxicant.

[Biocompatibility of polymer-bioglass cement Cortoss®: in vitro test with the MG63 cell model]. / Biokompatibilität von Polymer-Glaskeramik-Zement Cortoss®: In-vitro-Testung mit dem MG63-Zell-Modell.

BACKGROUND: Polymethylmethacrylate (PMMA) cement has been used for fixation of joint replacements for more than 50 years and cement augmentation of vertebrae has become a popular procedure since the first description in 1987. New cements have now been developed which are better suited to the requirements of minimally invasive application techniques for vertebral bodies. The combination of good mechanical properties and biocompatibility is the concern of present research. This study compared the features of a polymer-bioglass cement with a calcium phosphate cement used for vertebral augmentation. METHODS: The human osteoblast-like cell culture MG63 was used to study the polymer-glass ceramic cement Cortoss® and the hydroxyapatite cement Kyphos®. Every 24 h for 5-6 days a defined volume of the culture medium was harvested in the presence of the bone cements and added to 16 cell cultures for each time period. The viability of cells was determined photometrically at 550 nm with the MTT assay and cell morphology was studied using light and electron microscopy. RESULTS: In the presence of the calcium phosphate cement an early and small reduction of cell activity was found compared with the controls. At the end of 1 week the viability parameter improved nearly reaching the control level. Electron microscopy showed crystals with a 3-dimensional shape. The cell cultures with Cortoss® showed no cellular activity and the microscopic examinations were negative. This effect was not different at days 1-5 after polymerization of the cement. CONCLUSIONS: The calcium phosphate cement studied showed a good biocompatibility and allowed morphological signs of apatite formation. At least within the first 5 days the polymer-glass ceramic cement showed a reasonable cytotoxic effect. There was no sign of recovery of cell function within that period. The biocompatibility of the polymer-glass ceramic cement appeared significantly worse compared with the calcium phosphate cement. An ideal composition of biomechanical properties and biocompatibility has not been achieved so far.

Influence of different photo-activation distances on cytotoxicity of a dental adhesive model resin.

AIM: This study evaluated the cytotoxicity of a dental bonding model resin (DBMR) submitted to different photo-activation distances. METHODS: A monomer mixture based on Bis-GMA and HEMA was used to assess the cytotoxicity in a mouse fibroblast-cell line. To promote different photo-activation distances glass slides were interposed between DBMR surface and halogen light curing unit (LCU) tip. Afterwards, the specimens were immersed in RPMI culture medium for 24 h to obtain extracts. The extracts were incubated in contact with the cells for 24 h. Finally, an MTT colorimetric assay was used to assess the cytotoxicity. The cell viability data (absorbance) were analyzed by one way ANOVA followed by Tukey's test (P<0.05). RESULTS: The light output decreased according to the increase in the number of glass slides between the halogen LCU tip and DBMR surface. Yet, the distance between the tip of the curing light system and the specimens had significant influence on the cytotoxicity. All extracts produced by groups submitted to different photo-activation distances showed cytotoxic effect after 24h of incubation. CONCLUSION: The photo-activation distance and the interposition of glass slides between LCU tip and DBMR was shown to play an important role in the cytotoxic effect.

The upregulation of tumour necrosis factor-α and surface antigens expression on macrophages by bisphenol A-glycidyl-methacrylate.

AIM: To evaluate the expression of tumour necrosis factor-α and surface antigens by bisphenol A-glycidyl-methacrylate (BisGMA) on murine macrophage cell line RAW264.7. METHODOLOGY: Cytotoxicity was measured by tetrazolium bromide reduction assay. Tumour necrosis factor (TNF)-α was analysed by enzyme-linked immunosorbent assay. Cell surface antigens were investigated by flowcytometry. Statistical analyses were performed using anova followed by the Bonferroni's t-test for multigroup comparisons. RESULTS: BisGMA exhibited cytotoxicity to RAW264.7 in a dose-dependent manner (P < 0.05) during 2-h incubation period. BisGMA was found to increase TNF-α secretion in a dose-dependent manner (P < 0.05). In addition, CD11, CD14, CD45, CD54, CD40, CD80, and MHC II were significantly stimulated by BisGMA in a dose-dependent manner (P < 0.05). However, MHC I expression was not affected by BisGMA (P > 0.05). CONCLUSIONS: Taken together, the ability of macrophages to induce an appropriate immune response when exposed to BisGMA has the potential to upregulate TNF-α production and expression of surface antigens.

The role of DNA damage and caspase activation in cytotoxicity and genotoxicity of macrophages induced by bisphenol-A-glycidyldimethacrylate.

AIM: To evaluate the potential toxicological implications of BisGMA on murine macrophage cell line RAW264.7. METHODOLOGY: Lactate dehydrogenase release, flow cytometry, Western blot and fluorometric assays were used to detect cell viability, mode of cell death and caspase activities, respectively. In addition, alkaline single-cell gel electrophoresis and cytokinesis-block micronucleus assays were applied to detect genotoxicity. Statistical analyses were performed using anova followed by the Bonferroni's t-test for multi-group comparisons test. RESULTS: BisGMA demonstrated a cytotoxic effect on RAW264.7 cells in a dose-dependent and a time-dependent manner (P < 0.05). BisGMA was found to induce two modes of cell death. The mode of cell death changed from apoptosis to necrosis as the concentrations of BisGMA elevated. Caspase-3, caspase-8 and caspase-9 activities were significantly induced by BisGMA in a dose-dependent manner (P < 0.05). Moreover, BisGMA exhibited genotoxicity via a dose-related increase in the numbers of micronucleus and DNA strand breaks (P < 0.05). CONCLUSIONS: Cytotoxicity and genotoxicity induced by BisGMA are mediated by DNA damage and caspase activation.

Oxidative stress and cytotoxicity generated by dental composites in human pulp cells.

Dental composites are a source of residual monomers that are released into the oral environment. Since monomers act on cultured cells through reactive oxygen species (ROS), we hypothesized that composites generate ROS associated with cytotoxicity. Human pulp-derived cells were exposed to extracts of methacrylate-based materials including triethylene glycol dimethacrylate and 2-hydroxyethyl methacrylate-free composites (Tetric Ceram, Tetric EvoCeram, els, els flow, Solitaire 2) and a silorane-based composite (Hermes III). The materials were polymerized in the presence and absence of a polyester film and then extracted in culture medium. The generation of ROS was measured by flow cytometry, and cytotoxicity was determined as well. Methacrylate-based composites reduced cell survival but varied in efficiency. Undiluted extracts of Solitaire 2 specimens prepared in the absence of a polyester film reduced cell survival to 26% compared with untreated cultures. Cytotoxicity was reduced when specimens were covered with a polyester film during preparation. Cytotoxicity of the composites was ranked as follows: Solitaire 2 >> els flow > Tetric Ceram = Tetric EvoCeram = els > Hermes III. The generation of ROS followed the same pattern as detected with cytotoxic effects. A positive correlation was found between ROS production and cell survival caused by extracts made from materials not covered with a polyester film. These findings suggest that components released from composites affect cellular signaling networks through ROS formation. Regenerative and reparative capacities of the dentine-pulp complex may be impaired by biologically active resin monomers released from composite restorations.

Bisphenol A-glycidyl methacrylate induces a broad spectrum of DNA damage in human lymphocytes.

Bisphenol A-glycidyl methacrylate (BisGMA) is monomer of dental filling composites, which can be released from these materials and cause adverse biologic effects in human cells. In the present work, we investigated genotoxic effect of BisGMA on human lymphocytes and human acute lymphoblastic leukemia cell line (CCRF-CEM) cells. Our results indicate that BisGMA is genotoxic for human lymphocytes. The compound induced DNA damage evaluated by the alkaline, neutral, and pH 12.1 version of the comet assay. This damage included oxidative modifications of the DNA bases, as checked by DNA repair enzymes EndoIII and Fpg, alkali-labile sites and DNA double-strand breaks. BisGMA induced DNA-strand breaks in the isolated plasmid. Lymphocytes incubated with BisGMA at 1 mM were able to remove about 50% of DNA damage during 120-min repair incubation. The monomer at 1 mM evoked a delay of the cell cycle in the S phase in CCRF-CEM cells. The experiment with spin trap-DMPO demonstrated that BisGMA induced reactive oxygen species, which were able to damage DNA. BisGMA is able to induce a broad spectrum of DNA damage including severe DNA double-strand breaks, which can be responsible for a delay of the cell cycle in the S phase.

Induction of DNA strand breaks by dental composite components compared to X-ray exposure in human gingival fibroblasts.

The toxicity of dental composites has been attributed to the release of residual monomers from polymerized resin-based composites due to degradation processes or incomplete polymerization. Some of these eluted substances have a genotoxic potential. We tested the hypothesis that realistic concentrations (and/or worst case concentrations/situations) of bisphenol-A-glycidyldimethacrylate (BisGMA), triethyleneglycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) found in elution experiments can cause DNA strand breaks in human gingival fibroblasts (HGF). Such DNA damage was compared with that resulting from ionizing radiation coming from natural sources, dental radiography or tumor therapy. TEGDMA, HEMA and MMA did not induce DNA strand breaks at concentrations of up to 10 mM. About 24 h after incubation with 0.25 mM BisGMA, significantly more DNA strand breaks were found in HGF compared to controls. DNA strand breaks caused by 0.25 mM BisGMA, correspond to DNA strand breakage caused by irradiation with 4 Gy, only used in the high single-dose irradiation tumor therapy. But 0.25 mM BisGMA is more than 100-fold higher than that concentration found in worst case calculations. Therefore, our data did not support our hypothesis.

Protective effect of chitosan oligosaccharide lactate against DNA double-strand breaks induced by a model methacrylate dental adhesive.

BACKGROUND: Monomers of methacrylates used in restorative dentistry have been recently reported to induce DNA double-strand breaks (DSBs) in human gingival fibroblasts (HGFs) in vitro. Because such monomers may penetrate the pulp and oral cavity due to the incompleteness of polymerization and polymer degradation, they may induce a similar effect in vivo. DSBs are the most serious type of DNA damage and if misrepaired or not repaired may lead to mutation, cancer transformation and cell death. Therefore, the protection against DSBs induced by methacrylate monomers released from dental restorations is imperative. MATERIAL/METHODS: We examined the protective action of chitosan oligosaccharide lactate (ChOL) against cytotoxic and genotoxic effects induced by monomers of the model adhesive consisting of 55% bisphenol A-diglycidyl dimethacrylate (Bis-GMA) and 45% 2-hydroxyethyl methacrylate (HEMA). We evaluated the extent of DSBs by the neutral comet assay and the phosphorylation of the H2AX histone test. RESULTS: ChOL increased the viability of HGFs exposed to Bis-GMA/HEMA as assessed by flow cytometry. ChOL decreased the extent of DSBs induced by Bis-GMA/HEMA as evaluated by neutral comet assay and phosphorylation of the H2AX histone. ChOL did not change mechanical properties of the model adhesive, as checked by the shear bond test. Scanning electron microscopy revealed a better sealing of the dentinal microtubules in the presence of ChOL, which may protect pulp cells against the harmful action of the monomers. CONCLUSIONS: ChOL can be considered as an additive to methacrylate-based dental materials to prevent DSBs induction, but further studies are needed on its formulation with the methacrylates.