Biocompatibility of bulk-fill resins in vitro.

OBJECTIVES: This study aims to evaluate the cytotoxicity and genotoxicity of three different extracts obtained from Filtek™ One Bulk Fill, Tetric Evoceram® Bulk Fill and Coltene Fill-Up! resins. MATERIALS AND METHODS: The cytotoxicity was determined on 3T3 fibroblast cells using the MTT and crystal violet assays. The genotoxicity was determined using a cytokinesis-block micronucleus assay. RESULTS: The cytotoxicity of the resin extracts on 3T3 mouse fibroblasts was found to be dose-dependent with both the MTT and crystal violet assays. Extracts concentrated above 1% were cytotoxic according to the MTT assay. The Filtek™ One Bulk Fill, Tetric Evoceram® Bulk Fill, and Coltene Fill-Up! resins reached the LD50 at concentrations of 60%, 50%, and 20%, respectively, and showed genotoxicity rates that were 2-5 times, 3-8 times, and 4-15 times higher than the negative control, respectively. CONCLUSIONS: Coltene Fill-Up! resin extracts were the most cytotoxic and genotoxic, followed by Tetric Evoceram® Bulk Fill and Filtek™ One Bulk Fill. CLINICAL RELEVANCE: The analyzed bulk-fill resins showed differences in in vitro biocompatibility, and the Filtek™ One Bulk Fill was found to be the safest for clinical use.

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.

Effects of nanohybrid flowable resin-based composites on fibroblast viability using different light-curing units.

PURPOSE: To investigate the in vitro cytotoxic effects of Bis-GMA-containing and Bis-GMA-free flowable resin-based composites (RBCs) on primary human gingival fibroblast cells (hGFc) using direct and indirect curing methods and three different light-curing units (LCUs). MATERIALS AND METHODS: Cells were isolated and cultured in vitro in 24-well plates. The plates were divided into treatment (cells with RBC), control (cells only), and blank (media only) groups. In the treatment groups, two types of nanohybrid flowable RBCs were used: Bis-GMA-free and Bis-GMA groups. Each treatment group was subdivided according to the curing method, i.e., direct curing (RBC was injected into the wells and cured directly on the attached cells) and indirect curing (the samples were pre-cured outside of the well plate and then added to the well plate with cells). To vary the LCU, the subgroups were further divided into three groups: multiple-emission peak light-emitting diode, single-emission peak light-emitting diode, and quartz-tungsten-halogen units. Curing was conducted for 20 seconds. The hGFc cytotoxicity was evaluated via 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay after 24, 48, and 72 hours of culturing. RESULTS: The MTT assay results showed that both RBCs were significantly cytotoxic toward hGFc compared to the control group (p < 0.0001). The Bis-GMA group was significantly more cytotoxic to the cells compared to the Bis-GMA-free group. In addition, the curing method and time interval affected cell viability regardless of the LCU used. CONCLUSION: The Bis-GMA flowable RBC and direct curing method had the highest cytotoxic effects on hGFc regardless of the LCU used. Careful selection of flowable RBCs and proper curing techniques are required to decrease the cytotoxic effects on hGFc and improve the clinical handling of oral tissues.

Influence of the self-adhering strategy on microhardness, sorption, solubility, color stability, and cytotoxicity compared to bulk-fill and conventional resin composites.

OBJECTIVES: To analyze and compare, in vitro, the microhardness, sorption, solubility, color stability, and cytotoxicity of three types of resin composites: self-adhesive (SARC) (Dyad Flow (DF)/Kerr), bulk-fill (Filtek Bulk Fill Flow (FBF)/3 M ESPE), and conventional (Filtek Z350XT Flow (Z350)/3 M ESPE). MATERIALS AND METHODS: Thirty cylindrical specimens were prepared using a split metal mold (15 mm × 1 mm), divided into 3 groups (n = 10) according to the material used. Vickers hardness (VH) was calculated from three indentations (300gf/15 s) per specimen. The sorption and solubility were measured according to the ISO 4049:2009 specification after storing in distilled water for 7 days. The color of each resin composite was measured using a portable digital spectrophotometer according to the CIELAB system. After a 7-day immersion in coffee, the color variation (∆E) was calculated. Following the ISO 10993:2012, the cytotoxicity in Vero cells was evaluated through the MTT assay. The results were analyzed using the Kruskal-Wallis test to compare the studied groups. The Wilcoxon test was used to compare the assessments in each studied group. For cytotoxicity analysis, the data were compared by the ANOVA test (α = 0.05). RESULTS: DF showed the lowest VH (28.67), highest sorption (0.543 µg/mm3) and solubility (1.700 µg/mm3), and higher ∆E after 7 days of coffee immersion (p = 0.008). The resin composites studied were considered non-cytotoxic. CONCLUSIONS: The SARC presented inferior mechanical and physical-chemical properties than bulk-fill and conventional resin composites, with comparable cytotoxicity against Vero cells. CLINICAL RELEVANCE: The simplification of the clinical protocol of SARC can minimize the number of possible failures during the restorative technique. However, considering their inferior physical and mechanical properties, their coverage with materials of higher mechanical properties and physical-chemical stability should be considered.

Effect of Finishing-Polishing Procedures on Cytotoxicity of Resin-Based Restorative Materials via Real-Time Cell Analysis.

OBJECTIVE: The aim of this study was to evaluate the effect of finishing and polishing procedures of compomer and bulk-fill composite resins on cytotoxicity against human gingival fibroblasts by xCELLigence analysis. STUDY DESIGN: Filtek™ Bulk Fill composite and Dyract XP compomer were used. After curing, the specimens were randomly divided into two groups and finishing-polishing procedures were applied to one group; no finishing-polishing procedures were applied to the other group. For the first time in this study, pure gold samples were prepared with the same weight and base area as the test specimens and the wells containing the pure gold samples were determined as the control group. xCELLigence system was used to assess the response of the human gingival fibroblasts after exposure to test specimens. Measurements were recorded for 72 hours after adding specimens. RESULTS: Finishing and polishing procedures caused a significant increase in cell viability of Dyract XP compomer samples at all time periods; the percentage of cell viability reached above 70% after finishing and polishing procedures. However, significant effects were not observed in Filtek™ Bulk Fill composite samples at any time period. CONCLUSION: Finishing and polishing procedures play an essential role in increasing the biocompatibility of Dyract XP compomer. It is recommended to apply finishing and polishing procedures even though a smooth surface may be obtained in restorations with matrix strips.

The cytotoxic and oxidative effects of restorative materials in cultured human gingival fibroblasts.

The aim of this study was to evaluate the cytotoxic and oxidative effects of the most commonly used dental restorative materials on human gingival fibroblast cells (HGFCs). HGFCs were obtained from healthy individuals. The tested restorative materials were a microhybrid resin based composite, a compomer resin, a glass ionomer cement, and an amalgam alloy. One hundred eight cylindirical samples, 10 mm in diameter and 2 mm in height, were prepared according to ISO 10993-12:2002 specifications (n = 9 in the tested subgroups). Freshly prepared and aged samples in artificial saliva at 37 °C (7 and 21 d) were placed into well plates and incubated. Wells without dental materials were constituted as the control group. After 72 h incubation period, cytotoxicity was determined using the neutral red (NR) assay. Oxidative alterations were assessed using total antioxidant capacity (TAC) and total oxidant status (TOS) assay kits. Data were analyzed using the ANOVA and LSD post hoc tests. All tested materials led to significant decreases in the cell viability rates (33-73%) compared to the control group. Glass ionomer and resin composite were found to be more cytotoxic than amalgam alloy and compomer. The highest TAC level was observed in glass ionomer after seven-day aging and these changes prevented an increase in TOS levels. Increases in TAC levels after seven-day aging in all groups exhibited significant differences with freshly prepared samples (p < 0.05). In all material groups, TOS levels of freshly prepared samples differed statistically and significantly from samples aged for 7 and 21 d (p < 0.05). The data obtained suggested that all the tested materials exhibited cytotoxic and pro-oxidant features. Freshly prepared samples caused higher TOS levels. However, oxidant status induced by materials decreased over time.

Cytotoxicity of contemporary resin-based dental materials in contact with dentin.

In this study, the cytotoxicity of different combinations of contemporary resin-based restoratives (adhesives, composites, luting agents) against human keratinocytes (HaCaT) was evaluated under two conditions, whether materials were applied to dentin or not. Adhesives (3-step etch-and-rinse/3ER: OptiBond FL; 2-step self-etch/2SE Clearfil SE Bond; Single Bond Universal/UNI), composites (conventional composite resin/CCR: Filtek Z350XT; flowable/FCR: Filtek Z350XT Flow; self-adhesive composite resin/SACR: Dyad Flow), and luting agents (conventional luting agent/CLA: Variolink-II; self-adhesive luting agent/SLA: RelyXU200) were combined according to their clinical use. Eluates from polymerized specimens applied to dentin were placed in contact with cells grown for 1 and 7 d. The controls were defined by cells without material contact. Cell viability was determined using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)] assay. C=C conversion was investigated using Fourier-transform infrared spectroscopy. After 1 d of incubation, when dentin was not present, 2SE yielded the highest cell viability, whereas 3ER, UNI, and SACR showed higher cell viability in the presence of dentin. After 7 d, when dentin was absent, 2SE and CLA achieved significantly higher cell viability. The presence of dentin resulted in a drastically higher cell viability for all materials, except 2SE and CLA. UNI had the lowest C=C conversion. The presence of dentin was a significant factor, which resulted in higher cell viability than what was seen for the material specimens per se. All materials resulted in a lower viability of HaCaT than what was seen under the no-material control conditions, with effects mainly limited to the first 24 h.

Bulk Fill Composites Have Similar Performance to Conventional Dental Composites.

The aim of the study was to perform comprehensive characterization of two commonly used bulk fill composite materials (SDR Flow (SDR) and Filtek™ Bulk Fill Flowable Restorative (FBF) and one conventional composite material (Tetric EvoCeram; TEC). Eleven parameters were examined: flexural strength (FS), flexural modulus (FM), degree of conversion, depth of cure, polymerisation shrinkage (PS), filler particle morphology, filler mass fraction, Vickers hardness, surface roughness following simulated toothbrush abrasion, monomer elution, and cytotoxic reaction of human gingival fibroblasts, osteoblasts, and cancer cells. The degree of conversion and depth of cure were the highest for SDR, followed by FBF and TEC, but there was no difference in PS between them. FS was higher for bulk fill materials, while their FM and hardness were lower than those of TEC. Surface roughness decreased in the order TEC→SDR→FBF. Bisphenol A-glycidyl methacrylate (BisGMA) and urethane dimethacrylate were found in TEC and FBF eluates, while SDR released BisGMA and triethylene glycol dimethacrylate. Conditioned media accumulated for 24h from FBF and TEC were cytotoxic to primary human osteoblasts. Compared to the conventional composite, the tested bulk fill materials performed equally or better in most of the tests, except for their hardness, elastic modulus, and biocompatibility with osteoblasts.

Assessing the effect of triethyleneglycol dimethacrylate on tissue repair in 3D organotypic cultures.

Leachables from dental restoratives induce toxicity in gingival and pulp tissues and affect tissue regeneration/healing. Appropriate testing of these materials requires a platform that mimics the in vivo environment and allows the architectural self-assembly of cells into tissue constructs. In this study, we employ a new 3D model to assess the impact of triethyleneglycol dimethacrylate (TEGDMA) on early organization and advanced recruitment/accumulation of immortalized mouse gingival fibroblasts (GFs) and dental papilla mesenchymal cells (DPMCs) in extracellular matrix. We hypothesize that TEGDMA (1) interferes with the developmental architecture of GFs and DPMCs, and (2) inhibits the deposition of mineral. To test these hypotheses, GFs and DPMCs were incubated with the soluble TEGDMA at concentrations (0-2.5) mmol/L. Diameter and thickness of the constructs were determined by microscopic analysis. Cell differentiation was assessed by immunocytochemistry and the secreted mineral detected by alizarin-red staining. TEGDMA interfered with the development of GFs and/or DPMCs microtissues in a dose-dependent manner by inhibiting growth of inter-spherical cell layers and decreasing spheroid size (four to six times). At low/moderate TEGDMA levels, GFs organoids retained their structures while reducing thickness up to 21%. In contrast, at low TEGDMA doses, architecture of DPMC organoids was altered and thickness decreased almost twofold. Overall, developmental ability of TEGDMA-exposed GFs and DPMCs depended on TEGDMA level. GFs constructs were more resistant to structural modifications. The employed 3D platform was proven as an efficient tool for quantifying the effects of leachables on tissue repair capacities of gingiva and dental pulp.

Cytotoxic effects to mouse and human gingival fibroblasts of a nanohybrid ormocer versus dimethacrylate-based composites.

OBJECTIVES: Tooth-colored composites have emerged as a standard restorative material in caries therapy and have largely replaced materials such as silver amalgam or glass ionomer cements. In addition to their superior esthetics and desirable mechanical properties, composites also comprise negative characteristics, such as wear, shrinkage, and an adverse biocompatibility. Modifications of classic resin-based dental composites have been developed to overcome these shortcomings. For example, ormocers are innovative inorganic-organic hybrid polymers that form a siloxane network modified by the incorporation of organic groups. Recently, a new ormocer, Admira Fusion (VOCO), was introduced to composite technology. The absence of cytotoxic matrix monomers leads to the hypothesis that ormocers have improved biocompatibility compared to resin-based dental restorative materials. MATERIALS AND METHODS: The aim of this study was to compare the cytotoxic effects of Admira Fusion to a nanohybrid composite (GrandioSO, VOCO) and a nanofiller composite (Filtek Supreme XTE, 3M Espe) on the standard dermal mouse fibroblasts (L929) and human gingival fibroblasts (GF-1) via a Cell Counting Kit-8 (CCK-8) assay. RESULTS: Admira Fusion was significantly less cytotoxic than GrandioSO and Filtek Supreme XTE to both the standard mouse dermal fibroblasts (L929) and human gingival fibroblasts. CONCLUSIONS: Compared to other resin-based dental restorative materials, the ormocer (Admira Fusion) possesses a superior biocompatibility in vitro. Future research studies are needed to confirm our results. CLINICAL SIGNIFICANCE: Clinically, dental practitioners and their patients might benefit from Admira Fusion in terms of reduced adverse biologic reactions compared to resin-based dental restorative materials.

Cytotoxic and biological effects of bulk fill composites on rat cortical neuron cells.

The aim of this study was to investigate potential cellular responses and biological effects of new generation dental composites on cortical neuron cells in two different exposure times. The study group included five different bulk-fill flow able composites; Surefil SDR Flow, X-tra Base Flow, Venus Bulk Flow, Filtek Bulk Flow and Tetric-Evo Flow. They were filled in Teflon molds (Height: 4 mm, Width: 6 mm) and irradiated for 20 s. Cortical neuron cells were inoculated into 24-well plates. After 80% of the wells were coated, the 3 µm membrane was inserted and dental filling materials were added. The experiment was continued for 24 and 72 h. Cell viability measured by MTT assay test, total antioxidant and total oxidant status were examined using real assay diagnostic kits. The patterns of cell death (apoptosis) were analyzed using annexin V-FITC staining with flow cytometry. Β-defensins were quantitatively assessed by RT-PCR. IL-6, IL-8 and IL-10 cytokines were measured from the supernatants. All composites significantly affected analyses parameters during the exposure durations. Our data provide evidence that all dental materials tested are cytotoxic in acute phase and these effects are induced cellular death after different exposure periods. Significant cytotoxicity was detected in TE, XB, SS, FBF and VBF groups at 24 and 72 h, respectively.

DNA double-strand breaks caused by new and contemporary endodontic sealers.

AIM: To investigate the cytotoxicity and genotoxicity of a new silicate-based BioRoot RCS® sealer in comparison with contemporary sealers. METHODOLOGY: A periodontal ligament cell line using lentiviral gene transfer of human telomerase reverse transcriptase (hTERT) was used and exposed to subtoxic concentrations of 24-h eluates from two epoxy resin-based (AH Plus Jet® and Acroseal® ), four various methacrylate-based endodontic sealers (EndoREZ® , RealSeal® , RealSeal SE® and Hybrid Root SEAL® ) and three silicate-based sealers (BioRoot RCS® , iRootSP® and MTA Fillapex® ). The XTT-based cell viability assay was used for cytotoxicity screening of materials. The γ-H2AX assay was used for genotoxicity screening. In the γ-H2AX immunofluorescence assay, PDL-hTERT cells were exposed to eluates of the substances for 6 h and DNA double-strand breaks (DSB) were detected microscopically. Induced foci represented DSBs, which can induce ATM-dependent phosphorylation of the histone H2AX. The statistical significance of the differences between the experimental groups was compared using the Student's t-test (P < 0.05). RESULTS: The cytotoxicity of the 24-h eluates could be ranked in the following order: Hybrid Root SEAL® >RealSeal® >Acroseal® >RealSeal SE® ≥ AH Plus Jet® > EndoREZ® >MTA Fillapex® > iRoot SP® >BioRoot RCS® . In negative controls (cells which received medium only) 4.08 ± 0.53 DSB foci (mean ± SEM) whilst in positive controls 10.76 ± 4.05 DSB foci/cell were found. BioRoot RCS® and RealSeal SE® exhibited significant differences in foci formation at 1/3 EC50 compared with their 1/10 EC50 concentration (P < 0.05). Both concentrations (1/10 and 1/3 of EC50) of AH Plus Jet® , Acroseal® , RealSeal® and MTA Fillapex® sealers were not significantly different when compared with the medium control (P < 0.05). CONCLUSIONS: New BioRoot RCS® was not toxic whilst Hybrid Root SEAL® demonstrated more toxicity and DNA double-strand breaks when compared with other resin- and silicate-based root canal sealers.

Cytotoxicity of Experimental Resin Composites on Mesenchymal Stem Cells Isolated from Two Oral Sources.

Resin composite materials that are used to restore tooth cervical lesions associated with gingival recessions can hamper healing after root coverage surgeries. This study evaluates the in vitro cytotoxic effect of five resin composites (two commercial and three experimental) on oral mesenchymal stem cells (MSCs) and the persistence of stemness properties in high passage MSCs. Sorption and solubility tests were made for all materials. MSCs were isolated from re-entry palatal and periodontal granulation tissues and were characterized and cultured on composite discs. Cytotoxicity of the materials was evaluated by the Alamar Blue viability test, by Paul Karl Horan (PKH) labeling, and by immunocytochemical staining for actin. Water and saliva sorption and solubility data revealed that two of the experimental materials behaved comparable with the marketed resin composites. The Alamar Blue viability test shows that both cell lines grew well on composite discs that seemed to induce no apparent toxic effects. No signs of disruption of cytoskeleton organization was seen. Experimental resin composites can be recommended for further investigation for obtaining approval for use. The standard minimal criteria were fulfilled for high passage MSCs. Palatal tissue regains its regenerative properties in terms of MSC presence in the re-entry area after 6 months of healing.

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.

Cytogenetic damage in exfoliated oral buccal cells by dental composites.

PURPOSE: To evaluate the possible geno/cytotoxic effects of dental composite materials by assessing the frequency of micronuclei formation and other nuclear abnormalities in the exfoliated buccal epithelium. METHODS: Swabs were taken from the buccal mucosa of 85 young healthy subjects. All participants had healthy dentition or dentition restored only with composite materials. Genotoxicity and cytotoxicity was assessed by micronucleus assay. RESULTS: The results indicated no significant difference in number of oral mucosa cells with micronuclei in subjects with different numbers of composite restored tooth surfaces (P= 0.476). Also, the number of restored surfaces had no effect on nuclear alterations closely related to cytotoxicity, such as karyolysis (P= 0.572), karyorrehexis (P= 0.573) and picnosis (P= 0.765). CLINICAL SIGNIFICANCE: Despite doubts about the safe clinical use of resin composites, this study found no evidence that composite materials trigger long-term cytogenetic damage in the epithelial cells of buccal mucosa in humans. There is no objective and quantifiable evidence of genotoxicity induced by composite restorative materials in clinical practice.

Cytogenetic genotoxic investigation in peripheral blood lymphocytes of subjects with dental composite restorative filling materials.

Dental composite resins are biomaterials commonly used to aesthetically restore the structure and function of teeth impaired by caries, erosion, or fracture. Residual monomers released from resin restorations as a result of incomplete polymerization processes interact with living oral tissues. The objective of this study was to evaluate the genotoxicity of a common dental composite material (Enamel Plus-HFO), in subjects with average 13 filled teeth with the same material, compared to a control group (subjects having neither amalgam nor composite resin fillings). Genotoxicity assessment of composite materials was carried out in vitro in human peripheral blood leukocytes using sister-chromatid exchange (SCE) and chromosomal aberrations (CA) cytogenetic tests. The results of correlation and multiple regression analyses confirmed the absence of a relationship between SCE/cell, high frequency of SCE(HFC) or CA frequencies and exposure to dental composite materials. These results indicate that composite resins used for dental restorations differ extensively in vivo in their cytotoxic and genotoxic potential and in their ability to affect chromosomal integrity, cell-cycle progression, DNA replication and repair.

In vitro study of biocompatibility of a graphene composite with gold nanoparticles and hydroxyapatite on human osteoblasts.

The purpose of this study was to evaluate the biocompatibility of some composites consisting of different proportions of graphene in combination with gold nanoparticles (AuNPs) and nanostructured hydroxyapatite (HA) on osteoblast viability, proliferation and differentiation. Au/HA@graphene composites synthesized by the catalytic chemical vapor deposition induction heating method with acetylene as the carbon source and over an Au/HA catalyst, were characterized by transmission electron microscopy, thermogravimetric analysis and Raman spectroscopy and showed that the few-layer graphene was grown over the Au/HA catalyst. The cytocompatibility study was performed using the fluorescein diacetate assay for assessment of the viability and proliferation of osteoblasts cultivated in the presence of HA, Au/HA and Au/HA@graphene composites as colloidal suspensions or as substrates. The most favorable composites for cell adhesion and proliferation were HA, Au/HA and Au/HA composites with 1.6% and 3.15% concentration of graphenes. Immunocytochemical staining performed after 19 days of osteoblasts cultivation on substrates showed that the graphene composites induced low expression of alkaline phosphatase compared to the control group and HA and Au/HA substrates. The presence of graphene in the substrate composition also induced an increased level of intracellular osteopontin and cytoskeleton reorganization (actin-F) depending on graphene concentration, suggesting cell activation, increased cellular adhesion and acquisition of a mechanosensorial osteocyte phenotype.

Cytotoxicity and genotoxicity of triethyleneglycol-dimethacrylate in macrophages involved in DNA damage and caspases activation.

Triethyleneglycol-dimethacrylate (TEGDMA) is a monomer and widely used in dental composite resins. TEGDMA has been found to exhibit cytotoxicity and genotoxicity on many cells. However, little is known about the potential toxicological implications of TEGDMA on murine macrophage cell line RAW264.7. In this study, TEGDMA demonstrated a cytotoxic effect to RAW264.7 cells in a concentration- and time-dependent manner (p < 0.05). TEGDMA was found to induce two modes of cell death in a concentration-dependent manner (p < 0.05). TEGDMA-induced cell apoptosis was demonstrated by the increase in the portion of sub-G0/G1 phase and DNA ladder formation. In addition, TEGDMA exhibited genotoxicity via a dose-related increase in the numbers of micronucleus and DNA strand breaks (p < 0.05). Furthermore, the activation of caspase-3, -8, and -9 were generated by TEGDMA in a dose-dependent manner (p < 0.05). These results indicated that cytotoxicity and genotoxicity induced by TEGDMA in macrophages may be via DNA damage and caspase activation.

Wear resistance of a modified polymethyl methacrylate artificial tooth compared to five commercially available artificial tooth materials.

STATEMENT OF PROBLEM: Wear resistance is a limitation of artificial denture teeth. Improving the wear resistance of conventional artificial denture teeth is of value to prosthodontic patients. PURPOSE: The purpose of this in vitro study was to evaluate the wear resistance and hardness of modified polymethyl methacrylate artificial denture teeth compared to 5 commercially available artificial tooth materials. MATERIAL AND METHODS: This study evaluated 180 artificial denture teeth (6 groups) that included 3 groups of conventional artificial teeth (MajorDent, Cosmo HXL, and Gnathostar), 2 groups of composite resin artificial teeth (Endura and SR Orthosit PE), and 1 group of modified surface artificial teeth. The flattened buccal surface of each tooth (n=15) was prepared for investigation with the Vickers hardness test and the elucidate wear test (n=15) by using a brushing machine. Each group was loaded for 18,000 cycles, at 2 N, and 150 rpm. The wear value was identified with a profilometer. The data were statistically analyzed by using 1-way ANOVA and post hoc Turkey honestly significant difference tests (α=.001). The tribologies were observed under a scanning electron microscope, and the cytotoxicities were evaluated by MTT assay. RESULTS: The Vickers hardnesses ranged from 28.48 to 39.36. The wear depths and worn surface area values ranged from 1.12 to 10.79 µm and from 6.74 to 161.95 µm(2). The data revealed that the modified artificial denture teeth were significantly harder and exhibited significantly higher wear resistance than did the conventional artificial teeth (P<.001). The scanning electron microscopic images revealed cross sections of the conventional artificial denture teeth with intensively worn surface areas after brushing. The cytotoxicity test revealed 97.85% cell viability, which indicates the nontoxicity of the modified surface of this material. CONCLUSIONS: Within the limitations of this study, the polymethyl methacrylate modified surface artificial denture teeth was not significantly different from that of the composite resin artificial denture teeth, with the exceptions that the surface was harder and more wear resistant.

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.