Considerations about Cytotoxicity of Resin-Based Composite Dental Materials: A Systematic Review

The dental material industry is rapidly developing resin-based composites (RBCs), which find widespread use in a variety of clinical settings. As such, their biocompatibility has gained increasing interest. This literature review presents a summary of research into the cytotoxicity of methacrylate-based composites published from 2017 to 2023. Subject to analysis were 14 in vitro studies on human and murine cell lines. Cytotoxicity in the included studies was measured via MTT assay, LDH assay, and WST-1 assay. The QUIN Risk of Bias Tool was performed to validate the included studies. Included studies (based entirely on the results of in vitro studies) provide evidence of dose- and time-dependent cytotoxicity of dental resin-based composites. Oxidative stress and the depletion of cellular glutathione (GSH) were suggested as reasons for cytotoxicity. Induction of apoptosis by RBCs was indicated. While composites remain the golden standard of dental restorative materials, their potential cytotoxicity cannot be ignored due to direct long-term exposure. Further in vitro investigations and clinical trials are required to understand the molecular mechanism of cytotoxicity and produce novel materials with improved safety profiles.

Human osteoblasts response to different dental implant abutment materials: An in-vitro study

OBJECTIVES

This study aimed to investigate human osteoblasts (HOB) response towards different dental implant abutment materials.

METHODS

Five dental implant abutment materials were investigated: (1) titanium (Ti), (2) titanium coated nitride (TiN), (3) cobalt chromium (CoCr), (4) zirconia (ZrO₂), and (5) modified polyether ether ketone (m-PEEK). HOBs were cultured, expanded, and seeded according to the supplier's protocol (PromoCell, UK). Cell proliferation and cytotoxicity were evaluated at days 1, 3, 5, and 10 using Alamar Blue (alamarBlue) and lactate dehydrogenase (LDH) colorimetric assays. Data were analysed via two-way ANOVA, one-way ANOVA and Tukey's post hoc test (significance was determined as p < 0.05 for all tests).

RESULTS

All the investigated materials showed high and comparable initial proliferation activities apart from ZrO₂ (46.92%), with P% of 79.91%, 68.77%, 73.20%, and 65.46% for Ti, TiN, CoCr, and m-PEEK, respectively. At day 10, all materials exhibited comparable and lower P% than day 1 apart from TiN (70.90%) with P% of 30.22%, 40.64%, 37.27%, and 50.65% for Ti, CoCr, ZrO₂, and m-PEEK, respectively. The cytotoxic effect of the investigated materials was generally low throughout the whole experiment. At day 10, the cytotoxicity % was 7.63%, 0.21%, 13.30%, 5.32%, 8.60% for Ti, TiN, CoCr, ZrO₂, and m-PEEK. The Two-way ANOVA and Tukey's Multiple Comparison Method highlighted significant material and time effects on cell proliferation and cytotoxicity, and a significant interaction (p < 0.0001) between the tested materials. Notably, TiN and m-PEEK showed improved HOB proliferation activity and cytotoxic levels than the other investigated materials. In addition, a non-significant negative correlation between viability and cytotoxicity was found for all tested materials. Ti (p = 0.07), TiN (p = 0.28), CoCr (p = 0.15), ZrO₂ (p = 0.17), and m-PEEK (p = 0.12).

SIGNIFICANCE

All the investigated materials showed excellent biocompatibility properties with more promising results for the newly introduced TiN and m-PEEK as alternatives to the traditionally used dental implant and abutment materials.

Zebrafish; an emerging model organism for studying toxicity and biocompatibility of dental materials

Zebrafish (danio rerio) is a small, tropical freshwater teleost fish that belongs to the Cyprinidae family and lives in natural waters and rice fields in South Asia, North India, and Pakistan. Zebrafish has become a popular vertebrate model organism for biomedical research due to its numerous advantages such as their small size, short life cycle, accessibility in large numbers and inexpensive maintenance. In addition, fertilization happens externally in zebrafish and allows zebrafish to be manipulated directly. As another important advantage, the embryos are transparent thus the stages of development can be easily identified. Zebrafish can have multiple co-orthologs for human genes. In the 1930s, the zebrafish was first used as a model for developmental and embryological studies and in 1981, was introduced as a genetic model by Streisinger by force of developed genetic techniques in zebrafish such as cloning, mutagenesis and transgenesis. In the 1990s, various genetic manipulations were introduced. These improvements have contributed to the popularity of zebrafish. After that zebrafish was used in various research areas including genetics, biomedicine, neurobiology, toxicology, pharmacology as well as in human disease models. Zebrafish is also becoming a popular model organism in dental research. It is preferred in dental material toxicity studies and in research related to the genetic and molecular factors in tooth formation and craniofacial development. This review provides information on the use of zebrafish in dental research, focusing on tooth formation and dentition (pharyngeal dentition) of zebrafish and the dental research performed using zebrafish.

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.

[EVALUATION OF THE COMPARATIVE TOXICITY OF VARIOUS MATERIALS FOR DENTAL PROSTHETICS ON CELL CULTURE MODELS]

Difficulties in repairing the defects of the teeth are related with allergic-inflammatory, traumatic and dystrophic complications arising from the interaction of the foreign body with the mucous tissues of the oral cavity after the patient's prosthesis is established. The aim of our study was to establish the toxic pro-inflammatory activity of materials used for the manufacturing of bases of removable dentures - plastics based on polymethylmethacrylate prosthetic complexes Prothyl Hot, Ftorax and Perflex Flexi Nylon on the model of human leukemia transformed T cells (Jurkat cells) and MDCK cells. For the cells simulation Jurkat and MDCK cells was incubated with the components of prosthetic materials, Prothyl Hot, Ftorax and Perflex Flexi Nylon/ Prosthetic materials were added to the incubation medium at the doses used in practice (calculated at 106 cells); duration of incubation was 24 hours. A comparative assessment of the toxicity of prosthetic materials was determined by the MTT test (activity of mitochondrial dehydrogenases). Statistical analysis was carried out using the package (SPSS version 11.0). The statistical reliability of the difference between the indices was evaluated by the Student t test (the P <0.05 level was considered reliable). The results of the conducted studies testify to the absence of toxicity of the complexes Prothyl Hot, Ftorax and Perflex Flexi Nylon, used as a basis of circuit prostheses, on intact Jurkat and MDCK cells, as evidenced by the stability of their mitochondrial dehydrogenases. Based on the analysis of the conducted studies, it can be concluded, that as Jurkat and MDCK cells are used as models of immune and epithelial cells, the materials used for manufacturing of removable prostheses, the polymethylmethacrylate-based plastics (Prothyl Hot and Ftorax) and elastic thermoplastic polymer material Perflex Flexi Nylon, are not toxic. Studied materials, with the high probability, are not capable to cause massive death of immune cells, development of allergic or inflammatory damages, which in turn can stat cause the development of stomatitis and gingivitis, the destruction of the paradental tissue.

Cytotoxicity of Dental Implants: The Effects of Ultrastructural Elements

PURPOSE

In this in vitro study, the purpose was to assess the cytotoxicity profiles of seven commercial dental implant materials by using cell culture methods on an osteoblastic cell line.

MATERIALS AND METHODS

The microstructure of seven commercial dental implants (each given a letter code) was investigated via scanning electron microscopy and energy-dispersive x-ray analysis. Medium extracts were collected on the first and fifth days for each group and tested using MC3T3-E1 cell line. Cytotoxicity was evaluated with Xcelligance System and XTT reagent, and apoptosis was determined by Annexin-V staining. One-way analysis of variance (ANOVA) and Tukey's multiple range tests were used for statistical analyses. In all tests, P was set as .05.

RESULTS

ANOVA results disclosed that Ti (P = .001), Na (P = .001), Ca (P = .019), Al (P = .024), and P (P = .020) amounts were significantly different between test materials. Cytotoxicity and apoptosis analyses revealed that implant materials (C) and (E) were the materials with the lowest cell vitality and the highest apoptosis rates among the test materials. Phosphorus was the only element that presented the highest amount in C and E (14.23% and 12.29%, respectively) compared with the other implant materials tested. (F) and (G) had favorable results for all experiments.

CONCLUSION

The results suggest that pure dental implant materials with a lower number of additional elements may possess fewer cytotoxic effects than the other implant materials tested in this study.

Effect of Different Concentrations of Chlorhexidine in Glass-ionomer Cements on In Vivo Biocompatibility

PURPOSE

To examine whether a difference exists between the in vivo biocompatibility of glass-ionomer cements (GICs) containing chlorhexidine (CHX) in different concentrations.

MATERIALS AND METHODS

Eighty-four male Wistar rats were distributed into 7 groups (n = 12) and received subcutaneous implants of small tubes containing different materials, as follows: Ketac control (K), Ketac-CHX 10% (K10), Ketac-CHX 18% (K18), Resilience control (R), Resilience-CHX 10% (R10), Resilience-CHX 18% (R18), Control (polyethylene). The animals were then sacrificed on post-insertion days 7, 15 and 30, and tissues were examined under an optical microscope for inflammatory infiltrate, edema, necrosis, granulation tissue, multinucleated giant cells, and collagen fibers. The results were statistically analyzed using Kruskal-Wallis and Dunn's tests (p < 0.05).

RESULTS

Groups K18 and R18 showed larger areas of intense inflammatory infiltrate, with significant differences between group C and groups K18 and R18 (p = 0.007) at 7 days, and between groups C and K18 (p = 0.017) at 15 days. In terms of tissue repair, groups K18 and R18 demonstrated a lower quantity of collagen fibers with significant differences from group C (p = 0.019) at 7 days, and between group K18 and group C (p = 0.021) at 15 days.

CONCLUSION

The 18% concentration of CHX was shown to have a toxic effect. The 10% concentration of CHX was shown to be suitable for tissue contact. The addition of CHX to the glass-ionomer cements is a highly promising method for obtaining of an antibacterial GIC for use in clinical practice.

The analysis of cytotoxicity of an experimental preparation used for the reduction of dentin hypersensitivity

BACKGROUND

The problem of effective treatment of dentin hypersensitivity is still valid and not fully resolved.

OBJECTIVES

The aim of the study was to evaluate the potential toxicity against body tissues of an experimental preparation which is supposed to reduce dentin hypersensitivity and to compare it to a commercial formulation Seal & Protect (Dentsply) by means of measuring the activity of mitochondrial dehydrogenases (the MTT assay).

MATERIAL AND METHODS

The study used an original protective formulation which is supposed to eliminate hypersensitivity of dentin. A commercial preparation Seal & Protect (Dentsply) was used as the comparative material. Cytotoxic activity of the tested preparations (experimental and commercial) on murine lymphocyte cells CCL-1™ (NCTC clone 929) was determined in indirect contact with the use of the MTT test that measured the activity of the mitochondrial dehydrogenase enzyme.

RESULTS

A comparison of the results obtained in the MTT assay for the commercial preparation Seal & Protect (Dentsply) and the experimental formulation indicates that an experimental formulation has considerably lower cytotoxicity before polymerization, when compared to the commercial formulation, regardless of its dilution. However, after the polymerization of the commercial formulation was completed, its parameters improved significantly, especially for higher dilution values (1 : 10 and 1 : 15). Results for the experimental formulation are higher, particularly for the dilution value of 1 : 5. The overall summary of the results obtained from the MTT assay for the commercial preparation Seal & Protect (Dentsply) and the experimental formulation indicates that the experimental formulation had a significantly lower cytotoxicity before polymerization in comparison with the commercial formulation, regardless of dilution.

CONCLUSIONS

Estimating the biocompatibility of a given material is not simple, and measurement methods are rapidly evolving, as more and more is known about the interaction between dental materials and oral tissues, and also as a result of improvements in testing techniques.

TEGDMA Causes Apoptosis in Primary Human Gingival Fibroblasts

Previous in vivo studies have revealed that resins may generate a persistent inflammation of oral tissues and cell death as well. Apoptosis is an important regulated process that results in rapid cell death. This study tested the hypothesis that the comonomer triethyleneglycol-dimethacrylate (TEGDMA) causes apoptosis. The effects of TEGDMA on proliferation and apoptosis in primary oral fibroblasts were analyzed by light microscopy and flow cytometry (FACS; Annexin V-assay). TEGDMA at 5 and 7.5 mM inhibited proliferation after 24 hrs. No increased frequency of apoptosis or necrosis was observed with 1 mM or 2.5 mM TEGDMA after 24 hrs. Apoptosis and Annexin V-positive cells were observed with 5 mM and 7.5 mM TEGDMA by light microscopy after 24 hrs. A dramatic increase in apoptotic cells was detected by FACS after 24 hrs with 7.5 mM TEGDMA. Thus, TEGDMA was cytotoxic and “apoptotic” in a dose- and time-dependent manner.

The Induction of Gene Mutations and Micronuclei by Oxiranes and Siloranes in Mammalian Cells in vitro

Oxiranes and siloranes are candidate molecules for the development of composite materials with low shrinkage. Since some of these molecules are highly reactive, they could lead to adverse biological effects from underlying genetic mechanisms. Therefore, we analyzed the formation of micronuclei (chromosomal aberrations) and the induction of gene mutations (HPRT assay) in mammalian cells. The numbers of micronuclei induced by the oxirane di(cyclohexene-epoxidemethyl)ether (Eth-Ep) at low concentrations (10 μM) were about five-fold higher than controls. The related compound epoxy cyclohexyl methyl-epoxy cyclo-hexane carboxylate (Est-Ep) was less effective. The activity of diglycidylether of bisphenol A (BADGE) was even lower but similar to the most reactive silorane, di-3,4-epoxy cyclohexylmethyl-dimethyl-silane (DiMe-Sil). No induction of micronuclei was detected in the presence of a rat liver homogenate (S9). Est-Ep and Eth-Ep also induced gene mutations. Our analyses indicated low mutagenic potentials of siloranes; however, some oxiranes induced strong effects at two genetic endpoints.

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.

Capping Agent-Dependent Toxicity and Antimicrobial Activity of Silver Nanoparticles: An In Vitro Study. Concerns about Potential Application in Dental Practice

Objectives: In dentistry, silver nanoparticles (AgNPs) have drawn particular attention because of their wide antimicrobial activity spectrum. However, controversial information on AgNPs toxicity limited their use in oral infections. Therefore, the aim of the present study was to evaluate the antibacterial activities against a panel of oral pathogenic bacteria and bacterial biofilms together with potential cytotoxic effects on human gingival fibroblasts of 10 nm AgNPs: non-functionalized - uncapped (AgNPs-UC) as well as surface-functionalized with capping agent: lipoic acid (AgNPs-LA), polyethylene glycol (AgNPs-PEG) or tannic acid (AgNPs-TA) using silver nitrate (AgNO3) as control. Methods: The interaction of AgNPs with human gingival fibroblast cells (HGF-1) was evaluated using the mitochondrial metabolic potential assay (MTT). Antimicrobial activity of AgNPs was tested against anaerobic Gram-positive and Gram-negative bacteria isolated from patients with oral cavity and respiratory tract infections, and selected aerobic Staphylococci strains. Minimal inhibitory concentration (MIC) values were determined by the agar dilution method for anaerobic bacteria or broth microdilution method for reference Staphylococci strains and Streptococcus mutans. These strains were also used for antibiofilm activity of AgNPs. Results: The highest antimicrobial activities at nontoxic concentrations were observed for the uncapped AgNPs and the AgNPs capped with LA. It was found that AgNPs-LA and AgNPs-PEG demonstrated lower cytotoxicity as compared with the AgNPs-TA or AgNPs-UC in the gingival fibroblast model. All of the tested nanoparticles proved less toxic and demonstrated wider spectrum of antimicrobial activities than AgNO3 solution. Additionally, AgNPs-LA eradicated Staphylococcus epidermidis and Streptococcus mutans 1-day biofilm at concentration nontoxic to oral cells. Conclusions: Our results proved that a capping agent had significant influence on the antibacterial, antibiofilm activity and cytotoxicity of AgNPs. Clinical significance: This study highlighted potential usefulness of AgNPs against oral anaerobic Gram-positive and Gram-negative bacterial infections and aerobic Staphylococci strains provided that pharmacological activity and risk assessment are carefully performed.

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.

Relation between conversion degree and cytotoxicity of a flowable bulk-fill and three conventional flowable resin-composites

OBJECTIVE

The aim of this study is to evaluate if the cytotoxic effects of the Surefil SDR flow, bulk fill flowable composite resin and three conventional flowable materials (Venus Diamond Flow, Filtex Supreme XTE Flowable and Enamel plus HRi Flow) correlated with the conversion degree (DC); hardness and depth of cure are also assessed.

MATERIALS AND METHODS

Disks of each materials--cured using LED lamp--are utilized to evaluate DC (by FT-IR technique), amount of leached monomers (by HPLC technique), hardness (by Vickers hardness tester) and cytotoxicity (by MTT test).

RESULTS

All tested materials show light cytotoxic effects, independently from DC values. Both the latter parameter and the hardness, in fact, change in function of thickness and type of material. HPLC results show that the monomers amount leached from each specimen is influenced by thickness but it is always very low which justifies the absence of any cytotoxic effect.

CONCLUSIONS

Our findings suggest that there are not statistically significant differences in cytotoxicity in all experimental conditions, notwithstanding the differences in hardness and in degree of conversion.

Cytotoxicity of elastomeric power chains in artificial saliva: an in vitro study

INTRODUCTION

The main aim of this paper is to investigate the cytotoxicity of elastomeric power chains after stretching and immersion in a solution of artificial saliva.

MATERIALS AND METHOD

Two brands of grey polyurethane power chains available from two different firms (GAC, G&H) were selected for cytotoxicity assay. Each segment was stretched up to an initial force of approximately 200 g. Then each segment was kept stretched using appropriate equipment. The samples were tested in artificial saliva at two pH levels, pH7 and pH4. Following incubation, the saliva was removed, filtered and placed in contact with cell culture media using the RD line.

RESULTS AND DISCUSSION

At this supernatant dilution, no statistically significant difference was observed between the different groups of power chains studied in terms of cell viability. The GAC and G&H power chains, whether stretched or not and immerged in either pH7 or pH4 saliva, showed no toxic effect on RD cells (human cell line).

Cytotoxicity of resin composites containing bioactive glass fillers

OBJECTIVE

To determine the in vitro cytotoxicity of dental composites containing bioactive glass fillers.

METHODS

Dental composites (50:50 Bis-GMA/TEGDMA resin: 72.5wt% filler, 67.5%Sr-glass and 5% OX50) containing different concentrations (0, 5, 10 and 15wt%) of two sol-gel bioactive glasses, BAG65 (65mole% SiO2, 31mole% CaO, 4mole% P2O5) and BAG61 (3mole% F added) were evaluated for cytotoxicity using Alamar Blue assay. First, composite extracts were obtained from 7 day incubations of composites in cell culture medium at 37°C. Undifferentiated pulp cells (OD-21) were exposed to dilutions of the original extracts for 3, 5, and 7 days. Then freshly cured composite disks were incubated with OD-21 cells (n=5) for 2 days. Subsequently, fresh composite disks were incubated in culture medium at 37°C for 7 days, and then the extracted disks were incubated with OD-21 cells for 2 days. Finally, fresh composites disks were light cured for 3, 5, and 20s and incubated with OD-21 cells (n=5) for 1, 3, 5, and 7 days. To verify that the three different curing modes produced different levels of degree of conversion (DC), the DC of each composite was determined by FTIR. Groups (n=5) were compared with ANOVA/Tukey's (α≤0.05).

RESULTS

Extracts from all composites significantly reduced cell viability until a dilution of 1:8 or lower, where the extract became equal to the control. All freshly-cured composites showed significantly reduced cell viability at two days. However, no reduction in cell viability was observed for any composite that had been previously soaked in media before exposure to the cells. Composites with reduced DC (3s vs. 20s cure), as verified by FTIR, showed significantly reduced cell viability.

SIGNIFICANCE

The results show that the composites, independent of composition, had equivalent potency in terms of reducing the viability of the cells in culture. Soaking the composites for 7 days before exposing them to the cells suggested that the "toxic" components had been extracted and the materials were no longer cytotoxic. The results demonstrate that the cytotoxicity of composites with and without BAG must predominantly be attributed to the release of residual monomers, and not to the presence of the BAG.

Composite-induced toxicity in human gingival and pulp fibroblast cells

OBJECTIVE

The most important requirement for a material to be used in medical applications is its biocompatibility. Dental composite materials come into direct contact with oral tissues, especially gingival and pulpal cells. This study was performed to evaluate possible DNA damage in cells of human origin exposed to dental composites in vitro using a cytogenetic assay.

MATERIALS AND METHODS

Two composite resins (Vertise Flow, Kalore) were tested on human gingival and pulp fibroblasts using the acridine orange/ethidium bromide viability staining and alkaline comet assay. Cultures were treated with polymerized composites in two different concentrations (20 mg/ml, 40 mg/ml) for 14 days. Chi-square and Kruskall-Wallis non-parametric test were used for the statistical analysis (p < 0.05).

RESULTS

Significant cytotoxicity was observed for 40 mg/ml of Vertise Flow in both cultures, while Kalore (40 mg/ml) showed cytotoxic effect only on human pulp fibroblasts. A significant level of DNA damage was detected for both materials and concentrations, in both cell cultures.

CONCLUSION

If the two cell cultures are compared, the pulp cells were more sensitive to the cyto/genotoxic effects of dental composites. Based on the results, one can conclude that the use of tested materials may cause cellular damage in gingival and pulp fibroblasts in vitro.

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.

[Cytotoxicity of two dental materials on fibroblasts derived from human embryonic stem cells]

OBJECTIVE

To investigate the cytotoxicity of calcium hydroxide (CH) and composite resin on fibroblasts derived from human embryo body fibroblasts-H9 (EBf-H9), human dental pulp cells (hDPCs) and immortalized fibroblasts L929; and to evaluate the use of EBf-H9 as a cellular model for cytotoxicity screening of dental materials.

METHODS

The EBf-H9 cells were derived from human embryonic stem cells (H9) via outgrowth of embryonic body (EB); hDPCs were isolated from healthy dental pulp, and identified by immunochemical staining. Cell Counting Kit-8 (CCK-8) assay was applied to analyze the cytotoxicity of CH and composite resin with serial concentrations on the 3 kinds of cells.

RESULTS

Following 24 h and 48 h (or 72 h) post-treatment of CH and composite resin, the viability of L929 cells was significantly lower than that of EBf-H9 and hDPCs (P<0.05), and there was no significant difference between the last two groups (P>0.05).

CONCLUSION

Immortalized fibroblasts L929 cells exhibited different response to CH and composite resin compared with EBf-H9 and hDPCs, and the last two cell types were similar to each other. This study indicated that fibroblasts derived from human embryonic stem cells were a potential cellular model instead of traditional immortalized murine cell line for cytotoxicity screening assay.

[Surface aspect of fixed restaurations and parodontal influences]

Any new class of materials requires a new cutting technology which, unless complied with properly, may negatively impact on the advantages and performance of the material. The modifications appeared as a result of the technological processes in the structure or surface aspect of the materials not only affects the mechanical resistance of the restorations but also casts doubts on their biological qualities.

AIM

This study evaluates the impact of biomaterials involved in fixed restorations on the periodontal architecture, bearing extremely important connotations in the long run.

MATERIAL AND METHODS

The "in vitro" testing was conducted on culture cells for the cytotoxic effect of certain restorative materials--metallic alloys used in prosthetic restorations, composite materials, in collaboration with the Virology Laboratory of the Public Health Institute.The tested materials were metallic alloys, composite materials and acrylic resins used for the construction of standard sized plates (out of each material) in order to avoid the differences that might arise from the technological process. Artificial saliva processed to reach a pH = 7 was prepared in the Biophysics Laboratory of UMF Iasi. Material samples and the saliva inoculated with these were tested. -p.

RESULTS AND DISCUSSIONS

The cytotoxic effect of the tested materials on the celular cultures takes on extremely diverse forms, from discrete morphological modifications of the cells with regard to the size, shape, internal structure (for the noble and semi-noble alloys) up to the partial stripping-off of the celular film, the modification of density and coloration. In the case of the witness of non-inoculated culture, the testing results showed the presence of a continuous film, with cells having the same size, transparency and colouring, with an unaltered polyhedral contour, with visible nuclei, an image also kept in the case of the saliva witness.

CONCLUSIONS

The involvement of restaurative materials in triggering, maintaining and aggravating a periodontal pathology indicates the capital role played by the dentist in the identications of lesions during measures by avoiding or excluding etiological agents before an obvious lesions occurs in the process of active dispensarization.

Anti-adhesive and pro-apoptotic effects of 2-hydroxyethyl methacrylate on human gingival fibroblasts co-cultured with Streptococcus mitis strains

AIM

To evaluate and observe the cellular reactions that occur during the interaction/integration between 2-hydroxyethyl methacrylate/host tissue/microbial environment, in a co-culture of human gingival fibroblasts (HGF) and Streptococcus mitis strains.

METHODOLOGY

Streptococcus mitis were cultured with strains in the presence of 3 mmol L(-1) HEMA for 48 h and 72 h. Cytotoxicity was evaluated by the trypan blue dye exclusion test. Apoptosis was evaluated by TUNEL analysis. Adhesion was evaluated by immunofluorescence and western blot analyses. Quantitative analyses of the results were acquired by Qwin Plus 3.5 and QuantityOne I-D analysis software, respectively. The statistical significance of the results was evaluated using t-tests and linear regression tests.

RESULTS

The trypan blue dye test revealed 47.3% and 46.5% of dead fibroblasts after 48 and 72 h HEMA treatment, respectively, while bacterial viability was not influenced by the presence of HEMA and fibroblasts. The expression of pro-collagen I, involved in fibroblast adhesion, in untreated samples ranged from 12.49% to 6.91% of the positive area after 48 and 72 h, respectively, dropping to below 2% of the positive area in the other experimental conditions. Unlike the trypan blue test, co-cultured samples treated with HEMA showed 20% and 25% versus 17% and 21% (after 48 and 72 h, respectively) of apoptotic cells.

CONCLUSIONS

The evidence for HEMA toxicity and anti-adhesive effects against eukaryotic cells was reduced in the presence of bacteria, suggesting that dental resins should be well polymerized to avoid the spread of toxic monomers within the mouth.

Embryotoxicity assays for leached components from dental restorative materials

BACKGROUND

Currently, there are no suitable assays available to evaluate the embryotoxicity of leached components from restorative dental materials.

METHODS

The effect of the medium conditioned by composites and amalgam on mouse blastocysts in vitro was tested. The materials were also subcutaneously implanted, and the effect of the medium supplemented with serum from the host blood was evaluated in the embryotoxicity assay. The embryo implantation rate in the material-transplanted mothers was also evaluated.

RESULTS

The results show that while the culture in media conditioned by amalgams did not affect blastocyst development, the medium conditioned by composites caused blastocyst degeneration and apoptosis. The development of blastocysts in a medium containing serum obtained from animals after transplantation was, however, without effect. Finally, inconsistent reduction in the implantation rate in transplanted mothers was observed.

CONCLUSIONS

In this study, we provide examples of in vitro and in vivo tests that may be used to evaluate embryotoxicity for dental materials. Our results show that leached components from our composite-material induced embryotoxicity in vitro, however, no toxicity was observed when subcutaneously implanted in vivo. This highlights the necessity of integrated in vitro and in vivo tests for valuable predictive estimation of embryotoxicity for complex materials.

Current status of potential bisphenol toxicity in dentistry

Bisphenols are chemical components found in dental composites and sealants. Similar compounds also can be found in baby bottles, food can liners, and even drinking water. Bisphenols have gained attention recently because they, like other natural and synthetic compounds, including hormone-based drugs and soybean products, have the capacity to mimic the actions of the hormone estrogen in living cells and animals. Such estrogenic activity has been linked to a variety of health problems, including breast and prostate cancer, metabolic disorders, and reproductive dysfunction. In early 2010, the FDA issued a report stating that there are some concerns about the safety of bisphenols in food products and called for more research on bisphenol toxicity. At present, no regulatory or professional organization has expressed concern about health effects of bisphenols in dental materials.

2-hydroxylethyl methacrylate (HEMA), a tooth restoration component, exerts its genotoxic effects in human gingival fibroblasts trough methacrylic acid, an immediate product of its degradation

HEMA (2-hydroxyethyl methacrylate), a methacrylate commonly used in dentistry, was reported to induce genotoxic effects, but their mechanism is not fully understood. HEMA may be degraded by the oral cavity esterases or through mechanical stress following the chewing process. Methacrylic acid (MAA) is the primary product of HEMA degradation. In the present work we compared cytotoxic and genotoxic effects induced by HEMA and MAA in human gingival fibroblasts (HGFs). A 6-h exposure to HEMA or MAA induced a weak decrease in the viability of HGFs. Neither HEMA nor MAA induced strand breaks in the isolated plasmid DNA, but both compounds evoked DNA damage in HGFs, as evaluated by the alkaline comet assay. Oxidative modifications to the DNA bases were monitored by the DNA repair enzymes Endo III and Fpg. DNA damage induced by HEMA and MAA was not persistent and was removed during a 120 min repair incubation. Results from the neutral comet assay indicated that both compounds induced DNA double strand breaks (DSBs) and they were confirmed by the γ-H2AX assay. Both compounds induced apoptosis and perturbed the cell cycle. Therefore, methacrylic acid, a product of HEMA degradation, may be involved in its cytotoxic and genotoxic action.

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.

In vitro evaluation of cytotoxicity of permanent prosthetic materials

OBJECTIVES

To assess qualitative and quantitative cytotoxicity effect on permanent prosthetic materials to human gingival fibroblasts.

METHODS

Human gingival tissues were collected (with informed consent) from patients undergoing periodontal surgical procedures and fibroblasts were cultured in vitro. Cell type was determined by performing proteomic analysis. Selected prosthetic materials including titanium, feldspathic ceramic, gold and chrome-cobalt alloy specimens (5×2 mm) were fabricated. The toxicity of prepared specimens was tested by exposing them to cell culture medium for 48, 72, 96 and 120 hours at 37°C under sterile conditions. Cell viability was estimated using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. The data concerning cell viability were statistically analyzed using two-way ANOVA test and Tukey multiple comparison test.

RESULTS

Results obtained after 48 hours showed no toxic effect of titanium compared to control group. Cytotoxic effect was observed in gold alloy and feldspathic ceramic, however, it was not significant compared to control group. Chrome-cobalt alloy significantly reduced cell viability compared to control group (p≤0.001). Cytotoxicity diminished with increasing incubation time of specimens. After 120 hours of incubation all tested materials, except chrome-cobalt alloy, had no cytotoxicity.

CONCLUSIONS

Titanium proved to be non-toxic. Gold alloy and feldspathic ceramic had short-term cytotoxic effect. Chrome-cobalt alloy had highest cytotoxic effect on fibroblast cells.

In-vitro study of cellular viability and nitric oxide production by J774 macrophages stimulated by interferon gamma with ceramic, polycarbonate, and polyoxymethylene brackets

INTRODUCTION

Ceramic brackets are chemically inert in the oral cavity, whereas polycarbonate and polyoxymethylene brackets can degrade and release bisphenol-A and formaldehyde, respectively. More reliable tests are needed to assess the potential toxicity of these materials. In addition to traditional cytotoxicity tests, the study of nitric oxide (NO) cellular production stimulated by a specific material has been shown to be a reliable tool for evaluating cytotoxic potential. The purpose of this study was to assess, with esthetic brackets, cellular viability by 3,(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay (Sigma, St. Louis, Mo) in the macrophage cell line J774 stimulated with interferon gamma. Interferon gamma is a key cytokine in the activation of macrophages, plays an important role in immunologic processes, and also quantifies NO production by these macrophages.

METHODS

Well plates were seeded with 2 x 104 J774 cells per well, in a volume of 100 microL, resuspended in Roswell Park Memorial Institute Supplemented Medium 1640. The macrophage cell line J774 was stimulated with interferon gamma. Ceramic, polycarbonate, and polyoxymethylene brackets were added and kept in the culture for 24, 48, or 72 hours in 5% carbon dioxide at 37 degrees C; the control samples did not include brackets. At the end of each incubation period, the supernatant was collected for posterior NO quantification, and the cells were evaluated for cytotoxicity.

RESULTS

Cellular viability in all groups was higher at 72 hours than at 24 hours. The final means in the bracket groups did not show significant differences compared with the control group. NO production was significantly greater in all groups at the final time than at the initial time. However, the brackets with the interferon gamma stimulation did not result in greater NO production than did the cells in the control group.

Cytotoxicity of orthodontic separating elastics

BACKGROUND

Separating elastics may be cytotoxic to the interdental gingival tissues. Both latex and non-latex separating elastics are widely used and both types should be biocompatible.

OBJECTIVE

To determine if latex and non-latex orthodontic separating elastics are cytotoxic.

METHODS

The cytotoxicity of natural latex (Groups A, D and O) and non-latex (Group M) orthodontic separating elastics were determined by incubating 15 elastics of each type in Eagle's essential medium (MEM), removing the supernatant after 24, 48, 72 and 168 hours and adding it to cultures of L-929 mouse fibroblasts in growth medium (MEM plus glutamine, garamicine, fungizone, sodium bicarbonate, buffered saline and foetal calf serum). To verify the cell response in extreme situations, three additional groups were included: Group CC (cell control), consisting of L-929 cells not exposed to supernatants from the maintenance medium with the elastics; Group C+ (positive control), consisting of Tween 80; Group C- (negative control), consisting of phosphate buffered saline solution. The positive and negative controls were incubated in MEM maintenance medium for 24, 48, 72 and 168 hours and the extracted elutes were added to L-929 line cells incubated in the growth medium. The viability of the cells was determined with neutral red (dye-uptake method) at 24, 48, 72 and 168 hours. The data were analysed with the analysis of variance (ANOVA) and Tukey's multiple comparison test. The significance level was p < or = 0.05.

RESULTS

The elastics in Groups A, D and O induced greater cell lysis at 72 hours compared to the other experimental times. There were statistically significant differences between the cytotoxicity of the elastics in Groups A, D and O in relation to Group CC for experimental times of 24, 48, 72 and 168 hours (p > 0.05). There was not, however, a statistically significant difference between Groups D and CC at 24 hours.

CONCLUSION

The latex and non-latex orthodontic separating elastics tested were considered to be biocompatible.

Dental application potential of mesenchymal stromal cells and embryonic stem cells

In the past decade, research on the potential applications of stem cells in dentistry has made great progress. There are at least five different types of multipotent mesenchymal stromal cells (MSCs) originating from exfoliated primary teeth, including dental pulp, apica papilla, periodontal ligament, and dental follicle. It has been reported that dental tissue-derived MSCs are able to generate dentine-pulp-like complexes as well as differentiate into periodontal and craniofacial progenitor cells. Similar to these dental tissue-derived MSCs, bone marrowderived MSCs are also capable of developing into ameloblasts, odontoblasts and periodontal ligament progenitor cells, as well as regenerating cementum, alveolar bone, craniofacial bone and articular condyles. Besides adult stem cells, embryonic stem cells are an alternative cell source for dental tissue regeneration, but the current data are preliminary and are based predominantly on in vitro data. In addition to these commonly reported stem cells, other progenitor cells with MSC properties are also found in salivary glands, tongue muscle, taste buds and oral mucosa, and these may play a role in recovering the function of the residing tissues. Other than these regenerative applications, many reports have demonstrated the utility of these stem cells in cytotoxicity testing, biocompatibility testing and developmental research. The present article summarises the above findings regarding the regenerative and other potential applications of both MSCs and embryonic stem cells.

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.

[Progress in the studies of methods for testing cytotoxicity of dental biomaterial]

The favorable biocompatibility of dental biomaterial is very important, which guarantees the safety and effectiveness of its clinical application. The cytotoxicity test, as one of the biological evaluation screening tests, is known to be an important and frequently used method to evaluate biocompatibility of biomaterials. This text is devoted to an overview of the cytotoxicity test for dental materials.

Parental attitudes on restorative materials as factors influencing current use in pediatric dentistry

PURPOSE

The purpose of this study was to determine pediatric dentists' current practices and the perceptions about parents' opinions and how those parental preferences regarding dental materials influence dentists' practices.

METHODS

A questionnaire was sent to 500 randomly selected active members of the American Academy of Pediatric Dentistry. Twenty-five items queried demographics, use of restorative materials, perceptions of parents' attitudes towards materials, and dentists' reactions to parents' concerns.

RESULTS

The survey response rate was 61%. Parental concerns about materials in decreasing order were: (1) esthetics; (2) cost; (3) toxicity; and (4) durability. Parents' greatest concerns about stainless steel crowns were: (1) esthetics; and (2) cost. Among respondents, 43% followed parental preferences when challenged, and 28% currently never use amalgam. Amalgam use and the dentists' perception of parental challenge were each related to the socioeconomic status of the practice population, with lower socioeconomic practices feeling less parental challenge than higher socioeconomic practices and being more likely to use amalgam than "white" filling materials (P = .001).

CONCLUSIONS

Mercury concerns occur more frequently with higher than lower socioeconomic status parents (P = .002). Stainless steel crowns are challenged based on esthetics and cost. When confronted, many pediatric dentists (43%) follow parental preferences, even when that action is contrary to their initial clinical judgment.

Evaluation of tissue reaction to some denture-base materials: an animal study

AIM

Controversy continues regarding the biocompatibility of denture base materials. One method to evaluate the biocompatibility of materials is in an animal study. Using dogs as subjects, the purpose of this study was to evaluate the vestibular tissue reaction to cobalt chromium (Co-Cr), heat cure acrylic resin, and acrylic resin mixed with aluminum oxide (Al2O3) compared with a control group using the histopathologic method.

METHODS AND MATERIALS

Twelve disk shape samples (2 mm x 8 mm) in four groups of Co-Cr, acrylic resin, acrylic resin mixed with a 20% weight ratio of Al2O3, and a control group (Teflon) were fabricated. In one stage surgery two samples of each material (8 samples) was implanted in the buccal vestibule of each dog (n=6), subcutaneously. At 45 and 90-day intervals, half of the samples were excised along with peripheral tissue to assess the presence of inflammation by grading on a scale from 0 to 3 and the presence of a fibrotic capsule using histological observations. Data were analyzed using the Kruskal-Wallis, Mann-Whitney, and Tau b Kendal tests.

RESULTS

Tissue reaction between Co-Cr and the control group was significant (P=0.02), but it was not significant between other groups. There was no significant difference between the 45 and 90-day post-insertion samples. The formation of fibrotic capsule groups was significant (P=0.01). It was significant between the Co-Cr and acrylic resin groups (P=0.01) and the acrylic resin and control groups (P=0.01).

CONCLUSION

The Co-Cr group was more toxic than the other groups. The inflammation increased during time. The inflammation in two acrylic groups was greater than the control and less than the Co-Cr group. The formation of fibrotic capsule, except in the acrylic resin with Al2O3 group, increased over time.

CLINICAL SIGNIFICANCE

Co-Cr alloys are toxic and can produce damage to living tissue. Heat cure acrylic resin materials have less toxicity, and their use is safer than Co-Cr alloys.

Hybrid cell death induced by exposure to 2-hydroxyethyl methacrylate (HEMA): an ultrastructural and X-ray microanalytical study

PURPOSE

The aim of this study was to evaluate the ultrastructural characteristics and ionic profile of U937 cells after exposure to 2-hydroxyethyl methacrylate (HEMA) to shed light on the cytotoxicity of this dental adhesive and its relation to mechanisms of cell death.

MATERIALS AND METHODS

U937 human monoblastic cells were incubated in RPMI 1640 culture medium and exposed to HEMA at LD50. Structural changes after 5, 15, 30, 60, and 120 min were observed with transmission electron microscopy. Ionic content of Na, K, Cl, Mg, P and S was evaluated by quantitative electron probe X-ray microanalysis.

RESULTS

Our results in human monoblastic cell line U937 establish that exposure to HEMA at LD50 led to a singular mechanism of cell death characterized by changes in the morphology and ultrastructure of the cells (cell size, blebs, and organelle structure) compatible with apoptosis, but without changes in nuclear ultrastructure. These findings were consistent with our microanalytical data, which revealed a significant increase in intracellular Na and a decrease in K, along with a significant initial decrease in Cl concentration followed later (120 min) by an increase.

CONCLUSION

All three lines of evidence (cell morphology, ultrastructural changes, and ionic profile) showed that HEMA at LD50 led to a hybrid process of cell death. We suggest that apoptosis and necrosis are part of a continuum comprising a single process of cell death.

[Biocompatibility study of some adhesive systems for tooth pulp indirect and direct capping]

Microcolorimetric method was used for study of toxic and antiproliferous properties of 3 adhesive systems acting by adhesive upon fibroblast cell culture. It was established that I Bond adhesive system was most biocompatible and that it can be used for direct and indirect capping of injured tooth pulp.

Release phenomena and toxicity in polymer-based dental restorative materials

In this work, the origin of the release phenomena occuring in resin-based dental restorative materials is demonstrated using confocal fluorescence microscopy and tapping mode atomic force microscopy techniques. The surface structure (microcavities, protruded filler particles, grain boundaries, and cracks) produced by water environment on the surface of composite resins and resin-modified glass-ionomeric cements (RMGICs) are shown. The water absorption and the subsequent weight decrease, induced by leaching process, have been measured by gravimetric analysis. The different toxicity effects induced by the component release are described.

Toxicity potentiation by H2O2 with components of dental restorative materials on human oral cells

Toxicity potentiation of two monomers [bisphenol-A-glycidyldimethacrylate (BisGMA) and urethanedimethacrylate (UDMA)] as well as two comonomers [triethyleneglycoldimethacrylate (TEGDMA) and 2-hydroxyethylmethacrylate (HEMA)], each in combination with H(2)O(2), was investigated on the viability on human gingival fibroblasts (HGF) and human pulpal fibroblasts (HPF). The applied concentration of H(2)O(2) was 0.06 or 0.1 mmol/l, respectively, corresponding to the EC(0) of H(2)O(2) in HGF or HPF. The cell viability was assessed by the XTT test. From this test the half maximum effect concentrations (EC(50)) were calculated from fitted sigmoidale curves. EC(50) values were (HGF; mmol/l; mean +/- s.e.m.; n = 5): HEMA 11.9 +/- 0.9, TEGDMA 3.7 +/- 0.3, H(2)O(2) 0.36 +/- 0.04, UDMA 0.27 +/- 0.08, and BisGMA 0.11 +/- 0.03. No significant (P < 0.05) differences in the EC(50) values were observed when HGF was exposed to substances, as compared to HPF. No significant decrease of the EC(50) values was found when HGF or HPF, respectively, was exposed to HEMA or BisGMA in addition with H(2)O(2) up to the concentration of 0.1 mmol/l, as compared to those EC(50) values of each compound without H(2)O(2) addition. A significant decrease of the TEGDMA EC(50) value from 3.7 to 2.1 or 0.4 mmol/l, respectively, was found when cells were exposed to TEGDMA in combination with H(2)O(2) (0.06 or 0.1 mmol/l), as compared to that TEGDMA EC(50) value without H(2)O(2) addition. A significant decrease of the UDMA EC(50) value from 0.27 to 0.11 or 0.08 mmol/l, respectively, was found when HGF or HPF was exposed to UDMA in combination with H(2)O(2) (0.06 or 0.1 mmol/l), as compared to that UDMA EC(50) value without H(2)O(2) addition. The addition of H(2)O(2) (0.06 or 0.1 mmol/l) resulted in a toxicity potentiation of TEGDMA and UDMA, but not of HEMA and BisGMA, on HGF or HPF.

Expression of Bone Extracellular Matrix Proteins on Osteoblast Cells in the Presence of Mineral Trioxide

The biocompatibility of periapical tissue with mineral trioxide aggregate (MTA) affects its ability to repair and regenerate itself. Here we report the cytotoxicity of MTA and how it affects the expression of bone extracellular matrix protein in MC3T3-E1 osteoblast cells. We quantified the cytotoxicity of MTA, amalgam, and Dycal (Dentsply/Caulk, Milford, DE) on MC3T3-E1 cells by measuring the ability of cells to cleave a tetrazolium salt to produce formazan dye during a period of 24, 48, or 96 hours. We used reverse-transcriptase polymerase chain reaction with primer sets for type I collagen, osteocalcin, and bone sialoprotein to measure the gene-expression response of MC3T3-E1 cells treated with MTA. MTA, amalgam, and Dycal were less toxic after 48 hours. MC3T3-E1 cell growth with MTA and Dycal was greater than nonstimulated controls. MTA caused an upregulation of type I collagen and osteocalcin messenger RNA expression after 24 hours. These results showed that, in the presence of MTA, cells grow faster and produce more mineralized matrix gene expression in osteoblasts.

Biocompatibility of denture base acrylic resins evaluated in culture of L929 cells. Effect of polymerisation cycle and post-polymerisation treatments

OBJECTIVE

The purpose of this study was to evaluate the effect of two post-polymerisation treatments and different cycles of polymerisation on the cytotoxicity of two denture base resins.

MATERIALS AND METHODS

The resins tested were Lucitone 550 and QC 20. Discs of resins were fabricated following the manufacturer's instructions. Lucitone 550 was processed by long cycle or short cycle. The resin QC 20 was processed by reverse cycle or normal cycle. The specimens were divided into groups: (i) post-polymerised in microwave for 3 min at 500 W; (ii) post-polymerised in water-bath at 55 degrees C for 60 min and (iii) without post-polymerisation. Eluates were prepared by placing three discs into a sterile glass vial with 9 ml of Eagle's medium and incubated at 37 degrees C for 24 hours. L929 cells were seeded into 96 well culture plates and DNA synthesis was assessed by (3)H-thymidine incorporation assay.

RESULTS

The results were submitted to two-way anova and Tukey HSD test. QC 20 specimens polymerised by the normal cycle and submitted to microwave post-polymerisation were graded as moderately cytotoxic. Similar results were observed for Lucitone 550 processed by long cycle without post-polymerisation. The other experimental groups were graded as not cytotoxic. After water-bath post-polymerisation, specimens of Lucitone 550 processed by long cycle produced significantly lower inhibition of DNA synthesis than the other groups.

CONCLUSION

The long cycle increased the cytotoxicity of Lucitone 550 and water-bath post-polymerisation reduced the cytotoxicity of Lucitone 550 processed by long cycle.

Cytotoxicity of resin monomers on human gingival fibroblasts and HaCaT keratinocytes

OBJECTIVES

The aim of this study was to evaluate and compare the biological effects of three resin monomers on three human gingival fibroblast (HGF) cell lines and immortalised human keratinocytes.

METHODS

Primary HGFs and HaCaT keratinocytes were cultured for 24h and grown to sub-confluent monolayers. Resin monomers were dissolved in dimethyl sulphoxide (DMSO) and diluted with culture medium. Cultures were exposed to different concentrations of monomers (10(-2) to 10mM) for 24h. Cell viability measured by Alamar Blue assay, and cell culture supernatant was examined for the presence of human interlukin-1beta (IL-1beta) using sandwich enzyme-linked immunosorbant assay (ELISA). TC50 values were calculated from fitted dose-response curves.

RESULTS

All monomers showed toxic effects on the HGFs and HaCaT cells and inhibited chemical reduction of Alamar Blue in high concentrations. Statistical analysis of TC50 values by one-way ANOVA followed by Tukey's analysis showed that there is a significant difference in TC50 values between the cell lines (p<0.05), although the rank order of monomer toxicity remained the same for different cell lines. None of these monomers-induced IL-1beta release from HGFs and HaCaT cells.

SIGNIFICANCE

Dental resin monomers are toxic to human gingival fibroblasts and HaCaT keratinocytes. However, they cannot induce IL-1beta release from these cells by themselves. Alamar Blue assay is a sensitive method for the evaluation of cytotoxicity and it can detect different sensitivities of different cell lines to the resin monomers.

Biocompatibility of glass?ionomer cements using mouse lymphoma cells in vitro

Glass-ionomer cements are widely used in dentistry as restorative materials and adhesives for composite restorations. A number of genotoxicity studies have been conducted using these materials with results conflicting so far. Thus, the approach was aimed to look at the genotoxic and cytotoxic potential of three different glass-ionomer cements available commercially (Ketac Cem, Ketac Molar and Vitrebond) by the single cell gel (comet) assay and trypan blue exclusion test, respectively. For this, such materials were exposed to mouse lymphoma cells in vitro for 1 h at 37 degrees C. Data were assessed by Kruskall-Wallis non-parametric test. The results showed that all powders assayed did not show genotoxic effects. On the other hand, the liquid from Vitrebond at 0.1% dilution caused an increase of DNA injury. Significant statistically differences (P < 0.05) in cytotoxicity provoked by all powders tested were observed for exposure at 1,000 micro g mL(-1) concentration and 100 micro g mL(-1) for Ketac Molar. With respect to liquids of glass-ionomer cements evaluated, the major toxic effect on cell viability was produced at 1%, beginning at the dilution of 0.5% for Vitrebond. Taken together, these results support the notion that some components of glass-ionomer cements show both genotoxic and cytotoxic effects in higher concentrations.

(Meth)acrylate monomer-induced cytotoxicity and intracellular Ca2+ mobilization in human salivary gland carcinoma cells and human gingival fibroblast cells related to monomer hydrophobicity

To elucidate a possible link between the cytotoxicity and Ca(2+) mobilization by (meth)acrylates, we investigated the cell survival of and change in [Ca(2+)](i) in human salivary gland (HSG) cells (salivary gland carcinoma cell line) and human gingival fibroblasts (HGF) cells treated separately with 9 (meth)acrylate monomers used in dentistry. The cell survival was determined by the MTT method, and the [Ca(2+)](i) changes after the stimulation with the (meth)acrylate monomers were measured in floating indo-1/AM-loaded cells in Ca(2+)-free medium. For both HSG and HGF cells, the cytotoxicity of the monomers was approximately proportional to their hydrophobicity (logP). No increase in [Ca(2+)](i) was found with hydrophilic monomers, even with 10mm stimulation. [Ca(2+)](i) elevation by hydrophobic monomers occurred in a dose- and hydrophobic-dependent manner. The [Ca(2+)](i) change in HSG cells appeared as twin peaks, i.e., an initial sharp peak followed by a delayed broad one; whereas with the HGF cells only a single broad peak was seen, possibly dependent on their membrane quality. Pretreatment with n-butanol or methylmethacrylate enhanced the butylmethacrylate-induced [Ca(2+)](i) elevation, suggesting the [Ca(2+)](i) elevation by (meth)acrylate may be related to monomer hydrophobicity and cell type. The causal link between the cytotoxicity and [Ca(2+)](i) mobilization of monomers is discussed.

In vitro cytotoxicity of a low-shrinkage polymerizable liquid crystal resin monomer

The objective of this study was to determine the in vitro cytotoxicity of novel, polymerizable liquid crystal resin monomers when placed in direct contact with dental and nondental cell lines. One common dimethacrylate and three liquid crystal compounds, Bis-glycidyl methacrylate (Bis-GMA), 2-(t-butyl)-1,4-bis-{4-(6-acryloxy-hexane-1-oxy)-benzoyloxy}-benzene (C6), 2-(t-butyl), 1-[6-(3-acryloxy-propionoxy)-hexane-1-oxy-benzoyloxy], 4-[4-(6-acryloxy-hexane-1-oxy)-benzoyloxy]-benxene (by-product), and a 3:2 mixture of C6 and by-product, respectively, were tested for relative cytotoxicity in vitro. Cultured dental and nondental cells were treated for 24 h with test compound dissolved in media over a fourfold range of concentration (10(-4) -10(-7) mol/L). Cytotoxicity was measured using the WST-1 reagent as an indicator of remaining cell numbers based on the reduction of WST-1 substrate by mitochondrial dehydrogenases in viable cells. Bis-GMA ID(50) was found to be consistent with ID(50) values reported in the literature. A small but significant difference in the sensitivity of the dental and nondental cells in regard to their response to this dimethacrylate was noted. The liquid crystal resin monomers were significantly less cytotoxic to all cell lines tested. ID(50) values of >1 x 10(-4) mol/L were registered for the C6 and by-product monomers alone. The 3:2 mixture of C6 and by-product had a slightly higher cytotoxicity (ID(50) = 1 x 10(-4) mol/L); however, this remained significantly less than that of Bis-GMA. The results demonstrate that the newly synthesized low-shrinkage, polymerizable liquid crystal resin monomers demonstrate a minimal cytotoxic effect on both dental and nondental cells. These data suggest that the low-shrinkage liquid crystal resin monomers will not elicit a response by oral tissues (pulp tissue) when used to repair carious lesions in posterior teeth.

The effect of two fibre impregnation methods on the cytotoxicity of a glass and carbon fibre-reinforced acrylic resin denture base material on oral epithelial cells and fibroblasts

Acrylic resin dentures may have cytotoxic effects on oral soft tissues. However, there is sparse data about the cytotoxic effect of fibre-reinforced acrylic resin denture base materials. The purpose of this in vitro study was to determine the effect of two fibre impregnation methods on the cytotoxicity of a glass and carbon fibre-reinforced heat-polymerized acrylic resin denture base material on oral epithelial cells and fibroblasts. One hundred acrylic resin discs were assigned to five experimental groups (n = 20). One of the groups did not include any fibre. Two groups consisted of silane and monomer treated glass fibres (Vetrolex) impregnated into acrylic resin (QC-20) discs. The other two groups consisted of silane and monomer treated carbon fibres (Type Tenox J, HTA). Untreated cell culture was used as positive control. The human oral epithelial cell line and buccal fibroblast cultures were exposed to test specimens. The cytotoxicity of the test materials was determined by succinic dehydrogenase activity (MTT method) after 24 and 72 h exposures. Data were analysed with a statistical software program (SPSSFW, 9.0). A one-way analysis of variance (anova) test and Bonferroni test were used for the comparisons between the groups. All statistical tests were performed at the 0.95 confidence level (P < 0.05). After 24 and 72 h incubation, cell viability percentages of all experimental groups showed significant decrease according to the positive control cell culture. Fibroblastic cell viability percentages of silane and monomer treated fibre-reinforced groups were lower than the unreinforced group. Cell viability of monomer-treated groups displayed the lowest percentages. Elapsed incubation time decreased epithelial cell viability in silane-treated groups. Fibroblastic cell viability was not influenced by elapsed time except the unreinforced group.