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.

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.

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.

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.

In vitro and in silico evaluations of resin-based dental restorative material toxicity.

OBJECTIVES: This study aims to evaluate the cytocompatibility of three provisional restoration materials and predict neurotoxic potential of their monomers. These materials are Tab 2000® (methyl methacrylate based), ProTemp 4™ (bis-acrylic based) and Structur 3® (urethane dimethacrylate based). MATERIALS AND METHODS: Resin samples were incubated in a cell culture medium and the cytotoxic effects of these extracts were studied in 3T3 fibroblast cells through MTT and crystal violet assays as well as ROS assessment. The presence of relevant leached monomers was determined by HPLC. Additionally, the blood-brain barrier (BBB) permeability to these resin-based monomers was predicted using ACD/Labs algorithms model. RESULTS: Cell survival rates were compared with the resin extracts, and Structur 3® was statistically significant different from the others (p < 0.001) at all-time incubation periods. All materials induced a dose-dependent loss of cell viability; however, only Structur 3 extracts were cytotoxic against 3T3 fibroblasts. The highest cytotoxic effect (77%, p < 0.001) was observed at 24 h incubation period, which may be associated with the presence of urethane dimethacrylate (UDMA) leached monomers. Furthermore, the computational model showed that most monomers under study are expectedly capable of crossing the BBB. CONCLUSIONS: Our results showed that Structur 3® is not cytocompatible with our cell model and UDMA is a potential neurotoxic compound. CLINICAL RELEVANCE: These results indicate that only ProTemp 4™ and Tab 2000® are safe for provisional restorations.

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.

A review on potential toxicity of dental material and screening their biocompatibility.

OBJECTIVES: A wide range of compounds are utilized in dentistry such as dental composites, resins, and implants. The successful clinical use of dental materials relies on theirm physiochemical properties as well as biological and toxicological reliability. Different local and systemic toxicities of dental materials have been reported. Placement of these materials in oral cavity for a long time period might yield unwanted reactions. An extensive variety of materials is used in dentistry including filling materials, restorative materials, intracanal medicines, prosthetic materials, different types of implants, liners, and irrigants. The increasing rate in development of the novel materials with applications in the dental field has led to an increased consciousness of the biological risks and tempting restrictions of these materials. The biocompatibility of a biomaterial used for the replacement or filling of biological tissue such as teeth always had a high concern within the health care disciplines for patients. MATERIALS AND METHODS: Any material used in humans should be tested before clinical application. There are many tests evaluating biocompatibility of these materials at the point of in vitro, in vivo, and clinical investigations. RESULTS: The current review discusses the potential toxicity of dental material and screening of their biocompatibility. CLINICAL RELEVANCE: It is essential to use healthy and safe materials medical approaches. In dentistry, application of different materials in long-term oral usage demands low or nontoxic agents gains importance for both patients and the staff. Furthermore, screening tests should evaluate any potential toxicity before clinical application.

Contact sensitization to ingredients of dental materials and cosmetics in dental students: a pilot study.

OBJECTIVE: The aim of this study was to evaluate the rate of contact sensitization to selected cosmetic allergens, i.e. ingredients of dental materials, in students of dental medicine and dental patients. METHODS: A total of 50 participants were included in the study: 40 students of dental medicine exposed to the studied allergens during the course of practical education; and 10 randomly selected dental patients without occupational exposure to the investigated substances served as a control group. All of them were patch-tested with colophonium, myroxylon pereirae resin, paraben mix, fragrance mix I, isopropyl myristate, triclosan, polysorbate 80, compositae mix II, and hydroperoxides of limonene. RESULTS: The sensitization rates for colophonium and polysorbate 80 were the highest. For the group of dental students, we established significantly higher sensitization rate for colophonium compared to the ones for myroxylon pereirae resin and hydroperoxides of limonene (χ2 = 4.93; p = 0.026), paraben mix (χ2 = 3.6; p = 0.05), isopropyl myristate (χ2 = 6.56; p = 0.01), and triclosan (χ2 = 8.5; p < 0.001); and to polysorbate 80 compared to the ones for myroxylon pereirae resin and hydroperoxides of limonene (χ2 = 3.97; p = 0.046), isopropyl myristate (χ2 = 5.47; p = 0.02) and triclosan (χ2 = 7.34; p = 0.007). Significantly increased concomitant sensitization rate to compositae mix and to hydroperoxides of limonene was established (χ2 = 12.55; p < 0.001). Generally, the incidence of concomitant sensitization to the studied allergens in the whole studied population was high. CONCLUSIONS: Colophonium and polysorbate 80 could be outlined as sensitizers of paramount importance for both dental students and dental patients. We consider the major importance of exposure to colophonium during the course of practical education in dentistry for the onset of the sensitization. Sensitization to compositae mix was observed only among dental students. We consider the leading role of consumer exposure for the onset of the sensitization to triclosan and to hydroperoxides of limonene. Unexpected and unreported reactions of concomitant sensitization were observed.

Porous zirconia ceramic as an alternative to dentin for in vitro dentin barriers cytotoxicity test.

OBJECTIVES: This study assessed the potential of porous zirconia ceramic as an alternative to dentin via an in vitro dentin barrier cytotoxicity test. METHODS: The permeability of dentin and porous zirconia ceramic was measured using a hydraulic-conductance system, and their permeability was divided into two groups: high and low. Using an in vitro dentin barrier test, the cytotoxicity of dental materials by dentin and porous zirconia ceramic was compared within the same permeability group. The L-929 cell viability was assessed by MTT assay. RESULTS: The mean (SD) permeability of the high and low group for dentin was 0.334 (0.0873) and 0.147 (0.0377) µl min-1 cm-2 cm H2O-1 and for zirconia porous ceramic was 0.336 (0.0609) and 0.146 (0.0340) µl min-1 cm-2 cm H2O-1. The cell viability of experimental groups which are the low permeability group was higher than that of the high permeability group for both dentin and porous zirconia ceramic as a barrier except for Maxcem Elite™ by porous zirconia ceramic. There was no significant difference between dentin and porous zirconia ceramic in cell viability, within either the high or low permeability group for all materials. The SD for cell viability of the porous zirconia ceramic was less than that of the dentin, across all materials within each permeability group, except for Maxcem Elite™ in the high permeability group. CONCLUSIONS: Porous zirconia ceramic, having similar permeability to dentin at the same thickness, can be used as an alternative to dentin for in vitro dentin barrier cytotoxicity tests. CLINICAL RELEVANCE: In vitro dentin barrier cytotoxicity tests when a standardized porous zirconia ceramic was used as a barrier could be useful for assessing the potential toxicity of new dental materials applied to dentin before applying in clinical and may resolve the issue of procuring human teeth when testing proceeds.

Polymer-based dental filling materials placed during pregnancy and risk to the foetus.

BACKGROUND: Tooth-coloured polymer-based dental filling materials are currently the first choice for dental restorative treatment in many countries. However, there are some concerns about their safety. It has been shown that substances known as endocrine disrupters, which might pass through the placental barrier, are released from these materials within the first hours after curing. Thus, the placement of polymer-based dental fillings in pregnant women may put the vulnerable foetus at risk. Large epidemiological studies exploring the risk of having polymer-based dental materials placed during pregnancy are lacking. The aim of this study was to investigate the association between the placement of polymer-based dental fillings during pregnancy and adverse birth outcomes. METHODS: This study is based on data from the large Norwegian Mother and Child Cohort Study (MoBa). The information about dental treatment during pregnancy was obtained from questionnaires sent to the participating women during weeks 17 and 30 of pregnancy. Reported placement of "white fillings" was used as exposure marker for having received polymer-based dental filling materials. Only singleton births were included in the present study. Data were linked to the Medical Birth Registry of Norway. Logistic regression models that included the mother's age, level of education, body mass index, parity, and smoking and alcohol consumption during pregnancy were used to estimate the odds ratio (OR) and 95% confidence interval (CI). Different adverse birth outcomes were of interest in the present study. RESULTS: Valid data were available from 90,886 pregnancies. Dentist consultation during pregnancy was reported by 33,727 women, 10,972 of whom had white fillings placed. The adjusted logistic regression models showed no statistically significant association between having white dental fillings placed during pregnancy and stillbirth, malformations, preterm births, and low or high birth weight. CONCLUSIONS: In this study, women who reported white fillings placed during pregnancy had no increased risk for adverse birth outcomes compared with women who did not consult a dentist during pregnancy. Thus, our findings do not support the hypothesis of an association between placement of polymer-based fillings during pregnancy and adverse birth outcomes.

[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.

General Toxicity and Antifungal Activity of a New Dental Gel with Essential Oil from Abies Sibirica L.

BACKGROUND The aim of this study was to analyze the antifungal activity and the general toxicity of a new dental gel containing essential oil from the tree Abies sibirica L., which grows in the Republic of Kazakhstan. MATERIAL AND METHODS The essential oil from Abies sibirica L. was obtained by microwave heating method using the STARTE Microwave Extraction System. Adjutants used to prepare the oil were carbomer 974P, glycerin, polysorbate 80, xylitol, triethanolamine, and purified water, all allowed for medical usage. The antifungal activity of the essential oil was assessed by monitoring the optical density of Candida albicans in a microplate reader. The safety was determined by analyzing the acute and subacute toxicity. RESULTS The essential oil obtained by the microwave heating method revealed a higher antifungal activity in comparison with the essential oil obtained by the steam distillation method. No obvious changes were detected in guinea pigs following cutaneous application of the gel. Enteral administration of the essential oil caused minimal functional and histological changes in mice after 4 weeks. The new harmless dental gel containing pine oil from Abies sibirica L. was provided for the purposes of this particular clinical research. CONCLUSIONS The high antifungal activity of the gel is the basis for more in-depth studies on its safety and pharmacological activity.

Cytotoxicity and proinflammatory cytokine expression induced by interim resin materials in primary cultured human dental pulp cells.

STATEMENT OF PROBLEM: Acrylic resin materials for interim restoration may adversely affect pulp tissue during the polymerization phase. PURPOSE: The purpose of this in vitro study was to determine the cytotoxic and proinflammatory cytokine production effects induced by interim resin materials in primary cultured human dental pulp cells (hDPCs). MATERIAL AND METHODS: Five interim resin materials were evaluated: 3 types of chemically activated products, 1 light-activated product, and 1 computer-aided design and computer-aided manufacturing (CAD-CAM) product. After obtaining eluates from interim resin materials that either were in the process of polymerizing or were already polymerized, these extracts were cocultured with hDPCs under serially diluted conditions (50%, 25%, 12.5%, 6.25%, and 3.125%) for 24 hours with positive (1% phenol) and negative (distilled water) controls. A cell viability assay with tetrazolium was used to evaluate toxic effects on the cells, and images of both live and dead cells were captured using confocal microscopy. Proinflammatory cytokine levels were measured using cytokine antibody arrays. All experiments were independently repeated 3 times, and data were analyzed using 1-way ANOVA and post hoc Tukey honest significant differences test (α=.05). RESULTS: Cell viabilities less than 70% were observed from the eluates of the 3 chemically activated products under the 50% conditions. Among the chemically activated products, the adverse effects were significantly greater with eluates derived from the polymerizing phase compared than those that had already polymerized, as shown by confocal microscopy images of live and dead cells. However, the light-activated and CAD-CAM-fabricated products did not adversely affect the hDPCs. Significantly increased levels of proinflammatory cytokines were not detected in 12.5% of extract from polymerizing compared with distilled water control. CONCLUSIONS: The 50% eluates derived from chemically activated interim resin during the polymerizing phase were cytotoxic to hDPCs and may adversely affect pulp tissue. Recommendations such as excess washing are necessary during fabrication.

Comparative Analysis of the Water Sorption and Cytotoxicity of Two different Denture Base Systems: An in vitro Study.

AIM: Different biomaterials and techniques have been introduced in the field of prosthetic dentistry with the purpose of replacement and rehabilitation of the edentulous areas. Due to their shorter setting time, the light-activated restorative and prosthetic materials have the capability of releasing few amount of cytotoxic materials in the oral cavity. Polymer materials [urethane dimethacrylate (UDMA) and bis-acryl] are assumed to have high mechanical properties. Polymethyl methacrylate (PMMA) offers numerous advantages of being highly esthetic in nature and at the same time being cost-effective. Hence, this study aimed to assess and compare the water sorption and cytotoxicity of light-activated UDMA denture base resin and conventional heat-activated PMMA resin. MATERIALS AND METHODS: This study included assessment and comparison of water sorption and cytotoxicity of heat-activated PMMA resin and light-activated UDMA denture base system. Fabrication of heat-activated PMMA resin and UDMA specimens was done by investing the wax patterns in stone molds using manufacturer's instructions. Contraction of the specimens was done for assessment of cytotoxicity and water resorption of the UDMA and PMMA resin samples. All the results were analyzed by Statistical Package for the Social Sciences software version 18.0. Chi-square test and one-way analysis of variance tests were used for the assessment of the level of significance; p < 0.05 was taken as significant. RESULTS: Mean lysis score observed in the PMMA and UDMA groups was 0.4 and 0.3 respectively. While observing at the 3 months time, the mean water resorption in the PMMA and UDMA groups was found to be 37.9 and 40.2 respectively. Significant difference in relation to water resorption was observed between the two study groups only at 3 months time. CONCLUSION: Both materials used in this study are nontoxic. Furthermore, UDMA resin materials exhibited lower water resorption after more than 1 month of time of storage. CLINICAL SIGNIFICANCE: Water resorption is similar for different denture base resin systems till 1 months time.

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.

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.

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.

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.

A review of the effects of formaldehyde release from endodontic materials.

Formaldehyde is present in most living cells and the environment. In dentistry, patients may be exposed to formaldehyde through the use of several endodontic materials (e.g. AH 26) and during formocresol pulpotomies. This review outlines how the human body reacts to formaldehyde exposure, how recent data has relooked at the issue of carcinogenicity and leukaemia associated with formaldehyde, and whether it is possible to quantify the amount of formaldehyde produced by endodontic cements. The review analyses the way formaldehyde is produced from epoxy resins and addresses the question of whether the amount of formaldehyde from endodontic cements is large enough to override the body's ability to deal with its own endogenous levels of formaldehyde and should the amount of formaldehyde produced be a concern.