Investigation of the cytotoxic effect of current dentine bonding agents on human dental pulp cells.

BACKGROUND: An ideal aesthetic restorative material should be attached to the tooth tissues by adhesion, have a smooth surface as possible, should not cause toxic reactions in the pulp and discoloration and microleakage. This study aims at comparatively assess the cytotoxicity of current adhesive systems on human dental pulp cells. MATERIALS AND METHODS: The adequate density of human pulp cells was observed from the ready cell line. The passaging was performed and the 3rd passage cells were selected. Adhesive systems and MTA were used on the cultures. Trypan blue staining was conducted on the cells at the 1st, 2nd, 3rd days and a count of live and dead cells using a light microscope. The dead cells whose membrane integrity was impaired by staining with trypan blue and the viability rate was determined using live and dead cell numbers. Data analysis was performed using IBM SPSS Statistics 22. RESULTS: A significant difference in vialibity rates between adhesive systems was observed on the first day. No significant statistical differences were observed on the 2nd and 3rd days (p < 0.05). CONCLUSION: Futurabond M showed similar biocompatibility with MTA on human pulp cells and it can be applied in cavities with 1-1.5 mm hard tissue between pulp and dentine.

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

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

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

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

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

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

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 dentin bonding agents.

This study sought to evaluate the cytotoxicity of 5 dentin bonding agents (Admira Bond, Adper Single Bond Plus, Clearfil SE Bond, Clearfil S3 Bond, and Heliobond) by XTT assay using human gingival fibroblast cells. Samples of dentin bonding agents were prepared on a black 96-well microplate, and the cytotoxicity of each bonding material was measured every 24 hours for 7 days, then on Days 14, 21, and 28. One-way ANOVA and Bonferroni post hoc tests were used for statistical analyses. All 5 materials were evaluated as severely cytotoxic (P < 0.001) on the first day, with cell viabilities ranging from 6% to 24%. All the bonding agents showed severe cytotoxicity with viability results <10%. With the exception of Adper Single Bond Plus, toxicity continued to Day 28 for all compounds. The utmost care must be considered during the clinical utilization of dentin bonding agents to keep them within the area of restoration and prevent their contact with adjacent tissues.

Cytotoxic effects on human dental pulp stem Cells after exposure to adhesive bonding agents.

Studies regarding cytotoxic effects attributed to the use of adhesive bonding agents on pulp tissue are not conclusive. To point out whether these materials are safe for clinical use, in vivo exposure of dental pulp to adhesive bonding agents was simulated using an experimental setup in which Human Dental Pulp Stem Cells (hDPSC) are exposed to the action of two kinds of adhesives: self-etching adhesives and two-step bonding agents through a dentine barrier. Cytotoxic effects on these cells were evaluated by MTT assay protocol and fluorescence microscopy, and their results were contrasted to those obtained through Raman spectra taken on single hDPSCs. Overall, no significant cytotoxic effects were observed by combining all the techniques, and cell viability close to 90% was achieved for a dentine barrier of at least 1 mm thick. Moreover, Raman spectroscopy was able to detect structural DNA damage in some dental pulp cells when exposed to two-step bonding agents, suggesting that this technique could be considered a complementary tool with the potential to evaluate cell toxicity beyond cell viability.

Tetrahydrofuran as solvent in dental adhesives: cytotoxicity and dentin bond stability.

OBJECTIVES: The aim of this study was to investigate the cytotoxicity and 1-year dentin bond stability of solvated etch-and-rinse dental adhesives based on tetrahydrofuran (THF), acetone, or ethanol, containing water or not. MATERIALS AND METHODS: Seven primers were prepared using the following solvents: THF, acetone, ethanol, water, THF/water, acetone/water, and ethanol/water. Bovine dentin was used, and specimens for microtensile bond strength (µTBS) test were prepared. Specimens were tested after storage in distilled water for 24 h or 1 year. Cytotoxicity of the solvents was evaluated in 3T3/NIH mouse fibroblasts using a colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay after exposure for 24 h. RESULTS: No significant differences were detected among solvents after storage for 24 h, except for the water-based group, which showed the lowest µTBS values. After storage for 1 year, the THF-based adhesive system resulted in more stable bonds. Yet, THF showed an intermediate cytotoxicity when compared with the other solvents, being less toxic than phosphate monomer and similar to 2-hydroxyethyl methacrylate. CONCLUSION: THF seems to be a suitable solvent for adhesive systems. CLINICAL RELEVANCE: THF is a promising solvent that can be used to improve dentin bond stability.

Cytotoxicity test of dentin bonding agents using millipore filters as dentin substitutes in a dentin barrier test.

OBJECTIVES: The purpose of this study was to find proper dentin substitute for standardized dentin barrier test and perform the cytotoxicity test of commercial bonding agents with the proper substitute. MATERIALS AND METHODS: The three-dimensional cells attached to dentin disc or millipore filters as the dentin substitute were tested in a dentin barrier test by perfusion. MTT assay was performed as an evaluation method for the cell survival rate. The cytotoxicity test of serial phenol dilution by bovine dentin disc was done to determine a standard toxic material, and the test of this proper phenol by using various millipore combinations was performed to find the suitable dentin substitute. Also, the cytotoxicity test of bonding agents was performed by this standardized substitute. The cell viability was expressed as percentages of untreated group. RESULTS: Phenol concentration of 0.05 % was selected as the standard toxic material. The different combinations of millipore filters--two sheets of 0.45 µm, two sheets of 0.22 µm, and the combination of 0.65, 0.45, and 0.22 µm--showed similar cytotoxicity to natural dentin discs by 0.05 % phenol (p > 0.05). The millipore combination of 0.65, 0.45, and 0.22 µm that had structural similarity to natural dentin discs was used as the substitute for cytotoxicity test of bonding agents. The toxic level of Adper Prompt L-Pop using the selected substitute was significantly the highest among four kinds of dentin bonding agents (p < 0.05). Also, the dentin barrier test by the substitute showed constant results compared with the one by the natural dentin disc. CONCLUSIONS: The millipore filter combination of 0.65, 0.45, and 0.22 µm could be used as the substitute for the cytotoxicity test of materials applied to dentin. CLINICAL RELEVANCE: Dentin barrier test by standardized substitutes would be helpful for considering the potential toxicity of dentin bonding agents prior to clinical adaptations and reducing the variations of natural bovine dentin that has individually different characteristics.

Inhibition of cell survival, viability and proliferation by dentin adhesives after direct and indirect exposure in vitro.

OBJECTIVES: The influence of dentin adhesive systems (Scotchbond Multi-Purpose, XP Bond, Xeno V, Clearfil Protect Bond, AdheSE) on cell survival, viability and proliferation was characterized after direct and indirect exposure using different cell culture techniques. MATERIALS AND METHODS: The primers and cured bonding parts were directly exposed to cells using cell culture inserts, and complete materials were analyzed in a dentin barrier test. Cell responses were examined in 3T3 mouse fibroblasts after 24- and 72-h exposure periods by the estimation of total cell numbers (survival), apoptosis (viability) and cell proliferation. RESULTS: Cell numbers were effectively reduced by the primers of AdheSE, Protect Bond, and Scotchbond Multi-Purpose as well as XP bond after direct exposure in a cell culture insert test device. Likewise, Scotchbond Multi-Purpose primer induced a rate of apoptosis (93.9%) even higher than detected with Protect Bond primer (91.6%). Cell proliferation was entirely inhibited by primers and by Xp Bond as well. The Scotchbond Multi-Purpose was most cytotoxic in a dentin barrier test device after a 24-h indirect exposure. It also increased the percentage of cells in apoptosis to 15.4% compared to untreated controls. CONCLUSION: Unpolymerized primers of dentin adhesives were more cytotoxic than polymerized bonding counterparts. Moreover, total etch dentin adhesives were more cytotoxic than self-etch adhesives. CLINICAL RELEVANCE: When dentin adhesives are used in deep cavities without a protective dentin barrier the leachable hydrophobic and hydrophilic component of dentin adhesive systems can penetrate to the pulp and may induce cytotoxic responses in pulp tissues.

Potential implication of N-acetylcysteine detoxification on adhesive endodontics.

Methacrylate resin-based dentin adhesives and root canal sealers used for bonding of filling materials inside the root canal system are cytotoxic and result in reduction in cell proliferation to a variable extent. An in vitro study to examine the detoxifying effects of N-acetylcysteine (NAC) on four commercial adhesive systems on adhesive-induced cytotoxicity and cell survival was conducted so that the use of methacrylate resin-based materials for filling root canals could be optimized. The finding that NAC co-treatment protected the cells from adhesive-induced toxicity by increasing cellular proliferation, attenuating cell cycle arrest, and reducing cell death suggests the null hypothesis that NAC has no effect on dentin adhesive-induced cell death and cell cycle arrest should be rejected.

The influence of methodology on the comparison of cytotoxicity of total-etch and self-etch adhesive systems.

OBJECTIVES: The present study aimed to compare the in vitro cytocompatibility of two etch-and-rinse (Adper Scothbond, Optibond) and two self-etch (Clearfill SE Bond and Single Bond Universal) dental adhesives through a dentin-barrier model with human pulp fibroblasts. METHODS: Human fibroblasts were placed on a plastic device containing 500µm human dentin discs treated with each adhesive or without treatment (control). Other groups were directly exposed to media conditioned with adhesive samples according to ISO 10993-5:2009. After 24h exposure, cell viability was assessed by XTT, and released inflammatory mediators were detected with a multiparametric immunoassay. RESULTS: The standardized test without barrier indicated both etch-and-rinse adhesives and self-etch as cytotoxic, promoting viabilities under 70% of the control group (p<0.05). The dentin-barrier model identified increased cell viability for self-etch adhesives, with Clearfill SE Bond identified as non-cytotoxic. The immunoassay evidenced high rates of cytokines by cells exposed to the conditioned media of Adper Scotchbond, Optibond S, and Single Bond Universal. CONCLUSIONS: The use of a dentin-barrier in vitro model detected a better biocompatibility for self-etching adhesives and, in the case of Clearfill SE Bond, with a reversion from cytotoxic to biocompatible when compared to the indirect standardized test. CLINICAL SIGNIFICANCE: The use of a dentin-barrier in vitro model was able to detect a better biocompatibility for self-etching adhesives when compared to the indirect standardized test and presents itself as a predictive in vitro method for assessing the cytotoxicity of dental restorative materials that may simulate the clinical condition more accurately.

Genotoxicity evaluation of dentine bonding agents by comet assay.

AIM: To evaluate the genotoxicity of four different adhesives, Clearfil SE Bond, SL Bond, i Bond and Clearfil Protect Bond and the primers of Clearfil SE Bond and Clearfil Protect Bond. METHODOLOGY: Genotoxicity assessment of the adhesives and primers was carried out in vitro in human lymphocytes at different elution concentrations, using the alkaline single-cell gel electrophoresis technique (comet assay). After the incubation of lymphocytes with varying volumes of the test agent, cells were embedded in a low-melting-point agarose suspension and then lysed in alkaline (pH>13) conditions. Electrophoresis was performed on the suspended lysed cells followed by visual analysis with staining of DNA. Fluorescence was than calculated to determine the extent of DNA damage using imaging software. Statistical comparison of the results was carried out by one-way analysis of variance (anova). RESULTS: A significant increase (P<0.001) compared to untreated controls in DNA damage was observed with 'Clearfil Protect Bond' and 'Clearfil SE Bond' primer in human lymphocytes at concentrations of 2.5 and 5.0 mg mL(-1). Clearfil Protect Bond and Clearfil SE Bond adhesives induced significant (P < 0.001) DNA damage only at the higher concentration of 5.0 mg mL(-1) . No significant increase in DNA damage was observed with SL Bond and i Bond. No significant DNA damage was observed with any dentine bonding agents at the lower concentration of 1.25 mg mL(-1) . CONCLUSIONS: 'Clearfil Protect Bond' and 'Clearfil SE Bond' primers/adhesives increased DNA damage in human peripheral lymphocytes in high doses.

Influence of the activation mode of a self-etch resin-based luting cement upon the metabolism of odontoblast-like cells.

PURPOSE: To evaluate the cytotoxicity of a self-etch resin-based luting cement, RelyXUnicem (RXU) upon chemical or dual cure and with or without interposition of IPS d.SIGN (IPSD) or IPS Empress II (IPSE) ceramic discs between cement and light source. METHODS: 112 RXU specimens were subjected to different curing conditions and incubated in culture medium (DMEM) to obtain extracts. The following groups were formed: G1: DMEM (control); G2: dual RXU; G3: chemical RXU; G4: dual RXU+IPSD; G5: chemical RXU+IPSD; G6: dual RXU+IPSE; and G7: chemical RXU+IPSE. Cultured odontoblast-like cells were incubated for 24 hours in contact with the extracts. Data from cell metabolism (CM), total protein dosage (TPD) and alkaline phosphatase activity (APA) were obtained and analyzed statistically (alpha = 0.05; Kruskal Wallis and Mann-Whitney tests). Cell morphology was analyzed by SEM. RESULTS: CM and APA were significantly lower in G3 and G7 than in G1 (P<0.05). Significant TPD decrease occurred in G5 and G7 compared to G1 (P<0.05). Only G4 and G6 presented CM changes. RXU caused no cytotoxicity when subjected to dual cure without ceramic interposition. However, mild cytopathic effects were observed after chemical setting without ceramic interposition, and after chemical and dual activation under ceramic discs.

The cytotoxic effects of resin-based sealers on dental pulp stem cells.

AIM: To evaluate the effect of four current resin-based adhesives on expanded ex vivo human dental pulp mesenchymal stem cells (DP-MSCs). METHODOLOGY: Dental pulp mesenchymal stem cells were derived from dental pulps of ten donors. After in vitro isolation, dental pulp stem cells were analysed using flow cytometry. The immunophenotype of DP-MSCs disclosed the homogeneous expression of the mesenchymal-related antigens CD29, CD44, CD73, CD90, CD105, CD166. DP-MSCs were exposed to four different commercially available bonding systems (CMF Bond, Prime&Bond NT, Clearfil S(3) Bond, XP Bond), and after 24, 48 and 72 h of incubation the morphological features and the cell growth were analysed. Moreover, the cell viability was evaluated at the same times by MTT assay. Data were statistically analysed using a two-way anova and Holm-Sidak method (alpha set at 0.05). RESULTS: Significant differences were observed between the four groups when comparing DP-MSCs appearance. DP-MSCs survived and proliferated without inhibition in the presence of CMF Bond adhesive. On the contrary, microscopic evaluation of the other three groups revealed extensive cytotoxic effects from the dentine bonding agents. The MTT assay revealed no statistically significant differences in cell viability after 72 h between the control group and CMF Bond group. All the other experimental groups had statistically lower optical density values. CONCLUSIONS: CMF Bond adhesive allowed human dental pulp stem cells to survive and proliferate. All of the other dentine bonding agents had extensive cytotoxic effects.

Cytotoxicity of dentine bonding agents on human pulp cells is related to intracellular glutathione levels.

AIM: To evaluate ex vivo the mechanisms of cytotoxicity of dentine bonding agents in human pulp cells in vitro. METHODOLOGY: Human pulp cells were obtained from impacted third molars with informed consent and then cultured using an explant technique. Set specimens from Clearfil SE Bond (CB), Prime & Bond 2.1 (PB), and Single Bond (SB) were eluted with culture medium. Cytotoxicity was judged using an assay of tetrazolium bromide reduction. To determine whether glutathione (GSH) levels were important in the cytotoxicity of dentine bonding agents, cells were pretreated with 2-oxothiazolidine-4-carboxylic acid (OTZ) to boost GSH levels or buthionine sulfoximine (BSO) to deplete GSH. Three replicates of each dentine bonding agents were performed in each test. All assays were repeated three times to ensure reproducibility. Statistical analysis was by one-way analysis of variance (anova). Tests of differences of the treatments were analysed by Duncan's test. RESULTS: Clearfil SE Bond, PB, and SB were cytotoxic to pulp cells in a concentration-dependent manner (P<0.05). The cytotoxicity was upregulated by dentine bonding agents in the following order: PB>SB>CB. Addition of OTZ extracellularly protected the pulp cells from dentine bonding agents-induced cytotoxicity (P<0.05). Addition of BSO enhanced pulp cell death on dentine bonding agents-induced cytotoxicity (P<0.05). CONCLUSIONS: Dentine bonding agents have significant potential for pulpal toxicity. GSH depletion could be the mechanism for dentine bonding agents-induced cytotoxicity.

Physicochemical properties, sealing ability, bond strength and cytotoxicity of a new dimethacrylate-based root canal sealer.

BACKGROUND/PURPOSE: Resin-based root canal sealer can bond to dentin and establish a hermetic seal. The aim of this study was to evaluate the physicochemical properties, sealing ability, cytotoxicity and bond strength of a new resin-based root canal sealer (NRCS). METHODS: The physicochemical properties were assessed by the flow, setting time, solubility, film thickness, radiopacity and dimensional changes. Sixty premolar root samples were filled with either Resilon/NRCS or Resilon/Epiphany and sectioned perpendicularly at the long axis at 2 mm below the cemento-enamel junction into 1-mm serial slices. The bond strength was tested by a universal testing machine. The glucose microleakage model was used to test the sealing ability. Elutes of NRCS and Epiphany were co-cultured with human periodontal ligament cells to test the cytotoxicity. RESULTS: All the physicochemical properties of NRCS conformed to ISO 6876:2001(E). The root samples filled with Resilon/NRCS had significantly less leakage (p < 0.01) and greater bond strength (p < 0.001) than the Resilon/Epiphany group had. Environmental scanning electron microscopy showed that Resilon/NRCS filling material was intimately bonded to the root dentin. Although NRCS was slightly toxic to human periodontal ligament cells, its cytotoxicity was significantly less than that of Epiphany (p < 0.01) CONCLUSION: NRCS has better physicochemical and sealing properties, as well as lower cytotoxicity and microleakage than Epiphany has.

In vitro genotoxicity of root canal sealers.

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

In vitro cytotoxicity of orthodontic primers.

OBJECTIVES: The aim of this study was to evaluate the cytotoxicity of four orthodontic primers: Transbond XT and Transbond MIP (3M, USA), Eagle Fluorsure (American Orthodontics, USA) and Ortho Solo (Ormco, USA). MATERIALS AND METHODS: Balb 3T3 cells were exposed to different concentrations of primers (0-0.25 mg/ml). Mitochondrial dehydrogenase activity was evaluated by MTT assay and cell necrosis was measured by flow cytometry (propidium iodide staining). RESULTS: All the materials decreased cell viability in a dose related manner. Cytotoxicity of orthodontic primers based on concentrations which caused a 50% decrease of mitochondrial activity was ranked as follows: Transbond XT (45.57 mg/ml) > Eagle Fluorsure (49.27 mg/ml) > Transbond MIP (64.35 mg/ml) > Ortho solo (70.09 mg/ml). CONCLUSIONS: Our results suggest that the cytotoxic potencies demonstrated by orthodontic primers might be of clinical relevance since they disturbed cell metabolism and induced cell death in monolayer cultures.

Mechanical-physicochemical properties and biocompatibility of catechin-incorporated adhesive resins.

OBJECTIVES: Several anti-proteolytic dentin therapies are being exhaustively studied in an attempt to reduce dentin bond degradation and improve clinical performance and longevity of adhesive restorations. This study assessed the effect of epigallocatechin-3-gallate (EGCG) on long-term bond strength when incorporated into adhesives. MATERIAL AND METHODS: Adhesive systems were formulated with EGCG concentrations of 0 wt%: (no EGCG; control); 0.5 wt% EGCG; 1.0 wt% EGCG, and 1.5 wt% EGCG. Flexural strength (FS), modulus of elasticity (ME), modulus of resilience (MR), compressive strength (CS), degree of conversion (DC), polymerization shrinkage (PS), percentage of water sorption (%WS), percentage of water solubility (%WL) and cytotoxicity properties were tested. Dentin microtensile bond strength (µTBS) was evaluated after 24 h and again after 6 months of water storage. The adhesive interface was analyzed using scanning electron microscopy (SEM). RESULTS: No significant differences were found among the groups in terms of FS, ME, MR, CS and PS. EGCG-doped adhesives increased the DC relative to the control group. EGCG concentrations of 1.0 wt% and 0.5 wt% decreased the WS of adhesives. WL decreased in all cases in which EGCG was added to adhesives, regardless of the concentration. EGCG concentrations of 1.0 wt% and 0.5 wt% reduced cytotoxicity. EGCG concentrations of 1.0 wt% and 0.5 wt% preserved µTBS after 6 months of storage, while 1.5 wt% EGCG significantly decreased µTBS. SEM: the integrity of the hybrid layer was maintained in the 0.5 wt% and 1.0 wt% EGCG groups. CONCLUSION: EGCG concentrations of 1.0 wt% and 0.5 wt% showed better biological and mechanical performance, preserved bond strength and adhesive interface, and reduced cytotoxicity.