Adhesive resin induces apoptosis and cell-cycle arrest of pulp cells

Applications of Antioxidants in Dental Procedures

As people are paying more and more attention to dental health, various dental treatment procedures have emerged, such as tooth bleaching, dental implants, and dental restorations. However, a large number of free radicals are typically produced during the dental procedures. When the imbalance in distribution of reactive oxygen species (ROS) is induced, oxidative stress coupled with oxidative damage occurs. Oral inflammations such as those in periodontitis and pulpitis are also unavoidable. Therefore, the applications of exogenous antioxidants in oral environment have been proposed. In this article, the origin of ROS during dental procedures, the types of antioxidants, and their working mechanisms are reviewed. Additionally, antioxidants delivery in the complicated dental procedures and their feasibility for clinical applications are also covered. Finally, the importance of safety assessment of these materials and future work to take the challenge in antioxidants development are proposed for perspective.

Assessment of the Influence of Various Concentrations of Sodium Hypochlorite on Stem Cell Derived From Human Exfoliated Deciduous Teeth (SHED) Proliferation and Differentiation

Objectives  Previous research has established that sodium hypochlorite (NaOCl) has a detrimental effect on dental stem cell viability and maturation. However, a review of the literature revealed no study evaluating the response of NaOCl to the survival of stem cells derived from human exfoliated deciduous teeth (SHEDs). Hence, the aim of the present trial was to assess the influence of various dilutions of NaOCl on SHED proliferation and differentiation. Materials and Methods The 5.25% NaOCl solutions at concentrations of 0.5, 0.1, 0.025, 0.0125, and 0.005 mg/ml were used to assess the response to SHED proliferation and differentiation through methyl tetrazolium (MTT) assay, alkaline phosphatase (ALP) assay, and reverse transcription polymerase chain reaction gene expression analysis at various time point intervals. Results  MTT assay showed that the viability of SHEDs decreased with an increase in the concentration of NaOCl and an increase in incubation time. The ALP activity decreased with an increase in the concentration of NaOCl up to 14 days of incubation. However, the ALP activity of all the test specimens further decreased after 14 days of incubation. The gene expression levels of osteocalcin, dentin sialophosphoprotein, and STRO-1 were statistically significant when compared to the control after one, three, and seven days of incubation. Conclusion  Different doses of NaOCl other than 0.5 mg/ml revealed encouraging outcomes in terms of proliferation, long-term ALP functioning, and odontogenic differentiation potential when cultivated in SHEDs.

Dental resin monomers induce early and potent oxidative damage on human odontoblast-like cells

Resin-based dental materials consist of filler particles and different monomers that are light cured in situ to re-establish dental function and aesthetics. Due to the degree of conversion of adhesive polymers, the monomers triethyleneglycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) are released in relatively high amounts and are susceptible to degradation, acting as bioactive compounds and affecting cell and tissues. This study aimed to assess the effect of HEMA and TEGDMA exposure on metabolic activity, membrane integrity, and cell survival of human odontoblast-like cell (hOLCs). Exposure to resin monomers for 24 h induced major changes in cell membrane integrity, metabolic activity, and survival, which were measured by the calcein method and lactate dehydrogenase release. Increased and early reactive oxygen species (ROS) production was observed leading to degradative oxidation of membrane lipids identified as malondialdehyde production. Severe alteration in mitochondria occurred due to transmembrane mitochondrial potential collapse, possibly inducing activation of apoptotic cell death. hOLCs exposure to resin monomers modified the cell redox potential, with consequences on membrane permeability and integrity, including mitochondrial function. Lipid peroxidation appears to be a key phenomenon for the membrane structures oxidation after HEMA and TEGDMA exposure, leading to cell death and cytotoxicity. hOLCs respond early by differential induction of adaptive mechanisms to maintain cell homeostasis. Modulation of oxidative stress-induced response involves the regulation of genes that encode for antioxidant proteins such as catalase and heme oxygenase-1; regulation that functions as a critical protection mechanism against oxidative cell damage induced by HEMA and TEGDMA. Ascorbic acid as an antioxidant substance mitigates the oxidative damage associated with exposure to monomers.

Genotoxic and cytotoxic potential of methacrylate-based orthodontic adhesives

Objectives

The biocompatibility of methacrylate-based adhesives is a topic that is intensively discussed in dentistry. Since only limited evidence concerning the cyto- and genotoxicity of orthodontic adhesives is available, the aim of this study was to measure the genotoxic potential of seven orthodontic methacrylate-based adhesives.

Materials and methods

The XTT assay was utilized to determine the cytotoxicity of Assure Plus, Assure Bonding Resin, ExciTE F, OptiBond Solo Plus, Scotchbond Universal Adhesive, Transbond MIP, and Transbond XT after an incubation period of 24 h on human gingival fibroblasts. We also performed the γH2AX assay to explore the genotoxic potential of the adhesives within cytotoxic dose ranges after an incubation period of 6 h.

Results

The XTT assay showed a concentration-dependent reduction in cell viability. The decrease in cellular viability was in the same dose range most significant for Assure Plus, rendering it the adhesive material with the highest cytotoxicity. Employing the γH2AX assay, a concentration-dependent increase in H2AX phosphorylation was detected, indicating induction of DNA damage.

Conclusions

For most products, a linear correlation between the material concentration and γH2AX foci was observed. The most severe effect on γH2AX focus induction was found for Transbond MIP, which was the only adhesive in the test group containing the co-initiator diphenyliodonium hexafluorophosphate (DPIHP).

Clinical relevance

The data indicate that orthodontic adhesives, notably Transbond MIP, bear a genotoxic potential. Since the study was performed with in vitro cultivated cells, a direct translation of the findings to in vivo exposure conditions should be considered with great diligence.

Molecular Response of Pulp Fibroblasts after Stimulation with Pulp Capping Materials

This in vitro study evaluated cell viability and metabolism, nitric oxide release and production of two chemokines and one cytokine by cultured human dental pulp fibroblasts (HDPF) in contact with two glass ionomer cements (Ketac Molar-KM and Vitrebond-VB), Single Bond (SB) and calcium hydroxide (Dycal-DY). Cultures of HDPF were established by means of an explant technique. The specimens were prepared under sterile conditions and in disks measuring 5 mm x 2 mm obtained from a prefabricated mold and placed on a permeable membrane to avoid direct contact with the cells. Cytotoxicity was assessed by Trypan Blue exclusion method and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Nitric oxide release in cell supernatant was detected by the Griess Method whereas stromal derived factor-1 alpha (SDF-1α or CXCL12), chemokine (C-X-C motif) ligand 8 [Interleukin 8 (IL-8 or CXCL8)] and interleukin-6 (IL-6) were detected by ELISA. RT-qPCR was employed for gene expression analysis. Statistical analyses were performed by One-way ANOVA followed by Tukey's post hoc test for materials independent of the time, and Two-way ANOVA followed by Bonferroni correction test for the comparisons between materials and experimental time (p<0.05). Cytotoxic tests showed significant differences only for DY. Protein levels and mRNA expression were significantly increased for IL-8 for both periods of time. IL-6 production increased when fibroblasts were stimulated by KM. SDF-1α protein production and mRNA expression were not affected by any of the materials. There was a decrease in nitrate/nitrite levels only for KM. Although DY caused intense cell death and did not stimulate the production of the inflammatory mediators evaluated in this work, it is known that this event seems to be fundamental for the process of repair of the pulp tissue and formation of mineralized barrier. KM and VB increased production of proteins related to the inflammatory process, thus favoring tissue repair. Therefore, although these glass ionomer cements did not lead to large cell death, they should be used with caution.

Hot air stream reduces cytotoxicity of light-cured calcium hydroxide based cements

Background

The light-cured calcium hydroxide based cements have incomplete polymerization and unconverted monomers can cause pulp cell damage. The aim of this study was to evaluate the influence of a warm and hot air stream on the cytotoxicity of light-cured calcium hydroxide based cements.

Material and Methods

The materials Dycal (conventional cement), Biocal, Hidrox-Cal, and Ultra-Blend Plus (light-cured calcium hydroxide cements) were submitted to cytotoxicity analysis after polymerization, without vs. with previous heat treatment with a warm (37°C) and a hot (60°C) air stream. Following polymerization, cements were maintained in culture medium for 24 hours and 7 days, and subjected to the MTT test. Data were analyzed using analysis of variance (ANOVA) followed by post-hoc Student-Newman-Keuls (<0.05).

Results

The results indicated significant differences between the materials according to their composition, i.e., light-cured cements treated with a jet of warm air showed similar cytotoxicity levels to those observed for conventional cement, suggesting that they may be considered alternatives in cases requiring pulp-capping treatment.

Conclusions

Application of a hot air stream reduced cytotoxicity of materials tested.

Key words:Dental pulp capping, dental cements, calcium hydroxide, cell survival.

Dental Pulp Fibroblasts Response after Stimulation with HEMA and Adhesive System

This study evaluated in vitro cell viability and metabolism, nitric oxide release and production of chemokines by cultured human dental pulp fibroblasts (DPF) under contact with HEMA and Single Bond. Cultures of DPF were established by means of an explant technique. Once plated, cells were kept under contact with increasing concentrations of HEMA (10, 100 and 1000 nM) or Single Bond (SB) [10-fold serially diluted in culture medium (10-4, 10-3 and 10-2 v/v)] and also with polymerized SB components. Cytotoxicity was assessed by Trypan Blue exclusion method and MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Nitric oxide release on cell supernatant was detected by Griess Method whereas chemokines (CXCL12 and CXCL8) were detected by ELISA. RT-qPCR was employed for chemokines gene expression analysis. Cytotoxic tests showed significant differences for SB 10-2. None of the tested materials significantly altered NO levels. Protein levels of CXCL12 were significantly decreased only by HEMA. On the other hand, while CXCL12 mRNA remained unaltered, gene expression of CXCL8 had significant decrease with all materials, except for polymerized SB. In conclusion, Single Bond and HEMA at various concentrations, decreased expression and production of molecules involved in inflammatory processes and, therefore, the use of adhesive systems such as pulp capping materials must be viewed with caution due to its large cytotoxic effect when in close contact with the pulp.

Epigenetic Approaches to the Treatment of Dental Pulp Inflammation and Repair: Opportunities and Obstacles

Concerns over the cost and destructive nature of dental treatment have led to the call for novel minimally invasive, biologically based restorative solutions. For patients with toothache, this has resulted in a shift from invasive root-canal-treatment (RCT) toward more conservative vital-pulp-treatment (VPT) procedures, aimed to protect the pulp and harness its natural regenerative capacity. If the dental pulp is exposed, as long as the infection and inflammation can be controlled, conservative therapies can promote the formation of new tertiary dentine in a stem cell-led reparative process. Crucially, the volume and quality of new dentine is dependent on the material applied; however, currently available dental-materials are limited by non-specific action, cytotoxicity and poor clinical handling. Looking to the future, an improved understanding of the cellular regulators of pulpal inflammation and associated repair mechanisms is critical to predict pulpal responses and devise novel treatment strategies. Epigenetic modifications of DNA-associated proteins and the influences of non-coding RNAs have been demonstrated to control the self-renewal of stem cell populations as well as regulate mineralised tissue development and repair. Notably, the stability of microRNAs and their relative ease of sampling from pulpal blood highlight their potential for application as diagnostic inflammatory biomarkers, while increased understanding of their actions will not only enhance our knowledge of pulpal disease and repair, but also identify novel molecular targets. The potential therapeutic application of epigenetic modifying agents, DNA-methyltransferase-inhibitors (DNMTi) and histone-deacetylase-inhibitors (HDACi), have been shown to promote mineralisation and repair processes in dental-pulp-cell (DPC) populations as well as induce the release of bioactive dentine-matrix-components. Consequently, HDACis and DNMTis have the potential to enhance tertiary dentinogenesis by influencing the cellular and tissue processes at low concentrations with minimal side effects, providing an opportunity to develop a topically placed, inexpensive bio-inductive restorative material. The aim of this review is to highlight the potential role of epigenetic approaches in the treatment of the damaged dental pulp, considering the opportunities and obstacles, such as off-target effects, delivery mechanisms, for the therapeutic use of miRNA as an inflammatory biomarker or molecular target, before discussing the application of HDACi and DNMTi to the damaged pulp to stimulate repair.

Cytotoxicity of gypsum-based biomaterial for direct pulp capping using stem cells from human exfoliated deciduous teeth

Aim:

The aim of this study was to evaluate the cytotoxicity effects of experimental gypsum-based biomaterial prepared with various concentrations of chitosan (Gyp-CHT).

Materials and Methods:

The study was performed using cell viability assay for mitochondrial dehydrogenase activity in stem cells from human exfoliated deciduous teeth (SHED), after 1, 2, and 3 days of exposure to the biomaterial extracts of varying concentrations. Differences in mean cell viability values were assessed by one-way analysis of variance, followed by Dunnett T3 post hoc test for multiple comparisons (P < 0.05).

Results:

The cell viability to Gyp-CHT in low extract concentrations was statistically similar to that of the control and different from that of high extract concentrations. Gyp-5% CHT showed the highest percentage of cell viability with 110.92%, 108.56%, and 109.11%. The cell viability showed a tendency toward increment with low extract concentration and no constant effect of CHT on cell viability toward higher or lower.

Conclusions:

Gyp-CHT biomaterial has no cytotoxic effects on the cultured SHED.

In vitro dentin barrier cytotoxicity testing of some dental restorative materials

OBJECTIVES

To investigate the cytotoxicity of four dental restorative materials in three-dimensional (3D) L929 cell cultures using a dentin barrier test.

METHODS

The cytotoxicities of light-cured glass ionomer cement (Vitrebond), total-etching adhesive (GLUMA Bond5), and two self-etching adhesives (GLUMA Self Etch and Single Bond Universal) were evaluated. The permeabilities of human dentin disks with thicknesses of 300, 500, and 1000μm were standardized using a hydraulic device. Test materials and controls were applied to the occlusal side of human dentin disks. The 3D-cell scaffolds were placed beneath the dentin disks. After a 24-h contact with the dentin barrier test device, cell viabilities were measured by performing MTT assays. Statistical analysis was performed using the Mann-Whitney U test.

RESULTS

The mean (SD) permeabilities of the 300-μm, 500-μm, and 1000-μm dentin disks were 0.626 (0.214), 0.219 (0.0387) and 0.089 (0.028) μlmin^-1cm^-2cm H₂O^-1. Vitrebond was severely cytotoxic, reducing the cell viability to 10% (300-μm disk), 17% (500μm), and 18% (1000μm). GLUMA Bond5 reduced the cell viability to 40% (300μm), 83% (500μm), and 86% (1000μm), showing moderate cytotoxicity (300-μm) and non-cytotoxicity (500-μm and 1000-μm). Single Bond Universal and GLUMA Self Etch did not significantly reduce cell viability, regardless of the dentin thicknesses, which characterized them as non-cytotoxic.

CONCLUSIONS

Cytotoxicity varied with the materials tested and the thicknesses of the dentin disks.

CLINICAL SIGNIFICANCE

The tested cytotoxicity of materials applied on 300-, 500-, and 1000-μm dentin disks indicates that the clinical use of the test materials (excepting self-etching adhesives) in deep cavities poses a potential risk of damage to the pulp tissues to an extent, depending on the thickness of the remaining dentin.

Cytotoxicity of Two-step Self-etching Primer/Adhesives on L929 Cells

The cytotoxicity of four self-etching primer/adhesive systems (Clearfil® SE Bond, Clearfil® Protect Bond, Mac Bond® II and FL® Bond) was tested against L929 fibroblasts. The primer or adhesive component of each adhesive system was diluted serially with the culture medium at a ratio of 1:1,000 and 1:4,000 (v/v). Cytotoxicity was identified by adding L929 cells in 24-well culture plates at an initial density of 35,000 cells mL 1. The cells were maintained for 5 days; every 24h, the medium was changed with fresh medium containing specific dilutions of the primer or adhesive components of the test materials. Cytotoxicity was assessed quantitatively at 24, 48, 72, 96 and 120h. Physiological and pathological cellular changes as well as reactions and growth of the cell cultures were examined under an inverted microscope. All self-etching systems were found to be cytotoxic to varying degrees; more pronounced toxic effects were observed at lower dilution (1:1,000 [v/v]). The adhesive components of Mac Bond® II and FL® Bond showed the highest cytotoxicity at 1:1,000 (v/v). The primer and adhesive of Clearfil® SE Bond, the primer of Mac Bond® II and the antibacterial monomer (MDPB)-containing Clearfil® Protect Bond (at 1:4,000 [v/v]) were relatively less cytotoxic.

Cytotoxic effects of one-step self-etching adhesives on an odontoblast cell line

The aim of this study was to evaluate the cytotoxic effects of one-step self-etching adhesives. Cells from an immortalized mouse odontoblast cell line (MDPC-23) were cultured with six different dental adhesive systems (diluted to concentrations of 0.5% for 4 h): Adper Easy Bond (EB), Xeno V (XV), iBond (IB), AdheSE One (AO), Clearfil SE primer (CS), and Adper Single Bond 2 (SB). MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and flow cytometric apoptosis assays were used to evaluate cell viability and the rate of apoptosis. The odontoblasts were also examined under a scanning electron microscope. While all of the cultures with adhesives showed reduced viability, the viabilities in the IB and SB groups were not significantly different from the control group. Although increased apoptosis rates were observed in all of the cultures with adhesives, the rate in the SB group was not significantly different from the rate in the control. The control group showed the lowest apoptosis rate followed by the SB, AO, IB, EB, XV, and CS groups. When examined under a scanning electron microscope, control odontoblasts and the SB group exhibited relatively large cytoplasmic extensions. In contrast, in the EB and CS groups, fewer fibroblasts remained adhered to the plate surface. Cytoplasmic membrane shrinkage and cell-free areas with residual membrane fragments from dead cells were observed. In conclusion, all cultures with one-step self-etching adhesives showed increased apoptotic activity. SB, an etch-and-rinse adhesive, was comparable to the control group, and CS and EB showed the lowest odontoblast viabilities according to the MTT assay.

An in vitro evaluation of the cytotoxicity of varying concentrations of sodium hypochlorite on human mesenchymal stem cells

AIM

To evaluate and compare the cytotoxicity of various concentrations of sodium hypochlorite on immortalized human bone marrow mesenchymal stem cells (MSCs).

MATERIALS AND METHODS

The 5.25 percent sodium hypochlo-rite (NaOCl) at concentrations of 0.5, 0.1, 0.025, 0.0125, and 0.005 mg/ml were used to assess the cytotoxic effect on MSCs. Immortalized human bone marrow mesenchymal stem cells (hTERT-MSCs) were exposed to NaOCl at 5 different concentrations. Cell viability was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alamarBlue assays. The cell morphology changes were assessed with scanning electron microscopy (SEM) after exposure to 2, 4, and 24 hour incubation. The ethidium bromide/acridine orange (EB/ AO) fuorescent stain was applied to the cells in the 8-chamber slides after they were incubated with the testing agents for 2 and 4 hours to detect live and dead cells. The observations were quantitatively and qualitatively analyzed.

RESULTS

The cell viability study using MTT assay and AB assay showed significant reduction with varying concentration at 2 and 4 hours incubation period. The cell viability decreased with the higher percentage of NaOCl. The exposure time also revealed an inverse relation to the cell viability. The SEM analysis showed reduction in the number of cells and morphological alterations with 0.5 mg/ml at 2 and 4 hours compared to 0.025 mg/ml NaOCl. Destruction of the cells with structural alterations and lysis was evident under fuorescence microscope when the cells were exposed to 0.5 mg/ml NaOCl.

CONCLUSION

Within the limitations of this in vitro study it can be concluded that NaOCl is toxic to the human bone marrow MSCs. The cell lysis was evident with higher concentration of sodium hypochlorite. From the observations, it can be concluded that a lower concentration of NaOCl may be used as endodontic irrigant due to its cytotoxic properties. Further studies are mandatory to evolve a consensus on the optimal concentration of sodium hypochlorite to be used as endodontic irrigant.

One-pot synthesis of antibacterial monomers with dual biocidal modes

OBJECTIVES

The present study reported a method for preparing a blend of antibacterial quaternary ammonium silanes and quaternary ammonium methacryloxy silane (QAMS) based on the sol-gel reaction between dimethyldiethoxy silane and two trialkoxysilanes, one with an antibacterial quaternary ammonium functionality and the other with a methacryloxy functionality.

METHODS

Reaction products of the sol-gel reaction were characterised by direct infusion mass spectrometry, FTIR and proton, carbon and silicon NMR. This blend of monomers was incorporated into an experimental universal adhesive for evaluation of antimicrobial activity against Streptococcus mutans biofilms, microtensile bond strength and cytotoxicty. Retention of quaternary ammonium species on polymerised adhesive, leaching of these species from the adhesive and the ability of resin-dentine interfaces to inhibit S. mutans biofilms were evaluated over a 3-month water-ageing period.

RESULTS

The antibacterial adhesive version killed bacteria in S. mutans biofilms not only through the release of non-copolymerisable quaternary ammonium silane species (release-killing), but also via immobilised quaternary ammonium methacryloxy silane that are copolymerised with adhesive resin comonomers (contact-killing). Contact-killing was retained after water-ageing. The QAMS-containing universal adhesive has similar tensile bond strength as the control and two commercially available universal adhesives, when it was used for bonding to dentine in the etch-and-rinse mode and self-etching mode. Incorporation of the antimicrobial quaternary ammonium species blend did not adversely affect the cytotoxicity of the universal adhesive formulation.

CONCLUSIONS

Instead of using quaternary ammonium dimethacrylates and nanosilver, an alternative bimodal antimicrobial strategy for formulating antimicrobial universal dentine adhesives is achieved using the one-pot sol-gel synthesis scheme.

CLINICAL SIGNIFICANCE

The QAMS containing universal dentine adhesives with dual antimicrobial activity is a promising material aimed at preventing second caries and prolonging the longevity of resin composite restorations.

Cytocompatibility and antibacterial properties of capping materials

The aim of this study was to evaluate and compare the antimicrobial activity and cytocompatibility of six different pulp-capping materials: Dycal (Dentsply), Calcicur (Voco), Calcimol LC (Voco), TheraCal LC (Bisco), MTA Angelus (Angelus), and Biodentine (Septodont). To evaluate antimicrobial activity, materials were challenged in vitro with Streptococcus mutans, Streptococcus salivarius, and Streptococcus sanguis in the agar disc diffusion test. Cytocompatibility of the assayed materials towards rat MDPC-23 cells was evaluated at different times by both MTT and apoptosis assays. Results significantly differed among the different materials tested. Both bacterial growth inhibition halos and cytocompatibility performances were significantly different among materials with different composition. MTA-based products showed lower cytotoxicity and valuable antibacterial activity, different from calcium hydroxide-based materials, which exhibited not only higher antibacterial activity but also higher cytotoxicity.

Cytotoxicity of QMix™ endodontic irrigating solution on human bone marrow mesenchymal stem cells

Background

Debridement and disinfection of the root canal system is a crucial step in endodontic procedures. The effectiveness of irrigation relies on both the mechanical flushing action and the ability of irrigants to dissolve tissue and kill bacteria. The objective of the present study is to evaluate and compare the cytotoxicity of QMix™ root canal irrigating solution on immortalized human bone marrow mesenchymal stem cells (hTERT-MSC-C1) and to compare it with that of sodium hypochlorite (NaOCl).

Methods

Immortalized human bone marrow mesenchymal stem cells (hTERT-MSCs) were exposed to QMix™ and NaOCl. Cell viability was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alamarBlue assays. The cell morphology was studied after two hours of exposure to QMix™ and NaOCl. Scanning electron microscopy (SEM) analyses were performed after 2- and 4-hour incubation periods. Finally, ethidium bromide/acridine orange (EB/AO) fluorescent stain was applied to the cells in the 8-chamber slides after they were incubated with the testing agents for 2 hours to detect live and dead cells. The observations were tabulated and analyzed statistically.

Results

QMix™ exposure resulted in a significantly higher percentage of cell viability than NaOCl in the MTT and alamarBlue assays at three time points compared to the control. The SEM analysis demonstrated minimal morphological changes associated with cells that were exposed to the QMix™ solution, with little shrinkage and fragmentation of the cell wall. The live/dead analysis showed that the number of live cells after exposure to QMix™ was similar to that of the untreated control. No cell structure could be observed with the NaOCl group, indicating cell lysis.

Conclusion

Both the QMix™ and NaOCl solutions were toxic to human bone marrow MSCs. Each solution might have induced cell death in a different way as evidenced in the cell viability, SEM and fluorescent studies. The slower cell death induced by QMix™ might therefore be less aggressive and more acceptable to living tissues.

Histological evaluation to study the effects of dental amalgam and composite restoration on human dental pulp: an in vivo study

OBJECTIVE

To study and compare the effects of dental amalgam and composite restorations on human dental pulp.

MATERIALS AND METHODS

One hundred sound premolars scheduled for orthodontic extraction were divided equally into two groups: group A, teeth restored with silver amalgam, and group B, teeth restored with composite resin. Each group was equally subdivided into two subgroups [extracted after 24 h (A-1 and B-1) or 7 days (A-2 and B-2)], and the histological changes in the pulp related to the two different materials at the two different intervals were studied.

RESULTS

It was found that after 24 h, the inflammatory response of the pulp in teeth restored with amalgam and composite was similar (p = 1.00). However, after 7 days, the severity of the inflammatory response of the pulp in teeth restored with amalgam was less compared to that in teeth restored with composite (p = 0.045).

CONCLUSION

This study confirmed that amalgam continues to be the mechanically as well as biologically more competent restorative material. Composite could be a promising restorative material to satisfy esthetic needs for a considerable period of time. However, its biological acceptance is still in doubt.

The effect of glutathione on 2-hydroxyethylmethacrylate cytotoxicity and on resin-dentine bond strength

AIM

To evaluate the influence of reduced glutathione (GSH) application on 2-hydroxyethylmethacrylate (HEMA) cytotoxicity on rat pulpal cells and evaluate the effect of etched-dentine treatment with GSH on the immediate microtensile bond strength (μTBS) of etch-and-rinse adhesive.

METHODOLOGY

The cytotoxicity of 10 mmol L(-1) HEMA, 10 mmol L(-1) HEMA + 1 mmol L(-1) GSH, 10 mmol L(-1) HEMA + 5 mmol L(-1) GSH and 10 mmol L(-1) HEMA + 10 mmol L(-1) GSH was compared (6 h and 24 h). Cells viability was measured by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, followed by morphological observation of cells. Etched-dentine surfaces were rinsed and treated with one of the following solutions: 2% GSH, 5% GSH or 10% GSH, bonded with Adper Single Bond Plus (3M, ESPE, St. Paul, MN, USA) and restored with resin composite. The control group received no GSH treatment. After 1 day of water-storage at 37 °C, the specimens were subjected to μTBS testing. Cytotoxicity and μTBS data were analysed by one-way anova and Tukey post hoc tests (P < 0.05).

RESULTS

There were significant differences between the groups. HEMA elicited a remarkable toxic effect. 10 mmol L(-1) GSH prevented HEMA-induced damage at both exposure times. Whilst 5 mmol L(-1) GSH lost its protective effect at 24-h exposure time and 1 mmol L(-1) GSH showed no protective effect at both exposure times, GSH had no significant effect on the immediate μTBS; however, 5% GSH had higher bond strength value when compared to 10% GSH (P = 0.003).

CONCLUSION

Controlled concentrations of GSH had a protective effect against HEMA cytotoxicity. GSH had neither positive nor negative influence on μTBS.

Transdentinal cytotoxicity of experimental adhesive systems of different hydrophilicity applied to ethanol-saturated dentin

The aim of this study was to evaluate the transdentinal cytotoxicity of experimental adhesive systems (EASs) with different hydrophilicity and dentin saturation solutions on odontoblast-like cells. One hundred 0.4-mm-thick dentin discs were mounted in in vitro pulp chambers and assigned to 10 groups. MDPC-23 cells were seeded onto the pulpal side of the discs, incubated for 48h. The EASs with increasing hydrophilicity (R1, R2, R3 and R4) were applied to the occlusal side after etching and saturation of etched dentin with water or ethanol. R0 (no adhesive) served as controls. R1 is a non-solvated hydrophobic blend, R2 is similar to a simplified etch-and-rinse adhesive system and R3 and R4 are similar to self-etching adhesives. After 24h, cell metabolism was evaluated by MTT assay (n=8 discs) and cell morphology was examined by SEM (n=2 discs). Type of cell death was identified by flow cytometry and the degree of monomer conversion (%DC) was determined by infrared spectroscopy (FTIR) after 10s or 20s of photoactivation. Data were analyzed by the Kruskal-Wallis and Mann-Whitney tests (α=0.05). Dentin saturation with ethanol resulted in higher necrotic cell death ratios for R2, R3 and R4 compared with water saturation, although R2 and R3 induced higher SDH production. Photoactivation for 20s significantly improved the %DC of all EASs compared with 10s. A significant positive correlation was observed between the degree of hydrophilicity and %DC. In conclusion, except for R1, dentin saturation with ethanol increased the cytotoxicity of EASs, as expressed by the induction of necrotic cell death.

Quaternary ammonium silane-functionalized, methacrylate resin composition with antimicrobial activities and self-repair potential

The design of antimicrobial polymers to address healthcare issues and minimize environmental problems is an important endeavor with both fundamental and practical implications. Quaternary ammonium silane-functionalized methacrylate (QAMS) represents an example of antimicrobial macromonomers synthesized by a sol-gel chemical route; these compounds possess flexible Si-O-Si bonds. In present work, a partially hydrolyzed QAMS co-polymerized with 2,2-[4(2-hydroxy 3-methacryloxypropoxy)-phenyl]propane is introduced. This methacrylate resin was shown to possess desirable mechanical properties with both a high degree of conversion and minimal polymerization shrinkage. The kill-on-contact microbiocidal activities of this resin were demonstrated using single-species biofilms of Streptococcus mutans (ATCC 36558), Actinomyces naeslundii (ATCC 12104) and Candida albicans (ATCC 90028). Improved mechanical properties after hydration provided the proof-of-concept that QAMS-incorporated resin exhibits self-repair potential via water-induced condensation of organic modified silicate (ormosil) phases within the polymerized resin matrix.

The effects of hyaluronic acid, calcium hydroxide, and dentin adhesive on rat odontoblasts and fibroblasts

The aim of this study was to investigate the effects and efficiency of pulp capping preparations based on hyaluronic acid, calcium hydroxide, and dentin adhesive on the pulp tissue of Sprague-Dawley rats. The rats were killed and extracted teeth sectioned transversely through the pulp. The slices were placed in a RPMI 1640 cell culture medium supplemented with 10 % foetal calf serum. During 14 days of cultivation cultures were treated with preparations that contained hyaluronic acid (Gengigel Prof®), and calcium hydroxide (ApexCal®), or with dentin adhesive (Excite®). Cellularity and viability of fibroblasts and odontoblasts was analysed using a haemocytometer. Hyaluronic acid proved most efficient and the least toxic for direct pulp capping. Even though calcium hydroxide and dentin adhesive demonstrated a higher degree of cytotoxicity, their effects were still acceptable in terms of biocompatibility.

Apoptosis and survivability of human dental pulp cells under exposure to Bis-GMA

Objective

In the present study, we examined whether 2, 2-bis [4-(2-hydroxy-3methacryloxypropoxy) phenyl] propane (Bis-GMA) has effects on LSC2 cells, human dental pulp cell line.

Material and Methods

The viability, cell cycle, and morphology of LSC2 cells were analyzed after exposure to several different concentrations of Bis-GMA. The recovery of viability of Bis-GMA exposed cells was also analyzed in the condition without Bis-GMA. Further, penetration of Bis-GMA to dentin disc was examined using isocratic high-performance liquid chromatography.

Results

There was a concentration-dependent decrease in cell proliferation and an increase in cell number in the sub-G1 population after exposure to Bis-GMA. Furthermore, the cells showed typical characteristics of apoptotic cells after the exposure to high concentration of Bis-GMA. In contrast, cells exposed to lower concentrations of Bis-GMA recovered their viability after being cultured without Bis-GMA. We also found that Bis-GMA is capable of penetrating 1-mm-thick dentin discs, though the penetrated concentration was lower than that showing cytotoxicity.

Conclusion

These results suggest that Bis-GMA has cytotoxic effects, though dental pulp exposed to lower concentrations is able to recover their viability when Bis-GMA is removed.

Effect of light sources on nanohardness, elastic modulus and water sorption of a composite resin

The aim of this study was to evaluate the effect of a light source on nanohardness, elastic modulus, water sorption and solubility of a composite resin. Four curing units were used, three of which had an LED and another had a halogen source. The resin composite Z250 (3M ESPE) was used for all tests. For water sorption and solubility, five resin disks were made (15 mm in diameter and 1 mm thick), and these were polymerized for 20 seconds at nine different points (1 in the center and 8 around). For nanohardness and elastic modulus evaluation, 20 cylinders (5 for each group) were made with a bipartite steel matrix (6.0 mm diameter and 4.0 mm thick). The results of this study showed that the group polymerized with the Radii light-curing unit presented less water sorption than other curing units (p < 0.05). No statistical difference between units was found in nanohardness in 1mm-thick specimens. However, decreased nanohardness was shown at higher resin composite depth (p < 0.05). A Pearson correlation showed a strong positive relationship between nanohardness and elastic modulus for all groups and depths. The light source affects the water sorption, nanohardness and elastic modulus of composite resins.

Activation of stress-regulated transcription factors by triethylene glycol dimethacrylate monomer

Triethylene glycol dimethacrylate (TEGDMA) is a resin monomer available for short exposure scenarios of oral tissues due to incomplete polymerization processes of dental composite materials. The generation of reactive oxygen species (ROS) in the presence of resin monomers is discussed as a common mechanism underlying cellular reactions as diverse as disturbed responses of the innate immune system, inhibition of dentin mineralization processes, genotoxicity and a delayed cell cycle. Yet, the signaling pathway through a network of proteins that finally initiates the execution of monomer-induced specific cell responses is unknown so far. The aim of the present study was to extend the knowledge of molecular mechanisms of monomer-induced cell death as a basis for reasonable therapy strategies. Thus, the monomer-induced expression and phosphorylation of stress-related transcription factors was analyzed in various cell lines. The time-related induction of apoptosis was investigated as well. The expression of p53 increased in HeLa cell cultures treated with camptothecin (positive control) for 24h, and the formation of p53Ser15 and p53Ser46 was detected in cell nuclei by Western blotting. TEGDMA (3 mm) appeared to stimulate p53 expression only slightly, but increased p21 expression was found in cell nuclei and cytoplasm. Both camptothecin and TEGDMA increased p53 expression to some extent in the nuclear fraction in human transformed pulp-derived cells (tHPC), and similar effects were detected in RAW264.7 macrophages. No clear induction of c-Jun and phospho-c-Jun by TEGDMA was detected in HeLa cell nuclei, and the expression of ATF-2 and phospho-ATF-2 was inhibited in the presence of the monomer. ATF-3 expression was found only in the nuclear fraction of camptothecin-treated HeLa cultures. TEGDMA seemed to inhibit the formation of phospho-c-Jun and phospho-ATF-2 in tHPC, and the monomer acted negatively on the expression of c-Jun, ATF-2 and ATF-3 in RAW264.7 macrophages. These changes in the expression and activation of stress-related transcription factors were time-related to the induction of apoptosis by TEGDMA in all cell lines. The present study provides experimental evidence that TEGDMA interferes with the regulation of cellular pathways through transcription factors activated as a consequence of DNA damage like p53 or initiated downstream of MAPK (mitogen-activated protein kinases) like c-Jun, ATF-2 and ATF-3. The direct causal correlation between DNA damage, activation or inhibition of MAPKs and transcription factors, and apoptosis is under current investigation. However, the induction of apoptosis in different cell lines in the presence of monomers like TEGDMA may be subject to a higher level of complexity than currently suggested by simple linear models.

The effect of dentine-bonding agents on substance P release in human dental pulp

AIM

To quantify the effect of dentine-bonding agents on Substance P (SP) release in healthy human dental pulp tissue.

METHODOLOGY

Forty pulp samples were obtained from healthy pre-molars where extraction was indicated for orthodontic reasons. In thirty of these pre-molars, a standardized Class V cavity preparation was performed, and teeth were divided equally into three groups: (i) Unetched-cavity control group: Class V cavities only; (ii) Experimental Group I: 'One-step' self-etch bonding agent was placed in the cavity; and (iii) Experimental Group II: 'Two-step' total-etch bonding agent was placed in the cavity. The remaining ten healthy pre-molars where extracted without treatment and served as an intact-teeth control group. SP was measured by radioimmunoassay.

RESULTS

Greater SP release was found in the 'one-step' bonding agent group, followed by the 'two-step' bonding agent group and the unetched-cavity control group. The lower SP values were for the intact-teeth control group. anova showed statistically significant differences between groups (P = 0.0001). Tukey HSD post hoc tests showed statistically significant differences in SP release between the intact-teeth control group and the three other groups (P < 0.01) and between the unetched-cavity control group and the 'one-step' bonding agent group (P < 0.05). No significant difference was found between the 'two-step' bonding agent and the unetched-cavity control group.

CONCLUSION

Dentine-bonding agents placed over Class V cavity preparations increased SP release. One-step dentine-bonding agents increased SP release most.

Cytotoxicity and biocompatibility of direct and indirect pulp capping materials

There are several studies about the cytotoxic effects of dental materials in contact with the pulp tissue, such as calcium hydroxide (CH), adhesive systems, resin composite and glass ionomer cements. The aim of this review article was to summarize and discuss the cytotoxicity and biocompatibility of materials used for protection of the dentin-pulp complex, some components of resin composites and adhesive systems when placed in direct or indirect contact with the pulp tissue. A large number of dental materials present cytotoxic effects when applied close or directly to the pulp, and the only material that seems to stimulate early pulp repair and dentin hard tissue barrier formation is CH.

The induction of cytotoxicity, oxidative stress, and genotoxicity by root canal sealers in mammalian cells

OBJECTIVE

Toxicologic aspects of the root canal sealers Acroseal, Epiphany, AH Plus, and castor oil polymer (COP) were analyzed using cell culture techniques.

STUDY DESIGN

Set materials were extracted in culture medium, and cytotoxicity and the generation of reactive oxygen species (ROS) were determined in human pulp cells. The formation of micronuclei (MN), indicative of genotoxicity and changes of the cell cycle, were analyzed in V79 cells.

RESULTS

The ranking of the most to the least toxic material was: Acroseal > Epiphany = AH Plus >> COP. The production of ROS was increased by Epiphany, Acroseal, and AH Plus about 4-7-fold, but enhanced ROS production was not detected with COP. Acroseal, Epiphany, and AH Plus increased the numbers of MN, and Acroseal delayed the cell cycle in G2 phase.

CONCLUSION

The materials which tested cytotoxic in the present study may be able to alter oral tissue-specific functions and cause inflammation.

Can interaction of materials with the dentin-pulp complex contribute to dentin regeneration?

Understanding outcomes of the interaction between a dental material and tooth tissue is important in terms not only of biocompatibility but also of the potential for the material to modulate the response of the tissue. This interaction is influenced by many factors, including the chemistry of the material and any of its eluted components or degradation products, and the manner in which the tissue responds to these agents. Past studies of this interaction have primarily been aimed at identifying cytotoxic effects. More recently, investigations have focused on specific cellular responses, and in particular, on understanding how the materials themselves actually may contribute to regenerative processes in the tooth. Recent work has demonstrated the solubilization of proteins from dentin exposed to certain materials, such as calcium hydroxide, mineral trioxide aggregate, and acidic solutions that relate to those used in dentin bonding agents, with the subsequent modulation by these proteins of gene expression in odontoblast-like cells. This work suggests that dentin bridge formation under such materials may be stimulated through this process. Thus, there is much merit in examining both how new dental materials can be developed and how more traditional ones can be modified to preferentially stimulate regenerative processes when preferred. This review summarizes current knowledge about the potential beneficial effects derived from the interaction of dental materials with the dentin-pulp complex, as well as potential future developments in this exciting field.

Vasorelaxant effects of Clearfil SE Bond and Clearfil S(3) Bond mediated by calcium antagonistic action

Dental adhesives can alter the contractility of vascular tissue via different mechanisms. The aim of this study was to investigate and compare the vascular action of two self-etch adhesive systems, Clearfil SE Bond (CSEB) and Clearfil S(3) Bond (CS3B). Responses of isolated rat thoracic aorta rings were recorded isometrically by force displacement transducers. Following pre-contraction of aorta rings, relaxations to the independent and mixed components of CSEB and CS3B were recorded in the absence and presence of nitric oxide synthase (NOS) inhibitor (N(omega)-nitro-L-arginine methyl ester (N-LAME)), cyclooxygenase (COX) inhibitor (indomethacin) and K+ channel inhibitors (tetraethylammonium, glibenclamide and 4-aminopyridine). We also tested the effects of CSEB and CS3B in endothelium-intact and -denuded rat thoracic aorta rings. To investigate the Ca2+-channel antagonistic effect of adhesive components, concentration-response curves to CaCl2 were obtained in the absence and presence of the components. The primer, the bond, and the mixture of CSEB and CS3B elicited concentration-dependent relaxations. Mechanical rubbing of the endothelium did not significantly modify the extent of vasorelaxation induced by the test materials. The vasorelaxant effect was mediated neither by NOS and COX inhibition nor by the tested K+ channel antagonists. Mechanical removal of the endothelium did not alter the vasodilatory effect induced by the self-etch adhesives. Both CSEB and CS3B significantly inhibited the contractions induced by CaCl2. These results demonstrate the vasodilatory effect induced by the self-etch adhesive systems through a Ca2+-antagonistic effect.

The effects of one-step self-etch adhesives on the induction of oxidative stress and production of TGF-beta1 and BMP-2 by human gingival fibroblasts

The aim of this study was to evaluate and compare the effects of two self-etch adhesive materials on the induction of oxidative stress and production of transforming growth factor-beta1 (TGF-beta1) and bone morphogenetic protein-2 (BMP-2) by cultured human gingival fibroblasts (HGF). Inflammation-free attached gingiva was obtained from healthy donors under informed consent. Following 24- and 72-h exposure of HGF to two different elutes of the test materials, cell viability was determined using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Lipid peroxidation, a major indicator of oxidative stress, was measured by the thiobarbituric acid reactive substance (TBARS) assay. TGF-beta1 and BMP-2 levels in cell-free culture media were determined by enzyme-linked immunosorbent assay (ELISA). Cell viability of the test groups was significantly lower than those of control at 24 and 72 h (P < 0.001), but showed an increase at 72 h (P < 0.001). The TBARS levels of both test groups were significantly greater than that of control (P < 0.05), and displayed similar values at 72 h (P > 0.05). For both materials, the levels of TGF-beta1 and BMP-2 were significantly greater than that of control (P < 0.05). Both test groups showed increased TGF-beta1 levels. These results indicate that the tested self-etch adhesives might be capable of inducing production of TGF-beta1 and BMP-2 in cultured HGF, despite their cytotoxic and oxidative stress-producing potential.

Biocompatibility of Resin-based Dental Materials

Oral and mucosal adverse reactions to resin-based dental materials have been reported. Numerous studies have examined the biocompatibility of restorative dental materials and their components, and a wide range of test systems for the evaluation of the biological effects of these materials have been developed. This article reviews the biological aspects of resin-based dental materials and discusses the conventional as well as the new techniques used for biocompatibility assessment of dental materials.

Cytotoxicity of one-step dentin-bonding agents toward dental pulp and odontoblast-like cells

The purpose of this study was to compare the cytotoxicity of five one-step dentin-bonding agents on human dental pulp and odontoblast-like cells (MDPC-23). Photopolymerized and unpolymerized samples of these dentin-bonding agents were prepared and incubated with dental pulp or MDPC-23 cells. After 24 or 72 h of incubation, the number of unstained cells with trypan blue was counted. The staining of cells with trypan blue stands for a cytotoxicity. The pulp cell and MDPC-23 cytotoxicity of polymerized sample treatment increased in the order of AQ Bond Plus (AQ)<Clearfil Tri-S Bond (TS)=G-bond (GB)<Absolute (AB)<Adper Prompt (AP) for 24 and 72 h. The pulp cell cytotoxicity of unpolymerized sample treatment for 24 h increased in the order of AQ<GB = AB<TS<AP. The MDPC-23 cytotoxicity of unpolymerized sample treatment for 24 h increased in the order of AQ<GB<TS = AB<AP. Whether polymerized or unpolymerized, AQ was the least cytotoxic agent, while AP was the strongest. All polymerized dentin-bonding agents exhibited lower cytotoxicity by 2-65% than their unpolymerized counterparts. The appearance of the cytotoxicity of dentin-bonding agents was time-dependent, and cell viability was lower at 72 h by 2-46% than at 24 h. The cytotoxicity to MDPC-23 cells was about 5-24% higher than that to pulp cells. These results indicate that one-step dentin-bonding agents differ markedly in their cytotoxicity. Differential cytotoxic effects of one-step dentin-bonding agents should be considered during clinical application of operative restoration.

Cytotoxic effects of hard-setting cements applied on the odontoblast cell line MDPC-23

OBJECTIVE

The present study evaluated the cytotoxic effects of hard setting applied on the odontoblastlike cells MDPC-23.

STUDY DESIGN

Eighty round-shaped samples were prepared with the following experimental materials: calcium hydroxide, Vitrebond, RelyX Luting, and RelyX Unicem. The samples were placed in serum-free culture medium and incubated for 24 hours or 7 days at 37 degrees C with 5% CO2 and 95% air. The odontoblast cells were plated in the wells and incubated for 72 hours. After this period, the complete culture medium was replaced by the extracts obtained from every sample, and the methyltetrazolium assay was carried out to evaluate the cell metabolism.

RESULTS

For the 24-hour period, the experimental materials calcium hydroxide, Vitrebond, RelyX Luting, and RelyX Unicem decreased the cell metabolic activity by 91.52%, 81.14%, 78.17%, and 2.64%, respectively. For the 7-day period, calcium hydroxide, Vitrebond, RelyX Luting, and RelyX Unicem decreased the metabolic activity of the MDPC-23 cells by 91.13%, 87.27%, 79.04%, and 10.51%, respectively.

CONCLUSION

RelyX Unicem presented the lowest cytopathic effects to the cultured odontoblast cell line.