Overexpression of interleukin-6 and -8, cell growth inhibition and morphological changes in 2-hydroxyethyl methacrylate-treated human dental pulp mesenchymal stem cells

Cytotoxicity and microbiological behavior of universal resin composite cements

OBJECTIVES

To investigate the cytotoxicity on human dental pulp cells (HDPCs) and Streptococcus mutans (S.mutans) biofilm formation on universal resin composite cements (UCs).

METHODS

Three UCs (RelyX Universal, 3 M Oral Care - RXU; Panavia SA Cement Universal, Kuraray Noritake - PSAU; SoloCem, Coltene - SCM) and one 'gold-standard' multi-step cement (Panavia V5, Kuraray Noritake - PV5) were used following two polymerization protocols (light-cured - LC; self-cured - SC). Cytotoxicity (MTT) tests were performed after 1, 3 and 7 days of direct contact. Carboxy-2',7'-dichlorodihydrofluorescein diacetate was used to detect the release of reactive oxygen species (ROS), and interleukin 6 (IL-6) expression was analyzed by IL-6 proquantum high sensitivity immunoassay. S. mutans biofilms were grown on UCs samples in a bioreactor for 24 h, then adherent viable biomass was assessed using MTT assay. For microbiological procedures, half of UCs samples underwent accelerated aging. Data were statistically analyzed (α = 0.05).

RESULTS

The highest cytotoxicity was observed for PSAU SC, RXU SC, and PV5 SC at day 1, then for SC RXU after 3 days, and SC PSAU, LC PV5 and SCM after 1-week (p < 0.05). There was no increase in IL-6 expression after 1 day, while it increased depending on the group at 3 and 7 days. The highest ROS expression after 12 h was recorded for PSAU SC, PV5 SC and PV5 LC. Biofilm formation was as follows: RXU > > PSAU = PV5 > SCM, while light-curing systematically decreased biofilm formation (≈-33 %). Aging leveled out differences between UCs and between polymerization protocols.

SIGNIFICANCE

The choice of cement brand, rather than category, and polymerization protocol influence cell viability and microbiological behavior. Light-curing is beneficial for reducing the harmful pulpal effect that UCs may possess.

In Vitro Evaluation of Candida albicans Adhesion on Heat-Cured Resin-Based Dental Composites

Microbial adhesion on dental restorative materials may jeopardize the restorative treatment long-term outcome. The goal of this in vitro study was to assess Candida albicans capability to adhere and form a biofilm on the surface of heat-cured dental composites having different formulations but subjected to identical surface treatments and polymerization protocols. Three commercially available composites were evaluated: GrandioSO (GR), Venus Diamond (VD) and Enamel Plus HRi Biofunction (BF). Cylindrical specimens were prepared for quantitative determination of C. albicans S5 planktonic CFU count, sessile cells CFU count and biomass optical density (OD570 nm). Qualitative Concanavalin-A assays (for extracellular polymeric substances of a biofilm matrix) and Scanning Electron Microscope (SEM) analyses (for the morphology of sessile colonies) were also performed. Focusing on planktonic CFU count, a slight but not significant reduction was observed with VD as compared to GR. Regarding sessile cells CFU count and biomass OD570 nm, a significant increase was observed for VD compared to GR and BF. Concanavalin-A assays and SEM analyses confirmed the quantitative results. Different formulations of commercially available resin composites may differently interact with C. albicans. The present results showed a relatively more pronounced antiadhesive effect for BF and GR, with a reduction in sessile cells CFU count and biomass quantification.

Cytotoxicity of 3D printed resin materials for temporary restorations on human periodontal ligament (PDL-hTERT) cells

OBJECTIVES

Various dental resin materials are available for the fabrication of temporary restorations using modern additive printing methods. Albeit these materials are placed for several months in intimate contact with dental hard and soft tissues, including the gingival crevice, there exists only insufficient evidence on the biocompatibility of these materials. This in vitro study aimed to delineate the biocompatibility of 3D printable materials on periodontal ligament cells (PDL-hTERTs).

METHODS

Samples of four dental resin materials for additive fabrication of temporary restorations using 3D printing (MFH, Nextdent; GC Temp, GC; Freeprint temp, Detax; 3Delta temp, Deltamed), one material for subtractive fabrication (Grandio disc, Voco) and one conventional temporary material (Luxatemp, DMG) were prepared with a standardized size according to the manufacturer's instructions. Human PDL-hTERTs were exposed to resin specimens or eluates of the material for 1, 2, 3, 6 and 9 days. For determination of cell viability, XTT assays were performed. In addition, the expression of the proinflammatory cytokines interleukin 6 and 8 (IL-6 and 8) was assessed in the supernatants with ELISA. Cell viability and the expression of IL-6 and 8 in presence of the resin material or their eluates was compared with untreated controls. Immunofluorescence staining for IL-6 and IL-8, as well as scanning electron microscopy of the discs after culturing, were performed. Differences between groups were analyzed with Student´s t-test for unpaired samples.

RESULTS

Compared to untreated control samples, the exposure against the resin specimen induced strong reduction of cell viability in case of the conventional material Luxatemp (p < 0.001) and the additive material 3Delta temp (p < 0.001) irrespective of the observation period. On the contrary, the presence of eluates of the various materials induced only minor changes in cell viability. Considering IL-6 (day 2: p = 0.001; day 6 and 9: p < 0.001) and IL-8 (day 1: p = 0.001; day 2, 3, 6, 9: p < 0.001) their expression was strongly reduced in presence of the eluate of Luxatemp. Except for IL-6 at day 1 and 6 also the material 3Delta temp caused significant reduction of both proinflammatory mediators at any time point.

SIGNIFICANCE

The conventional material Luxatemp and the additive material 3Delta temp appear to severely affect cell viability when in direct contact with PDL-hTERTs. The other tested materials of this new category of additive materials and the subtractive material Grandio seem to induce only minor changes in direct contact with these cells. Therefore, they could serve as a viable alternative in the fabrication of temporary restorations.

Wear Properties of Conventional and High-Translucent Zirconia-Based Materials

This study investigated the two-body wear resistance of a first generation 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), a second generation 3Y-TZP, a third generation 4 mol% yttria partially stabilized zirconia (4Y-PSZ), a 5 mol% yttria partially stabilized zirconia (5Y-PSZ), and a type III gold alloy (Aurocast 8), performed using opposing antagonistic cusps made out of the same material. Eight cylindrical specimens were prepared for each material (n = 8) for a total of forty specimens (N = 40). Conical cusps were fabricated for each material. Each cylinder−cusp pair was arranged inside a two-axis chewing simulator over up to 360,000 loading cycles. The wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm3). The antagonist wear (mm) was recorded before and after the wear test to evaluate the linear difference. Statistical analysis was performed using one-way analysis of variance (ANOVA); multiple comparisons were performed according to Tukey’s method. No statistically significant differences (p > 0.05) among the first generation 3Y-TZP, second generation 3Y-TZP, and 4Y-PSZ wear were found. 5Y-PSZ showed statistically significant higher wear compared to other the zirconias. Aurocast 8 displayed the highest values in terms of vertical wear, antagonist cusp wear, and volumetric loss. Although still not statistically comparable, the wear behavior of the latest 5Y-PSZ was the closest to the widely recognized gold standard represented by the type III gold alloy.

Effects of resin materials dedicated for additive manufacturing of temporary dental restorations on human gingival keratinocytes

OBJECTIVE

This study investigated the effect of eluates of conventional and 3D-printed resin materials for manufacturing temporary dental restorations on gingival keratinocytes.

METHODS

Three-dimensional (3D)-printed resin materials: 3Delta temp (Deltamed), NextDent MFH (Nextdent), Freeprint temp (Detax), GC temp (GC), were compared to Grandio disc (Voco) and Luxatemp (DMG). Human gingival keratinocytes (IHGKs) were exposed to eluates of the materials and XTT assays were performed at 24 h, 48 h, 72 h, or 144 h. For quantification of the proinflammatory response, the protein amount of IL-6 and 8 was determined in the supernatants using ELISA. One-way ANOVA with post hoc analysis was used to compare differences in cell viability and IL-6 and IL-8 levels between groups.

RESULTS

At 24 h, and more remarkably at 48 h, a significant decrease in cell viability occurred for the 3D-printed materials compared to the untreated IHGKs, but also compared to Grandio disc and Luxatemp. Except for the expression of IL-8 in presence of the eluate of Grandio disc at 24 and 48 h, all tested materials caused attenuation of IL-6 and 8 from IHGKs for any observation period.

CONCLUSIONS

The materials for additive manufacturing affect cell proliferation differently than the subtractive manufactured material Grandio disc and the conventional material Luxatemp.

CLINICAL SIGNIFICANCE

In comparison to conventional and subtractive manufactured restorations, 3D printed temporary restorations might induce more negative effects on the gingival and probably also on pulpal health since viability and the proinflammatory response of oral keratinocytes are more intensively affected by these materials.

Expression of immunomodulatory and tissue regenerative biomarkers in human dental pulp derived-mesenchymal stem cells treated with curcumin: an in vitro study

BACKGROUND

Human Dental pulp derived-mesenchymal stem cells (hDP-MSCs) have the capability of selfrenewal, multipotency, as well as immunosuppressive properties. They are ideal candidates for regenerating damaged dental tissue and treating inflammation-related diseases. However, methods (such as genetic variation) to improve the immunomodulatory and regenerative efficiency of MSCs in different diseases still need to be developed. Curcumin (CUR) is known for its broad applications in regenerative medicine and the treatment of inflammatory disorders via its anti-inflammatory and anti-oxidant effects. This study was conducted to investigate the effect and underlying mechanisms of CUR on the immunomodulatory and regenerative function of hDP-MSCs and whether treating these cells with CUR can improve therapeutic efficacy.

METHODS AND RESULTS

hDP-MSCs were isolated from dental pulp and then treated with CUR. Cell viability rate was observed in hDP-MSCs after treatment of CUR by MTT assay. Real-time quantitative (RT-PCR) was applied to estimate the expression of immunomodulatory and regenerative genes after treatment of CUR. The RT-PCR results showed that VEGF-A and STAT3 markers were up-regulated while HLA-G5 and VCAM-1 markers were down-regulated by CUR (20 µM) treatment in hDP-MSCs (P < 0.001). Besides, this research indicated that there were no significant changes in the expressions of RelA and DSPP after 48 h (P = 0.33, P = 1).

CONCLUSION

Our findings demonstrate that CUR can enhance the immunomodulatory and regenerative effects of hDP-MSCs and improve their therapeutic efficacy. These findings can give an understanding of the mechanism for improving restorative and immunomodulatory activity in hDP-MSCs by curcumin.

Antibacterial and Antibiofilm Properties of Three Resin-Based Dental Composites against Streptococcus mutans

Antibacterial and antibiofilm properties of restorative dental materials may improve restorative treatment outcomes. The aim of this in vitro study was to evaluate Streptococcus mutans capability to adhere and form biofilm on the surface of three commercially available composite resins (CRs) with different chemical compositions: GrandioSO (VOCO), Venus Diamond (VD), and Clearfil Majesty (ES-2). Disk-shaped specimens were manufactured by light-curing the CRs through two glass slides to maintain a perfectly standardized surface topography. Specimens were subjected to Planktonic OD_600nm, Planktonic CFU count, Planktonic MTT, Planktonic live/dead, Adherent Bacteria CFU count, Biomass Quantification OD_570nm, Adherent Bacteria MTT, Concanavalin A, and Scanning Electron Microscope analysis. In presence of VOCO, VD, and ES2, both Planktonic CFU count and Planktonic OD_600nm were significantly reduced compared to that of control. The amount of Adherent CFUs, biofilm Biomass, metabolic activity, and extracellular polymeric substances were significantly reduced in VOCO, compared to those of ES2 and VD. Results demonstrated that in presence of the same surface properties, chemical composition might significantly influence the in vitro bacterial adhesion/proliferation on resin composites. Additional studies seem necessary to confirm the present results.

Influence of 2-hydroxyethyl methacrylate (HEMA) exposure on angiogenic differentiation of dental pulp stem cells (DPSCs)

OBJECTIVE

The angiogenic differentiation of dental pulp stem cells (DPSCs) is important for tissue homeostasis and wound healing. In this study the influence of 2-hydroxyethyl methacrylate (HEMA) on angiogenic differentiation was investigated.

METHODS

To evaluate HEMA effects on angiogenic differentiation, DPSCs were cultivated in angiogenic differentiation medium (ADM) in the presence or absence of non-toxic HEMA concentrations (0.1 mM and 0.5 mM). Subsequently, angiogenic differentiation was analyzed on the molecular level by qRT-PCR and protein profiler analyzes of angiogenic markers and flow cytometry of PECAM1. The influence of HEMA on angiogenic phenotypes was analyzed by cell migration and sprouting assays.

RESULTS

Treatment with 0.5 mM HEMA during differentiation can lead to a slight reduction of angiogenic markers on mRNA level. HEMA also seems to slightly reduce the quantity of angiogenic cytokines (not significant). However, these HEMA concentrations have no detectable influence on cell migration, the abundance of PECAM1 and the formation of capillaries. Higher concentrations caused primary cytotoxic effects in angiogenic differentiation experiments conducted for longer periods than 72 h.

SIGNIFICANCE

Non-cytotoxic HEMA concentrations seem to have a minor impact on the expression of angiogenic markers, essentially on the mRNA level, without affecting the angiogenic differentiation process itself on a detectable level.

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.

Wear Properties of Different Additive Restorative Materials Used for Onlay/Overlay Posterior Restorations

The purpose of this laboratory study was to compare the two-body wear resistance of different restorative materials commonly used for the indirect restoration of posterior teeth. The tested materials, based on ceramic (Imagine Press X, IPS e.max CAD, Milled Celtra Duo, Glaze-Fired Celtra Duo, Vita Mark II) and composite (Enamel Plus HRi, Enamel Plus HRi Bio-Function, Filtek Supreme XTE, Lava Ultimate), were compared with the wear properties of a type III gold alloy (Aurocast 8). Flat samples were prepared with a 6-mm thickness (n=10). Composite samples were tested after a heat polymerization cycle. All samples were exposed to a two-body wear test in a dual axis chewing simulator performing over 120,000 loading cycles. The opposing abrader cusps were fabricated from yttria-stabilized tetragonal zirconia polycrystal. The vertical substance loss (mm) and the volume loss (mm3) were recorded, as was the wear of the antagonist cusp (mm). Mean values were analyzed by one-way analysis of variance. Significant differences among materials were detected. The heat-cured resin-based composite material Enamel Plus Bio-Function and the type III gold alloy demonstrated similar mean values for wear depth and volumetric loss.

Curcumin/Liposome Nanotechnology as Delivery Platform for Anti-inflammatory Activities via NFkB/ERK/pERK Pathway in Human Dental Pulp Treated With 2-HydroxyEthyl MethAcrylate (HEMA)

Curcumin, primary component of the spice turmeric extracted from the rhizomes of Curcuma longa, represents the major anti-oxidant and anti-inflammatory substance found in turmeric, acting thought various mechanisms not completely understood. Curcumin modulates cytokines, growth factors, transcription factors, inflammatory molecules and cell signaling pathways. During restorative dentistry practice, free resin monomers of 2-hydroxyethyl methacrylate (HEMA) propagate through dentin micro-channel and pulp into the bloodstream affecting cellular integrity. The study highlights the significance of application of curcumin bioactive component into liposomal formulations (CurLIP) to restore the homeostasis of dental pulp stem cells (hDPSCs) in response to 3 and 5 mmol L^–1 HEMA treatment. Cell proliferation in combination with changes of the morphological features, proinflammatory cytokines secretion as Interleukin (IL) 6, IL8, Monocyte Chemoattractant Protein-1 (MCP1) and Interferon-gamma (IFNγ) were assayed along with the nuclear factor (NF)-kB, an inducible transcription factor involved in the activation of several cell processes associated to extracellular signal-regulated kinases (ERK) and posphorylated (p-) ERK pathway. Our results showed a decreased cell proliferation, morphological changes and upregulation of IL6, IL8, MCP1 and IFNγ in presence of 3 and 5 mmol L^–1 HEMA treatment. CurLIP therapy in hDPSCs provokes an increase in cell proliferation and the block of inflammatory cytokines secretion through the inhibitory regulation of NFkB/ERK and pERK signaling cascade. The natural nanocarrier CurLIP influences numerous biochemical and molecular cascades causing anti-inflammatory properties in response to HEMA treatment in human dental pulp stem cells, representing an innovative endodontic formulation able to improve the quality of dental care with a major human community impact.

Effects of the methacrylate/acrylate monomers HEMA, TEGDMA, DEGDA, and EMA on the immune system

Incomplete curing of dental fillings may lead to leakage of methacrylate/acrylate monomers, which may come in contact with different cells of the immune system in oral tissues. Very little is known about the different immunologic effects caused by these methacrylates/acrylates. The objective of the present study was to study if and how the methacrylate/acrylate monomers ethyl methacrylate (EMA) and diethylene glycol diacrylate (DEGDA) affect the immune system in vivo and in vitro in comparison to 2-hydroxyethyl methacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA). Human peripheral blood mononuclear cells were exposed to the different monomers (500 and 1000 μM) for 24 hr in vitro. BioPlex Pro™ assays were used for cytokine analysis. In vivo, BALB/c mice were immunized subcutaneously at the base of the tail with HEMA, TEGDMA, EMA, or DEGDA in combination with ovalbumin (OVA) in order to study adjuvant properties of the 4 monomers. Peripheral blood mononuclear cells exposed to DEGDA had viability less than 50% of the cells. A pattern was observed where the levels of most cytokines were elevated after exposure to HEMA or TEGDMA. Since that, many cells died after DEGDA-exposure, the only observed cytokine secretion was a significantly increased production of interleukin-18. In the in vivo experiments, all mice immunized with DEGDA died after the booster injection. Mice receiving OVA in combination with HEMA, TEGDMA, or EMA developed a higher immunoglobulin G anti-OVA antibody levels compared to the group immunized with OVA alone. We could not demonstrate any significant difference in antibody levels among the mice receiving the various methacrylate/acrylate monomers. The different monomers affected the production, increase and decrease, of different cytokines in vitro but resulted also in vivo in increased antibody production and T-cell activity.

Antibacterial Activity of Commercial Dentine Bonding Systems against E. faecalis-Flow Cytometry Study

Literature presents inconsistent results on the antibacterial activity of dentine bonding systems (DBS). Antibacterial activity of adhesive systems depends on several factors, including composition and acidity. Flow cytometry is a novel detection method to measure multiple characteristics of a single cell: total cell number, structural (size, shape), and functional parameters (viability, cell cycle). The LIVE/DEAD^® BacLight™ bacterial viability assay was used to evaluate an antibacterial activity of DBS by assessing physical membrane disruption of bacteria mediated by DBS. Ten commercial DBSs: four total-etching (TE), four self-etching (SE) and two selective enamel etching (SEE) were tested. Both total-etching DBS ExciTE F and OptiBond Solo Plus showed comparatively low antibacterial activity against E. faecalis. The lowest activity of all tested TE systems showed Te-Econom Bond. Among SE DBS, G-ænial Bond (92.24% dead cells) followed by Clearfil S3 Bond Plus (88.02%) and Panavia F 2.0 ED Primer II (86.67%) showed the highest antibacterial activity against E. faecalis, which was comparable to isopropranol (positive control). In the present study, self-etching DBS exhibited higher antimicrobial activity than tested total-etching adhesives against E. faecalis.

NF-kB mediated down-regulation of collagen synthesis upon HEMA (2-hydroxyethyl methacrylate) treatment of primary human gingival fibroblast/Streptococcus mutans co-cultured cells

PURPOSE

In vitro studies have evidenced the cytotoxic effect of HEMA (2-hydroxyethyl methacrylate), the most common component of dental resin-based restorative material, which is released within the oral cavity, on eukaryotic cells such as gingival fibroblast and epithelial cells. However, since the presence of microorganisms within the oral cavity cannot be excluded and little is known about the interactions occurring between eukaryotic cells and the human oral microbiota, our attention has been addressed to investigate the effect of 3 mM HEMA on the molecular mechanisms driving the response of human gingival fibroblasts (HGFs) co-cultured with Streptococcus mutans.

METHODOLOGY

HGF/S. mutans co-culture has been set up in our lab, and upon HEMA treatment, S.mutans and HGF cells' viability and adhesion along with type I collagen gene and pro-collagen I, Bax, Bcl2, nuclear factor kB (NF-kB), IkBα, pIkBα protein expression by PCR, Western blotting and ELISA assays have been investigated.

RESULTS

HEMA treatment determines a significant decrease of type I collagen protein production, even in the presence of S. mutans, in parallel to a decrease of cell viability and adhesion, which seem to be regulated by NF-kB activation. In fact, when SN50, NF-kB-specific pharmacological inhibitor, is added to the culture, cell proliferation along with collagen synthesis is restored.

CONCLUSION

The modulation exerted by S. mutans on the cytotoxic effect of HEMA suggests that within the oral cavity, the eukaryotic/prokaryotic cell interactions, maintaining the balance of the environment, allow HEMA to perform its adhesive and bonding function and that the use of a co-culture system, which simulates the oral cavity organization, improves the knowledge concerning the biocompatibility of this dental material.

Expression of P2X7 ATP receptor mediating the IL8 and CCL20 release in human periodontal ligament stem cells

ATP is released by human periodontal ligament cells (hPDLCs) and has been shown to regulate PDL regeneration and responses to mechanical stress through activation of P2Y receptors. This nucleotide, however, has also been reported to trigger the pro-inflammatory cascade by inducing the maturation and/or release of chemokines/cytokines from various cell types mainly via P2X7 receptors. Much less is known on the possible role of ATP in stem cells deriving from PDL (hPDLSCs) which are considered to be a promising tool for cell-based therapy to restore lesions. Given the role played by P2X7 in pathophysiological conditions, in this study we investigated the expression of P2X7 ATP receptors in hPDLSCs. The results obtained showed that hPDLSCs express P2X7 receptors evaluated by means of cytofluorimetric, immunohistochemistry, reverse transcriptase-PCR, and Western blot analyses. P2X7 ligation by 2',3'-(benzoyl-4-benzoyl)-ATP (BzATP), a specific receptor agonist, was followed by an increase in intracellular Ca2+ and in the uptake of ethidium bromide. These effects were dramatically reduced by oxidized ATP (oATP), the P2X7 irreversible inhibitor, suggesting that the P2X7 is the functional receptor involved. At 24 h treatment of hPDLSCs with BzATP it enhanced the release of the pro-inflammatory agents IL8 and CCL20, without influencing cell viability. These effects were counteracted by pre-treating the cells with oATP or with A-740003, a selective and potent P2X7 competitive antagonist. Collectively, these results indicated that extracellular ATP mediate a pro-inflammatory response via P2X7 receptors in hPDLSCs opening a further approach to control hPDLSCs behavior in their possible application as therapeutic tool.

Pro-inflammatory cytokine release and cell growth inhibition in primary human oral cells after exposure to endodontic sealer

AIM

To assay the toxicity of the single-methacrylate-based sealer urethane dimethacrylate (UDMA) (EndoRez) in terms of cell growth and pro-inflammatory cytokines release, in expanded ex vivo human dental pulp stem cells (hDPSCs), human periodontal ligament stem cells (hPDLSCs), human gingival fibroblasts (hGFs) and human osteoblasts (hOSTs).

METHODOLOGY

Dental pulp and periodontal ligament stem cells, osteoblasts and fibroblasts were derived from five young donors. After in vitro isolation, hDPSCs, hPDLSCs, hGFs and hOSTs were seeded to resin-based sealers for 24, 48, 72 h up to 1 week. The morphological features and the cell growth and the release of pro-inflammatory interleukin (IL)6, IL8, IL12 and tumour necrosis factor (TNF) α were analysed. Differences in cell growth and in interleukin secretion were analysed for statistical significance with two-way anova tests for multiple comparisons.

RESULTS

Exposure to endodontic sealer based on UDMA resulted in a 50% decrease in survival oral cells at 24 h of incubation. No evident morphological changes were present in cell cultures examined. After 48 h, 72 h and 1-week culture time, a progressive cell growth was evident. A significant up-regulation of IL6, IL8, IL12 and TNFα cytokines in cells in contact with the dental sealer compared to the control was observed.

CONCLUSION

In vitro, EndoRez interacted with primary human hDPSCs, hPDLSCs, hGFs and hOSTs causing damage to biological system evidenced through cell growth inhibition and up-regulation of IL6, IL8, IL12 and TNFα proinflammatory mediators.

Morphological Analysis and Interleukin Release in Human Gingival Fibroblasts Seeded on Different Denture Base Acrylic Resins

The development of different types of materials with application in practice dentistry is an area of intense growth and research due to its importance in oral health. Among the diverse materials currently used in restoration or in dentures, the acrylic based resins have been widely employed. The release of toxic components and the changes on their physical and mechanical properties actually represent a goal of intensive research. In vivo analysis showed that the surface roughness of the acrylic resin represents a factor that could stimulate bacteria colonization and soft tissue inflammation. For this purpose, in this work, we have analyzed the cell response to acrylic based resins Ivoclar, Tokuso and Coldpack in basal conditions, unpolished, and after the polished procedure performed to reduce the surface roughness. Our in vitro results using human gingival fibroblasts (HGFs) showed a decrease of cell growth, evaluated by MTT assay starting at 24 h of incubation, in samples seeded on resins in basal conditions and after the polished procedure. This cell growth reduction was associated to evident morphological changes in unpolished materials. After 24 h of culture in presence of polished and unpolished resins a spontaneous release was present of pro-inflammatory cytokines such as Interleukin-6 (IL-6) and −8 (IL-8), which was higher in unpolished resins, indicating that the polished procedure, minimizing the cytotoxicity process, could contribute to reduce the gingival inflammation processes.

Toll-like Receptor 4 Expression, Interleukin-6, -8 and Ccl-20 Release, and NF-KB Translocation in Human Periodontal Ligament Mesenchymal Stem Cells Stimulated with LPS-P. Gingivalis

Periodontal diseases, the major public health problem of the oral cavity, are clinically characterized by inflammation of the periodontal connective tissue that ultimately induces the destruction of periodontal tissue and the loss of alveolar bone. In chronic periodontitis, as well as aggressive periodontitis, the anaerobic gram-negative bacterium Porphyromonas gingivalis (P. gingivalis) is implicated. The pathogenicity of P. gingivalis is exerted by a wide variety of factors, including lipopolysaccharides (LPSs). LPSs activate the innate immune response during Gram-negative bacterial infections through the Toll-like receptor 4 (TLR-4)/myeloid differentiation protein 2 (MD-2) complex. In this study, the expression of TLR-4, the cell growth, the cytokine release, and the nuclear factor-KB (NF-kB) transcription factor expression in response to LPS- P.Gingivalis (LPS-G) were examined in Human Periodontal Ligament Mesenchymal Stem Cells (PDL-MSCs). The results obtained demonstrate that, in basal conditions, human PDL-MSCs express high levels of TLR-4. In inflammatory conditions mimicked by LPS-G challenge, the MTT assay carried out at different treatment times demonstrated the decrease of the cell growth. Moreover, the recognition of P. gingivalis components by TLR-4 culminated with the activation of secretion of inflammatory mediators such as: IL-6, IL-8 and CCL-20, and with the up-regulation of NF-kB, which was translocated into the nucleus. Our data intended to specify that TLR-4 expressed by PDL-MSCs is functional and plays a key role in inflammation.