In vitro induction of hydrolytic activity in human gingival and pulp fibroblasts by triethylene glycol dimethacrylate and monocyte chemotatic protein-1

TEGDMA (Triethylene Glycol Dimethacrylate) Induces Both Caspase-Dependent and Caspase-Independent Apoptotic Pathways in Pulp Cells

Monomers leached from resin-based composites (RBCs) may reach intrapulpal concentrations of the millimolar (mM) range, which could contribute to inflammation. The aim of this investigation was to assess the cytotoxicity of triethylene glycol dimethacrylate (TEGDMA) monomers on pulp cells as well as to identify molecular mechanisms leading to apoptosis. Pulp cells were harvested from molars extracted for orthodontic reasons and cultured through an explant method. To assess cytotoxicity, cells underwent a 5-day exposure to 0.75, 1.5, and 3 mM TEGDMA and were subject to cell counting and WST-1 staining. Based on the findings, cells were subsequently exposed to 0.1, 0.2, 0.75, 1.5, and 3 mM TEGDMA for 24 h to uncover the details of apoptosis. Changes in the production or cleavage of the apoptosis-specific proteins caspase-8, caspase-9, caspase-3, caspase-12, and Apoptosis-Inducing Factor (AIF) were measured by Western blot. The 5-day study showed concentration- and time-dependent cytotoxicity. Significant cell death was detected after 24 h with TEGDMA concentrations of 1.5 and 3 mM. One-day exposure to TEGDMA led to the activation of caspase-8, -9, -3, and -12 and an increased AIF production. Results suggest that relevant concentrations of TEGDMA monomers, leached from RBCs, induce apoptosis in pulp cells through both caspase-dependent as well as caspase-independent mechanisms. Endoplasmic reticulum stress and the activation of caspase-independent apoptotic pathways may be further mechanisms by which monomers induce apoptosis in pulp cells.

The effects of the dental methacrylates TEGDMA, Bis-GMA, and UDMA on neutrophils in vitro

Objectives

The prevalent usage of methacrylates in modern dentistry demands good knowledge of their biological impacts. While there have been several studies demonstrating the effects of different methacrylic monomers on mononuclear white blood cells, very little is known about the effects caused by these monomers on neutrophilic granulocytes. The objective of this study was to add novel knowledge about how neutrophils are affected by exposure to triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and bisphenol A glycol dimethacrylate (Bis‐GMA) alone or in combinations.

Materials and Methods

Isolated neutrophils were cultured in the presence or absence of methacrylates. The IL‐8 release was measured using a DuoSet ELISA development kit. Apoptosis and necrosis were analyzed using flow cytometry. The formation of neutrophil extracellular traps (NETs) was investigated using Sytox green DNA staining combined with microscopically examination of released DNA and myeloperoxidase (MPO).

Results

The release of IL‐8 was significantly increased after exposure to TEGDMA, Bis‐GMA, UDMA, or TEGDMA in combination with Bis‐GMA or UDMA compared to the unstimulated controls. Exposure to TEGDMA, UDMA, and Bis‐GMA for 24 hr separately or in combination did not affect apoptosis or necrosis of the exposed neutrophils. NET structures were formed by neutrophils after exposure to the different combinations of the methacrylates.

Conclusion

The combination of TEGDMA and Bis‐GMA had a synergistic proinflammatory effect on neutrophils by increasing the release of IL‐8 and the formation of NET structures. The changes in the normal functions of neutrophils caused by methacrylate exposure may lead to altered inflammatory response and relate to previously reported adverse immune reactions caused by these substances.

Triethyleneglycol dimethacrylate addition improves the 3D-printability and construct properties of a GelMA-nHA composite system towards tissue engineering applications

In tissue engineering, there is a growing interest in the development of 3D printable bone tissue-inspired nanocomposites. However, most such nanocomposites have poor mechanical properties, owing to poor dispersion of the mineral phase (e.g. nano-hydroxyapatite, nHA) within the organic phase (e.g. methacrylated gelatin, GelMA) and low volume fractions of each phase. Triethyleneglycol dimethacrylate (TEGDMA) is commonly added to dental resin-based composites to improve the properties of the dental resin. Here, the effects of substituting a portion of the water phase in a GelMA-nHA composite with TEGDMA were evaluated. TEGDMA improved the dispersion of nHA within the highly-concentrated GelMA-based composite ink, as well as increased the ink's shear yield strength and reduced the critical energy for ink cure. As a result, the printability of the composite ink was greatly improved upon TEGDMA inclusion. Lastly, while the swelling of the cast composite in 37 °C water increased slightly, the mechanical properties (tensile strength, toughness, and stiffness) of the cast composite increased by at least an order of magnitude upon TEGDMA addition, and all composites demonstrated MSC cytocompatibility after 24 h. Overall, TEGDMA shows promise as an additive to tune properties of the GelMA-nHA system towards use in tissue engineering applications.

Toxicology of Pre-heated Composites Polymerized Directly and Through CAD/CAM Overlay

Objectives

The aim was to compare cytotoxicity/genotoxicity of pre-heated composites polymerized through CAD/CAM overlays on isolated human peripheral blood lymphocytes.

Material and Methods

A microhybrid (Z100, 3M ESPE) and nanofilled composite (Filtek Supreme Ultra, 3M ESPE) were heated in a heating unit (Calset, AdDent Inc.) at different temperatures: 37 ^oC, 54 ^oC, and 68 ^oC. A small amount of heated composite was placed in a cylindrical mold (6mm diameter; 0.65mm thick), covered with a Mylar sheet, pressed and light-cured directly and through 2 mm thick CAD/CAM ceramic-reinforced polymer (CRP)(LAVA Ultimate, 3M ESPE) or CAD/CAM lithium disilicate ceramic (LDC)(e.max, Ivoclar/Vivadent) overlay. After curing, the specimens were immediately placed in a prepared lymphocyte cell culture. Cytotoxicity was assessed using a dye exclusion method by simultaneous staining with ethidium bromide and acridine orange, aimed to determine percentages of viable, apoptotic and necrotic cells. Genotoxicity was studied using alkaline comet assay.

Results

For Z100, the highest percentage of viable cells is recorded at T1 (93.7%) after direct light curing, followed by light curing through CRP (92.3%) and through LDC (91.7%T1,T3). For Filtek Supreme Ultra, the highest percentage of viable cells is recorded while curing through CRP (91.0% T2), followed by LDC (90% T1,T3) and direct light curing (88.7%T2).

Conclusion

For both tested materials, preheating the procedure at T1 and T2 may be the procedure of choice. In terms of genotoxicity, preheating at T3 may not be suggested.

Triethylene glycol dimethacrylate: adjuvant properties and effect on cytokine production

Objective: Leakage of monomers from dental fillings due to incomplete curing is very common. The objective of the present study was to examine the cytokine profile in cells exposed to triethyleneglycol dimethacrylate (TEGDMA) and the adjuvant properties of TEGDMA.

Materials and methods: Human peripheral blood mononuclear cells were exposed to TEGDMA (500 and 1000 μM) for 24 h in vitro. Bio-Plex Pro™ assays were used for analysis and detection of cytokines. In vivo, BALB/c mice were immunized subcutaneously in the base of the tail with TEGDMA in combination with ovalbumin (OVA).

Results: The cytokine levels of IL-8, IL-18, GRO-α and MCP-1 were significantly increased for both concentrations. IL-1β, IL-6 and TNF-α was only significantly increased in cultures exposed to 500 μM TEGDMA. The concentration of TNF-α was significantly decreased in cultures exposed to 1000 μM TEGDMA. Animals immunized with OVA co-administrated with TEGDMA had a significantly higher IgE and IgG anti-OVA antibody levels in blood than animals immunized with OVA only.

Conclusions: TEGDMA affects production of proinflammatory cytokines IL-1β, IL-6, IL-8, IL-18 and TNF-α. This inflammatogenic capacity renders TEGDMAs adjuvant properties, which may interfere with the homeostasis between the immune system and the indigenous microflora in the oral cavity.

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.

Release of monomers from orthodontic adhesives

INTRODUCTION

Most composite resins release both bisphenol A (BPA), which disrupts the endocrine balance, and triethylene glycol dimethacrylate (TEGDMA), which has high risks for human health: eg, allergies and cytotoxicity. The aim of this study was to characterize monomers released from orthodontic adhesives.

METHODS

We studied samples of orthodontic adhesives by associating 2 techniques: gas phase chromatography and mass spectrometry.

RESULTS

The in-vitro analysis detected significant quantities of BPA, TEGDMA, and other monomers in orthodontic adhesives used in daily practice: Transbond XT, Transbond Supreme LV (both, 3M Unitek, Monrovia, Calif), Blugloo (Ormco, Orange, Calif), and MonoLok 2 (Rocky Mountain Orthodontics, Denver, Colo).

CONCLUSIONS

Clinicians should consider that orthodontic adhesives contain BPA, an endocrine disruptor; TEGDMA, an allergic and a cytotoxic compound; and carcinogenic genotoxic compounds. These molecules are not mentioned in the material safety data sheets. Manufacturers should declare all components of dental composites to identify these substances that may result in allergic or undesirable side effects for patients and dental staff.

Novel endodontic sealers induce cell cytotoxicity and apoptosis in a dose-dependent behavior and favorable response in mice subcutaneous tissue

OBJECTIVES

The objective of the present study is to evaluate the in vitro cytotoxicity and in vivo biocompatibility of two novel endodontic sealers: RealSeal XT1 and Sealapex Xpress on the subcutaneous connective tissue of mice.

MATERIALS AND METHODS

The cytotoxicity was assessed by cell viability using the MTT assay (one-way ANOVA), trypan blue test (Mann-Whitney) and cell apoptosis by flow cytometer. For the subcutaneous study, polyethylene tubes filled with the sealers were implanted in 70 BALB/c mice: 6 experimental groups (n = 10/group) and 2 control groups with empty tubes (n = 5/group). At the end of experimental periods (7, 21, and 63 days), the tissue was removed and histotechnically processed. Angioblastic proliferation and edema (Fisher's exact test) were evaluated, besides thickness measurement (μm) of the reactionary granulomatous tissue and neutrophil counts (Kruskal-Wallis and Dunn's post test; Mann-Whitney) (α = 0.05).

RESULTS

MTT assay, trypan blue, and analysis of apoptotic cells showed a dose-dependent direct effect: the more diluted the sealer, the less cytotoxic. Regarding the angioblastic proliferation and edema, difference between the sealers at 7 and 63 days occurred (p < 0.05). Both endodontic sealers initially promoted perimaterial tissue reaction as a foreign body granuloma and thus stimulated favorable tissue responses.

CONCLUSIONS

Both sealers showed a dose-dependent effect and promoted satisfactory subcutaneous tissue response; the sealer Sealapex Xpress was less cytotoxic and more biocompatible than RealSeal XT.

CLINICAL RELEVANCE

The step of root canal filling during endodontic treatment is highly important for the preservation of the periapical tissue integrity. Subcutaneous reaction to endodontic sealers enables scientific basis for clinical use.

Visible light cure characteristics of a cycloaliphatic polyester dimethacrylate alternative oligomer to bisGMA

Objective: The goal of this study was to characterize the light curing characteristics of a new oligomer PEM-665 designed to be used as an alternative monomer to BisGMA.

Materials and methods: PEM-665 (P) and BisGMA (B) solutions were prepared with triethylene glycol dimethacrylate (T) diluent in different weight proportions (70/30 and 50/50). Solutions containing 70% P and 30% T were designated as 70PT, 70%B and 30%T as 70BT, 50%P and 50%T as 50PT and 50%B and 50%T as 50BT. The initiators were CQ (EDMAB was used as amine accelerator for CQ) and DPO in 1% concentration. Eight solutions were prepared in a factorial design: 70PT/DPO; 70PT/CQ; 50PT/DPO; 50PT/CQ; 70BT/DPO; 70BT/CQ; 50BT/DPO; 50BT/CQ. BISCO VIP visible light was used to cure the monomer solutions using 30 s exposure time and 400 W power setting. TA Instruments Differential Scanning Calorimeter (DSC 2910) was used to determine the heat of cure (J/g) during polymerization at 37 °C, from which molar heat of cure (kJ/mole) and %Conversion values were estimated.

Results: Range of mean values as a function monomer selections were: heat of cure (J/g): 161.7 for 70PT/DPO system to 198.6 for 50BT/CQ system; molar heat of cure (kJ/mole): 67.3 for 70BT/DPO to 78.86 for 50PT/CQ; % conversion: 59.9 for 70BT/DPO to 70.3 for 50PT/CQ. Analysis of variance and Tukey HSD pairwise contrast showed statistically significant differences between % conversion means of PEM and BisGMA mixtures, with PEM mixtures showing significantly higher mean values.

Conclusions: The results suggest that PEM-665 is a promising candidate material for dental polymer applications.

Triethylene Glycol Dimethacrylate Induction of Apoptotic Proteins in Pulp Fibroblasts

Objective

Monomers such as triethylene glycol dimethacrylate (TEGDMA) can leach from dental composites. TEGDMA-induced apoptosis in human pulp has been reported. However, the apoptotic (pro or anti) proteins involved in this process remain unclear. Therefore, the purpose of this study was to determine which apoptotic proteins are enhanced or suppressed during TEGDMA-induced apoptosis.

Materials and Methods

Human pulp fibroblasts (HPFs) were incubated with different TEGDMA concentrations (0.125-1.0 mM) and cytotoxicity was determined. TEGDMA was shown to be cell cytotoxic at concentrations of 0.50 mM and higher. The highest concentration with no significant cytotoxicity was then incubated (0.25 mM TEGDMA) with the HPFs. Cell lysates were then prepared and the protein concentrations determined. Human Apoptosis Array kits were utilized to detect the relative levels of 43 apoptotic proteins.

Results

HPFs exposed to TEGDMA showed significant increases in multiple pro-apoptotic proteins such as Bid, Bim, Caspase 3, Caspase 8, and Cytochrome c at 24 hours. Some anti-apoptotic proteins were also altered.

Conclusions

The results indicated that TEGDMA activates both the extrinsic and intrinsic apoptotic pathways.

A novel three-dimensional scaffold for regenerative endodontics: materials and biological characterizations

An electrospun nanocomposite fibrous material holds promise as a scaffold, as well as a drug-delivery device to aid in root maturogenesis and the regeneration of the pulp-dentine complex. A novel three-dimensional (3D) nanocomposite scaffold composed of polydioxanone (PDS II®) and halloysite nanotubes (HNTs) was designed and fabricated by electrospinning. Morphology, structure, mechanical properties and cell compatibility studies were carried out to evaluate the effects of HNTs incorporation (0.5-10 wt% relative to PDS w/w). Overall, a 3D porous network was seen in the different fabricated electrospun scaffolds, regardless of the HNT content. The incorporation of HNTs at 10 wt% led to a significant (p < 0.0001) fibre diameter increase and a reduction in scaffold strength. Moreover, PDS-HNTs scaffolds supported the attachment and proliferation of human-derived pulp fibroblast cells. Quantitative proliferation assay performed with human dental pulp-derived cells as a function of nanotubes concentration indicated that the HNTs exhibit a high level of biocompatibility, rendering them good candidates for the potential encapsulation of distinct bioactive molecules. Collectively, the reported data support the conclusion that PDS-HNTs nanocomposite fibrous structures hold potential in the development of a bioactive scaffold for regenerative endodontics.

Pulpal and Periapical Response After Restoration of Deep Cavities in Dogs' Teeth With Filtek Silorane and Filtek Supreme XT Systems

Objective:

This study evaluated, histopathologically, the pulpal and periapical response to a silorane-based resin (Filtek Silorane) and a methacrylate-based nanoparticle resin (Filtek Supreme XT) in deep cavities in dogs, having zinc oxide and eugenol-based cement (ZOE) as a control.

Methods:

The tooth/bone blocks were collected after 10 and 90 days and processed for microscopic analysis of the dentin, pulp, and periapical tissues using a score system. Data were analyzed statistically by Kruskal-Wallis and Dunn post-test (α=0.05).

Results:

At 10 days, the pulp, connective tissue, and periodontal ligament showed normal characteristics. No resorption areas were observed. Both resins caused significantly less (p&lt;0.05) periapical and pulpal inflammatory response than ZOE. At 90 days, for all materials, the connective pulp tissue was healthy and dense, with a normal blood vessel system. The apical and periapical region had normal structure and thickness.

Conclusions:

The use of the Filtek Silorane and the Filtek Supreme XT resins caused no adverse pulpal and periapical reactions after restoration of deep dentin cavities in vivo.

Immortalized gingival fibroblasts as a cytotoxicity test model for dental materials

In vitro cytotoxicity test is an initial step to identify the harmful effects of new dental materials. Aim of this study was to develop a stable human cell line derived from normal gingival fibroblasts (hNOF) and to assess its feasibility in in vitro cytotoxicity testing. Immortalized human gingival fibroblasts (hTERT-hNOF) were successfully established with human telomerase reverse transcriptase gene transfection, preserving its phenotypical characteristics, replicative potential and biological properties. Utilizing standard cytotoxicity test modeling and dental materials, hTERT-hNOF were evaluated for their feasibility in cytotoxicity testing, compared with hNOF and L929 cells. Similar pattern of cytotoxic response was observed among hNOF, hTERT-hNOF and L929 cells. Cytotoxicity response of hTERT-hNOF was significantly similar to hNOF, moreover hTERT-hNOF and hNOF were found to be more sensitive towards the tested dental materials compared to L929 cells. This study suggested that hTERT-hNOF is an effective cytotoxic test model for dental materials.

Carboxylesterase expression in human dental pulp cells: role in regulation of BisGMA-induced prostanoid production and cytotoxicity

Biocompatibility of dentin bonding agents (DBA) and composite resin may affect the treatment outcome (e.g., healthy pulp, pulpal inflammation, pulp necrosis) after operative restoration. Bisphenol-glycidyl methacrylate (BisGMA) is one of the major monomers present in DBA and resin. Prior studies focused on salivary esterase for metabolism and degradation of resin monomers clinically. This study found that human dental pulp cells expressed mainly carboxylesterase-2 (CES2) and smaller amounts of CES1A1 and CES3 isoforms. Exposure to BisGMA stimulated CES isoforms expression of pulp cells, and this event was inhibited by catalase. Exogenous addition of porcine esterase prevented BisGMA- and DBA-induced cytotoxicity. Interestingly, inhibition of CES by bis(p-nitrophenyl) phosphate (BNPP) and CES2 by loperamide enhanced the cytotoxicity of BisGMA and DBA. Addition of porcine esterase or N-acetyl-l-cysteine prevented BisGMA-induced prostaglandin E(2) (PGE(2)) and PGF(2α) production. In contrast, addition of BNPP and loperamide, but not mevastatin, enhanced BisGMA-induced PGE(2) and PGF(2α) production in dental pulp cells. These results suggest that BisGMA may induce the cytotoxicity and prostanoid production of pulp cells, leading to pulpal inflammation or necrosis via reactive oxygen species production. Expression of CES, especially CES2, in dental pulp cells can be an adaptive response to protect dental pulp against BisGMA-induced cytotoxicity and prostanoid release. Resin monomers are the main toxic components in DBA, and the ester group is crucial for monomer toxicity.

Molecular toxicology of substances released from resin-based dental restorative materials

Resin-based dental restorative materials are extensively used today in dentistry. However, significant concerns still remain regarding their biocompatibility. For this reason, significant scientific effort has been focused on the determination of the molecular toxicology of substances released by these biomaterials, using several tools for risk assessment, including exposure assessment, hazard identification and dose-response analysis. These studies have shown that substances released by these materials can cause significant cytotoxic and genotoxic effects, leading to irreversible disturbance of basic cellular functions. The aim of this article is to review current knowledge related to dental composites' molecular toxicology and to give implications for possible improvements concerning their biocompatibility.

Biocompatibility of resin composites subcutaneously implanted in rats with experimentally induced arthritis

OBJECTIVE

To evaluate the biocompatibility of resin composite specimens with different curing efficiency, subcutaneously implanted in rats with experimentally induced arthritis.

METHODS

The amount of remaining CC bonds (%RDB) of hybrid resin composite specimens photopolymerized for 10s and 40s exposure time (n=3) was measured by micro-attenuated total reflectance Fourier transform infrared spectroscopy. Male Wistar rats (n=36) were classified in two groups (n=18) of healthy animals and of animals with experimentally induced arthritis. Resin composite specimens irradiated for 10s and 40s and calcium hydroxide control specimens were implanted subcutaneously in each animals' dorsum. Following 2-, 4- and 9-week periods the animals were sacrificed. The development of arthritis was defined by biochemical analysis and the changes in the relative weight of animals' organs (spleen, thymus, adrenals). Tissue reactions were examined histologically.

RESULTS

%RDB per site and exposure time showed statistically significant differences. Lowest %RDB values were recorded on 40s exposed specimens. Biochemical indices and relative organ weights demonstrated statistically significant differences between healthy animals and animals with arthritis. The health status of the animals and the materials used did not influence tissue response. First and second periods of sacrifice showed reduced propensity of connective tissue development in comparison to the third period. The same applied for the second period regarding the presence of giant cells.

SIGNIFICANCE

The materials tested and the animals' health status did not result in altered tissue response compared to control group. The period of sacrifice was associated with different tissue responses.