Effects of two low-shrinkage composites on dental stem cells (viability, cell damaged or apoptosis and mesenchymal markers expression)

The spatial distribution, health risk, and cytotoxicity of metal(loid)s in contaminated field soils: The role of Cd in human gastric cells damage

The spatial distribution and pollution level of heavy metal(loid)s in soil (0-6 m) from a typical industrial region in Jiangmen City, Southeast China was investigated. Their bioaccessibility, health risk, and human gastric cytotoxicity in topsoil were also evaluated using an in vitro digestion/human cell model. The average concentrations of Cd (87.52 mg/kg), Co (106.9 mg/kg), and Ni (1007 mg/kg) exceeded the risk screening values. The distribution profiles of metal(loid)s showed a downward migration trend to reach a depth of 2 m. The highest contamination was found in topsoil (0-0.5 m), with the concentrations of As, Cd, Co, and Ni being 46.98, 348.28, 317.44, and 2395.60 mg/kg, respectively, while Cd showed the highest bioaccessibility in the gastric phase (72.80 %), followed by Co (21.08 %), Ni (18.27 %), and As (5.26 %) and unacceptable carcinogenic risk. Moreover, the gastric digesta of topsoil suppressed the cell viability and triggered cell apoptosis, evidenced by disruption of mitochondrial transmembrane potential and increase of Cytochrome c (Cyt c) and Caspases 3/9 mRNA expression. Bioaccessible Cd in topsoil was responsible for those adverse effects. Our data suggest the importance to reduce Cd in the soil to decrease its adverse impacts on the human stomach.

Conditional Mitigation of Dental-Composite Material-Induced Cytotoxicity by Increasing the Cure Time

Light-cured composite resins are widely used in dental restorations to fill cavities and fabricate temporary crowns. After curing, the residual monomer is a known to be cytotoxic, but increasing the curing time should improve biocompatibility. However, a biologically optimized cure time has not been determined through systematic experimentation. The objective of this study was to examine the behavior and function of human gingival fibroblasts cultured with flowable and bulk-fill composites cured for different periods of time, while considering the physical location of the cells with regard to the materials. Biological effects were separately evaluated for cells in direct contact with, and in close proximity to, the two composite materials. Curing time varied from the recommended 20 s to 40, 60, and 80 s. Pre-cured, milled-acrylic resin was used as a control. No cell survived and attached to or around the flowable composite, regardless of curing time. Some cells survived and attached close to (but not on) the bulk-fill composite, with survival increasing with a longer curing time, albeit to <20% of the numbers growing on milled acrylic even after 80 s of curing. A few cells (<5% of milled acrylic) survived and attached around the flowable composite after removal of the surface layer, but attachment was not cure-time dependent. Removing the surface layer increased cell survival and attachment around the bulk-fill composite after a 20-s cure, but survival was reduced after an 80-s cure. Dental-composite materials are lethal to contacting fibroblasts, regardless of curing time. However, longer curing times mitigated material cytotoxicity exclusively for bulk-fill composites when the cells were not in direct contact. Removing the surface layer slightly improved biocompatibility for cells in proximity to the materials, but not in proportion to cure time. In conclusion, mitigating the cytotoxicity of composite materials by increasing cure time is conditional on the physical location of cells, the type of material, and the finish of the surface layer. This study provides valuable information for clinical decision making and novel insights into the polymerization behavior of composite materials.

How the Duration and Mode of Photopolymerization Affect the Mechanical Properties of a Dental Composite Resin

Composite materials are the most common materials in use in modern dentistry. Over the years, the methods of photopolymerization of composite materials have been improved with the use of various devices, such as quartz tungsten halogen lamps (QTHs), light-emitting diode units (LEDs), plasma-arc lamps and argon-ion lasers. This study aimed to compare the mechanical properties of a composite material, depending on the time and mode of photopolymerization. One hundred and forty rectangular specimens (25 × 2 × 2 mm) and forty-two disc-shaped samples (5 mm diameter and 2 mm thickness) were prepared from shade A2 Boston composite resin. Samples were cured using the following seven photopolymerization protocols: four fast-cure modes (full power for 3, 5, 10, and 20 s), two pulse-cure modes (5 and 10 shots of 1 s exposures at full power), and one step-cure mode (soft start with a progressive cycle lasting 9 s). Specimens were subjected to a flexural strength test, Vickers microhardness test, and FTIR spectroscopy test. A 2-factor ANOVA and post-hoc tests were carried out to assess the differences in the flexural strength parameter between the tested groups of samples before and after aging. A mixed-model ANOVA was carried out to assess the differences in the Vickers microhardness parameter between the tested groups of samples before and after aging. The lowest values of flexural strength (p < 0.001) and Vickers microhardness (p < 0.001) were obtained for the 3 s mode for the pre- and post-aging groups. The FTIR mapping tests showed a much more homogeneous chemical structure of the composite after 20 s of continuous irradiation, compared to the sample irradiated for 5 s in the continuous mode. The mode and cure time affects the mechanical properties of the composite resin. Appropriate selection of the cure mode and time ensures better mechanical properties of composite resin. This suggests that the survival of dental restorations within the oral cavity could be extended by using longer photopolymerization durations.

Investigating the residual effect of silver nanoparticles gel as an intra-canal medicament on dental pulp stromal cells

BACKGROUND

The aim of this study was to evaluate the indirect effects of residual silver nanoparticles (AgNPs) gel on human dental pulp stromal cells (DPSCs).

METHODS

Ninety-five dentin discs (4x4x1 mm) were prepared from freshly extracted human single-rooted teeth following institutional ethical approval and informed consent. Samples were cleaned, autoclaved, and treated with: 1.5%NaOCl, Saline and 17% EDTA then randomly assigned to 5 groups that received 50 μl of one of the following treatments: 0.01%AgNPs, 0.015%AgNPs, 0.02%AgNPs, Calcium hydroxide (Ca (OH)₂) or no treatment for 1 week. Discs were washed with Saline and 17%EDTA then seeded with DPSCs and incubated for 3 and 7 days. At 24 hours unattached cells were collected and counted. At each time point cytotoxicity (LDH assay), cell viability (live/dead staining and confocal microscopy) and cell proliferation (WST1 assay) were assessed. All experiments were repeated a minimum of 3 times using DPSCs isolated from 3 different donors for each time point assessed (n = 9/group). Statistical analysis was done using One-Way ANOVA followed by Tukey's test and Kruskal Wallis followed by post-hoc comparisons with significance set at p ≤ 0.05.

RESULTS

After 24 hours, the percentage of DPSCs attachment ranged between 92.66% ±4.54 and 95.08% ±1.44 with no significant difference between groups (P = 0.126). Cell viability was ≥92% at 24 hours for all groups. However this percentage dropped to less than 60% at 3 days then started to rise again at 7 days. There was no significant difference in cytotoxicity between different groups at all time points except for 0.01%AgNPs group which had the highest cytotoxicity. DPSCs proliferation increased significantly from 3 to 7 days in all groups except for Ca (OH)₂ which showed lower proliferation rates at both 3 (45.89%) and 7 days (79.25%).

CONCLUSION

Dentin discs treated for 7 days with concentrations of AgNPs gel (0.01-0.02%) allowed more than 90% DPSCs cell attachment after 24 hours. The cytotoxicity and proliferation of DPSCs in response to AgNPs gel were comparable to those with calcium hydroxide. This suggests that AgNPs gel may represent a promising future candidate for clinical use in regenerative endodontics. However, its effects may be concentration-dependent warranting further investigation.

Are Endodontic Solvents Cytotoxic? An In Vitro Study on Human Periodontal Ligament Stem Cells

The aim of this study was to assess the influence of eucalyptol, chloroform, and Endosolv on the proliferative capability, cell viability, and migration rates of human periodontal ligament stem cells (hPDLSCs) in vitro. Solvent eluates were formulated following ISO 10993-5 guidelines, and 1%, 0.25%, and 0.1% dilutions were prepared. The HPDLSCs were isolated from the extracted third molars of healthy donors. The following parameters were assessed: cell viability via trypan blue and IC50 assays, cell migration via horizontal wound healing assay, cell morphology via cell cytoskeleton staining (phalloidin labeling), and cell oxidative stress via reactive oxygen species assay. The data were analyzed using one-way ANOVA and Tukey’s posthoc tests, and their significance was established at p < 0.05. Chloroform and eucalyptol exhibited significantly higher cytotoxicity on the hPDLSCs in vitro compared to the control group, as shown by the cell viability, migration, morphology, and reactive oxygen species release assays. Alternatively, Endosolv showed adequate cytotoxicity levels comparable to those of the control group. The cytotoxicity of the tested endodontic solvents increased in a dose-dependent manner. The results from the present study highlight the cytotoxicity of chloroform and eucalyptol. Thus, their limited and cautious use is recommended, avoiding solvent extrusion.

Multiple growth factors accommodated degradable submicron calcium sulfate hemihydrate/porous hydroxyapatite for dentin-pulp regeneration

Vital pulp therapy (VPT) has gained significant consideration by utilizing the natural healing capacity of the inflamed pulp in healing process. However, the protective pulp capping materials that facilitate this healing process are still under investigation for the successful promotion of dentin-pulp regeneration. Herein, we developed a bioactive and biodegradable pulp capping material (denoted as sCSHA-GFs) by synthesizing inorganic submicron calcium sulfate hemihydrate (sCS)/porous hydroxyapatite (HA) loaded with growth factors (GFs) such as transforming growth factor-beta 1 (TGF-β1), fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF). Physiochemical characteristics of submicron CSHA-GFs (sCSHA-GFs) cement were determined. Human dental pulp stem cells (hDPSCs) were used for analyzing their biocompatibility and bioactivity for dentin mineralization. To evaluate the efficacy of sCSHA-GFs, we compared it with a commercial material, mineral trioxide aggregate (MTA), the reference standard used clinically on pulp capping. Our results showed that sCSHA-GFs cement presented good biodegradability with dissolution properties for sustained release of calcium (Ca²⁺) ions and GFs, and facilitated attachment, proliferation, differentiation and migration of hDPSCs. In addition, sCSHA-GFs cement was found to be more effective than MTA at prolonged incubation time in inducing the mRNA expression levels of odontoblastic differentiation markers, dentin sialophosphoprotein (DSPP) and dentin matrix protein (DMP-1), leading to increased mineralization (with calcium deposits) along with increased alkaline phosphatase (ALP) expressions, evident from Alizarin Red S and ALP staining assays. Our findings suggest that sCSHA-GFs cement may act as a suitable material in VPT for dentin-pulp regeneration.

Effects of nanohybrid, flowable, resin-based composites on fibroblast viability using different light-curing units

PURPOSE

To investigate the in vitro cytotoxic effects of Bis-GMA-containing and Bis-GMA-free flowable resin-based composites (RBCs) on primary human gingival fibroblast cells (hGFc) using direct and indirect curing methods and three different light-curing units (LCUs) MATERIALS AND METHODS: Cells were isolated and cultured in vitro in 24-well plates. The plates were divided into treatment (cells with RBC), control (cells only), and blank (media only) groups. In the treatment groups, two types of nanohybrid flowable RBCs were used: Bis-GMA-free and Bis-GMA groups. Each treatment group was subdivided according to the curing method, i.e., direct curing (RBC was injected into the wells and cured directly on the attached cells) and indirect curing (the samples were pre-cured outside of the well plate and then added to the well plate with cells). To vary the LCU, the subgroups were further divided into three groups: multiple-emission peak light-emitting diode, single-emission peak light-emitting diode, and quartz-tungsten-halogen units. Curing was conducted for 20 s. The hGFc cytotoxicity was evaluated via 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay after 24, 48, and 72 h of culturing RESULTS: The MTT assay results showed that both RBCs were significantly cytotoxic toward hGFc compared to the control group (p < 0.0001). The Bis-GMA group was significantly more cytotoxic to the cells compared to the Bis-GMA-free group. In addition, the curing method and time interval affected cell viability regardless of the LCU used CONCLUSION: The Bis-GMA flowable RBC and direct curing method had the highest cytotoxic effects on hGFc regardless of the LCU used. Careful selection of flowable RBCs and proper curing techniques are required to decrease the cytotoxic effects on hGFc and improve the clinical handling of oral tissues. This article is protected by copyright. All rights reserved.

Depth of Cure, Hardness, Roughness and Filler Dimension of Bulk-Fill Flowable, Conventional Flowable and High-Strength Universal Injectable Composites: An In Vitro Study

(1) Objective: To evaluate and compare the depth of cure (DOC) of two bulk-fill flowable composites (Filtek Bulk Fill Flowable Restorative and Tetric EvoFlow Bulk Fill), two conventional flowable composites (Filtek Supreme XTE Flowable Restorative and G-ænial Flo X) and one high-strength universal injectable composite (G-ænial Universal Injectable). (2) Methods: specimens were placed in a stainless-steel mold with an orifice of 4 mm in diameter and 10 mm in depth and light-cured for 20 s using a light emitting diode (LED) light-curing unit (LCU) with an irradiance of 1000 mW/cm2; depth of cure was assessed using the ISO 4049 scrape technique, and the absolute length of the specimen of cured composite was measured in millimeters with a digital caliper. The same procedure was repeated with 14 samples for each material under investigation, for a total number of 70 test bodies. Material roughness and hardness results were also investigated using, respectively, a 3D laser confocal microscope (LEXT OLS 4100; Olympus) at ×5 magnification and a Vickers diamond indenter (Vickers microhardness tester, Shimadzu®, Kyoto, Japan) under 10-N load and a 30 s dwell time. SEM images at 3000 and 9000 magnification were collected in order to study the materials’ filler content. Statistical analysis were performed by a commercial statistical software package (SPSS) and data were analyzed using multiple comparison Dunnett’s test. (3) Results: The average DOC of both bulk-fill composites was more than 4 mm, as a range of 3.91 and 4.53 mm with an average value of 4.24 and 4.12 mm, while that of the conventional flowable composites was much lower, as a range of 2.47 and 2.90 mm with an average value of 2.58 and 2.84 mm; DOC of the high-strength injectable composite was greater than the one of traditional composites, but not to the level of bulk-fill materials, as a range of 2.82 and 3.01 mm with an average value of 3.02 mm. Statistical analysis revealed significant differences (p-values < 0.05) in the depth of cure between bulk fill flowable composites and other composites, while there was no difference (p-values > 0.05) between the materials of the same type. (4) Conclusions: Bulk-fill flowable composites showed significantly higher depth of cure values than both traditional flowable composites and high-strength injectable composites.

The Cytocompatibility of Silver Diamine Fluoride on Mesenchymal Stromal Cells from Human Exfoliated Deciduous Teeth: An In Vitro Study

Silver diamine fluoride (SDF) has been used for many years for the treatment of caries, and minimally invasive dentistry concepts have made it popular again. The fact that its application does not require the administration of anesthesia makes its use in children more desirable. The aim of this study was to determine the cytotoxicity of two new commercial SDF products: Riva Star (SDI Dental Limited) and e-SDF (Kids-e-Dental) on mesenchymal stromal cells from human exfoliated deciduous teeth (SHEDs). SHEDs were exposed to SDF products at different concentrations (0.1%, 0.01% and 0.005%). Then different assays were performed to evaluate their cytocompatibility on SHEDs: IC50, MTT, cell migration (wound healing), cell cytoskeleton staining, cell apoptosis, generation of intracellular reactive oxygen species (ROS), and ion chromatography. Statistical analyses were performed using one-way ANOVA and Tukey’s post hoc test (p < 0.05). Riva Star Step 2 showed the same cell metabolic activity when compared to the control condition at any time and concentration. Meanwhile, e-SDF displayed high cytotoxicity at any time and any concentration (*** p < 0.001), whereas Riva Star Step 1 displayed high cytotoxicity at any time at 0.1% and 0.01% (*** p < 0.001). Only e-SDF showed a statistically significant decreased cell migration rate (*** p < 0.001) at all times and in all concentrations. At 0.1%, e-SDF and Riva Star Step 1 only showed 4.37% and 4.47% of viable cells, respectively. These results suggest that Riva Star has better in vitro cytocompatibility on SHEDs than does e-SDF. Riva Star Step 1 was found to be as cytotoxic as e-SDF, but it had better biological properties when mixed with Riva Star Step 2. Our findings suggest that Riva Star is more suitable when used in deciduous teeth due to its lower cytotoxicity compared to e-SDF.

A Reliable Method of Measuring the Conversion Degrees of Methacrylate Dental Resins

The main aim of the study was to implement the most reliable method of measuring the degrees of conversion during photopolymerization of dental fillings. Contrary to the methods used so far, the method is based only on comparison with the monomer absorbance spectrum without reference bands. Another aim of the study was to prepare a comparative analysis of the polymerization kinetics of dental resins under various light sources and different environmental conditions (irradiance, light dose, temperature), with estimation of the degrees of conversion (DC) of the resins being the main metric. HRi Universal Enamel (UE2) and HRi Universal Dentine (UD2) were examined under two different types of light sources used in dentistry, LED and halogen. DC was measured by Fourier transform infrared spectroscopy (FTIR) in transmission mode from 5 s up to 7 days. Spectra were recorded from the parallel optical layers of samples that were placed between the KBr crystals. The results are expressed by the changes in the absorbance spectrum during the polymerization and the calculated conversion rates. The results of each experiment were averaged from three separate measurements of three samples, during which the samples were illuminated under identical conditions. The data were analyzed by performing ANOVA test comparisons between sample groups at the significance level α = 0.05. The degree of conversion of the UD2 resin was higher than that of UE2 for each experimental condition, but there was no statistically significant difference between the DC of those materials (p > 0.05). There was statistically significant difference (p < 0.01) in the DC caused by LED and halogen light sources producing the same light doses (38 J/cm2). This was the result of different features of light transmission to the filler in the resin composite. The efficacy of the LED source is twice as high as that of the halogen light source. Maximal DC without any other differences in conditions, such as resin type or light source, reached around 70% for temperatures of 22−37 °C. For 37 °C, this took 24 h, which is a contrast to the 7 days it took for 23 °C. The influences of different conditions and factors on reaction kinetics are only strong in the early and the rapid stage of conversion. The optimal time of irradiance using either light source is 20 s for a monolayer, and its thickness should not exceed 2 mm.

Comparative cytocompatibility of the new calcium silicate-based cement NeoPutty versus NeoMTA Plus and MTA on human dental pulp cells: an in vitro study

OBJECTIVES

The aim of the present in vitro study is to determine the cytocompatibility of the recently introduced NeoPutty in contact with human dental pulp cells compared with its precursor NeoMTA Plus and the classic gold standard MTA Angelus.

MATERIALS AND METHODS

Sample disks were obtained for each of the tested materials (5 mm diameter; 2 mm thickness; n = 30), along with 1:1, 1:2, and 1:4 material eluents. HDPCs were extracted and cultured with the tested materials (test groups) or in unconditioned medium (control group), and the following biocompatibility assays were performed: MTT assay, scratch wound assay, cell cytoskeleton staining assays, and cell attachment assessment via SEM. Additionally, material ion release and surface element composition were evaluated via ICP-MS and SEM-EDX, respectively. Each experimental condition was carried out three times and assessed in three independent experiments. Statistical significance was established at p < 0.05.

RESULTS

1:2 dilutions of all the tested materials exhibited a comparable cell viability to that of the control group at 48 and 72 h of culture (p < 0.05). The same was observed for 1:4 dilutions of the tested materials at 24, 48, and 72 h of culture (p > 0.05). All the tested materials exhibited adequate cytocompatibility in the remaining biocompatibility assays. MTA exhibited a significantly higher calcium ion release compared to NeoPutty and NeoMTA Plus (p < 0.05).

CONCLUSION

The results from the present work elucidate the adequate cytocompatibility of NeoPutty, NeoMTA Plus, and MTA Angelus towards human dental pulp cells.

CLINICAL RELEVANCE

Within the limitations of the present in vitro study, our results may act as preliminary evidence for its use in vital pulp therapy as a pulp capper. However, results need to be interpreted with caution until further clinical supporting evidence is reported.

Effects of Monomer Composition of Urethane Methacrylate Based Resins on the C=C Degree of Conversion, Residual Monomer Content and Mechanical Properties

(1) Background: This study investigated the influence of Bis-GMA, TEGDMA, UDMA, and two different polyethylene glycol (PEG)-containing, UDMO-based co-monomers on the Young’s modulus and flexural strength, degree of methacrylate C=C double bond conversion and residual monomer elution of experimental dental resins. (2) Methods: Urethane methacrylate-based monomer was synthesised via a radical chain growth polymerization mechanism using PEG in order to improve the mechanical properties. Dental resins were formulated using Bis-GMA, UDMA, or UDMO as base monomers combined with TEGDMA as a dilution monomer and DMAEM + CQ as the photo-initiator system. Degree of conversion (DC), mechanical properties, and residual monomer content of light-activated methacrylate resin formulations were evaluated and statistically analysed by ANOVA and a Tukey’s test. (3) Results: PEG-containing UDMO resins had lower Young’s modulus and elastic strength than UDMA-derived resin for all irradiation times. The highest DC (67,418%) was observed for the PEG-containing UDMO-based resin formulation when light cured for 40 s. For all samples, DC increased with the photo-polymerization time. The amount of residual monomer decreased after increasing the light-curing period from 20 to 40 s, resin with UDMO content 0.01 mol of PEG having the smallest amount of free eluted monomer. (4) Conclusions: A strong structure–property relationship exists in photo-cured dimethacrylate-based dental resins. The time and quantity of the photochemical initiation system can influence the physical–mechanical properties of the resins but also the monomers in their composition.

Raman and XANES Spectroscopic Study of the Influence of Coordination Atomic and Molecular Environments in Biomimetic Composite Materials Integrated with Dental Tissue

In this work, for the first time, the influence of the coordination environment as well as Ca and P atomic states on biomimetic composites integrated with dental tissue was investigated. Bioinspired dental composites were synthesised based on nanocrystalline calcium carbonate-substituted hydroxyapatite Ca4ICa6IIPO46−xCO3x+yOH2−y (nano-cHAp) obtained from a biogenic source and a set of polar amino acids that modelled the organic matrix. Biomimetic composites, as well as natural dental tissue samples, were investigated using Raman spectromicroscopy and synchrotron X-ray absorption near edge structure (XANES) spectroscopy. Molecular structure and energy structure studies revealed several important features related to the different calcium atomic environments. It was shown that biomimetic composites created in order to reproduce the physicochemical properties of dental tissue provide good imitation of molecular and electron energetic properties, including the carbonate anion CO₃²⁻ and the atomic Ca/P ratio in nanocrystals. The features of the molecular structure of biomimetic composites are inherited from the nano-cHAp (to a greater extent) and the amino acid cocktail used for their creation, and are caused by the ratio between the mineral and organic components, which is similar to the composition of natural enamel and dentine. In this case, violation of the nano-cHAp stoichiometry, which is the mineral basis of the natural and bioinspired composites, as well as the inclusion of different molecular groups in the nano-cHAp lattice, do not affect the coordination environment of phosphorus atoms. The differences observed in the molecular and electron energetic structures of the natural enamel and dentine and the imitation of their properties by biomimetic materials are caused by rearrangement in the local environment of the calcium atoms in the HAp crystal lattice. The surface of the nano-cHAp crystals in the natural enamel and dentine involved in the formation of bonds with the organic matrix is characterised by the coordination environment of the calcium atom, corresponding to its location in the Ca^I position—that is, bound through common oxygen atoms with PO₄ tetrahedrons. At the same time, on the surface of nano-cHAp crystals in bioinspired dental materials, the calcium atom is characteristically located in the Ca^II position, bound to the hydroxyl OH group. The features detected in the atomic and molecular coordination environment in nano-cHAp play a fundamental role in recreating a biomimetic dental composite of the natural organomineral interaction in mineralised tissue and will help to find an optimal way to integrate the dental biocomposite with natural tissue.

Assessing Biocompatibility of Face Mask Materials during COVID-19 Pandemic by a Rapid Multi-Assays Strategy

During the coronavirus disease 2019 (COVID-19) pandemic, scientific authorities strongly suggested the use of face masks (FMs). FM materials (FMMs) have to satisfy the medical device biocompatibility requirements as indicated in the technical standard EN ISO 10993-1:2018. The biologic evaluation must be confirmed by in vivo tests to verify cytotoxicity, sensitisation, and skin irritation. Some of these tests require an extensive period of time for their execution, which is incompatible with an emergency situation. In this study, we propose to verify the safety of FMMs combining the assessment of 3-[4,5-dimethylthiazolyl-2]-2,5-diphenyltetrazolium bromide (MTT) with quantification of nitric oxide (NO) and interleukin-6 (IL-6), as predictive markers of skin sensitisation or irritation based on human primary fibroblasts. Two hundred and forty-two FMMs were collected and classified according to spectrometer IR in polypropylene, paper, cotton, polyester, polyethylene terephthalate, 3-dimensional printing, and viscose. Of all FMMs tested, 50.8% passed all the assays, 48% failed at least one, and only 1.2% failed all. By a low cost, rapid and highly sensitive multi assays strategy tested on human skin fibroblasts against a large variety of FMMs, we propose a strategy to promptly evaluate biocompatibility in wearable materials.

Effect of preheating on the cytotoxicity of bulk-fill composite resins

Background. Due to the effect of pre-heating on the degree of conversion of composite resins and the possible effect on cytotoxicity, the effect of pre-heating of bulk-fill composite resins was investigated on cytotoxicity in this study. Methods. In this study, three different types of composite resin were used, including Tetric N-Ceram Bulk-Fil, Xtrafil, and Xtrabase. From each composite resin, 10 cylindrical samples (5 mm in diameter and 4 mm in height) were prepared, with five samples preheated to 68°C, and the other five samples polymerized at room temperature (25°C). Twenty-four hours after polymerization, cytotoxicity was assessed by MTT assay on human fibroblasts. Statistical analysis of data was carried out with two-way ANOVA and Sidak Post-Hoc. The significance level of the test was determined at 0.05. Results. There was no statistically significant difference between the mean percentage of cytotoxicity in terms of pre-heating (P>0.05), but the cytotoxicity of the studied composite resins was significantly different (P<0.001). The cytotoxicity of Tetric N-Ceram Bulk-fil composite resin was higher than that of the two other composite resins. Conclusion. Pre-heating of bulk-fill composite resin did not affect their cytotoxicity. In addition, the cytotoxicity of different bulk-fill composite resins was not the same.

Evaluation of the biocompatibility of resin composite-based dental materials with gingival mesenchymal stromal cells

Resin composite-based dental materials can leach certain components into the oral environment, causing potentially harmful gingival biological effect. Gingival tissue is a rich source of mesenchymal stem cells (MSCs) that is easily accessible, and can be used as a complementary approach for the investigation of dental material biocompatibility. Using gingival MSCs (gMSCs), the present study aimed to investigate the cytotoxicity of two classes of restorative dental materials (ormocers and resin composites) used to restore class II cavities close to the gingival margin, in addition to analyzing the leached compounds from these resin composite-based materials. Functionality assays (Colony-forming unit, migratory potential, and proliferation assays) and a viability assay (MTT) were employed. Cells' aspect was observed by scanning electron microscopy (SEM). Leached monomers were also quantitated using high-performance liquid chromatography (HPLC). The cytotoxicity of the biomaterials was highlighted by impaired functionality and diminished viability of gMSCs. Despite being variants of the same commercial material, the two ormocers behaved differently one material having a more negative impact on cell functionality than the other. Cells appeared to attach well to all materials. Main monomer molecules were mostly released by the tested materials. For all samples, an increased elution of monomers was recorded in artificial saliva as compared with culture medium. One composite material has released nearly eight times more urethane dimetacrylate in artificial saliva than in culture medium. Significantly lower gMSC viability scores were recorded for all the investigated samples in comparison with the control.

Applications of inflammation-derived gingival stem cells for testing the biocompatibility of dental restorative biomaterials

BACKGROUND

Normal or inflamed gingival tissues are regarded as a source of mesenchymal stem cells (MSCs) abundant and easily accessible through minimally invasive dental procedures. Due to the proximity of dental resin composites to gingival tissues and to the possible local cytotoxic effect of the eluted components, gingiva-derived MSCs could be used to investigate the biocompatibility of dental biomaterials.

PURPOSE

The present research aimed to isolate (MSCs) from inflamed and normal gingiva, to fully characterize them and to observe their behavior in relation with some commercial resin composite materials and one experimental material.

MATERIAL AND METHODS

Following their isolation, putative MSCs from both gingival sources were grown under the same culture conditions and characterized by immunophenotyping of cell surface antigens by flow-cytometry and transcription factors by immunocytochemical staining. Moreover, stemness gene expression was evaluated by RT-PCR analysis. Multipotent mesenchymal differentiation potential was investigated. Osteogenic and neurogenic differentiated cells were highlighted by immunocytochemical staining, chondrogenic cells by cytochemical staining, and adipocytes by cytochemical staining and spectrophotometry, respectively. Resin composite cytotoxicity was evaluated by cell membrane fluorescent labeling with PKH 26 and MTT assay. The results of PKH labeling were statistically analysed using two-way RM ANOVA with Bonferroni post-tests. For MTT assay, two-way RM ANOVA with Bonferroni post-tests and unpaired t test with Welch's correction were used.

RESULTS

A similar expression pattern of surface markers was observed. The cells were positive for CD105, CD73, CD90, CD49e, CD29, CD44 and CD166 and negative for CD45, CD34, CD14, CD79, HLA-DR and CD117 indicating a mesenchymal stem cell phenotype. The qRT-PCR analysis revealed a low gene expression for NOG, BMP4 and Oct3/4 and an increased expression for Nanog in both cells lines. Immunocytochemical analysis highlighted a more intense protein expression for Nanog, Oct3/4 and Sox-2 in MSCs derived from normal gingiva than from inflamed gingiva. Multipotent differentiation capacity of MSCs isolated from both sources was highlighted. The tested materials had no hazardous effect on MSCs as the two cell lines developed well onto resin composite substrates. Cell counting revealed some significant differences in the number of PKH-labeled MSCs at some experimental moments. Also, some differences in cell viability were recorded indicating better developmental conditions offered by some of the tested biomaterials.

CONCLUSIONS

The experimental resin composite behaved like the most biocompatible commercial material. Inflamed gingiva-derived MSCs retain their stem cell properties and could be used as a valuable cell line for testing dental biomaterials.

Stem Cells from Dental Pulp: What Epigenetics Can Do with Your Tooth

Adult stem cells have attracted scientific attention because they are able to self-renew and differentiate into several specialized cell types. In this context, human dental tissue-derived mesenchymal stem cells (hDT-MSCs) have emerged as a possible solution for repairing or regenerating damaged tissues. These cells can be isolated from primary teeth that are naturally replaced, third molars, or other dental tissues and exhibit self-renewal, a high proliferative rate and a great multilineage potential. However, the cellular and molecular mechanisms that determine lineage specification are still largely unknown. It is known that a change in cell fate requires the deletion of existing transcriptional programs, followed by the establishment of a new developmental program to give rise to a new cell lineage. Increasing evidence indicates that chromatin structure conformation can influence cell fate. In this way, reversible chemical modifications at the DNA or histone level, and combinations thereof can activate or inactivate cell-type-specific gene sequences, giving rise to an alternative cell fates. On the other hand, miRNAs are starting to emerge as a possible player in establishing particular somatic lineages. In this review, we discuss two new and promising research fields in medicine and biology, epigenetics and stem cells, by summarizing the properties of hDT-MSCs and highlighting the recent findings on epigenetic contributions to the regulation of cellular differentiation.

Chemical characterization of simulated landfill soil leachates from Nigeria and India and their cytotoxicity and DNA damage inductions on three human cell lines

Landfill soils are sources of emerging carcinogens, teratogens and mutagens in the environment. There is inadequate information on its possible health risk and cytogenotoxicity. This study evaluated chemical characterization of four simulated landfill leachates with their cytotoxicity and DNA damage in human cells. Hepatocarcinoma (HepG2), lymphoma (Jurkat) and osteosarcoma (HOS) cells, incubated with 6.25, 12.5, 25, 50, 75 and 100% of Aba Eku (AEL), Olusosun (OSL), Awotan (AWL) and Nagpur (NPL) simulated leachates for 24 h, were assessed for cell viability using MTT assay and morphological alterations. DNA damage was also assessed after 24 h treatment of cells with sub-lethal concentrations of the leachates using comet assay. Metals and organic compounds in the soil leachates were determined using inductively coupled plasma-mass spectrometry (ICP-MS) and gas chromatography-mass spectroscopy (GC-MS) respectively. The leachates induced significant cytotoxicity in the treated cells with evidence of apoptosis; shrunken morphologies, detachment from the substratum and cytoplasmic vacuolations. Similarly, there was significant DNA damage induced in the treated cells, with increased Olive tail moment, tail length and % tail DNA. Jurkat was the most sensitive (Jurkat > HepG2 > HOS) to the cytotoxic and genotoxic effects of the leachates. All the analyzed metals except Cd, Fe, Zn and Mn were found at levels lower than standard allowable limits. 32, 17, 23 and 23 different PAHs and PCBs were detected in AEL, AWL, OSL and NPL respectively, at varying retention peak times. These toxic constituents induced the observed cytogenotoxicity in the cells and may suggest possible public health risk.

Effects of composite films of silk fibroin and graphene oxide on the proliferation, cell viability and mesenchymal phenotype of periodontal ligament stem cells

In regenerative dentistry, stem cell-based therapy often requires a scaffold to deliver cells and/or growth factors to the injured site. Graphene oxide (GO) and silk fibroin (SF) are promising biomaterials for tissue engineering as they are both non toxic and promote cell proliferation. On the other hand, periodontal ligament stem cells (PDLSCs) are mesenchymal stem cells readily accessible with a promising use in cell therapy. The purpose of this study was to investigate the effects of composite films of GO, SF and GO combined with fibroin in the mesenchymal phenotype, viability, adhesion and proliferation rate of PDLSCs. PDLSCs obtained from healthy extracted teeth were cultured on GO, SF or combination of GO and SF films up to 10 days. Adhesion level of PDSCs on the different biomaterials were evaluated after 12 h of culture, whereas proliferation rate of cells was assessed using the MTT assay. Level of apoptosis was determined using Annexin-V and 7-AAD and mesenchymal markers expression of PDLSCs were analyzed by flow cytometry. At day 7 of culture, MTT experiments showed a high rate of proliferation of PDLSCs growing on GO films compared to the other tested biomaterials, although it was slightly lower than in plastic (control). However PDLSCs growing in fibroin or GO plus fibroin films showed a discrete proliferation. Importantly, at day 10 of culture it was observed a significant increase in PDLSCs proliferation rate in GO films compared to plastic (P < 0.05), as well as in GO plus fibroin compared to fibroin alone (P < 0.001). Flow cytometry analysis showed that culture of PDLSCs in fibroin, GO or GO plus fibroin films did not significantly alter the level of expression of the mesenchymal markers CD73, CD90 or CD105 up to 168 h, being the cell viability in GO even better than obtained in plastic. Our findings suggest that the combination of human dental stem cells/fibroin/GO based-bioengineered constructs have strong potential for their therapeutic use in regenerative dentistry.

Thermal, spectral, and surface properties of LED light-polymerized bulk fill resin composites

The aim of this study was to evaluate the thermal, spectral, and surface properties of four different bulk fill materials – SureFil SDR (SDR, Dentsplay DETREY), QuixFil (QF, Dentsplay DETREY), X-tra base (XB, Voco) X-tra fil (XF, Voco) – polymerized by light-emitting diode (LED). Resin matrix, filler type, size and amount, and photoinitiator types influence the degree of conversion. LED-cured bulk fill composites achieved sufficient polymerization. Scanning electron microscope (SEM) analysis revealed different patterns of surface roughness, depending on the composite material. Bulk fill materials showed surface characteristics similar to those of nanohybrid composites. Based on the thermal analysis results, glass transition (T(g)) and initial degradation (T(i)) temperatures changed depending on the bulk fill resin composites.