Epigallocatechin-3-Gallate Reduces Cytotoxic Effects Caused by Dental Monomers: A Hypothesis

Optimal resin monomer ratios for light-cured dental resins

Monomer ratios play a crucial role on the performances of dental resins, the optimal monomer ratios for dental resins are determined by combining the degree of conversion (DC), rate of polymerization (Rp), and mechanical properties, based on commonly-used Bis-GMA (bisphenol A-glycidyl methacrylate), UDMA (urethane dimethacrylate), and TEGDMA (triethyleneglycol dimethacrylate) resins. The DC and mechanical properties of the dental resins are examined by NIR (Near Infrared Ray) spectroscopy and nanoindentation tests, respectively. The results indicate that the Rp increases while the DC decreases with the loading content of Bis-GMA or UDMA in dental resins (i.e., Bis-GMA/TEGDMA and UDMA/TEGDMA). Meanwhile, both elastic modulus and hardness also present a tendency to increase. Various different monomers maybe create a strong polymer matrix in proper proportions, comprehensively comparing the performances of dental resins in different monomer ratios, the cured resins containing Bis-GMA (15–35 wt%), UDMA (37–60 wt%) and TEGDMA (20–35 wt%) show better material properties. The present study offers a quantitative analysis for Bis-GMA/UDMA/TEGDMA dental resins as well as provides guidance for the research of dental resins.

Prosthetic Materials Used for Implant-Supported Restorations and Their Biochemical Oral Interactions: A Narrative Review

The purpose of this study is to outline relevant elements regarding the biochemical interactions between prosthetic materials used for obtaining implant-supported restorations and the oral environment. Implant-supported prostheses have seen unprecedented development in recent years, benefiting from the emergence of both new prosthetic materials (with increased biocompatibility and very good mechanical behavior), and computerized manufacturing technologies, which offer predictability, accuracy, and reproducibility. On the other hand, the quality of conventional materials for obtaining implant-supported prostheses is acknowledged, as they have already proven their clinical performance. The properties of PMMA (poly (methyl methacrylate))-which is a representative interim material frequently used in prosthodontics-and of PEEK (polyether ether ketone)-a biomaterial which is placed on the border between interim and final prosthetic use-are highlighted in order to illustrate the complex way these materials interact with the oral environment. In regard to definitive prosthetic materials used for obtaining implant-supported prostheses, emphasis is placed on zirconia-based ceramics. Zirconia exhibits several distinctive advantages (excellent aesthetics, good mechanical behavior, biocompatibility), through which its clinical applicability has become increasingly wide. Zirconia's interaction with the oral environment (fibroblasts, osteoblasts, dental pulp cells, macrophages) is presented in a relevant synthesis, thus revealing its good biocompatibility.

New insights into the role of the Nrf2 signaling pathway in green tea catechin applications

Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a transcriptional signaling pathway that plays a crucial role in numerous clinical complications. Pivotal roles of Nrf2 have been proved in cancer, autoimmune diseases, neurodegeneration, cardiovascular diseases, diabetes mellitus, renal injuries, respiratory conditions, gastrointestinal disturbances, and general disorders related to oxidative stress, inflammation, apoptosis, gelatinolysis, autophagy, and fibrogenesis processes. Green tea catechins as a rich source of phenolic compounds can deal with various clinical problems and manifestations. In this review, we attempted to focus on intervention between green tea catechins and Nrf2. Green tea catechins especially epigallocatechin gallate (EGCG) elucidated the protective role of Nrf2 and its downstream molecules in various disorders through Keap-1, HO-1, NQO-1, GPx, GCLc, GCLm, NF-kB cross-link, kinases, and apoptotic proteins. Subsequently, we compiled an updated expansions of the Nrf2 role as a gate to manage and protect different disorders and feasible indications of green tea catechins through this signaling pathway. The present review highlighted recent evidence-based data in silico, in vitro, and in vivo studies on an outline for future clinical trials.

Effects of epigallocatechin gallate (EGCG) on the biological properties of human dental pulp stem cells and inflammatory pulp tissue

OBJECTIVE

This study aimed to investigate the effect of epigallocatechin gallate (EGCG) on the proliferation, mineralization, inflammation and hypoxia responses of human dental pulp stem cells (hDPSCs) in vitro and its effect on inflammatory pulp tissue in rats in vivo.

DESIGN

The optimum concentration of EGCG was selected by creating a dose response curve. Expression of odontogenic/osteogenic-related genes and inflammatory cytokines after stimulation with Lipopolysaccharide (LPS) was detected by real-time PCR. Under hypoxic conditions, cell proliferation and expression of reactive oxygen species (ROS) and superoxide dismutase (SOD) were detected.In vivo, the maxillary first molars of SD rats were pulpotomized and stimulated with 5 mg/mL LPS for 30 min. Normal saline and EGCG were used to flush the pulp chamber. After 2 months, samples were removed for micro-CT scanning and HE staining.

RESULTS

CCK-8 assay revealed that 10 μg/mL EGCG had no significant effect on the proliferation of hDPSCs. EGCG inhibited expression of IL-1β, IL-6, and TNF-α. Furthermore, EGCG rescued cell proliferation ability, increased SOD activity and reduced ROS expression under hypoxia.In vivo, reduced inflammatory cell accumulation was observed in the coronal pulp in the EGCG group, while in the control group, diffuse inflammatory cells were observed in the radicular pulp.

CONCLUSION

EGCG had no obvious effects on calcified nodule formation but significantly inhibited the inflammatory response of hDPSCs and inhibited apoptosis of hDPSCs caused by hypoxia injury. In vivo, EGCG exerts inhibitory effects on pulp tissue inflammation.

A Review on the Biocompatibility of PMMA-Based Dental Materials for Interim Prosthetic Restorations with a Glimpse into their Modern Manufacturing Techniques

This paper's primary aim is to outline relevant aspects regarding the biocompatibility of PMMA (poly(methyl methacrylate))-based materials used for obtaining interim prosthetic restorations, such as the interaction with oral epithelial cells, fibroblasts or dental pulp cells, the salivary oxidative stress response, and monomer release. Additionally, the oral environment's biochemical response to modern interim dental materials containing PMMA (obtained via subtractive or additive methods) is highlighted in this review. The studies included in this paper confirmed that PMMA-based materials interact in a complex way with the oral environment, and therefore, different concerns about the possible adverse oral effects caused by these materials were analyzed. Adjacent to these aspects, the present work describes several advantages of PMMA-based dental materials. Moreover, the paper underlines that recent scientific studies ascertain that the modern techniques used for obtaining interim prosthetic materials, milled PMMA, and 3D (three-dimensional) printed resins, have distinctive advantages compared to the conventional ones. However, considering the limited number of studies focusing on the chemical composition and biocompatibility of these modern interim prosthetic materials, especially for the 3D printed ones, more aspects regarding their interaction with the oral environment need to be further investigated.

N-Acetyl Cysteine as a Novel Polymethyl Methacrylate Resin Component: Protection against Cell Apoptosis and Genotoxicity

The present study investigated the antiapoptotic and antigenotoxic capabilities of N-acetyl cysteine- (NAC-) containing polymethyl methacrylate (PMMA) resin. An in vitro Transwell insert model was used to mimic the clinical provisional restorations placed on vital teeth. Various parameters associated with cell apoptosis and genotoxicity were investigated to obtain a deeper insight into the underlying mechanisms. The exposure of human dental pulp cell (hDPC) cultures to the PMMA resin (Unifast Trad™) resulted in a rapid increase in reactive oxygen species (ROS) level beginning at 1 h, which was followed by time-dependent cell detachment and overt death. The formation of γ-H2AX and cell cycle G1 phase arrest indicated that oxidative DNA damage occurred as a result of the interactions between DNA bases and ROS, beyond the capacities of cellular redox regulation. Such oxidative DNA damage triggers the activation of p53 via the ataxia telangiectasia mutated (ATM) signaling pathway and the induction of intrinsic mitochondrial apoptosis. Oxidative stress, cell apoptosis, and DNA damage induced by the PMMA resin were recovered to almost the level of untreated controls by the incorporation of NAC. The results indicate that the PMMA resin induced the intrinsic mitochondrial apoptosis as a consequence of p53 activation via the ATM pathway in response to oxidative DNA damage. More importantly, the incorporation of NAC as a novel component into the Unifast Trad™ PMMA resin offers protective effects against cell apoptosis and genotoxicity. This procedure represents a beneficial strategy for developing more biocompatible PMMA-based resin materials.

Protection against HEMA-Induced Mitochondrial Injury In Vitro by Nrf2 Activation

Dental resin monomers such as 2-hydroxyethyl methacrylate (HEMA) disturb vital cell functions and induce mitochondrial intrinsic apoptosis via generation of oxidative stress. Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates the gene expression of antioxidative enzymes and plays a crucial role in the maintenance of cellular redox equilibrium and mitochondrial homeostasis. The present study investigated the functional significance of Nrf2 in cellular response toward HEMA. It was found that HEMA stimulation promoted nuclear translocation of Nrf2 and increased Nrf2 and heme oxygenase-1 (HO-1) expression, which was further enhanced by Nrf2 activator tert-butylhydroquinone (tBHQ), but suppressed by Nrf2 inhibitor ML385. Pretreatment of primary human dental pulp cells (hDPCs) with tBHQ protected the cells from HEMA-induced oxidative injury (increased reactive oxygen species production and apoptosis) and mitochondrial impairment (morphological alterations, decreased ATP production, suppressed oxidative phosphorylation activity, depolarization of mitochondrial membrane potential, and disrupted electron transport chain). In contrast, pretreatment with ML385 increased cell sensitivity to these injurious processes. This protective effect on mitochondria could be related to peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α)/nuclear respiratory factor 1 (NRF1) pathway. These results contribute to the understanding of the function of Nrf2 and the development of novel therapies to counteract the adverse effects of dental resin monomers.

Sources of free radicals and oxidative stress in the oral cavity

OBJECTIVE

An oral cavity is a place especially susceptible to oxidative damage. It is subjected to many environmental pro-oxidative factors or factors that have the ability to generate reactive oxygen species (ROS). The aim of this article is to present the main sources of ROS and oxidative stress in the oral environment.

DESIGN

A literature search was performed using the PubMed and Google Scholar databases.

RESULTS

One of the most important ROS sources in the oral cavity is periodontal inflammation. Other sources of ROS include: xenobiotics (ethanol, cigarette smoke, drugs), food (high-fat diet, high-protein diet, acrolein), dental treatment (ozone, ultrasound, non-thermal plasma, laser light, ultraviolet light), and dental materials (fluorides, dental composites, fixed orthodontic appliances, and titanium fixations). It has been shown that excessive production of ROS in the oral cavity may cause oxidative stress and oxidative damage to cellular DNA, lipids, and proteins, thus predisposing to many oral and systemic diseases.

CONCLUSIONS

Recognition of the exogenous sources of ROS and limitation of exposure to the ROS generating factors can be one of the prophylactic measures preventing oral and systemic diseases. It is suggested that antioxidant supplementation may be helpful in people exposed to excessive production of ROS in the oral cavity system.

Biological Activities and Potential Oral Applications of N-Acetylcysteine: Progress and Prospects

N-Acetylcysteine (NAC), a cysteine prodrug and glutathione (GSH) precursor, has been used for several decades in clinical therapeutic practices as a mucolytic agent and for the treatment of disorders associated with GSH deficiency. Other therapeutic activities of NAC include inhibition of inflammation/NF-κB signaling and expression of proinflammatory cytokines. N-Acetylcysteine is also a nonantibiotic compound possessing antimicrobial property and exerts anticarcinogenic and antimutagenic effects against certain types of cancer. Recently, studies describing potentially important biological and pharmacological activities of NAC have stimulated interests in using NAC-based therapeutics for oral health care. The present review focused on the biological activities of NAC and its potential oral applications. The potential side effects of NAC and formulations for drug delivery were also discussed, with the intent of advancing NAC-associated treatment modalities in oral medicine.

Protective role of epigallocatechin-3-gallate on arsenic induced testicular toxicity in Swiss albino mice

Arsenic, often referred to as the king of poisons is carcinogenic in humans and animals. It affects multiorgan systems including reproduction. The present study was undertaken to explore the protective role of green tea compound, epigallocatechin-3-gallate (EGCG) on arsenic induced testicular toxicity in Swiss albino mice. Thirty two adult male mice were randomly assigned to four groups (n=8). Group I served as control without test chemical. The group II received arsenic (200ppm) through drinking water, group III received only EGCG (20mg/kgb.wt., intraperitoneally, alternate days) and group IV was administered arsenic+EGCG for 40days. Factorial experimental design was employed to assess the treatment effect. The EGCG restored arsenic induced decrements in epididymal sperm concentration, kinematic attributes (total motility, rapid, progressive motile, fast progressive, VSL, VAP, VCL, BCF, LIN, WOB, STR and Type A), structutal membrane integrity, functional membrane integrity and mitochondrial membrane potential. As evidenced by the histoarchitectural studies, the EGCG reversed the deleterious effects of arsenic on testicular malondialdehyde (p<0.05) levels, reduced glutathione, antioxidative enzymes and spermatogenesis. Overall, the results suggest that EGCG reduces the testicular oxidative stress induced by arsenic poisoning and thereby protect the reproductive system.

Fabrication and Characterization of Carbon Fiber-Reinforced Nano-Hydroxyapatite/Polyamide46 Biocomposite for Bone Substitute

Background

Ideal bone repair material should be of good biocompatibility and high bioactivity. Besides, their mechanical properties should be equivalent to those of natural bone. The objective of this study was to fabricate a novel biocomposite suitable for load-bearing bone defect repair.

Material/Methods

A novel biocomposite composed of carbon fiber, hydroxyapatite and polyamide46 (CF/HA/PA46) was fabricated, and its mechanical performances and preliminary cell responses were evaluated to explore its feasibility for load-bearing bone defect repair.

Results

The resultant CF/HA/PA46 biocomposite showed a bending strength of 159–223 MPa, a tensile strength of 127–199 MPa and a tensile modulus of 7.7–10.8 GPa, when the CF content was 5–20% (mass fraction) in biocomposite. The MG63 cells, showing an osteogenic phenotype, were well adhered and spread on the surface of the CF/HA/PA46 biocomposite. Moreover, the cells vitality and differentiation on the CF/HA/PA46 biocomposite surface were obviously increased during the culture time and there was no significant difference between the CF/HA/PA46 biocomposite and HA/PA (as control) at all the experimental time (P>0.05).

Conclusions

The addition of CF into HA/PA46 composite manifest improved the mechanical performances and showed favorable effects on biocompatibility of MG63 cells. The obtained biocomposite has high potential for bone repair in load-bearing sites.

Quaternary ammonium-based biomedical materials: State-of-the-art, toxicological aspects and antimicrobial resistance

Microbial infections affect humans worldwide. Many quaternary ammonium compounds have been synthesized that are not only antibacterial, but also possess antifungal, antiviral and anti-matrix metalloproteinase capabilities. Incorporation of quaternary ammonium moieties into polymers represents one of the most promising strategies for preparation of antimicrobial biomaterials. Various polymerization techniques have been employed to prepare antimicrobial surfaces with quaternary ammonium functionalities; in particular, syntheses involving controlled radical polymerization techniques enable precise control over macromolecular structure, order and functionality. Although recent publications report exciting advances in the biomedical field, some of these technological developments have also been accompanied by potential toxicological and antimicrobial resistance challenges. Recent evidenced-based data on the biomedical applications of antimicrobial quaternary ammonium-containing biomaterials that are based on randomized human clinical trials, the golden standard in contemporary medicinal science, are included in the present review. This should help increase visibility, stimulate debates and spur conversations within a wider scientific community on the implications and plausibility for future developments of quaternary ammonium-based antimicrobial biomaterials.

Effect of an Experimental Direct Pulp-capping Material on the Properties and Osteogenic Differentiation of Human Dental Pulp Stem Cells

Effective pulp-capping materials must have antibacterial properties and induce dentin bridge formation; however, many current materials do not satisfy clinical requirements. Accordingly, the effects of an experiment pulp-capping material (Exp) composed of an antibacterial resin monomer (MAE-DB) and Portland cement (PC) on the viability, adhesion, migration, and differentiation of human dental pulp stem cells (hDPSCs) were examined. Based on a Cell Counting Kit-8 assay, hDPSCs exposed to Exp extracts showed limited viability at 24 and 48 h, but displayed comparable viability to the control at 72 h. hDPSC treatment with Exp extracts enhanced cellular adhesion and migration according to in vitro scratch wound healing and Transwell migration assays. Exp significantly upregulated the expression of osteogenesis-related genes. The hDPSCs cultured with Exp exhibited higher ALP activity and calcium deposition in vitro compared with the control group. The novel material showed comparable cytocompatibility to control cells and promoted the adhesion, migration, and osteogenic differentiation of hDPSCs, indicating excellent biocompatibility. This new direct pulp-capping material containing MAE-DB and PC shows promise as a potential alternative to conventional materials for direct pulp capping.

Methacryloxylethyl Cetyl Ammonium Chloride Induces DNA Damage and Apoptosis in Human Dental Pulp Cells via Generation of Oxidative Stress

The polymerizable antibacterial monomer methacryloxylethyl cetyl ammonium chloride (DMAE-CB) has provided an effective strategy to combat dental caries. However, the application of such material raises the question about the biological safety and the question remains open. The mechanism of this toxic action, however, is not yet clearly understood. The present study aims at providing novel insight into the possible causal link between cellular oxidative stress and DNA damage, as well as apoptosis in human dental pulp cells exposed to DMAE-CB. The enhanced formation of reactive oxygen species and depletion of glutathione, as well as differential changes in activities of superoxide dismutase, glutathione peroxidase, and catalase in DMAE-CB-treated cells indicated oxidative stress. By using substances that can alter GSH synthesis, we found that GSH was the key component in the regulation of cell response towards oxidative stress induced by DMAE-CB. The increase in oxidative stress-sensitive 8-Oxo-2'-deoxyguanosine (8-OHdG) content, formation of γ-H2AX and cell cycle G1 phase arrest indicated that DNA damage occurred as a result of the interaction between DNA base and ROS beyond the capacities of antioxidant mechanisms in cells exposed to DMAE-CB. Such oxidative DNA damage thus triggers the activation of ataxia telangiectasia-mutated (ATM) signaling, the intrinsic apoptotic pathway, and destruction of mitochondrial morphology and function.

N-Acetyl Cysteine Depletes Reactive Oxygen Species and Prevents Dental Monomer-Induced Intrinsic Mitochondrial Apoptosis In Vitro in Human Dental Pulp Cells

Purpose

To investigate the involvement of intrinsic mitochondrial apoptosis in dental monomer-induced cytotoxicity and the influences of N-acetyl cysteine (NAC) on this process.

Methods

Human dental pulp cells (hDPCs) were exposed to several dental monomers in the absence or presence of NAC, and cell viability, intracellular redox balance, morphology and function of mitochondria and key indicators of intrinsic mitochondrial apoptosis were evaluated using various commercial kits.

Results

Dental monomers exerted dose-dependent cytotoxic effects on hDPCs. Concomitant to the over-production of reactive oxygen species (ROS) and depletion of glutathione (GSH), differential changes in activities of superoxide dismutase, glutathione peroxidase, and catalase were detected. Apoptosis, as indicated by positive Annexin V/propidium iodide (PI) staining and activation of caspase-3, was observed after dental monomer treatment. Dental monomers impaired the morphology and function of mitochondria, and induced intrinsic mitochondrial apoptosis in hDPCs via up-regulation of p53, Bax and cleaved caspase-3, and down-regulation of Bcl-2. NAC restored cell viability, relieved oxidative stress and blocked the apoptotic effects of dental monomers.

Conclusions

Dental monomers induced oxidative stress and mitochondrial intrinsic apoptosis in hDPCs. NAC could reduce the oxidative stress and thus protect hDPCs against dental monomer-induced apoptosis.