Comparative radical production and cytotoxicity induced by camphorquinone and 9-fluorenone against human pulp fibroblasts

Cytotoxicity of Methacrylate Dental Resins to Human Gingival Fibroblasts

This study aimed to assess the acute and delayed cytotoxicity of three, popular light-cured methacrylate-based restorative resins (MRs): Charisma (C), Estelite (E), and Filtek (F), to human gingival fibroblasts in culture. Cells were grown for up to 24 h with light-cured (or pre-cured) resins. We evaluated resin cytotoxicity, redox imbalance, necrosis/apoptosis, miR-9, and heat shock protein 70 (HSP70). The role of resin-induced oxidative stress (damage) in HSP70-response (repair) was assessed using binary fluorescence labeling. All MRs decreased viable cell numbers and cell proliferation and damaged cell membranes, and their 24 h-delayed toxicity was lower (C), higher (F), or similar (E) to that induced by freshly-cured resins. Cell membrane damage induced by C and E decreased with time, while F produced a linear increase. All resins generated intracellular oxidative stress with the predominant necrotic outcome, and produced heterogeneous responses in miR-9 and HSP70. The double fluorescence (damage/repair) experiments pointed to common features of E and F but not C. In the subset of cells, the binary response induced by E and F was different from C, similar to each other, and positively interrelated. Experimental data show that selective MR cytotoxicity should be taken into account when considering repetitive use or massive reconstruction.

Human dental pulp stem cell responses to different dental pulp capping materials

Background

Direct pulp capping is a vital pulp therapy for a pin-point dental pulp exposure. Applying a pulp capping material leads to the formation of a dentin bridge and protects pulp vitality. The aim of this study was to compare the effects of four dental materials, DyCal^®, ProRoot^® MTA, Biodentine™, and TheraCal™ LC in vitro.

Methods

Human dental pulp stem cells (hDPs) were isolated and characterized. Extraction medium was prepared from the different pulp capping materials. The hDP cytotoxicity, proliferation, and migration were examined. The odonto/osteogenic differentiation was determined by alkaline phosphatase, Von Kossa, and alizarin red s staining. Osteogenic marker gene expression was evaluated using real-time polymerase chain reaction.

Results

ProRoot^® MTA and Biodentine™ generated less cytotoxicity than DyCal^® and TheraCal™ LC, which were highly toxic. The hDPs proliferated when cultured with the ProRoot^® MTA and Biodentine™ extraction media. The ProRoot^® MTA and Biodentine™ extraction medium induced greater cell attachment and spreading. Moreover, the hDPs cultured in the ProRoot^® MTA or Biodentine™ extraction medium migrated in a similar manner to those in serum-free medium, while a marked reduction in cell migration was observed in the cells cultured in DyCal^® and TheraCal™ LC extraction media. Improved mineralization was detected in hDPs maintained in ProRoot^® MTA or Biodentine™ extraction medium compared with those in serum-free medium.

Conclusion

This study demonstrates the favorable in vitro biocompatibility and bioactive properties of ProRoot^® MTA and Biodentine™ on hDPs, suggesting their superior regenerative potential compared with DyCal^® and TheraCal™.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01544-w.

Biological and mechanical characterization of commercial and experimental periodontal surgical dressings

The objective of this study was to evaluate the biocompatibility and mechanical properties of two commercially available and one experimental periodontal dressing materials. The cytotoxicity of Periobond ® , Barricaid ® and one experimental periodontal dressing based on Exothane ® 8 monomer was tested on 3T3/NIH mouse fibroblast. Genotoxicity was assessed by micronuclei formation, and cell alterations were analyzed using light microscopy. Both biological assays were performed using the eluate obtained from specimens after 24, 72, or 168 hours of incubation. Mechanical characterization was assessed through the ultimate tensile strength and the water sorption and solubility tests. The significance level of α = 0.05 was used for all statistical analyses. All the materials promoted a cell viability lower than 60% in all evaluated times. In general, the cell viability was significantly reduced after 72 and 168h of specimens' incubation. Considering the factor material, there were not statistical differences in the cell viability (p = 0.156). The genotoxicity was not statistically significant among the groups in the different periods of time (p > 0.05). Differences in the ultimate tensile strength values were not statistically significant different among the groups (p = 0.125). Periobond ® showed the higher water sorption values (p < 0.001). Regarding solubility, there were no statistical differences between the groups (p = 0.098). All the periodontal dressing materials evaluated in this study exerted a cytotoxic effect against mouse fibroblasts, and their toxicity became more evident over time. Among the materials evaluated, the experimental light-cure type has shown overall similar properties to the commercial references.

Cytocompatibility and bioactive properties of the new dual-curing resin-modified calcium silicate-based material for vital pulp therapy

OBJECTIVE

The aim of the present study was to evaluate the in vitro biocompatibility of Theracal PT, Theracal LC, and MTA Angelus, considered as bioactive materials used for vital pulp treatment, on human dental pulp stem cells (hDPSCs).

MATERIALS AND METHODS

Human dental pulp stem cells (hDPSCs) were isolated from third molars, and material eluates were prepared (undiluted, 1:2, and 1:4 ratios). The hDPSC cytotoxicity, adhesion, morphology, viability, and cell migration were assessed. The mineralization nodule formation was determined by Alizarin red S staining (ARS). The odonto/osteogenic differentiation potential was assessed by osteo/odontogenic marker expression real-time qPCR. The chemical composition and ion release of the vital pulp materials were determined by energy dispersive X-ray (EDX) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. Statistical differences were assessed by ANOVA and Tukey's test (p < 0.05).

RESULTS

The three vital pulp materials showed variable levels of calcium, tungsten, silicon, and zirconium release and in their chemical composition. Cytocompatibility assays revealed higher hDPSC viability and migration rates when treated with Theracal PT than with Theracal LC. The lowest cell adhesion and spreading were observed in all Theracal LC-treated groups, whereas the highest were observed when treated with MTA. Theracal PT and MTA promoted the upregulation of DSPP and RUNX2 gene expression (p < 0.05). After 21 days, both MTA Angelus and Theracal PT-treated cells exhibited a significantly higher mineralized nodule formation than the negative control (p < 0.05).

CONCLUSIONS

This study demonstrates the favorable in vitro cytocompatibility and bioactive properties of the recently introduced Theracal PT and the well-established MTA Angelus on hDPSCs, as opposed to Theracal LC. More studies, including in vivo animal testing are suggested before these new formulations might be used in the clinical setting.

CLINICAL RELEVANCE

Theracal PT is a new material that could be clinically suitable for vital pulp therapy. Further studies considering its biocompatibility and bioactivity are necessary.

Cytotoxic and genotoxic potential of the type I photoinitiators BAPO and TPO on human oral keratinocytes and V79 fibroblasts

OBJECTIVES

Phenylbis(acyl) phosphine oxide (BAPO) and diphenyl(acyl) phosphine oxide (TPO) are alternative photoinitiators to camphorquinone (CQ) in dental resinous materials. Aim of this study was to investigate their cytotoxic/genotoxic potential in human oral keratinocytes (OKF6/Tert2) and Chinese hamster lung fibroblasts (V79) in comparison to CQ.

METHODS

Cells were exposed to different concentrations of BAPO and TPO (1-50μM). Cytotoxicity was evaluated using H33342 and MTT assay, cell proliferation by BrdU proliferation assay and microscopy. Effects on cellular redox homeostasis were assessed by detecting intracellular levels of reactive oxygen/nitrogen species (ROS/RNS) using the DCFH₂ assay and by quantification of mRNA expression of oxidatively regulated, cyto-protective enzymes. Genotoxic potential was determined by use of micronucleus (MN) assay.

RESULTS

BAPO and TPO induced a concentration-dependent decrease of cell number. BAPO and TPO showed 50- to 250-fold higher cytotoxicity than CQ. In contrast to CQ, both photoinitiators revealed no increase of intracellular ROS/RNS. However, BAPO (10μM) at least significantly induced mRNA-expression of redox-regulated proteins after 24h similar to 2.5mM CQ. Additionally, BAPO significantly raised the number of micronuclei, but only in V79 cells (10μM: 12±1, 2.5mM CQ: 15±1, medium control: 6±3). However, it also significantly decreased proliferation of these cells (10μM BAPO: 19.8%±7.3% compared to controls).

SIGNIFICANCE

BAPO and TPO revealed concentration-dependent cytotoxic effects in human oral keratinocytes and V79 cells. However, in contrast to CQ, no generation of intracellular ROS/RNS was found. Only BAPO induced genotoxicity in V79 cells.

Genotoxic and mutagenic potential of camphorquinone in L5178/TK+/- mouse lymphoma cells

OBJECTIVES

Camphorquinone (CQ) is the most important photoinitiator used in dental composite resins. Sparse data indicate a mutagenic potential of CQ. Therefore, it was aim of this study to evaluate the cytotoxicity, genotoxicity, and mutagenicity of CQ in L5178Y TK^+/- mouse lymphoma cells.

METHODS

L5178Y/TK^+/- cells were exposed to different concentrations of non-irradiated CQ (0.25-2.5mM). Cytotoxicity was evaluated by propidium iodide assay, determination of suspension growth rate, relative total growth and the mitotic index. Intracellular levels of reactive oxygen/nitrogen species (ROS/RNS) were quantified by 2',7'-dichlorofluoresceine diacetate (DCFH-DA). Early induction of DNA strand breaks and oxidative DNA base lesions was assessed using the 8-hydroxyguanine DNA-glycosylase 1 (hOGG1)-modified alkaline comet assay, whereas mutagenicity of CQ was determined in the mouse lymphoma TK assay (MLA), according to OECD Guideline No. 490.

RESULTS

CQ (0.5-2.5mM) induced concentration- and time-dependent inhibition of cell growth associated with increased ROS/RNS production, amounting to 2342%±1108% of controls after 90min at 2.5mM. Additionally, CQ concentration-dependently caused direct DNA-damage, i.e. formation of DNA strand breaks and 8-hydroxy-2'-deoxyguanosine. Whereas the MLA indicated lack of mutagenicity of CQ after a 4h of treatment, CQ concentration-dependently increased total mutant frequency (MF) after 24h (about 2-fold at 2.5mM). But, based on the global evaluation factor concept, increase in MF did not reach biologically relevance.

SIGNIFICANCE

CQ induced concentration-dependent, cytotoxic and genotoxic effects in L5178Y/TK^+/- cells, most likely due to oxidative stress, but without mediating obvious biological relevant mutagenicity.

Biocompatibility and bond degradation of poly-acrylic acid coated copper iodide-adhesives

OBJECTIVE

To investigate the effect of poly-acrylic acid (PAA) copper iodide (CuI) adhesives on bond degradation, tensile strength, and biocompatibility.

METHODS

PAA-CuI particles were incorporated into Optibond XTR, Optibond Solo and XP Bond in 0.1 and 0.5mg/ml. Clearfil SE Protect, an MDPB-containing adhesive, was used as control. The adhesives were applied to human dentin, polymerized and restored with composite in 2mm-increments. Resin-dentin beams (0.9±0.1mm²) were evaluated for micro-tensile bond strength after 24h, 6 months and 1year. Hourglass specimens (10×2×1mm) were evaluated for ultimate tensile strength (UTS). Cell metabolic function of human gingival fibroblast cells exposed to adhesive discs (8×1mm) was assessed with MTT assay. Copper release from adhesive discs (5×1mm) was evaluated with UV-vis spectrophotometer after immersion in 0.9% NaCl for 1, 3, 5, 7, 10, 14, 21 and 30 days. SEM, EDX and XRF were conducted for microstructure characterization.

RESULTS

XTR and Solo did not show degradation when modified with PAA-CuI regardless of the concentration. The UTS for adhesives containing PAA-CuI remained unaltered relative to the controls. The percent viable cells were reduced for Solo 0.5mg/ml and XP 0.1 or 0.5mg/ml PAA-CuI. XP demonstrated the highest ion release. For all groups, the highest release was observed at days 1 and 14.

SIGNIFICANCE

PAA-CuI particles prevented the bond degradation of XTR and Solo after 1year without an effect on the UTS for any adhesive. Cell viability was affected for some adhesives. A similar pattern of copper release was demonstrated for all adhesives.

Genotoxic effects of camphorquinone and DMT on human oral and intestinal cells

OBJECTIVE

Released components of oral biomaterials can leach into the oral cavity and may subsequently reach the gastrointestinal tract. Camphorquinone (CQ) is the most common used photoinitiator in resinous restorative materials and is often combined with the co-initiator N,N-dimethyl-p-toluidine (DMT). It has been shown that CQ exerts cytotoxic effects, at least partially due to the generation of reactive oxygen species (ROS). Objective of this study was to examine the cytotoxic and genotoxic potential of CQ in human oral keratinocytes (OKF6/TERT2) and immortalized epithelial colorectal adenocarcinoma cells (Caco-2). Furthermore, the effects of visible-light irradiation and the co-initiator DMT were investigated as well as the generation of ROS, the potential protective effect of glutathione (GSH) and a recovery period of CQ-treated Caco-2 cells.

METHODS

The alkaline comet assay was used to determine DNA damage. Additionally, an enzyme modified comet assay was applied, which detects 7,8-dihydro-8-oxoguanine (8-oxoguanine), a reliable marker for oxidative stress.

RESULTS

Our data revealed that high concentrations of CQ induced DNA lesions in OKF6/TERT2 cells. This DNA damage is at least partly caused by the generation of 8-oxoguanine. In addition, CQ and DMT increased ROS formation and induced DNA damage in Caco-2 cells. CQ-treatment resulted in generation of 8-oxoguanine. The antioxidant GSH efficiently prevented CQ-associated DNA damage. Furthermore, a recovery following CQ-treatment significantly reduced DNA damage.

SIGNIFICANCE

We conclude that CQ-induced DNA damage is caused by oxidative stress in oral and intestinal cells. These lesions can be prevented and possibly repaired by GSH-treatment and recovery of cells after the photoinitiator is removed from cultures.

Evaluation of cell responses toward adhesives with different photoinitiating systems

OBJECTIVES

The photoinitiator diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) is more reactive than a camphorquinone/amine (CQ) system, and TPO-based adhesives obtained a higher degree of conversion (DC) with fewer leached monomers. The hypothesis tested here is that a TPO-based adhesive is less toxic than a CQ-based adhesive.

METHODS

A CQ-based adhesive (SBU-CQ) (Scotchbond Universal, 3M ESPE) and its experimental counterpart with TPO (SBU-TPO) were tested for cytotoxicity in human pulp-derived cells (tHPC). Oxidative stress was analyzed by the generation of reactive oxygen species (ROS) and by the expression of antioxidant enzymes. A dentin barrier test (DBT) was used to evaluate cell viability in simulated clinical circumstances.

RESULTS

Unpolymerized SBU-TPO was significantly more toxic than SBU-CQ after a 24h exposure, and TPO alone (EC50=0.06mM) was more cytotoxic than CQ (EC50=0.88mM), EDMAB (EC50=0.68mM) or CQ/EDMAB (EC50=0.50mM). Cultures preincubated with BSO (l-buthionine sulfoximine), an inhibitor of glutathione synthesis, indicated a minor role of glutathione in cytotoxic responses toward the adhesives. Although the generation of ROS was not detected, a differential expression of enzymatic antioxidants revealed that cells exposed to unpolymerized SBU-TPO or SBU-CQ are subject to oxidative stress. Polymerized SBU-TPO was more cytotoxic than SBU-CQ under specific experimental conditions only, but no cytotoxicity was detected in a DBT with a 200μm dentin barrier.

SIGNIFICANCE

Not only DC and monomer-release determine the biocompatibility of adhesives, but also the cytotoxicity of the (photo-)initiator should be taken into account. Addition of TPO rendered a universal adhesive more toxic compared to CQ; however, this effect could be annulled by a thin dentin barrier.

Camphorquinone inhibits odontogenic differentiation of dental pulp cells and triggers release of inflammatory cytokines

INTRODUCTION

Camphorquinone (CQ) is a photoinitiator that triggers polymerization of light-curing materials such as dental adhesives and composites. CQ does not become a part of the polymer network, suggesting that CQ can be leached out into surrounding environment including dental pulp and exert adversary effects on tissues. In order to understand the mechanisms of CQ-induced side effects, we investigated the effect of CQ on cell viability, cytokine secretion, and odontogenic differentiation of dental pulp stem cells in vitro.

METHODS

Cell viability was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay after CQ exposure. Western blotting was performed for p16(INK4A), p21(WAF1), and p53. Secretory cytokines were evaluated using the membrane-enzyme-linked immunosorbent assay as well as conventional and quantitative reverse-transcription polymerase chain reaction. The effects of CQ on odontogenic differentiation were evaluated using alkaline phosphatase and alizarin red S staining methods.

RESULTS

CQ treatment suppressed the proliferation of DPSCs and induced the expression of p16(INK4A), p21(WAF1), and p53. Levels of proinflammatory cytokines (eg, interleukin 6, interleukin 8, and matrix metalloproteinase-3 [MMP3]) were increased by CQ treatment. CQ also inhibited odontogenic differentiation and mineralization capacities of DPSC and MC3T3-E1 cells.

CONCLUSIONS

Our study showed that CQ may trigger pulpal inflammation by inducing proinflammatory cytokine production from the pulpal cells and may impair odontogenic differentiation of dental pulp cells, resulting in pulpal irritation and inflammation.

Radical-scavenging activity of dietary phytophenols in combination with co-antioxidants using the induction period method

The radical-scavenging activity of dietary phytophenols has been investigated by many researches due to their antioxidant, anti-inflammatory and anticancer property but the radical-scavenging effect of 2-phytophenol and the phytophenol:co-antioxidants, vitamin C and thiol combination under nearly anaerobic conditions still remains unknown. The radical-scavenging activity for seventeen phytophenols and for six synthetic phenols (positive controls) was investigated using the induction period method in the polymerization of methyl methacrylates (MMA) initiated by thermal decomposition of benzoyl peroxide (BPO) by monitoring differential scanning calorimetery (DSC). The k_inh for the phytophenols was likely with the range 0.5 × 10³ M⁻¹s⁻¹−2.2 × 10³ M⁻¹s⁻¹, whereas that for synthetic phenols, hydroquinone and galvinoxyl, was with the range 7 × 10³ M⁻¹s⁻¹−8 × 10³ M⁻¹s⁻¹. Also, the additive scavenging effect of the (−)-epigallocatechin (EGC):(−)-epicatechin (EC) and the (+)-catechin:epicatechin (EC) combination was observed at 1:1 molar ratio, whereas that of the EC:quercetin combination showed the cancel (prooxidative) effect. Furthermore, the EGC:ASDB (L-ascorbyl 2,6-dibutylate) or 2-ME (2-mercaptoethanol) combination showed the prooxidative effect. Such enhancement of prooxidation in the combination may increase their toxic effects due to their cooxidation. Also, the synergic, additive or cancel effects of the flavonoid:vitamins E combination on the induction period in the BPO (a PhCOO* radical) and 2,2′-azobisisobutyronitrile (AIBN, an R* radical) systems are discussed.

Cytotoxicity of dentine bonding agents on human pulp cells is related to intracellular glutathione levels

AIM

To evaluate ex vivo the mechanisms of cytotoxicity of dentine bonding agents in human pulp cells in vitro.

METHODOLOGY

Human pulp cells were obtained from impacted third molars with informed consent and then cultured using an explant technique. Set specimens from Clearfil SE Bond (CB), Prime & Bond 2.1 (PB), and Single Bond (SB) were eluted with culture medium. Cytotoxicity was judged using an assay of tetrazolium bromide reduction. To determine whether glutathione (GSH) levels were important in the cytotoxicity of dentine bonding agents, cells were pretreated with 2-oxothiazolidine-4-carboxylic acid (OTZ) to boost GSH levels or buthionine sulfoximine (BSO) to deplete GSH. Three replicates of each dentine bonding agents were performed in each test. All assays were repeated three times to ensure reproducibility. Statistical analysis was by one-way analysis of variance (anova). Tests of differences of the treatments were analysed by Duncan's test.

RESULTS

Clearfil SE Bond, PB, and SB were cytotoxic to pulp cells in a concentration-dependent manner (P<0.05). The cytotoxicity was upregulated by dentine bonding agents in the following order: PB>SB>CB. Addition of OTZ extracellularly protected the pulp cells from dentine bonding agents-induced cytotoxicity (P<0.05). Addition of BSO enhanced pulp cell death on dentine bonding agents-induced cytotoxicity (P<0.05).

CONCLUSIONS

Dentine bonding agents have significant potential for pulpal toxicity. GSH depletion could be the mechanism for dentine bonding agents-induced cytotoxicity.

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.

Effects of visible light-irradiated camphorquinone and 9-fluorenone on murine oral mucosa

The purpose of this study was to evaluate the histopathological effects of camphorquinone (CQ) and 9-fluorenone (9F) with or without visible light (VL) irradiation on the oral mucous membranes of mice. VL irradiation resulted in a higher degree of tissue damage after CQ or 9F application, particularly the latter. Necrosis and apoptosis were responsible for the tissue damage after application of either agent in the presence of VL irradiation.

Protective effects of antioxidants on micronuclei induced by irradiated 9-fluorenone/N,N-dimethyl-p-toluidine in CHO cells

9-Fluorenone (9F), the aromatic photosensitizer, is widely used as an initiator in visible-light (VL) cured resin systems. There is growing concern that 9F may produce genetic damage by inducing mutation. In this study, 9F in the presence or absence of reducing agent N,N-dimethyl-p-toluidine (DMT) with or without VL irradiation was analyzed for the induction of chromosomal aberrations indicated by micronuclei (MN) induced in CHO cells. Our data demonstrated that a dose-related increase in the frequency of MN and prolonged cell cycles in 9F with or without DMT in the presence or absence of VL irradiation (p < 0.05). The rank orders with respect to genotoxicity and cytotoxicity were found to be as follows: 9F/DMT +VL > 9F/DMT = 9F + VL > 9F. To determine whether oxidative stress could modulate MN induced by 9F/DMT with or without VL irradiation in CHO cells, cells were pretreated with N-acetyl-L-cysteine (NAC), ascorbic acid, and alpha-tocopherol. The pretreatment with antioxidants could diminish not only the prolonged cell cycle but also the decreased frequency of MN which is induced by 9F with or without DMT in the presence or absence of VL irradiation in CHO cells (p < 0.05). Our findings provide the evidences for the induction of MN by 9F in the presence or absence of DMT with or without VL irradiation in CHO cells, indicating clastogenic activity of 9F/DMT in vitro. These antioxidants act as the antagonists against the genotoxicity and cytotoxicity of 9F/DMT. Thus, leaching photoinitiator and reducing agent might be contributing the sources of oxidative stress.

Protective effects of antioxidants on micronuclei induced by camphorquinone/N,N-dimethyl-p-toluidine employing in vitro mammalian test system

Camphorquinone (CQ) is widely used as an initiator in modern visible-light (VL) cured resin systems. CQ is also characterized as a potential allergenic compound. To date, there is growing concern that CQ may produce genetic damage by inducing mutation. In this study, CQ in the presence of reducing agent N,N-dimethyl-p-toluidine (DMT) with or without VL irradiation was analyzed for the induction of chromosomal aberrations indicated by micronuclei (MN) induced in CHO cells. Our data demonstrated that an increase in the numbers of MN was observed with CQ/DMT with or without VL irradiation (p < 0.05). Significant prolongation of cell cycles was observed by the treatment with CQ/DMT with or without VL irradiation (p < 0.05). In addition, VL irradiated CQ/DMT was found to exhibit significantly genotoxic and cytotoxic effects as compared with CQ/DMT alone (p < 0.05). Furthermore, to determine whether oxidative stress could modulate the MN induced by CQ/DMT with or without VL irradiation in CHO cells, cells were pre-treated with various antioxidants 10 mM N-acetyl-L-cysteine (NAC), 2 mM ascorbic acid, and 2 mM alpha-tocopherol. The pre-treatment with antioxidants could antagonize not only the increased MN cells but also the prolonged cell cycle induced by CQ/DMT with or without VL irradiation in CHO cells (p < 0.05). Our findings provide the evidences for the induction of MN by CQ/DMT employing mammalian test system, indicating clastogenic activity of CQ/DMT with or without VL irradiation in vitro. In addition, VL irradiated CQ/DMT exhibits higher genotoxic and cytotoxic effects than CQ/DMT alone. Moreover, NAC, ascorbic acid, and alpha-tocopherol act as the antagonists against the genotoxicity and cytotoxicity of CQ/DMT with or without VL irradiation.

Systematic review of the chemical composition of contemporary dental adhesives

Dental adhesives are designed to bond composite resins to enamel and dentin. Their chemical formulation determines to a large extent their adhesive performance in clinic. Irrespective of the number of bottles, an adhesive system typically contains resin monomers, curing initiators, inhibitors or stabilizers, solvents and sometimes inorganic filler. Each one of these components has a specific function. The aim of this article is to systematically review the ingredients commonly used in current dental adhesives as well as the properties of these ingredients. This paper includes an extensive table with the chemical formulation of contemporary dental adhesives.

Effects of combinations of ROS scavengers on oxidative DNA damage caused by visible-light-activated camphorquinone/N,N-dimethyl-p-toluidine

The objective of this investigation was to analyze whether various combinations of the ROS scavengers glutathione (GSH), N-acetyl-cysteine (NAC), and vitamins C and E decrease DNA damage due to visible-light-irradiated (VL-irradiated) camphorquinone/N,N-dimethyl-p-toluidine (CQ/DMT) compared with individual vitamin C or E. PhiX-174 RF plasmid DNA was used to determine single and double strand breaks as parameters of DNA damage. Individual ROS scavengers and combinations of the antioxidants were added to plasmid DNA treated with VL-irradiated CQ/DMT/Cu (II). After incubation, DNA was loaded into a 1% agarose gel. Following electrophoresis, gels stained with 0.5 microg/mL ethidium bromide were photographed under ultraviolet illumination and analyzed with NIH ImageJ software. Results were evaluated between groups for statistical significance using Student's paired t-test (p < 0.05). Glutathione significantly reduced oxidative DNA damage at all test concentrations when combined with vitamin C or vitamin E. The concentration of damaged DNA observed in the presence of combinations of GSH with vitamin C or vitamin E was significantly lower compared with all other combinations of antioxidants investigated in our study (p < 0.05). In contrast to GSH, NAC was not able to compensate the pro-oxidative effects of vitamin C and vitamin E. Only at a concentration of 2 mM, NAC combined with vitamin C efficiently prevented CQ/DMT/Cu (II)-associated DNA damage. Our data indicate that solely the combinations of GSH with vitamin C or vitamin E significantly reduce the severity of oxidative DNA damage caused by CQ/DMT, whereas NAC may even increase the pro-oxidant activity of vitamin C and vitamin E.

Encapsulation of Chondrocytes in Photopolymerizable Styrenated Gelatin for Cartilage Tissue Engineering

We have developed a photopolymerizable styrenated gelatin that can cross-link through polymerization induced by irradiation with visible light. The purpose of this study was to investigate the feasibility of using photopolymerizable styrenated gelatin as a cell carrier in chondrocyte transplantation. As visible light activates camphorquinone added as a photoinitiator, free radicals induce the polymerization of the gelatin macromer; the styrenated gelatin then becomes cross-linked. Rabbit articular chondrocytes were cultured in styrenated gelatin hydrogels and also in collagen gels as a control. After being cultured in the gels, the cells were collected from both gels and counted. Reverse transcriptase-polymerase chain reaction, histological examination, and quantification of the synthesized glycosaminoglycan were performed. On average, 26% of the embedded cells were collected from the gelatin hydrogel immediately after the crosslinking reaction. The surviving chondrocytes expressed the mRNA of type II collagen and aggrecan core protein and produced a cartilaginous matrix throughout the gelatin after 3 weeks. A slightly insufficient accumulation of the matrix was found in the internal region of the gelatin hydrogels, suggesting that less permeability for nutrients due to the high concentration and closely packed structure resulted in less cell viability. Although some limitations became evident, these results indicate that it may be possible to use photopolymerizable styrenated gelatin as a cell carrier in chondrocyte transplantation.

The effect of N-acetyl-l-cysteine and ascorbic acid on visible-light-irradiated camphorquinone/N,N-dimethyl-p-toluidine-induced oxidative stress in two immortalized cell lines

Recent studies have revealed that visible-light (VL)-irradiated camphorquinone (CQ), in the presence of a tertiary amine (e.g., N,N-dimethyl-p-toluidine, DMT), generates initiating radicals that may indiscriminately react with molecular oxygen forming reactive oxygen species (ROS). In this study, the ability of the antioxidants N-acetyl-l-cysteine (NAC) and ascorbic acid (AA) to reduce intracellular oxidative stress induced by VL-irradiated CQ/DMT or VL-irradiated hydrogen peroxide (H(2)O(2)) was assessed in an immortalized Murine cementoblast cell line (OCCM.30) and an immortalized Murine fibroblast cell line, 3T3-Swiss albino (3T3). Intracellular oxidative stress was measured with the membrane permeable dye, 2',7'-dichlorodihydrofluorescein diacetate (H(2)DCF-DA). VL-irradiated CQ/DMT and VL-irradiated H(2)O(2) each produced significantly (p<0.001) elevated intracellular oxidative levels in both cell types compared to intracellular ROS levels in VL-irradiated untreated cells. OCCM.30 cementoblasts were found to be almost twice as sensitive to VL-irradiated CQ/DMT and VL-irradiated H(2)O(2) treatment compared to 3T3 fibroblasts. Furthermore, 10mm NAC and 10mm AA each eliminated oxidative stress induced by VL-irradiated CQ/DMT and VL-irradiated H(2)O(2) in both cell types. Our results suggest that NAC and AA may effectively reduce or eliminate oxidative stress in cells exposed to VL-irradiated CQ/DMT following polymerization.

Reactive oxygen species generation and its role in the differential cytotoxicity of the arylhydroxylamine metabolites of sulfamethoxazole and dapsone in normal human epidermal keratinocytes

Cutaneous drug reactions (CDR) are responsible for numerous minor to life-threatening complications. Though the exact mechanism for CDR is not completely understood, evidence suggests that bioactivation of drugs to reactive oxygen or nitrogen species is an important factor in the initiation of these reactions. Several CDR-inducing drugs having an arylamine functional group, such as sulfamethoxazole (SMX) and dapsone (DDS), undergo bioactivation to reactive arylhydroxylamine metabolites. These metabolites can generate cellular oxidative stress by forming reactive oxygen species (ROS). Several studies have demonstrated a higher cytotoxicity with DDS hydroxylamine (DDS-NOH) compared to SMX hydroxylamine (SMX-NOH). To investigate the role of differential ROS generation in the higher cytotoxicity of DDS-NOH, hydroxylamine metabolites of SMX and DDS were synthesized and ROS formation by these metabolites determined. DDS-NOH and its analogues/metabolites consistently resulted in higher ROS formation as compared to SMX-NOH. However, comparison of the ROS generation and cytotoxicity of a series of arylhydroxylamine analogues of DDS did not support a simple correlation between ROS generation and cell death. Numerous ROS scavengers were found to reduce metabolite-induced ROS formation, with differences in the potency between the agents. The decrease in DDS-NOH-induced ROS generation in NHEK with ascorbic acid, N-acetylcysteine, Trolox, and melatonin was 87, 86, 44, and 16%, respectively. Similarly, the cytotoxicity and adduct formation of DDS-NOH in NHEK was reduced in the presence of ascorbic acid. In summary, these studies show that arylhydroxylamine metabolites of SMX/DDS induce ROS generation in NHEK, though such generation is not directly related to cytotoxicity.

ROS formation and glutathione levels in human oral fibroblasts exposed to TEGDMA and camphorquinone

Glutathione (GSH) is important for the self-protection of cells against oxidative stress and toxic xenobiotics, whereas reactive oxygen species (ROS) at elevated concentrations may cause detrimental alterations of cell membranes, DNA, and other cellular structures. The present investigation addressed the effects of triethylene-glycoldimethacrylate (TEGDMA) and camphorquinone (CQ) on glutathione metabolism and the formation of ROS in oral cells. Primary human pulp fibroblasts were exposed to various concentrations of TEGDMA and CQ (0.1-5 mM). Subsequently, GSH concentration and ROS formation were analyzed with the use of the monobromobimane assay (GSH) and 2',7'-dichlorofluorescein diacetate (DCFH-DA) (ROS). The endogenous ROS hydrogen peroxide (H2O2) was used as a positive control (0.02-2 mM). TEGDMA significantly decreased GSH at concentrations between 0.5 and 5 mM (p<0.05), but did not elevate ROS levels. Contrary, CQ increased ROS formation at concentrations>or=1 mM, but had only a moderate effect on GSH at the highest test concentration. Hydrogen peroxide increased ROS and simultaneously decreased GSH at concentrations of >or=0.2 mM. These data show that the investigated substances may cause cell damage due to various mechanisms, GSH decrease and/or ROS increase. As a consequence, TEGDMA and CQ released into an aqueous environment from resinous materials might interact, thus generating significant cytotoxic effects even at low concentrations.