Search

Several studies suggest that light in the UVA range (320–400 nm) activates signaling pathways that are anti-inflammatory and antioxidative. These effects have been attributed to Nrf2-mediated upregulation of “phase 2” genes such as heme oxygenase-1 (HO-1) that neutralize oxidative stress and metabolize electrophiles. Proteomics analysis previously had shown that small doses of blue light (400–500 nm) increased levels of peroxiredoxin phase 2 proteins in THP-1 monocytes, which led to our hypothesis that blue light activates Nrf2 signaling and thus may serve as an anti-inflammatory agent. THP-1 monocytes were treated with doses of blue light with and without lipopolysaccharide (LPS) inflammatory challenge. Cell lysates were tested for Nrf2 activation and HO-1 production. Treated cells were assessed for viability/mitochondrial activity via trypan blue exclusion and MTT assay, and secretion of two major pro-inflammatory cytokines, interleukin 8 (IL8) and tumor necrosis factor alpha (TNFα) was measured using ELISA. Blue light activated the phase 2 response in cultured THP-1 cells and was protective against LPS-induced cytotoxicity. Light pre-treatment also significantly reduced cytokine secretion in response to 0.1 μg ml−1 LPS, but had no anti-inflammatory effect at high LPS levels. This study is the first to report these effects using a light source that is approved for routine use on dental patients. Cellular responses to these light energies are worth further study and may provide therapeutic interventions for inflammation.

Previous studies report that microsized monosodium titanates (MSTs) deliver metal ions and species to mammalian cells and bacteria with cell-specific and metal-specific effects. In this study, we explored the use of MST and a new synthesized nanosized monosodium titanate (nMST) to deliver gold(III), cisplatin, or platinum(IV) to two human cell lines with different population doubling times, in vitro. The effect was measured using a fluorescent mitochondrial activity assay (CellTiter-Blue® Assay). This fluorescence assay was implemented to mitigate optical density measurement errors owing to particulate titanate interference and allowed for the studies to be extended to higher titanate concentrations than previously possible. Overall, native MST significantly (p 50 mg/L. Native nMST significantly suppressed the rapidly dividing cell line (by 50%) over untreated cultures, but had no effect on the more slowly dividing cells. For both cell types, increased titanate concentrations resulted in increased effects from delivered metals. However, there was no difference in the effect of metal delivered from micro- versus nano-sized MST. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 254–260, 2015.

Background Titanates are inorganic, amorphous, aqueously insoluble, particulate compounds of titanium, oxygen, hydrogen, and sodium. Two types of titanates, monosodium titanate (MST) and amorphous peroxotitanate (APT), have recently been proposed for use in biological applications where it would be advantageous to locally sequester and deliver metals to alter cellular functions. Purpose In the current study, the ability of MST and APT to suppress the mitochondrial function of a rapidly dividing cell line, OSC2 (oral squamous cell carcinoma) with and without loaded metals [Au(III), Hg(II), Pd(II), Pt(II), Pt(IV), and cis Pt] was determined. Methods Cellular mitochondrial activity of OSC2 cells after 72 hours exposure to titanates or titanate-metal compounds was estimated by measuring succinate dehydrogenase (SDH) activity via the 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Results The results of this study showed that neither native APT nor native MST was biologically neutral to oral squamous cell carcinoma (OSC2). Increasing the concentration of either MST or APT resulted in a statistically significant decrease in SDH activity of OSC2 cells versus untreated cells (40% for APT and 30% for MST). The addition of titanate-metal compounds augmented the effects of APT and MST on OSC2 metabolism, decreasing overall mitochondrial activity compared to controls by 50–70%. However, both titanate types and metal ion species determined the degree to which the SDH activity was suppressed. Conclusion The findings of the current study demonstrate that APT and MST alone significantly suppress the metabolism of a rapidly dividing cell line, an effect that is augmented by specific titanate-metal combinations. These compounds may have potential as unique therapeutic agents.

Introduction Pulp repair is less likely to occur when dentin or pulpal tissue remains infected after caries excavation. Yet there are currently few options to kill residual bacteria without damaging resident cells. The current study has evaluated the effect of 3 blue light–activated chemicals on the viability of lactobacilli, odontoblast-like cells (MDPC-23), undifferentiated pulp cells (OD21), and human embryonic stem cells (hESC H1). Methods Bacteria were incubated for 15 minutes with curcumin, eosin Y, or rose bengal and then irradiated with blue light (240 seconds). Bacteria were labeled with LIVE/DEAD BacLight Bacterial Viability kit, and viability was assessed by fluorescence-activated cell sorting. Cytotoxicity assays were performed on MDPC-23 cells, OD21, and hESC H1 cells grown in 24-well plates and exposed to the same photosensitizer-light combination. After 24 hours, cellular response was measured by using the methyl-thiazol-diphenyl-tetrazolium assay. Results were statistically analyzed by using one-way analysis of variance and Tukey multiple comparison intervals (α = 0.05). Results Bacterial viability was significantly reduced after exposure to different combinations of light and photosensitizers; mitochondrial activity of cultured cells remained unaffected when exposed to the same conditions, suggesting a good therapeutic index in vitro. Conclusions Blue light–mediated disinfection is promising for the development of new treatment strategies designed to promote pulp repair after carious exposure.

Monosodium titanates (MST) are a relatively novel form of particulate titanium dioxide that have been proposed for biological use as metal sorbents or delivery agents, most recently calcium (II). In these roles, the toxicity of the titanate or its metal complex is crucial to its biological utility. The aim of this study was to determine the cytotoxicity of MST and MST-calcium complexes with MC3T3 osteoblast-like cells; MST-Ca(II) complexes could be useful to promote bone formation in various hard tissue applications. MC3T3 cells were exposed to native MST or MST-Ca(II) complexes for 24–72 h. A CellTiter-Blue® assay was employed to assess the metabolic activity of the cells. The results showed that MST and MST-Ca(II) suppressed MC3T3 metabolic activity significantly in a dose-, time-, and cell-density-dependent fashion. MST-Ca(II) suppressed MC3T3 metabolism in a statistically identical manner as native MST at all concentrations. We concluded that MST and MST-Ca(II) are significantly cytotoxic to MC3T3 cells through a mechanism yet unknown; this is a potential problem to the biological utility of these complexes.

Components of dental composites have been implicated as metabolic and oxidative stressors in cells. Antioxidant colloidal platinum nanoparticles (CPtN) could be useful as nanofillers that reduce cellular stress caused during placement and exposure to unpolymerized composite components. Yet, CPtN may have pro- or anti-oxidative properties depending on the chemical environment in which they are used. This study investigated the ability of CPtN to mitigate mitochondrial or oxidative stress induced by camphorquinone (CQ) and dimethylaminoethyl methacrylate (DMAEM), two components of dental composites that initiate light-activated addition polymerization. THP-1 human monocytic cells were exposed to subtoxic concentrations of CQ and DMAEM, then blue light for 0–60 s. Mitochondrial and oxidative stress were estimated 0, 6, or 24 h after irradiation by measuring cellular ATP or GSH levels, respectively. CPtN (0–20 ppm) were added prior to blue light irradiation. Statistically significant effects were determined by ANOVA with Tukey post-hoc analysis (α = 0.05). Light alone did not alter THP-1 activity, but CQ and DMAEM induced 120% increases in cell ATP levels, which was increased further (50%) by CPtN. Blue light irradiation caused a 50% drop in ATP levels, which increased to 75% when CPtN were added. GSH levels were suppressed by CQ/DMAEM and blue light, and CPtN increased suppression by 20–30%. CPtN did not mitigate mitochondrial or oxidative stress in THP-1, but amplified these stresses under the conditions tested. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.

In the biomedical field, palladium has primarily been used as a component of alloys for dental prostheses. However, recent research has shown the utility of palladium alloys for devices such as vascular stents that do not distort magnetic resonance images. Dental palladium alloys may contain minor or major percentages of palladium. As a minor constituent, palladium hardens, strengthens and increases the melting range of alloys. Alloys that contain palladium as the major component also contain copper, gallium and sometimes tin to produce strong alloys with high stiffness and relatively low corrosion rates. All current evidence suggests that palladium alloys are safe, despite fears about harmful effects of low-level corrosion products during biomedical use. Recent evidence suggests that palladium poses fewer biological risks than other elements, such as nickel or silver. Hypersensitivity to palladium alone is rare, but accompanies nickel hypersensitivity 90-100% of the time. The unstable price of palladium continues to influence the use of palladium alloys in biomedicine.

Amorphous peroxotitantes (APT) are insoluble titanium-based particles that bind a variety of metal compounds with high affinity; these particles could be sequestered locally in a solid phase to deliver metal-based drugs. Previous studies have confirmed the 'biodelivery' of metals from metal-APT complexes to fibroblasts, but not monocytes. Our goal in the current study was to use monocytic cytokine secretion to assess delivery of gold or platinum-based compounds from APT to human THP1 monocytes. Cytokine secretion was not triggered by APT alone or metal-APT complexes. In monocytes activated by lipopolysaccharide (LPS), APT alone enhanced or suppressed IL1beta or IL6 secretion, yet TNFalpha secretion was unaffected. Complexes of APT and Au(III) or cis-platin altered LPS-activated IL6 or IL1beta secretion most, TNFalpha least. Our results suggest that the APT deliver metals to monocytes.

Nickel-containing alloys are used in dentistry because of their low cost, but poor corrosion behavior increases their risk of causing adverse biological responses. Intraorally, nickel-containing alloys accumulate bacterial plaque that triggers periodontal inflammation via toxins such as lipopolysaccharide (LPS). Recent evidence suggests that in monocytes, Ni(II) amplifies LPS-induced secretion of several cytokines that mediate periodontal destruction. Thus, we investigated the effects of Ni(II), with or without LPS, on the secretion of a broader array of cytokines from monocytes. We then measured monocytic expression of two proteins, Nrf2 and thioredoxin-1 (Trx1), that influence the regulation of cytokine secretion. Cytokine arrays were used to measure the effects of 0-50 microM Ni(II) on cytokine secretion from human THP1 monocytes, with or without LPS activation. Immunoblots were used to estimate Nrf2 and Trx1 levels. Our results indicate that both Ni(II) alone and Ni(II) with LPS have broad-based effects on cytokine secretion. Ni(II) increased Nrf2 levels by threefold, and LPS amplified the effects of Ni(II) by 10-fold. Trx1 levels did not change under any condition tested. Our results suggest that Ni(II)-induced changes in cytokine secretion by monocytes are diverse and may be influenced by Nrf2 but are not likely influenced by changes in whole-cell Trx1 levels.

Statement of problem Alloys with high nickel content have been increasingly used for dental prostheses. These alloys have excellent hardness, elastic modulus, and strength, yet have high corrosion rates when exposed to chemical or physical forces that are common intraorally. Purpose The purpose of the current study was to measure the susceptibility of several types of nickel-based alloys to brushing abrasion relative to gold- and palladium-based alloys. Material and methods Au-Pt, Au-Pd, Pd-Ag, Ni-Cr, and Ni-Cr-Be dental alloys were brushed with a toothbrush (Oral-B Soft) and toothpaste (Ultrabrite) in a linear brushing machine, then the surface roughness was measured by profilometry (R a , R v , R p ). Specimens (n=4) were brushed for 48 hours in a saline solution (pH 7). The effect of brushing was determined using 2-sided t tests (α=.05), and roughness among alloys postbrushing was compared using 1-way ANOVA with Tukey post hoc analyses (α=.05). Results All polished alloy surfaces (before brushing) had roughnesses of ≤0.1 μm (R a ). The Pd-Ag alloy was the most resistant to brushing. The Ni-Cr-Be alloy abraded the most, with a postbrushing surface roughness of >1 μm (R a ). Ni-Cr alloys without Be had a postbrushing surface roughness of 0.25 μm (R a ). Postbrushing roughness of all other alloys ranged from 0.1-0.25 μm (R a ). R v and R p values behaved similarly to R a values for all alloys. Conclusions Although they have many excellent mechanical properties, Ni-Cr-Be alloys may be prone to degradation from brushing. (J Prosthet Dent 2008;99:455-460)

Objectives Human blood levels of mercury are commonly 10 nM, but may transiently reach 50–75 nM after dental amalgam placement or removal. Controversy persists about the use of mercury because the effects of these ‘trace’ levels of mercury are not clear. Concentrations of mercury ≥5000 nM unequivocally alter redox balance in blood cells including monocytes. In the current study, we tested a hypothesis that concentrations of mercury

AIM: To evaluate the long-term sealing ability of four contemporary endodontic sealers [Pulp Canal Sealer (PCS), AH-Plus, GuttaFlow and Epiphany] using a fluid filtration technique. METHODOLOGY: The palatal roots of 40 human maxillary molar teeth were selected and the root canal was prepared using a crown-down technique (apical size 40, 6% taper). Roots were irrigated with 3% NaOCl, 17% EDTA solution and rinsed with distilled water. Canals were filled with either PCS, AH-Plus, GuttaFlow or Epiphany using a single-cone technique (n = 8). Twenty-four hours after filling, the roots were connected to an automatic flow-recording device (Flodec System) filled with double-distilled water under pressure (0.2 bar) to measure leakage. Flow rates were assessed at 6, 12 or 24-h and after 1-year of storage. RESULTS: None of the materials fully prevented fluid flow. Fluid flow decreased after 6 h and decreased further after 12 h. After 24 h, PCS and AH-Plus allowed significantly more fluid flow than GuttaFlow and Epiphany. After 1 year, PCS allowed significantly more fluid flow than the other materials. No significant changes in leakage occurred between 24 h and 1 year. CONCLUSIONS: GuttaFlow and Epiphany allowed less fluid movement along filled straight roots.

Summary Blue light curing units (wavelengths of 400–500 nm) are a mainstay of restorative dentistry, and several high-intensity light sources have been developed to polymerize resin composites more rapidly. The biological safety of visible light has been assumed, but some reports of adverse biological effects of blue light in non-dental contexts support further evaluation of the biological safety of high-intensity blue light. The current study tested the hypothesis that blue light provokes cell stress responses resulting in the secretion of cytokines or expression of heat-shock proteins (HSP) in monocytes. Human monocytic cells were irradiated with three light sources (quartz-tungsten-halogen, plasma-arc and laser), then cellular proliferation, secretion of the inflammatory cytokine TNFα and induction of HSP72 were measured. Results indicated that although all three light sources significantly inhibited proliferation of monocytes, the secretion of TNFα was not induced following exposure to blue light and was not potentiated with administration of the activator lipopolysaccharide. Similarly, treatment with the plasma-arc light, which caused the largest temperature increase in previous studies, did not induce HSP72. The current results do not support activation of monocytes by blue light as an inflammatory risk factor in dental tissues during curing of composites. However, the results of the current study should be further verified in primary monocytes and an animal model before decisions about clinical risks are made.

Resin composites are widely used in dentistry, and are polymerized in situ using a blue-light activated, free-radical polymerization mechanism. Blue light (400–500nm) is used to activate camphoroquinone (CQ), which decomposes to form free radicals that are stabilized by dimethyl-p-toludine (DMPT). CQ and DMPT are applied near tooth pulpal tissues and are irradiated during restorative procedures, suggesting that pulpal cells are exposed to free radicals. Because glutathione is a major component of the cellular redox management system, we tested the hypothesis that blue light irradiation would shift cellular glutathione redox balance of cells exposed to CQ and DMPT. We also measured NFκB activation, a redox-sensitive transcription factor that regulates inflammatory responses and glutathione synthetic enzyme levels. THP1 human monocytes were exposed to sublethal levels of CQ (0.4 mM) or DMPT (1.0 mM), with or without blue light exposure (25 J/cm2) from a quartz-tungsten-halogen source. The ratio of reduced to oxidized glutathione was measured using as assay based on 5,5′-dithio-bis(2-nitrobenszoic acid). NFκB transactivation was measured by transfection of an NFκB-containing plasmid linked to a luciferase reporter. Our results showed that blue light, CQ, or DMPT alone had no significant effect on cellular glutathione redox balance, but that the combination of these agents induced a marked oxidative bias, and reduced total glutathione levels up to 50%. On the other hand, light, CQ, and DMPT alone or in combination suppressed NFκB transactivation by >70%. Our results suggest that CQ and DMPT pose risks to pulpal tissues with or without blue light irradiation, and that multiple, interacting mechanisms shape the response to these agents. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2007

Nickel is a component of biomedical alloys that is released during corrosion and causes inflammation in tissues by as yet unknown mechanisms. Recent data show that Ni(II) at concentrations of 10-50 microM amplifies lipopolysaccharide-triggered, NFkappaB-mediated cytokine secretion from monocytes. In the current study, we tested the hypothesis that Ni(II) amplifies cytokine secretion by activating the Nrf2 antioxidant pathway rather than by enhancing activity of the NFkappaB signaling pathway. Human THP1 monocytes were exposed to Ni(II) concentrations of 10-30 microM for 6-72 h, then immunoblots of whole-cell lysates or cytosolic and nuclear proteins were used to detect changes in Nrf2 or NFkappaB signaling. Our results show that Ni(II) increased (by 1-2 fold) whole-cell Nrf2 levels and nuclear translocation of Nrf2, and amplified lipopolysaccharide (LPS)-induction of Nrf2 (by 3-5 fold), but had no detectable effect on the initial activation or nuclear translocation of NFkappaB. Because Nrf2 target gene products are known regulators of NFkappaB nuclear activity, our results suggest that Ni(II) may affect cytokine secretion indirectly via modulation of the Nrf2 pathway.

Thioredoxin reductase (TrxR) reduces thioredoxin (Trx), thereby contributing to cellular redox balance, facilitating the synthesis of deoxy-ribose sugars for DNA synthesis, and regulating redox-sensitive gene expression. Auranofin is a gold compound that potently inhibits TrxR. This inhibition is one suspected mechanism of auranofin’s therapeutic benefit in the treatment of rheumatoid arthritis. The use of other gold compounds to treat cancer or inflammatory disease may rely on their ability to inhibit TrxR. In the current study, we tested the hypothesis that a variety of gold compounds may inhibit TrxR. Methods: We exposed rat-TrxR1 to auranofin, gold sodium thiomalate, sodium aurothiosulfate, triphenyl phosphine gold chloride, or gold acetate, and measured TrxR activity ex vivo. We then compared TrxR1 inhibitory levels of gold compounds to those that inhibited mitochondrial activity of THP1 monocytes and OSC2 epithelial cells, estimated by succinate dehydrogenase activity. Results: All gold compounds inhibited TrxR1 at concentrations ranging from 5 to 4000 nM (50% inhibitory concentration). The oxidation state of gold did not correlate with inhibitory potency, but ligand configuration was important. Au(I)-phosphine compounds (triphenyl phosphine gold chloride and auranofin) were the most potent inhibitors of TrxR. All TrxR1 inhibitory concentrations were sublethal to mitochondrial activity in both THP1 and OSC2 cells. Conclusions: Diverse types of gold compounds may be effective inhibitors of TrxR1 at concentrations that do not suppress cellular mitochondrial function. Inhibition may be optimized to some degree by altering the ligand configuration of the compounds. These results support future study of a variety of Au compounds for therapeutic development as inhibitors of TrxR1.

The transcription factor NFkappaB plays a key role in the tissue inflammatory response. Metal ions released into tissues from biomaterials (e.g., Au, Pd, Ni, Hg) are known to alter the binding of NFkappaB proteins to DNA, thereby modulating the effect of NFkappaB on gene activation and, ultimately, the tissue response to biomaterials. Little is known about the effect of these metals on key signaling steps prior to NFkappaB-DNA binding such as transcription factor activation or nuclear translocation, yet these steps are equally important to modulation of the pathway. Oxidative stress is known to alter NFkappaB proteins and is suspected to play a role in metal-induced NFkappaB signaling modulation. Our aim in the current study was to assess the effects of sublethal levels of Ni, Hg, Pd, and Au ions on NFkappaB activation and nuclear translocation in the monocyte, which is acknowledged as an important orchestrator of the biological response to materials and the pathogenesis of chronic disease. Sublethal concentrations of Au(III), Ni(II), Hg(II), and Pd(II) were added to cultures of human THP1 monocytic cells for 72 h. In parallel cultures, lipopolysaccharide (LPS) was added for the last 30 min to activate the monocytic cells. Then cellular cytoplasmic and nuclear proteins were isolated, separated by electrophoresis, and probed for IkappaBalpha degradation (activation) and NFkappaB p65 translocation. Protein levels were digitally quantified and statistically compared. The levels of reactive oxygen species (ROS) in the monocytic cells were measured as a possible mechanism of metal-induced NFkappaB modulation. Only Au(III) activated IkappaBalpha degradation by itself. Au(III) and Pd(II) enhanced LPS-induced IkappaBalpha degradation, but Hg(II) and Ni(II) suppressed it. Au(III), Ni(II), and Pd(II) activated p65 nuclear translocation without LPS, and all but Ni(II) enhanced LPS-induced translocation. Collectively, the results suggest that these metal ions alter activation and translocation of NFkappaB, each in a unique way at unique concentrations. Furthermore, even when these metals had no overt effects on signaling by themselves, all altered activation of signaling by LPS, suggesting that the biological effects of these metals on monocytic function may only be manifest upon activation. None of the metal ions elevated levels of ROS at 72 h, indicating that ROS were probably not direct modulators of the NFkappaB activation or translocation at this late time point.

Titanium-based alloys form a surface reaction layer when cast. This study investigated the effect of the surface reaction layer on the cytotoxicity of novel Ti-based binary alloys. The cytotoxicities of the novel alloys were compared with commercially pure titanium, Ti-6Al-4V and Ti-6Al-7Nb. Cast discs with or without the reaction layer were first tested for cytotoxicity, then for elemental release into cell-culture medium. The elements released into the extracts were measured by means of an inductively coupled plasma atomic emission spectrometer. The commercial and novel binary Ti-based alloys showed no statistically significant cytotoxicity, although some trends were noted for several alloys. The presence of the reaction layer did not significantly alter the cytotoxicity. These favourable biocompatibility results show that these novel alloys have promise for use in dental restorations.

Green tea polyphenols (GTPPs) are considered beneficial to human health, especially as chemopreventive agents. Recently, cytotoxic reactive oxygen species (ROS) were identified in tumor and certain normal cell cultures incubated with high concentrations of the most abundant GTPP, (-)-epigallocatechin-3-gallate (EGCG). If EGCG also provokes the production of ROS in normal epithelial cells, it may preclude the topical use of EGCG at higher doses. The current study examined the oxidative status of normal epithelial, normal salivary gland, and oral carcinoma cells treated with EGCG, using ROS measurement and catalase and superoxide dismutase activity assays. The results demonstrated that high concentrations of EGCG induced oxidative stress only in tumor cells. In contrast, EGCG reduced ROS in normal cells to background levels. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and 5-bromodeoxyuridine incorporation data were also compared between the two oral carcinoma cell lines treated by EGCG, which suggest that a difference in the levels of endogenous catalase activity may play an important role in reducing oxidative stress provoked by EGCG in tumor cells. It is concluded that pathways activated by GTPPs or EGCG in normal epithelial versus tumor cells create different oxidative environments, favoring either normal cell survival or tumor cell destruction. This finding may lead to applications of naturally occurring polyphenols to enhance the effectiveness of chemo/radiation therapy to promote cancer cell death while protecting normal cells.

Objectives . The aim of this study was to investigate the hypothesis that dental material components alter cytokine secretion from monocytes if applied for several weeks at sublethal doses. The current study significantly extended exposure times of monocytes to the components over times published in previous studies. These exposure times approached the estimated average life span of monocytes in the bloodstream. Methods . Human THP-1 monocytes were exposed to 2-hydroxyethylmethacrylate (HEMA, 0–1.2 mmol/l), triethyleneglycoldimethacrylate (TEGDMA, 0–0.75 mmol/l), Hg 2+ (0–2 μmol/l), or Ni 2+ (0–20 μmol/l) for 2 weeks. The cells were then collected and additionally incubated for 24 h, with or without bacterial lipopolysaccharide (LPS), a common component of dental plaque. TNF-α secretion from THP-1 was determined using by enzyme-linked immunosorbent assay. Results . None of the dental material components induced TNF-α from THP-1 by themselves, but LPS alone strongly induced TNF-α secretion as expected. HEMA and TEGDMA significantly suppressed (40–70%) TNF-α secretion from cells stimulated with LPS. Hg 2+ at 2.0 μmol/l doubled TNF-α secretion from THP-1s stimulated with LPS over LPS alone. Ni 2+ did not significantly affect TNF-α secretion, with or without LPS exposure. Significance . The results in this study suggest that sublethal, 2-week exposures of some dental material components may alter TNF-α secretion from THP-1 monocytes when the cells are challenged. These alterations may influence the biological response of tissues to materials in an inflammatory intraoral environment.

Objectives: The purpose of this research was to examine the influence of enamel matrix proteins (EMP) on the viability, proliferation, and attachment of periodontal ligament fibroblasts (PDLF) to diseased root surfaces. Materials and Methods: Primary cell cultures of PDFL were obtained from clinically healthy third molars or premolar teeth. Viability and proliferation rates were carried out over a 10-day period. A total of 80,000 cells were plated in 24-well plates followed by EMEM with 10% FBS (positive control) and EMEM plus EMP at 25, 50, 75, and 100 μg/ml. Cells were harvested on days 1, 3, 5, 7, and 10 and viability was performed utilizing an MTS assay. PDLF proliferation rates were assessed by a CyQUANT GR dye assay. SEM analysis was used to examine the qualitative effects of cellular attachment to diseased root surfaces following EMP compared to nontreated controls. Results: The results indicated that viability was negatively affected for higher doses over time while lower doses displayed viability effects similar to control. Proliferation, however, appeared to be ameliorated following exposure to EMP. The SEM analysis suggests that cellular attachment to diseased dentin was enhanced following EMP application. Conclusion: These in vitro studies support the concept that EMP may act as a suitable matrix for PDLF.

Metals are components of a variety of biomaterials used in orthopedic and dental appliances; however, their biocompatibility with the surrounding tissues is not completely understood. Monocytes are important immune cells that respond to inflammatory stimuli by rapidly producing a variety of inflammatory proteins. Regulation of this response often involves activation of the transcription factor NF kappa B. The current study was designed to determine whether monocyte activation of NF kappa B in response to bacterial lipopolysaccharide (LPS) is affected by pretreatment with metal ions. Concentrations of metal ions that affected cell number after 24 h of exposure were first determined. Then THP-1 human monocytes were cultured for 2 h in media containing metal ions at concentrations below levels that altered cell growth. Parallel cultures were treated with 10 microg/mL Escherichia coli LPS, and all samples were cultured an additional 2 h. Nuclear proteins were extracted and normalized amounts were incubated with [(32)P]-end-labeled NF kappa B consensus oligonucleotide. NF kappa B-DNA complexes were identified and quantified by electrophoretic mobility shift analysis. The extent of NF kappa B-DNA complex formation after metal ion pretreatment with or without LPS induction was compared to no treatment or LPS-only treated controls. Finally, LPS-induced IL1 beta secretion was measured from palladium-treated and control cells. Concentrations were identified for each metal ion (Ag(+), Co(2+), Cu(2+), Hg(2+), Ni(2+), and Pd(2+)) that did not reduce cell number after 24 h of exposure (ranging from 5 microM for Ag(+) and Hg(2+) to 200 microM for Ni(2+)). Exposures of 2 h at these concentrations did not alter cell morphology, staining with trypan blue, or cell number. LPS exposure had no effect on cell number with or without metal ions after 2 h. When metal treatment alone was assessed, none of the metal ions had a significant effect on NF kappa B-DNA binding. However, pretreatment with Co(2+), Ni(2+), Ag(1+), Hg(2+), and Pd(2+) significantly decreased NF kappa B-DNA binding by 40-70% versus LPS alone. Only Cu(2+) had no effect on LPS-induced NF kappa B-DNA complex formation. Pd(2+) lowered, but did not abolish, IL1 beta secretion at concentrations comparable to those that altered NF kappa B-DNA binding. These results suggest that many commonly used metals alter monocyte function at concentrations that are not overtly toxic, and that protein levels controlled in part by NF kappa B also may be altered.

Laser-ablation sector-field (high resolution) inductively coupled plasma mass spectrometry (LA-HR-ICP-MS) has been used for in situ determination and spatial elemental profiling of nickel concentrations in tissues that have been exposed to nickel wire. Nickel has a number of adverse biological effects that have made the use of nickel (or any other metal) in biomedical implants controversial. Yet, information about the distribution of nickel in tissues around nickel-containing implants is scarce. This study examines the diffusion of nickel with time and the spatial distribution of nickel around nickel-containing implants in vivo. Pure nickel wires were implanted subcutaneously into rats for seven days and the tissues were analyzed for nickel content and degree of inflammation away from the implants using 24Mg and 60Ni isotopes. Data were obtained by ablation with Nd:YAG laser operating in the UV region (266 nm and 213 nm) and element analysis with a high resolution ICP-MS. A 50 ppm glass standard (NIST-612) was also analyzed for the same isotopes. Quantification was performed by assuming a uniform nominal magnesium concentration value of 97 µg g−1 in untreated tissue and using 24Mg intensity for internal calibration. The precision (RSD%) of measurements for 24Mg for the NIST-612 Glass standard was within 3.8% to 4.6% and for the tissue samples was within 3.2% to 4.5%. The precision of analysis for 60Ni for the NIST-612 Glass standard was 5.4%. There was a significant penetration of nickel ions into tissues exposed to nickel wire implants. The concentration of nickel reached values as high as 60 µg g−1 near the implants, falling exponentially to undetectable levels 3–4 mm from the implants. The study showed that the laser ablation technique was well suited for analysis of soft tissues for metal ion content. This technique also allowed metal concentration spatial profiling as a function of time.

Monocytes play a central role in the response of tissues to biomaterials. Monocytic cell lines such as the THP-1 cell line have been used extensively as models for primary monocytes (directly from blood) in biocompatibility research. However, little information exists about the appropriateness of these cell lines as models. Thus, the current study compared the biological response of both primary peripheral blood monocytes (PBMs) and the THP-1 cell line to four common components of dental materials known to be released into the oral environment: nickel ions, 2-hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA), and 2,2-bis[4(2-hydroxy-3-methacryloloxy)-phenyl]propane (Bis-GMA). Comparisons were made by constructing dose-response curves for each type of monocyte and the four components. The 50% cytotoxicity values (TC50 values) were then statistically compared. In addition, the response of the monocytes to the materials with and without lipopolysaccharide (LPS) stimulation were assessed by measuring TNF-alpha secretion from the monocytes. The results showed that the PBMs were 5-10 times less sensitive than the THP-1 monocytes to these dental components, but that both cell lines ranked the components identically. TNF-alpha secretion from both types of monocytes often showed similar trends, although some inconsistent results were noted. The current study supports the use of THP-1s as a model for ranking the cytotoxicity of components of dental biomaterials. Furthermore, the secretory activity of PBMs appears to be generally well represented by the THP-1s. However, sufficient differences between these cell types exist to recommend confirmation of any critical results obtained with THP-1s using PBMs.

Few studies have investigated the ability of dental resins to induce cellular stress at sublethal concentrations. Cellular stress, especially in immune cells such as monocytes, may modulate the biological response to materials or the host's ability to respond to bacterially mediated inflammation. The current study examined the ability of sublethal concentrations of 2-hydroxylethylmethacrylate (HEMA) and triethyleneglycol dimethacrylate (TEGDMA) to induce heat shock protein 72 (HSP72) in human monocytes. HEMA and TEGDMA significantly suppressed heat-induced HSP72 expression, even at sublethal levels, but did not induce HSP72 by themselves. The results of the current study suggest that components released from dental resin could modulate the HSP stress response without altering cellular metabolic activity.

Highly filled composites, Ormocers (organically modified ceramics) and 'smart' materials have been developed to overcome the polymerization shrinkage problems of conventional composite materials. The purpose of the current study was to investigate the effect of longer-term (up to 8 weeks) ageing of these resin-based dental restorative materials and determine the effect of post-curing on cytotoxicity. Twelve discs of each material (Colombus/IDR, Definite/Degussa, Ariston pHc/Vivadent) were either light-cured (Lc) or light-cured and post-cured (Pc). For cytotoxicity testing, the discs were placed in contact with cell culture medium (DMEM) and incubated at 37 degrees C. Extracts from composite materials were collected after 24 h and weekly over a time period of 8 weeks. Cytotoxicity of the eluates to cultured fibroblasts (Balb/c3T3) were measured by the succinic dehydrogenase (SDH) activity (MTT assay) and the results expressed in percentage of negative controls (Teflon discs). The results showed that ageing significantly influenced the cytotoxicity of the materials. Except for Ariston pHc, materials were less cytotoxic after 8 weeks of ageing than they were in early intervals and post-curing was not generally useful in reducing cytotoxicity. The Ariston pHc was initially moderately toxic, but then become highly cytotoxic for 5 weeks before returning to initial levels. The current study demonstrated the importance of assessing the cytotoxicity of resin composite materials at multiple times.

In dentistry, antibacterial photodynamic therapy (a-PDT) has shown promising results for inactivating bacterial biofilms causing carious, endodontic and periodontal diseases. In the current study, we assessed the ability of eosin Y exposed to 3 irradiation protocols at inactivating Enterococcus faecalis biofilms, in vitro.E. faecalis biofilms formed on hydroxyapatite disks were incubated with eosin Y (10-80μM), then activated with blue light using different irradiation protocols. Biofilms exposed to continuous exposure were incubated for 40min before being light-activated for 960 s. For the intermittent exposure, biofilms were exposed 4 times to the light/photosensitizer combination (960 s total) without renewing the photosensitizer. For repeated a-PDT, the same light dose was delivered in a series of 4 irradiation periods separated by dark periods; fresh photosensitizer was added between each light irradiation. After treatment, bacteria were immediately labeled with LIVE/DEAD BacLight Bacterial Viability kit and viability was assessed by flow cytometry (FCM). Results were statistically analyzed using one-way ANOVA and Tukey multiple comparison intervals (α=0.05).The viability of E. faecalis biofilms exposed to 10μM eosin Y, was significantly reduced compared to controls (light only-eosin Y only). After a second exposure to blue light-activated eosin Y, viability significantly decreased from 58% to 12% whereas 6.5% of the bacterial biofilm remained live after a third exposure (p0.05). Only 3.5% of the bacterial population survived after the fourth exposure.The results of this study indicate that blue light-activated eosin Y can photoinactivate E. faecalis biofilms grown on hydroxyapatite disks. Also, repeated exposures to blue light-activated eosin Y were shown to significantly improve efficacy. Further studies seem warranted to optimize the antibacterial activity of blue light-activated eosin Y on major oral pathogens.

Failing implants with loss of alveolar bone are associated with gram-negative bacteria that carry lipopolysaccharide (LPS) in the bacterial cell wall. Bony regeneration around these implants is still an unpredictable procedure due to the many clinical factors involved. One important factor is the presence of contaminants such as LPS on the implant surface. The effect of implant-associated LPS on the attachment of bone cells to the implant surface is unknown. This project investigated the effect of LPS on the attachment of osteoblast-like cells (MC3T3-E1) to titanium and titanium alloy surfaces in vitro. We hypothesized that LPS would inhibit bone cell attachment either through loss of cellular attachment sites or alteration of cellular function. Three experimental approaches were used. First, alloy surfaces were exposed to LPS (100 μg/mL) before the cells were allowed to attach. In the second approach, the cells were exposed to the LPS before they were allowed to attach. Last, the cells were allo...

Statement of problem. Contamination of removable prostheses with microorganisms, particularly Candida albicans, is a common clinical problem. Microban, a broad-spectrum antimicrobial containing triclosan, recently has been proposed to inhibit microbial growth. Purpose. This study aimed to determine whether the addition of Microban to PermaSoft denture liner prevents the growth of C albicans and affects the cytotoxicity of the PermaSoft material. Material and methods. Experimental specimen disks (5 × 1 mm each) with and without incorporated Microban were fabricated aseptically (n = 6) against polyester film to produce a smooth surface. To assess the cytotoxic effect of Microban, the MTT assay was used. To determine the effect of Microban on the growth of C albicans, disks were placed in Transwell dishes, covered with Sabouraud's broth containing an ATCC strain of C albicans, and incubated at 37°C for 24 hours. Wells containing fluorocarbon resin disks or broth alone served as controls. The disks were rinsed to remove unattached C albicans and then sonicated in sterile water to remove surface organisms. Serial dilutions of the water extracts were plated on Sabouraud's agar and returned to the incubator for 24 hours. Colonies were counted with a Brunswick Colony Counter. Growth of C albicans in the internal aspects of the specimens was determined in a manner as previously described, with the exception that the specimens were sonicated to remove surface organisms, minced, and sonicated once more before making serial dilutions. The results were compared with ANOVA and Tukey intervals (α=.05). Results. The number of colonies formed ranged from 17 to 31 × 10 5 (mean = 23 ± 4 × 10 5 ) and 14 to 69 × 10 5 (mean = 32 ± 20 × 10 5 ) for the PermaSoft with and without Microban groups, respectively. There was no statistically significant difference between PermaSoft with and without Microban. Conclusion. The addition of Microban did not significantly alter the cytotoxicity of the PermaSoft denture lining material or reduce the adherence of viable C albicans to the surface of PermaSoft material after 24 hours. (J Prosthet Dent 2001;85:352-6.)

Certain cells of the periodontium are necessary for the regeneration of tissues that are destroyed as a result of periodontal disease. There has been debate regarding which cells are the primary participants in periodontal regeneration. It is a well-known fact that osteoblasts are essential in new bone formation, but controversy surrounds the role that gingival fibroblasts may play in the regeneration of the hard tissues of the periodontium. If gingival fibroblasts could contribute to the regeneration of these tissues, they might provide an additional source of progenitor cells. The bone morphogenetic proteins are potent stimulators of cell differentiation and have been shown to induce new bone formation in many experimental models. This project investigated the ability of recombinant human bone morphogenetic protein–2 (rhBMP-2) to (1) enhance the production of markers of osteoblastlike cells (osteocalcin and mineralization in culture) in human osteosarcoma cells (MG63) and to (2) induce the expr...

The release of metal ions from dental restorations has been well established, but the sublethal effects of these ions on oral tissues remain undefined. Metal ions are a potential cause of sublethal oxidative stress in cells. Oxidative stress is known to alter cellular processes which are important in the inflammation of tissues. The presence of oxidative stress is commonly assessed by measuring the oxidized (GSSG) and reduced (GSH) forms of cellular glutathione. Normally, the majority of cellular glutathione exists as GSH and the GSH–GSSG ratio is high. Since monocytes often orchestrate inflammatory responses, oxidative stress in monocytes is important. Our hypothesis for the current work was that metal ions induce oxidative stress in monocytes which is manifested by a lower GSH–GSSG ratio. Human THP-1 monocytes were exposed for 24 h to sublethal concentrations of ions of Ag, Be, Co, Cu, Hg, Ni, Pd, and Zn – all known to be released from dental biomaterials. GSH and GSSG were measured using colorimetric assays. Cu lowered the GSH–GSSG ratio as hypothesized, but the ratio could not be determined for other metals because other metal ions interfered with the GSSG assay. However, a statistically significant ( anova/Tukey) increase in GSH per cell was observed upon exposure to Ag (50%), Co (100%), Hg (250%) and Zn (10%). This increase may be indicative of an oxidative stress in its own right. Alterations in GSH levels may be important to how released metal ions alter cytokine secretion from monocytes and other cells which play a role in the inflammatory response to dental biomaterials.

Previous studies have demonstrated and quantified the cytotoxicity of metal ions in vitro, but the data from these reports have been limited to short-term exposures of metal ions to cells (24-72 h). Yet, the longer-term, low-dose effects of metal ions are most relevant to the clinical use of dental and other biomedical alloys. Thus, the purpose of the current study was to assess longer-term effects of ions of silver, copper, mercury, and nickel - four metal ions known to be released from dental alloys - on monocytes. THP-1 human monocytes were exposed to the metal ions for up to 4 weeks. Concentrations of the metal ions were 1-10% of those known to cause cytotoxicity with 24-h exposures. Cellular proliferation and cellular viability were measured weekly. Ag(1+) and Hg(2+) did not alter the percentage of nonviable cells, but Cu(2+) and Ni(2+) increased the nonviable component as a function of metal concentration. These effects were cumulative over the 4 weeks only for Ni(2+). All metal ions caused a significant reduction in cellular proliferation, but the pattern of the effect was unique to each metal ion, and the effects were often not evident until 3 or 4 weeks of exposure. The results of the current study indicate that metal ions released from metallic biomaterials may have adverse biological effects at concentrations lower than previously reported.

The release of elements from dental casting alloys is directly related to adverse biological effects they may have. Longer-term (>1 month) studies of elemental release have suggested that release decreases significantly after a higher initial release of elements. The aim of the current study was to measure the release of elements from a variety of clinically relevant dental casting alloys and compare the release at weekly intervals through 4 weeks. The hypothesis was that the release during the initial week should be higher than in subsequent weeks, and that cytotoxicity should decrease as elemental release decreases. Alloy samples were exposed to cell-culture medium which was changed at weekly intervals and assessed for elemental release by means of atomic absorption spectrometry. The cytotoxicity of the medium was also measured. The results showed that for single phase alloys, initial release was often significantly higher in the first weeks than in subsequent weeks, but not for all elements in an alloy. Multiple phase alloys showed steady or increasing release relative to the first week. Cytotoxicity relationships were complex depending on which elements were released and the ratios of elements released. This study suggests that short-term tests (

Although pit and fissure sealants have been utilized extensively in dentistry as a way of preventing occlusal caries, results described by Olea et al. (1996) raised concerns about the safety of sealants and other resin-based dental materials due to the reported presence of bisphenol A (BPA) and its dimethacrylate ester (BPA-DM). Although the release of these compounds from dental materials has not been substantiated by two subsequent studies, we believed it was important to confirm or refute the report that BPA and BPA-DM have estrogenic activity in vitro. We grew breast cancer cells (MCF-7, T-47D, ZR-75-1) known to proliferate under estrogenic stimulation in phenol red-free DMEM containing human serum and concentrations of BPA or BPA-DM ranging from 10−8M to 5 × 10−6M. After 1 week, plates were harvested for crystal violet or sulforhodamine-B assays, and the optical densities of groups of treated cells were compared with values from control cells. At concentrations at or above 10−6M, both BPA and BPA-DM significantly increased cell proliferation (p < 0.05), comparable to the increase seen with 10−9M of estrogen. Flow cytometric methods demonstrated that these mitogenic effects occurred within 24 h of exposure to estrogen, BPA, or BPA-DM. The increase in DNA synthesis was analogous to that seen with estrogen stimulation. Thus, we confirmed that BPA and BPA-DM cause cell proliferation at micromolar concentrations that exceed the effective concentrations of estrogen by 1 to 10,000-fold. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 45, 192–197, 1999.

Statement of problem. Dental casting alloys are subjected to transient acidity in the oral environment, yet most studies have not investigated the effects of these transient environments on elemental release from alloys. Elemental release is important because it plays a significant role in alloy biocompatibility. Purpose. It was hypothesized that acidic environments would increase elemental release from dental alloys during exposure and after the acidic environment was removed. This hypothesis was based on the known increase in release of nickel from nickel-based alloys in an acidic environment. Material and methods. High-noble, noble, and base metal casting alloys were exposed for 30 minutes to solutions with pH ranging from 1 to 7. Elemental release of representative elements was measured by means of atomic absorption spectrometry during the exposure and in the week after the exposure. This release was compared with elemental release in the week before the exposure. Results. High-noble and noble alloys were resistant to acidic environments. A pH of 4 did not increase elemental release during or after exposure. A pH 1 environment slightly elevated release of Ag, Cu, and Pd in some alloys. However, a Ni-based alloy released large amounts of Ni during the acidic exposure of pH 1 or 4, and more importantly, in the week after the exposure as well. Increased time of exposure to acid did not alter elemental release from noble or high-noble alloys, but markedly increased release from the Ni-based alloy. Conclusions. Transient exposure of casting alloys to an acidic oral environment is likely to significantly increase elemental release from Ni-based alloys, but not from high-noble or noble alloys. (J Prosthet Dent 1998;80:691-8.)

Dentin bonding agents (DBA) have been considered for use as root-end fillings. Previous studies have documented the release of DBA components in vivo and in vitro, but the biological implications are not clear. The macrophage is important in wound healing, and likely to be important in any inflammatory response. Therefore, this study determined the concentrations of the components of DBAs that suppress the mitochondrial activity of human macrophages in vitro. THP-1 macrophages were cultured in the presence of four DBA components (2-hydroxyethyl methacrylate (HEMA), 4-methacryloxyethyl trimellitate anhydride (4-META), bisphenol-glycidylmethacrylate (Bis-GMA), and urethane dimethacrylate (UDMA)) at various concentrations and for varying durations. Residual effects were also measured after the resins were removed. Controls received only the vehicle solution, ethanol or water. THP-1 mitochondrial activity was estimated using the MTT assay, and the 50% toxicity concentrations (TC50) were determined graphically. Resin components suppressed the mitochondrial activity of macrophages at different concentrations (TC50 values for HEMA (10,000 mumol/L), 4-META (3,800 mumol/L), Bis-GMA (130 mumol/L), and UDMA (110 mumol/L) at 24 h, and the effect was time-dependent. Residual effects were observed for all resins.

The release of elements from eight types of commonly used dental casting alloys into cell-culture medium was measured over a 10-month period. The release of elements was determined to provide information about the long-term biological risk these alloys may pose to the oral tissues. The current work extends previous studies of shorter time periods, and is more relevant to the in vivo situation, where dental alloys are present intraorally for years.The alloys were Au-, Ag-, Pd-, and Ni-based with nobilities ranging from 0 to 95 at.%. Alloy samples (n = 12) were exposed to cell-culture medium. The medium was changed every 30 days for 10 months. Elemental release into the medium was measured by means of atomic absorption spectrophotometry. Differences in mass release were determined using ANOVA and Tukey multiple comparison intervals (alpha = 0.05).The release of elements continued through 10 months, and it appeared that the release was constant throughout most of the experiment. Higher initial rates were suspected but not verified. Most alloys reached a constant rate after100 days of exposure to the medium. Long-term element release was not generally intuitive based on the amount of an element in an alloy or the overall nobility of the alloy. Total mass lost over the 10-month period ranged from2 micrograms/cm2 for the Au-Pd alloy to 55 micrograms/cm2 for the Au-Ag-Cu alloy (Tukey interval at alpha = 0.05 was 0.8 microgram/cm2). By comparison, pure Cu lost 4500 micrograms/cm2 during this period.Tests which assess biological risk from elemental release must consider longer-term release because elemental release continues for extended periods. Longer-term mass loss from a given alloy is often not intuitive based on its overall composition or noble metal content.

Streptococcus mutans biofilms are considered as primary causative agents of dental caries. Photodynamic antimicrobial chemotherapy (PACT) has been recently proposed as a strategy for inactivating dental biofilms. This study aimed to investigate the effect of blue light activated curcumin on S. mutans viability and to explore its potential as a new anti caries therapeutic agent. The effect of different concentrations and incubation times of photo activated curcumin on the survival of S. mutans in planktonic and biofilm models of growth was assessed by flow cytometry. Streptococcus mutans in planktonic suspensions or biofilms formed on hydroxyapatite disks were incubated for 5 or 10min with curcumin prior to blue light activation. Bacteria were labeled with SYTO 9 and propidium iodide before viability was assessed by flow cytometry. Results were statistically analyzed using one way ANOVA and Tukey multiple comparison intervals (a=0.05). For planktonic cultures 0.2µM of light activated curcumin significantly reduced S. mutans viability (p

Previous studies have shown that Ni-based alloys implanted into soft tissues cause an infiltration of inflammatory cells around the implant. This phenomenon is potentially important to dental alloys which are adjacent to oral tissues. To help define the mechanisms by which Ni causes an infiltration of inflammatory cells, we exposed endothelial cells in vitro to Ni ions and measured the expression of intercellular adhesion molecule 1 (ICAM-1). ICAM-1 is known to be involved in the recruitment of inflammatory cells from the bloodstream. We also exposed macrophages to Ni ions to test the hypothesis that Ni might alter cytokine secretion and subsequently cause expression of ICAM-1 on endothelial cells. The results showed that Ni ions could promote the expression of ICAM-1 on endothelial cells, but only at concentrations which were high enough (850 mumol/L for 24 h) to suppress cell metabolic activity. Although we had previous evidence that Ni could cause macrophages to secrete cytokines such as interleukin 1 beta, Ni-exposed macrophage supernatants did not induce expression of ICAM-1 on endothelial cells at concentrations subtoxic to the macrophages (85 mumol/L). At subtoxic concentrations, Ni ions were able to suppress ICAM-1 expression on endothelial cells which were stimulated with lipopolysaccharide. Thus, Ni ions either promoted or suppressed the expression of ICAM-1 depending on their concentration. This dual action of Ni ions may be important in vivo where a gradient of concentrations of released ions is likely to exist around the implanted biomaterial. Further studies are necessary to determine the effect of time of exposure and the molecular mechanisms of increased ICAM-1 expression.

Mercury vapor release from amalgams during setting significantly decreases when the amalgams are prepared with binary Hg-In liquid alloys. The objective of this study was to compare the cytotoxicity of amalgams made with experimental Hg-In alloys with that of amalgam without In and a commercial In-containing amalgam.Amalgam specimens were prepared by triturating a high-Cu alloy powder (Tytin, Kerr) with pure Hg or Hg-In liquid alloy containing 5, 20 or 50% In and also by triturating an In-containing high-copper alloy powder (Indiloy, Shofu) with pure Hg. After the specimens were aged for 2 wk, a cylindrical specimen of each amalgam was immersed consecutively in cell culture medium for 0-8, 8-48 and 48-72 h. The cytotoxicity of the extracts was determined by placing them in contact with Balb/c 3T3 mouse fibroblasts for 24 h, after which the succinic dehydrogenase (SDH) activity was measured and expressed as a percentage of the Teflon negative controls. The results were statistically compared using ANOVA and Tukey's test (alpha = 0.05). The concentration of elements released into the extracts was determined by atomic absorption spectrophotometry and evaluated by Kruskal-Wallis and nonparametric multiple comparisons.For the 0-8 h and 8-48 h intervals, the 20% In amalgam was significantly (p0.05) less toxic than the other amalgams, and not different from the Teflon control. Results for the other amalgams were only slightly depressed compared to the Teflon control. For the 48-72 h interval, all amalgams were essentially no different from the control. Copper was the element dominantly released into the medium from all the amalgams tested.For amalgam tested after aging, alloying indium to mercury did not deleteriously affect the cytotoxicity of the resultant amalgam compared to the amalgam without indium.

The use of nickel casting alloys for long-term restorations in dentistry has long been controversial. A ‘tug-of-war’ between economic, engineering and biological considerations is central to this controversy; nickel-casting alloys have low costs and favorable physical properties, but are corrosion-prone in the oral environment. Clinicians and researchers have questioned the safety of nickel-containing dental alloys because several nickel compounds are known to cause adverse biological effects in vivo and in vitro in contexts outside of dentistry. The debate revolves around the extent to which corrosion products from oral restorations cause intraoral or systemic biological problems. Current evidence suggests that nickel alloys may be used successfully and safely in dentistry if clinical risks are taken into account. However, these alloys may cause significant clinical problems, primarily allergenic and inflammatory, if the risks are ignored.

In dentistry, palladium is a very common component of dental casting alloys of all types, and its use has increased over the past several decades in response to the increased cost of gold. However, there have been recent controversies, particularly in Germany, over possible adverse biological effects of using palladium in dental alloys. Therefore, the purpose of this paper is to review the known biological effects of palladium and the likelihood that these effects can be caused by dental alloys which contain palladium. In an ionic form and at sufficiently high concentrations, palladium has toxic and allergic effects on biological systems. Palladium allergy almost always occurs in individuals who are sensitive to nickel. The carcinogenic potential of the palladium ion is still unclear, although there is some evidence that it is capable of acting as a mutagen. However, there are no well documented cases of adverse biological reactions to palladium in the metallic state. Furthermore, in spite of the potential adverse biological effects of palladium ions, the risk of using palladium in dental casting alloys appears to be extremely low because of the low dissolution rate of palladium ions from these alloys.

The goal of placement of endosseous dental implants is to achieve osseointegration or biointegration of the bone with the implant. A wide variety of materials has been used for these implants, but only a few promote osseointegration and biointegration. Titanium and titanium alloy (Ti6A14V) have been the most widely used of these materials. The surface oxide of titanium appears to be central to the ability of this material to osseointegrate. The oxide limits dissolution of elements and promotes the deposition of biological molecules which allow bone to exist as close as 30 A to the surface of the implant. The details of the ultrastructure of the gap between the implant and bone remain undefined, and the consequences of elements which are released on the interface over time are not known. These areas of investigation are particularly important in defining the differences between commercially pure titanium implants and those made of titanium, aluminium and vanadium. The epithelial interface between the gingiva and titanium appears to contain many of the structural characteristics of the native tooth-gingiva interface, but details are still vague. The connective tissue interface with the titanium appears to be one of tightly fitting tissues rather than adhesion. Ceramic coatings appear to improve the ingrowth of bone and promote chemical integration of the implant with the bone. The characteristics of these coatings are complex and affect the bony response, but the mechanisms remain obscure. The degradation of the coatings is an issue of particular controversy. Progress in dental implantology is likely to continue as the interface between the material and bone is more clearly understood, and biological molecules and artificial tissues are developed.

In dentistry, residual infection remains a major cause of failure after endodontic treatment; many of these infections involve Enterococcus faecalis. In the current study, we explored the possibility that blue light activated photosensitizers could be used, in principle, to inactivate this microbe as an adjunct disinfection strategy for endodontic therapy. Three blue light absorbing photosensitizers, eosin-Y, rose bengal, and curcumin, were tested on E. faecalis grown in planktonic suspensions or biofilms. Photosensitizers were incubated for 30 min with bacteria then exposed to blue light (450-500 nm) for 240 s. Sodium hypochlorite (3%) was used as a control. After 48 h, the viability of E. faecalis was estimated by measuring colony-forming units post-exposure vs. untreated controls (CFU/mL). Blue light irradiation alone did not alter E. faecalis viability. For planktonic cultures, blue light activated eosin-Y (5 μM), rose bengal (1 μM), or curcumin (5 μM) significantly (p

Objectives. This study was conducted to 1) measure the sensitivity of human and mouse macrophages to metal ions which are released from dental biomaterials, 2) compare these sensitivities with those of other cell types in the oral cavity, and 3) determine if metal ions alter the metabolism and synthetic processes of these cells at lower concentrations than are required to lyse the cells. This information will help define the biological risks associated with the release of metal ions into the oral cavity. Methods. Macrophages were exposed to a range of concentrations of Ag 1+ , Au 3+ , Cu 2+ , Hg 2+ , Ni 2+ , Pd 2+ , Pt 4+ , and Zn 2+ for 24 h in cell culture. The concentrations which caused a 50% decrease in succinic dehydrogenase (SDH) activity, protein production, and lactate dehydrogenase (LDH) release were measured and compared with these values for fibroblasts and osteoblasts. Results. Most metal ions caused alteration in SDH activity and protein production at lower concentrations that were required to induce LDH release. There were exceptions to this trend, and the differences were not always statistically significant. Furthermore, although the macrophages sometimes had statistically different sensitivities to metal ions than fibroblasts or osteoblasts, these differences were less than one order of magnitude. Macrophage response to the metal ions was highly dependent on the metal ion and the species of macrophage. Significance. Macrophages react adversely to metal ions at similar concentrations as other cell types found in the oral cavity. Furthermore, the concentrations which affect cell metabolism and protein production are generally lower than those which lyse the cells. Thus, non-lethal concentrations of metal ions may alter the secretion of protein inflammatory mediators such as cytokines which direct the inflammatory responses in tissues.

An in vitro screening test was used to compare the cytotoxicity and elemental release from mercury- and gallium-based dental restorative materials.The test employed three sequential extractions of the samples into cell-culture medium which were then used to evaluate the cytotoxicity of the samples and the release of elements from the samples. Cytotoxicity was measured by placing the extract in contact with Balb/c mouse fibroblasts for 24 h and measuring the succinic dehydrogenase activity of the cells. The release of elements was measured by means of atomic absorption spectrophotometry.Samples of Tytin (Kerr) showed no cytotoxicity compared to Teflon controls. Dispersalloy (Johnson and Johnson) was severely cytotoxic initially when Zn release was greatest, but was less toxic between 48 and 72 h as Zn release decreased. Gallium Alloy GF (Tokuriki Honten) was moderately cytotoxic after 8 h, and increased in cytotoxicity thereafter, which correlated with a substantial and persistent release of Ga from this material.The results of the current study concurred with in vivo assessments of these materials, and the use of sequential extractions was useful in determining trends in the cytotoxicity and elemental release from these materials.

Cytotoxicity testing of dental restorative materials must be viewed as an assessment of hazards, that is the potential of the material to cause pulpal problems. In this context, composites, glass ionomers, amalgams, zinc-based cements and peroxide bleaching agents are all possible hazards to the pulp. The risks that these materials will cause pulpal toxicity in vivo can be partly estimated by assessing the cytotoxicity of the substances which are released from these materials in vitro and comparing these cytotoxic concentrations with those concentrations that are present in vivo. The resin components of composites, metal ions and hydrogen peroxide, all of which are released from dental restorative materials, have been shown to be cytotoxic in vitro in sufficient concentrations. The potencies of these substances are quite diverse. However, the cytotoxicity of these substances in usage tests, and therefore the risks of pulpal toxicity, depends on their ability to diffuse through the dentine and accumulate in the pulp.

Summary The diffusion through dentine by a number of biological and synthetic molecules, including resins and dyes, is reported. In vitro measurements were derived by experiments with a modified ‘split-chamber device’. Diffusion was found to be indirectly proportional to dentine thickness for all molecules. Permeability of water-soluble molecules and ethanol-soluble molecules was proportional to the molecular weights, except for fluorescein, hydrogen peroxide (H2O2) and urethane dimethacrylate. The resin components tested are not soluble enough in an aqueous medium to diffuse through 0.5 mm dentine at sufficient concentrations to cause cytotoxicity to pulpal cells.

Nickel-based alloys are used for dental restorations because of their strength, high moduli, and relatively low cost. However, these alloys corrode significantly in use, particularly in lower pH environments that are common under oral biofilms. Ni(II) corrosion products increase inflammatory cytokine secretion from activated monocytes, suggesting that nickel alloys may exacerbate inflammatory responses in adjacent periodontal tissues caused by dental plaque. Because inflammatory cytokine secretion is regulated in part by the NFκB signaling pathway, our goal in the current work was to determine whether Ni(II) altered cellular levels or nuclear localization of NFκB-family subtypes. THP1 monocytes were exposed to Ni(II) for 72 h, and activated with lipopolysaccharide for the last 30 min to 6 h. Secretion of IL6 and TNFα were measured using ELISA, and NFκB levels and localization was measured using SDS-PAGE with immunoblots and digital analysis. We observed that Ni(II) did not alter the levels of secreted TNFα from activated monocytes, but increased secreted IL6 levels about 30% over controls. Ni(II) did not alter whole-cell levels of any NFκB subtype, but increased nuclear persistance of p65 and c-Rel. Our results suggest that Ni(II) may increase inflammatory cytokine secretion by increasing nuclear localization of some NFκB subtypes. Further studies should be done to determine the prominence of this mechanism in clinical environments. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.

Medline, CENTRAL, LILACS, TRIP Database, National Guideline Clearinghouse, OPENSigle and a number of other medical / dental databases and websites, as well as reference lists.Randomised controlled trials and controlled clinical trials in any language that compared oxalates with placebo or no treatment were eligible for inclusion.Three reviewers extracted data with two people assessing quality independently using the Cochrane risk of bias domains. Standardized mean differences (SMD) were estimated by random-effects meta-analysis and heterogeneity between studies was quantified with the I2-statistic.12 reports were included. Interventions were diverse and included: monohydrogen-monopotassium oxalate, ferric oxalate, di-potassium oxalate, or oxalate containing pre-polymerized resin, and combinations of monohydrogen-monopotassium and di-potassium oxalate. Follow up intervals varied between immediate to 1 year. Hypersensitivity was elicited by tactile, evaporative or thermal stimuli, and a number of outcomes used to measure pain. Risk of bias was high in a number of studies and statistical heterogeneity high. Based on 187 and 179 units (patients or teeth) in the intervention and placebo groups from seven studies, the summary SMD for 3% monohydrogen-monopotassium oxalate was -0.71 (95% Confidence Interval (CI):-1.48, 0.06), which suggests it may not be beneficial. There was no improvement with the other interventions.The review identified no evidence to indicate benefit from treating dentine hypersensitivity with oxalates beyond a placebo effect.