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Garry J P Fleming - One of the best experts on this subject based on the ideXlab platform.

  • biocompatibility effects of indirect exposure of base metal Dental Casting alloys to a human derived three dimensional oral mucosal model
    Journal of Dentistry, 2013
    Co-Authors: Emma Louise Mcginley, Gary P. Moran, Garry J P Fleming
    Abstract:

    Abstract Objectives The study employed a three-dimensional (3D) human-derived oral mucosal model to assess the biocompatibility of base-metal Dental Casting alloys ubiquitous in fixed prosthodontic and orthodontic dentistry. Methods Oral mucosal models were generated using primary human oral keratinocyte and gingival fibroblast cells seeded onto human de-epidermidised dermal scaffolds. Nickel–chromium (Ni–Cr) and cobalt–chromium (Co–Cr) base-metal alloy immersion solutions were exposed to oral mucosal models for increasing time periods (2–72 h). Analysis methodologies (histology, viable cell counts, oxidative stress, cytokine expression and toxicity) were performed following exposure. Results Ni-based alloy immersion solutions elicited significantly decreased cell viability ( P P P P P  > 0.4755) or cellular toxicity ( P Conclusions Although the multiple analyses highlighted Ni–Cr base-metal alloy immersion solutions elicited significantly detrimental effects to the oral mucosal models, it was possible to distinguish between Ni–Cr alloys using the approach employed. The study employed a 3D human-derived full-thickness differentiated oral mucosal model suitable for biocompatibility assessment of base-metal Dental Casting alloys through discriminatory experimental parameters. Clinical significance Increasing incidences of Ni hypersensitivity in the general population warrants serious consideration from Dental practitioners and patients alike where fixed prosthodontic/orthodontic Dental treatments are the treatment modality involved. The novel and analytical oral mucosal model has the potential to significantly contribute to the advancement of reproducible Dental medical device and Dental material appraisals.

  • influence of s mutans on base metal Dental Casting alloy toxicity
    Journal of Dental Research, 2013
    Co-Authors: Emma Louise Mcginley, Gary P Mora, Adam H Dowling, Garry J P Fleming
    Abstract:

    We have highlighted that exposure of base-metal Dental Casting alloys to the acidogenic bacterium Streptococcus mutans significantly increases cellular toxicity following exposure to immortalized human TR146 oral keratinocytes. With Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), S. mutans-treated nickel-based (Ni-based) and cobalt-chromium-based (Co-Cr-based) Dental Casting alloys were shown to leach elevated levels of metal ions compared with untreated Dental Casting alloys. We targeted several biological parameters: cell morphology, viable cell counts, cell metabolic activity, cell toxicity, and inflammatory cytokine expression. S. mutans-treated Dental Casting alloys disrupted cell morphology, elicited significantly decreased viable cell counts (p < 0.0001) and cell metabolic activity (p < 0.0001), and significantly increased cell toxicity (p < 0.0001) and inflammatory cytokine expression (p < 0.0001). S. mutans-treated Ni-based Dental Casting alloys induced elevated levels of cellular toxicity...

  • influence of s mutans on base metal Dental Casting alloy toxicity
    Journal of Dental Research, 2013
    Co-Authors: Emma Louise Mcginley, Adam H Dowling, Gary P. Moran, Garry J P Fleming
    Abstract:

    We have highlighted that exposure of base-metal Dental Casting alloys to the acidogenic bacterium Streptococcus mutans significantly increases cellular toxicity following exposure to immortalized human TR146 oral keratinocytes. With Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), S. mutans-treated nickel-based (Ni-based) and cobalt-chromium-based (Co-Cr-based) Dental Casting alloys were shown to leach elevated levels of metal ions compared with untreated Dental Casting alloys. We targeted several biological parameters: cell morphology, viable cell counts, cell metabolic activity, cell toxicity, and inflammatory cytokine expression. S. mutans-treated Dental Casting alloys disrupted cell morphology, elicited significantly decreased viable cell counts (p < 0.0001) and cell metabolic activity (p < 0.0001), and significantly increased cell toxicity (p < 0.0001) and inflammatory cytokine expression (p < 0.0001). S. mutans-treated Ni-based Dental Casting alloys induced elevated levels of cellular toxicity compared with S. mutans-treated Co-Cr-based Dental Casting alloys. While our findings indicated that the exacerbated release of metal ions from S. mutans-treated base-metal Dental Casting alloys was the likely result of the pH reduction during S. mutans growth, the exact nature of mechanisms leading to accelerated dissolution of alloy-discs is not yet fully understood. Given the predominance of S. mutans oral carriage and the exacerbated cytotoxicity observed in TR146 cells following exposure to S. mutans-treated base-metal Dental Casting alloys, the implications for the long-term stability of base-metal Dental restorations in the oral cavity are a cause for concern.

  • base metal Dental Casting alloy biocompatibility assessment using a human derived three dimensional oral mucosal model
    Acta Biomaterialia, 2012
    Co-Authors: Emma Louise Mcginley, Gary P Mora, Garry J P Fleming
    Abstract:

    Abstract Nickel–chromium (Ni–Cr) alloys used in fixed prosthodontics have been associated with type IV Ni-induced hypersensitivity. We hypothesised that the full-thickness human-derived oral mucosa model employed for biocompatibility testing of base-metal Dental alloys would provide insights into the mechanisms of Ni-induced toxicity. Primary oral keratinocytes and gingival fibroblasts were seeded onto Alloderm™ and maintained until full thickness was achieved prior to Ni–Cr and cobalt–chromium (Co–Cr) alloy disc exposure (2–72 h). Biocompatibility assessment involved histological analyses with cell viability measurements, oxidative stress responses, inflammatory cytokine expression and cellular toxicity analyses. Inductively coupled plasma mass spectrometry analysis determined elemental ion release levels. We detected adverse morphology with significant reductions in cell viability, significant increases in oxidative stress, inflammatory cytokine expression and cellular toxicity for the Ni–Cr alloy-treated oral mucosal models compared with untreated oral mucosal models, and adverse effects were increased for the Ni–Cr alloy that leached the most Ni. Co–Cr demonstrated significantly enhanced biocompatibility compared with Ni–Cr alloy-treated oral mucosal models. The human-derived full-thickness oral mucosal model discriminated between Dental alloys and provided insights into the mechanisms of Ni-induced toxicity, highlighting potential clinical relevance.

  • Development of a discriminatory biocompatibility testing model for non-precious Dental Casting alloys
    Dental materials : official publication of the Academy of Dental Materials, 2011
    Co-Authors: Emma Louise Mcginley, Garry J P Fleming, Gary P. Moran
    Abstract:

    Abstract Objectives To develop an enhanced, reproducible and discriminatory biocompatibility testing model for non-precious Dental Casting alloys, prepared to a clinically relevant surface finishing condition, using TR146 oral keratinocyte cells. Methods Comparative biocompatibility was determined following direct and indirect exposure of TR146 cells to two nickel–chromium (Ni–Cr) and a cobalt–chromium (Co–Cr) alloy-discs. The surface roughness of the discs was determined using a contact stylus profilometer and the elemental ion release by inductively coupled plasma mass spectrometry (ICP-MS). Subsequent biocompatibility analysis included cell morphology, cell density measurements with Trypan blue exclusion assay, inflammatory cytokine expression with ELISAs, cellular metabolic activity using XTT and cellular toxicity using lactate dehydrogenase (LDH) release assay. Results TR146 cell morphology was altered following direct and indirect exposure to the Ni–Cr alloys but not the Co–Cr alloy. Significant reductions (all P ® 15 alloy compared with d.Sign ® 10 alloy were identifiable (all P Discussion Nickel ions from the Ni–Cr alloys permeated the epithelial cells and activated a proinflammatory response, namely IL-1a, IL-8 and PGE2 expression. Further evidence of nickel ioninduced cell death was supported by the decreased biocompatibility of the highest nickel ion releasing alloy (d.Sign ® 15 compared with d.Sign ® 10) and the increased biocompatibility of the Co–Cr (d.Sign ® 30) alloy where nickel ions were absent.

Joel D. Bumgardner - One of the best experts on this subject based on the ideXlab platform.

  • metallurgical surface and corrosion analysis of ni cr Dental Casting alloys before and after porcelain firing
    Dental Materials, 2008
    Co-Authors: Hsinyi Lin, Bonnie Bowers, John T Wolan, Zhuo Cai, Joel D. Bumgardner
    Abstract:

    Abstract Objectives A porcelain veneer is often fired on nickel–chromium Casting alloys used in Dental restorations for aesthetic purposes. The porcelain-fused-to-metal (PFM) process brings the temperature to over 950 °C and may change the alloy's corrosion properties. In this study, the metallurgical, surface, and corrosion properties of two Ni–Cr alloys were examined, before and after PFM firing. Methods Two types of alloy were tested—a high Cr, Mo alloy without Be and a low Cr, Mo alloy with Be. Before the PFM firing, specimens from both alloys were examined for their microstructures, hardness, electrochemical corrosion properties, surface composition, and metal ion release. After the PFM firing, the same specimens were again examined for the same properties. Results Neither of the alloys showed any differences in their electrochemical corrosion properties after the PFM firing. However, both alloys exhibited new phases in their microstructure and significant changes in hardness after firing. In addition, there was a slight increase in CrOx on the surface of the Be-free alloy and increased Mo–Ni was observed on the surface of both alloys via X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). This might be one of the reasons why both alloys had increased Ni and Mo ion release after firing. Significance The PFM firing process changed the alloys’ hardness, microstructure, and surface composition. No significant changes in the alloys’ corrosion behavior were observed, however, the significant increase in metal ion release over a month may need to be further investigated for its clinical effects.

  • metallurgical surface and corrosion analysis of ni cr Dental Casting alloys before and after porcelain firing
    Dental Materials, 2008
    Co-Authors: Bonnie Bowers, John T Wolan, Joel D. Bumgardner
    Abstract:

    OBJECTIVES: A porcelain veneer is often fired on nickel-chromium Casting alloys used in Dental restorations for aesthetic purposes. The porcelain-fused-to-metal (PFM) process brings the temperature to over 950 degrees C and may change the alloy's corrosion properties. In this study, the metallurgical, surface, and corrosion properties of two Ni-Cr alloys were examined, before and after PFM firing. METHODS: Two types of alloy were tested-a high Cr, Mo alloy without Be and a low Cr, Mo alloy with Be. Before the PFM firing, specimens from both alloys were examined for their microstructures, hardness, electrochemical corrosion properties, surface composition, and metal ion release. After the PFM firing, the same specimens were again examined for the same properties. RESULTS: Neither of the alloys showed any differences in their electrochemical corrosion properties after the PFM firing. However, both alloys exhibited new phases in their microstructure and significant changes in hardness after firing. In addition, there was a slight increase in CrO(x) on the surface of the Be-free alloy and increased Mo-Ni was observed on the surface of both alloys via X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). This might be one of the reasons why both alloys had increased Ni and Mo ion release after firing. SIGNIFICANCE: The PFM firing process changed the alloys' hardness, microstructure, and surface composition. No significant changes in the alloys' corrosion behavior were observed, however, the significant increase in metal ion release over a month may need to be further investigated for its clinical effects.

  • cellular response to metallic ions released from nickel chromium Dental alloys
    Journal of Dental Research, 1995
    Co-Authors: Joel D. Bumgardner, L C Lucas
    Abstract:

    Concerns exist over the potential release of elevated levels of metal ions such as Ni and Be from Ni-Cr Dental Casting alloys, due to their susceptibility to accelerated corrosion. In this investigation, we evaluated the release of metal ions from four commercial Ni-Cr alloys, representing a range of compositions, in three-day cell culture tests. Metal ion release, as measured by atomic absorption spectroscopy, was correlated to changes in cellular morphology, viability, and proliferation. The results showed that the test alloys and their corrosion products did not affect cellular morphology or viabilities, but did decrease cellular proliferation. The types and amounts of metal ions released, which corresponded to the alloys' reported surface and corrosion properties, also correlated to observed decreases in cellular proliferation after 72 h. Neptune, which caused the smallest decrease in cellular proliferation as compared with control cells, released the lowest amount of corrosion products, due to its co...

  • effect of nickel based Dental Casting alloys on fibroblast metabolism and ultrastructural organization
    Journal of Biomedical Materials Research, 1995
    Co-Authors: J E Doeller, Joel D. Bumgardner, L C Lucas
    Abstract:

    Previous cell culture evaluations have shown that nickel–chromium Dental alloys did not affect cellular viability or morphology. However, nickel-based alloys released corrosion products which decreased cellular proliferation. It was hypothesized that this decrease was due to an interference of cellular energy metabolism by released metal ions. To test this hypothesis, we evaluated the effects on cellular energy metabolism, adenosine triphosphate (ATP) levels, and cellular ultrastructure by four nickel-based alloys, including high and low chromium alloys with and without beryllium additions, in human gingival fibroblast cell culture. Energy metabolism was evaluated by measuring glucose-6-phosphate dehydrogenase (G-6-PDH) activity. ATP levels were measured with the luciferin–luciferase method. Cellular membranes and ultrastructural organization were evaluated by scanning and transmission electron microscopy. The results of this study showed that metal ions released from all alloys completely inhibited G-6-PDH activity and reduced cellular ATP levels as compared to controls. The reduction in intracellular ATP was greater for the beryllium containing alloys than the non-beryllium-containing alloys. However, no morphologic changes in cellular membranes or organelles were observed. These results support the hypothesis that metal ions released from nickel-based Dental Casting alloys interfere with cellular energy metabolism. © 1995 John Wiley & Sons, Inc.

  • corrosion and cell culture evaluations of nickel chromium Dental Casting alloys
    Journal of Applied Biomaterials, 1994
    Co-Authors: Joel D. Bumgardner, L C Lucas
    Abstract:

    In this study, the corrosion and surface properties of four commercially available nickel-chromium Dental Casting alloys, were evaluated using electrochemical corrosion testing and Auger electron microscopy. The corrosion tests were conducted under cell culture conditions of 5% CO2 humidified atmosphere at 37°C in minimum essential medium (MEM) balanced salt solution, 95% MEM–5% FBS (fetal bovine serum) cell culture media, and in 95% MEM–5% FBS media after cold solution sterilization of test samples. The results of the surface and corrosion analyses were correlated to cytotoxicity and metal ion release from the alloys using agarose overlay and direct contact cell culture tests. The surface and electrochemical corrosion analyses demonstrated that the non-beryllium containing alloys were more resistant to accelerated corrosion processes as compared to the beryllium-containing alloys. All alloys demonstrated decreased corrosion rates in cell culture solutions after cold solution sterilization treatment. The corrosion products released from the nickel-based alloys failed to alter the cellular morphology and viability of human gingival fibroblasts, however they did cause reductions in cellular proliferation. The potential for accelerated corrosion and the exposure of local and systemic tissues to elevated levels of corrosion products raises concerns over the biocompatibility of these alloys. © 1994 John Wiley & Sons, Inc.

C H Lloyd - One of the best experts on this subject based on the ideXlab platform.

  • 31p solid state mas nmr spectroscopy of the compounds that form in phosphate bonded Dental Casting investment materials during setting
    Dental Materials, 2007
    Co-Authors: S N Scrimgeour, John A Chudek, George A Cowper, C H Lloyd
    Abstract:

    Abstract Objectives To use 31 P solid-state MAS-NMR to determine which compounds form in phosphate-bonded Dental Casting investment material during setting, when the ambient temperature is altered. To determine whether they differ in material originating at the center of the mix from material that adheres to the mixing bowl wall. Methods 1 H high powered decoupled (HPDC) and 1 H cross polarized (CP) 31 P solid-state MAS-NMR spectroscopy were used at a resonance frequency of 121.4 MHz to determine molecular structure. Four commercial products were examined. Manufacturer's instructions were followed and special liquid used without dilution. Ambient temperature was between 18 and 37 °C. Results Molecular structures change with ambient temperature and product. Amorphous Mg 3 (PO 4 ) 2 or struvite dominate with newberyite, cattiite, amorphous Mg 2 P 2 O 7 and amorphous MgHPO 4 present as minor phases. Exceptionally, amorphous MgHPO 4 dominates. Differences in structure were found in material taken from the center of the mix compared with that scraped from the bowl wall, but the incidence may be specific to the product/mixer combination and not a general effect. Significance The formation of compounds in phosphate-bonded investment can be affected by ambient temperature. This effect and the use of material adhering to the bowl wall (instead of that from the center of the mix) are possible causes for the unpredictability of setting expansion measurements between laboratories. There is variation between products. When phosphate-bonded investment is required for Casting, a consistent ambient temperature must be used and it would be wise to mix sufficient material to avoid scraping the bowl.

  • the determination of phosphorus containing compounds in Dental Casting investment products by 31p solid state mas nmr spectroscopy
    Dental Materials, 2007
    Co-Authors: S N Scrimgeour, John A Chudek, C H Lloyd
    Abstract:

    Abstract Objectives To use 31 P solid-state MAS-NMR to determine the phosphorus compounds that occur in Dental Casting investment material: (a) as-received, (b) after setting and (c) after burn-out and discover whether such compounds are the same in each material across a product range. Methods { 1 H} High powered decoupling (HPDC) and { 1 H} cross-polarization (CP) 31 P solid-state MAS-NMR spectroscopy at a resonance frequency of 121.4 MHz were used. Six commercial products were examined. Manufacturer's instructions were followed and a special liquid was used without dilution. Results All products contain ammonium dihydrogen phosphate as the acid phosphate required for the setting reaction. All set by the formation of struvite and significant amounts of amorphous magnesium orthophosphate. In three products, lesser amounts of newberyite were present and in another the equivalent amorphous compound was formed. When burnt-out, magnesium metaphosphate or pyrophosphate was the dominant matrix compound. A higher burn-out temperature favoured pyrophosphate formation. Farringtonite was present to a lesser extent with the metaphosphate. Significance Compounds that were not detected in earlier X-ray powder diffraction spectroscopy studies were detected by NMR, notably amorphous and glassy compounds (magnesium orthophosphate in set investment and magnesium metaphosphate in burnt-out material). The variation between products was significant and far greater than expected from the published scientific literature. Since the formation of compounds is affected by technical procedure and ambient conditions, these findings could offer some insight into the cause of the unpredictability of expansion measurements between laboratories. Further research is being undertaken.

Her-hsiung Huang - One of the best experts on this subject based on the ideXlab platform.

  • effect of chemical composition of ni cr Dental Casting alloys on the bonding characterization between porcelain and metal
    Journal of Oral Rehabilitation, 2005
    Co-Authors: Her-hsiung Huang, M C Lin, Tzuhsin Lee, Huiwen Yang, F L Chen, C C Hsu
    Abstract:

    summary  The purpose of this study was to investigate the influence of chemical composition of Ni-Cr Dental Casting alloys on the bonding behaviour between porcelain and metal. A three-point bending test was used to measure the fracture load of alloy after porcelain firing. A scanning electron microscope, accompanied by an energy dispersion spectrometer, was used to analyse the morphology and chemical composition of the fracture surface. An X-ray photoelectron spectrometer and glow discharge spectrometer were used to identify the structure and cross-sectional chemical composition, respectively, of oxide layers on Ni-Cr alloys after heat treatment at 990 °C for 5 min. Results showed that the oxide layers formed on all Ni-Cr alloys contained mainly Cr2O3, NiO, and trace MoO3. The Ni-Cr alloy with a higher Cr content had a thicker oxide layer, as well as a weaker bonding behaviour of porcelain/metal interface. The presence of Al (as Al2O3) and Be (as BeO) on the oxide layer suppressed the growth of the oxide layer, leading to a better porcelain/metal bonding behaviour. However, the presence of a small amount of Ti (as TiO2) on the oxide layer did not have any influence on the bonding behaviour. The fracture propagated along the interface between the opaque porcelain and metal, and exhibited an adhesive type of fracture morphology.

  • effect of chemical composition of ni cr Dental Casting alloys on the bonding characterization between porcelain and metal
    Journal of Oral Rehabilitation, 2005
    Co-Authors: Her-hsiung Huang, Huiwen Yang, F L Chen, Shihching Wu
    Abstract:

    : The purpose of this study was to investigate the influence of chemical composition of Ni-Cr Dental Casting alloys on the bonding behaviour between porcelain and metal. A three-point bending test was used to measure the fracture load of alloy after porcelain firing. A scanning electron microscope, accompanied by an energy dispersion spectrometer, was used to analyse the morphology and chemical composition of the fracture surface. An X-ray photoelectron spectrometer and glow discharge spectrometer were used to identify the structure and cross-sectional chemical composition, respectively, of oxide layers on Ni-Cr alloys after heat treatment at 990 degrees C for 5 min. Results showed that the oxide layers formed on all Ni-Cr alloys contained mainly Cr2O3, NiO, and trace MoO3. The Ni-Cr alloy with a higher Cr content had a thicker oxide layer, as well as a weaker bonding behaviour of porcelain/metal interface. The presence of Al (as Al2O3) and Be (as BeO) on the oxide layer suppressed the growth of the oxide layer, leading to a better porcelain/metal bonding behaviour. However, the presence of a small amount of Ti (as TiO2) on the oxide layer did not have any influence on the bonding behaviour. The fracture propagated along the interface between the opaque porcelain and metal, and exhibited an adhesive type of fracture morphology.

  • surface characterization of passive film on nicr based Dental Casting alloys
    Biomaterials, 2003
    Co-Authors: Her-hsiung Huang
    Abstract:

    Abstract Surface characterization of passive film formed on different NiCr-based Dental Casting alloys in an acidic artificial saliva was investigated by using electrochemical impedance spectroscopy (EIS) measurement and potential decay test. The polarization resistance ( R p ), which is inversely proportional to corrosion rate, of passive film was obtained from the EIS data. The stable passive current density, passivating rate, and passivity decay rate of passive film were evaluated by potential decay test. Surface chemical analyses of passive film were performed by using X-ray photoelectron spectrometer and Auger electron spectrometer. Results showed that the R p , stable passive current density, passivating rate, and passivity decay rate, respectively, were significantly different among the various NiCr-based alloys ( p 2 O 3 ) and Mo (maximum 10–11 at%; mainly as MoO 3 ) contents in the passive film led to a higher R p , lower stable passive current density, faster passivating rate, and lower passivity decay rate. The presence of Be (>20 at%; mainly as BeO) in the passive film was detrimental to both the corrosion resistance and the stability of passive film. The presence of small amount of Ti ( 2 ) in the passive film did not show any influence on the characterization of passive film.

  • surface characterization of passive film on nicr based Dental Casting alloys
    Biomaterials, 2003
    Co-Authors: Her-hsiung Huang
    Abstract:

    Abstract Surface characterization of passive film formed on different NiCr-based Dental Casting alloys in an acidic artificial saliva was investigated by using electrochemical impedance spectroscopy (EIS) measurement and potential decay test. The polarization resistance ( R p ), which is inversely proportional to corrosion rate, of passive film was obtained from the EIS data. The stable passive current density, passivating rate, and passivity decay rate of passive film were evaluated by potential decay test. Surface chemical analyses of passive film were performed by using X-ray photoelectron spectrometer and Auger electron spectrometer. Results showed that the R p , stable passive current density, passivating rate, and passivity decay rate, respectively, were significantly different among the various NiCr-based alloys ( p 2 O 3 ) and Mo (maximum 10–11 at%; mainly as MoO 3 ) contents in the passive film led to a higher R p , lower stable passive current density, faster passivating rate, and lower passivity decay rate. The presence of Be (>20 at%; mainly as BeO) in the passive film was detrimental to both the corrosion resistance and the stability of passive film. The presence of small amount of Ti ( 2 ) in the passive film did not show any influence on the characterization of passive film.

  • Effect of chemical composition on the corrosion behavior of Ni-Cr-Mo Dental Casting alloys.
    Journal of Biomedical Materials Research, 2002
    Co-Authors: Her-hsiung Huang
    Abstract:

    The objective of this investigation was to study the compositional influence on the corrosion behavior of Ni-Cr-Mo Dental Casting alloys in acidic artificial saliva. Cyclic potentiodynamic and potentiostatic tests were used to evaluate the corrosion behavior of different Ni-Cr-Mo Dental Casting alloys in deaerated artificial saliva with pH 5 at 37°C. Optical microscope observations were made following the cyclic potentiodynamic tests. Surface chemical analyses were characterized by X-ray photoelectron spectroscopy and auger electron spectroscopy following the potentiostatic tests. The results show that the corrosion resistance of the Ni-Cr-Mo Casting alloys investigated is associated with the formation of passive film containing Ni(OH)2, NiO, Cr2O3, and MoO3, on the surface. The pitting potential and passive range, respectively, were statistically different among the different Ni-Cr-Mo alloys. The Ni-Cr-Mo alloys with higher Cr (≈21%) and Mo (≈8%) contents had a much larger passive range in the polarization curve and were immune to pitting corrosion due to the presence of high Cr (maximum ≈31–35%) and Mo (maximum ≈12%) contents in the surface passive film. The presence of Ti lower than 4% in the Ni-Cr-Mo Casting alloy had no effect on corrosion resistance. A pitting resistance equivalent (PRE) of about 49 could provide the Ni-Cr-Mo alloy with a good pitting corrosion resistance. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 458–465, 2002; DOI 10.1002/jbm.10080

Emma Louise Mcginley - One of the best experts on this subject based on the ideXlab platform.

  • biocompatibility effects of indirect exposure of base metal Dental Casting alloys to a human derived three dimensional oral mucosal model
    Journal of Dentistry, 2013
    Co-Authors: Emma Louise Mcginley, Gary P. Moran, Garry J P Fleming
    Abstract:

    Abstract Objectives The study employed a three-dimensional (3D) human-derived oral mucosal model to assess the biocompatibility of base-metal Dental Casting alloys ubiquitous in fixed prosthodontic and orthodontic dentistry. Methods Oral mucosal models were generated using primary human oral keratinocyte and gingival fibroblast cells seeded onto human de-epidermidised dermal scaffolds. Nickel–chromium (Ni–Cr) and cobalt–chromium (Co–Cr) base-metal alloy immersion solutions were exposed to oral mucosal models for increasing time periods (2–72 h). Analysis methodologies (histology, viable cell counts, oxidative stress, cytokine expression and toxicity) were performed following exposure. Results Ni-based alloy immersion solutions elicited significantly decreased cell viability ( P P P P P  > 0.4755) or cellular toxicity ( P Conclusions Although the multiple analyses highlighted Ni–Cr base-metal alloy immersion solutions elicited significantly detrimental effects to the oral mucosal models, it was possible to distinguish between Ni–Cr alloys using the approach employed. The study employed a 3D human-derived full-thickness differentiated oral mucosal model suitable for biocompatibility assessment of base-metal Dental Casting alloys through discriminatory experimental parameters. Clinical significance Increasing incidences of Ni hypersensitivity in the general population warrants serious consideration from Dental practitioners and patients alike where fixed prosthodontic/orthodontic Dental treatments are the treatment modality involved. The novel and analytical oral mucosal model has the potential to significantly contribute to the advancement of reproducible Dental medical device and Dental material appraisals.

  • influence of s mutans on base metal Dental Casting alloy toxicity
    Journal of Dental Research, 2013
    Co-Authors: Emma Louise Mcginley, Gary P Mora, Adam H Dowling, Garry J P Fleming
    Abstract:

    We have highlighted that exposure of base-metal Dental Casting alloys to the acidogenic bacterium Streptococcus mutans significantly increases cellular toxicity following exposure to immortalized human TR146 oral keratinocytes. With Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), S. mutans-treated nickel-based (Ni-based) and cobalt-chromium-based (Co-Cr-based) Dental Casting alloys were shown to leach elevated levels of metal ions compared with untreated Dental Casting alloys. We targeted several biological parameters: cell morphology, viable cell counts, cell metabolic activity, cell toxicity, and inflammatory cytokine expression. S. mutans-treated Dental Casting alloys disrupted cell morphology, elicited significantly decreased viable cell counts (p < 0.0001) and cell metabolic activity (p < 0.0001), and significantly increased cell toxicity (p < 0.0001) and inflammatory cytokine expression (p < 0.0001). S. mutans-treated Ni-based Dental Casting alloys induced elevated levels of cellular toxicity...

  • influence of s mutans on base metal Dental Casting alloy toxicity
    Journal of Dental Research, 2013
    Co-Authors: Emma Louise Mcginley, Adam H Dowling, Gary P. Moran, Garry J P Fleming
    Abstract:

    We have highlighted that exposure of base-metal Dental Casting alloys to the acidogenic bacterium Streptococcus mutans significantly increases cellular toxicity following exposure to immortalized human TR146 oral keratinocytes. With Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), S. mutans-treated nickel-based (Ni-based) and cobalt-chromium-based (Co-Cr-based) Dental Casting alloys were shown to leach elevated levels of metal ions compared with untreated Dental Casting alloys. We targeted several biological parameters: cell morphology, viable cell counts, cell metabolic activity, cell toxicity, and inflammatory cytokine expression. S. mutans-treated Dental Casting alloys disrupted cell morphology, elicited significantly decreased viable cell counts (p < 0.0001) and cell metabolic activity (p < 0.0001), and significantly increased cell toxicity (p < 0.0001) and inflammatory cytokine expression (p < 0.0001). S. mutans-treated Ni-based Dental Casting alloys induced elevated levels of cellular toxicity compared with S. mutans-treated Co-Cr-based Dental Casting alloys. While our findings indicated that the exacerbated release of metal ions from S. mutans-treated base-metal Dental Casting alloys was the likely result of the pH reduction during S. mutans growth, the exact nature of mechanisms leading to accelerated dissolution of alloy-discs is not yet fully understood. Given the predominance of S. mutans oral carriage and the exacerbated cytotoxicity observed in TR146 cells following exposure to S. mutans-treated base-metal Dental Casting alloys, the implications for the long-term stability of base-metal Dental restorations in the oral cavity are a cause for concern.

  • base metal Dental Casting alloy biocompatibility assessment using a human derived three dimensional oral mucosal model
    Acta Biomaterialia, 2012
    Co-Authors: Emma Louise Mcginley, Gary P Mora, Garry J P Fleming
    Abstract:

    Abstract Nickel–chromium (Ni–Cr) alloys used in fixed prosthodontics have been associated with type IV Ni-induced hypersensitivity. We hypothesised that the full-thickness human-derived oral mucosa model employed for biocompatibility testing of base-metal Dental alloys would provide insights into the mechanisms of Ni-induced toxicity. Primary oral keratinocytes and gingival fibroblasts were seeded onto Alloderm™ and maintained until full thickness was achieved prior to Ni–Cr and cobalt–chromium (Co–Cr) alloy disc exposure (2–72 h). Biocompatibility assessment involved histological analyses with cell viability measurements, oxidative stress responses, inflammatory cytokine expression and cellular toxicity analyses. Inductively coupled plasma mass spectrometry analysis determined elemental ion release levels. We detected adverse morphology with significant reductions in cell viability, significant increases in oxidative stress, inflammatory cytokine expression and cellular toxicity for the Ni–Cr alloy-treated oral mucosal models compared with untreated oral mucosal models, and adverse effects were increased for the Ni–Cr alloy that leached the most Ni. Co–Cr demonstrated significantly enhanced biocompatibility compared with Ni–Cr alloy-treated oral mucosal models. The human-derived full-thickness oral mucosal model discriminated between Dental alloys and provided insights into the mechanisms of Ni-induced toxicity, highlighting potential clinical relevance.

  • Development of a discriminatory biocompatibility testing model for non-precious Dental Casting alloys
    Dental materials : official publication of the Academy of Dental Materials, 2011
    Co-Authors: Emma Louise Mcginley, Garry J P Fleming, Gary P. Moran
    Abstract:

    Abstract Objectives To develop an enhanced, reproducible and discriminatory biocompatibility testing model for non-precious Dental Casting alloys, prepared to a clinically relevant surface finishing condition, using TR146 oral keratinocyte cells. Methods Comparative biocompatibility was determined following direct and indirect exposure of TR146 cells to two nickel–chromium (Ni–Cr) and a cobalt–chromium (Co–Cr) alloy-discs. The surface roughness of the discs was determined using a contact stylus profilometer and the elemental ion release by inductively coupled plasma mass spectrometry (ICP-MS). Subsequent biocompatibility analysis included cell morphology, cell density measurements with Trypan blue exclusion assay, inflammatory cytokine expression with ELISAs, cellular metabolic activity using XTT and cellular toxicity using lactate dehydrogenase (LDH) release assay. Results TR146 cell morphology was altered following direct and indirect exposure to the Ni–Cr alloys but not the Co–Cr alloy. Significant reductions (all P ® 15 alloy compared with d.Sign ® 10 alloy were identifiable (all P Discussion Nickel ions from the Ni–Cr alloys permeated the epithelial cells and activated a proinflammatory response, namely IL-1a, IL-8 and PGE2 expression. Further evidence of nickel ioninduced cell death was supported by the decreased biocompatibility of the highest nickel ion releasing alloy (d.Sign ® 15 compared with d.Sign ® 10) and the increased biocompatibility of the Co–Cr (d.Sign ® 30) alloy where nickel ions were absent.