title: Influence of S. mutans on base-metal dental casting alloy toxicity.
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.
authors.affiliation: Materials Science Unit, Dublin Dental University Hospital, Trinity College Dublin, Ireland.
authors.forename: E L
authors.initials: EL
authors.lastname: McGinley
authors.forename: A H
authors.initials: AH
authors.lastname: Dowling
authors.forename: G P
authors.initials: GP
authors.lastname: Moran
authors.forename: G J P
authors.initials: GJ
authors.lastname: Fleming
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry / Q000633:toxicity; D002452:Cell Count; D018929:Cell Culture Techniques; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002858:Chromium Alloys / Q000737:chemistry / Q000633:toxicity; D003722:Dental Alloys / Q000737:chemistry / Q000633:toxicity*; D003734:Dental Casting Investment / Q000737:chemistry / Q000633:toxicity; D015232:Dinoprostone / Q000032:analysis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D053582:Interleukin-1alpha / Q000032:analysis; D016209:Interleukin-8 / Q000032:analysis; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D008422:Materials Testing; D008670:Metals / Q000737:chemistry / Q000633:toxicity; D009532:Nickel / Q000737:chemistry / Q000633:toxicity; D012995:Solubility; D013054:Spectrophotometry, Atomic; D013295:Streptococcus mutans / Q000502:physiology*; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
chemical_list: D001672:Biocompatible Materials; D002858:Chromium Alloys; D003722:Dental Alloys; D003734:Dental Casting Investment; D053582:Interleukin-1alpha; D016209:Interleukin-8; D008670:Metals; D014409:Tumor Necrosis Factor-alpha; D009532:Nickel; D015232:Dinoprostone