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.

Streptococcus mutans adhesion and releasing of metallic ions in dental alloys

“…The atomic absorption spectrophotometer indicated that the values of ions release for Cu/Al alloy were significantly affected by exposure to S. mutans. This was also observed by the study of McGinley et al 14 who assessed the influence of S. mutans on dental alloys' toxicity and observed that ions release significantly increased in the presence of these bacteria, as it leads to pH reduction. On the other hand, MutluSagesen et al 22 stated that pH reduction is directly related to the great ions release by dental alloys.…”

Cobalt-chromium alloys in dentistry: An evaluation of metal ion release

“…All specimens were polished with silicon carbide paper (400, 800, 1200 grit) with a grinder-polisher machine (M2V; Manfredi). The specimens were than cleaned in ethanol and deionized water in an ultrasonic cleaner for 5 minutes to remove contaminants and finally autoclave-sterilized as previously reported by Xin et al 42 and McGinley et al 17 Three solutions were prepared in order to evaluate chemical corrosion following the study by Mutlu-Sagesen et al 30 Three solutions were prepared to evaluate biocorrosion: a solution of 50% artificial saliva (pH 7.1), 45% tryptic soy broth (TSB; Oxoid) and 5% defibrinated horse blood (SS+B; Oxoid); a solution of 50% artificial saliva buffered with H3PO4 at pH 5.5, 45% TSB (SigmaAldrich) and 5% defibrinated horse blood (SS+AB; Oxoid); and a solution of 50% artificial saliva (pH 7.1), 45% TSB (Oxoid), and 5% defibrinated horse blood (Oxoid) added with 5 × 10 6 cells/mL E. corrodens (SS+BB). One sample of artificial saliva/TSB blood was adopted as blank reference.…”

“…9-12 The oral environment is an ideal place for corrosion because of the presence of saliva, acid bacterial plaque, changes in pH and temperature related to food or beverage intake, and the action of different medications. [13][14][15][16][17] The possibility of local alterations and the degree of severity at which they happen can be directly related to the alloy type and chemical state of the metal, the concentration, and the time of contact with mucosal tissues. 4,5 Base metal dental prostheses with monophasic alloys are less cytotoxic and inhibit human cell growth less than those with polyphasic alloys.…”

“…However, bacterial development of microbial corrosion on dental alloy requires the adhesion of bacteria to the surface, which also depends on characteristics. 17,31 Retention of oral microorganisms on cobaltchromium alloys has been described, but the possible effect of specific bacteria on biocorrosion processes is still unclear. 32 Eikenella corrodens, a facultative gram-negative bacillus, is a common inhabitant of the oral cavity.…”

A novel coping metal material CoCrCu alloy fabricated by selective laser melting with antimicrobial and antibiofilm properties

“…ACCEPTED MANUSCRIPT 11 and cause local symptoms, such as mucositis or even carcinogenicity and mutagenicity [40][41][42][43][44].…”