Objectives: The release of low-molecular-mass monomers and/or fragments from polymeric dental resin biomaterials is an area which has recently attracted much interest in view of the potential health hazards presented by these agents. Indeed, components such as methacrylates display a cytotoxic potency, bisphenol A and its derivatives [for example, impurities present in bisphenol A bis[2-hydroxypropyl]methacrylate (Bis-GMA), and degradation product arisings from other resins] exhibit estrogenic activity, and, together with methacrylate, selected organic acid xenobiotics can alter cell metabolism. In this investigation, we have explored the capacity of high resolution proton (¹H) nuclear magnetic resonance (NMR) analysis to determine the molecular nature of such agents in appropriate aqueous media following prolonged equilibration of their parent polymeric biomaterials [Bis-GMA and triethylene glycol dimethacrylate (TEGDM)] therein.

Methods: Increasing quantities (0.00-0.32g) of Bis-GMA and TEGDM were equilibrated in artificial saliva (AS) at 37° C for a period of 28 days. Subsequently, each mixture was centrifuged and the clear supernatant removed for NMR analysis. This procedure was then repeated using doubly-distilled water in place of AS. ¹H NMR spectra were acquired on a Bruker AMX-600 spectrometer, using sodium 3-trimethylsilyl [2,2,3,3-²H₄] propionate (TSP) as a chemical shift reference and quantitative internal standard.

Results: Unique proton signals corresponding to the "parent" monomer units of Bis-GMA and TEGDM were detected in the spectra of supernatants arising from the equilibration of these polymeric resins in AS and doubly-distilled water, together with their degradation products, e.g. bisphenol A mono[2-hydroxypropyl]methacrylate, bisphenol A and methacrylic acid.

Conclusions: High resolution ¹H NMR analysis provides valuable multicomponent molecular information regarding the degradation of dental resins and the release of potentially toxic agents therefrom.

Back to the Dental Materials: V - Polymer Materials-Chemistry Program
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