Abstract
A multicomponent evaluation of the oxidative consumption of salivary biomolecules by a hydrogen peroxide (H2O2)-containing tooth-whitening formulation has been performed using high-resolution proton (1H) nuclear magnetic resonance (NMR) spectroscopy. Unstimulated human saliva samples (n = 10) were treated with aliquots of supernatants derived from 1) the H2O2-containing whitening gel, 2) the corresponding tooth-whitening accelerant solution containing an amino-alcohol activator, and 3) a combination of these product agents pre-mixed in the recommended manner. 600 MHz 1H NMR spectra acquired on these samples demonstrated that H2O2 present in the whitening gel gave rise to the oxidative decarboxylation of salivary pyruvate (to acetate and CO2), the direct oxidation of trimethylamine and methionine (to trimethylamine-N-oxide and methionine sulphoxide respectively), and the indirect oxidative consumption of lactate and carbohydrates in general. Experiments conducted on a chemical model system confirmed the consumption of pyruvate by added H2O2, and also revealed that this method could be employed for determinations of the H2O2 content of tooth-whitening products. In conclusion, high-resolution 1H NMR analysis provides much valuable molecular information regarding the fate of tooth-whitening oxidants in human saliva, and also permits an assessment of the ability of endogenous antioxidants therein to protect against any soft tissue damage arising from the possible leakage of H2O2 from tooth-whitening application trays.
Highlights
IntroductionThe incorporation of hydrogen peroxide (H2O2), carbamide peroxide (CP) and peroxo-adducts of inorganic anions such as peroxoborate, peroxodisulphate and peroxocarbonate as agents for the bleaching of discoloured teeth in commercially-available tooth-whitening products such as gels, toothpastes and oral rinses has evoked much interest regarding their modes of action, redox activity in oral environments, and adverse effects and safety considerations [1,2]
High-resolution 1H nuclear magnetic resonance (NMR) analysis provides much valuable molecular information regarding the fate of tooth-whitening oxidants in human saliva, and permits an assessment of the ability of endogenous antioxidants therein to protect against any soft tissue damage arising from the possible leakage of H2O2 from tooth-whitening application trays
The incorporation of hydrogen peroxide (H2O2), carbamide peroxide (CP) and peroxo-adducts of inorganic anions such as peroxoborate, peroxodisulphate and peroxocarbonate as agents for the bleaching of discoloured teeth in commercially-available tooth-whitening products such as gels, toothpastes and oral rinses has evoked much interest regarding their modes of action, redox activity in oral environments, and adverse effects and safety considerations [1,2]
Summary
The incorporation of hydrogen peroxide (H2O2), carbamide peroxide (CP) and peroxo-adducts of inorganic anions such as peroxoborate, peroxodisulphate and peroxocarbonate as agents for the bleaching of discoloured teeth in commercially-available tooth-whitening products such as gels, toothpastes and oral rinses has evoked much interest regarding their modes of action, redox activity in oral environments, and adverse effects and safety considerations [1,2]. Salivary biomolecules which can act as scavengers of H2O2 (or other peroxo-adducts) serve to protect oral soft tissues against any deleterious effects exertable by these oxidants which are sometimes prone to escape from customised application trays or alternative application devices and make con-. The analysis of salivary biomolecules by conventional methods (for example, those involving gas or high-performance liquid chromatographic techniques) generally requires the time-consuming, labour-intensive determination of pre-selected components. These methods require much information regarding the identities of particular salivary biomolecules prior to analysis, and generally offer only a limited characterisation of the redox reactivity of H2O2 and/or related peroxo-adducts. The development of high-field NMR spectrometers with increased resolution, dynamic range and sensitivity has given rise to rapid advances in the analysis of complex, multicomponent samples such as human biofluids (intact or otherwise), pharmaceutical formulations, dentifrices and ACES
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