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Title: Investigating the clinical and laboratory aspects of tooth whitening
Author: Qusti , Najlaa Yusef Mohammed
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2013
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Although bleaching is considered a conservative technique, controversy surrounds whether bleaching demineralises or modifies tooth surfaces. Little is known about how bleaching may predispose enamel to subsequent acid challenges or how it affects the adsorption of protective salivary pellicles. Aim: To investigate the effects of bleaching on: susceptibility of hydroxyapatite to subsequent acid attack; on adsorption of salivary proteins and their protective properties and to carry out an in situ study to investigate the impact of a commercial bleaching product on mineral density of human enamel. Methods: Hydroxyapatite powder bleached in vitro was used to examine the effect of bleaching on: acid solubility; salivary protein adsorption and the protective properties of adsorbed salivary proteins using SDS-PAGE and for protein identification using mass spectrometry. An in situ study, employing extra-oral bleaching, examined the effect of bleaching ' on enamel mineral density as measured by X-ray NanoCT scanning technique. Results: The results indicated that bleaching had no effect on hydroxyapatite acid susceptibility. However, bleaching did affect the adsorption of salivary proteins such as a-salivary amylase. A novel finding was that the precise effect observed was donor specific i.e. salivary protein heterogeneity between individuals dictated how bleaching effected the nature of the adsorbed salivary pellicle. Bleaching appeared to significantly increase the ability of the salivary pellicle to protect hydroxyapatite from acid attack. Increasing the pH of the bleaching agent enhanced subsequent adsorption of the model protein bovine serum albumin. The in situ study indicated that the bleaching regime used here had no significant effect on the inner enamel but Significantly increased mean mineral density at the enamel surface by 6.8%. It is suggested that peroxide incorporates in the hydroxyapatite lattice and modifies mineral properties. Conclusions: Overall, data indicates that the specific bleaching regimes employed here do not have a detrimental effect on mineral density and may actually increase mineral density.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available