Deciphering pH Effects on the Peptide-guided Nucleation and Growth of Hydroxyapatite and Peptide-Ion Interactions for Dentin Hypersensitivity Treatment

Thesis (Master's)--University of Washington, 2020With enamel demineralization being a significant factor in the development of dentinal hypersensitivity, it has been an enormous endeavor to restore the enamel. Incorporating a biomimetic approach to tooth repair has been a long-lasting challenge, especially in integrating a newly constructed mineral layer to the molecular structure of the tooth, e.g. enamel and dentin. GEMSEC’s (Genetically Engineered Materials Science and Engineering Center) previous research evaluated the amelogenin-derived peptide sADP5 in guiding the remineralization of enamel and the ability to control the biomimetic mineral layer properties. Not only was remineralization achieved, but mineral integration into the tooth structure was successful in a modeled oral environment. This led to the development of a market introductory remineralizing tooth whitening dental product in the form of a lozenge as a delivery mechanism for remineralization in the oral cavity. This work was only limited to a constant saliva temperature and pH. Saliva pH is variable and dynamic and can alter hydroxyapatite crystal-growth mechanisms. This thesis focused on the unexplored pH effects on the nucleation and growth of the newly formed mineral layer, as well as its effects on peptide characteristics, behavior, and interaction with surrounding ions. The resulting optimal pH for mineralization is used as a testing parameter in the lozenge delivered remineralization approach. Calcium assays were performed to measure the calcium consumption throughout time. Structural characterization was done using a scanning electron microscope (SEM), observing the mineral morphology, thickness, and structural integration. The results suggested that the peptide-guided nucleation and growth of the new mineral on the tooth surface can be controlled with pH. With each application of the remineralizing tooth whitening lozenge, under the pH condition determined in the pH experiments, there were clearly observable increases in the thickness of the newly formed mineral layer. The knowledge developed in this thesis will contribute to the future in everyday dental care products and change the way the oral health care system approaches treatments in periodontal diseases