AFM and CFM Study of the Etiology of Fluorosis

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DESCRIPTION: The effectiveness of fluoride as a Dental preventive agent and public health measure would be increased if the systemic side effects of fluoride could be reduced, no matter what the mode of therapy. The optimal level of fluoride l ppm in drinking water has been established because it gives a reduction of caries of 30-50% without the corresponding increase in Dental fluorosis, although it is known that levels exceeding l ppm would bring about greater reductions in caries. The biological etiology of fluorosis is not understood, although one of the suggested mechanisms is the impaired removal of enamel matrix proteins from enamel surfaces, which impede crystal growth, leading to hypoplastic defects in enamel. This atomic and chemical force microscopy study (AFM and CFM) will describe and compare the binding capacity of fluorotic and non-fluorotic enamel crystals for the well characterized enamel proteins, amelogenin, ameloblastin, enamelin, and their cleavage products. Recent studies have identified charge domains on the enamel crystal surfaces, which appear to affect protein crystal binding to the enamel surfaces. The use of enamel crystals obtained from various stages (secretory, transition and maturation) of enamel development will help identify when charge domains appear on crystal surfaces and when fluoride has major effect on enamel mineralization. Protein binding capacity of both the fluorotic and non-fluorotic enamel crystals will be correlated and compared with the concentration of a phosphate solution needed to strip these proteins from the crystals. The presence of charge domains on the crystal surfaces will be examined by CFM using different chemically modified tips ("functionalized tips"). The role of the charge domains in protein/crystal surface interactions will be investigated. The exquisitely characterized proteins and their cleavage products may help identify the protein motifs involved in the crystal binding. The effect of these proteins on crystal growth will also be examined in the AFM. Single crystal growth has already measured in the AFM. Similar growth measurements will be made in this study, i.e., in crystal length and width; pit or hillock formation will also be assessed. The outcome of this project will not only shed light on the role the enamel matrix proteins play in enamel mineralization, but also offer an explanation for the cause of fluorosis. This explanation may allow therapies or treatments to be devised that will prevent the deleterious effects of fluoride and let it be administered at levels, which will cause a greater reduction in caries.