Pore Size and Surface Charge Analysis of Decalcified Human Enamel

Objectives: The aim of this study was to utilize Atomic Force Microscopy (AFM) to quantify changes in surface pore size and charge of sound and decalcified enamel. This will further facilitate the design of novel biodegradable nanoparticles to distinguish between active and inactive carious lesions and simultaneously deliver, after penetration into the lesion, potential therapeutics to arrest and remineralize these lesions. The nanoparticles need to be the right size to penetrate into, and the correct charge to adhere to, the subsurface of the carious lesions to facilitate their effectiveness.
Methods: AFM was used to quantitate pore size and surface charge of sound enamel on extracted human teeth, and subsequently, pore size and surface charge of the same enamel surfaces after incipient lesion formation using carboxymethylcellulose gel. Electric Force Microscopy was used to determine the surface charge, while non-contact mode AFM was be used to generate topographical images of the enamel samples. The software used to analyze the surface charge and topographic AFM data was SPIP^® (Scanning Image Probe Processor) 4.5 software from Nanosensors.
Results: We found that the average pore size of demineralized enamel is approximately 450nm ± 600nm, which is significantly greater than mineralized enamel. Additionally, it was determined that the surface of carious lesions is more negatively charged than mineralized enamel.
Conclusions: Our findings confirmed that active carious lesions have larger microscopic pores and a more negative surface charge compared with sound enamel. This gives insight on how to better design diagnostic and therapeutic compounds for penetration into lesions without surface modification. The data from this study has provided the framework for developing a novel nanomaterial, for the diagnosis, using fluorescence, and simultaneous treatment of active carious lesions. Ultimately, this will allow dental practitioners to employ truly non-invasive caries management techniques in their practice.