ABSTRACT
This chapter discusses the use of various agents that can be applied to tooth surfaces to enhance the imaging of caries lesions (tooth decay) and internal structures in teeth at near-infrared (NIR) and short wavelength infrared (SWIR) wavelengths for transillumination and reflectance imaging, with an emphasis on optical coherence tomography (OCT). The refractive indices (RI) of enamel, dentin, and cementum are quite high – 1.63, 1.54, and 1.58, respectively – and surface scattering and specular reflection can interfere with optical penetration into the tooth. Moreover, dental hard tissues are porous structures, and that porosity increases markedly with demineralization and hypomineralization. Filling the porous structure of subsurface caries lesions with a high RI fluid enables better optical penetration through such lesions to better view the underlying tooth structure. The loss of mobile water in sound enamel and dentin or displacement by another fluid profoundly changes light scattering in these tissues and optical penetration. The use of exogenous agents to enhance dental imaging is of increasing interest to the dental community with the introduction of NIR and SWIR transillumination and reflectance imaging methods along with OCT, which exploit the high transparency of dental enamel at longer wavelengths beyond the visible range.
