Introduction: Polarization sensitive optical coherence tomography (PS-OCT) and near-IR imaging are promising new technologies under development for monitoring early carious lesions. Fluorosis is a growing problem in the U.S., and the more prevalent mild fluorosis can be visually mistaken for early enamel demineralization. Some initial near-IR images suggest that enamel defects and dental caries manifest different optical behavior in the near-IR. Unfortunately, there is little quantitative information available regarding the differences in optical properties of sound enamel, enamel development defects, and demineralized enamel due to caries. Objective: This study tested the hypothesis that hypomineralized enamel due to fluorosis can be differentiated from demineralized enamel due to caries using near-IR and PS-OCT imaging because of different optical behavior in the near-IR. Methods: Thirty extracted human teeth with various degrees of suspected fluorosis and/or caries were imaged using PS-OCT and near-IR transillumination. An InGaAs camera and a near-IR diode laser were used to measure the optical attenuation through transverse tooth sections (~200um). The sections were then imaged with high-resolution digital microradiography to assess the volume percent mineral loss for correlation with the scattering changes measured in the near-IR at 1310-nm. Results: Developmental defects were clearly visible in the polarization-resolved OCT images, demonstrating that PS-OCT can be used to nondestructively measure the depth and possible severity of the defects. Enamel defects that could be imaged with high contrast with visible light were transparent in the near-IR while demineralized areas due to caries were opaque. In contrast, dental caries could be clearly distinguished from sound enamel. Conclusions: This study suggests that PS-OCT and near-IR methods may potentially be used as tools to assess the severity and extent of enamel defects and for the differentiation of mild fluorosis defects from early carious lesions. Support: This work was supported by NIH grants T32-HDO52275-01 and R01-DE14698

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