*Review* **Quantitative Assessment Methods of Early Enamel Caries with Optical Coherence Tomography: A Review**

**Boya Shi 1,2,\*, Jiaxin Niu 1,2, Xinyue Zhou 1,2 and Xiaoyang Dong 1,2**


**\*** Correspondence: shiboya@tiangong.edu.cn

**Abstract:** Early detection of caries is an urgent problem in the dental clinic. Current caries detection methods do not detect early enamel caries accurately, and do not show microstructural changes in the teeth. Optical coherence tomography (OCT) can provide imaging of tiny, demineralized regions of teeth in real time and noninvasively detect dynamic changes in lesions with high resolution and high sensitivity. Over the last 20 years, researchers have investigated different methods for quantitative assessment of early caries using OCT. This review provides an overview of the principles of enamel caries detection with OCT, the methods of characterizing caries lesion severity, and correlations between OCT results and measurements from multiple histological detection techniques. Studies have shown the feasibility of OCT in quantitative assessment of early enamel lesions but they vary widely in approaches. Only integrated reflectivity and refractive index measured by OCT have proven to have strong correlations with mineral loss calculated by digital microradiography or transverse microradiography. OCT has great potential to be a standard inspection method for enamel lesions, but a consensus on quantitative methods and indicators is an important prerequisite. Our review provides a basis for future discussions.

**Keywords:** optical coherence tomography; early enamel caries; quantitative assessment; quantitative indicators
