Abstract. This study aimed to investigate whether swept source optical coherence tomography (SS-OCT) could estimate the lesion depth and mineral loss quantitatively without the use of polarization sensitivity, and to examine a relationship between OCT data and transverse microradiography (TMR) lesion parameters. Twenty-four bovine root dentin specimens were allocated to three groups of 4-, 7-, and 14-day demineralization. Cross-sectional images of the specimens before and after the demineralization were captured by OCT at 1319 nm center wavelength. Following the demineralization, these specimens were cut into sections for TMR analysis. Correlations between the OCT data and TMR lesion parameters were examined. TMR images of the specimens showed cavitated lesions (lesion depth or LD TMR : 200 to 500 μm, Z or mineral loss: 10,000 to 30,000 vol % μm). The OCT images showed "boundaries," suggesting the lesion front. Integrated dB values before and after the demineralization and their difference (R D , R S , and R, respectively) were calculated from the lesion surface to the corrected depth of boundary (LD OCT ). A statistically significant correlation was found between LD OCT and LD TMR (p < 0.05, r = 0.68). Similarly, statistically significant correlations were found between Z and R D or R. The OCT showed a potential for quantitative estimation of lesion depth and mineral loss with cavitated dentin lesions in vitro. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).