Polarized light microscopy (PLM) is an established technique for the inspection of thin tooth sections in dental research. However, conventional PLM is mainly based on the qualitative evaluation of color-dependent birefringence, depolarization and transmittance but lacks a quantitative interpretation and, thus, the comparison with other polarimetric imaging methods. Here, we describe an easy to implement extension of PLM that enables measuring the degree of polarization (DOP). By replacing the analyzer and RGB camera in PLM with a monochrome polarization camera, linear polarization states can be directly determined from the transmitted light. Additionally rotating the polarizer in the illumination path and, by that, the state incident into the sample facilitates reconstructing a DOP image from multiple linear measurements. The resulting depolarization measurements are compared with conventional PLM images as well as X-ray micro-computed tomography (µCT) data of the intact teeth. Our results show that caries and demineralization appear to be directly related to depolarization in enamel. However, the interpretation is more complicated for dentin, which shows a reduced DOP also in sound tissue. We assume that these insights support the development and analysis of future dental polarimetry techniques in vivo, such as intra-oral polarization-sensitive optical coherence tomography (PS-OCT).