Cross-polarization optical coherence tomography (CP-OCT) is a promising imaging modality to detect demineralization under the margins of composite restorations. The aim of this study was to assess how base materials applied under composite resin may affect CP-OCT image assessment. Base materials are commonly used for managing deep dentinal decay but once applied residual amounts of the base materials can be inadvertently left on the inner enamel walls. This study determined that base materials have significantly different scattering properties. The order grouping in the mean backscattered reflectivity (mR) of the base material was Dycal>caries phantom>Fuji IX, Vitrebond, Fuji II (p<0.05). The calcium hydroxide base (Dycal) had a higher mR than demineralized dentin and Vitrebond before and after the resin restoration was placed (p<0.05). While calcium hydroxide maybe a confounder in CPOCT imaging, several protective base materials are compatible with this type of imaging modality.