Systems and methods are described for identifying a sub-gingival surface of a tooth in volumetric imagery data. Shape data is received from a surface scanner and volumetric imagery data is received from a volumetric imaging device. The shape data of the super-gingival portion of a first tooth is registered with the volumetric imagery data of the super-gingival portion of the first tooth to obtain a registration result. At least one criterion is then determined for detecting a surface of the first tooth in the volumetric imagery data of the super-gingival or the sub-gingival portion using the registration result. The surface of the sub-gingival portion of the first tooth is detected in the volumetric imagery data using the at least one criterion.