A system comprises an intraoral scanner to generate intraoral images of a dental site, and a computing device. The computing device is configured to: receive an intraoral image comprising a depiction of a first tooth; determine a contour of the first tooth in the intraoral image; select a portion of the intraoral image that is within the contour of the first tooth; lock the portion of the intraoral image that is within the contour of the first tooth; and generate a 3D model comprising the first tooth and one or more other intraoral objects based at least in part on the intraoral image and one or more additional intraoral images, wherein the locked portion of the intraoral image is used for the first tooth in the 3D model.