A system for scanning a dental arch of a patient includes a reference element having a reference pattern thereon a holding mechanism configured to hold the reference element in a fixed position inside the patients oral cavity adjacent to and spaced from the dental arch, wherein the holding mechanism is configured to be installed on the patient without contacting an occlusal surface of the dental arch and an intra-oral scanner configured to scan the dental arch and an adjacent portion of the reference element to obtain a scanned image comprising the scanned portion of the dental arch and the scanned adjacent portion of the reference pattern.
