Digital Impressions for the Fabrication of Aesthetic Ceramic Restorations

A Case Report

Steven Glassman, DDS

A male patient presented for aesthetic enhancement following the completion of orthodontic treatment, which relieved the crowding of the mandibular incisors, provided a more stable overbite/overjet relationship, and removed an existing edge-to-edge bite (Figure 1). All four first premolars had been extracted prior to conventional orthodontia when the patient was in his early teens (Figure 2).

The original treatment plan included this orthodontic therapy, tooth whitening, and subsequent restoration of teeth #4(15) through #13(25). Teeth #4 and #13 were to be restored will all-ceramic zirconia crowns to replace opaque porcelain-fused-to-metal restorations (PFMs). Teeth #6 through #11, in addition to #23 through #26, were to be conservatively restored with feldspathic porcelain veneers. Following completion of orthodontic treatment (Figure 3), a diagnostic waxup was created from mounted casts (Figure 4). Kois facebow and centric relation bite records were obtained in order to mount the case as precisely as possible and capture occlusal and dentofacial information. The mounted models, along with a series of digital photographs, were forwarded to the dental laboratory in order to create the initial diagnostic waxup. The completed waxup was returned for inspection along with a reduction matrix, prepared models, and a provisional template (Figures 5 and 6).

Following the administration of anesthetic, the relevant case information (ie, patient name, laboratory, number of teeth, type of restoration, material, stump, and shade) was entered into the computer terminal for the digital impression scanner. The preexisting PFMs were removed, and the maxillary teeth were provisionalized after tooth reduction was performed. Tooth preparation for the porcelain veneers was performed according to the reduction guides (Figure 7). Since the teeth were in proper alignment following orthodontic treatment, the preparations were confined to the tooth enamel, with a reduction of 0.3 mm to 0.5 mm on the labial surfaces and approximately 0.1 mm on the incisal edge. Retraction cord was placed subgingivally (Figure 8), which allowed the clinician to refine the preparations without iatrogenic damage to the ginigiva. Following refinement of the chamfer preparations, a second cord was placed and allowed to set for five minutes. A single retraction cord was placed at the veneer preparations, again allowing the clinician to refine and visualize the margins. Since the patient presented with a relatively high lip line, the author elected to keep the margins slightly subgingival. Following an additional five-minute set period, the scanning procedure was initiated.

Scanning for the digital impression was performed with the camera in contact or slightly away from the teeth. Voice prompts indicated when individual tooth scanning and opposing arch scans were necessary. A functional bite registration was taken with the teeth in centric occlusion by positioning the camera horizontally. If any blood or oral fluids seeped into the preparation, the operator removed the camera and allowed the assistant to blow or blot the fluids from the area prior to image capture. If the operator moved the camera during image capture, the digital impression system prompted the author to rescan that particular tooth before proceeding to the next. The scanning process for the entire 12-unit case was competed in less than seven minutes for both arches (Figures 9 and 10).

The patient was provisionalized (Figure 11) and the case was then forwarded digitally to the manufacturer, where the digital information was analyzed. The three-dimensional scan was digitally forwarded from there to the laboratory for approval. Once the scan was deemed acceptable, the digital information was sent to a milling machine, where polyurethane models were created. The finished, articulated models were forwarded to the dental laboratory for fabrication of the definitive restorations. The mandibular veneers were fabricated with feldspathic porcelain, and the full-coverage crowns were fabricated from zirconia.

Throughout this process, the patient was given time to evaluate the aesthetics, phonetics, and function delivered by the provisional restorations. Any necessary adjustments were made and communicated to the laboratory. On the seating appointment, the patient was anesthetized and the provisional restorations were removed. The preparations were cleaned via intraoral sandblasting and chlorhexidine. The definitive restorations were tried in to evaluate fit, contact area, occlusion, and aesthetics. The case was tried in with water-soluble gel, and it was decided that a clear paste would be acceptable. The try-in gel was removed and the veneers were prepared with a phosphoric acid etch, rinsed, cleaned, and coated with a silane material. Following tissue retraction and hemostasis, the veneers and crowns were adhesively bonded in place. Excess cement was removed with use of curved scalpel and discs, and the occlusion was verified. The entire seating appointment, from removal of the provisional restorations to final polishing, was performed in just 10 minutes—including all chairside adjustment (Figure12). The patient was rescheduled for one more follow-up appointment to finalize the occlusion and aesthetics.