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).
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).
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.
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).
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.
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.
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