Page 22 - DT Vol 13 No 2

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22 cosmetic section DENTAL TECHNOLOGY, APRIL-JUNE 2023

A CHALLENGING ANTERIOR CASE SOLVED

IN AN AESTHETIC WAY

Reconstruction of natural incisors is a challenging task. A case becomes particularly difficult
when dentin discoloration and/or a root post are involved. In these cases, the dental technician
must choose a material mix that ensures not only reliable layering, but also a natural play of color
and light. In the following case report, MDT Show Yamamoto shows how such clinical situations
can be resolved successfully with Vita YZ zirconium oxide and Vita VM 9 veneering ceramic. The
clinical treatment and intraoral photographs were provided by Dr. Takuya Yada of Tokyo, Japan.

INITIAL SITUATION AND TREATMENT PLANNING
A patient presented to the dental office with the wish of restoring
#21 with a single crown. The color and characterization of the
apparently nonvital tooth, which was layered onto a metal frame-
work, was obviously not in harmony with the adjacent dentition.
The metal margin of the crown was visible in the cervical area
and was only partially covered by direct composite material
(Figure 1). A partial silicone impression was taken for the chair-
side fabrication of a temporary crown. After removal of the defec-
tive crown, discolored dentin and a metal post abutment were
exposed (Figure 2). No secondary caries was detected. The radi-
ographs showed sufficient endodontic treatment and no periapi-
cal inflammation.
To mask the discoloration and the root post, a zirconium oxide
framework using Vita YZ T Color and a gloss level of LL1 was
used to layer the feldspathic Vita VM 9 fine-structure ceramic
veneer to create a natural play of shade and light. The base color
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of the tooth was determined for the chairside fabrication of a F FIG 1: Starting situation with defective 21metal-ceramic crown
temporary crown. The Vita Linearguide 3D-Master was used to
determine the dentin shade (Figure 3), and the Vita Toothguide
3D-Master was used to determine the enamel shade. (Figure 4).
The temporary crown was fabricated direct at chairside using a
self-curing composite and silicone matrix, was provisionally
cemented and the excess removed.
DETERMINATION OF SHADE AND FABRICATION OF THE STRUCTURE
The exact determination of the tooth shade is an essential step in
the aesthetic reproduction of ceramics for anterior teeth. The
tooth shade was digitally determined using the Vita Easyshade
spectrophotometer V, with measurements taken in the cervical,
middle and incisal thirds of the adjacent incisor (Figures 5 and
6). Shade results were documented with a digital camera to pro-
vide the dental technician with as much information as possible
for the reproduction of the ceramic (Figures 7 and 8). The char-
acteristics and internal structures of the teeth were visualized
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using the Cross Polar-eyes polarization filter which eliminates F FIG 2: After removing the crown: discolored dentin and a metal abutment post
reflections (Figure 9). After removing the temporary crown, the
color was documented again with Vita Linearguide 3D-Master in
two systematic steps and with a digital camera.
Since it was difficult to place the color samples horizontally,
these were placed at an angle of 105° near the adjacent incisor
(Figures 10 to 12). "I think the combination of visual and dig-
ital improves the accuracy of the final shade selection," says MDT
Yamamoto, emphasizing the importance of this step.
Finally, 3M2 was chosen as the shade base. Impressions were
taken of the maxillary arch with the prepared root and of the
antagonist. The shape of the zirconium oxide framework was
determined by wax-up on the master model and then fabricated
in Vita YZ TColor using CAD/CAM (Figure 13). After sintering,
Vita Akzent Plus Body Stain was sprayed onto the zirconium
oxide coping. With firing, a rough surface was created for
optimal reproduction of the shade base of the tooth (Figures 14 F FIG 3: Determining the base shade of dentin with

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and 15). Vita LinearGuide 3D Master