How to Fabricate an 11-Unit Zirconia Bridge Using

How to
Fabricate an 11-Unit
Zirconia Bridge Using
a Manual Milling System
Case Study
Restorative Challenge
A female patient lost teeth #2-5, 7, 10
and 13 to dental caries and periodontal disease. She presented with a faulty
11-unit bridge with open margins, a
reduced occlusal vertical dimension
and faulty pontic design, especially in
the areas of teeth #10 and 11 (Figures
1 and 2). She wanted a more esthetic
and functional bridge.
Restorative Team
Alexander Kanotscher, CDT, owner,
Zahnprofi in Braunau/Inn, Austria
and Dr. Wolfgang Koller from Scharding, Austria.
After the faulty bridge was
removed and the teeth re-prepared, a temporary bridge was fabricated. This case was challenging, as the center line between the upper
and lower anterior teeth didn’t match and the
patient presented with asymmetry of the upper
lip.
Dr. Koller sent the impressions to Zahnprofi
where stone models were fabricated (Figure
3). Using the Zirkograph 025, Kanotscher
milled a trial framework made from a sturdy
light-cured resin on the articulated working
model.
The benefit of milling a trial framework is that
all the necessary adjustments can be made to
the resin framework and then it can be exactly
replicated in zirconium, saving material costs
and reducing the need for remakes. Kanotscher
gave special attention to the condylar paths to
ensure proper function and created a cuspsupported substructure to ensure a uniform
thickness of ceramic to prevent fractures.
He returned the framework to Dr. Koller for a
try-in and provided removable acrylic facings
for verification of esthetics and phonetics (Figure 4). These facings are easy for the dentist to
use and can be adjusted chairside using traditional grinding equipment or added to with a
light-cured polymer at try-in. Internal corrections of individual abutments can be made,
edges checked and a bite registration taken
with the plastic framework in situ.
Dr. Koller returned the adjusted resin framework and bite registration to the laboratory
(Figures 5 and 6). Kanotscher inserted the
resin framework into the Zirkonzahn milling
unit. Using a single blank of zirconia in the
appropriate size for the case, Kanotscher copy
milled the case (Figures 7 and 8). The five-axis Zirkograph 025 enabled him to mill out the
11-unit framework as one piece with excellent
detail. To compensate for the shrinkage of the
zirconia during sintering, the Zirkograph 025
automatically increases the size of the coping
during milling.
Treatment Plan
Kanotscher and Dr. Koller decided
to build an 11-unit zirconia bridge
to replace teeth #4-14; tooth #4 was
included in the bridge as a cantilever
crown and teeth #2 and 3 were not restored. The bridge would be processed
and milled using the Zirkograph 025
manual zirconia milling system from
Zirkonzahn.
The patient presented with a faulty
11-unit bridge.
Pontic areas of teeth #10 and 11 were defective
and the patient’s smile was asymmetrical.
Stone model of newly prepared
abutment teeth.
Acrylic framework for try-in with removable
plastic acrylic facings that can be used to verify
esthetics and phonetics.
The milling process took Kanotscher about 90
minutes. After he was done, he removed the
zirconia structure from the system and dipped
it into an A3 color liquid. The structure then
was pre-dried under an infrared light and sintered (Figure 9).
Lab Management Today November/December 2008
Although an overlay of veneering porcelain is
optional, it was used in this case for better preservation of opposing natural dentition since
the zirconium is so hard. The dentist placed the
final bridge and verified that it was fully seated
using radiographs.
Both the dentist and the patient approved the
esthetics and final shade of the bridge before it
was cemented. The patient is very pleased with
the esthetic results, especially because there’s
no metal margin, blue discoloration to the gingival or shadows. (Figures 10-13).
Kanotscher’s
Buying Decision
Bite registration taken in cement.
The edges of the crowns are checked
for accuracy.
The resin coping in the template disk.
Like many laboratory owners, Alexander Kanotscher, CDT, owner of Zahnprofi in Braunau/
Inn, Austria, began outsourcing zirconia copings and frameworks to respond to client demand. After outsourcing for three years, his
outsourcing costs began to rise and he started
looking for a zirconia milling system to gain
more control over his product in his four-person laboratory.
In February 2005, Kanotscher purchased
Zirkonzahn’s Zirkograph 025 milling system
developed by owner Enrico Steger of South Tyrol, Italy. It’s a manually operated, copy milling system that can fabricate zirconia crowns,
bridges up to 14 units, dowel crowns, posts
and cores, long-term temporary appliances, inner telescopes, anchor and attachment work,
Maryland bridges and implant superstructures. It can mill all types of preparations and,
because of its five-axis milling, it can handle
bridges with diverging abutments.
Since purchasing the system, Kanotscher’s lab
has increased its sales by 20% each year and it’s
now an outsource provider for other laboratories. “I like the manual aspect of the system because I can offer a precise zirconia restoration
without being dependent on expensive equipment and I don’t have the corresponding maintenance costs. Also, I like the control I have
with the system,” says Kanotscher.
The sintered bridge.
Alexander Kanotscher, CDT, owner, Zahnprofi,
mills the bridge using the 5-axis Zirkograph 025.
Material Values of
ZirkonZahn’s ZrO2
Bending strength of Zr02: 1200 Mpa
(in comparison, the bending strength
of glass ceramic is 100-200 Mpa)
Palatal view of the bridge mounted
on the stone model.
Buccal view of the bridge mounted
on the stone model.
Hardness: 1250 Vickers
Fracture Toughness: 10-12 Weibull
Radioactivity measurements:
Zr02 single unit: 0.3 Bq
Facing ceramic: 1 Bq
Adult human body: 6,000 Bq
Contents for this article
provided by Zirkonzahn
The bridge cemented in patient’s mouth.
The patient is very pleased with
the esthetic results of her new bridge.
Zirkonzahn introduced the Zirkograph 025
manual milling system to the U.S. market in
2007. The system price starts at $5,425; if you
have additional questions, call 800-989-8931
or 678-441-9419, e-mail [email protected]
com or visit www.zirkonzahn.com.