In recent years, the all-ceramic restoration
has become the restoration of choice whenever
possible. This was primarily brought about
by the developments of resin luting cements
and dentin bonding agents.6 Coupled with
these are the before-mentioned reinforced
porcelain systems. The
success of the bonded restorations are well-documented
and studies do agree on the exceptional
effectiveness of this modality in both functional
and esthetic treatments.
Second, low firing temperatures allow
a better, more stable, natural color format.
The translucency is not clouded, opalescence
is true to the ceramic and not a metallic
oxide fritting.9 Light dispersion is very
natural and similar to tooth structure.
Third, the homogenous and extremely dense
nature of this ceramic material makes it
easy to grind, and it polishes extremely
well. This softer porcelain is unique in
that all test results indicate it is "most
like natural enamel" in functional
wear properties.9 This creates a much less
abrasive occlusal surface and enhances periodontal
tissue health.
In our laboratory. Low Fusing Ceramic is
utilized to encase ceramo-metal and all-ceramic
restorations as per the manufacturer's recommendations.
I have been very im pressed with the results
of this new material. If the laboratory
testing does extrapolate into every day
clinical results, I perceive it to be the
restoration of choice among the discerning
dentists of tomorrow.
Although there are many porcelain systems
on the market today, no system should be
expected to be all-encompassing. Some systems
function and/or appear different under certain
circumstances."' Thus the integrity
and talent of the ceramist-technologist
will always be the critical factor in our
pursuit of excellence.
Pursuant to this cooperative goal of naturally
beautiful and functional smiles is good
communication between the dental office
and laboratory. Visual communications are
perhaps the most convenient to use and best
convey details and the expectations of the
patient and doctor. Photographs, laboratory
prescriptions, computer imaging, color mapping,
study models, or videos are tools of necessity
to obtain optimum clinical results.
The following cases incorporate the before
mentioned materials along with some of these
ideas.
This patient expressed a strong interest
in remaking a poorly constructed porcelain
to metal restoration on tooth #8, (non-vital)
which had been completed just a few months
prior. He also expressed a strong desire
to close the diastema between #8 and #9,
correct the rotated appearance of ft 7,
and create a better overall color and contour
harmony in the maxillary anterior region.
At this point, photographs and study models
were taken.
It was concluded that in order to reduce
anterior stresses, slight coronal plasty
w^ould be done on the mandibular lat erals
and central and veneers would be made for
teeth #7 and #9, along with the replacement
of #8 with an all-ceramic restoration. This
conservative approach proved to produce
good results in restoring proper colors
and contours.
An initial enamel reduction of 0.5 mm was
done using a LVS-1 Brasseler diamond bur.
The remaining facial bulk enamel was reduced.
Final preparations included a tape ing chamfer
that extended to the edge of the retracted
gingiva on each veneer. Tooth #9's preparation
did not
break the distal contact and a lingual margin
was established. Toward the mesial lingual,
the margin was again brought down to the
retracted gingiva to provide for the mesial
emergence profile. Tooth #7 was prepared
in much the same fashion; slightly more
reduction was made to the mesial facial
lobe for a more ideal contouring of the
veneer. Tooth #8 had previously been prepared
and only minor changes were made to "clean
up" the margins.
With the retraction cord in place on #7
and #9, the second cord on #8 was removed,
and a polyvinylsiloxane impression was taken
along with an
opposing arch. I was called to the office
to determine the shades to be utilized.
First, I wanted to closely match the adjacent
prepared teeth in color
and the degree of opacity exhibited bv ff7
and 9 at the same depth. A previously fabricated
shade tab was used, consisting of a 1:1:1
ratio of B-2, D-2, and D-3 opacious dentin,
and it was mixed with a 20% 1:1:1 ratio
of B-2, D- 2, and D-3 dentin." It was
determined that this should be used to build
up &8 and that a D-2 shade, plus a slight
ochergingival tone and an opal incisal halo
would blend in well.
Model and Die Work
Models and dies along with a soft tissue
model were prepared. The dies were trimmed
under a 10X stereo microscope. The dies
are painted with a removable varnish to
allow about 35
microns space for resin. All saw cuts were
then blocked out and an impres-
sion was made with Express STD (vinylpolysiloxan).
The refractory
material was then mixed, vibrated into place,
and allowed to set for 45 minutes. The cast
was then removed and trimmed that it might
be incorporated in an Accu-Trac tray with
additional refractory material and allowed
to dry. The tray and refractory are then
separated, sectioned, and trimmed to facili
tate the ease of handling and access to
the interproximal margins.
The dies are placed in the oven at about
400 degrees C to eliminate ammonia
from the refractory that otherwise would
severely contaminate the porcelain. The
margins are then marked and fired to place.
The "cure" bake
(stabilization and expansion) is performed
at 980 degrees C. The second
bake is that of a wash-bake nature at 925
degrees C to adhere the porcelain
into the micro porosities of the refractory
material itself; thus the porcelain
will not separate or pull away from the
die due to "porcelain creep" upon
vitrification. I believe these first two
firings are crucial for three reasons:
the tray, condensed, fired at 500 Degrees
C to 915 degrees C at a six
minute rise under vacuum, and then air fired
at 915 degrees C for 1 minute.
First, to insure intimate margin adaptation;
second, a well condensed and
homogenous internal surface; third, establish
basic color tones. Next, I set out the porcelain
palate. Remember, I want to build up #8
to mimic somewhat the prepared teeth #7
and #9. This was done and fired into place.
The corresponding shades were mixed to follow
the prescription. First a D-2 plus a slight
amount of ocher porcelain modifier was placed
on the cervical margins and a basic D-2
dentin build up was made along with the
D-2 +1 /4 B-l dentin that was also prescribed.
A vertical segmental layering was applied
with very little mammalon development. An
incisal 50 and 51 were used along with a
thin overlay of window, and opal incisal
was added to form a whitish halo effect.
Each was then removed fromthe tray, condensed,
fired at 500
Degrees C to 915 degrees C at a six minute
rise under vacuum, and then
air fired at 915 degrees C for 1 minute.
Contour and Glazing
The restorations were contoured to close
the diastema and correct the rotation on
#7. All surfaces were then layered with
LFC transparent and fired. Slight surface
texture was done with a med.-coarse diamond
point, and a final LFC glaze was done. The
contacts were checked, and the veneers and
all porcelain restorations were separated
from the refractory via Al
0 (25 micron) at 30 Ibs. psi.
They were each tried on the master dies
and model. A slight contact adjustment and
a slight margin overhang on the lingual
of #8 was refined. All margins were checked
for correct contours. Any adjustments at
this point were done with a white rubber
wheel and polished with diamond paste. Each
was etched and silanated and delivered to
the doctor for placement.
The patient's primary complaint and reason
for seeking treatment was that
#8 and #9 were too broad, and lighter in
value than her smaller-than-normal,
grey-appearing laterals. The yellow chroma
of the cuspids was stronger than any of
her remaining teeth. Isolated bleaching
was performed on #7 and #10 along with a
full lower bleaching treatment. At this
time a photo was taken for laboratory communication.
The teeth were prepared and another photo
was taken to show the color and density
of color along with other char acterization
of the remaining tooth structure.
Polychromatic Layering of Porcelains
Porcelain placements consisted of a 1:4
mixture ofB-2 Opacous Dentin and B-2 Dentin,
plus a touch of light yellow (to bump up
the chroma and value slightly). The basic
B-2 Dentin layer was verv thin and interspersed
with a B-l lobe here and there. It was then
brushed back from the labial incisal 1/3
of the build up. Then a vertical segmental
incisal placement was done alternating a
1:2 ratio mix of window (clear), and [ncisal
50 (light blue-grey), with a 1:2 ratio mix
of window (clear), and Incisal 51 (light
grey), and a touch of T-5 (polar blue).
Each build-up was removed. Enamel shaded
contact areas were placed. The porcelain
was condensed with vibration and moisture
removal (tissue blot technique), then fired
from 500 degrees C to 915 degrees C in 6
minutes vacuum with a 1 minute air fire
at 915 degrees C.
Although this technique of multiple building
and firing is more time consuming, it offers
a system of checks and balances relative
to the location of final crown contours,
colors, and the appearance of enamel depth
that looks natural.
Contour and Glazing
After firing the veneers, contacts were
adjusted, final contours were established,
and surface texture completed. The margins
were also finished at this time.
An initial glaze was done with LFC glaze
at which time a light opal halo was placed
on each restoration and a few light to moderate
decalcification (white) areas were added.
Note: LFC stains are a fitted porcelain
and metal oxide composition and not a metal
oxide only. Thus they do not wear off or
leach out as many conventional stains do
over 4-7 years.9 When staining, a double
glaze is a good idea with strong merit.
A second LFC glaze was done, and the veneers
are removed from the refractory via Al 0
(25 micron) and 30 Ibs. psi. Each was etched
and silanated for delivery.
Conclusion
This new single-phase hydrotherrnal dental
ceramic, coupled with sound techniques and
polychromatic layering will create superior
esthetic results. The physical properties
and wear characteristics most closely match
that of natural dentition of any tooth colored
restorative available. You can ensure vour
patients function and esthetics for years
to come.
