Keywords
ceramics - crowns - veneers - try-in
Introduction
A try-in session is an important part of any esthetic rehabilitation case. It allows
both the practitioner and the patient to assess the restorations in terms of fit,
shape, and color. Statically, it is possible for the dentist to assess those parameters
with regular try-in paste. However, it is reported in the literature that assessing
the restorations dynamically when in function is an important process.[1] During the try-in session, the patient should be able to evaluate the restorations
when smiling and speaking. The dentist needs to assess these parameters to evaluate
speech and esthetics. In addition, assessment of the occlusion prior to cementation
should be performed to minimize post cementation adjustments in the ceramics. With
regular try-in paste, these are not possible due to the low viscosity of most commercial
try-in cements. This low viscosity causes the veneers to be dislodged immediately
as the patient bites or performs any dynamic movement. For this reason, in most cases
bite adjustments are still performed after cementation. This has a detrimental effect
on the quality of the finalized restorations caused by loss of the high gloss layer
on the surface of the ceramic material. Surface roughness and microcracks will develop
on the surface due to adjustments performed after cementation.[2] These adjustments often require subsequent intraoral polishing; However, the ceramic
surface smoothness will not be on par with laboratory grade glaze. It is reported
in the literature that surface microcracks will cause significant decrease in the
strength of ceramic veneers, and therefore it is recommended that all bite adjustments
to be performed during the try-in session to allow for a final laboratory glaze fire.[3]
Try-in pastes are fabricated with the primary concern that the optical properties
of the paste should be identical to those of the cement. The viscosity and adherence
power during the cementation are not given adequate attention by companies and the
commercially available products are “water-runny” try-in pastes. Clinicians who utilize
these try-in pastes experience the frustration of the crowns and more importantly
veneers constantly falling off in the try-in session due to the low viscosity of the
paste. Therefore, many clinicians attempt “non-academic” techniques for allowing the
restorations to stay in place. These include the use of petroleum oil jelly “Vaseline”
or other commercial nondental glue sticks such as “UHU.” These practices have no basis
in the literature and are used by clinicians at their own risk. Concerns should be
raised regarding petroleum jelly due to the fact that these oils leave residues on
the intaglio surface of the restorations that could adversely affect bonding.[4] The disadvantage of using glue sticks “UHU,” on the other hand, is their unestablished
safety. These products were not intended for intraoral applications and their use
for this purpose should be backed up by published evidence stating absence of cytotoxicity
of such materials. Due to the preceding problems, the authors suggest the use of a
polymerizable soft resin similar to that used as gingival dam material in bleaching
treatments ( Liquidam, Discus Dental; Philips Oral Healthcare, Stamford, CT, United
States) ([Fig. 1]). These resins are proven safe for intraoral use due to their long history in dental
applications.[5]
[6]
[7]
[8] In addition, these resins polymerize immediately and provide a soft interphase that
locks the crowns or veneers in place, but makes removal an easy process with a dental
explorer leaving no residues since the resin is removed as a single film ([Fig. 2]).
Fig. 1 Soft polymerizable resin (Liquidam).
Fig. 2 Frontal smile view of the patient.
Case Report
A 34-year-old patient presented to the outpatient clinic at Beirut Arab University
seeking esthetic treatment. Patient’s main concern was the multiple spacing and discoloration
of the teeth. Medical and dental history was collected. Case was planned after radiographic
and photographic assessment. Smile design was performed and patient had mock-up session
prior to any preparation. After gaining approval from the patient, guided preparation
was performed and veneers were fabricated. After verifying the fit of the restorations
without any paste, the teeth were kept moist without excessive drying. One drop of
Liquidam was placed on intaglio surface of the restorations. It was placed labially
to avoid locking and facilitate easy removal. The crown or veneer was not filled with
Liquidam paste; only pea-sized drop was placed. The restorations were then placed
with even pressure for complete seating and polymerized for 10 seconds using an LED
curing unit. Dynamic try-in was performed and patient was asked to smile and talk
without the fear of having the restorations fall off. Patient was asked to bite as
well, and bite adjustments were performed. After completion of the try-in, the tip
of a probe was inserted under the margin for removal. The Liquidam film was removed
from the intaglio surface of the restoration as a single film ([Fig. 3]). The intaglio surface was later sandblasted and cleaned with water and steam pressure.
Fig. 3 Peeling off the Liquidam paste as a single film after try-in.
Discussion
In this case, the ceramic utilized was monolithic lithium disilicate (IPS e.max CAD
HT; Ivoclar-VivadentAG, Schaan, Liechtenstein) ([Fig. 4]). The preoperative condition shows moderate discoloration and multiple spacing between
the teeth ([Fig. 2]). Despite the nonretentive nature of the preparations ([Fig. 5]), the restorations did not fall off during the try-in due to the locking power of
the Liquidam. Bite adjustment was also one of the prominent advantages in this technique
since in traditional try-in, when the patient bites the restorations move out of place
and therefore, most clinicians keep the bite adjustments till after the cementation.
This is not a recommended practice since it causes loss of the ceramic glazed surface,
increases surface flaws, and decreases ceramic strength.[9] Using this technique, occlusion marks left by articulating carbon paper were easily
visualized on the cast and adjusted prior to final glaze because the restorations
were not dislodged intraorally during dynamic try-in ([Fig. 6]). Therefore, post-cementation bite adjustments are avoided. Patient was also able
to smile wide, and pronounce various letters and practice speech allowing for the
concept of dynamic try-in to be applied.
Fig. 4 Photograph showing the ceramic restorations used.
Fig. 5 Retracted view of teeth and respective preparations with retraction cord.
Fig. 6 Marks left by articulating paper after dynamic try-in of restorations.
To compare the shade matching of traditional try-in paste and soft polymerizable resin,
regular try-in paste was used in the left quadrant and Liquidam was utilized in the
right quadrant to assess possible color differences ([Fig. 7]). Upon visual and electronic assessment using a clinical spectrophotometer (Easyshade
V, VITA Zahnfabrik, Bad Sackingen, Germany), no color difference was recorded between
the side with Liquidam and the side with regular try-in paste. For thinner ceramics,
care must be taken as Liquidam might not replicate the optical properties of the cement
used, notice the color difference between the regular try-in paste on the left and
the Liquidam on the right ([Fig. 8]). In case of ultra-thin ceramics, it is recommended after the resin try-in to reconfirm
color matching using a regular commercial try-in paste that is respective to the resin
cement to be used for the final cementation.[10] It could be arguable that the film thickness of Liquidam is higher than the try-in
paste or the cement; This is clinically irrelevant at the try-in stage if there is
complete seating of the restoration. The micron scale difference in film thickness
plays an important role in the quality of the final cementation and the authors argue
that it does not affect the fitting of the restorations during try-in. The seating
could be confirmed using high magnification assessment of the margins of the restorations
with a dental explorer under microscopes or utilizing macro dental photography. Despite
of that, the advantages of using Liquidam for temporarily holding the restorations
in place during try-in outweigh its limitation of use.
Fig. 7 Dynamic try-in of restorations showing regular try-in paste (left side) and Liquidam
(right side).
Fig. 8 Regular try-in paste left) (Liquidam to the right).
Conclusion
Soft polymerizable resin is useful for try-in of crowns and especially veneers lacking
mechanical retention. Restorations fitted with Liquidam will not fall off during the
try-in session as the patient smiles, speaks, or bites. It could be removed easily
with the tip of a probe and the polymerized resin could be removed from the fitting
surface as a single film without leaving any residues. Care must be taken, however,
with thin veneers for color reproducibility.
