NDSO/Elite Flyer - Spring 2020 - 19

Impression Accuracy
Goes Beyond the Perfect Margin
There is no doubt that precise models of the prepared and opposing

arches, properly articulated and mounted, give the lab technician the
greatest potential for a successful indirect restoration that satisfies the
patient's specific requirements for form, function, and esthetics. Accurate
and stable final impressions of the preparations are a necessity; the
opposing arch impression must contain the finest detail of anatomy and the
articulation of the upper and lower models requires a precise and stable
bite registration that must seat within the prepared arch and opposing
model without interference. Adhering to this principle, single crown and
cases with two adjacent crowns have been successfully restored using a
dual-arch impression technique for many years. This technique provides
the laboratory with a quadrant impression of the prepared arch, a bite
registration, and a highly accurate quadrant impression of the opposing
arch... all in one stable combined impression. Of course, the practitioner
must exercise caution as to which indirect cases are suitable to this
technique. For instance, the number of units involved should not exceed
two adjacent crowns, although, some rare cases of small three-unit bridges
may be suitable for the dual-arch impression technique. Additionally, the
crown should not be on the terminal tooth of the arch.
The dentist must carefully consider the materials used in a dual-arch
impression so that the final restoration is an exact fit on the prepared tooth
and in functional occlusion. For starters, the tray must be stable throughout
the impression procedure, regardless of the occlusal forces placed on it
through the patient closing into the impression material, as well as during
the removal of the impression intraorally. Any distortion, no matter how
slight, may result in an ill-fitting restoration requiring adjustments in order
to be functional. Plastic dual-arch impression trays are elastic in nature.
The mere force of the patient biting into the tray material, with or without
NEW
hard or soft tissue impingement, may cause the tray to twist or flex. Upon
removal from the mouth, the plastic tray will instinctively return to its
original shape. This will lead to distortion of the final impression that is
indiscernible to the naked eye. Tray stability throughout the impression
procedure is paramount to a highly accurate final impression. For many
years, the metal Quad-Tray® Xtreme, from Clinician's Choice, has provided
dentists with the support and stability necessary for highly accurate
dual-arch impressions. Made from rigid aluminum, the Quad-Tray Xtreme
is memory-free, preventing any chance of impression distortion as it will
simply not flex when placed and the occlusion is registered, maintaining its
accuracy through to removal from the mouth.

a wide arch width that accommodates arches with mal-aligned
teeth. However, their dead-soft, aluminum construction enable the arch
width to be narrowed to fit virtually any arch size. The low sidewalls of the
Quad-Tray Xtreme further avoid palatal impingent and axial roll of the tray
wall, both of which can cause impression distortion. The extended mesh of
the Quad-Tray Xtreme helps in accurately capturing up to four teeth while
longer arches can benefit from the Quad-Tray XL. Even the variability of
the retro-molar pad is taken into account with the thin distal bar of the
Quad-Tray Xtreme, ensuring patient comfort and preventing distortion due
to retro-molar pad impingement.
The tray material chosen for the dual-arch technique is also vital for
providing the laboratory with a stable, accurate impression. Along with
the choice of metal versus plastic tray, dual-arch impressions attain a great
deal of their dimensional stability from the rigidity or hardness of the tray
material itself. The best choice would be a tray material designed to be
as rigid as possible, yet displaying the ideal flow that will not displace the
light body from the preparation. However, the accuracy of the impression
material is moot if it becomes dislodged in any way from the tray upon
removal from the teeth. For optimal dimensional stability, the upper and
lower aspects of the tray material should actually be connected buccal and
lingually to form a monobloc of impression material. The low sidewalls of
the Quad-Tray Xtreme easily allows this to occur. The perforated, slotted
and tapered walls of the Quad-Tray XL both lock-in the tray material and
allow the monobloc to form at either end of the tray. In addition, the
narrow walls of the Quad-Tray Xtreme have retentive bars that help lock in
tray material, providing further prevention of material dislodgement.

Ultimately, the success of your dual-arch impression technique will be
determined at the crown insertion appointment. The degree to which
you have to adjust the crown proximally, internally, and occlusally
will determine how accurate and dimensionally stable your dual-arch
impression is. As mentioned previously, simple visual inspection of
The Bluewave™️ Soft Tissue Diod
the impression upon removal of the mouth will not reveal any level of
lets you perform many soft tissu
distortion. Since chair time is our most valuable resource, simply reviewing
procedures with virtually no blee
your dual-arch technique and careful selection of tray and tray material can
post-operative swelling or disco
result in significant time savings and a superior quality
restoration.
powerful 5W laser is completely

Light the way to
surgical accuracy

allowing for over three hours of
rechargeable lithium-ion battery
Dr. Douglas Harvey is a consultant in Clinical
a surgical instrument or for nonAffairs with Clinician's Choice Dental Products.
laser-assisted periodontal and hy
He has a Bachelor's Degree in Biology ('84) and
therapy - the Bluewave is a vers
The choice of quadrant impression tray must also be wide enough and
a Doctor of Dental Surgery ('88),
both
from thefor your ever
intuitive
instrument
long enough to fit most cases, yet adaptable to fit the myriad of quadrant
University of Western Ontario.
He
served
a
features threeas
pre-programmed
lengths, widths, and tooth position scenarios. As such, the adjusted tray
dental officer at the Canadian
National
Defence
(debride,
perio,
and
cut) and one
has to be comfortable enough for the patient to endure the setting time.
headquarters before enjoying
a career
solo light produc
unique
blueinguiding
There can be no painful hard or soft tissue impingement that may alter
general practice until 2015. Dr.
Harvey
a and bloo
contrast
onhas
oralbeen
tissues
the patient's ability to occlude in the appropriate manner throughout the
long-standing member of the
International
Dental
traditional red beam, for increas
Soft Tissue Diode Laser (791-0668)
impression procedure as this would surely have a negative impact onBluewave
the
Study Club, and has served in organized dentistry
at the local
accuracy
and and
efficiency. The Blu
final impression and as a result, the final restoration. Many plastic trays
Please contact
your Henry
provincial
levelsSchein
in Canada.
an inexpensive, versatile, easy-to
have a narrow occlusal table. This may lead to hard tissue interferenceAccount
from Manager for more information.
laser that's suitable for your enti

a tooth that is either in linguo- or bucco-version. The interference
will decrease the accuracy of the bite registration element through
burn-through and possibly distortion of the dual-arch impression. Metal
Quad-Tray Xtreme, Quad-Tray® XL, and the Anterior Quad-Tray® X2 all have

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NDSO/Elite Flyer - Spring 2020

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