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Complete Denture Dent and (PowerPoint)

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  • pg 1
									Custom Trays: The Key




         to a
Great Final Impression
                      Patient Visit #2
                                     Visit 2
                 Clinical                                 Lab.
                procedure                               procedure


Evaluation of final
                        Border molding     Boxing/Pouring           Master casts
 impression trays


                        Final impression                        Record Bases



                                                                Occlusal Rims
                  Outline
• Over view of border molding & making a
    final impression.
•   Make custom trays on the preliminary cast.
       Outline the tray borders on the cast.
       Block out the undercuts.
       Apply the relief wax.
       Place & shape the Triad resin material.
       Cure the resin.
       Adjust the tray.
        Border-Molding

Definition: Shaping of an impression
 material by the manipulation or
 action of tissues adjacent to the
 borders of an impression tray
Objective:
 To determine the contours, height
 and width of the borders of the
 complete denture
Custom trays are constructed prior
to the final impression appointment.
                     Why?
 Stock trays are universal. They are not made to
fit a specific patient‟s mouth.
 Stock trays are difficult, if not impossible, to
adjust to fit a patient‟s mouth.
 The most accurate impression is one that has an
even thickness of impression material.
 Custom trays require a minimum amount of
impression material.
 Requirements of a custom tray:

 They must be rigid so as not to distort the
impression.
 They must be able to be adjusted to fit the
patient‟s mouth.
 The tray handles must not interfere with the
border molding process.
 The tray must allow for an even thickness of
impression material.
      How to make a custom tray:

   Draw the outline on the cast.
   Block out the undercuts.
   Place the wax spacer on the cast.
   Place the Triad on the cast.
   Mold the Triad into the proper shape.
   Cure the tray in a curing oven.
   Trim the tray.
   Cut back the wax.
     Draw the outline on the cast




  Since alginate impressions in stock trays will always leave
the vestibular areas over-extended, an outline is drawn 2 mm
short of periphery in the labial and buccal vestibular areas to
arbitrarily define the borders of the tray until they are
adjusted to fit the mouth. The line is left long in the
posterior palate and the retromolar pad areas to allow the
impressions to capture the soft tissues in these areas.
         Block out the undercuts




  Major undercuts on the preliminary cast are blocked out
with wax before the impression tray is made. This is
necessary so that the tray can be inserted in the mouth
without chafing the soft tissue and be removed from the
master cast once the final impression is made and poured in
yellow stone.
  Place a wax spacer on the cast




  A piece of wax is dipped in a hot water bath or heated
over a Bunsen burner to soften it uniformly. One layer of
warm baseplate wax is pressed into place over the maxillary
cast with the thumb and finger pressure. It is trimmed along
the external borders of the land area by pressing it against
the sharp external edge of the cast.
     Trim the wax to the outline




1 thickness of baseplate wax is cut back 2 mm from the
depth of the vestibule. The dark line that was scribed on
the cast should be visible through the wax and provide an
easy guide as to where the cut needs to be made. It should
be easily visible after the wax is removed from the cast.
The same basic procedures described for the making a
maxillary tray also apply to the mandibular tray. The wax is
pressed into the lingual area first and then the buccal and
labial areas, and cut by pressing the wax against the outer
border of the land area. The wax is trimmed to the line
marked on the cast at 2 mm from the depth of the buccal and
labial vestibules. The wax is left long over the retromolar pad
and lingual flange areas, but does not extend onto the land
area.
   Trim the wax to the outline




  The wax is left a little long in the posterior palate and
retromolar pad areas to allow the tray to be constructed
long in these areas and permit recording the posterior
palatal area where the palatal seal will be formed and
the retromolar pad, which is the most stable support
area of the mandibuar ridge. The areas over all frenum
attachments are relieved to the 2mm distance to allow
for full movement of the lip.
       Place the Triad on the cast




  One thickness of Triad tray material is placed onto the wax. It
is pressed into the lingual area (mandibular) or palatal area
(maxillary) first to prevent air pockets from forming, then
pressed over the ridge and buccal areas. It is pinched off at
the edge of the land area and cut along the edge of the lingual
vestibule with a red handled knife to remove this section.
      Place the Triad on the cast




The Triad is pressed into the internal border of the land area
with the thumbnail to form the external border of the tray.
This is done around the entire border of the cast.
              Add a tray handle




  A handle is molded onto the tray. It must arise from the
crest of the ridge in the anterior of the tray and should be
at a 45o angle to the crest of the ridge. It must be just
long enough to accommodate the width of the thumb. This
will allow sufficient access for the border molding to be
accomplished in this area by allowing the lip to be pulled
along the surface without binding. It also provides enough
surface area for the tray to be securely held while placing
and removing it during the impression procedures.
              Add a tray handle




  The handle for the lower tray is made longer and narrower
than the one made for the upper tray. This allows the tongue
to move freely around it and perfect the border molding in
the lingual area. Finger rests are placed on the crest of the
posterior ridges that are narrower than the width of the tray
to raise the finger above the area that is being border-
molded and to prevent recording the width of the finger in
the final impression. Sufficient distance must be provided
between these and the handle for the tongue to pass through.
 Cure the Triad in the curing oven




  The tray is cured on the cast in a curing unit for three
minutes. It is removed from the cast and placed in the curing
unit with the waxed side up for an additional two minutes. A
quick look will show where the Triad material extends beyond
the wax.
  The thumb is placed on the handle to determine if there
is sufficient thickness and length of the handle to allow
adequate grasp for the tray to be placed and removed
during the impression procedure.
                Trim the tray




The wax is allowed to cool, then the tray material is
trimmed back to the level of the wax spacer. A lathe will
speed up the process and a handpiece can be used to
refine the cutback. A laboratory diamond is especially
made for this task and will greatly reduce the time spent
adjusting the Triad.
  After the tray borders
have been reduced and the
tray has been finished, it
is placed back on the cast
to verify that it has been
sufficiently cut back 2 mm
short of the vestibule to allow
for sufficient bulk of the
border molding compound.
                 Cut back the wax




  An additional 2mm of wax is removed from the inside of the
tray to allow the border molding material to overlap the edge of
the tray and form a U-shaped joint. This joint will be strong
enough to firmly retain the compound on the tray. A few
millimeters of wax is also removed from the posterior palatal
area to allow for the palatal seal to be developed in the final
impression.
This „U‟-shaped joint will provide sufficient strength to
the compound so that it doesn‟t fracture off during
the border-molding or impression phases.
  The tray is tried into the patient‟s mouth and the
borders are reduced 2 mm short of the depth of the
vestibules and the frenuli attachments. This is determined
by pulling the lip outward and having the patient raise the
tongue. This assures that there is sufficient room for
the border-molding,
  Custom trays are border-molded with dental compound (also
known as modeling plastic) prior to making a final impression.
This material softens with heat and hardens at mouth
temperature, allowing several adjustments to record the
vestibular areas very accurately.
  The impression is then just a thin “wash” of polysulfide
impression material over the compound-modified custom tray.

								
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