2. Learning outcomes
1. Define custom trays and list the
materials for making custom tray.
2. Explain the procedure for making a
custom tray.
3. Define border molding and list the
materials for doing border molding.
4. Define final impressions and list the
materials for making final impressions
and master casts.
3. Patient Visit #2
Visit 2
Clinical
procedure
Lab.
procedure
Evaluation of custom
impression trays
Border molding
Beading & Boxing
& Pouring
the casts
Master casts
Final impression Record Bases
Occlusal Rims
4. Custom tray: an
individualized impression tray
made from a cast recovered
from a preliminary impression.
It is used in making a final
impression.
5. Why Use Custom Trays?
Custom trays provide
anatomically correct extension of
denture impressions.
Allow homogeneous thickness of
impression material.
Provide accuracy.
6. Requirements of a custom tray
a) stability in air and in a moist
environment,
b) volume stability over time,
c) moisture resistance,
d) rigidity,
e) adhesion of the impression material in
the tray and
f) even thickness of impression material.
7. Materials Used for Custom Trays
1. The chemically-cured (CC)
acrylic resin custom tray materials
2. Visible Light-Cured (VLC) resin
custom tray materials
8. The chemically-cured (CC) acrylic resin
custom tray materials have some
disadvantages:
Polymerization shrinkage
A time interval must be allowed between
the fabrication and the use of these custom
trays
The hazardous effects caused by the
monomer (methyl methacrylate) include
dermatologic reactions
9. VLC resin is:
less hazardous,
reduces preparation time,
easy to use and
has good handling properties.
10. Identify Denture Extensions
Mark the anticipated final
extension of the denture in
pencil on the cast
Method of fabrication of a
custom tray
11.
12. Mark Tray Extensions
Mark the tray extension in
pencil about two mm shorter
than the first pencil line except
in posterior palatal seal area.
13.
14. Mark spacer outline
Mark the spacer outline 2 mm
short of the tray outline. Also
mark the tissue stops in canine
(2) and molar (2) region. Spacer
in the posterior palatal seal
should be bow shaped.
15.
16. Why Spacer?
The spacer provides room for the
impression material
It also minimizes the pressure
that could distort the mucosa.
17. Tissue Stops:
1. To orient the tray
2. For uniform thickness of the
impression material
26. When monomer and polymer
are mixed in the proper
proportions, a workable mass
is produced. Upon standing,
the resultant mass passes
through five distinct stages.
31. Handle Design
Functions of handle:
1. Supports the lip while making
impression.
2. Tray handles are particularly
helpful when loading, placing and
orientating custom trays in the
mouth.
34. Finger rests
Finger rests
Finger rests help in holding the
tray in position when making
the final impression.
35. Functions of finger rests
Stabilize tray in mouth
Equal distribution of pressure
Reduces pressure applied to
tissues
36. • The finger rests (arrow) should
not impinge upon the tongue
space and not extend above the
occlusal plane and are placed
near the 2nd
premolar/1st
molar
teeth.
42. Border molding: the shaping of
the border areas of an impression
material by functional or manual
manipulation of the soft tissue
adjacent to the borders to
duplicate the contour and size of
the vestibule.
43. MATERIALS USED FOR BORDER
MOLDING
1. Low fusing compound
2. Putty consistency of elastomeric
impression materials
44. Wax Spacer Removal
After border molding, remove wax
spacer
Do not dislodge border molding
45. Final Impression: the
impression that represents the
completion of the registration of the
surface or object.
also called master impression
Secondary impression ------ not a
good term
46. MATERIALS USED FOR FINAL
IMPRESSION
1. Zinc Oxide Eugenol Impression
Paste
2. Elastomeric Impression
Materials (medium body and
light body)
47. Definitive Cast: a replica of the
residual ridge areas, and/or other
parts of the dental arch used to
fabricate a prosthesis;
also called final cast or master casts
49. Methods of pouring casts
1. Inversion method (for preliminary
casts)
2. Beading and boxing method (for
master casts)
A. Wax boxing method
B. Plaster of paris and pumice
boxing method
53. Land
area
Land Area: the portion of a dental
cast that extends beyond the
impression’s replica surface laterally.
54. Boxing an impression:
The enclosure (box) of an
impression to produce the
desired size and form of the
base of the cast and to
preserve desired details.
56. Advantages of beading and
boxing
Superior hardness of cast surface
Provides land area
Preserves borders of the
impression
Minimizes trimming
57.
58. Pouring of casts
Once beading and boxing is done
pour cast with dental stone (100 gm
of stone to 28-30 ml of water) and
allow it to set for about an hour.
59. Retrieving of casts
After the cast has set, place the tray
with cast in hot water to soften the
low fusing compound and carefully
separate the cast from the
impression.
61. The method we will use is the 1:1
plaster/pumice mixture. Equal parts of
plaster and pumice are mixed together
dry, then enough water is added for the
mix to become smooth and creamy.
H2O
Plaster
Pumice
72. Two types of indexing:
1.Groove indexing method
2.Notch indexing method
73. 1. Groove indexing method
In this method, V- shaped
grooves are made on the cast for
indexing.
74. 2. Notch indexing method
In this method, 3 notches are
placed at the edges of the cast at
its thickest portion.
Notas del editor
Gordon J. Christensen, D.D.S., M.S.D., Ph.D-JADA, May 1994:
(Blatterfein , JPD 1985)
The recommended ratio of plaster to pumice is about 50/50 or 1:1. It is not critical that these components are measured out exactly. All that is necessary, is to produce a mixture that is sufficiently soft to allow easy removal when set, yet sufficiently rigid to support the impression and boxing wax. The plaster and pumice should be mixed together in a powder form prior to adding the water. Only enough water is added to provide a smooth, creamy mix.
The bases are trimmed to allow for about 4mm width in the area that will become the land area.
The box must not leak, therefore, the area where the pieces of the wax box come together must be sealed by adding an additional piece of wax which is left sufficiently long so that it can be folded over the joint area and also sealed to the wax using a hot instrument. A piece of beading wax is then used to seal the box to a plastic slab.
One of the most commonly seen problems that have resulted from undercuts on casts being insufficiently blocked out or insufficiently lubricated prior to making the baseplate Is a broken or marred surface of the cast. This is particularly distressing to the student and patient alike as the entire impression-making procedure must be repeated at another appointment. If a ridge is thin and is expected to possibly break during the constant placement and removal of a baseplate, a good preventive measure is to make an impression of the blocked-out master cast and duplicate it.
