CUSTOM TRAYS 302B
WEEK 5
INTRODUCTION:
The topics covered today are:
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Impression Trays
Stock Impression Trays
Advantages of Stock Impression Trays
Disadvantages of Stock Impression Trays
Custom Impression Trays
Advantages of Custom Impression Trays
Types of Impressions and Models
Flow Chart of Impression Trays
Handle Dimensions and Position
Custom Trays 302B – Week 5
Page 1 of 8
Stage 1
IMPRESSION TRAY
A RECEPTACLE OR DEVICE USED TO CARRY
THE IMPRESSION MATERIAL TO THE MOUTH,
CONFINE THE MATERIAL IN APPOSITION TO
THE SURFACES TO BE RECORDED, AND
CONTROL THE IMPRESSION MATERIAL WHILE
IT SETS TO FORM THE IMPRESSION.
THERE ARE TWO TYPES OF IMPRESSION TRAYS:
1. STOCK IMPRESSION TRAY
2. “CUSTOM” IMPRESSION TRAY
“CUSTOM” IMPRESSION TRAYS MAY ALSO BE
CALLED “SPECIAL” OR “INDIVIDUAL” TRAYS.
Custom Trays 302B – Week 5
Page 2 of 8
Stage 1
STOCK IMPRESSION TRAYS
STOCK TRAYS COME IN A VARIETY OF DESIGNS AND
SIZES. THESE TRAYS FALL INTO THREE MAIN TYPES:
FULL DENTATE TRAYS
PARTIALLY DENTATE TRAYS
EDENTULOUS TRAYS
THERE ARE A VARIETY OF SIZES TO SUIT MOST
PATIENTS. STOCK TRAYS CAN BE MADE OF METAL
(NOT DISPOSABLE) OR PLASTIC. THE PLASTIC TRAYS
ARE INTENDED TO BE DISPOSABLE.
ADVANTAGES (METAL STOCK TRAYS)
 DESIGNED TO BE USED MANY TIMES
 MUST BE ABLE TO BE SRERILISED
 USED TO TAKE FIRST IMPRESSION FOR THE
PRODUCTION OF THE PRIMARY CAST
DISADVANTAGES
 THE PROBLEM IN USING STOCK TRAYS IS THAT
THE IMPRESSION MATERIAL IS OF VARIOUS
THICKNESS WHICH CAN LEAD TO DISTORTION
 THE FLOW OF THE IMPRESSION MATERIAL
CANNOT BE GUARANTEED TO COVER ALL THE
AREAS OF THE TEETH OR TISSUES REQUIRED
 PRESSURE POINTS CAN OCCUR WHEN USING A
STOCK TRAY. THE PATIENT CAN EXPERIENCE
DISCOMFORT DURING IMPRESSION TAKING DUE
TO THE LARGE AMOUNT OF IMPRESSION
MATERIAL USED IN THE TRAY. IN ORDER TO
OVERCOME THESE PROBLEMS, SPECIAL TRAY
SHOULD BE CONSTRUCTED.
Custom Trays 302B – Week 5
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Stage 1
CUSTOM IMPRESSION TRAYS
MADE BY A TECHNICIAN FOR AN INDIVIDUAL
PATIENT AND ONLY USED FOR THAT PATIENT.
CUSTOM TRAYS ARE CONSTRUCTED BY THE
TECHNICIAN ON A PRELIMINARY MODEL. THE
MATERIALS WHICH CAN BE USED FOR THE
CONSTRUCTION OF A CUSTOM TRAY ARE AS
FOLLOWS:
1. THERMOPLASTIC IMPRESSION COMPOUNDS
2. ACRYLIC RESIN – ‘SELF CURE’ OR ‘HEAT CURE’
3. PRESSURE OR VACUUM FORMED THEMOPLASTIC
COMPOUNDS
4. LIGHT CURED ACRYLIC
WE WILL BE CONSTRUCTING OUR SPECIAL TRAYS WITH
LIGHT CURED ACRYLIC. THIS IS BECAUSE IT IS
RELATIVELY CHEAP, SAFE (NO MIXING REQUIRED) AND
EASY TO ADAPT TO A MODEL. IT ALSO HAS A
RELATIVELY LONG WORKING TIME.
Custom Trays 302B – Week 5
Page 4 of 8
Stage 1
ADVANTAGES OF CUSTOM TRAYS
1. Even thickness of impression material.
2. Controlled distortion of tissues.
 Muco-static: pertaining to the normal, relaxed
condition of mucosal tissues covering alveolar
ridges and denture related surfaces.
 Muco-compressive: pertaining to pressure on
mucosal tissues covering alveolar ridges and
denture related surfaces.
3. Even support of the impression material.
4. Control over the flow of the impression material.
5. Reduced discomfort for the patient.
6. Economic use of the impression material.
7. Reduced distortion during pouring of model due
to support of impression material.
Custom Trays 302B – Week 5
Page 5 of 8
Stage 1
PRIMARY IMPRESSION
Is an impression which is taken with a stock tray, it is not an
accurate representation of the patient. Once the impression
is poured a primary model is produced.
PRIMARY MODEL
Is an inaccurate copy of a patient’s mouth which is used to
assess and decide on a treatment plan. A primary models
purpose is also to construct a custom tray on it.
SECONDARY IMPRESSION
Is an impression which is taken with a custom tray, it is an
accurate representation of the patient. Once the impression
is poured a secondary model is produced.
SECONDARY OR MASTER MODEL
This model is an accurate copy of the patient’s mouth, it is
this model which is used to begin the steps in constructing an
appliance or denture.
Custom Trays 302B – Week 5
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Stage 1
Custom Trays 302B – Week 5
Page 7 of 8
Stage 1
HANDLE DIMENSIONS AND POSITION
20 – 25mm
20mm
10 mm
4mm
4mm
The handle must be placed so that it will not interfere
with any movements of the patients’ lips during the
impression taking, it should be placed where the teeth
once were. The handle should be shaped so that it is:
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It is easy to hold
Strong enough so not to fracture during removal
Smooth and round with no sharp edges
Positioned approximately in the centre or midline
region
OUTCOME:
You should now be able to know the following:
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What is an Impression Tray
What are Stock Impression Trays
The Advantages of Stock Impression Trays
The Disadvantages of Stock Impression Trays
What are Custom Impression Trays
The Advantages of Custom Impression Trays
The types of Impressions and Models
Flow Chart of Impression Trays
Handle Dimensions and Position
Custom Trays 302B – Week 5
Page 8 of 8
Stage 1