Definitions
Tray
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 .
Impression
Is A Negative Replica Or Imprint Of The Teeth And Adjacent Tissues For Use In Dentistry
Impression Material Is A Substance Used For Making A Negative replica For The Required Tissues
Types Of Impression Trays
Stock Trays (Various Size & Made By Manufactures)
Custom (Individual Or Special) Trays Made For One Patient And Discarded Later
Requirements Of An Ideal Impression Tray
Rigid
Retain Shape
Easily To Be Trimmed And Modified
Smooth Edges
Control Material During Seating, Set &Removal
Classification Of Dental STOCK Trays
Metal trays are made of
Aluminum or stainless steel
Non metallic trays are made of
*Plastic (disposable)
**Plastic can be sterilized (xantalgin trays)
According to the nature of impression materials
*Plain tray
*Perforated tray
*Rim lock tray
*Water cooled tray
# PARTS OF STOCK TRAY
BODY & HANDLE
# Differences between trays for complete denture and those for RPDs
Preliminary (Primary) impression
Is an impression made for the purpose of diagnosis and construction of custom tray
Preliminary (Primary or diagnostic) cast
Positive replica of the upper or lower jaw tissues that is made in an impression and over which custom trays may be made
Preliminary Impression Materials *Alginate (irreversible hydrocolloid) and may be
used for• Primary impression for complete denture• Some cases of RPD• Some cases of FPD• Alginate impression should be poured
immediately• (WHY) ??????????** Modeling compound
Preliminary (Diagnostic) Cast
*A Positive Reproduction Of The Upper Or Lower Jaw Tissues That Is Made In An Impression And Over Which Impression Trays May Be Made
• ** Requirements and uses of diagnostic cast
Uses OF Diagnostic cast 1- Detection of ridge relationship and inter
ridge distance 2-To evaluate the size and contour of the
arch 3- To detect areas need to be relieved
4- To construct a custom tray
Custom)special &individual) Impression Trays And Construction Of Master Cast
Is an individual tray made over the diagnostic cast and it is used in making a final impression.
Materials for constructing a custom tray- Autopolymerizing acrylic resin (self- curing)- Heat cured acrylic resin- Vacuum adapted resin- Shellac base plate - VLC- Hydro plastic materials
Autopolymerizing Acrylic Resin
Easy To be used and require no special Equipment
Technique of construction ;
1) Finger dough adapted technique
2) Sprinkle on method
Shellac Baseplate
*Easily manipulate and quickly adapted
**Tend to warp, distort easily, brittle, lack rigidity.
(Dimensionally unstable)
VLC (visible light activated resin)
*Urethane dimethylacrylate
**Initiator
***Curing unit has light from quartz halogen lamp
VCL has no monomer, well adapted,,,
excess can be stored to be used later.
Materials Used For Final Impression
For example:- Zinc-euginol Impression Paste ( Close
Fitting Custom Tray,,, No Spacer
Elastomeric Impression Materials
Border Molding
Green Stick Compound Is Traced Along The Sections Of The Tray,,, Patient moves lips Checks And Tongue To Record The Proper Denture Extensions.
Pouring & Trimming And Indexing Of Master Cast
Boxing Is building up vertical walls around the
impression usually in wax, to produce the desired size, form of the base of the cast and to preserve the width, height and landmarks of the impression
Advantage of boxing 1) Preservation of the border of the impression 2) Controlling the thickness of the base 3) Conservation of time and materials 4) The produced cast free from air bubbles Methods; 1)Plaster And Pumice 2) Putty Methods. - Indices Permit Removal Of The Casts And Accurate
Replacement In The Articulator.
RECORD BLOCKSRecord blocks are fabricated to register
the relationships of the mandible to the maxilla at which the denture is made.
Record block consists of• Record base (temporary or permanent)• Record rim (occlusal rim)
#Record base*Temporary (same materials and techniques
used for special tray fabrication**Permanent may be made of heart cured
acrylic resin or metal
#Occlusal rim*Base plate wax**Modeling compound***Plaster & pumice
Requirements For Baseplate Well Adapted To The Basal Seat Area
AS The Finished Denture. Have The Same Borders As The
Finished Denture. Rigid & Dimensionally Stable Easily Manipulated Smooth & Rounded Edges Does Not Damage The Cast During
Removal or replacement
Uses of occlusion rim 1) To establish accurate maxillo-mandibular
relation record
2) To determining the length and width of the artificial teeth
3) In arranging the artificial teeth to form the trail denture.