Presented by : pragati sharma Guided by : Dr. Ashistaru Saha Dr. Tushar Tanwani Dr. Pranay Mahaseth Dr. Ankita Piplani
Jan 05, 2016
Presented by :
pragati sharma
Guided by :Dr. Ashistaru SahaDr. Tushar TanwaniDr. Pranay MahasethDr. Ankita Piplani
CONTENTS
• INTRODUCTION
• REQUIREMENTS
• MATERIALS USED
• TYPES
• STEPS IN FABRICATION
• CONCLUSION
• REFERENCES
Special Tray
A special tray is defined as, “A custom made
device prepared for a particular patient which is
used to carry, confine and control an impression
material while making an impression’’.
Requirements of special tray:
A special tray should be
1.Rigid
2.Retain shape
3.Simple fabrication
4.Easy to trim
Materials used to fabricate special tray:
1. Auto polymerizing acrylic resin.
2. Shellac
3. Vacuum or pressure-formed thermoplastic
resin sheets.
4. Tray compound
Overview
FABRICATION
A. Preparation of the primary cast : 1. Undercuts should be find out with the
help of surveyor and should be blocked out .
RELIEF - TYPES
B. Adapting the relief wax: Relief wax should be adapted over the
relief areas marked on the cast.
ROY MAC GREGOR
SPACER
C. Adapting the spacer:
NEILL- O.9 mm of casting wax all over except pps area
BOUCHER’S DESIGN 1 mm base plate wax all over except over pps area.
MORROW,RUDD,
RHOADSfull wax spacer 2mm short of
tray.3 tissue stops -
4x4mm equidistant from
each other.
SHARRY’S SPACER DESIGN
base plate wax covering the entire tray,4 tissue stops-2 mm in width . In molar and cuspid region . 1 vent hole in incisive papilla region.
Function: a. The spacer allows the tray to be properly
positioned in the mouth during border molding procedure.
b. To allow the impression to have an even thickness of impression material.
Thickness of the spacer for different impression
material:
Zn oxide eugenol paste 0.5 mmAlginate 3 mmElastomeric 0.5-1.5 mmPlaster 1.5 mm
Zn oxide eugenol paste 0.5 mmAlginate 2 mmPolysulphide, Silicones 1.3 mm, 3 mmPlaster 2.5 mm
or
Spacer continued
Ref: J. A. Hobkirk
Ref: Finn
D. The use of stops: The spacer should be cut out in 2-4 places so that
the special tray touches the ridge in these areas .
Location: Usually 4 stoppers are placed,
Size and shape : 2 by 4 mm rectangle
E. Application of separating medium
Autopolymerizing resin impression trays
1.Sprinkle on
2.Finger adapted dough method
F. Acrylization: Thickness 2-3 mm
G. Fabrication of handle: Criteria of handle :
1. The handle should be parallel to
the long axis of the teeth that are to be replaced.
2. The handle should not arise horizontally from the tray because it may interfere with lip movements. 3. It should be 3-4 mm thick , 8 mm long , and 8 mm high.
4. The vertical distance from
the sulcus to the handle is 2 cm
5. The handle upstand must be made
long enough for the handle to exit
through the oral commissure.
Handle criteria continued
6. For mandibular tray two posterior handle should be given as finger rests.
The next phase is preparing the tray for border molding procedure:
Shellac
For immediate dentures
Full arch finger adapted
vacuum method Custom posterior trays Two piece trays
References: 1. Zarb. Bolender.: Prosthodontic Treatment of
Edentulous patient,edi 12. p225-247 2. Sheldon Winkler.: Essentials of Complete
Denture Prosthodontics,edi 2
3. The selective pressure maxillary impression: A review of the techniques and presentation of an alternate custom tray design . Year 2007,vol.7.