special tray

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.