PRELIMINARY AND SPECIAL TRAY

SPECIAL TRAY (INDIVIDUAL TRAY)

custom-made device prepared for a particular patient which is used to carry, confine and control an

impression material while making an impression

MOST COMMONLY USED MATERIALS IN SPECIAL TRAY (INDIVIDUAL TRAY)

Most commonly used materials

o Shellac

o Cold cure acrylic/Self cure acrylic

o Visible Light Cure

o Vacuum formed thermoplastic resin

o Type II impression compound (Tray Compound)

TRAY RESIN

Brittle but very accurate

TRAY RESIN

Easy to adjust with a knife or a handpiece with a bur while border molding

LIGHT CURE RESIN

Accurate but expensive

LIGHT CURE RESIN

Must be adjusted with an acrylic bur.

LIGHT CURE RESIN

Cannot be adjusted with a knife while border molding

red line

depth of the vestibule

red line

arks the denture base

2mm

blue line __ above the redline.

blue line

determines the tray extension

Frenum

o Buccal surface of the tuberosity

o Rugae

o Flabby portions of the alveolar ridges

Block out undercut max areas.

Mylohyoid ridge

o Frenum

o Lingual side of the mandible opposite the retromylohyoid space

Block out undercut mand areas.

Spacer

should be adapted throughout the extent of special tray (coincide with the second line)

Spacer

should be cut out in 2-4 pieces

STOPPER

the part of the tray that extends into the cut out of the spacer

o Very strong

o Adapts well to the cast

o Good thermal properties

o Can be trimmed to adequate thickness

o Easy to fabricate

o Good stability

ADVANTAGES OF LIGHT CURE RESIN

Ease of use

▪ Minimal wastage of material

ADVANTAGES OF SPRINKLE ON TECHNIQUE

Even thickness cannot be obtained

▪ Too many porosities may form within the material

▪ Time consuming

DISADVANTAGES OF SPRINKLE ON TECHNIQUE

2-3mm

Tray periphery thickness

1-2mm

Rest of the tray thickness

10mm high

Tray handle

Finger rest

aid in holding the tray in position when making the wash impression.

Finger rest

without this, the wash material will be forced back into the vestibule distorting this portion of

the impression

Acrylic special trays

stored in water (to avoid warpage)

Shellac special tray

cool dry place

PRELIMINARY IMPRESSIONS

for diagnosis and construction of custom impression trays

PRELIMINARY IMPRESSIONS

Must capture all intraoral landmarks, retromolar pads, retromylohyoid space, hamular notches, et

PRELIMINARY IMPRESSIONS

capture the 3-D contours of the vestibular

borders of the limiting structures

Alginate (irreversible hydrocolloid)

o Tray Adhesive

o Edentulous metal stock trays

o Plastic mixing bowl

o Round edge spatula

o Periphery wax

o Water bath

o Mouth mirror

MATERIALS FOR PRELIMINARY IMPRESSION

STOCK TRAY

a receptacle into which a suitable material is placed to make an

impression

2'mm clearance

between the stock tray and the ridge

STOCK TRAY

Should extend over the tuberosity and the hamular notch

CAKES

a temperature-controlled water bath to the required softening temperature

STICKS

softened by heat over a flame

POSTERIOR PALATAL SEAL (POSTDAM

The soft tissue at or along the junction of the hard and soft palate on which pressure within the physiological limits of

the tissues can be applied by a denture to aid in the retention of the denture

o Aids in retention by making constant contact with the soft palate (speech, mastication, and swallowing)

o Reduced gag reflex

o Prevents food accumulation

o Compensates for no polymerization shrinkage

FUNCTION OF POST DAM

VIBRATING LINE

Imaginary line across the posterior part of the palate marking the division between the movable and immovable

tissues of the soft palate

ANTERIOR VIBRATING LINE

Ask the patient to say “ah” in short vigorous burst

POSTERIOR VIBRATING LINE

Ask the patient to say “ah” in short but normal non-vigorous fashion