DIES AND WAX

PATTERNS

INTRODUCTION

The wax pattern is a precursor of the finished cast

restoration that will be placed on the prepared tooth.

Careful handling and manipulation of the wax pattern is

required to obtain an accurate casting

DIEIt is the positive reproduction of the form of a prepared tooth in

any suitable substance

DEFINITIVE CAST

A replica of the tooth surfaces, residual ridge areas, and/or other

parts of the dental arch and/or facial structures used to fabricate

a dental restoration or prosthesis

REQUIREMENTS OF A DIE

• Reproduce the preparation exactly

• All surfaces should be adequately duplicated

• Avoid voids in the margins

• Adequate access to margin is imperative

• Adequately rigid

DIE MATERIALS

• Type IV (high strength) dental stone.

• Type V (high strength and expansion) dental stone

• Resin strengthened gypsum products

• Resin dies – epoxy, polyurethane

• Electroplated dies

• Flexible die materials

SELECTION CRITERIA

• Dimensionally accurate cast – strong and resistant to

abrasion

• Easy to section and trim

• Compatible with separating agent

• Accurate surface detail reproduction

• Contrasting colour

• Easily wettable by wax

• Type of restoration needs to be considered

DIE MATERIALS

DIE SYSTEMS

1. REMOVABLE DIES

2. SOLID CAST WITH INDIVIDUAL DIE

3. ALTERNATIVE DIE SYSTEMS

REMOVABLE DIESAdvantages

• Simple to fabricate a cast and die

• Maintains fixed and immovable relationship between the

abutments

• Easier to obtain physiologically harmonious restoration contours

when fabricating wax pattern.

Disadvantages

• Wax pattern should be transferred from one to the other.

• Can be used only with elastomeric impressions

REQUIREMENTS OF REMOVABLE DIE SYSTEM

• Dies must return to their exact original positions.

• Dies must remain stable, even inverted.

• Cast containing the dies must be easy to mount on an

articulator.

METHODS OF REPOSITIONING DIE

PREPOUR TECHNIQUE

• Devices are oriented into the impression before pouring the

stone

POST POUR TECHNIQUE

• Devices are oriented into the impression after pouring the stone.

DOWEL PIN

A metal pin used in stone casts to remove die

sections and replace them accurately in the

original position

TYPES OF DOWEL PINS

Tapered, flat-sided brass dowel pin

Flat-sided, stainless steel dowel pin

Curved, single dowel pin

Single dowel

Double dowel

Two separate dowels

Horizontal contact tracks and vertical ribs

STRAIGHT DOWEL PIN

• Commonly used for many years.• Brass dowel pin is used

Advantages• Resists horizontal displacement • Removable die facilitates wax up and ceramic build up• No special equipments required

Disadvantages• Technical skill is needed

CURVED DOWEL PIN

• Incorporated into the impression before or after the

stone is poured.

SOLID CAST WITH INDIVIDUAL DIE

(MULTIPLE POUR TECHNIQUE)

Impression obtained

Ist pour – prepared teeth area; set; separated ;trimmed into die

2nd pour – entire arch – mounted on articulator (Definitive cast)

Wax pattern started on die ,transferred to articulated casts – refinement of axial contours

After completion pattern is returned to die before investing

ADVANTAGES

• Simple

• Minimal trimming of definitive cast

• Gingival tissue – guide when contouring restoration

DISADVANTAGES

• Difficult to transfer complex wax patterns

• Seating pattern on definitive cast – 2nd pour larger

• Only be used with elastomeric materials

CHOICE OF CAST AND DIE SYSTEM

• Operator preference

• Solid cast technique simplifies cast and die fabrication –

waxing and porcelain becomes difficult

• Dowel and removable die system less manipulation of wax

pattern; reduces chances of breakage during transfer;

porcelain handling easier

Impression removed from

mouth

Washed under running water

Blow dried, inspected

Disinfected

PRE POUR TECHNIQUE

Position dowels pre pour with bobby pins and sticky wax

Measure proper proportions of stone and water

Hand spatulation; vacuum mix

Small quantities – prepared area in increments

Rest of impression filled to a height of atleast 5 mm beyond free gingival margin

POST POUR TECHNIQUE

SOLID CAST MULTIPLE POUR

Stone mass is built upto height

of 25 mm

First pour has set; cast is separated

and repoured

First pour sectioned into individual dies

SECTIONING REMOVABLE DIES

• Trim buccal and lingual sulcal areas adjacent

to removable areas

• Mark intended saw cuts in pencil

• Saw cuts – parallel or converge

• Avoid undercuts

• Carefully position saw blade

• Not touch prepared tooth margin or proximal

contact

• 0.007 to 0.01”

DIE PREPARATION

DITCHING THE DIE

• Ditching or trimming the die defines

the position of the margin and acts as a

guide to gingival contour when the

restoration is being waxed.

• Excessive trimming does not give the

correct emergence profile and may

lead to an over-contoured or bulky

crown.

DITCH BELOW MARGIN LINE THE MARGIN

APPLY DIE HARDENER ABOVE AND BELOW MARGIN LINE

FIRST RELIEF COAT ADDITIONAL RELIEF COATS

BLOCK OUT WAX

Thickness of die hardener are:

• Cyanoacrylates: 1.0 to 2.5um

• Acrylic lacquers: 4.0 to 10um

DIE SPACER

• Applied to die to increase cement space between axial

walls of prepared tooth and restoration

• Formulated to maintain constant thickness

• Should not coat entire preparation

• 1 mm space from the margin must be maintained

• Available as a paint on or pen type application

• Die spacer is needed to provide space for the luting agent

(cement) during cementation of the finished crown.

• When applying the die spacer over the preparation leave the

area 1mm above the margin line free of spacer.

• Close adaptation of the crown and cement (or luting agent)

• No disintegration and dissolution of the luting agent at the

margin.

LUTING AGENT SPACE

• The ideal space for the cement is suggested at 20 - 40μm

for each wall. So the internal diameter of the crown may be

40 - 80 μm larger than the prepared tooth.

• There needs to be space otherwise the restoration will not

seat properly. Each dentist and laboratory have their own

standard thickness within this specified range.

INCREASING LUTING SPACE

INCREASEDTHERMAL

ANDPOLYMERISATION

SHRINKAGE

SOLID CAST WITH

INDIVIDUAL DIES

INTERNAL LAYER OF SOFT WAX IN WAX

PATTERN

DIE SPACERS

INCREASEDEXPANSION OF INVESTMENT

MOLD

METAL

REMOVAL

FROM FITTING

SURFACE

MARKING MARGINS

• Precise marking of preparation margin is crucial

• Color used for marking should contrast wax

• Ordinary lead pencil not recommended

• Marked margin can be coated with cyanoacrylate;

blown dry

• Side of colored pencil used to keep line width minimal

ALTERNATIVE DIE SYSTEMS

DVA MODELSYSTEM

PINDEX SYSTEM

DI-LOK SYSTEM

ACCUTRAC (VENEERS)

DIVESTMENT TECHNIQUE

ZEISER SYSTEM

PINDEX SYSTEM

• Post-pour technique is used

• Reverse drill press is used to create a

master cast

• The machine accurately drills parallel

holes from the under side of the

trimmed cast

• Dual pin, tri plus pin

DI LOK TECHNIQUE

A snap-apart plastic segmented trays with internal orienting grooves

and notches is used

Impression is poured; di-lok tray filled

Cast trimmed to horse shoe configuration

Tray filled with second mix and cast seated

Die stone set- locking and curved arms of the tray are removed

Saw cuts made 3/4ths through stone; resulting die is trimmed

Cast and die reassembled in tray; mounted on articulator

ACCUTRAC

• Used in laminate veneers

• Removable die system

• Modification of a plastic tray

with internal orientation

grooves and notches

DIVESTMENT TECHNIQUE• Investment material itself is used for making a die.

• Die is directly incorporated into the investment with the pattern.

• This technique is mainly used for patterns that are not removable from the

die

Disadvantages

• Master cast may not articulate with the opposing cast properly (because of

high setting expansion).

• Seating the cast for interocclusal records can be a problem.

• Needs another cast and die for finishing and polishing purposes because

the die is destroyed while casting.

DIESTONE+INVESTMENTDIVESTMENT

A commercial gypsum bonded material that contains die material and the investment medium in comparable composition

• Commercially available as Divestment

• It is mixed with a colloidal silicate liquid. • Die is made from this and then wax pattern constructed

on it, then assembly is invested in a mixture of divestment and water, this eliminates possibility of distortion of pattern.

• Setting expansion: 0.9%

Box in the impression on the tray carrier for pin paralleling

Place tray carrier with impression onto the slider with solid ZEISER base plate underneath

Survey the required pin position and drill the pin holes

Push table down gently to definite stop position. Drill two holes per segment

ZEISER

SYSTEM

Insert tapered pins into drilled holes and press down according to friction required

Pour up the impression with die stone

Load base plate with stone around pins. Invert plate; seat onto impression.

After approx. 20 minutes (stone) or 8 hrs (BLUESTAR) remove the impression from the tray carrier and separate the pour up from the base plate.

Trim the arch, clean, blow dry and reposition back onto base plate.

Precision die saw

DIE SYSTEMS

WAX PATTERNS

WAX PATTERN

A wax form that is the positive likeness of an

object to be fabricated

METHODS OF FABRICATING A WAX PATTERN

• Pattern is waxed on the prepared

tooth in the patient’s mouthDIRECT

TECHNIQUE

• Pattern is waxed on a stone cast made from an accurate impression of the prepared tooth

• Most popular method

INDIRECTTECHNIQUE

ADVANTAGES OF INDIRECT TECHNIQUE

• Less chair-side time

• Better visualization of the restoration

• Ready access to waxing margins

INLAY WAX

• Inlay casting wax is used for all wax patterns.

• Inlay wax consists of:Paraffin (40% to 60%).

Dammar resin to reduce flaking

Carnauba resin, ceresin, candelilla wax to raise the melting

temperature.

Dyes to provide color contrasts

TYPE I WAX

• Formulated for making intraoral wax patterns• Medium hardness wax• Resist flow at mouth temperature

TYPE IIWAX

• Formulated for fabrication of wax patterns extra-orally

• Softer wax; Have a slightly lower melting point• Resist flow at room temperature

REQUIREMENTS OF GOOD INLAY WAX

1. Flow readily when heated, without chipping ,

flaking or loosing its smoothness

2. When cooled, it must be rigid

3. It must be capable of being carved precisely

without chipping, distorting or smearing.

4. Wax should be of some colour that will contrast

with and easily

distinguishable from the stone die

• Stresses – heating and manipulation

• Wax –thermoplastic material relaxes as these stresses

are released – distortion

• Distortion – poor fit

• To minimize distortion patterns should never be left off

the die, and they should be invested as soon after

fabrication

WAX PATTERN

FABRICATION

ARMAMENTARIUM

• PKT Waxing instruments( No.1,2,3,4,5)

• Wax spatula

• No.2 pencil

• Laboratory knife

• Bunsen burner

• Inlay casting wax

• Die lubricant

• Electric heating instruments(precise temperature control)

PKT

INSTRUMENTS

#1,2: Wax addition instruments#3 : Burnisher for refining occlusal anatomy#4,5: Wax carvers

• Heat the instrument in Bunsen flame

• Touch it in wax and quickly reheat its

shank in flame

• Wax spatula used

for adding large amounts

of wax

INTERNALSURFACE

WAX PATTERN REMOVAL AND EVALUATION

PROXIMAL SURFACES

AXIAL SURFACES

OCCLUSAL SURFACES

MARGIN FINISHING

POSTERIOR

TEETH

WAXING

INTERNAL SURFACE

• Die lubricant

• Flow wax onto die from well heated large waxing instrument

• Initial layer – wax is fully molten; wax memory – distortion

• Sufficient wax – coping without breakage

• Proximal areas extra bulk – grip and prevent distortion

• Trim wax

WAX PATTERN REMOVAL

PROXIMAL SURFACES

• Flat or slightly concave from contact

area to CEJ

• Overcontouring – periodontal

problems

• Undercontouring – flossing

ineffective

CONTACT AREAS

• Posterior contact areas – occlusal third

• Maxillary 1st and 2nd molar – middle third

• Contact between mandibular teeth and

maxillary molars – central

• Lingual embrasures larger than buccal

• Gingival embrasures - symmetric

AXIAL SURFACES

• Location of height of contour is particularly important

• Gingival third; mandibular molars in middle third

• Emergence profile: tooth surface gingival to its height of contour

immediately adjacent to gingival soft tissues

• Flat or concave

• Periodontal disease- axial contour modified to improve access

for plaque removal

• Wax gingival surface axially – smooth flat

profile

• Shape middle third of axial surface –

adjacent teeth as guide

• Add wax to join axial and proximal

surfaces and smooth them; location and

shape of mesial and distal transitional line

angles

• Boley gauge

OCCLUSAL SURFACES

• Nonfunctional cusps – overlap vertically and horizontally

• Point contact between opposing teeth

• Sequential wax addition technique

CONE PLACEMENTCUSPAL RIDGES SUPERIMPOSED

CONES, CUSPAL&TRIANGULARRIDGES SECONDARY AND MARGINAL RIDGES

COMPLETED OCCLUSAL WAXING

CUSP HEIGHT AND LOCATION

• Position and height of cusps – wax cones

• Mark central fossae of opposing teeth

• Position functional cusps occlude

buccolingual center

• Mesiodistal location of cones;occlusal

scheme

• Cusp height –curve of spee

CUSP-MARGINAL RIDGE ARRANGEMENT

• Functional cusp contacts opposing

occlusal surfaces on the marginal ridges

or fossa of the opposing teeth.

• One-tooth to two-teeth arrangement.

• Commonly used occlusal relationship.

CUSP-FOSSA ARRANGEMENT

• Functional cusp nestled into occlusal

fossa of opposing teeth

• Tooth-tooth arrangement

• Rarely used

• Centric cusp contact occlusal

fossa of opposing tooth at three points

• Developed by waxing two opposing

quadrants simultaneously

Indications

• Prevent Food impaction

• Centric relation closure forces near long axes of teeth

improved

• Improved stability results from tripod contact for each

functional cusp

Cusp fossa Cusp marginal ridge

1. Location of occlusal contact on opposing teeth

Occlusal fossae only Marginal ridges and occlusal fossae

2. Relation with opposing tooth

Tooth-to-tooth Tooth-to-two-teeth

3. Advantages Occlusal forces are directed parallel with long axis of the tooth. These forces are near the center of the tooth, placing very little stress on the tooth

Found in 95% of all adults. Can be used for single tooth restorations

4. Disadvantages Rarely found in natural teeth. Used when restoring several contacting teeth and teeth opposing them

Food impaction, displacement of teeth if functional cusps wedge into lingual embrasure

5. Application. Full mouth reconstruction Most restorations in daily practice

• Completion of axial contours -Give each cusp a triangular ridge towards center of occlusal surface(apex-cusp tip) -Secondary ridges : 2 to each triangular ridge;convex with grooves

MARGINAL FINISHING

Reflow margins; well adapted 1 mm wide zone from margin to prepared surface

POLISHING OF WAX PATTERN

ANTERIOR TEETH• Anatomic contour waxing – metal ceramic restorations• Lingual and incisal surfaces - overall arch form and occlusal requirements -concavity in lingual surfaces - Maximum intercuspation – anterior teeth should be set just out of contact - Lingual surfaces – non contacting

• Labial surface - Mesiolabial and distolabial line angles

WAX CUT BACK

• If ceramic veneer is to be prepared, once final

contour of wax pattern is completed, pattern

is cutback over an even thickness

• Usually about 1 mm

• Provide room for the porcelain fused onto

the cast metal substructure

WAXING CONNECTORS• Connectors that join separate components

created in wax just before margins finalized

• Whether cast or soldered; shaped in wax for

precise control

• Optimal strength: connector large

• Should not impinge and 1mm above crest of

interproximal soft tissue

• Esthetic areas: connectors should be hidden

behind ceramic veneer; lingual placement

REFERENCES

• Fundamentals of Fixed Prosthodontics

3rd edition Shillingburg

• Contemporary fixed prosthodontics

4th edition Rosentiel Land Fujimoto

• Tylman’s theory and practice of fixed

prosthodontics

• Phillips’ Science of Dental Materials

• Glossary of prosthodontic terms

• Butta .R, Tredwin C j, et.al, Type IV gysum compatibility

with five adition-reaction silicone impression materials

J Prosthet Dent 2005;93:540-4.

• Reports of Councils and Bureaus (1977) revised

American Dental Association specification No. 19 for

non-aqueous, elastomeric dental impression materials