WAX PATTERNS

Presented by:Dr Shebin Abraham

Dept Of Prosthodontics

CONTENTS Introduction Prerequisites Material sciences Technique

Armamentarium Waxing instruments Posterior teeth Anterior teeth Waxing for metal ceramic crowns.

Conclusion

INTRODUCTION

“Lost wax technique” metal prosthesis.

Success in clinical practise depends upon on every step in the treatment procedure.

A large of percentage of time and effort spent in fabricating fixed prosthesis is devoted to producing a very accurate pattern.

• Most defects can be easily be corrected in wax pattern but cannot be done in a metal casting.

• Follow:- 1. Precise technique, 2. Use the correct armamentarium 3. Handle the material(wax) carefully in

order to obtain

Prerequisites for wax patterns

1. Correction of defects. Small defects on the die like dimples due

to caries or loss of previous restorations Normally blocked out intraoral by GIC Can be blocked on the die as long as the

defect does not extend to within 1 mm of the cavity margin.

Blocked out using zinc phosphate cement Autopolymerizing resin, monomer spray

etc

2. Provision of adequate cement space. Adequate cement space is of 20 to 40 um for

each wall. So internal diameter of the wall of crown would

be 40 to 80 um. 1mm of band around the margin shouldn’t be

given any luting space. If no luting space is provided the crown

wouldn’t seat completely due to the hydraulic pressure from the viscous cement.

Factors that causes increase in the cement space:-

1. Use of a solid cast with individual stone dies

2. Use of an internal (initial) layer of soft wax

3. Use of die spacers4. Increased expansion of the

investment mold5. Removal of metal from the

fitting surface by grinding, airborne-particle abrasion, etching with aqua regia, or electrochemical milling

Factors that causes decrease in the cement space:-

1. Use of resin or electroplated dies

2. Use of alloys with a higher melting range

3. Reduced expansion of the investment

Die spacer is most commonly used to create space for the luting cement.

This material (similar to model airplane paint) is applied to the die to increase the cement space between axial walls of the prepared tooth and the restoration. It is formulated to maintain constant thickness when painted on the die.

Different types of die spacers are:- Red, 7 microns:

Yellow, 7 microns

Blue, 10 microns

New dentin, 10 microns

Gold 13 microns

Silver, 13 microns

3. Marking the margins The margins should be marked in order to locate it

during wax carving. It should be dileneated with a contrast coloured

pencil like red for green wax. Graphite pencil shouldn’t be used as it can abrade

the die and also act as antiflux. If required the marked area can be coated with a

thin layer of cyanoacrylate.

Material science

GC inlay waxes

Bego inlay waxes

Kemdent inlay waxes

Cornings inlay waxes

Kerr inlay waxes

Charminar inlay waxes

Material science

Paraffin-60% (Melting range 40-71o C)

Carnauba-25%(Melting range 84-91o C)

Beeswax-5%

Ceresin-10%

Natural resins (gum dammer)-less than 1%

Organic fillers- added to avoid excessive shrinkage, expansion due to temp change

Microcrystalline wax- In minute amount.

Candelilla

Coloring agents

Composition of inlay wax

According to ADA no 4 it is of two types:- Type I-a medium wax (generally used with

the direct technique for making patterns in the oral cavity)

Type II-a softer wax (generally used for the indirect fabrication of castings)

Waxes used with direct techniques must not flow appreciably at mouth temperature.

Those used with indirect techniques must resist flow at room temperature to maintain their newly shaped forms.

Source:- Philips textbook of dental materials

Points to be followed while using waxes:- Its has ELASTIC MEMORY should be thoroughly

liquefied before it is added to die, dipping method is best.

STRESS RELEASE as wax sets stresses are released.

HIGH THERMAL EXPANSION AND CONTRACTION so it should be heated only adequately.

So because of above properties the wax patterns should be remelted at the margins before it is invested for proper adaptation.

Different types of waxes used:-

Special wax for electrical wax heating unit (vario therm),

Dark blue-hard and light blue soft are for modelling, trimming and dipping application,

Lilac-medium hard , red stress free for cervical margins,

Green wax-hard for trimming. Dip application yellow wax caps of

uniform strength Wax Preforms are available - It

simplifies wax up and shorten finishing procedure

Different techniques in wax pattern fabrication:

1. Dipping method.

2. Addition method.

3. Molten press method.

4. Injection method.

Source:- Google Web

Armamentarium required for wax pattern fabrication

1. PKT waxing instruments

2. No 7 wax spatula

3. Laboratory knife with no 25 blade

4. Sharp colored pencil (contrasting to wax)

5. Sable brush

6. Bunsen burner/electric wax knife

7. Inlay wax

8. Occlusal indicator powder(zinc-sterate or powdered wax)

9. Die spacer

10. Die lubricant (separating liquid)

11. Soft tooth brush

12. Fine nylon hose

Waxing instruments:-

Waxing instruments can be categorized by the intent of their design:

1. Wax addition,

2. Carving, or

3. Burnishing.

Of the popular PKTs (designed by Dr. Peter K. Thomas specifically for the additive waxing technique), No. 1 and no. 2 are wax addition instruments,

No. 3 is a burnisher for refining occlusal anatomy,

Nos. 4 and 5 are wax carvers.

No1 & 2

No 3 No 4

No 5

No 7

Wax carvers. No. 2 Ward and nos./, and 3Hollenback.

DPT no. 6 wax burnisher.

Electric waxing instrument

Sequence in wax pattern fabrication1. Coping fabrication.

2. Wax pattern removal and evaluation.

3. Proximal surfaces.

4. Axial surfaces.

5. Occlusal surfaces.

6. Margin finishing.

1. Coping fabrication

a) Before coping is fabricated die lubricant is applied.

b) The wax is added PKT no1 or no 2.

c) Initial layer should be completely molten Memory effect!!!!!

d) Whenever subsequent layers of wax are added the previous layer which was applied should be remelted or else creases or folds would form on fitting surface.

e) A large waxing instrument can be used like PKT no 7 is adequate for this purpose.

f) Adequate bulk should be provided at proximal and axial surface in order to prevent distortion while removal.

g) Excess wax at the margins should be scrapped of carefully.

h) Thin layers scrapping----carefully-----damage to the die---use burnisher instead of sharp carvers.

i) Dipping the die in molten wax pot is easiest and better way to fabricate a coping.

2. Wax pattern removal and evaluation The wax pattern sufficiently cooled

Removed using the thumb and forefinger with light grip pressure.

A small rubber dam piece. If the pattern is not coming out the

excess wax at the margin should be trimmed of.

After it remove the patterns is evaluated

3. Proximal surfaces

The proximal surfaces of natural teeth tend to be flat or slightly concave from the contact area to the cementoenamel junction, and any restoration must reproduce this feature.

Over contouring maintaining periodontal health difficult

Excessively concave or under contoured proximal surfaces flossing ineffective.

Proximal area gingival to The contact area are Normally flat or concave

Contact areas:- Abnormally large proximal contact make

plaque control more difficult can lead to periodontal disease

Very small (point) contacts may be unstable and cause drifting

Deficient contacts can also lead to food impaction On maxillary teeth more

Occlusal and buccal when Progressing anteriorly

On mandibular posterior teethCentrally located

Procedure:-

The wax coping is seated back on to the die Wax is added coping at the contact area

die is seated back with wax is in molten state.

After the wax is hardened the die is removed and the wax gingival to the contact area is shaped accordingly.

The proximal surface is evaluated and the surface should be either flat or slightly concave.

They should adequate space for the lingual and buccal embrasure.

The wax should continue to the unprepared tooth surface.

Axial surfaces:- The buccal and lingual surfaces are shaped

to follow the contours of adjacent teeth. The height contour should be adequately

placed usually at the gingival third of all the teeth except in mandibular molars it is present in the middle third.

The natural teeth are rarely more than 1mm wider at their height of contour than at CEJ

The tooth surface gingival to its height of contour immediately adjacent to the gingival soft tissues is called emergence profile, it is usually flat or concave.

Straight profile treatment objective Creation of convexity or a shelf or ledge

bacterial plaque removal difficult to cause inflammation of marginal gingiva.

Special care should be taken when waxing teeth with recession or exposure of furcation, providing adequate space for hygiene procedures

Adjacent and contralateral teeth are used as guide A flat profile is created gingivally . No change of direction from unprepared tooth

structure to axial restoration contour Add wax to join axial and proximal surfaces and

smooth them, the line angles should correspond to those on contralateral teeth if present

Procedure:-

Evaluate at greatest convexity Compare with contralateral

tooth Each part of the outline is

scrutinized properly. Buccal and lingual contours and

the embrasures should all be assessed.

Each contact area has four embrasures: gingival, buccal, lingual and occlusal, except occlusal all will be complete by now

All the embrasure should be symmetrical.

Evaluation:-

The cusps and ridges of the occlusal surfaces should be shaped to allow even contact with the opposing teeth while stabilizing the teeth and directing forces along their long axes.

Non-functional cusps should provide adequate horizontal and vertical overlap.

Occlusal surfaces:-

Why put all those grooves on the occlusal surface????

Why not simple inclined planes on a flat table????

Numerous occlusal contacts Small centric contacts allow for disclusion in excursion

Occlusal morphology with inclined plane produceLarge contacts in centric occlusion A and inExcursions B

Importance of Occlusal Morphology

Point contacts between opposing teeth are preferred to broad, flat occlusal contacts because1. Wear of the restorations will be minimized and

2. Mastication of tough or fibrous foods improved.

Effect of anterior guidance The contact of anterior teeth in excursions affects the

movements of the mandible

Change in morphologic features of anterior restoration can change the anterior guidance

Increase in vertical overlap- longer cusp and vice versa

Increase in horizontal overlap - shorter cusp and vice versa

Types of Centric Contacts

There are three basic ways by which centric contacts are usually established:-

1. Surface to surface contact Not recommended because it is stressful and it

produces lateral interferences.

2. Tripod contact In tripod contact the tip of the cusp never touches

the opposing tooth. Instead, contact is made on the sides of the cusps which are convexly shaped. It is a stable contact. 3 point contact is seen.

3. Cusp tip to fossa contact In this the cusp tip is properly located in the most

advantageous fossa. It offers good function and stability. This type of occlusion is easy to equilibrate.

Occlusal schemes are basically classified on the basis of contact made by the functional cusp on the opposing tooth in the centric relation:-1. Cusp to fossa occlusal scheme.

2. Cusp to marginal ridge occlusal scheme.

Occlusal schemes

Cusp to fossa occlusal scheme Functional cusp contacts opposing fossa in the

centric relation. Tooth to tooth type of arrangement. Hence forces are directed parallel to the long axis

of the tooth and also near the centre of the tooth, thus minimizing lateral stresses.

Rarely seen in the natural dentition it can only be given in cases of full mouth reconstruction.

Cusp to marginal ridge occlusal scheme

Functional cusp contacts fossa and marginal ridge of opposing pair of teeth.

One tooth to two teeth type of an arrangement. It is the most commonly found scheme, almost in 95%

of adult patients. Hence commonly practiced for constructing single unit

restorations or small span fixed partial dentures. It has a disadvantages of causing food impaction.

Aims and Objectives of Selecting Correct OcclusalScheme and Giving Correct Occlusal MorphologyWhile Restoring Patients’ Teeth are

1. To direct the occlusal forces properly by minimizing lateral forces during excursive movements of the mandible.

2. To make the occlusion stable.

3. To increase the masticatory efficiency.

4. To reduce the frictional wear.

Waxing Technique to Develop Cusp to Marginal Ridge Relationship

Proposed by E V Payne.First proposed waxing technique.Called as the wax additive techniqueSteps in this technique are:-

Step:- 1

Step:- 2

Step:- 3

Completed wax pattern

Waxing technique to achieve Cusp to Fossa Occlusal Scheme

Developed by P K THOMAS.

Mostly used in full mouth rehabilitation cases. In this occlusal scheme, mandibular functional

cusps arise opposite the middle of maxillary teeth; similarly maxillary functional cusps are positioned half way between the mandibular buccal and lingual cusp tips.

Hence occlusal forces are transmitted parallel to long axes of teeth.

Steps:-1. Cones mandibular functional cusps first. 2. Located approximately one third the distance from the

buccal to lingual surface. Also they should fall into appropriate fossae mesiodistally.

3. Then the cones for maxillary palatal cusps are placed.4. Next non functional cusps are placed, i.e. Maxillary

buccal and mandibular lingual.

Certain morphological differences which need tobe carved while doing wax ups to achieve Cusp To Fossa Occlusion

In Mandibular Teeth. During working excursion, buccal cusp of each

maxillary premolar will pass distal to the buccal cusp of each mandibular premolar.

To facilitate easy and rapid disocclusion, it is necessary to place a small depression in the form of notch on the distal incline of buccal cusp of each mandibular premolar. This notch is referred as Thomas notch.

During non working excursive movement of the mandible, mesiopalatal cusp of maxillary molar passes through the area distal to the distobuccal cusp of mandibular molar.

A notch is developed to form three buccal cusps in both the mandibular molars to prevent this non working interference

Lingual cusps of mandibular molars and premolars should be short enough to allow easy and rapid disocclusion

In Maxillary Teeth:- During non working excursive movement of

the mandible, distobuccal cusp of mandibular molar moves in a mesiolingual direction across the buccal incline of mesiopalatal cusp of maxillary first molar.

To provide the escape way for opposing cusp, it is necessary to place a groove on the mesiopalatal cusp of maxillary 1st molar. It is

referred as Stuart’s groove

Margin finishing:-

To optimize adaptation it is done. Done before investing by

reflowing the margins. It minimizes dissolution of cement

and helps in plaque control in the final casting.

1mm of area at the margin is reflowed.

Note:- Over waxing:-

Shouldn’t be done.

Any little excess flash over the margins should be trimmed off.

Open margins:- A gap between the wax and the die, resulting

in an open margin, can be difficult to detect.

If the wax is not well adapted, a black shadow line will be visible.

Ripples:- Rough margins on wax patterns if not polished

can be carried to metal causing accumulation of plaque.

Thick margins:- Thick rounded margins, improper seating and

poor contour,

Causing periodontal problem.

Finishing

Occlusal surface is polished by dipping a cotton in die lubricant and slowly passing it over the occlusal surface without any pressure.

It is done same over the axial surface, then with dry cotton pellet the surface is smoothened off carefully.

Die lubricant should not be left on the pattern.

Any depressions are filled with wax.

Waxing of anterior teeth:- It is completely different from posterior teeth. In case of multiple replacement of anterior teeth

a guide is used for labial and lingual contours. The labial and lingual contours influences

articulation of anterior teeth. It is recreated by custom anterior guidance table

made by diagnostic mounting of diagnostic cast. Usually the contralateral teeth is taken as guide

while carving the teeth.

Determined by overall arch form , functional occlusal requirements

Opposing incisors should contact evenly during protrusion but not during lateral excursion

It is achieved by the concavity in the lingual surface of the maxillary incisors

In centric closure they should be just out of contact

Waxing of lingual and incisal surfaces:-

The mesiolabial and distolabial line angles determines the appearance of anterior teeth and its shape.

If the labial surface is too bulbous, plaque control may be difficult, and there may be lingual tilting of the tooth caused by the force exerted by the upper lip.

When waxing individual anterior teeth, careful study of the embrasure form of adjacent teeth can be particularly helpful.

Waxing of labial surface:-

WAXING CONNECTORS The connector should be as

large as possible for optimum strength

Should not impinge on gingival tissue and should be at least 1mm above the crest of interproximal soft tissue

Should permit optimum plaque control

Cervical aspect should be arch like

In esthetic area connector should be hidden behind the esthetic ceramic veneer, therefore slightly placed lingually

Prerequisites are:-1. Waxing to anatomic contours

Normal anatomic configuration wax up is done.

At the porcelain metal interface the ceramic material should be at least 0.5mm thick

Distinct margin so that the porcelain is not overextended.

There should be no abrupt contour change between the metal and the adjacent porcelain.

All this can be achieved by waxing to anatomic contour first then cutting it back.

WAX-UP FOR METAL-CERAMIC RESTORATION

2. Occlusal stops:- The centric stops

located on either porcelain or metal.

At least 1.5 mm away from the junction to prevent porcelain fracture.

Opposing restorations must be carefully planned so that contacting surfaces will be of the same material (i.e., metal opposing metal, porcelain opposing porcelain)

Techniques for waxing up copings for metal ceramic restorations.

1. Single coping wax pattern.

2. Plastic shell technique.

Full contoured wax pattern is completely fabricated.

Then sketch the outline of the wax pattern to be removed with a sharp scalpel.

The ceramic veneer should extend far enough interproximally, particularly in cervical half to avoid metal display.

Remove 1.5 mm from the incisal portion of an anterior pattern with the knife.

Depth cuts of 1mm are places and horizontal vertical grooves are given connecting the depth cuts.

Then the islands in between the grooves are removed with a scalpel blade.

1. Single coping wax pattern.(cut back)

The porcelain metal interface should be given a 90 degrees butt joint.

The margins are reflowed again. The troughing or depth grooves can be placed

using a specialized chisel. Any sharp margins should be finished off.

2. Plastic shell technique

Sprueing of wax pattern. Wax, plastic and metal is used as sprue. 2.5 mm(10 gauge) to 2 mm(12 gauge) diameter

sprue is used in fpd. Location:- sprue should be attached to bulkiest

portion of the pattern. Attached at an angle 135 degrees to the nearest

axial wall. The attachment should be smooth and blended to

prevent turbulence.

CONCLUSION

• If the waxing procedure is followed in a sequential

order, inexperienced but conscientious operators

should have no problem achieving excellent

results.

• With more experience, they can combine and

modify some of these steps; however, waxing up

teeth "from memory" is not advised. Even

the most experienced technician should

copy the shape of natural teeth rather than

redesign them.

References:-

Waxing Techniques to Develop Proper Occlusal

Morphology in Different Occlusal Schemes J Indian

Prosthodont Soc (Oct-Dec 2011) 11(4):205–209.

Contemporary Fixed Prosthodontics STEPHEN F.

ROSENSTIEL, 4th edition.

Shillingburg, Herbert T., et al., eds. "Fundamentals of

Fixed Prosthodontics, ed, 1997." Learning 10 (1997): 40.

Anusavice, Kenneth J., et al. Phillips' science of dental

materials. Elsevier Health Sciences, 2012.