wax patterns in fpd/ dentistry course in india

WAX PATTERNS IN FPD

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Contents • Introduction• History• Waxes• Armamentarium• Wax pattern fabrication

Coping fabrication Wax pattern removal and evaluation Proximal surfaces Axial surfaces Occlusal morphology Margin finishing

• Conclusion• References www.indiandentalacademy.com

INTRODUCTION

HISTORY


WAXESDental waxes are organic polymers consisting

of hydrocarbons and their derivatives.

Molecular weight ranges from 400-4000


Classification

According to origin According to use and application


ACCORDING TO ORIGIN

Natural Synthetic - Mineral - Plant- Insect- Animal


ACCORDING TO USE AND & APPLICATION

Pattern waxes Processing Impression waxes waxes


INLAY CASTING WAX

Composition1. Paraffin-chief content2. Gum dammar 3. Carnauba wax,Ceresin or Candelilla wax4. Beeswax5.Colouring agent


CLASSIFICATION

According to ANSI and ADA sp no 4 Type 1 a medium wax. Used for direct technique.

Type 2 a softer wax.Used for indirect technique.


Properties1. Flow: flow % requirements for ADA sp no 4Type of inlay wax

30 Max

37 Max

40Min Max

45Min Max

Type 1 --- 1.0 --- 20 70 90

Type 2 1.0 --- 50 --- 70 90


2. Thermal properties- Thermal conductivity- Coefficient of thermal expansion may expand 0.7% with an increase in in temperature of 200 C and contract as much as 0.35% when it is cooled from 370 C to 250 C- Average co-efficient of thermal expansion: 350 x 10-6 0/C


3.Wax distortion - Elastic memory This can result from thermal changes,release of stresses on cooling,time and temperature during storage etc. Other desirable properties of inlay waxes include: - Color - Residue ADA sp no 4 requires that the melted wax when vaporized at 5000C shall leave behind no solid residue in excess of 0.10% of the original weight of the specimen.


Armamentarium• PKT waxing instruments (no 1 to no 5)• No 7 wax spatula• Laboratory knife with blade• Sharp colored pencil (contrasting to wax)• Sable brush• Bunsen burner • Inlay wax• Occlusal indicator powder• Die lubricant www.indiandentalacademy.com

WAX PATTERN FABRICATION

The following sequence is recommended:1. Coping fabrication.2. Wax pattern removal and evaluation.3. Proximal surfaces.4. Axial surfaces.5. Occlusal surfaces.6. Margin finishing.


COPING FABRICATION


WAX PATTERN REMOVAL & EVALUATION


PROXIMAL SURFACES


AXIAL SURFACES

Emergence Profile


OCCLUSAL MORPHOLOGY

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 and displacement of teeth may arise if functional cusps wedge into a lingual embrassure.

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

Classification of occlusal arrangements


WAXING TECHNIQUE

There are two wax added techniques for waxing occlusal surface of restoration.1st technique given by E.V. PayneH.L. Lundeen promoted the same technique using wax of a different color for each of the features.Usually associated with cusp-marginal ridge occlusal scheme2nd technique given by P.K. Thomas Most often associated with cusp-fossae occlusal scheme


CUSP MARGINAL RIDGE FOR MAXILLARY TEETH


CUSP MARGINAL RIDGE FOR MANDIBULAR TEETH


CUSP-FOSSA ARRANGEMENT


MARGIN FINISHING


WAXING FOR ANTERIOR TEETH


Wax pattern for the functionally generated path technique


SUMMARY & CONCLUSION


REFERENCES

• Contemporary Fixed Prosthodontics. 3rd edition, Rosensteil.

• Fundamentals of Fixed Prosthodontics. 3rd edition, Herbert T. Shillenburg.

• Philips Science of Dental Materials. 10th edition, Kenneth J. Anusavice.

• Restorative Dental Materials. 6th edition, Robert J. Craig.

• Theory and Practice of Ceramo-metal restorations. Mashiro Kuwata.


• Periodontal considerations of crown contour. Perel ML. JPD, 1971; 26: 627-

630.

• Current controversies in axial contour design. Anthony HL, Tjan. JPD,

1980; 44: 536-540.

• Crown contours and gingival response. Lee M. Jameson, Willam Melone,

JPD 1982; 47: 620-624.

• Emergence profile in natural tooth contour. Part 1, Burney M. Croll, JPD

1989; 62: 4-10.

• Emergence profile in natural tooth contour. Part 2, Burney M. Croll, JPD

1990; 63: 374-379.


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