Introduction to Gold Casting

1. March 11, 2009 STI Introduction to Gold Casting

2. Go for the Gold! • Characteristics • Parallelism • No undercut areas like in direct restorations • Lost wax technique • Higher strength than direct restorations • Control of contours and good proximal contacts • Ability to create acute margins: use less metal, take away less tooth structure • Gold casting alloy • Multiple appointments

3. Considerations • 1. Biocompatibility • Most biocompatible • Best long lasting • Low reactivity in oral environment • No emission of electrons: no corrosion • 2. High gold alloys best >75% (wt) gold/platinum • Lower% gold performs well

4. Considerations • 3. Proximal caries • Extensive involvement • Casting transmits energy throughout to hold tooth together to prevent spread of fractures • Control of contours and contacts • Difficult subgingival margins are more properly restored • 4. Facial/lingual • Caries high? Caries rate? • Existing restorations: consider full coverage crown

5. Considerations • 5. Endodontic treatment • Consideran onlay • Design considerations • 6. Fractured teeth • Presence of fracture lines • Cusp replacement • 7. Elimination of electrical or corrosive activity

6. Considerations • 8. Diastema closure and occlusal plane correction • Need to extend mesial/distal dimension • Correction of occlusal irregularities • 9. Removable prosthodontic abutment • Control of rest seats and guide planes • Partial denture forces

7. Considerations • 10. Economics • More chair time needed • Laboratory fees • 11. Age of patient • Pulp size and anatomy • Example: In young patient, full gold crown requires removal of a large amount of tooth structure. Wait until the patient is older and pulp has receded a little bit. • Caries rate • Health vs. prognosis • 12. Esthetics • Metal may be seen • Consider alternatives: e.g. porcelain

8. The Inlay • Defined • Posterior teeth • Intracoronal = between the cusps, NOT over cusps • Within the cusps (intracoronal) • Class I or Class II (includes marginal ridge) • May involve a cusp • Indications • Patient desire • Form and function • Removable partial denture rest seat

9. The Inlay Preparation • Convenience form • Plane cut tapered fissure burs (No. 271, No. 169L) • Obtain uniformly tapered walls • Smooth walls, floor, and seat

10. “Draw” • Concept of Draw • All walls must diverge from gingival to occlusal • No undercuts • Path of the “draw” is usually along the long axis • 10-20 degree divergence—near parallel • 10 degrees if walls are necessary short • 20 degrees if walls are long and deep • SO: as length of wall increases, the degree of taper should increase

11. Path of Draw • The wax pattern (casting) must “draw” from the tooth. There can be NO undercuts or obstruction.

12. The Inlay: Outline form • Depth is 1.8 - 2.0 mm measured from pit closest to the involved marginal ridge • Maintain the bur parallel to the long axis of the tooth at all times.  • Exception:  Lower molars and premolars with crowns tiltedlingually.  Tilt bur 10 degrees to lingual.  • Maintain dentin support of uninvolved marginal ridge

13. The Dovetail: Retention Form • Dovetail Retention Form • Resists mesial/distal displacement of the casting  • Allows casting to placed only from an occlusal direction  • Placed even at the expense of non-carious grooves

14. Proximal Box • Maintain bur parallel to long axis • Drop bur as you would an amalgam, BUT • Buccal and lingual walls do NOT converge toward the occlusal !! • Walls of box DIVERGE with angle of the bur • Contacts are opened buccally and lingually and 0.5 to 1.0 mm gingivally • NO "S" or reverse curve !

15. Bevels and Flares • Bevels and Flares • Better fit at margins • Lesser angle metal margins are easier to finish to die and/or tooth • Proximal Flare - 40 degree metal margin  • Placed when the restoration angle is greater that 40 degrees.  • Allows a marginal enamel angle of 140 degrees • Buccal wall may be limited by esthetics

16. The Bevel Advantage • Gingival Bevel - 30 degree metal margin • Casting discrepancies at the margins are minimized • Provide firm enamel support for margin (no fragile) • Placed with a GF 11 or flame-shaped finishing bur (#7901) • Bevels

17. The Bevel Advantage =1/2 D

18. Bevels • Occlusal Bevel - 40 degree metal margin • Provides a strong but burnishable margin • Not indicated if the cusp inclines are steep so that a 40 degree angle already will occur • All bevels and flares should "blend"  together to allow a continuous margin.

19. The Inlay Preparation

20. Other Types of Casting

21. Types of Finish Lines

22. The Onlay • Defined • Posterior teeth • Class II involvement • All cusps are "capped" • Indications • Large defective amalgam or resin restorations • Weak buccal/lingual cusps that require splinting • Heavy occlusal wear

23. Other Casting Types • Margin Requirements • All margins shouldbesupragingival • Easy to evaluate and finish the margin • Easier for patient to keep clean • No gingival irritation • except due to: • Existing caries/restorations • Short crowns - retentive walls need 4 mm • Esthetics

24. Bottom Line • General Principles of Partial Veneer Castings: • Necessity to see all surfaces • Weak tooth is splinted • Adequate metal - proper amount of reduction • Esthetics • Smooth junctions between tooth surfaces