Presentation on theme: "March 11, 2009 STI. Go for the Gold! Characteristics Parallelism ○ No undercut areas like in direct restorations Lost wax technique Higher strength."— Presentation transcript:
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
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
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
Considerations 5. Endodontic treatment Consider an onlay Design considerations 6. Fractured teeth Presence of fracture lines Cusp replacement 7. Elimination of electrical or corrosive activity
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
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
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
The Inlay Preparation Convenience form Plane cut tapered fissure burs (No. 271, No. 169L) Obtain uniformly tapered walls Smooth walls, floor, and seat
“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
Path of Draw The wax pattern (casting) must “draw” from the tooth. There can be NO undercuts or obstruction.
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 tilted lingually. Tilt bur 10 degrees to lingual. Maintain dentin support of uninvolved marginal ridge
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
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 !
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
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
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.
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
Other Casting Types Margin Requirements All margins should be supragingival ○ 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
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