March 11, 2009 STI

Go for the Gold! Characteristics

Parallelism ○ No undercut areas like in direct restorations

Lost wax techniqueHigher strength than direct restorations Control of contours and good proximal contactsAbility to create acute margins: use less metal,

take away less tooth structure Gold casting alloyMultiple appointments

Considerations

1. BiocompatibilityMost biocompatibleBest long lastingLow reactivity in oral environment

○ No emission of electrons: no corrosion

2. High gold alloys best >75% (wt) gold/platinumLower % gold performs well

Considerations 3. Proximal caries

Extensive involvement ○ Casting transmits energy throughout to hold tooth

together to prevent spread of fracturesControl of contours and contactsDifficult subgingival margins are more properly

restored 4. Facial/lingual

Caries high? Caries rate?Existing restorations: consider full coverage

crown

Considerations

5. Endodontic treatmentConsider an onlayDesign considerations

6. Fractured teethPresence of fracture linesCusp replacement

7. Elimination of electrical or corrosive activity

Considerations

8. Diastema closure and occlusal plane correctionNeed to extend mesial/distal dimensionCorrection of occlusal irregularities

9. Removable prosthodontic abutmentControl of rest seats and guide planesPartial denture forces

Considerations 10. Economics

More chair time neededLaboratory fees

11. Age of patientPulp 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 rateHealth vs. prognosis

12. EstheticsMetal may be seenConsider alternatives: e.g. porcelain

The Inlay Defined

Posterior teethIntracoronal = between the cusps, NOT over

cusps○ Within the cusps (intracoronal)

Class I or Class II (includes marginal ridge)May involve a cusp

IndicationsPatient desireForm and functionRemovable partial denture rest seat

The Inlay Preparation

Convenience formPlane cut tapered fissure burs (No. 271, No.

169L)Obtain uniformly tapered wallsSmooth walls, floor, and seat

“Draw” Concept of Draw

All walls must diverge from gingival to occlusalNo undercutsPath of the “draw” is usually along the long axis10-20 degree divergence—near parallel10 degrees if walls are necessary short20 degrees if walls are long and deepSO: 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 FlaresBetter fit at marginsLesser angle metal margins are easier to finish to

die and/or toothProximal Flare - 40 degree metal margin Placed when the restoration angle is greater that

40 degrees. Allows a marginal enamel angle of 140 degreesBuccal 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

The Bevel Advantage

=1/2 D

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 Inlay Preparation

Other Types of Casting

Types of Finish Lines

The Onlay Defined

Posterior teethClass II involvementAll cusps are "capped"

IndicationsLarge defective amalgam or resin

restorationsWeak buccal/lingual cusps that require

splintingHeavy occlusal wear

Other Casting Types

Margin RequirementsAll 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 surfacesWeak tooth is splintedAdequate metal - proper amount of

reductionEstheticsSmooth junctions between tooth surfaces