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Questions and Answers
What is the objective of finishing the internal margin of a cast metal restoration?
What can prevent complete seating of a cast metal restoration?
What should be the minimum space between the internal surface of the restoration and the tooth?
What is the result of a small nodule on the internal surface of the restoration?
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What tool can be used to remove nodules from the internal surface of the restoration?
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What is the purpose of finishing the internal margin of a cast metal restoration?
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What happens if a defect occurs in the internal margin of a cast metal restoration?
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What is the significance of careful examination under magnification in the internal margin of a cast metal restoration?
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What can be removed in the next phase if they are away from the margin?
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Why is it necessary to remove any contact between the internal surface of the restoration and the tooth?
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Study Notes
Finishing of Cast Restorations
- The finishing process involves 7 distinct zones, each requiring specific procedures for proper finishing.
Zone 1: Internal Margin
- Objective: achieve a 1 mm band of metal well-adapted to the tooth surface to prevent cement dissolution.
- Defects in the margin may require a restoration remake.
- Nodules in the fitting surface can prevent complete seating and must be carefully examined and removed.
Zone 2: Intaglio Surface
- No contact should exist between the internal surface of the restoration and the tooth; a space of 25-35 microns is necessary for cement.
- Contacts should be identified and removed to prevent an increase in marginal gap width.
- Nodules can be removed using a small round carbide bur.
Zone 3: The Sprue
- Once the fit is acceptable, the sprue can be removed using a carborundum separating disc.
- Cutting is done around the sprue, then the last part is removed manually by twisting.
- Any excess material is refined with stones.
Zone 4: Proximal Contacts
- Proximal contact areas are adjusted to be correct (or slightly too tight) when evaluated in the mouth.
- Proximal contacts on the stone cast can be minimally relieved by careful scraping with a scalpel.
- Thin Mylar articulating can be used to identify contact areas.
Zone 5: Occlusal Surface
- Occlusal contacts are reestablished in static and dynamic relationships to the opposing arch.
- Occlusal structure must ensure positional stability and satisfy all functional requirements.
- Occlusal contacts are checked with thin Mylar articulating film to ensure they match the design in the waxing stage.
- Occlusal adjustments can be performed with flame-shaped finishing burs or diamonds.
Zone 6: Axial Walls
- Axial walls should be smoothly contoured and highly polished to enable the patient to carry out optimal plaque control.
- The most efficient method of polishing involves a sequence of progressively finer abrasives, each removing the scratches made by the previous grade.
- Light pressure is applied when using abrasives, and the instrument must be kept rotating.
Zone 7: External Margin
- Margin finishing is crucial for a restoration's longevity.
- A highly polished metal surface without ledges or steps as the transition is made from restoration to unprepared tooth.
- Care must be taken not to remove more metal than is strictly necessary without compromising the fit and/or emergence profile of the restoration.
- Finishing should be performed by gently brushing a fine-grit stone over the surface to remove casting roughness, followed by a soft rubber wheel or point, and finally by rouge on a brush.
Checking Occlusal Interferences
- Several marking agents are available to help identify interferences with seating, including water-soluble dyes, solvent-based dyes, powdered sprays, and rouge suspension.
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Description
Learn about the finishing of cast restorations, including adjusting occlusal contacts, polishing, and axial wall finishing. Understand how to achieve optimal plaque control and efficient polishing techniques.
