Full Metal and All Ceramic Restoration Flashcards
T/F: The restoration can survive in the biologic environment of the oral cavity only if the margins are closely adapted to the Cavo surface finish line of the preparation.
True
•Permits very acute margin of metal •Most conservative preparation type •Flame or needle diamond •Generally contraindicated •Difficult to see; difficult to cast •Other Disadvantage’s \:ØThe axial reduction may fade out instead of terminating in a definite finish line. ØSusceptible to distortion in the mouth when the casting is subjected to occlusal forces.
Knife Edge Finish Line
- Difficult to wax / cast →
- Produces thin margin susceptible to distortion (B) •ORLeads to over-contoured surface (C)
- (Poor emergence profile)
Knife Edge Finish Line
- Indications: very convex axial surfaces; lingual surface of mandibular posteriors; tipped teeth where the axial surface is at an angle >15o
- It will produce a distinct finish line•Less destruction of tooth structure
Knife Edge Finish Line
- Margin Geometry –•(0.3mm) –0.5mm axial depth
- Produces 30o–45o acute metal margin / rounded internal angle
- Margin combines an acute edge(adaptability / seating) with a nearby bulk of metal(strength).
Narrow Chamfer
Round-endor torpedo diamond as axial wall is being produced (1/3 –1/2 diameter of rotary instrument).
•Axial preparation deeper than ½ diameter results in an acute, unsupported “lip” of tooth structure at the margin.
Chamfer margin
Metal-ceramic / Ceramic Crowns •Adequate thickness for ceramic support •Internal rounded angle ↓ stresses •1 –1.2 mm axial depth •Large round-end or chamfer diamond
Heavy chamfer
- 90o Cavo surface angle
- Indications:
- Metal Ceramic Margins
- All-Ceramic Crowns
- Modified (Radial) Shoulder
- Rounded internal axio-gingival line angle
- Flat-end diamond
Shoulder finish line
- Cavosurface angle of 90o
- Supports adequate thickness of ceramic
- Rounded axiogingival line angle –decreased stresses •Finish line most used for ceramic margins
- Generally not used for cast metal
Shoulder finish line
What are the 3 indications for shoulder with bevel?
- Inlay / Onlay
- Partial Veneer Crown
- Metal-Ceramic Crown (metal collar)
The shoulder with bevel is used only when the margin is completely in ____
Metal
_____ is well suited for a complete cast crown:•Ease of placement•Ease of detection on impression; waxing, casting and adaptation to the tooth•Acute in cross section while providing adequate bulk for strength
Chamfer
______ of the tooth surface finish line can prevent close adaptation of the margin.•Rough margin → plaque retention
•Roughness
_____ instrumentation :high speed handpiece / air-waterspraywith diamond burs
•Preparation
______ instrumentation :Slow speed w/ diamond or carbide burs; hand instruments
•Finishing
_______ instrumentation :slow speed with a #4-6 round carbide bur; spoon excavators
•Caries removal