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
•Raising pulp temperature 6oC ↑pulp death by____ %
15%.
•Increases of 10oC →___ % incidence of pulp death •
95%
§Use copious water spray to cool dentin / pulp
§Use sharp burs / diamonds / high speed, light pressure
§Do NOT marginate crowns “dry”
§Prepare teeth as quickly as feasible / avoid desiccation
Decrease temp
•Remove enamel and dentin by _____
grinding
_____ burs
•milling cutters that sheartooth structure from surface
•cut precise preparation features and smooth surfaces in enamel and dentin
•Tungsten carbide burs
_____ drills
•cutting edges on the tip and fluted sides
•bore small-diameter holes in dentin for pins
Used for core buildups
•Twist drills
____ instruments smoothly finish enamel finish lines
Hand instruments
Advantages of _____ Crowns
1) Complete coverage affords greatest retention and resistance form
2) Allows for the greatest change in esthetic tooth form and occlusion
3) Makes it successful in a wide range of situations such as tooth form or alignment is not ideal and therefore a less than perfect tooth preparation will be a likely result
Full metal crowns
Disadvantages of ______Crowns
1) These crowns are not esthetic to many people and therefore they are often limited to non-visible areas of the mouth
2) They require more extensive tooth preparation than partial coverage crowns
3) If the finish line is subgingival around the entire tooth, it is more likely there will be a less than optimal gingival response
Full Metal Crowns
What type of margin is used on full metal crown?
Chamfer
What is the width of the chamfer for full metal?
.3-.5 mm
Line angles are ______ to facilitate pouring impressions without trapping air bubbles and investing wax patterns without air inclusions.
rounded
Reduction for in a full metal crown prep for occlusal clearance of ____ - _____ mm
1.0 –1.5 mm
What should the TOC of the axial reduction be in a full metal crown prep?
10-20 degrees
Advantages of _______ Crowns
1)Esthetic potential / translucency2)Good tissue response
All ceramic crowns
Disadvantages of ______ crowns:
1) Reduced strength
i. No metal substructure
ii. Brittle nature of material
2) Substantial tooth reduction required
3) Technique sen sitive
i. Clinical tooth preparation
ii. Resin cementation
4) Opposing tooth wear
5) Greater fracture potential –posteriors ( Zirconia ?)
6) Fixed partial dental prostheses limitations (Zirconia ??)
All ceramic crowns
Indications of _______ crowns
1)High esthetic requirement2)Favorable distribution of occlusal load3)Optimal tooth preparation is possiblei.Ceramic supportii.Circumferential shoulder or heavy chamfer4)When a more conservative restoration is not indicated
All ceramic crowns
Contraindications of _____ crowns
1) Molar teeth (FC Zirconia)
i. Increased occlusal load
ii. Decreased esthetic demand
2) Unfavorable occlusion
i. Anterior: edge-edge or cervical 1/5
ii. Bruxism / clenching
3) Inadequate tooth length for support
i. Ceramic thickness >2-3 mm
ii. Short clinical crowns
4) Inability to produce uniform circumferential margin
All ceramic crowns
How much incisal reduction is there on a glass ceramic crown?
2-2.5mm
How much facial axial reduction is there on a glass ceramic crown?
1.2-1.7mm
How much lingual axial reduction is there on a glass ceramic crown?
1-1.2mm
How much marginal reduction is there on a glass ceramic crown?
1-1.2mm
What should you use for glass ceramic crowns on darker stained teeth?
Zirconia core
•What are the 2 Methods of strengthening brittle materials in all ceramic crowns?
- Reinforced Glass Ceramics; Polycrystalline -Zirconia
2. CAD-CAM
What are the 4 Methods of design to optimize success in all ceramic crowns?
- Management of occlusal forces
- Restoration design and material
- Cementation (resin bonding)
- Tooth preparation design
Layered or Monolithic•Indications: •Anterior / Posterior crowns •Anterior FDP •Inlays / Onlays, Veneers •Strength: 360-500 Mpa(Moderate) •Resin cementation •Requires 1.5-2.0mm occlusal thickness and 1mm should
Particle-filled Glass-ceramics
