3. Finish Line Flashcards
Where is the supra-gingival margin located?
0.5-1mm from surrounding gingiva
How are the esthetics of supra gingival?
Poor
When is a supra-gingival finish line indicated? (2)
- NO ESTHETIC IS COMPROMISED
- ENOUGH HEIGHT OF THE ABUTMENT TOOTH TO HAVE ADEQUATE RETENTION
Which finish line is the most hygenic?
Supragingival
Where is the yuxtagingival margin?
At the level of the gingiva to 0.5mm-1mm under the gingival margin
Main advantage of subgingival finish line?
- Ethetics
Main disadvantage of subgingival finish line?
High risk of biological width invasion
What does increasing the occluso-cervical dimension do for the sibgingival finish line?
Increased retention and resistance
Indications of the subgingival margin? (6)
- Aesthetic (bucally)
- Short clinical tooth (to increase the height and gain retention)
- Subgingival caries.
- Subgingival composites (the FL should always be over healthy structure)
- Subgingival fractures of the tooth.
- Caries propension over the roots.
Contraindications of subgingival margin? (3)
- Scaling and root planning
- Periodontal surgery
- Gingival recession and high clinical crown
How long after scaling and root planning can you prepare a subgingival finish line?
2-3 months
How long after periodontal surgery can you prepare a subgingival finish line?
5-6 months
Define marginal integrity
Configuration of the preparation finish line dictates the shape and bulk of
restorative material in the margin of the restoration
How many microns is a high accuracy marginal integrity?
20-40 microns
How many microns is the maximum clinically acceptable marginal integrity?
100 microns
How do you check the marginal integrity? (2)
Explorer and x-rays
What occupies the marginal integrity?
Cement
What occurs if there is an undercontoured horizontal marginal fit?
Higher risk of caries
What occurs if there is an normocontoured horizontal marginal fit?
Adequate emergence profile
What occurs if there is an overcontoured horizontal marginal fit?
higher tendency for gingival retraction and periodontal issues
The FL must have the correct shape and size so the restoration CAN fulfil
the following requirements: (4)
- marginal integrity.
- structural strength.
- localisation.
- adequate emergency profile
What burs are more commonly used for the finish line? (4)
- 856-016
- 856-012
- 847-016
- 847-016KR
What is the shape of the 856 bur?
Round end tapered diamond
What is the shape of the 847 bur?
Flat end tapered diamond
What are the dimensions of the 856-016 bur?
Base 1.6mm
Tip 1mm
What are the dimensions of the 856-012 bur?
Base 1.2mm
Tip 0.8mm
What bur do you use for chamfer in veneers?
856-012
What are the dimensions of the 847-016 bur?
Base: 1.6mm
Tip: 1.1mm
Whats the difference between the 847-016 bur and the 847-016KR
The 847-016KR has a more rounded angle
What is the 837-012 bur used for?
Occlusal and incisal reduction
What shape is the 858 bur?
Needle shape
What is the 858 bur used for?
Proximal reduction to break contact point
What shape is the 368-023 bur?
Rugby/football
What is the 368-023 bur used for?
Lingual or palatal concavity for anterior teeth
Shape of a cahmfer?
Curved
Depth of a chamfer?
0.5-0.7mm
How conservative is a chamfer?
Very conservative
What bur do you use for a chamfer?
856-016
A chamfer needs ___ at the end of the restoration
metal
Chamfer: with smaller angles…
the margin increases fit
Chamfer: stress?
Less stress at cement area
Indications of chamfer? (5)
- Metal-end restorations (metal collar).
- Lingual or palatal surfaces of PFM crowns.
- low aesthetic demand
- Periodontal teeth ( metallic finishing over cementum)
- Feldspathic veneers(856-012 RK, for a 0.3 to 0.5mm FL)
Whats another name for a deep chamfer? (2)
- Heavy chamfer
- Rounded chamfer
Deep chamfer: Angle at the margin ?
90 degrees approximately
What is the difference between a deep chamfer and normal chamfer?
Inner shape has a smaller radius than the normal chamfer
Indications of a deep chamfer? (5)
- Full coverage crowns
- proximal surfaces of PFM crowns
- Crowns when long teeth (metal margin)
- Porcelain veneers
- CAD/CAM
How do you prepare a chamfer for a full coverage crown?
- Lingual/buccal PFM 0.5-0.7mm (metal collar)
- PFM posterior teeth buccal surface when esthetics are not jeopardized 1.2mm
How many mm should the deep chamfer of porcelain veneers be?
0.3-0.5mm
What bur do we use to prepare a butt-shoulder?
Flat-tip cylinidrical bur
When do we use a butt shoulder finish line?
Was used for all ceramic crowns
What is the cavosurface angle of a buttshoulder finish line?
90 degrees
What is the depth and angle at the margin of a butt shoulder finish line?
90 degrees
1.0-1.2mm deep
What are the indications of a butt-shoulder finish line? (2)
- Jacket crowns (all ceramic feldspathic)
- Labial surface of PFM anterior crowns
Which finish line is not used anymore?
Butt shoulder
What are the disadvantages of the butt shoulder finish line? (4)
- CAD/CAM scanners read it badly
- least conservative
- 90 degree inner angle creates tension making it difficult for alloy casts or porcelain to fit well
Which finish line is the least conservative?
Butt-shoulder
What is the angle at the margin for a rounded shoulder?
93 degrees at axial wall and gingival wall
How does the inner angle of a rounded shoulder compare to the butt shoulder?
inner angle is rounded in rounded shoulder
What is the benefit of using the rounded shoulder finish line?
- reduces tension and stress concentration over the tooth
- Good CAM/CAM scanning
- Good space for porcelain
- more conservative than butt
What bur do we use to prepare a rounded shoulder?
847-016KR cylindrical with rounded tip
Indications of a rounded shoulder? (3)
- Full ceramic crown (1mm full perimeter)
- Labial surface of upper anterior PFM crown (or posteriors when esthetics jeopardized)
- PFM anterior crowns/bridges
How many mm is a rounded shoulder in full ceramic crowns?
1mm all around
How many mm is a rounded shoulder in PFM crowns?
1.0-1.5mm
Rounded finish lines and rounded angles of the prep facilitate.. (2)
- laboratory fabrication and
procedures - restoration fit
Rounded finish lines and rounded angles of the prep reduces …
Stress concentration
Rounded finish lines and rounded angles of the prep is easier for.. (2)
- taking impressions
- capture working digitally/using CAD/CAM
Rounded finish lines and rounded angles of the prep has less..
- air bubble trapping while pouring
- air trapping when investing the die with wax pattern
When do we use a ceramic shoulder? (2)
- Porcelain labial shoulder
- PFM anterior sector
What is the benefit of ceramic shoulder?
- High aesthetic
- allows yuxtagingival finish line
- metal only covers axial wall
Which finish line is the best option from an esthetic point of view?
Ceramic shoulder
What is the fit for a ceramic shoulder?
acceptable fit 45 microns
Metal margin finish line? (3)
- 0.2-0.3 mm showed labially.
- To be placed subgingivally.
- Doesn’t warp because of the bulk of metal at the shoulder.
What is the purpose of a shoulder with bevel?
Diminishing the marginal discrepancy
What is the purpose of a feather/knife edge?
Allows acute margin of metal but can create complications
What finish line do you use for PFM crowns buccal/labially with small esthetic concern? (2)
- Deep chamfer (porcelin-metal margin 0.4mm metal collar)
- Shoulder with bevel (porcelin-metal margin 0.5mm metal collar)
What finish line do you use for PFM crowns buccal/labially with medium esthetic concern?
Rounded shoulder (porcelin-metal margin 0.2-0.3mm metal collar)
What finish line do you use for PFM crowns buccal/labially with high esthetic concern?
Rounded shoulder (porcelain margin)
What finish line do you use for PFM crowns lingually ? (2)
- chamfer (metal margin)
- deep chamfer (metal margin)
What finish line do you use for PFM crowns proximally?
- Deep chamfer (metal margin)
- Rounded shoulder (metal margin)
What finish line do you use for all ceramic crown porcelain jacket? (2)
- Rounded shoulder
- Chamfer
1mm both
What finish line do you use for all ceramic crown porcelain jacket full ceramic crown? (2)
- Rounded shoulder
- Rounded chamfer
1mm both
What finish line do you use for all ceramic crown porcelain veneer?
Chamfer (0.3-0.5mm)