CVC Intro (22) Flashcards
Preparation definition
The final shape to receive a restoration
Complete veneer crown preparation
Extracoronal preparation involving the entire clinical crown
Complete veneer crown
A cast-gold extracoronal which covers the clinical crown
Path of withdrawal
The imaginary line along which a casting is moved when it is separated from its single crowns preparation
Should be nearly coincident with the tooth’s long axis
Want it to be +/- 5 degrees
Axial wall
Part of a crown prep prepared in the long six of the tooth - can be designated as buccal, lingual, mesial, or distal
Convergence angle
The angle or taper formed by diametrically opposed axial walls
Should be ~6 degrees
Chamfer
The cervical junction of the prepared axial wall and the unprepared portion of the tooth structure.s. Extends around the most cervical portion of the tooth prep.
Line angles
Lines formed by the junction of any two tooth surfaces. Should be rounded in a CVC prep
Axial wall line angle
The junction between 2 axial walls
Occlusoaxial line angle
The junction between the occlusal surface and an axial wall
Cavosurface line angle
The junction of prepared and unprepared tooth
This is an external line angle
Depth orientation grooves
Grooves placed on the surface of the tooth to provide a reference to determine when sufficient tooth structure has been reduced
Functional cusp bevel
A wide bevel placed on the functional cusps, the thickness of which ensures that correct contours of the final restoration be re-established while providing correct convergence and adequate thickness of materials
Undercut
A crown preparation is undercut if a wax pattern cannot be withdrawn from its die without distortion
Occlusal clearance
The distance between the occlusal surface of the prepared tooth and the occlusal surface of the opposite tooth.
This is evaluated during excursive jaw movements as well as in as well as in intercuspal position
Retention form
The characteristics of the tooth preparation which tends to resist the removal of a restoration along its path of withdrawal
Resistance form
The characteristics of a tooth preparation which tends to prevent dislodgment of a seated restoration by force in an optical or oblique direction.
CVC Advantages
High strength
Longevity
High resistance to displacement
Ability to modify axial contours an occlusion
CVC Disadvantages
Display of metal
Removal of tooth substance
Vitality testing
Margin close to gingival tissue which can lead to inflammation
CVC indications
Extensive destruction by caries or trauma Endodontically treated teeth Large existing restorations Maximum retention needed Recontouring of axial surfaces Correction of malinclination Correction of occlusal discrepancies To provide contours suitable for a removable partial denture
CVC contraindication
Wherever a tooth can be adequately restored with a more conservative restoration
Principles of tooth preparation
Conservation of tooth structure
Marginal integrity of the restoration
Adequate retention and resistance
Structural durability
Conservation of tooth structure
Minimum tooth reduction compatible with adequate strength and correct contour
Marginal integrity of the restoration
The tooth restoration interface at the gingival margin is a potential site of failure due to cement dissolution or roughness. The prep should be designed to enable a smooth, strong, well-adapted casting to be provided
Excessive tooth reduction will occur if…
- the tooth is peeped with excessive convergence
- the prep does not follow the anatomy of the tooth
- the POW diverges from the long axis of the tooth
- Excessively wide margin
- Excessive gingival extension
Inadequate marginal integrity will occur if…
- The chamfer is too narrow to provide sufficient bulk of restorative material without over contouring
- The cavo-surface line angle cannot easily be determined during laboratory procedures
- The chamfer is rough or uneven
- The preparation is undercut causing distortion of the wax pattern
Causes of inadequate retention and resistance
- Excessive convergence angle
- Inadequate height and surface of the axial walls
- Insufficient surface area to resist tipping
Functional cusps recommended and acceptable range
- 5 mm
1. 3-1.7mm
Central groove thickness
- 0mm
0. 8-1.2mm
Non-funcitonal cusp thickness
- 0mm
0. 8mm-1.2mm
Chamfer width
- 5mm
0. 4mm-0.7mm
What should be the difference between the depth orientation depth, and the final prep depth?
0.2mm more shallow
What considerations should be taken into effect
Biological considerations
Mechanical considerations
Esthetic consideration
What biological considerations should be taken?
Prevent damage during tooth prep
Considerations affecting future dental health
Conservation of tooth structure
What mechanical considerations should be taken?
Providing resistance form
Providing retention form
Preventing deformation fo teh prep
What are the indications for a crown?
Extensive coronal destruction Short clinical crowns Endo treated Maximum retention and resistance are needed Correction of axial contours
What are contraindications for a crown?
Wherever an intact buccal or lingual wall exists
If less than maximum retention and resistance are needed
If objectives can be met with a more conservative restoration
Why does a crown have greater retention than more conservative restorations?
All axial surfaces of the tooth are included
T/F - A crown has greater resistance than a partial coverage restoration on the same tooth
True
T/F - A complete cast crown allows the operator to modify axial tooth contours and the occlusal surface
True
What are the disadvantages of a crown?
Remmoves a large amount of tooth structure
Can have adverse effects on tissue
Display of metal
Vitality testing is not feasible
