CVC Prep Flashcards
The final shape to a restoration (form of the tooth produced by instrumentation)
Preparation
Extracoronal preparation involving the entire clinical crown
Complete veneer crown prep
A cast-gold extracoronal restoration which fits the clinical crown
complete veneer crown (CVC)
The imaginary line along which a casting is moved when it is separated from its single crowns.
should coincide with the tooth’s long axis
Path of Withdrawal (POW)
Part of the crown prep prepared in the long axis of the tooth
can be designated as buccal, lingual, mesial, or distal
axial wall
The angle or taper formed by diametrically opposed axial walls
convergence angle
The cervical junction of the prepared axial wall and unprepared portion of the structure
Extends around the cervical portion of the tooth prep.
Chamfer
Lines formed by the junction of any two tooth surfaces.
Should be rounded in complete crown preps
line angles
Junction between any two axial walls
Axial wall line angle
Junction between the occlusal surface and an axial wall
occlusoaxial line angle
Junction of the prepared to unprepared tooth structure (external line angle)
Cavo-surface line angle
Grooved placed on the surface of the tooth to provide a reference to determine when sufficient tooth structure has been reduced.
depth orientation grooves
A wide bevel placed on the fuctional cusps.
The thickness of the tooth structure removed when preparing this bevel ensures that correct contours of the final restoration can be re-established while providing correct convergence and adequate thickness of restorative materials.
Functional cusp bevel
A crown prep is ___ if a wax pattern cannot be withdrawn from its die without distortion
undercut
What causes undercuts?
- a depression in an axial wall (by caries)
- diametrically opposed axial walls that do not converge occlusally caused by improper angulation of the cutting instrument
How do you correct an undercut caused by a carious lesion?
a base/build up material
How do you correct an undercut caused by improper bur angulation?
requires further tooth reduction
Characteristics of the tooth preparation which tends to resist the removal of the restoration along its POW.
Retention form
Characteristics of a tooth preparation which tend to prevent dislodgement of a seated restoration by forces directed in an apical or oblique direction.
Prevents dislodgement of the restoration by occlusal forces
Resistance form
Name 4 advantages of complete veneer crowns
high strength
longevity
high resistance to displacement
ability to modify axial contours and occlusion
Name 4 disadvantages of complete veneer crowns.
Display of metal
removal of tooth substance
vitality testing (pulp testing)
Margin close to gingival tissue
What criteria does a patient need to be a candidate for a CVC?
- 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
- have a need to provide contours suitable for removable partial denture
What are contraindications of CVCs?
- When a tooth can be adequately restored with a more conservative restoration
- esthetics
What could be examples excess reduction of a CVC prep?
- tooth is prepared with excessive convergence angle
- prep does not follow the anatomical features of the tooth
- POW diverges from the long axis of the tooth
- excessively wide margin
- excessive gingival extension of the prep
What is the ideal convergence angle of a CVC prep?
between 2 and 10 degrees
What is the ideal width of the prep margin?
0.5 mm
How far gingivally should a CVC prep go?
no further than retention form and existing restoration or defects dictate
When might inadequate marginal integrity occur?
- chamfer is too narrow to provide sufficient bulk of restorative material without over contouring
- cavo-surface line angle cannot easily be determined during lab procedures
- chamfer is rough or uneven
- preparation is undercut causing distortion of the wax pattern
What will happen if you have inadequate retention and/or resistance form?
displacement of the restoration
What are some causes of inadequate retention/resistance form?
- excessive convergence angle (greater than 10 degrees)
- inadequate height and surface area of the axial walls
- insufficient surface area to resist tipping of the restoration
What are the recommended dimensions for CVC prep?
Functional cusp - 1.5 mm taken away
Central groove - 1 mm taken away
Non-functional cusp - 1mm taken away
Chamfer width - 0.5 mm
In order, what is the sequence of steps taken to prep a CVC?
- occlusal guiding grooves
- occlusal reduction
- axial guiding grooves
- axial reduction
5 finishing and evaluation
