Chapters 1-5 Flashcards
The final shape (form of the tooth, produced using instrumentation) to receive a restoration
preparation
Extracoronal preparation involving the entire clinical crown
complete veneer crown preparation
A cast-gold extracoronal restoration which covers the clinical crown
complete veneer crown (CVC)
The imaginary line along which a casting is moved when it is separated from its single crowns the path of withdrawal should be nearly coincident with the tooths long axis, which can be formed by opposing axial surfaces in third of the tooth
Path of withdrawal (POW)
Part of a crown preparation 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 the unprepared portion of the tooth structure. It extends around the most cervical portion of the tooth prep
chamfer
The junction of the prepared (cut) to unprepared (uncut) tooth structure. This is an external line angle.
cavo-surface line angle
Grooves placed on the surface of the tooth to provide a reference to determine when sufficient tooth structure has been removed
depth orientation grooves
A wide bevel placed on the functional cusps (buccal for mandibular and lingual for maxillary)
Functional cusp bevel
A crown preparation is said to be undercut if a wax pattern cannot be withdrawn from its die without distortion. What are two things that may cause this?
1.) a depression in the axial wall, cause, for example, by a carious lesion
2.) diametrically opposed axial walls that do not converge occlusally caused by improper angulation of the cutting instrument
(type 1 can usually be corrected with a base material while type 2 must be further reduced)
The distance between the occlusal surface of the prepared tooth and the occlusal surface of the opposing tooth. This clearance is evaluated during excursive jaw movements as well as in intercuspal position
occlusal clearance
The characteristics of the tooth preparation which tends to resist the removal of a restoration along its path of withdrawal
retention form
The characteristics of a tooth prepartation which tends to prevent dislodgment of a seated restoration by forces directed in an apical or oblique direction. It works through the use of occlusal forces.
resistance form
What are the advantages of CVCs?
- high strength
- longevity
- high resistance to displacement
- ability to modify axial contours and occlusion
Disadvantages of CVCs?
- display of metal
- removal of tooth substance
- vitality testing
- margin close to gingival tissue
Indications for CVCs
- 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
Contraindiction for CVCs
wherever a tooth can be adequately restored with a more conservative restoration
Principles of tooth preps
- conservation of tooth structure
- marginal integrity of the restoration
- retention and resistance
- structural durability
Excess reduction will occur if:
- the tooth is prepared with excessive convergence angle (recommended 2 to 10 degrees)
- the prep does not follow the anatomical features
- the path of withdrawal diverges from the long axis of the tooth
- and excessively wide margin
- excessively gingival extension of the prep
Inadequate marginal integrity will occur if:
- the chamfer is too narrow to provide sufficient bulk of restorative material without over contouring (ideal is 0.5 mm
- the cavo-surface line angle cannot easily be determined during lab procedures
- the chamfer is rough or uneven
- the preparation is undercut causing distortion of the wax pattern
Causes of inadequate retention and resistance are:
- 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
Structural durability acceptable ranges
- functional cusp 1.5 mm (1.3 mm-1.7 mm)
- central groove 1.0 mm (0.8 mm- 1.2 mm)
- non-functional cusp 1.0 mm (0.8 mm- 1.2 mm)
- Chamfer width 0.5 mm (0.4 mm- 0.6 mm)
The 242.6M and 243.6M diamond burs are ____ to produce a chamfer as the bur cuts into the tooth.
hemispherical (leave a 3-4 degree occlusal convergence)
When cutting our silicon reduction guide, the guide should be cut from ____ to ____.
mid-buccal, mid-lingual
Grooves are places ____ mm shallower than the intended tooth reduction to allow finishing and smoothing.
0.2 mm
Interproximally, the prep must extend cervically to the contact area to provide a ___ mm clearance with the adjacent tooth.
0.5 mm
