Quiz 1 Flashcards
What three considerations must you take when thinking about placing a crown?
- Biological
- Mechanical
- Esthetic
What mechanical considerations must you take?
- Resistance form
- Retention form
- Preventing deformation of the restoration
What are some different types of crowns?
- CVC - Complete Veneer Crown
- MCC - Metal ceramic crown
- ACC - All ceramic crown
- Zirconia
What are some indications for a single crown?
- Extensive coronal destruction
- Short clinical crowns
- Endodontically treated teeth
- Maximum retention and resistance are needed
- Correction of axial contours
What are some contraindications for single crowns?
- Wherever there is still an intact buccal or lingual wall
- If less than maximum retention and resistance are needed
- If objectives can be met with a more conservative restoration
What are the pros of crown restorations?
- Greater retention due to all axial surfaces being included
- Greater resistance
- Allows operator to modify axial and occlusal contours
What are the cons to crown restorations?
- Extensive tooth structure removal with possible adverse effects on pulp and periodontium
- Gingival inflammations
- No more eclectic vitality testing
- Esthetics of metal
What is the finish line?
Terminal most cervical portion of the preparation
What is a chamfer?
A finish line design in which the gingival aspect meets the external axial surface at an obtuse angle
What is the axial inclination?
The alignment of the long axis of a tooth to a selected plane
Where should the long axis be determined from?
The gingival third of the tooth
What is the convergence angle?
The taper of a crown prep. The angle formed between opposing axial walls
What is the ideal convergence angle?
6 degrees
What is the POW?
Path Of Withdrawal: the specific direction in which the crown will be placed and removed
What is the major point of reference when determining the POW?
Long axis of tooth
What is an undercut?
Any irregularity in the wall that prevents seating or removal
What are the steps of a CVC prep?
- Occlusal guide grooves
- Occlusal reduction
- Axial guide grooves
- Buccal and lingual reduction
- Interproximal reduction
- Finishing and evaluation
What are the recommended dimensions of a CVC prep?
Central Groove: 1.0mm
Non-functional cusp: 1.0mm
Functional cusp: 1.5mm
Chamfer width: 0.5mm
What is the purpose of the functional cusp bevel?
Create the correct contours and provide proper thickness of material
What are the advantages and disadvantages of a chamfer finish?
Advantage: distinct margin, adequate bulk, easier to control
Disadvantage: care needed to avoid unsupported lip of enamel
What can cause inadequate retention and retention form in the prep?
- Excessive convergence angle
- Inadequate height of axial walls
- Insufficient surface area
Adaptation:
The degree of proximity of a restorative material to a tooth preparation
Axial inclination:
The alignment of the long axis of a tooth to a selected plane, often the horizontal plane
What is distinctive about a chamfer?
Gingival aspect meets the external axial surface at an obtuse angle
What is the clinical crown?
Clinical crown: visible crown
What is a shoulder finish line?
Gingival part of prep meets axial surface at a right angle
What is the functional bevel for?
Ensures correct contours, correct convergence, and adequate material thickness
What can cause an undercut?
- Depression in axial wall
2. Improper convergence of axial walls
Difference between retention and resistance form?
Retention: resist removal along POW
Resistance: prevent removal by apical or oblique forces and occlusal forces
What is the recommended range of convergence?
2-10 degrees (6 is ideal)
What can cause a failed gingival margin?
- Chamfer too narrow (.5mm ideal)
- Cavo-surface line angle can’t be determined in lab
- Chamfer is rough
- Undercut
What are some causes of poor resistance and retention?
- Excessive convergence
- Inadequate axial wall height
- Insufficient surface area
