Comprehensive Exam Material Flashcards
When do we use an S curve?
In a class two preparation
Purpose of an S curve:
- Keeps narrow isthmus away from axiopulpal line angle
- Allows preparation to break buccal contact
- Creates a smooth & rounded outline
- Allows the buccal wall to be 90 degrees to cavosurface margin
Exposes the ends of enamel rods for a stronger bond & gives a better seal:
Gingival bevel
Why do we place a gingival bevel
Exposes ends of enamel rods for stronger bond & better seal
Where do we place a gingival bevel?
At axiopulpal line angle
When we place the gingival bevel at the axiopulpal line angle, this allows for:
Increased resistance to fracture of isthmus of restoration
What is the most common cause of fracture of the isthmus of a class II?
Lack of gingival bevel
When and why would we extend margins of the box portion of a preparation?
Sharp axiopulpal line angle - (this is why we bevel it_
What are the appropriate exit angles of buccal, lingual & gingival walls in an amalgam:
90 degrees on all
What are the appropriate exit angles of buccal, lingual & gingival walls in a composite:
Buccal & Lingual- flare, greater than 90 degrees
Gingival- 90 degrees
When would not need to place a gingival bevel?
Once you get into deeper preparations when enamel is extremely thin or you’re into dentin or cementum (because no enamel rods are present here)
Where do you place retention grooves in a box?
- Buccal-axial line angle & lingual-axial line angle
- Just inside the DEJ, entirely in dentin
When placing a retention groove in a box, the groove does not go into:
Gingival floor
Label the following image:
A) gingival-axial line angle
B) buccal-gingival line angle
C) buccal-gingival axial point angle
D) buccal-axial line angle (with optional retention groove)
E) axiopulpal line angle
F) lingual-axial line angle (with optional retention groove)
G) Iingual-gingival axial point angle
H) lingual-gingival line angle
List the advantages of composite resin: (6)
- Esthetics
- Conservation of tooth structure
- Bonding
- No metal
- Can be economical (compared to crowns inlays/onlays)
- Prep more forging (restoration is not)
Why is it advantageous that composite resin incorporates bonding: (2)
- Reduced microleakage and recurrent decay
- Increased retention
Why is it advantageous that composite resin does NOT incorporate metal: (3)
- No mercury arguments from patients
- No corrosion
- No galvanic shock
List order of expensive from to least to greatest:
-Crowns & inlays/onlays
-Amalgam restorations
-Composite restoration
- Amalgam
- Composite
- Crowns/inlays/onlays
What are the disadvantages of composite resin: (9)
- Low modulus of elasticity
- Porous
- More technique sensitive placement
- More time-consuming placement
- Microleakage
- Pull back, can create voids
- Expensive compared to amalgam
- Cannot place in bulk
- Cannot support occlusion
What do we mean by “composite cannot support occlusion”
Must have tooth supported occlusion on marginal ridges & cusp tips
What is the purpose of using a wedge in a class II preparation?
Closed the margin in the gingival of the box & prevents overhang
When using a tofflemire retainer band the narrower opening faces:
Gingivally
What way should the opening slits of the tofflemire face?
Gingivally
Why should the opening slits of the tofflemire face ginivally?
So when you release the Tofflemire it comes off the tooth toward the occlusal surface