When do we use an S curve?
In class II prep
Purpose of an S curve:
Exposes the ends of enamel rods for a strong bond and gives a better seal
gingival bevel
Why do we place a gingival bevel?
exposes ends of enamel rods for stronger bond and 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 at the isthmus of a class II?
Lack of gingival bevel
When and why would we extend margins of the box portion of preparation?
Sharp axiopulpal line angle (this is why we bevel it)
Appropriate exit angles of buccal, lingual, and gingival walls of amalgam:
90 degrees on all
Appropriate exit angles of buccal, lingual, and gingival walls of composite:
buccal & lingual- flare greater than 90 degrees
gingival- 90 degrees
when would you 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 (bc no enamel rods are present here)
Where do you place retention grooves in a box?
-buccal-axial line angle and lingual-axial line angle
- just inside the DEJ, entirely in dentin
When placing a retention groove into a box, the groove does not go into the:
gingival floor
Label this photo:
A: gingival-axial line angle
B: buccal-gingival line angle
C: buccal-gingival axial point angle
D: buccal axial line angle (w/optional retention groove)
E: axiopulpal line angle
F: lingual-axial line angle (w/optional retention groove)
G: lingual-gingival axial point angle
H: lingual-gingival line angle
List the advantages of composite resin: (6)
Why is it advantageous that composite resin involves bonding? (2)
Why is it advantageous that composite resin does not incorporate metal? (3)
List order of expense from least to greatest:
- crown & inlays/onlay
- amalgam
- composites
What are the disadvantages of composite resin restorations? (9)
What do we mean by “composite cannot support occlusion”
must have tooth supported occlusion on marginal ridges and cusp tips)
What is the purpose of using a wedge in a class II preparation?
closes the margin at the gingival of the box and prevents overhang
When using a tofflemire retainer band the narrower opening faces:
gingivally
What way should the opening slits of the tofflemire face?
gingival
Why should the opening slits of the tofflemire face gingivally?
so when you release the tofflemire it comes off of the tooth towards the occlusal surface