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Flashcards in Lecture 2 Deck (16)
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1
Q

three basic principles of tooth preparation

A

biologic (conservation of tooth structure)
mechanical
esthetic

2
Q

the poor appearance of some metal-ceramic restorations is often due to what

A

insufficient porcelain thickness

3
Q

what are the parameters for the biologic width?

A

3mm btw restoration and bone

4
Q

the more accurately the restoration is adapted to the tooth, the less the chance for what?

A

recurrent caries or periodontal disease

5
Q

what is the recommended convergence angle of the axial walls?

A

6 degrees

6
Q

the location of the finish line for #21 should be ____ and #19 should be

A

.75mm (bc of the shoulder)

.5mm (typical chamfer)

7
Q

which POW should you choose when making an FPD?

A

always choose the molar POW

8
Q

the first plane grooves should be what?

A

parallel to the long axis of the tooth

9
Q

how many planes of reduction are there for a #21

A

3 (fxnal cusp, 1rst plane, second plane)

10
Q

the shoulder should be how long?

A

1.2-1.5 mm

11
Q

you should prepare all abutments at the same time to minimize what?

A

undercuts

12
Q

retention form

A

forces parallel to long axis

13
Q

resistance form

A

lateral forces (occlusal forces)

14
Q

what angle should the shoulder be?

A

120 degrees

15
Q

advantages of supra gingival margins

A

easily finished
impressions more easy
restoration can be more easily evaluated
more easily cleansed

16
Q

indications of sub gingival margins

A
  • presence of caries, cervical lesions, or restorations that extend subgingivally
  • need for additional retention
  • root sensitivity
  • need to hide the margin of a metal-ceramic crown for esthetics on anteriors