Week 2 - Class II Prep and Restorations

Question 1

what is the purpose of the s curve

Answer 1

• creates smoothly rounded form to improve resistance to fracture
• keeps narrowest part of preparation away from axiopulpal line angle to improve resistance to fracture
• allows preparation to break contact while allowing buccal wall to meet the tooth surface at a 90 degree exit angle

Question 2

how big should the buccal contact, gingival contact and lingual contact be open in a class II amalgam

Answer 2

• buccal: 0.2-0.5mm
• gingival: at least 0.5mm
• lingual: 0.2-0.5mm

Question 3

what does the 0.5 mm open gingival contact ensure

Answer 3

the caries susceptibel area below the contact is clear

Question 4

what should be the degree of convergence for each the buccal and lingual wall in class II

Answer 4

3-4 degree convergence

Question 5

what should you use to remove undermined enamel hooks

Answer 5

enamel hatchet

Question 6

what should you use to smooth the gingival floor

Answer 6

56 or 57 bur or 245

Question 7

how are enamel rods inclined

Answer 7

gingivally

Question 8

how should you smooth the gingival floor with a 56 o 57

Answer 8

• bur has sharp edges that leave sharp internal line angles that must be rounded
• remaining undermined enamel on gingival margin will need to be trimmed away with hand instrument

Question 9

how should you smooth the gingival floor with a 245 bur

Answer 9

• bur has slightly rounded edges leaving more roundness at the internal line angles
• more difficult to smooth gingival floor with this than the 56 or 57
• need to use hand instrument to remove undermined enamel

Question 10

how should you bevel the axiopulpal line angle

Answer 10

• use flat end of a 56 or 57 straight fissure bur to put a 45 degree bevel on the axiopulpal line angle

Question 11

what is the benefit of approaching the axiopulpal line angle to bevel through an open portion of the box

Answer 11

less likely to nick the surrounding tooth structure compared to using the side of a 169 or 7902 flame bur

Question 12

what does a reverse S curve starting too far distally cause

Answer 12

weakening cusp

Question 13

what does no reverse S curve cause

Answer 13

weak amalgam

Question 14

what does flare for reverse S curve starting too far mesially cause

Answer 14

amalgam prone to fracture

Question 15

what does a concave axial wall cause

Answer 15

compromised resistance and retention form

Question 16

what is the axial wall depth for a composite

Answer 16

1-1.5mm

Question 17

what should be beveled in a composite prep

Answer 17

• lingual wall
• gingival bevel
• axiopulpal line angle

Question 18

what is the benefit of keeping margins in enamel

Answer 18

minimize microleakage and post op sensitivity

Question 19

what are the main differences between composite and amalgam preps

Answer 19

• composite preps can be more conservative
• bonding capability of composite may strengthen supporting tooth structure

Question 20

what are the contraindications to composite

Answer 20

• occlusion
• restorations extending to root surface
• deep sub gingival margins

Question 21

what are the advantages of composite

Answer 21

• esthetic
• conserves tooth structure
• bonding
• no metal
• can be economical
• prep can be more forgiving

Question 22

what are the advantages of the bonding in composites

Answer 22

-reduced microleakage and recurrent decay
- increased retention

Question 23

what are the advatnages of no metal in composites

Answer 23

• no mercury arguments from patients
• no corrosion
• no galvanic shock

Question 24

what are the disadvantages of composite

Answer 24

• low modulus of elasticity
• porous
• more technique sensitivie placement
• more time consuming placement
• microleakage
• may stick to instrument, resulting in voids
• cant place in bulk
• expensive compared to amalgam

Question 25

why should you not use a clear matrix band with composite

Answer 25

- too much flash - poor contours - reservoir for moisture - overall terrible

Question 26

what can you do to avoid dessicating dentin

Answer 26

place a cotton pellet over it

Question 27

what is the oxygen inhibited layer

Answer 27

the sticky uncured layer left of the surface - oxygen in the air interferes with polymerization on surface of composite - this facilitates bonding to the next layer added

Question 28

what are the new things to be considered with composite

Answer 28

- interproximal contacts - voids -light -polymerization stress

Question 29

how do you insert the band into the tofflemire retainer

Answer 29

- turn the inner nut counterclockwise until slot vice is about 1/4 inch from the guide channels - hold the inner nut and turn the outer nut clockwise until the pointed end of the spindle is free of the slot in the slot vice - double the band back on itself forming a loop - insert into the slot vice and direct it through one of the three guide channels and tighten spindle

Question 30

where is the wider opening in the loop of the matrix band

Answer 30

toward the occlusal of the tooth

Question 31

where is the slot vice in relation to the tooth

Answer 31

toward the gingival of the tooth

Question 32

when is the retainer of the tofflemire on the lingual side of the tooth and what does it require

Answer 32

- useful with missing buccal tooth structure - requires use of a contra angle retainer

Question 33

what is the purpose of the wooden wedge

Answer 33

to close the margin at the gingival of the box and prevent overhand

Question 34

when would double wedging be done

Answer 34

if you have a wide interproximal space and a gingivally deep box

Question 35

when would you vertically stack two wedges

Answer 35

in event of gingival recession and a proximal box of moderate depth

Question 36

when would you use interproximal fluting

Answer 36

root concavity

Question 37

where should the occlusal stop be in MI and why

Answer 37

bottom of the fosaa to put long axis forces on the teeth

Question 38

what happens if you carve grooves so deep that no stop is created in MI

Answer 38

the teeth may later erupt to re achieve contact but the forces may not be down the long axis of the teeth