Week 2 - Class II Prep and Restorations Flashcards
what is the purpose of the s curve
- 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
how big should the buccal contact, gingival contact and lingual contact be open in a class II amalgam
- buccal: 0.2-0.5mm
- gingival: at least 0.5mm
- lingual: 0.2-0.5mm
what does the 0.5 mm open gingival contact ensure
the caries susceptibel area below the contact is clear
what should be the degree of convergence for each the buccal and lingual wall in class II
3-4 degree convergence
what should you use to remove undermined enamel hooks
enamel hatchet
what should you use to smooth the gingival floor
56 or 57 bur or 245
how are enamel rods inclined
gingivally
how should you smooth the gingival floor with a 56 o 57
- 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
how should you smooth the gingival floor with a 245 bur
- 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
how should you bevel the axiopulpal line angle
- use flat end of a 56 or 57 straight fissure bur to put a 45 degree bevel on the axiopulpal line angle
what is the benefit of approaching the axiopulpal line angle to bevel through an open portion of the box
less likely to nick the surrounding tooth structure compared to using the side of a 169 or 7902 flame bur
what does a reverse S curve starting too far distally cause
weakening cusp
what does no reverse S curve cause
weak amalgam
what does flare for reverse S curve starting too far mesially cause
amalgam prone to fracture
what does a concave axial wall cause
compromised resistance and retention form
what is the axial wall depth for a composite
1-1.5mm
what should be beveled in a composite prep
- lingual wall
- gingival bevel
- axiopulpal line angle
what is the benefit of keeping margins in enamel
minimize microleakage and post op sensitivity
what are the main differences between composite and amalgam preps
- composite preps can be more conservative
- bonding capability of composite may strengthen supporting tooth structure
what are the contraindications to composite
- occlusion
- restorations extending to root surface
- deep sub gingival margins
what are the advantages of composite
- esthetic
- conserves tooth structure
- bonding
- no metal
- can be economical
- prep can be more forgiving
what are the advantages of the bonding in composites
-reduced microleakage and recurrent decay
- increased retention
what are the advatnages of no metal in composites
- no mercury arguments from patients
- no corrosion
- no galvanic shock
what are the disadvantages of composite
- 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
why should you not use a clear matrix band with composite
- too much flash
- poor contours
- reservoir for moisture
- overall terrible
what can you do to avoid dessicating dentin
place a cotton pellet over it
what is the oxygen inhibited layer
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
what are the new things to be considered with composite
- interproximal contacts
- voids
-light
-polymerization stress
how do you insert the band into the tofflemire retainer
- 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
where is the wider opening in the loop of the matrix band
toward the occlusal of the tooth
where is the slot vice in relation to the tooth
toward the gingival of the tooth
when is the retainer of the tofflemire on the lingual side of the tooth and what does it require
- useful with missing buccal tooth structure
- requires use of a contra angle retainer
what is the purpose of the wooden wedge
to close the margin at the gingival of the box and prevent overhand
when would double wedging be done
if you have a wide interproximal space and a gingivally deep box
when would you vertically stack two wedges
in event of gingival recession and a proximal box of moderate depth
when would you use interproximal fluting
root concavity
where should the occlusal stop be in MI and why
bottom of the fosaa to put long axis forces on the teeth
what happens if you carve grooves so deep that no stop is created in MI
the teeth may later erupt to re achieve contact but the forces may not be down the long axis of the teeth
