cavity design

Question 1

what is black’s classification of caries based on?

Answer 1

location of the lesion

Question 2

what is class I caries lesion?

Answer 2

pits and fissures on occlusal posterior teeth, occlusal 2/3 of B or L surfaces of posterior teeth, palatal surfaces of anterior teeth.

Question 3

class II classification?

Answer 3

proximal surfaces of posterior teeth

Question 4

what classification is a carious lesion that is on proximal surface of anterior tooth (no incisal edge involvement)

Answer 4

class III

Question 5

what is class Iv?

Answer 5

proximal surfaces of anterior teeth with involvement of incisal edge

Question 6

what class is this? gingival 1/3 of buccal and lingual surfaces of any teeth?

Answer 6

class V

Question 7

what is class VI?

Answer 7

incisal edge of anterior teeth, cusp areas of pos teeth, a bit rare

Question 8

which lesion occurs in high caries risk patients?

Answer 8

class VI

Question 9

what is the difference between primary and secondary caries?

Answer 9

lesion on previously unaffected tooth is primary, lesion around the restoration margins is secondary.

Question 10

what is the term used for prep involving 2-3 surfaces?

Answer 10

compound

Question 11

how do we distinguish internal vs external wall surfaces?

Answer 11

internal are the ones not extending to the external tooth surface.

Question 12

what is a line angle and a point angle?

Answer 12

line angle junction between 2 surfaces, point angle junction between 3 surfaces.

Question 13

what is the junction between a prepared wall and the external tooth surface?

Answer 13

cavosurface margin

Question 14

what is cavosurface angle?

Answer 14

angle between a prepared wall and the external tooth surface

Question 15

what is the rule for access for cavity design?

Answer 15

needs to be minimally invasive, aesthetically acceptable and most direct access to caries

Question 16

which class has direct access?

Answer 16

class I and V

Question 17

what is the access for class III

Answer 17

lingual or palatal as labial should always be preserved

Question 18

how is the alignment of rotary instruments for caries involving the occlusal or proximal surfaces ?

Answer 18

parallel to the long axis of the tooth

Question 19

how is the alignment of rotary instruments for caries involving the buccal or lingul/palatal surfaces ?

Answer 19

perpendicular to the affected surface

Question 20

what is outline form?

Answer 20

area of the tooth surface to be included in the prepared cavity, overall outline of the prep determined by the peripheral walls

Question 21

what factors affect outline form?

Answer 21

anatomy of the tooth, extent of the caries, retention and resistance, convenience form

Question 22

what is resistance form/

Answer 22

prevention of fracture of restoration or tooth structure under occlusal forces.

Question 23

what are the factors affecting the resistance form?

Answer 23

depth of the cavity, thickness of the remaining cavity walls, internal angles, pulpal wall, cavosurface angle

Question 24

what is the required cavosurface angle?

Answer 24

90 degrees for amalgam, composite or cramic restorations. beveled for intracoronal cast-metal restorations.

Question 25

what is retention form?

Answer 25

prevention of restoration displacement from cavity

Question 26

what are some retention form designs?

Answer 26

occlusally lock/dovetail undercuts i.e. narrow and wide lock design. proximally divergent buccal and L walls gingivally, vertical axial wall, horizontal pulpal and gingival walls

Question 27

what is convenience form?

Answer 27

size and shape of the cavity suitable for: prep without damaging adjacent teeth, caries removal, proper matrix placement and application of materials.

Question 28

if the enamel prisms aren't supported by the dentin during prep what form is compromised?

Answer 28

resistance form

Question 29

why is the specified cavosurface angle important for amalgam prep?

Answer 29

because of low edge strength of amalgam and glass cermic

Question 30

what does the external wall finishing step entail?

Answer 30

cavosurface completion which includes beveling and removalof unsupported enamel to avoid chipping

Question 31

what does cavity debridement entail?

Answer 31

residues of oil from handpieces, bacterial biofilm, lose debris etc. it needs to be cleaned with water/air or cleaning substances for better bonding of materials.

Question 32

what is the purpose of beveling in cavity prep?

Answer 32

to remove unsupported enamel rods and increase bonding surface

Question 33

why is beveling not recommended for amalgam restorations?

Answer 33

amalgam has low edge strength so bevel could create a fracture prone surface

Question 34

at what angle is bevel typically created?

Answer 34

15-45 degrees

Question 35

where is beveling usually used?

Answer 35

anterior teeth for aesthetic gradual transition

Question 36

do we have beveling in enamel margins of class V?

Answer 36

yes but not if the margin extends onto cementum

Question 37

are all lesion types carious?

Answer 37

no we also have non-carious lesions

Question 38

does cavity design depend on the defect extent or restorative material used?

Answer 38

both and it needs to be minimally invasive

Question 39

when in cavity prep we use pear shaped diamond bur?

Answer 39

for access and outline form

Question 40

do we need retention and resistance forms to be achieved for class V ?

Answer 40

no

Question 41

what we use for caries removal in dentin?

Answer 41

round carbide bur

Question 42

when do we use gingival margin trimmer/enamel hatched in cavity prep?

Answer 42

to remove weakened enamel at margins

Question 43

what are some cases where we don't need a cavity prep?

Answer 43

non carious cervical lesions, slight roughening of dentine then consider a retention groove and then bevelling for composite.