principles of cavity prep

Question 1

what is the function of cavity preparation?

Answer 1

to treat disease

Question 2

what is a typodont tooth?

Answer 2

simulated enamel, dentine and caries

Question 3

what 3 things determine cavity design

Answer 3

structure and properties of the dental tissues
the diseases eg caries, perio
properties of restorative materials

Question 4

what factors must be reviewed and reassessed continually when preparing a tooth?

Answer 4

position of caries
extent of caries
shape of prepared cavity
final restorative material

Question 5

what are the classifications for position of caries?

Answer 5

pit & fissure
approximal-posterior/anterior
smooth surface
-caries common at gingival margin due to bad brushing technique
-erosion/abrasion/abfraction/hypoplasia
root

Question 6

when should you intervene?

Answer 6

when lesion is cavitated

when patient cant access lesion for prevention

Question 7

what other situations should you intervene?

Answer 7

when the lesion is into dentine radiographically
the lesion is causing a pulpitis
the lesion is unaesthetic

Question 8

what are the goals for cavity prep?

Answer 8

maximising adhesion
occlusal relationships
ease of px cleaning
properties of materials used

Question 9

what situations would healthy tooth tissue be removed?

Answer 9

material for rest. required it
margins of cavity are in contact with another tooth surface
margins of cavity cross an occlusal contact

Question 10

what are the steps of cavity design and prep?

Answer 10

identify and remove carious enamel
remove enamel to identify the maximal extent of the lesion at the amelodentinal junction and smooth the enamel margins
progressively remove peripheral caries in dentine from ADJ then circumferentially deeper-avoid pulp
remove deep caries from pulp
outline form modification
internal design modification

Question 11

what does outline form modification include?

Answer 11

enamel finishing
occlusion
requirements of restorative material

Question 12

what does internal design modification include?

Answer 12

internal line and point angles

requirements of rest. material

Question 13

how to cut the final cavo-surface margins?

Answer 13

remove enamel that will not be supported by the etch technique
smooth cavosurface margins and line angles
ensure there are no excessively acute line angle transitions and that outline form is smooth and rounded
check for stress concentrators

Question 14

how to do final cavity design?

Answer 14

if existing rest. removed ensure all gone
smooth external enamel sharp line or point angles
create appropriate cavo-surface margin angle
remove internal dentinal sharp line or point angles
check for stress concentrators

Question 15

how should the final seal of the restoration look?

Answer 15

smooth margins
appropriate CSMA
no unsupported tooth tissue
internal anatomy that allows adaption of material

Question 16

what should you do after cutting the cavity, before rest. procedure?

Answer 16

clean cavity to ensure it is free from debris generated during prep

Question 17

how should a restoration be removed?

Answer 17

start from centre and cut towards edge

Question 18

how to detect dentinal caries?

Answer 18

detected as brown stain or softened tissue when using a sharp probe
sound dentine will not stick under probing

Question 19

when can brown staining be left?

Answer 19

if hard to probe

Question 20

how should carious dentine on the pulpal floor be removed?

Answer 20

using the largest instrument which will work
hand held excavator
round bur
chemo-mechanical caries removal
caries detector dyes may help

Question 21

what are the principles of cavity prep?

Answer 21

access
extent
dentinal caries
modification

Question 22

what is the disadvantage of composite?

Answer 22

operator sensitive

Question 23

what are the advantages of composite?

Answer 23

aesthetics
conservation of tooth tissue
support for remaining tooth tissue
adhesion/bonding
command cure
low thermal conductivity
elimination of galvanism

Question 24

what are the disadvantages of amalgam?

Answer 24

does not bond to enamel or dentine
doesn’t support tooth
need to remove healthy tissue for retention and resistance
not tooth coloured
cut dentine may require sealed resin layer
held in cavity by retention and resistance form

Question 25

what is retention?

Answer 25

features of the cavity which prevent the restoration being dislodged in any occlusal direction

Question 26

what gives retention?

Answer 26

anatomical cavity design features

• undercuts
• dovetail
• key
• isthmus

Question 27

what features are needed in design to place an amalgam restoration?

Answer 27

retentive and resistive

Question 28

describe cavity margins in an amalgam restoration?

Answer 28

all cavity margins should be:

• caries free
• free of contact with adjacent tooth
• accessible for cleansing

Question 29

how should the cavity margin/restoration interface be designed?

Answer 29

for maximum strength and minimum leakage
cavo-surface angle 90-120
avoid unsupported enamel or inappropriate CSMA

Question 30

what happens with a high configuration factor?

Answer 30

increased polymerisation contraction stress

Question 31

what is the result of configuration stress?

Answer 31

composite dimensional change
etch/bond stronger than interstitial enamel strength
enamel failure
-acute angles cause breakage leading to plaque traps

Question 32

how to clean cavity before restoration

Answer 32

wash with a mixture of air and water, rinse with chlorhexidine
rinse with water and leave surface moist

Question 33

what is the problem with CSMA?

Answer 33

prisms unsupported by underlying dentine fractured and lost- ditching-plaque trap