principles of cavity prep Flashcards
what is the function of cavity preparation?
to treat disease
what is a typodont tooth?
simulated enamel, dentine and caries
what 3 things determine cavity design
structure and properties of the dental tissues
the diseases eg caries, perio
properties of restorative materials
what factors must be reviewed and reassessed continually when preparing a tooth?
position of caries
extent of caries
shape of prepared cavity
final restorative material
what are the classifications for position of caries?
pit & fissure approximal-posterior/anterior smooth surface -caries common at gingival margin due to bad brushing technique -erosion/abrasion/abfraction/hypoplasia root
when should you intervene?
when lesion is cavitated
when patient cant access lesion for prevention
what other situations should you intervene?
when the lesion is into dentine radiographically
the lesion is causing a pulpitis
the lesion is unaesthetic
what are the goals for cavity prep?
maximising adhesion
occlusal relationships
ease of px cleaning
properties of materials used
what situations would healthy tooth tissue be removed?
material for rest. required it
margins of cavity are in contact with another tooth surface
margins of cavity cross an occlusal contact
what are the steps of cavity design and prep?
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
what does outline form modification include?
enamel finishing
occlusion
requirements of restorative material
what does internal design modification include?
internal line and point angles
requirements of rest. material
how to cut the final cavo-surface margins?
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
how to do final cavity design?
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
how should the final seal of the restoration look?
smooth margins
appropriate CSMA
no unsupported tooth tissue
internal anatomy that allows adaption of material
what should you do after cutting the cavity, before rest. procedure?
clean cavity to ensure it is free from debris generated during prep
how should a restoration be removed?
start from centre and cut towards edge
how to detect dentinal caries?
detected as brown stain or softened tissue when using a sharp probe
sound dentine will not stick under probing
when can brown staining be left?
if hard to probe
how should carious dentine on the pulpal floor be removed?
using the largest instrument which will work hand held excavator round bur chemo-mechanical caries removal caries detector dyes may help
what are the principles of cavity prep?
access
extent
dentinal caries
modification
what is the disadvantage of composite?
operator sensitive
what are the advantages of composite?
aesthetics conservation of tooth tissue support for remaining tooth tissue adhesion/bonding command cure low thermal conductivity elimination of galvanism
what are the disadvantages of amalgam?
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
what is retention?
features of the cavity which prevent the restoration being dislodged in any occlusal direction
what gives retention?
anatomical cavity design features
- undercuts
- dovetail
- key
- isthmus
what features are needed in design to place an amalgam restoration?
retentive and resistive
describe cavity margins in an amalgam restoration?
all cavity margins should be:
- caries free
- free of contact with adjacent tooth
- accessible for cleansing
how should the cavity margin/restoration interface be designed?
for maximum strength and minimum leakage
cavo-surface angle 90-120
avoid unsupported enamel or inappropriate CSMA
what happens with a high configuration factor?
increased polymerisation contraction stress
what is the result of configuration stress?
composite dimensional change
etch/bond stronger than interstitial enamel strength
enamel failure
-acute angles cause breakage leading to plaque traps
how to clean cavity before restoration
wash with a mixture of air and water, rinse with chlorhexidine
rinse with water and leave surface moist
what is the problem with CSMA?
prisms unsupported by underlying dentine fractured and lost- ditching-plaque trap
