Principles of Cavity Preparation Flashcards
What determines cavity design? (3)
- Structure + properties of the dental tissues
- The diseases (dental caries, per disease, tooth surface loss)
- Properties of restorative materials
What steps does the final restorative design rely on? (4)
- The position of the caries
- The extent of the caries
- The shape of the prepared cavity
- The final restorative material
What areas can caries be found? ( 4)
- Pits and fissures
- Approximal:
- Posterior
- Anterior - Smooth surface
- Root
When should a clinician intervene with a lesion? (2)
- When the lesion is cavitated
2. When the patient can’t access the lesion for prevention
When should a clinician CONSIDER a restoration? (3)
- The lesion is into dentine radiographically
- The lesion is causing a pulpitis
- The lesion is unaesthetic
What is the exception for when healthy tooth tissue CAN be removed? (3)
- The material used for the restoration requires it
- The margins of the cavity are in contact with another tooth surface
- The margins of the cavity cross an occlusal contact
State the principles of cavity prep (6)
- Identify + remove carious enamel
- Remove enamel to identify extent of lesion at ADJ + smooth the enamel margins
- Remove peripheral caries in dentine from ADJ first, then circumferentially deeper
- Only THEN remove deep caries over the pulp
- Outline form modification
- Enamel finishing
- Occlusion
- Requirements of the restorative material - Internal design modification
- Internal line + point angles
- Requirements of the restorative material
Checklist for when checking the final cavity design (5)
- Where an existing restoration has been removed, ensure that no traces of restorative material remain
- Smooth enamel line and point angles
- Create appropriate Cavo-surface margin angle
- Remove dentinal sharp line or point angles
- Check for stress concentrators
What should the final seal of the restoration contain? (5)
- Smooth margins
- Appropriate CSMA
- No unsupported tooth tissue
- No stress concentrators
- Internal anatomy that allows adaption of the material
- Smooth line and point angles
How is dentinal caries detected?
Detected as a brown stain
OR
Softened tissue when using a sharp probe
Compare sound dentine and residual carious dentine
Sound dentine shouldn’t yield under probing
Any sticking of the probe indicates residual caries that should be removed
How is caries on the pulpal floor removed?
Using a large bound bur or large hand held excavator
Advantages of composite (6)
- Aesthetics
- Conservation of tooth tissue
- Support for remaining tooth tissue
- Adhesion/bonding
- Low thermal conductivity
- Elimination of galvanism
Define the term galvanism
Electric currents between metal in dental restorations and electrolytes in saliva/dental pulp/ other restorations
Disadvantages of amalgam (4)
- Aesthetics
- Does not bond to enamel or dentine
- Does not support the tooth
- Need to remove healthy tissue to get retention + resistance
What holds amalgam into the cavity?
Retention + resistance form
What prevents amalgam from fracturing?
Adequate bulk - at least 2mm deep
What is retention, in terms of amalgam cavity design?
- Features of the cavity which prevent the restoration being dislodged in any occlusal direction
- Achieved by anatomical cavity design features
e. g. undercuts, dovetails, key, isthmus
NOT REQUIRED FOR ADHESIVE RESTORATIONS
Why are CSA adjusted?
To increase bonding area and ensure no unsupported enamel
REQUIRED FOR ADHESIVE RESTORATIONS
How should the internal dimensions of a amalgam cavity differ from a composite cavity?
Internal dimensions of the cavity should be greater than the access into it
What is the usual CSA angle for amalgam?
Between 90-120 degrees
Why should caries NOT be left at the dentine-enamel junction?
It will result in unsupported enamel and early breakdown of the restorative margin IF micro leakage occurs
Why should the configuration factor be low?
Reduced polymerisation contraction stresses
Configuration stress leads to enamel failure
How should a cavity be cleaned up after cavity prep?
Remove loose enamel + dentine chipping and organic/inorganic dentine debris smeared into the walls of the cavity
BY
Washing the cavity with air + water
Rinse with water and leave surface moist
What can smooth surface caries be a result of? (5)
- Caries
- Erosion
- Abrasion
- Abfraction
- Hypoplasia
The type of tubules in primary dentine
Open tubules
