CSAR 2 pt 1 Flashcards
what is an indirect restoration?
made outwith the mouth
the tooth is prepared and an impression is taken
What is a direct restoration?
Placed directly on the tooth
Soft when placed
Why are indirect restorations done? (4)
- aesthetics
- restore function and form
- structural integrity
- replacing missing teeth
Why can direct restorations be preferred to indirect? (3)
- cheaper
- one visit
- no provision required
What is the evidence base considering indirect and direct restorations?
Indirect vs direct no differences were seen over a 5 year period, however a big direct restoration - difficult to get occlusal contacts
How can indirect restorations be classified
3 categories
- Cementation
- Material
- Coverage
What is the difference between an onlay and a crow?
a crown covers the whole tooth - up to the gingival margin, whereas an onlay only covers a cusp/cusps
what are the different materials restorations may be made of? (4)
- composite
- PFM
- metals (precious and non precious)
- ceramics (etch able - EMAX and non - Zirconia )
What are the methods of retaining an indirect restoration? (2)
Mechanically (P, Zn, GIC, RMGIC)
Adhesive resin cement
what does the elastic modulus of a material show ?
the ability to resist elastic deformation - shows the rigidity
Elastic modulus of
- ceramic
- enamel
- dentine
- composite
- flowable
- 95
- 80
- 14-18
- 10-20
- 4-5
Where do anterior teeth undergo loading?
the palatal surface
Loss of enamel on the palatal surface of an anterior tooth can cause?
decreased stiffness leading to flexion
How can rigidity of enamel be restored (anterior tooth palatally)?
if ceramic is used it restores rigidity to normal, if composite, it improves it but does not restore to previous normal
What structure of the tooth helps prevent flexion and should be preserved?
the marginal ridges
what can make a tooth biomechanically compromised - when prepping (2)
- loss of marginal ridges
- leaving thin cusps
What type of loading are thin cusps under
what may this lead to (2)
tensile loading which causes flexion which may cause cracks to propagate or marginal breakdown
What happens when stress is applied to a thin cusp?
it is under tensile loading, this causes movement and flexion, may propagate a crack or fracture
How can tensile loading of thin cusps be avoided?
by reducing cuspal height and placing an onlay
- CUSPAL REDUCTION AND COVERAGE
what type of loading occurs if cuspal height has been reduced and coverage is placed (onlay)
compressive.
Where is the critical area of the tooth ?
peri cervical area
how may you fix cracked tooth syndrome?
cuspal reduction and coverage.
this results in compressive loading decreasing flexion and protecting the tooth
You can do this on just the one cusp that is effected
What does an inlay replace?
pits and fissures
what does an onlay replace
partial or full cuspal coverage
