CSAR 3 pt 1 Flashcards
for a crown prep, what 3 things do you do?
- occlusal reduction
- axial reduction
- marginal configuration
what does reduction and modification rely on?
they rely on the tooth being of the ideal form
if not can wax up or use composite
What does retention mean?
What does resistance mean?
Retention - resisting removal along the path of insertion
Resistance - prevents dislodgement by forces directed apically or obliquely
what is the ideal prep height??
3-4mm
What is the total occlusal convergence ?
ideally between 6-12 degrees
max: 20 degrees
surgical crown lengthening what is it
- expose a greater height of clinical crown for aesthetic reasons
- needs careful and holistic planning
What are the negatives of surgical crown lengthening?
- limited root in the bone - can cause periodontal problems
- the further up you go, the more exposed and the more narrow the tooth is
do you want undercuts during crown prep?
no
look at it from above and see it
what is marginal configuration ?
the junction between the prep and prosthesis
what are the types of margins?
- chamfer
- knife edge
- vertical
- shoulder
what are the positives of a metal crown? (4)
- more durable
- stronger in thinner sections so prep is less destructive
- kinder to opposing teeth
- reliable marginal seal
why are Ceramic and PFM preps larger?
as they are too brittle to be placed thin layers so preps need to account for this
if someone is getting a crown and have periodontal disease, what is needed?
- stabilisation
- but prep will need to be larger to accommodate PFM crown
Where do you want to avoid placing the crown margin?
connective tissue attachment
what can placement of the crown margins on the connective tissue attachment cause?
persistant inflammation
