Indications for Crowns and Core Success Flashcards
what tooth fractures are considered restorable/unrestorable?
restorable - craze lines, fractured cusp, cracked tooth above ACJ
unrestorable if crack extends past crown onto root surface
what are telescopic/double crown dentures?
removeable dentures that fit precisely over teeth prepared with an inner crown - the inner crowns aid denture retention
what condition must abutment tooth be in for it to be prepped to retain a bridge?
abutment tooth must be heavily restored to justify crown prep
it would not be acceptable to prepare an unrestored/minimall restored tooth for a crown as a bridge retainer
what is the biological width? on average how far above is it to the crest of the bone?
the distance between the junctional epithelium and connective tissue attachment to the root surface
3-4mm above the crest of the bone
what will happen if crown margin encroaches the biological width? how will this look on a person?
gingiva will reject crown - gingiva will become inflammed and bone loss around tooth
why is crown prep not indicated for everything?
crown prep produced heat and may cause pulp damage
may cause pulpal irritation and necrosis
may risk ingress of bacteria to pulp
crown placement places tooth one step closer to XLA
what are contraindications for a crown?
poor diet, poor OH, smoking, parafunction
active caries, periodontal disease, periradicular disease or tooth wear
inadequate crown height
inadequate access for tooth prep and impression taking
when a more minimally invasive option is available
give 3 tx options if crown fails
new crown
post retained crown
XLA
what must pulpal state be prior to crown prep?
tooth must be asymptomatic - if pulp vital and infected then RCT prior to crown placement
what is the ideal excursive movement for crown placement?
canine guidance
when is a core build up required?
if tooth to be crowned is heavily restored/broken down
list 4 ways to aid core retention
undercut preparation
dentine pins
adhesives
elective endo to place posts
list some disadvantages of self threading pins
induces stress
can cause dentinal crazing
often doesn’t penetrate full pin hole depth
can reduce fracture resistance of core
may perforate periodontium
what can be used to aid retention of amalgam core in posterior teeth?
Nayaar core - amalgam extends down coronal part of canals
why do we not place cores in posterior teeth?
the posts weaken roots
roots in posterior teeth often narrow and curved - risks perforation, weakned tooth amd root fracture
when only are cores required in anterior teeth?
posts only required when insuffieicent tooth structure and heavily broken down tooth - marginal ridges not intact
what 3 ways can GP be removed from canals prior to post placement?
heat, chemicals or mechanically using gates gliddens (non cutting tip bur)
how much GP should be left apically? what must length and diameter of post be? what ferrule is required?
4mm
post should be longer than crown
post should not be >1/3rd the diameter of the root
1.5-2mm ferrule required
what is the ferrule?
band of natural tooth tissue between crown and core
explain the difference between active and passive posts
active posts = engage the walls of the canal - inc retention but more stress on root
passive posts = retained strictly by luting cement
what type of post is more retentive? texture and parallel/tapered
texture = threaded>serated>smooth
angle = parallel>tapered
how does diameter and length of post affect retention?
diameter has little effect on retention
post length has effect on retention - longer posts more retentive
explain difference between direct and custom made posts
direct posts = cylindrical and may ot match shape of canal
custom made posts = indirect, impression taken of post space, post allows natural shape of canal to be replicated
fibre reinforced posts - what are they cemented with? what crowns are they used for?
adhesive resin cements
used for all ceramic bonded crowns
