posts and core Flashcards
what aspects of clinical assessment are relevant to RCT teeth
amount of tooth tissue left (ferrule)
coronal seal
can tooth be isolated by dam
is tooth TTP (suggests inflamed PDL)
is there swelling or pus
is there periodontal pocketing (single deep pocket suggests vertical root fracture)
is the tooth mobile
what aspects of radiographic assessment are relevant to RCT teeth
quality of the root canal filling (length, voids, perforations)
shape of the canal (narrow, tapering)
unfilled or missed canals
patency (instrument fracture, sclerosis)
bone support
crown:root ratio (ideally 1:1.5)
pathology
what problems can occur after RCT
insufficient amount of tooth structure (internally and externally)
large restoration type (MOD weakens tooth by 66%)
lack of or no ferrule
wide post holes (esp after reRCT)
endo complications (perforation, inadequate root fillings)
what is coronal leakage and why is it important
ingress of oral microorganisms into the root canal system
the most important cause of RCT failure
GP exposed to oral environment >3m requires retx
trim GP to ACJ, cover with RMGIC and then restore
cusp coverage prevents coronal micro leakage and catastrophic failure
what are the restorative options for anterior RCT teeth
intact marginal ridges - composite, veneer
intact marginal ridges + discolouration - bleaching, veneer, crown
destroyed marginal ridges - core build up with crown, post core (direct posts require ferrule for moisture control; cast posts don’t require ferrule but not ideal as cant build up in composite and need to take impression for cast post)
what is a post core
post retains the core which retains the crown
gains intraradicular support for a definitive restoration
what are the guidelines for post placement
avoid in curved canals to avoid perforations
in multi rooted teeth pick the longest straightest root canal
4-5mm GP remaining for apical seal
<1/3 width of the root at the narrowest point
at least 1/2 of the post is in the root supported by alveolar bone
the post is at least the height of the crown it is replacing
ferrule - at least 1.5m height and width of coronal dentine
what is a ferrule
collar of supra gingival dentine that prevents tooth fracture
if crown margin is not placed on solid tooth root fracture is significantly increased
ortho extrusion or crown lengthening can be done to create ferrule - not common
what is the ideal post
parallel sided - more retentive than tapered; but needs more prep
non-threaded - not as retentive as threaded but passive so not placing stress on the remaining tooth
cement retained - not as retentive as threaded posts but acts as a buffer between masticatory forces and the post/tooth
what are the advantages of prefab posts
only 1 visit required
no impression and laboratory visit required
chair side core build up
post and core are different materials
immediate preparation of core
large selection of designs and materials
what are the properties of metal posts
gold, SS, brass, titanium
poor aesthetics
root fracture
corrosion
nickel sensitivity
radiopaque
what are the properties of ceramic posts
alumina, zirconia
high flexural strength
high fracture toughness
favourable aesthetics
difficult retrievability
root fracture
what are the properties of fibre posts
quartz, carbon, glass
flexible
similar properties to dentine
aesthetics
retrievable
bond to dentine with DBAs
radiolucent
what is a core build up
internal part of the tooth is build up with restorative material to replace the lost tooth tissue
the core is prepared - it provides retention and resistance for definitive restorations
what are the properties of composite when used as a core material
common
bonds to tooth
good aesthetics
needs good moisture control
command set so can prep and take master impressions immediately
used with fibre posts
