endo third year. - restoration of endo treated tooth Flashcards
what do you clinically assess in a RCT tooth?
coronal seal remaining tooth structure - ferrule restorable? - can you isolate with dam swelling sinus TTP buccal sulcus TTP mobility increased pocketing - PDD and root fracture
what do you radiographically assess in an RCT tooth?
root filling - length, quality, voids
unfilled/missed RCs
shape of canal
patency - fractured instruments, posts, sclerosis
bone support
crown to root ratio (1:1.5)
pathology - PA radiolucency, resorption, perforations
which is the most commonly missed RC?
2MB canal 16/26
if the root filling is inadequate what should you do?
re-treat before pros
problems with restoring a tooth after RCT
amount of remaining tooth structure internally and externally
lack/no ferrule
wide post holes
endo complications - fractured instruments. perforations, short/long root fillings
are RCT teeth more brittle?
no
what is coronal leakage?
ingress of oral microorganisms into the RC system
what is the most important cause of RCT failure?
coronal microleakage
generally if root filled teeth are unrestored for how long should they be re-RCT?
3m or longer
how do you create an ideal coronal seal?
trim the GP to ACJ and place RMGI over pulp floor and RC openings (lateral canals)
not too thick - allow remainder of pulp chamber for retention and restoration
Rx options for anterior teeth - intact marginal ridges
composite
veneer
Rx options for anterior teeth - intact marginal ridges and discoloured crown
bleaching or veneer
crown
Rx options for anterior teeth - marginal ridges destroyed
core build up with crown
post crown
function of a post-core
gain intraradicular support for a definitive restoration
function of core
provides retention for crown
function of post
retains core
do posts strengthen or weaken teeth?
weaken - removing more tooth structure
6 guidelines for post placement
try to avoid 1 - tooth type 2 - root filling length 3 - post width 4 - sufficient alveolar bone support 5 - crown length/post length ratio 6 - ferrule
guidelines for post placement - tooth type
avoid L incisors- thin/tapering MD roots, 30% have 2 RCs
avoid in curved canals - avoid perforations
premolars - small pulp chambers and tapering roots, place in widest RC
guidelines for post placement - root filling length
4-5mm GP apically
guidelines for post placement - post width
no more than 1/3 of root width at narrowest point and 1mm of remaining circumferential coronal dentine
does diameter of post increase retention?
no
guidelines for post placement - sufficient alveolar bone support
at least half of the post length into the root
guidelines for post placement - post length/crown length ratio
min 1:1
does length of post increase retention?
yes
guidelines for post placement - ferrule
at least 1.5mm height and width of remaining coronal dentine from the gingival margin
what is a ferrule?
1.5-2mm collar of dentine extending supragingivally 360 degrees round circumference
advantage of a ferrule
reduces fracture risk of tooth, and also root when crown placed
what does the post length below the crown need to at least equal?
crown length
ideal post features
parallel sided
non-threaded (passive)
cement-retained
ideal post features - parallel sided
avoids wedging
more retentive than tapered
ideal post features - non-threaded
smooth surface incorporates less stress to remaining tooth than threaded
ideal post features - cement retained
less retentive than threaded posts but cement acts as a buffer between masticatory forces and post/tooth
3 classifications of posts
manufacture - prefabricated or custom made
material - cast metal, steel, zirconia, carbon/glass fibre
shape - parallel sided or tapered
advantage of prefabricated posts
only one visit required - no impressions/lab visit
disadvantage of prefabricated posts
posts and core are different materials
advantage of custom made posts
unified post and core - preferred for non-vital teeth as avoids material interfaces
disadvantage of custom made posts
2 visits required - temporisation between risks contamination of RC
what do cast custom posts tend to be made from?
type 4 heat hardened gold
what materials can posts be made from?
metal
ceramics
fibre
metal posts materials
cast gold, SS, brass, titanium
disadvantages of metal posts
poor aesthetics
root fracture
corrosion
nickel sensitivity
advantages of metal posts
radiopaque
ceramic post materials
alumina, zirconia
advantages of ceramic posts
high flexural strength and fracture toughness
good aesthetics
disadvantages of ceramic posts
difficult retrievability
root fracture common
fibre post materials
glass, quartz, carbon
advantages of fibre posts
flexible similar properties to dentine aesthetic retrievable bond to dentine with DBAs
are fibre posts radiolucent or radiopaque?
radiolucent
post shapes
tapered
parallel
describe a core build up
internal part of tooth is built up with restorative material to replace the lost tooth tissue
core is prepared - provides retention and resistance for permanent restorations
do all cores need a post?
no
core materials
composite
amalgam
GI
composite as a core material
most commonly used good aesthetics bonds to tooth structure technique sensitive - moisture control required used with fibre posts
amalgam as a core material
tend to avoid as retention is required
poor aesthetics
core can’t be prepared straight away - need 24hrs to set
avoid pinned amalgams
GI as a core material
not really used as it absorbs water and core expands in size
Nayyar core
root treatment is removed from the RCs
amalgam is packed into the RCs and tooth built up - provides retention for the amalgam
cannot be prepared for 24hrs until amalgam sets
problems with posts
perforation
core fracture - v common
root fracture
post fracture
post perforation management
repair - internal or external (PR surgery)
extraction
post removal
US Masseran Kit (trephan) Moskito forceps (screw retained) Eggler device sliding hammer anthogyr (safe relax)
why do most posts fail?
restorative reasons>PD reasons>endo reasons
what material is usually used for a direct post?
fibre
for a direct fibre post what is required?
ferrule
bonding a direct fibre post
resin cement under dam
which type of post can be done (not ideal) without a ferrule?
cast post
why should you avoid posts where possible?
it is a last resort to save the tooth
stages in cast post prep (11)
assessment design of new restoration provisional restoration GP removal post space prep and anti-rotation features provisional construction impression lab prescription provisional placement try in fit
why is it so important to be confident in the quality of RCT before placing a post?
posts are difficult to dismantle and there is a risk of root fracture
what is the risk with tapered posts?
act as wedges - root fracture
how much GP should remain apically with a post?
3-5mm
where should crown margins be placed and why?
on the ferrule - solid tooth tissue
gives resistance to rotational forces and micro leakage, reduces fracture risk
core design
6 degree taper
length required - to allow 2mm clearance incisally for MCC
what options do you have for a provisional restoration?
provisional post core crown e.g. tempbond
immediate denture
dressing e.g. ZOE
Essix retainer with some teeth on
what size GG do you need to get to when removing GP In straight part of canal for a post?
min size 3
how do you ensure you leave 3-5 mm of GP apically?
use WL and rubber stopper on GG
what can you use to ensure a GP plug remains?
loupes
microscope
PA
how can you soften GP?
heat or solvent
why is it sensible to leave once obturated for 24 hours before post prep?
to allow resin sealer to set
- ideally post prep at same time as obturation but risk disrupting that
ParaPost XP
indirect casting technique post system different drill sizes brushing motion Ti provisional post imp post parapost drill
what should you do before post space prep?
impression
ParaPost XP - preparing provisional post
cut it from apical end 2-3mm short of incisal edge
ParaPost XP - post space prep
heat source remove GP
GGs and irrigate
Parapost drill. irrigate
pro temp into putty matrix - parapost retained in pro temp
ParaPost XP - definitive master impression
putty wash technique
- light body
- putty impression over top
- post retained in imp (imp post)
antirotation groove
some cut this into prep to prevent rotational displacement
in bulkiest area of root, usually lingual
lab prescription for cast post
please construct cast post and core
para post (colour)
core 6 degree taper
please leave 2mm space in occlusion for crown
enclosed registration/opposing impression/(shade) for crown
cast post try in
check post space for any remaining temp bond or debris - US to clean out irrigate CHX 0.2% - dam? dry PP ensure fits around prep - protect airway do you have enough occlusal clearance?
cast post fit
don’t fill post space with cement - may prevent it seating, hard to remove it again
firm apical pressure
get rid of excess
can ask lab for provisional acrylic crown
make sure no excess around or gingival bleeding when taking crown imp/fitting MCC
post removal problems
unable to remove root fracture (immediate/delayed) render tooth unrestorable post space too wide you break post
posts in molars
-s outweigh +s
if absolutely have to
in most cases sufficient natural retention for a core
if no coronal tissue - posts may be inserted for short distance into largest straightest root canal
at least 1mm ferrule of definitive coronal restoration required unless all-porcelain Rx
which roots do posts usually involve in molars and why?
distal L molars
palatal U molars
they provide a large and usually straighter canal for post-insertion
cuspal protection
prevent catastrophic fracture
prevent microbial ingress
maintain coronal seal
posts in premolars
only if roots are adequately bulky, long and straight
only one canal should be used
