Restoration of the Endodontically Tx Tooth Flashcards
Before restoring a tooth what must we assess?
If tooth is restorable - can we isolate tooth with rubber dam?
how much tooth structure remains? ferrule
coronal seal?
any sign of infection? TTP?
Mobility?
Probe for pocketing - perio disease, root fracture
What is the tx aims when restoring an endo tx tooth?
To retain tooth as functional unit in arch
To maintain the coronal seal of root canal system
to protect and preserve tooth structure
What is a post made of?
dk?
What do we assess in radiograph of an endodontically tx tooth?
Quality of obturation - length (1-2 of radiographic apex, well condensed? coronal GP at level of ACJ?)
Any unfilled or missed root canals (MB2 in 6s)
Shape of canal - if we are going to do a post
Patency of canal - fractured instruments?
Sclerosis of canals?
Crown root ratio
Pathology
Bone levels
What is sclerosis of the canals?
This is where pulp become obliterated by deposition of peritubular dentine (either due to edge or defence against trauma)
What do we want to known about prev endo tx?
How it was carried out - rubber dam used? sodium hypochlorite used? if not then re-RCT as not done under gold standards
Why do we need cusp coverage on posterior teeth?
To prevent coronal micro leakage and ingress of bacteria into tooth
to prevent catastrophic fracture - if tooth splits through furcation and buccal wall comes off then unrestorable
What is coronal micro leakage?
This is where there is ingress of Microorganisms into the root canal space and is a cause of root canal failure
If RCT tooth has GP exposed what is the rule?
If >3 months then tooth needs re-RCT due to risk of ingress of MOs into root canal space leading to infection
Where do we trim GP back to after obdurating?
ACJ - so we can see canal orifice openings
What do we do after obdurating with GP and trimming GP back to ACJ?
We then seal over with vitrebond/RMGIC over the pulp floor and root canal opening
Why do we ensure liner of GI over pulp isn’t too thick?
so we can utilise retainer of pulp chamber for retention and restoration
Why is coronal seal so important?
the technical quality of the coronal sal if more important than technical quality of RCT
How do we assess the quality of RCT?
Condensed - well or poorly?
Voids presence?
GP at level of ACJ
1-2mm of radiographic apex
voids around master and accessory points?
What is a ferrule?
Collar of dentine that encircles tooth (360 degrees) and prevents tooth fracture
Why does a ferrule prevent tooth fracture?
As it means the coronal restoration will be on tooth structure (dentine) rather than filling material (core)
What increases the risk of root fracture in restored teeth?
If there is no ferrule and restoration lies on restorative material rather than dentine so decreased longevity of crown
Does RCT make teeth more brittle?
No
Does RCT make tooth more likely to fracture?
No if minimal loss of dentine
Does endo make tooth become weaker?
Actual endodontic tx itself doesn’t alter dentine harness but access cavity weakness tooth
How can we restore a tooth post endo tx?
Direct restoration (composite, GIC)
Indirect restoration (crown, post crown, veneer)
What is a marginal ridge?
Enamel that forms M+D of anterior and posterior tooth
In anterior teeth if marginal ridge is intact what do we do for post endo restoration?
Direct restoration (we dont want to do crown/post crown which would affect integrity of marginal ridge)
If anterior teeth have loss or compromised marginal ridge what do we do for post endo restoration?
Indirect restration - crown/post Crown
What is average survival rate for well done crown?
8-10 years
Does a post and core strengthen a tooth?
No - just increases longevity of tooth in the mouth
What is the purpose of a post and core?
Provides intra-radicular support for a definitive restoration and is used when not enough tooth structure present so we can attach/cement a crown
What does a post do?
It retains the core
What does a core do?
Provides retention for the crown
What does prep for a post do?
Weakens the tooth - as to create space for post we need to remove tooth structure
Where is the post placed?
In the root canal system to retain the core
What is the core?
This is what the prosthesis is cemented onto (crown)
Do we use posts in incisors and canines
No if we have enough ferrule present
if extensive loss of coronal tooth tissue = need post as single root canal is not adequate at retaining a core
When do we avoid posts?
Lower incisors - due to thin, tapering, narrow mesiodistal roots
If we have multi-rooted tooth where do we place post?
Widest canal and in straight canals to avoid risk of perforation
What are the 4 criteria for post placement?
4-5mm Apical GP remaining (so apex is sealed and majority of lateral canals occur in apical 5mm)
width <1/3rd
post length: 1:1 crown root ratio or 2?3rd root length
2mm ferrule circumferentially
What does a ferrule allow us to do?
Build up a core so that when we place a coronal restoration the crown margins will be on dentine (reduces chance of root fracture)
Where should crown margins finish?
On tooth structure or else inc likelihood of fracture
If here is no ferrule what options do we have?
ortho extrusion
surgical crown lengthening
What are the 3 features of an ideal post?
PARALLEL SIDED
NON THREADED PASSIVE POST
CEMENT RETAINED
What is a non threaded post?
This is where post is passive and doesn’t cause transmission of force inside root reducing risk of root fracture
What are the types of posts?
Pre-formed
Custom Made (direct or indirect)
What material can posts be made of?
Cast metal
Steel
Zirconia
Carbon
Glass fibre
What are the shapes of posts?
Parallel sided
Tapered (less retentive than parallel)
Smooth
Serrated
Threaded (screw) - most retentive but most likely to fracture root
What are pre-fabricated posts?
These are posts that are ready made in diff shapes - can be smooth or threaded
they only require 1 visit - no impression required and can do chair side core build up
What are custom made posts?
These are posts that are made in the lab
we create post hole, take impression, cover it in adhesive, place silicone in imp tray, pour up in ab and lab make post and core
requires two visits - imps and then fit
Difference between tapered and parallel posts?
Tapered posts follow the root and ensure stress is concentrated coronally but they are retained by cement
parallel place stress along length of root and concentrate stress apically
Difference between threaded and non threaded posts?
Threaded - inc retention due to self threading into dentine but inc risk of fracture as it cuts into canal
Non-threaded - retained by cement which helps to distribute forces evenly but less retention
What types of metal can be used for a post?
Cast gold, stainless steel, brass
poor aesthetiucs
risk of shine through
risk of root fracture
corrosion risk
radiopaque
What are benefits of ceramic posts?
high flexural strength and fracture toughness (post wont fracture but tooth may)
good aesthetics - tooth coloured, no shine through issue
if they break difficult to retrieve and risk of root fracture
What are benefits of fibre posts such as carbon and glass fibre?
flexible, similar properties to dentine, aesthetic, retrievable, bonds to dentine with DBA but hard to etch into post hole
What cement can be used for posts?
Adhesive resin
GIC
RMGIC
What cement provides highest retention for posts?
Adhesive resin - however bonding can be impaired by endo material remnants in canal
Describe GI as a cement for posts
Weak chemical bond to dentine
easier to retrieve
fluoride release
several days to reach max strength
What is a core build up?
This is where we buildup internal part of tooth with restorative material to replace lost tooth tissue and then we can put a crown on
What does core do?
Provides retention and resistance for permeant restorations
What can we use as a core?
Composite
Amalgam nagar core
What is a composite core?
this is where we use composite to build up core and it bonds to tooth structure with DBA and has good aesthetics and is tooth coloured
What is a nyaar core?
2-3mm coronal GP removed
amalgam packed into coronal aspect of canal - locks in undercuts and used to retain core
takes 24 hours to set - cant be prepd straight away
poor aesthetics
doesn’t bond to tooth
uses pulp space and orifice to retain amalgam
What are some risks of post crowns?
Perforations
Core fracture
Root fractyure
Post fracture
Describe post perforation
This is where post perforates the tooth (common in curved, narrow canals)
If post perforates the tooth what may we see?
Lateral radiolucency
What is management of post perforation?
Xla
Peri-radigular surgery
How does core fracture happen?
This is where theres not enough tooth structure or lack of ferrule and core fractures off
Why can post fracture?
If too short or narrow
How do we remove posts?
Ultrasonic
Masseran KIt
Mosquito forceps
Eggler
Anthogyr
What are some problems during removal of post?
Fracture of post
fracture of root
unable to remove post
tooth becomes unrestiroable
What is deemed as endodontic failure?
presence of clinical signs and symptoms of infection
enlargement of existing peri-radicular lesion
new peri-radicular lesion
Persistnce of peri-radicular lesion of tooth RCT 4 years previously
What can we do once we identify failed RCT?
Monitor
Orthograde Re-RCT
Peri-radicular surgery
Extract
Before re-RCT a tooth what must we consider?
Can we improve?
cost?
risks ans benefits
What are indications for orthograde Re-RCT?
Intra- radicular infection (RC short of apex, loss of coronal system)
if pt needs new complex restoration and we are unsure of standard of prev RCT
loss of corneal seal - exposed GP >3 months
What are the principles of re-RCT?
Remove restoration
Assess tooth - caries removal, assess for fractures
removal all of root filling
assess anatomy
refine/modify prep
obturate
How do we remove GP?
Eucalyptus oil
Ultrasonic removal
Hand files
Reciproc R25
