endodontic failure Flashcards
preop causes of endo failure and what are some precautions
1) error in dx
might be because of
- false + or - from diagnostic tests
- source of infection is extra radicular and hence removal of bacteria in canal is ineffective
- failure to idnetify teeth with poor prognosis (eg VRF)
precautions
- use >1 diagnostic test
- proper exam
- take radiographs from multiple angles
2) poor case selection
intra op causes of endo failure and how to avoid
general:
break of aseptic technique bc communication of sterile canal with unsterile oral envt will introduce contaminants into the canal
precautions: RDI, prep tooth before RCT (must be caries free)
access:
1) gouge
can be due to:
- lack of attn to degree of axial inclination of the tooth
- under prep leads to limited visibility and loss of orientation
possible ways to avoid:
- access without rubber dam to determine orientation
- use safe ended bur after penetration into pulp chamber
2) missed canals
- can be because of lack of knowledge of root canal anatomy and under prep
C&S:
1) under instrumentation
- inadequate debridement harbours residual bacteria in canal
- might be because blockage then end up short of WL
- precaution: ensure straight line access, pproper use of AL and frequent recapitulation to ensure correct WL
2) over instrumentation
- violate apical foramen, loss of apical constriction an extrusion of debri
3) procedural errors like ledges, zipping, apical transportation, lateral & apical perf
- these will cause difficulty in obturation also
4) instrument separation
- torsional strain: tip binds to canal but motor continues to rotate
- cyclical fatigue: due to overuse, compressive & tensile stresses
to avoid:
- check files for signs of overuse before usage
- copious use or irrigants as lubrication
5) extrusion of irrigant
- forceful use and wedging of needle in canal
- leads to hypochlorite accident (sudden pain, rapid diffuse swelling)
to avoid:
- use perforated needle
- irrigation with controlled pressure
- needle placement in canal should be loose and short of WL
OBTURATON:
1) underfill
- due to under instrumentation, insufficient condensation pressure or canal blockage
- >2mm short or over extension leads to poorer healing (Sjogren et al 1990)
to avoid:
- ensure patency of canal and correct WL
- proper adaptation of master cone with positive stop & tug back
2) overfill
- caused by over instrumentation or excessive condensation pressure
- leads to lack of apical seal
- extrusion of materials not good because GP is mildly toxic initially and sealers can cause foreign body reaction and impair healing g
3) moisture contamination
- impt bc sealers may be slightly soluble so moisture contamination of GP or dentine can lead to dissolution of sealer, increase spaces for bacteria to recolonise
4) might cause VRF if there are excessive lateral forces in overprepared canal and hence wedging action
management options when endo has failed
1) non surgical retreatment
- Toronto study: 81% cases healed
- more favourable long term outcomes than surgery
- very high success rate if cause of failure is correctly identified and corrected
2) surgical retreatment: high success rate
3) extraction with replacement:
- single tooth implant
- FPD
4) extraction without replacmenet
- SDA
5) intentional replantation
- careful exo with minimal damage to PDL then perform root end surgery without desiccating and damaging PDL in <10 min
- reinsert tooth into socket and splint for 5-7 days
- indicated when there is no other tx to maintain tooth
6) auto transplantation
- transfer tooth from one socket to another in same px
- good case selection will lead to good prognosis
- both this and intentional replantation can fail via ankylosis and resorption
some evidence for retreatment
Friedman 2008
- when there is absence of PARL: complete healing in 93-95% of teeth
- where there is presence of PARL: complete healing in 73-86% of teeth, asymptomatic function in 95%
Holm Pedersen et al 2007: presence of perforations lowers success, the 5 year survival is 42% of teeth
indications for surgical treatment
- foreign body rxn
- true cysts
- extra radicular infection in refractory cases
what are the indications and contra indications of non surgical retreatment
indications
- when there is still intra canal infection
- inadequate tx requiring revision
contraindications
- restorative: when there is already poor restorative prognosis
- periodontal: poor C:R ratio, excessive mobility
- endodontic
1) thin canal walls: risk of lateral perf
2) post/separated instruments not amenable to removal
3) severe apical curvature, beyond line of sight causing risk of perf
4) apical perf: not possible to re establish apical control of GP
5) root fracture
what is the classification for root perf
Fuss & Trope 1996
1) coronal
- coronal to crestal bone & epithelial attachment
2) crestal
- at level of crestal bone & epithelial attachment
3) apical
- apical to crestal bone & epithelial attachmenta
factors influencing prognosis of root perforation
1) time between occurrence & tx
- less time in between then less chance of infection
- better periradicular envt around perforation and hence better healing
- longer duration means poorer prognosis
2) size of perforation
- the smaller the better because easier to seal and less tissue destruction & inflammation and hence healing more predictable
3) location of perf
- coronal: access to perf is attainable and adequate sealing is possible without periodontal involvement hence good prognosis
- crestal: susceptible to epithelial migration to perf site and hence rapid pocket formation thus poor prognosis
- apical: adequate endodontic tx and accessible main canal so good prognosis
what are the 6 causes of persistent apical periodontitis (briefly, then elaborate later)
Nair 2006
split into 2 main categories - microbial and non microbial causes
MICROBIAL
1) intra radicular infection
2) extra radicular infection
NON MICROBIAL
3) cystic apical periodontitis (true cysts)
4) cholesterol crystals
5) foreign bodies
6) scar tissue healing
what type of microbial flora in intra radicular infection
- predom gram + cocci, rods, filaments
- E faecalis, Actinomyces, Streptococci, C albicans, F nucleatum
Enterococcus faecalis:
- Gram + facultative anaerobe
- more common in persistent than primary infections (treated>untreated canals)
got resistance because
- can survive in high alkaline envt (up to pH 11.5)
- resistant to most intracanal medicament (CaoH)
- survive without synergistic support
- survive in nutrient deprived conditions
- forms biofilm, invade dentinal tubules and bind to dentine
how does extra radicular infection work
1) bacteria exists on external root tip surface with biofilm structure
- grow in clumps (Actinomyces, Propionibacterium)
- cluster formation in lesion tissue -> too large for phagocytosis
2) can also occur in periapical actinomycosis
- rare chronic, granulomatous infection
- caused by gram + bacteria -> perpetuate inflammation at periapex even after RCT
- presents as persistent & recurrent draining fistula in PA region
3) extra radicular microbes
- microorganisms invade extra radicular tissues during expanding & exacerbating phases of disease process
4) extra radicular viruses
- PA inflammatory process activates latent virus
why should we avoid carrying out C&S halfway
because the microbial flora are able to adapt and survive in changed environmental conditions and hnce must eradicate microorganisms in initial tx session
pocket cyst vs true cyst
pocket cyst is epithelium lined cavity open to root canals, has a communication w root canal whereas true cyst is where the cavities are completely enclosed in epithelial lining and theres no communication with root canal
healing of pocket cyst after NSRCT is likely but for true cyst, is not likely esp if big
how do cholestrol crystal cause apical periodontitis
accumulation of cholesterol crystals in apical cyst irritates PA tissues & prevents healing
how do foreign bodies cause apical periodontitist are the different responses to different kind of GP extrusion
GP extrusion in general is associated with delayed healing of periapex
large pieces: well encapsulated in collagenous capsules
fine particles: induce FB reaction: intense, localised tissue response
