ENDO dx and mx of complex cases Flashcards
what causes most iatrogenic errors in endo?
erroneous manipulation and inattention to detail
what is torsional stress?
a tip binds against a canal wall and the coronal part of the file rotates
elastic limit of the metal is exceeded = plastic deformation = fracture
what is cyclic fatigue?
repeated cycles of tension and compression happen during bending
what are the 2 types of rotary file fractures?
torsional stress
cyclic fatigue
list factors contributing to file fracture?
file size and taper
type of alloy
manufacture process of NiTi files
less experienced operator
inadequate access and glide path
anatomy
apical pressure
high speed
repeated use (not in the UK)
what type of files are more vulnerable to torsional stress?
fine, more flex files
what types of canals are more susceptible to fracture files?
canals merging/ dividing
abrupt curvature and radius
s-shaped
isthmuses
fins
what is a favourable outcome for fracture files in a canal?
no PA periodontitis
instrument in apical 1/3rd of root
able to retrieve if PA pathosis present
defect correctable with apical surgeru
what is a questionable outcome of a fractured file in canal?
instrument fractures in coronal or mid-root portion and cannot be retrieved
pt asymptomatic
no PA periodontitis
what is an unfavourable outcome to a fractured file in canal?
pt is symptomatic or a lesion persists requiring extensive procedure to retrieve instrument which may compromise the long-term survival of the tooth
surgical tx is not an option
what do you do if a file fractures in a tooth with a diagnosis of irreversible pulpitis?
remove or bypass
if not possible, the retained fragment should not influence prognosis as the canal is minimally infected with no pre-existing apical pathology
when you are treating an infected canal, what do you do if your fracture files at the end of instrumentation?
embed fragment in filling material if cannot be removed
when you are treating an infected canal, what do you do if your fracture files early in treatment?
the canal beyond the instrument cannot be cleaned and this may be responsible for failure
attempt removal or a by-pass if possible
what instrument is used to attempt bypass?
size 10 file
in what parts of the canal can a fracture file be retrievable?
middle/ coronal third only if straight line access is possible
what factors affect prognosis after of fractured files in canals?
periapical lesion
stage of canal prep
potential weakening of root
perforation/ procedural risks
what is the probability of # file removal?
87%
what factors influence the successful removal of # files?
position of the file in relation to the root curvature
depth within the canal
whether the file is visible using a microscope
what are the risks of removing # instruments?
excessive removal of radicular dentine which may predispose the root to fracture
ledging
perforation
limited application in narrow and curve canals
possibility of extrusion of the #file
the more apically positioned, the higher the risk of iatrogenic damage
what are the 4 techniques of removal of # files?
mechanical
ultrasonics
tube techniques
other
what are mechanical techniques for #file removal
H files
gripping devices; fine haemostat or stieglitz forceps
excavators
how are ultrasonics used to remove # files?
create straight line access to the file
trephine around the file (anti-clockwise) to expose it’s coronal part and loosen it off
describe the tube system for removing # files?
trephine with ultrasonics
position the microtube
engage and remove
what techniques of # file removal are not recommended?
masseran kit
cancellier kit
altered needles
using a glue
if a file fractures in a tooth, what is the prognosis dependant on?
the presence of preoperative periradicular periodontitis
what must the pt be informed about when a file # in canal?
possible consequences
influence on success rate
complications which might occur
further tx
what is a ledge formation?
an iatrogenically created irregularity in the canal, that impedes access of the instruments to the apex
platform = very firm stop
where are ledges common?
outer side of curved canals
what causes ledge formation?
inadequate access cavity
incorrect assessment of canal curvature
failure to pre-bend ss files
using larger, stiffer ss instruments
failure to use instruments in a sequential manner
cutting on inward rather than outward stroke
by-passing a fractured instrument
negotiation of calcified canal
explain the management of ledge formation?
- establish the depth at which the ledge is present
- coronal flare up to F2-F3 working 1-2mm shorter, use small irrigation needle to irrigate between
- PUI with a chelator and NaOCl
- probe with a pre-bent 08 file (coated in chelator paste) - use a gentle picking motion
(if possible to bypass, use short vertical strokes to change shape of ledge, keeping tip of file apical to ledge at all times) - repeat with size 10,15 and 20 until ledge removed
- use pre-bent hand protaper files to complete prep
how do you prebend ss and hand protaper files?
with endobender or tweezers
if you cannot bypass a ledge and the patient has no symptoms, what do you do?
prepare to the ledge
copious irrigation
dress with ns CaOH
obturate using thermoplastic technique
inform pt of gaurded prognosis and review clinical symptoms and bony healing
how do you prevent ledges?
create a reproducible glide path
when working in very narrow/ curved canals, coronal pre-flaring may be necessary (up to S2) before the full working length can be used
copious irrigation using gauge 30 needle + recapitulation
what is a canal blockage?
blockage of the canal in a previously patent canal that prevents access and complete disinfection of the most apical part of the root canal
what may a blocked canal contain?
compacted dentinal mud, most likely infected and/or
- residual pulp tissue, and/or
- remnants of filling material
what causes canal blockages?
apical patency is not confirmed and secured when WL is measured with EAL
during instrumentation, pulpal tissue is packed and solidified in the apical constriction by the use of instruments
instrumentation is not accompanied by copious irrigation and recapitulation
instruments are not cleaned before insertion into canal
when may you recognise a canal is blocked?
the instruments or GP cones are no longer able to reach full WL
characteristic tactile sensation when a very small file is reaching an almost solid but penetrable wall - instead of a solid wall with a ledge
explain management of canal blockage?
- establish a depth at which the blockage is present
- coronal flaring up to S2 working 1-2mm shorter, using small irrigation needle
- PUI with a chelator and NaOCl
- pre-bent 08 file (coated in chelator paste) is introduced into canal and rotated clockwise to detect a weak sticky spot in the mass of debris
- once detected, the file is used passively in a watch winding motion, inandout strokes until reaches WL
- do not remove the file, turn 2-3 times clockwise at full WL
- remove and irrigate
- repeat with size 10 and 15
what is the prognosis of a tooth with a canal blockage?
if it is recognised and corrected, no effect on prognosis
when it cannot be corrected, negative effect on tx outcome, particularly in infected cases
how to prevent canal blockages?
copious irrigation as soon as pulp chamber roof is removed
in narrow and curved canals, coronal pre-flaring before WL is established
small pre-bent k-file (6-10) to establish WL using EAL
recapitulation is essential
what is a canal transportation?
removal of canal wall structure on the outside curve in the apical half of the canal due to the tendency of ss files to restore themselves to their original linear shape during canal prep, may lead to ledge formation and possible perforation
what causes canal transportations?
insufficiently designed access cavities
canal curvature
leaving rotary files in same position
forcing a file into canal
insufficient irrigation
clinical experience
when may endo instruments straighten themselves inside canal?
file pressed against outer side of canal when working in the apical 1/3
file pressed against inner side of canal when working in mid and coronal 1/3
what are the consequences of canal transportation?
damage to apical constriction (debris extrusion)
zip formation (elliptical shape at AC)
elbow formation (narrow point at max curvature)
perforation (on apical 1/3)
strip perforation (along inner side of curvature in mid and coronal third)
ledging
prevention of canal transportation in curved canals?
pre-bent flex files for glide path (08,10 proglider)
never keep rotary file in same position for more than 1s
dont force file down canal
adequate irrigation
