Endodontics Flashcards
Why is the working length 1-2mm short of the radiographic apex?
The apical foramina is located 0.5-0.7mm away from the anatomical and radiographic apex. The apical constriction is 0.5-0.7mm short of the foramina.
What are the average working lengths of the maxillary teeth?
1 -21 2-20 3-25 4/5-19 6-19 7-18
What are the average working lengths of the mandibular teeth?
1-19 2-19 3-24 4/5-20 6-19 7-18
What are indications for initiating RCT?
Pulp irreversibly damaged, necroting +/or evidence of apical periodontitis
elective devitalisation prior to restorative Tx such as overdenture
What are contra indications of initiating RCT?
non functional/non restorable teeth
insufficient periodonatl support
How does RCT work?
It is the chemical and mechanical debridement of the root canals, removal of the pulp tissue, shaping of the canal, and sealing the disinfected canal by root obturation and a coronal seal
What are the objectives of shaping the canal?
- there should be a continuously tapering shape (effective for irrigation, disinfection and obturation)
- maintain the apex location
- maintain the apex shape
What is the aim of obturation?
to provide a hermetic 3D seal to prevent the ingress of bacteria and tissue fluids which could act as a culture media
incarcerate any microbes remaining the the canal system
prevent reinfection of the root canal system
How do you use k-files?
These are stainless steel files. Used in watch winding action or balanced force
clockwise binds the flutes into the dentine
anticlockwise removes the dentine
What is the difference between NiTi and StSt files?
NiTi is significantly more flexible, exspecially at thicker files.
They can have a range of tapers
can still # from torsional fatigue and torsional stress
What are irrigants used for in RCT and what are the choices?
Flushing, lubricating, bacteriocidal, dissolving organic debris
NaOCl at 5%
EDTA can help with blocked or scleronsed canals
What intercanal medicaments can you use and what is their mechanism of action
nsCaOh paste (hypocal/ultracal) high pH, bacteriocidal
iodine containing paste (vitapex) if organisms are resistant to CaOh
What do you use to obturate and what are the constituents?
gutta percha
has rubber, dyes, plasticisers and radiopaque materials such as barium - used with resin based sealers (AH plus)
How would you restore a tooth after RCT?
seal the canals with flowable composite. fill pulp with GI restore with: crown onlay inlay composite post/core/crown
how would you carry out an RCT?
Have a post operative radiograph to show the full length of the root
provide LA
place non-latex dam with single tooth isolation - seal the dam with oraseal
access the pulp chamber - remove all caries before you enter it
access pulp chamber, remove any pulp with slow speed bur.
use safe ended bur to get straight line access
gates-glidden burs can be used to open the coronal aspect of the canal
Identify canals using dg16 probe - remember the rules
How do you prepare a canal for RCT?
initial negotiation - iso 10 - watch winding. NaOCl.
glide path - increase iso unil size 20
coronal flare - NiTi or gates glidden. recapitulate with iso10 and lots of irrigation
apical negotiation - rest of canal to size 20
working length determination - radiographically and apex locator
apical preparation to working length - minimum iso25
What are some common errors in canal prep
incomplete debridement lateral perforation apical perforation ledge formation apical zipping elbow formation strip perforation
What is the ratio for anti-curvature filing?
outer wall: inner wall
3:1
What are some different obturation techniques?
cold lateral compaction
warm lateral compaction
thermoplasticised injectable GP
coated carriers
If a patient came to you with an acute periapical abscess, how would you proceed?
radiographs, history and sensibility testing.
Establish drainage - under dam and through the pulp. Use a diamond bur to access the pulp
irrigate thoroughly with sodium hypochlorite
seal with GI/ZOE
see patient again in 24 hours to start RCT
If the abscess is fluctuant, anaesthetise around the abscess, incise the abscess at the heaviest point
if the infection is not systemic, no cellulitis then no ABs are required
what determines the success of retrieval of a fractured instrument?
the anatomy of the canal (straight>curved)
the location of the instrument (coronal>apical)
the material of the instrument (StSt>NiTi - NiTi can bind to the dentine)
What are the different methods for retrieving a fractured instrument?
Masseran technique - kits make a channel around the instrument to facilitate removal
mosquito forceps - find forceps if you can see the instrument
can leave in the canal (if at apical region and not symptomatic), fill and monitor
insert a file alongside it
How do you remove old GP for re-rct?
eucalyptus oil dissolves the GP, but this can leave smear layer which is hard to remove
hedstrom files
Why do you need a definitive restoration after RCT?
coronal seal to prevent ingress of bacteria into canal
protect the remaining tooth structure - weakened by cavity prep, dehydration, loss of elasticity of dentine
aesthetics
function
What are the prognositc factors influencing the outcome of RCT?
pre-treatment status of the periapical tissues - no pathology = 95%, smaller lesion better outcome that larger
quality and length of RCF - well compacted, within 2mm of radiographic apex
quality of coronal restorationn
If a patient presents with an acute periapical abscess, how would you treat it?
Drain the abscess - if possible through the tooth under a rubber dam and using a diamond tip but to open the pulp
irrigate the canal with hypochlorite and reseal.
see the patient again in 24 hours.
if abscess is fluctuant, anaesthetise the surrounding tissue and incise at the most fluctuant point.
if the infection is not systemic/cellulitis then no ABs are required
What defines the success of removal of fractured instruments?
root canal anatomy (straight>curved)
where in the canal it has fractured (coronal>apical)
what it is made out of (StSt>NiTi - NiTi can bind dentine)
How would you remove a fractured instrument?
Masseran kit - make a channel around the instrument to remove it
mosquito forceps - fine forceps to be able to hold it
What are some differences between endo on a primary and secondary tooth?
primary - larger pulp chambers, closer to surface. bulbous crowns. ribbon-like canals, splayed roots, resorption of roots, check root formation
Give the aims of peri-radicular surgery
Achieving an apical seal
remove any exisitng infection (excision of apex and curettage)
Why can endodontics fail?
calcification of canals, # instrument, dilaceration or fracture of root, under/over filled, open apex, lateral canals
What are the indications for peri-radicular surgery?
Apical pathology - cyst or infected apex in communication with developing follicle
significant restorative work completed which has intact seal
lateral perforations
RCF extruded beyond apex
give the surgical technique for performing an apicectomy
- achieve anaesthesia
- mark tissue and tooth
- crevicular incision and distal relieving flap
- raise flap - protecting papilla
- use mitchells trimmer to find weak spot in bone over pathology
- remove bone with electric handpiece - amount depends of extent of lesion
- resect apical portion of root (2-4mm) at right angles to long axis and clean
- enucleation of granulation tissue
- prepare apex and seal with RMZOE or MTA - all canals
- reposition flap and suture closed
why do you remove the apex at 90 degrees to long axis of tooth when performing an apicectomy?
to minimise surface area exposed - minimises canals exposed
How do you clean canals during apicectomies?
ultrasonic tips - 3mm prep in canal
What are causes of failure after an apicectomy?
inadequate seal from: extra root too little apex removed - left a fin incorrect shape of seal lateral perf displaced seal lateral canals
or inadequate support: too much apex removed poor perio health excessive occlusal loading apical 1/3 #
vertical root#
poor healing
exposure of apex
When irrigating a canal with NaOCl, patient feels severe pain. What is the likely cause?
extrusion of NaOCl through the apex can be from too much force pushing needle too far through open apex can lead to tissue necrosis
How would you act if you extruded NaOCl through the apex of a patient?
- stop
- reassure pt, tell them what the likely cause is
- dry canal and temporise
- remove dam
- call Maxfacs for referral
- cold pack in 15 min intervals for 24 hours
- pain relief
- document all information, including measures taken to avoid this happening
- recall next day
How do you avoid NaOCl contacting tissues?
- bib
- eye protection
- dam
- dam sealer
- EWL from Rx
- bend in needle 2mm short of EWL
- finger pressure on plunger
- blunt ended needle with side venting
- aspiration with yanker
- needle doesnt engage canal walls
- pass needle behind pt head
What are symptoms of NaOCl extrusion through apex?
severe pain bleeding from canal progressive swelling in area immediate ecchymosis and haematoma of skin trismus ana/para or hyperaesthesia
What is the technique for cold lateral compaction?
- choose GP point which is the size of the apical constriction
- check fits with tug back and no concertinaing
- cover in AH plus resin adhesive
- place in canal to WL using locking tweezers
- use finger spreader (A) in lateral direction
- use accessory cones until no more fit
- remove exccess with hot firing instrument and condense with cold plugger
- seal with RMGI
What are different problems that can occur when preparing a canal with StSt instruments
zipping apical transportation perforation ledge formation blockage fracture of instrument
What criteria must be fulfilled before the root canal system of a tooth can be obturated?
symptomless
canal must be dried
full biomechanical cleaning
give 3 types of sealers used in root canal obturation
ZOE
resin based
CaOH
calcium silicate
