Endodontics

Question 1

Why is the working length 1-2mm short of the radiographic apex?

Answer 1

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.

Question 2

What are the average working lengths of the maxillary teeth?

Answer 2

1 -21
2-20
3-25
4/5-19
6-19
7-18

Question 3

What are the average working lengths of the mandibular teeth?

Answer 3

1-19
2-19
3-24
4/5-20
6-19
7-18

Question 4

What are indications for initiating RCT?

Answer 4

Pulp irreversibly damaged, necroting +/or evidence of apical periodontitis
elective devitalisation prior to restorative Tx such as overdenture

Question 5

What are contra indications of initiating RCT?

Answer 5

non functional/non restorable teeth

insufficient periodonatl support

Question 6

How does RCT work?

Answer 6

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

Question 7

What are the objectives of shaping the canal?

Answer 7

1. there should be a continuously tapering shape (effective for irrigation, disinfection and obturation)
2. maintain the apex location
3. maintain the apex shape

Question 8

What is the aim of obturation?

Answer 8

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

Question 9

How do you use k-files?

Answer 9

These are stainless steel files. Used in watch winding action or balanced force
clockwise binds the flutes into the dentine
anticlockwise removes the dentine

Question 10

What is the difference between NiTi and StSt files?

Answer 10

NiTi is significantly more flexible, exspecially at thicker files.
They can have a range of tapers
can still # from torsional fatigue and torsional stress

Question 11

What are irrigants used for in RCT and what are the choices?

Answer 11

Flushing, lubricating, bacteriocidal, dissolving organic debris
NaOCl at 5%
EDTA can help with blocked or scleronsed canals

Question 12

What intercanal medicaments can you use and what is their mechanism of action

Answer 12

nsCaOh paste (hypocal/ultracal)
high pH, bacteriocidal

iodine containing paste (vitapex) if organisms are resistant to CaOh

Question 13

What do you use to obturate and what are the constituents?

Answer 13

gutta percha

has rubber, dyes, plasticisers and radiopaque materials such as barium - used with resin based sealers (AH plus)

Question 14

How would you restore a tooth after RCT?

Answer 14

seal the canals with flowable composite. 
fill pulp with GI
restore with:
crown
onlay
inlay
composite
post/core/crown

Question 15

how would you carry out an RCT?

Answer 15

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

Question 16

How do you prepare a canal for RCT?

Answer 16

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

Question 17

What are some common errors in canal prep

Answer 17

incomplete debridement
lateral perforation
apical perforation
ledge formation
apical zipping
elbow formation
strip perforation

Question 18

What is the ratio for anti-curvature filing?

Answer 18

outer wall: inner wall

3:1

Question 19

What are some different obturation techniques?

Answer 19

cold lateral compaction
warm lateral compaction
thermoplasticised injectable GP
coated carriers

Question 20

If a patient came to you with an acute periapical abscess, how would you proceed?

Answer 20

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

Question 21

what determines the success of retrieval of a fractured instrument?

Answer 21

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)

Question 22

What are the different methods for retrieving a fractured instrument?

Answer 22

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

Question 23

How do you remove old GP for re-rct?

Answer 23

eucalyptus oil dissolves the GP, but this can leave smear layer which is hard to remove
hedstrom files

Question 24

Why do you need a definitive restoration after RCT?

Answer 24

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

Question 25

What are the prognositc factors influencing the outcome of RCT?

Answer 25

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

Question 26

If a patient presents with an acute periapical abscess, how would you treat it?

Answer 26

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

Question 27

What defines the success of removal of fractured instruments?

Answer 27

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)

Question 28

How would you remove a fractured instrument?

Answer 28

Masseran kit - make a channel around the instrument to remove it mosquito forceps - fine forceps to be able to hold it

Question 29

What are some differences between endo on a primary and secondary tooth?

Answer 29

primary - larger pulp chambers, closer to surface. bulbous crowns. ribbon-like canals, splayed roots, resorption of roots, check root formation

Question 30

Give the aims of peri-radicular surgery

Answer 30

Achieving an apical seal | remove any exisitng infection (excision of apex and curettage)

Question 31

Why can endodontics fail?

Answer 31

calcification of canals, # instrument, dilaceration or fracture of root, under/over filled, open apex, lateral canals

Question 32

What are the indications for peri-radicular surgery?

Answer 32

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

Question 33

give the surgical technique for performing an apicectomy

Answer 33

1. achieve anaesthesia 2. mark tissue and tooth 3. crevicular incision and distal relieving flap 4. raise flap - protecting papilla 5. use mitchells trimmer to find weak spot in bone over pathology 6. remove bone with electric handpiece - amount depends of extent of lesion 7. resect apical portion of root (2-4mm) at right angles to long axis and clean 8. enucleation of granulation tissue 9. prepare apex and seal with RMZOE or MTA - all canals 10. reposition flap and suture closed

Question 34

why do you remove the apex at 90 degrees to long axis of tooth when performing an apicectomy?

Answer 34

to minimise surface area exposed - minimises canals exposed

Question 35

How do you clean canals during apicectomies?

Answer 35

ultrasonic tips - 3mm prep in canal

Question 36

What are causes of failure after an apicectomy?

Answer 36

``` 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

Question 37

When irrigating a canal with NaOCl, patient feels severe pain. What is the likely cause?

Answer 37

``` extrusion of NaOCl through the apex can be from too much force pushing needle too far through open apex can lead to tissue necrosis ```

Question 38

How would you act if you extruded NaOCl through the apex of a patient?

Answer 38

- 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

Question 39

How do you avoid NaOCl contacting tissues?

Answer 39

- 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

Question 40

What are symptoms of NaOCl extrusion through apex?

Answer 40

``` severe pain bleeding from canal progressive swelling in area immediate ecchymosis and haematoma of skin trismus ana/para or hyperaesthesia ```

Question 41

What is the technique for cold lateral compaction?

Answer 41

- 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

Question 42

What are different problems that can occur when preparing a canal with StSt instruments

Answer 42

``` zipping apical transportation perforation ledge formation blockage fracture of instrument ```

Question 43

What criteria must be fulfilled before the root canal system of a tooth can be obturated?

Answer 43

symptomless canal must be dried full biomechanical cleaning

Question 44

give 3 types of sealers used in root canal obturation

Answer 44

ZOE resin based CaOH calcium silicate