Endodontic failure

Question 1

how does the ESE guidelines define a successful outcome for endodontic treatment?

Answer 1

• absence of pain, swelling and other symptoms
• no sinus tract
• no loss of function
• radiographic evidence of normal PDL

Question 2

when should you review a RCT?

Answer 2

• at least 1 year after and subsequently as required

Question 3

what is an uncertain outcome in endodontics?

Answer 3

if radiographic changes remain the same or has only diminished in size

Question 4

what is the recommended period for review in uncertain outcome?

Answer 4

4 years minimum - assess lesion further until it has resolved

Question 5

what may be indicative if the lesion of uncertain outcome persists after 4 years?

Answer 5

post-treatment disease

Question 6

when does a RCT have an unfavourable outcome?

Answer 6

• tooth is associated with signs and symptoms of infection
• a radiologically visible lesion that has appeared subsequent to treatment or a pre-existing lesion that has increased in size
• a lesion that has remained the same size or has only diminished in size during the 4 year assessment period
• signs of continuing root resorption

Question 7

what is an exception to the persistence of radiological lesions?

Answer 7

• extensive radiologocal lesion may heal but leave a locally visible, irregularly mineralised area
• may be scar tissue formation rather than sign of persisting apical periodontitis
• continue to assess tooth

Question 8

why may RCTs fail?

Answer 8

• presence of a periapical lesion/sinus
• filling underextended (>2mm from apex)
• filling not well condensed with voids
• bad quality coronal resoration - coronal leakage
• missed canals
• perforation
• forcing instruments
• failure to observe sequence of instruments
• not able to establish patency
• severe curvates creating blockages
• poor length control
• mixing of CHX and NaOCl

Question 9

what are biological reasons for failure?

Answer 9

• persistant intra-radicular infection - complex canals, resistant bacteria
• extra-radicular bacteria - actinomycosis, extruded biofilm that cannot be debrided/disinfected
• non-microbial agents - cyst formation (peri-radicular)
• cholestrol crystals
• foreign body reactions - delayed healing
• scar tissue healing

Question 10

what is the law of centrality?

Answer 10

the floor of the pulp chamber is always located in the centre of the tooth at the level of the ACJ

Question 11

what is the law of concentricity?

Answer 11

the walls of the pulp chamber are always concentric to the external surface of the tooth at the level of the ACJ

follows the same shape of the external surface

Question 12

what is the law of the ACJ?

Answer 12

the ACJ is the most consistent, reliable and repeateable landmark for locating the position of the pulp chamber

Question 13

what is the law of symmetry 1?

Answer 13

except for maxillary molars, the orifaces of the canals are equidistant from a line drawn mesio-distally through the pulp-chamber floor

Question 14

what is the law of symmetry 2?

Answer 14

except for maxillary molars, the orifaces of the canals lie on a line perpendicular to a line drawn mesio-distally through the pulp chamber floor

Question 15

what is the law of colour change?

Answer 15

the colour of the pulp-chamber floor is always darker than the walls

Question 16

what is the law of oriface location 1?

Answer 16

the orifaces of the root canals are always located at the junction of the walls and floor

Question 17

what is the law of oriface location 2?

Answer 17

the orifaces of the root canals are located at the angles in the floor-wall junction

Question 18

what is the law of oriface location 3?

Answer 18

the orifaces of the root canals are located at the terminus of the root developmental fusion lines (dentine map)

Question 19

what is the difference between a true and pocket cyst?

Answer 19

• true cyst is separate from the root canal (require surgical intervention)
• pocket cyst is continuous to the root canal/lamina dura (primarily caused by root canal infection - manage cause)

Question 20

what are you looking for when assessing restorative prognosis of a tooth?

Answer 20

• fractures (magnification)
• assess remaining tooth structure
• can you get a good coronal seal? will restoration last?

Question 21

what are the management options for a tooth that needs retreatment?

Answer 21

• KUO
• attempt orthograde retreatment (re-RCT)
• periradicular surgery
• extraction

Question 22

how can you remove GP from a canal?

Answer 22

depends on how condensed
* poorly condensed - use H files to withdraw GP
* well condednsed - may need to create space with C+ files and solvents to dissolve GP

mechanical removal
* Pro-Taper D files
* Reiproc
* Gates-Glidden burs

Question 23

what is the problem with using solvents to dissolve GP?

Answer 23

can leave a smear layer of GP on the surface of the canal, obstructing dentinal tubules
* can soften GP with eucalyptus oil to reduce risk of creating ledge or perforation