Endodontic tips and tricks


Justin Underwood gives some simple tips and tricks to follow if you’re offering endodontic treatment.

Understanding canal anatomy

  • Plan ahead better by taking two pre-operative radiographs (30 degrees apart) to analyse canal morphology. This might confirm the presence of an MB2 or whether any canals divide or re-join
  • Some endodontic hand files have a black mark on the rubber bung. When a clinician pre-curves the apical portion of the file and orientates it with this black marking, it allows the clinician to work out the direction of any apical curvatures or any bifurcations once the file is inside the canal
  • Lower first and second premolars may appear straightforward initially but always be mindful that they can be the most challenging teeth to treat as the canals can bifurcate or trifurcate
  • To investigate if any canals merge together, place a hand file in one canal and a GP cone in the other. When they are withdrawn, have a look to see if the file has made a mark on the GP.

Rubber dam placement

  • If you are struggling to secure a clamp on the tooth, consider a wingless clamp instead as they grip better subgingivally than the winged ones
  • We all know that bacteria is the cause of endodontic disease so why not disinfect the outside of the tooth and the rubber dam with chlorhexine or sodium hypochlorite on a cotton pellet before starting the access cavity
  • If for whatever reason your rubber dam is leaking mid treatment, there is no need to remove anything, instead just place a second dam on top of the first
  • If the practice does not have Oraseal chaulking agent, invert the rubber dam with floss and try using light body silicone impression material or a flowable composite around the tooth to create a better seal than nothing at all.

Checking for cracks

  • Cracks can fail endodontic treatment. If possible, try and replace the existing restoration before accessing the pulp chamber to explore for cracks. Plaque disclosing solution or the ultra-violet curing light are simple devices to help, however high magnification with a light source is essential.

Preventing perforation

  • The pulp floor is at the same level as the CEJ. Estimate your anticipated bur depth penetration by measuring it along the outside of the tooth with the CEJ to reduce the risk of a furcal perforation
  • In molar teeth with extremely receded pulps, aim the access cavity towards the pulp horns. Once you’ve started to instrument the coronal part of the canals, it is easier to get your bearings on the case. If you are unsure if you are in the pulp chamber, the floor of the pulp is dark whereas the roof of the pulp chamber is dentine colour
  • When shaping multi rooted teeth always brush away from the furcation otherwise you can easily strip perforate the inner walls.

Preventing file separation

  • Never place a rotary file where a hand file hasn’t been. Always create a nice channel for your rotary instrument to flow into by developing a smooth glide path. Rotary files commonly separate at the junction where canals merge hence the importance for a glide path of each canal to the apex. Always wipe and inspect the instruments after every use and always check for any un-twisting. Never rush to the apex and if there is resistance met when using a rotary instrument never be tempted to push it apically. Endodontics requires discipline and patience, with continuous irrigation, recapitulation and re-irrigation afterwards
  • When your rotary file has reached the full working length, there is no need to spend more than a second or two at the apex before withdrawing.

Bypassing a ledge

  • If you have created a ledge in a canal you will need to prebend your hand file to bypass it and then use vertical strokes to eventually smooth out the outer wall. Some rotary files can be pre-bent instead making ledge management easier than hand filing alone. If there are any struggles with this, the clinician instead could position the rotary file in the canal (without being connected to the handpiece) and once the ledge has been bypassed manually it could then be connected to the handpiece to be used
  • An even better technique is not to create a ledge. Use balance force technique using hand files with triangular cutting flutes so the file can stay centred within the canal.

Limited mouth opening

  • If the restorative plan is for cuspal coverage, why not reduce the height of the cusps first before starting. This takes the tooth out of occlusion, creates a flatter and more manageable reference point and allows you to use shorter files. Furthermore this would also help if the patient has limited mouth opening
  • Using a smaller mirror (size 0 or size 1) will also help when there is limited access
  • If space is still a problem, research the different contra-angle handpieces. Consider using burs with shorter shanks and rotary instruments with shorter latching handles. Every little helps.

Apex locators

  • The radiographic and anatomical apex can differ up to 3.5mm so always trust your apex locator. For this reason, don’t panic if your obturation appears short on radiographs. Research shows it is better to be too short than too long (where you would destroy the natural apical constriction)
  • Apex locators are only accurate when the beeping sound fires continuously. The countdown measurements on the screen are false readings. Essentially, there is no need to watch your apex locator count down, instead just negotiate your file down the canal and simply listen. When the continuous beeping starts the working length will be 0.5mm from this measurement
  • If you can not get to the apex, there could well be an apical bend. Use orthodontic universal pliers to make a hockey-stick shape hook in the apical 2mm of the file.

Manual dynamic activation (GP pumping)

  • After using 17% EDTA solution to remove the instrumented smear layer, ultimately reopening the dentinal tubules, sodium hypochlorite can then penetrate these and lateral canals by a piston-like hydrodynamic pressure created with a master GP cone (cut 2mm short of the working length) when gently pumped up and down in the canal for one minute, which forces irrigant across the whole root canal system. The clinician must be mindful of a slight sodium hypochlorite extrusion accident if too much force is used.

Drying the canal

  • Instead of using excessive paper points to dry canals, use an empty syringe to draw the solution up and finish with a single paper point.

Master cone radiograph

  • Instead of using the bulkier endodontic radiograph holders for taking master cone radiographs, the regular periapical filmer holders can still be used if you position a cotton roll along the occlusal surface of the tooth, which flattens the bite platform when the clamp is in place. This will prevent the film from tilting unfavourably.

Obturation

  • When cutting a GP cone at office level, a better method than heating an excavator under a Bunsen burner would be to use an ultrasonic scaler tip without water. It melts like butter and is less messy
  • Once there is confirmation of the correct working length of the master cones inside the canals, secure each of them with separate locking tweezers to the designated reference points to easily keep track of their lengths when you place them back in the canals for obturating.

Metal post removal during re-treatments

  • Removing metal posts aren’t as hard as you think but it does require patience. Ten minutes with an ultrasonic scaler tip (alternating with and without water) nearly always breaks the cement lute.

PTFE tape

  • When planning endodontic treatment across two visits, consider using PTFE tape to cover the canal orifices instead of a cotton pellet. This will stop the bur ravelling up every time when you enter the tooth again
  • If you remove the restoration before starting and discover a possible leakage point from a deep margin, pack this area with PTFE tape
  • If you are struggling to get apex locator readings with metal crowns or existing amalgam restorations, you can place some PTFE tape around the file under the rubber bung to prevent metal touching metal.

Justin Underwood

Justin Underwood

Author at Young Dentist

Justin Underwood graduated in 2011 at Cardiff University in addition to gaining an intercalated Bsc in Oral Diseases. During this year his research around dental implants was published and presented in the London’s Queen Elizabeth II Conference Centre at the International Association of Dental Research conference. Justin is currently studying towards his Msc in Endodontics and is a member of the British Endodontics Society and European Endodontology Society.

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