Introduction and overview to Endodontics

The aims of root canal treatment are to:1. Remove and eliminate the bacterial load in the root canal system.2. Dissolve and debride inflamed and infected pulp tissue from the pulp space.3. Prevent future invasion of microorganisms.

NOTE: Preparation of the root canal is both mechanical and chemical –so called “chemo-mechanical debridement

What shapes are the access cavities?

- Anteriors: Triangular- Maxillary

o Premolars: Ovoido Molars: Rhomboidal/Blunted Triangle

- Mandibularo Premolars: Circularo Molars: Trapezius/Rhomboid

NOTE: Posterior teeth - the access cavity walls will open towards the mesial to allow better visualisation and instrumentation.

Purpose of a correctly shaped and positioned access

- Easier location of canals- Allows straight-line access for instrumentation where files are able to track against the

access walls to enter canals.- Allows appropriate access to visualise the pulp chamber for debridement.- Preserve as much sound tooth structure as possible, reducing the long-term risk of root

fracture.- Allows temporary seal in-between appointments.

Key Concepts

Preparing the root canal with the crown-down + step-back technique

- Pre-operative LCPA to estimate working length, number of canals and anatomy of roots.

- Coronal preparation (crown-down)o Remove the roof of the pulp chamber to

for initial access with round diamond or fissure bur and copiously irrigated with sodium hypochorite.

o Locate root canals with pre-curved size 10 file. Working length LCPA can be taken now after using the apex locator.

o Improve visualisation and remove interferences to allow straight-line access once canals are confirmed. Diamond taper burs for walls and gooseneck rosehead burs for canal orifices.

o Coronal flaring with Gates Glidden 4, 3, 2. Each size down, going 2-3mm deeper than previous.

- Apical preparation o Using a large file, e.g. 60 with some EDTA lubricant, work your way down the canal,

going down in size until you reach ~4mm short of WL with a size 30-35. (crown-down technique finished)

o Step-back technique – at working length, prepare apex with files 8, 10, 15, 20 (25) with balanced force technique. NOTE: Ensure patency + irrigation performed between in each file through out this process. Go up in file size, each file 1mm short of previous file.

o Join the apical third with the middle third with this technique. o Master GP can now be placed and LCPA taken.

What is patency filing?

Prevent blockage of canals with infected debris, particularly at the apices. Small files (ISO 6, 8 or 10) should be used in-between each debriding instrument after sodium hypochlorite irrigation. The file should pass beyond the working length with ease. 8-10 files are used to check patency with the occasional use of 6 is the 8 or 10 suspects a blocked canal. The 6 could slip between the root walls and the debris, allowing it to be dislodged and removed with another irrigation. Why pre-flare and prepare the coronal 2/3 of the canal?

- The bulk of infected material is found in the pulp chamber and coronal third of the root canal system. Removing this material early reduces the potential for bacteria in debris to block or even extrude at the apex.

- Early flaring of the coronal 2/3 removes dentine constrictions that can cause instrumentation to be short of WL.

- More rapid penetration of irrigant into the apical third.

Apex anatomy

- Apical foramina: the hole where the nerves exit at the apex of the root. Usually slightly lateral to the centre of the tooth.

- Apical constriction: the narrowest area of the canal system where we aim to fill our GP up to. ~0.5mm short of the apex.

- Radiographic apex: the end of the root as we see on a radiograph.

Avoid zipping of the apex

- This is the iatrogenic straightening of a curved root canal, particularly a problem at a laterally exiting foramen.

- It would overprepare the outer wall of the curve and underprepare the inner wall.

- Pre-curving the canal would prevent this as well as reducing the chance of ledging.

Chemical components of RCT

Sodium Hypochlorite – potent disinfectantant, low surface tension and can dissolve organic tissue at higher concentrations. 0.5% solution effectively kills bacteria. >1% will have dissolving properties.

EDTA (ethylene diaminetetraacet ate) – calcium binder (chelator) thus removes smear layer. Useful to finish canals/aid the preparation of sclerosed canals, as well as unblocks canals. Removes unsetting CaOH that is placed in-between appointments.

Root Canal Sealer (Grossmans Sealer) – fills irregularities in the root canal preparation, improving the seal of the filling. Lateral canals and isthmuses blocked. Zinc oxide + eugenol base, also antibacterial. Extrusion would cause irritation though.

Calcium Hydroxide – the use of non-setting CaOH inbetween appointments is antibacterial due to its high pH. When in place for at least 7 days, it has been shown to effectively kill pathogens found within the canal system and resists recolinisation.

Ledermix – High effective anti-inflammatory cortisone derivative + antibiotic (a tetracycline). Normally used after extirpation, rapidly relieving acute pulpal symptoms. Will automatically kill the nerve if used as a direct pulp cap and will need RCT.

Others…Chlorhexidine (do not use in conjunction with NaOCl!), Iodine Potassium Iodide.

Balanced force technique