The right lower canine tooth is fractured exposing the pulp

Endodontics: Treating the insides of teeth

Root treatments

Root treatments, including conventional root canal therapy and pulp capping, are intended to help maintain teeth with a damaged and/or infected pulp.

Left: Immature teeth have a large pulp and little dentine
Right: The pulp and its blood supply shrink with continued dentine deposition.
In dogs and cats it takes 1-2 years following eruption for teeth to gain full strength.

Retaining a living pulp

The pulp is responsible for maintaining and thickening the dentine walls that makes up the bulk of a tooth. Bacteria entering the pulp via the blood stream, through the dentine or at a fracture site, or disturbance of the blood supply entering the tooth leads to infection and death (necrosis) of the pulp. In the case of recent traumatic exposure (fractured teeth or pulp exposed during treatment) it is sometimes possible to apply dressings to induce healing. These pulp capping techniques are rarely successful if there is established disease or in old teeth with a poor blood supply.

Damage to an immature tooth is an emergency. Immediate treatment with antibiotics and pain killers permits time to arrange specialist treatment to save the tooth. The specific treatment should be performed as soon as conveniently possible.

Left to right: Treatment of a fractured immature tooth by partial pulpectomy and pulp capping.
The illustration on the right depicts a successful treatment several months later
with deposition of a 'dentine bridge' beneath the dressing,
thickening of the dentine walls of the tooth,
narrowing of the pulp cavity and
completed root formation

The superficial (infected) pulp is removed, a calcium hydroxide based dressing is applied to the remaining pulp, and a surface filling placed to seal the pulp from further exposure to irritants and infection. If there is a good blood supply and the pulp infmammation was superficial the pulp will stay alive and produce a new layer of dentine beneath the dressing. If the pulp does not recover then disease progresses (though often without obvious external signs because detecting discomfort is difficult in animals). A periapical reaction develops and progresses destroying the surounding bone. Unless an acute abscess develops, it usually requires an x-ray to idenmtify the problem.

Treating infected and necrotic pulp

When the pulp is significantly damaged or infected either a full conventional root treatment or extraction will ususlly be necessary. If the tooth has other significant disease such as advanced periodontitis then extraction is indicated. In the case of an immature tooth with pulp nectrosis it is not possible to perform standard root treatments so a modification of the pulp capping technique is used to try and stimulate closure of the end of the root. If this can be acheived, then a modified root filling procedure is possible.

Apexification in an immature tooth with pulp necrosis:
access, cleaning, dressing, elimination of periapical
inflammation with formation of a calcified
barrier and then root filling

Conventional root treatment involves removing all the pulp from a tooth and replacing it with an inert filling material after thorough preparation; cleaning, shaping and disinfection of the pulp cavity. A surface filling or fillings are then placed. The tooth will be dead, but the root attachment will remain healthy providing a suitable home dental care programme is maintained.

Conventional endodontic treatment is a complex and time consuming procedure:
Access is required into the pulp cavity, sometimes in several places.
The residual pulp has to be removed and the pulp cavity
shaped, cleaned and thoroughly disinfected.
The end of the root is then sealed,
the pulp cavity filled, and
the access cavities
sealed

Whilst the vast majority of root treatments are highly successful, it is quite possible for residual infection to flare up after treatment. Leakage of damaged surface fillings is a common cause of this problem so regular follow-up is needed to check the surface fillings and to x-ray the treated tooth to check for periapical disease.

Surgical access for treatment of a root abscess.
The infection has destroyed the bone surounding the root apex of this dog's untreated fractured mandibular canine tooth.

It is advised to watch for signs of pain or discomfort, swelling or discharge around the tooth and its root(s), particularly in the immediate post-treatment period. Should these occur, professional advice should be sought as additional medication and/or re-treatment may be required. In some cases the root filling may need removing and the pulp cavity disinfecting again. Where there are complications preventing adequate cleaning and disinfection of the root canal, surgical access to the root tips may be anecessary for direct placement of fillings to seal them.

Post-treatment radiograph of a conventional root filling in a maxillary canine tooth in a dog.
Some of the sealant used during root filling has leaked through the root tip. This confirms
that at least some of the narrow passages previously occupied by nerves and
blood vessels entering into the root have been filled with sealant

With all endodontic treatments longer term complications are also possible, so radiographic followup is essential. Generally this is initially done at 3-6 months post treatment, and if all is well, 1 year later, then every 1-2 years throughout the animals life.

It is important to remember routine tooth care as it would be a shame to loose an endodontically treated tooth through preventable periodontal disease!

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