Veterinary Dental Referral Service

Cedric Tutt BVSc (hons), MMedVet (Med) (Bov), MRCVS

Endodontics - root canal therapy

• This is an alternative to extraction! The pulp (mainly blood vessels and nerves) is removed from the root canal and replaced by an appropriate filling material before a final restoration (dental filling) is placed in the tooth. Usually the crown of the tooth is not built up to its original height because the restorative material is weaker than the tooth substance and may be broken off again.

Fractured left lower canine

Restoration after root canal treatment

• Although most teeth in the dog can be root filled, the canines, carnassials and incisors are the teeth most commonly treated in this manner.
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• Animals that have short lower jaws (commonly called over shot or "parrot mouth"), the lower canines bite into the palate inside the upper canines. This not only causes pain and trauma to the soft tissues, but also causes destruction of the hard palate eventually resulting in a comunication between the mouth and the nasal passages (known as an oro-nasal fisula). The lower canines are shortened or extracted. Shortening of the teeth results in exposure of the pulp and they will thus require root canal therapy.
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Palatal Trauma due to lower canines

• Teeth may become discoloured pink or grey as a result of damage to the pulp. These teeth will require root canal therapy as well because they can become infected leading to root abscess formation.

Pulpitis of left lower canine

When the permanent teeth first erupt into the mouth they do not have roots. However after a number of months the roots develop and in most dogs the roots will have formed completely by one year of age. If a young dog fractures a tooth and exposes the pulp it should be seen as a matter of urgency. When these cases are seen within a couple of hours, the exposed part of the pulp can be removed (called a "partial pulpectomy") and after an appropriate dressing has been placed on the pulp the tooth can be restored. This will enable the root to continue developing and root canal therapy can be performed at a later date. In young patients that have had to have their canines shortened because of trauma to the palate, partial pulppectomy followed by root canal therapy at a later stage will be performed.

Fractured deciduous canine

Endodontic treatment

Endodontic treatment, commonly known as root canal therapy, is performed in a number of situations. The most common reason would be as an alternative to extraction of an otherwise healthy tooth that has been fractured. Other reasons include teeth that have severe periodontal disease involving the pulp and teeth that are mal-positioned and causing trauma either to other teeth or soft tissues in the mouth.

When teeth are fractured and the pulp is exposed, initially it becomes inflamed but can progress to infection and pulp death. This leads to damage of the supporting bone around the tip of the root and can culminate in a tooth root abscess often seen as a swelling of the pet’s face.

Fractured teeth can cause abscesses that drain into the mouth	Fractured teeth can cause facial abscesses

Fractured Carnassial	Irrepairable Fractured Canine

Firstly a dental radiograph is taken of the affected and adjacent teeth. This helps the veterinary dentist decide whether the tooth is salvageable or not. For instance if the crown of the tooth is broken and the dental radiograph reveals that the root is also broken just below the gum as well, there is no alternative to extraction. Teeth that break at an angle with the fracture line extending below the gum level may also need to be extracted. There are exceptions to this rule that will involve extensive surgery including crown elongation procedures. Immature permanent teeth will not have developed a root tip and this can be confirmed on the radiograph as well. In these teeth it will be necessary to perform treatment in stages.

If the radiograph reveals that the tooth and its attachments are sound, endodontic treatment may be commenced. Some veterinary dentists use the fracture site to enter the pulp cavity while others will create a second access site (mainly in canine teeth). A very thin endodontic file (0.1 mm in diameter) is inserted into the pulp cavity and the radiograph of the tooth is repeated to confirm that the tip of the file is at the tip of the root. The file is then used to clean and shape the walls of the pulp cavity. The pulp itself may need to be removed using an instrument called a “barbed broach” that has fish hook like barbs extending from its shaft. During shaping and cleaning of the pulp cavity files of incremental size (generally up to about 0.9 – 1.4 mm in diameter) are used. After each file is used the debris is flushed from the canal using an appropriate solution. Once the canal has been cleaned, shaped and flushed it is finally rinsed using sterile water before being dried using finely rolled “paper points”. The canal is now ready to be filled with an appropriate filling material. This is followed by a base filling and finally the access site is restored using an appropriate dental restorative material. The materials used in endodontics are those that your own dentist may use should you require endodontic treatment yourself. Radiographs are taken each step of the procedure to ensure that the treatment is going according to plan. About 3-12 (usually 6) months later, radiographs of the affected tooth or teeth are repeated to evaluate the repair around the root and the integrity of the filling.

Endodontic Files