Dental extraction remains the primary treatment in many conditions: fractured teeth, periodontally involved teeth, teeth associated with chronic feline gingivostomatitis, etc. Thorough evaluation of lesions requires dental and periodontal clinical examinations as well as dental radiographs. Another parameter of importance is the owner's perception of the condition and willingness to save (or not) the tooth. Treatment options always have to be presented, then discussed with the owner.
1. General Principles and Decisionmaking
Preservation of a fractured tooth depends both on the integrity of the tooth itself and on its supporting apparatus (periodontium):
Evaluation of the extent of the fracture is a key element in deciding whether to extract or save the tooth. The fracture may only affect the crown of the tooth or affect both the crown and the root (crown-root fracture). Extension of the fracture on the root is a complicating factor which may lead to an extraction decision depending on the deep extent of the fracture, the type of tooth (single or multirooted tooth) and the possibility of maintaining a healthy periodontium around the fractured tooth.
The second key element is the exposure of the pulpal tissue which is the nutritive and trophic connective tissue of the tooth. Both the fact that the pulpal tissue has been exposed (complicated fracture) and the delay between pulpal exposure and treatment are important criteria.
Third is the stage of tooth development at the time of the trauma.
The pulp forms a functional unit with the dentin, and this pulp-dentin unit is called the endodontium. It is responsible for the vitality of the entire tooth. At time of eruption, only about two-thirds of the root is formed and the dentinal walls of the tooth are very thin. The root continues to develop in length until the apex is formed (apexogenesis) at the age of 10–16 months, depending on tooth type and breed. Odontoblasts, which are specialized cells within the pulpal tissue, continue secreting secondary dentin throughout life and are responsible for the increase in thickness of the walls of the tooth and the decrease in size of the root canal.
As soon as the pulp is exposed, bacteria enter the pulpal canal and induce a local acute (reversible) pulpitis. Without immediate treatment, the pulpitis extends to the entire pulpal tissue, microabscesses form, and a general (irreversible) pulpitis develops. Pulpal necrosis establishes within a few weeks. Bacterial toxins, enzymes, antigen and byproducts diffuse to the periapical space through the apex and induce an inflammatory reaction (periapical lesion). The chronic periapical lesion (periapical granuloma) is an equilibrium between the irritants within the pulpal canal and the body's defences in the periapical space. It is characterized radiographically by an ovoid periapical lucency centered on the apex. When the body's defences are overwhelmed by the infection (because of aging, increase of bacterial load with time or systemic diseases), the chronic lesion is reactivated into an acute lesion. Pus/exudate can diffuse within the surrounding tissue (cellulitis) or find a way outside (fistula). Radiographically, the periapical osteolysis which formed during the chronic phase is observed.
2. Conservative Treatments of Fractured Teeth
a. Treatment of Vital Immature Teeth1
Complicated tooth fracture (fracture exposing the pulpal tissue) results in pulpal bleeding. Due to the specificity of the pulpal tissue, immediate treatment is necessary in order to avoid complete pulpal infection. No chemically caustic or physically aggressive means of stopping the haemorrhage should be used in order to avoid pulpal necrosis. Injectable antibiotic (amoxicillin) should be given to limit pulpal infection, and dental treatment must be performed as soon as possible. Adequate dental treatment in this case is partial vital pulpectomy with direct pulp capping. The purpose of the procedure is to save vital pulpal tissue. This is particularly useful when dealing with young dogs (usually less than 16 months of age) which still have an immature tooth (thin dentinal wall and more or less open apex). When the pulpal tissue dies, maturation of the tooth stops, leaving a very fragile tooth in place. This treatment can be attempted if the fracture is less than about 5 days old in a young dog. Treating older dogs or older fractures is much less likely to be successful. The teeth are scaled and the oral cavity is rinsed with a chlorhexidine solution. The procedure is performed under aseptic conditions. The coronal part of the pulpal tissue is amputated at a depth of about 8–10 mm with a sterile, round diamond bur or with a small dental excavator if the size of the cavity permits it. Hemostasis is performed on the pulpal stump with sterile cotton pellets moistened with sterile saline.
Once achieved, a biologic material called MTATM is placed over the amputated pulpal tissue. A glass ionomer cavity base is placed over it. The final obturation of the cavity is performed with composite material. Control radiographic examination is scheduled at 4 to 12 months. If the procedure is successful, the radiograph should show thickening of the dentinal wall with decrease of the size of the root canal and closure of the apex if the tooth was immature. No periapical radiolucency should be seen.
b. Treatment of Nonvital Mature Teeth2
The rationale of conventional (orthograde) root canal treatment is to eliminate the infection from the root canal, to perfectly seal (in 3-D) the apical part of the root canal and the coronal access to avoid recolonisation by bacteria in order to induce healing of the periapical lesion. Dental radiographs are taken to assess root canal diameter, apex formation, periapical lesion size and potential dental resorption. To allow proper root canal preparation, root canal cleaning and obturation in the apical part, the coronal access needs to be properly enlarged. The coronal access is opened/enlarged with a bur and then the coronal part of the root canal is enlarged with Gates-Glidden drills, a specific ultrasonic tip or other suitable instrument. The working length is calculated by introducing a thin file to the apical stop and confirming this length radiographically. The root canal is cleaned and enlarged with successive K-files and H-files. Large volume of irrigant (2.5% sodium hypochlorite) is used during root canal preparation. Once all debris has been removed and the root canal is cleaned, it is dried with paper points. Obturation is performed with gutta-percha points and endodontic sealer. After placement of the master gutta-percha point (= the master point matching the biggest file reaching the working length), additional points are placed to provide 3-D obturation. Once the canal is obturated, a superficial reconstitution with composite resin is placed.
c. Treatment of Nonvital Immature Teeth3
Immature teeth with nonvital pulpal tissue (irreversible pulpitis or pulpal necrosis) cannot undergo apexogenesis and further secondary dentinogenesis. These teeth are weak as the dentinal thickness is thin. To be able to perform root canal obturation, the apex must be closed. Apexification is a technique to induce a calcified barrier at the apex to enable proper obturation of the root canal.
References
1. Luotonen N, Kuntsi-Vaattovaara H, Sarkiala-Kessel E, Junnila JJ, Laitinen-Vapaavuori O, Verstraete FJ. Vital pulp therapy in dogs: 190 cases (2001–2011). J Am Vet Med Assoc. 2014;244(4):449–459.
2. Kuntsi-Vaattovaara H, Verstraete FJ, Kass PH. Results of root canal treatment in dogs: 127 cases (1995–2000). J Am Vet Med Assoc. 2002;220(6):775–780.
3. Juriga S, Marretta SM, Niederberger V. Mineral trioxide aggregate (MTA) for apexification of non-vital immature permanent teeth. J Vet Dent. 2007;24(4):274–277 (review).