By Jessica Riehl, DVM, DAVDC
Dentistry and Oral Surgery/Medicine
Tooth fractures are one of the most common dental issues in our veterinary patients, particularly dogs. Many times these injuries are from chewing on inappropriate items, but they can also be a result of trauma. Consequences of tooth fracture can range from relatively simple to complex – involving both the endodontic system and the periodontium.
Owners may present a patient for changes in chewing behavior, decreased appetite, facial swelling, draining tract, visible change in appearance to the tooth, known traumatic event, or a tooth fracture may be an incidental finding during a veterinary exam with no perceived changes at home. Treatment, or at a minimum radiographic evaluation, is always indicated for a fractured tooth. A “watch and wait” approach is never appropriate.
A complicated crown fracture of the right maxillary fourth premolar (108) in a 8 year old Miniature Dachsund. This tooth was treated with root canal therapy.
Choosing the appropriate treatment option first relies on being able to identify damage to the dental hard tissue and recognize pathology.
Uncomplicated crown fractures are fractures that do not result in pulp exposure. These fractures involve loss of the outer enamel as well as the underlying dentin. When enamel loss is present, there is the possibility for endodontic disease or infection within the tooth. Dentin, which comprises the majority of tooth structure, is porous in nature. If you were to examine dentin under an electron microscope, it would appear as a series of tubules. Within these tubules is fluid (hydrostatic pressure/nerve endings), which can lead to dentin sensitivity as a result of the dentin being exposed to the oral cavity. The dentin can also permit bacterial ingress and direct communication to the pulp.
The pulp may become infected or pulpitis from the inciting trauma may be irreversible and lead to a necrotic pulp. Dental radiographs are needed to evaluate the tooth for evidence of endodontic disease (damage to the dental pulp) such as periapical lucency, widening of the periodontal ligament, loss of lamina dura, apical resorption, or a wide pulp canal indicating arrested tooth maturation. If any of these radiographic findings are present, the tooth will require treatment (see discussion of treatment options under complicated crown fractures).
Dental radiographs do have limitations in this diagnostic purpose. Early endodontic disease may not show any radiographic changes as bone changes can take several months to appear. This lag in our ability to diagnose endodontic disease is the reason it is important to recommend follow-up radiographs of these teeth in 6 to 12 months.
In many teeth with uncomplicated fractures, over time tertiary dentin will be laid down. This process occurs when the tooth has a healthy pulp and healthy dentin. The cells that line the pulp chamber, odontoblasts, create and lay down dentin. This reparative dentin will fill the open dentinal tubules (from the deep side) and serve to create a barrier between the external environment and the pulp. Tertiary dentin is laid down quickly by the odontoblasts and is therefore less organized in structure, resulting in its ease to pick up stain and have the typical tan to dark brown appearance.
Dentin is softer in density than enamel and more rough in texture. This can lead to faster wear on the tooth as well as increased plaque and calculus accumulation following tooth fracture. A discussion should always be held with the owners to go over appropriate chew items and the importance of oral home care.
Complicated crown fractures involve the enamel, dentin and have pulp exposure of the tooth. The exposed pulp can range from actively hemorrhaging, pink and bulbous (pulp granuloma), or a pink (vital), brown or black dot (necrotic pulp). These teeth absolutely have endodontic disease. Local oral bacteria are able to enter the pulp chamber and invariably the pulp will suffer from irreversible pulpitis and become non-vital. Radiographs may or may not demonstrate changes associated with endodontic disease depending on a variety of factors (time since tooth fracture, local immunity, etc).
Teeth with pulp exposure or endodontic disease require treatment without question. In adult patients treatment options include either exodontia or root canal therapy. The eight strategic teeth in our veterinary patients include all four canine teeth as well as the carnassial teeth bilaterally (maxillary fourth premolar and mandibular first molar). Due to the anatomical importance of these teeth including their functionality and large root structure, it is desired to preserve these teeth, as well as preserving bone and jaw structure. Root canal therapy permits the teeth to be saved and remain functional for a pet. The purpose of this treatment is to remove the infected pulp (instrumentation), eliminate bacteria from within the pulp chamber/root canal system (sterilization), and fill the interior of the canal with a material that will prevent re-entry of bacteria (obturation). Although a root canal involves many steps and specific endodontic materials, it is a less invasive as well as a less painful treatment. Healing time post-operative is short compared to surgical extraction – which involves healing of the gingival flap and more significantly underlying bone. Patients can resume normal diet and appropriate chew items as short as 24-48 hours after root canal treatment. Evidence of treatment is very minimal with the exception of 2-3 small tooth colored restorations (fillings) where previous pulp exposure was located and additional access sites created to allow instruments all the way to the apex of the tooth.
Root canal treatment has a very high success rate in our veterinary patients with endodontic therapy failure as minimal as 5%.1 Because the tooth will look relatively unremarkable from inside the oral cavity, radiographs are necessary to diagnose the uncommon root canal failure. Recommendation for follow-up radiographs comprise of recheck radiographs 6-12 months following the endodontic procedure and ideally once annually thereafter to coincide with the time of a dental cleaning. This anesthetic event also permits thorough evaluation of the restoration for any defects such as chips or cracks.
In young patients (generally less than 2 years of age), complicated crown fractures have alternate treatment options. Dependent on the time of the fracture, vital pulp therapy should be considered. This is one of the few true “dental emergencies.” Vital pulp therapy or direct pulp capping, removes the coronal-most portion of the pulp, attempting to remove the infected portion and keep the remainder of the pulp vital. This procedure can only be performed on a tooth where the time of the fracture is known and is ideally less than 48 hours from treatment.
Finally, crown-root fractures involve the complexity of endodontic disease with alteration to the periodontium. These fractures extend beneath the gingival margin and can lead to chronic focal periodontitis by permitting food, debris and plaque bacteria to hide in the subgingival defect and promote periodontal attachment loss. Treatment options for these teeth include exodontia and in efforts to save the teeth, extensive procedures such as root canal with crown therapy, apical repositioning, or crown lengthening may be possible.
A few prerequisites exist before considering a tooth a candidate for endodontic therapy with either root canal or vital pulpotomy. The tooth must not have a vertical fracture (extending coronal to apical with extension full thickness into the pulp) and the tooth should be periodontially healthy. The last requirement is that the root itself should be relatively free of inflammatory root resorption to create an optimal “seal” with filling material and prevent future bacterial ingress.
The most suitable treatment option for teeth with endodontic disease will depend on the type of fracture, age of the animal, chronicity or severity of the situation, general health of the patient, ability for owner to provide home dental care and the client’s interest in preserving the tooth.
For more information, please contact Angell’s Dentistry Service at 617-522-7282 or firstname.lastname@example.org.
Kuntsi-Vaattovaara H, Verstraete FJM, Kass PH. Results of root canal treatment in dogs:127 cases (1995–2000) J Am Vet Med Assoc. 2002;220:775–780