The endodontic tissues (dentin and pulp) make up the structure of the tooth and form the tooth’s crown and root. These are separate from the periodontal tissues that surround the tooth root. While a large portion of endodontic disease is due to trauma, several types of problems can affect the tooth’s crown and root. Each requires careful diagnosis and specific treatment.
Types of endodontic problems
In mild cases, the pulp survives. In other cases, the tooth becomes non-vital and infection occurs. Careful diagnosis of a pet’s endodontic problem ensures that the correct treatment is prescribed.
Tooth contusions: Occasionally, tooth trauma occurs, causing pulp bleeding without breaking the tooth; this is called tooth contusion. A tooth with contusion will initially appear pink due to hemmorhage in the pulp canal. Later , the discoloration becomes brown or gray as the blood becomes degraded. Pulpitis and pulp necrosis (non-vital tooth) are the most common outcomes of tooth contusions.
Tooth abrasion and attrition: When dentinal tubules or pulp are exposed due to abnormal enamel wear such as chewing on abrasive toys (like tennis balls), hard materials such as fencing or cages, or intense self-grooming (itchy skin), it is called tooth abrasion. When the enamel is mildly and gradually worn away, the dentinal tubules become exposed, but the pulp may survive. When the abrasion is aggressive and occurs rapidly, pulpitis, pulp necrosis and apical abscesses may develop.
Tooth attrition refers to the tooth wear caused by an opposite tooth. This occurs with malocclusions when teeth from the mandible (lower jaw) come into abnormal contact with teeth from the maxilla (upper jaw).
Pulpitis: Pulpitis is painful inflammation of the pulp, which occurs when the tooth is damaged by fracture, abnormal wear, or other trauma. If pulpitis becomes chronic, root canal treatment or extraction is required to alleviate the intractable pain.
Pulp necrosis: This occurs as a consequence of severely inflamed or infected pulp (pulpitis). Once pulp necrosis has occurred, the tooth is considered to be non-vital. The most common outcome of non-vital teeth is progression to tooth root abscesses.
Apical root abscess: Apical root abscesses are painful and result from infection travelling down the root canal or periodontal space to the soft tissues at the apex (tip) of the root.
Tooth fracture: Tooth fractures can be caused by a major trauma, such as being hit by a car, but can also occur simply from aggressive chewing on hard materials such as bones. Tooth fractures can result in various degrees of structural damage. Tooth fractures can be uncomplicated and limited to the enamel and dentin, or they may be complicated, exposing the pulp canal. Tooth fractures may be limited to the crown or also involve the root.
UNCOMPLICATED TOOTH FRACTURE: In uncomplicated tooth fractures, exposing the dentinal tubules results in an inflammatory reaction in the pulp (pulpitis). These teeth are painful. Uncomplicated tooth fractures can be superficial (away from the pulp) or deep (close to the pulp). In superficial uncomplicated crown fractures, the pulp may heal, but deep uncomplicated crown fractures are at high risk for chronic pulpitis, pulp necrosis and apical abscess.
COMPLICATED TOOTH FRACTURE: In a complicated tooth fracture, the pulp is exposed. Soon after exposure, the tooth develops pulpitis, which will progress to pulp necrosis, and an apical root abscess.
Caries disease: Caries disease is manifested by lesions that affect the tooth structure; it is a specific type of endodontic disease. Caries lesions are caused by destruction of the tooth’s enamel and dentin by acid-producing oral bacteria.
In health, acid-producing oral bacteria attach to the tooth surfaces and are maintained at a normal, manageable, level. Certain conditions such as frequent treats containing high concentrations of starch and sugar and cause these bacteria to proliferate and produce acids, which causes dissolution of the hard surfaces of the tooth. The resulting tooth lesions are painful, as they cause exposure of the dentinal tubules and pulpitis. If they progress far enough, they can also cause exposure of the pulp, pulp necrosis, and tooth root abscess.
Tooth resorptive lesions: Root replacement resorption, for example, is mild, limited, and can be a part of the aging process. In this case, the loss of periodontal ligament allows the alveolar bone (the socket) to fuse with the root surface. At the opposite end of the spectrum are the feline tooth resorptive lesions, where tooth structure is progressively destroyed, leaving chronically painful defects on tooth surfaces.
Unlike caries disease (“dental cavities”) that are caused by acid-producing bacteria, tooth resorptive lesions are caused by a type of cells, called odontoclasts, which are specialized in removing hard tissue (in this case, the dentin). When tooth resorption results in exposure of dentinal tubules or pulp, the tooth becomes very painful.
While some types of tooth resorptive lesions can be associated with the aging process, other types can result from trauma, chronic inflammation, mechanical compression, oral tumors, or systemic disease.
Feline tooth resorptive lesions are common, affecting up to 67% of cats. These lesions are also found in remains of ancient cats and wild felines. A similar process occurs, but with a low frequency, in in other species, including dogs and humans. Unfortunately these painful lesions are idiopathic, meaning that the reasons the odontoclasts become destructive are unknown.
Diagnosis of endodontic disease
Many endodontic problems can be identified in cooperative animals during a non-anesthetized oral examination. However, is necessary to determine the degree of root and pulp involvement and the health of the associated periodontal tissue. This requires oral diagnostics, including dental radiographs, probing, and exploring, which need to be performed under anesthesia.
Despite the fact that endodontic disease can be very painful, animals will conceal their oral pain to the best of their ability. A change in eating habits or behavior may prompt an oral examination, but this is far from reliable. Most painful endodontic lesions are found on routine examination, and not because a problem was suspected based on behavior. Because some endodontic problems, like tooth resorptive lesions are associated with the tooth root and pulp, most are not readily seen.
The presence of feline tooth resorptive lesions may be suspected based on a characteristic appearance of the gingiva. When focal areas of inflamed and enlarged gingiva are noted, further evaluation under anesthesia is warranted. However, this gingival appearance is not always seen with feline tooth resorptive lesions.
Accurate interpretation of dental radiographs is essential for classifying tooth resorptive lesions.
Resorptive lesions are classified based on the presence or absence of concurrent processes such as inflammation, cysts, and tumors; their location on the tooth (cervical, internal, or external); stage of progression (stages 1-5, with stage four having sub-stages A, B, and C); and type of periodontal involvement (I-III). While this detailed classification can appear cumbersome for those less familiar, it provides important information for planning treatment.
Treatment of endodontic disease
Treatment of endodontic disease should be based on complete oral diagnostics including dental radiographs, periodontal probing and exploring the root canal where indicated. Oral diagnostics provide the information needed to determine treatment options. Whenever feasible, saving the tooth is a priority.
Vital pulp therapy (pulp capping): The immature teeth of young adult animals have very thin walls. Vital pulp therapy refers to treating a complicated tooth fracture in a young adult animal by removing the superficial portion of the inflamed pulp, applying medication to the pulp, sealing the fractured surface of the tooth, and allowing the pulp to heal so that the tooth maturation process can continue. Vital pulp therapy is most effective within 24 to 48 hours after trauma, before pulpitis extends farther down the root. Vital pulp therapy can also be performed when the pulp is exposed during the treatment of crown reduction in certain malocclusions as an alternative to orthodontic movement.
Bonded sealants: This treatment addresses the tooth sensitivity caused by the exposed dentinal tubules and allows the pulp to heal. Bonded sealants cannot be used in contact with, or be close to, the soft tissues of the pulp and gingiva. If an uncomplicated crown fracture is deep, near the pulp, placing a bonded sealant may aggravate the pulpitis and can even cause chronic pulpitis that can progress to pulp necrosis and apical abscess. For those cases vital pulp therapy or root canal treatment is the recommended treatment.
Root canal therapy: Root canal therapy involves removing the diseased or non-vital pulp, disinfecting and sealing the dentinal tubules from the root canal, filling the canal with a biocompatible material and placing a restoration that closes the fractured surface. Root canal therapy is intended to preserve the structural and functional integrity of a tooth, alleviate pain, and prevent or treat the formation of apical root abscesses. Teeth with chronic pulpitis, necrotic pulp and apical abscesses can benefit from this treatment.
Teeth that have undergone root canal therapy may benefit from the additional protection and strength provided by a custom-prepared metal crown.
Tooth extraction: Tooth extraction is considered a last resort and is generally reserved for cases where salvaging the tooth is not an option or not in the animal’s best interest. In animals the tooth roots are very large, so in cases where the roots are surrounded by healthy bone, extraction requires oral surgery, and especially for larger teeth, this includes surgical removal of a significant amount of the alveolar bone that surrounds the tooth.