Tooth problems.

Dr. Farcas performs a root canal treatment on a feline patient. He uses thin files to remove the pulp from the pulp chamber.

The tooth is made of dentin and pulp. Together, they comprise the endodontic tissues, which are distinct from the surrounding periodontal tissues. Most endodontic disease is caused by trauma to the tooth, but other problems also affect the endodontic tissues. Careful diagnosis and specific treatment are required to alleviate the pain and infection (or potential for it to develop) associated with endodontic disease, and ideally to preserve the tooth structure.

Types of endodontic problems

The pulp is sensitive and can be affected by many types of problems.

When only mildly affected, the pulp can survive, but with more severe damage, the pulp becomes inflamed, and may lose its vitality and become infected. Thorough evaluation of an endodontic problem allows for the most appropriate treatment to be recommended.

Tooth contusions

Animal Dental Clinic: contusion
Tooth contusion. The tooth appears pink due to hemorrhage in the pulp chamber and dentinal tubules.

Discoloration means the tooth is in trouble.

When a tooth is traumatized such that the pulp bleeds without breaking the tooth, it is called tooth contusion. A contused tooth will first appear pink due to the fresh blood trapped in the dentinal tubules. With time, the discoloration becomes brown or gray as the blood components break down. In severe tooth contusions, chronic pulpitis and pulp necrosis are the most likely outcomes. Ideally, a contused tooth should be treated to alleviate pain and to save the tooth.

Tooth abrasion and attrition

Animal Dental Clinic: abrasion
Tooth abrasion. Excessive wear on this tooth has caused exposure of dentinal tubules, as well as the pulp chamber.

Teeth that look to be worn-down can be painful.

When pets aggressively chew on abrasive or hard materials, teeth dentinal tubules or, in severe cases, pulp becomes exposed; this is called tooth abrasion. In cases where the tooth’s hard protective enamel wears away over time, dentin is exposed, but pulp might survive. However, when the wear is rapid or aggressive, pulpitis, pulp necrosis and apical abscesses are likely outcomes.

Attrition refers specifically to wear caused by an opposite tooth, which happens in patients with malocclusion; where mandibular teeth abnormally contact maxillary teeth.


Tooth contusion. Trauma has damaged the blood vessels of the pulp, causing the pulp chamber and dentinal tubules to fill with blood. Pink: enamel with pink appearance due to blood visible beneath enamel surface; Red: hemorrhage within pulp chamber and dentinal tubules

Pets don’t complain about their toothache.

When a tooth suffers significant damage from trauma, fracture, or abnormal wear- pulpitis, or inflammation of the pulp, is a common result. When pulpitis is chronic, definitive treatment such as root canal therapy or tooth extraction is recommemded to relieve pain and stop the progression of infectious processes.

Pulp necrosis

Tooth contusion with pulp necrosis: When trauma is severe, pulpitis progresses to pulp necrosis (decay). As blood degrades, the pink color of the contused tooth turns to gray. Light gray: enamel, Dark gray: degraded blood from hemorrhage in the pulp chamber and dentinal tubules.

Pulp necrosis is loss of tooth vitality.

When pulpitis is severe or progresses to infection, the blood vessels, nerves, and pulp cells are destroyed, and the tooth is called non-vital. These teeth commonly progress to develop apical root abscesses.

Apical root abscess

Progression of pulpitis to pulp necrosis. In this illustration, necrosis extends from the pulp chamber into the periodontal tissues at the root apex, causing a periapical abscess.

Progression of tooth infection into the surrounding tissues.

When infection in the pulp spreads beyond the root tip (apex), an abscess develops. Tooth abscesses are known to be very painful and can have negative effects on adjacent structures, both inside and outside the oral cavity.

Tooth fractures

Animal Dental Clinic: tooth-fracture
Complicated crown fracture in a dog. This is a very common site for tooth fractures in dogs. In this case, the crown fracture has exposed the blood vessels and nerves of the pulp.

Under certain conditions, any tooth can be broken.

Tooth fractures can be caused by major trauma, but can also result from chewing on materials that are harder than the tooth, such as bones. Tooth fractures are classified based on the severity of damage to the tooth. In so-called uncomplicated tooth fractures, the dentinal tubules are exposed, while complicated tooth fractures, exposure of the pulp canal takes place. Further classification indicates whether the crown, root, or both are involved.

Uncomplicated tooth fracture: With these fractures, exposed dentinal tubules cause a pulp reaction, and in severe cases, significant pulp inflammation (pulpitis), which is very painful. Uncomplicated fractures may be superficial (farther away from the pulp) or deep (closer to the pulp). Superficial uncomplicated fractures may allow the pulp to heal, but deep ones pose a high risk for chronic pulpitis, pulp necrosis and apical abscess.

Complicated tooth fracture: Complicated tooth fractures by definition expose the pulp, which results in rapid development of painful pulpitis. Without treatment, chronic pulpitis progresses to pulp necrosis, and results in apical root abscess.

Caries disease

Animal Dental Clinic: endoidontics-types-caries-lesions
Here, acid-producing baceria have caused destruction of the enamel and dentin of this tooth, exposing the dentinal tubules and pulp chamber.

A common human problem that also affects dogs.

In caries disease, teeth develop lesions that damage the physical structure of the tooth. These lesions are the result of acid-producing oral bacteria destroying enamel and dentin.

Normally, these bacteria are in contact with all oral surfaces and the body’s defenses keep their numbers low enough that they do not cause harm. When these defenses are disrupted or overwhelmed by certain unbalancing conditions, the bacteria proliferate and produce acid that dissolves the hard tissues of the tooth. Caries lesions expose dentinal tubules and cause pulpitis, so they are exceptionally painful. When allowed to progress, pulp necrosis and tooth root abscess can result.

Tooth resorption

Animal Dental Clinic: endodontic-lesion-resorption-radiograph
Radiograph showing feline resorptive lesions that have caused destruction of the crowns and roots of all three teeth pictured.

Tooth resorption can be mild and non-painful, or it may be destructive and extremely painful.

Tooth resorption is a process where the normal tissues of the tooth are replaced with another type of tissue. There are multiple contributing factors- some known, and some unknown, and several different categories, or types, that have a variety of outcomes. For example, one less problematic form is root replacement resorption, which is generally mild, limited, and may be a normal part of aging. At the opposite end of the spectrum are feline tooth resorptive lesions, which cause progressive destruction of the tooth structure; this leaves severely painful defects on tooth surfaces. Other types of resorption can result from trauma, chronic inflammation, mechanical compression, oral tumors, or systemic disease. All of these are distinctly different from caries disease, which is caused by acid-producing oral bacteria.

Diagnosis of endodontic disease

This radiograph shows a tooth that was fractured long before this radiograph was taken. As dogs and cats mature, their pulp chamber becomes narrower. When pulp necrosis occurs, this process stops. This radiograph shows that this tooth is non-vital because its pulp chamber is much wider than the teeth on either side of it. Also note the decrease in bone density at the root apices (tips), indicating periapical abscess, or extension of the pulp decay into the periodontal tissue.
This radiograph shows a tooth that was fractured long before this radiograph was taken. As dogs and cats mature, their pulp chamber becomes narrower. When pulp necrosis occurs, this process stops. This radiograph shows that this tooth is non-vital because its pulp chamber is much wider than the teeth on either side of it. Also note the decrease in bone density at the root apices (tips), indicating periapical abscess, or extension of the pulp decay into the periodontal tissue.

Finding the problem is only the first step.

While an endodontic problem is often seen on an awake oral examination, this doesn’t provide enough information to determine how best to proceed. To understand the degree of root and pulp involvement and assess the local periodontal tissue, further oral diagnostics are needed.

Even though endodontic disease is usually painful, pets do their absolute best not to show it. Pet owners may notice subtle changes in eating habits or behavior, but this is far from reliable. The majority of painful endodontic lesions are diagnosed because a veterinarian or pet owner looked for them as a part of routine valuation, and not because the pet owner suspected a problem. Other endodontic problems occur below the gingiva, so are not seen until oral diagnostics are performed.

While this doesn’t occur reliably, a characteristic inflammatory appearance of the gingiva may increase a veterinarian’s suspicion of feline tooth resorptive lesions. Certainly, when focal areas of gingivitis are seen in cats, further oral diagnostics are indicated.

Classification of tooth resorptive lesions, which is important for planning treatment, also requires expert interpretation of dental radiographs.

Treatment of endodontic disease

When possible, saving a tooth with appropriate treatment can preserve and improve oral function.

Endodontic treatment should always be guided by oral diagnostics, which provide the information needed to determine what treatment options are viable and provide the best outcome long-term. Whenever feasible, options to save a damaged tooth are presented, so that oral function is not compromised by loss of the tooth.

Bonded sealants

Animal Dental Clinic: endo-treatment-bonded-sealant
Bonded sealants are cured (hardened) by exposure to ultraviolet (UV) light.

Bonded dentinal sealants cover exposed dentinal tubules.

In selected cases where pulp is not exposed, placement of a bonded dentinal sealant can eliminate the sensitivity caused by exposed dentinal tubules; it can also allow healing of inflamed pulp.

Vital pulp therapy (pulp capping)

13. Vital Pulp Therapy

Vital pulp therapy: Gray: composite restoration; Green: pulp medication

Vital pulp therapy can allow a fractured immature tooth to continue normal development.

When young adult animals fracture their thin-walled, immature adult teeth, vital pulp therapy may be a good option to save the tooth. In specific situations, this treatment can provide conditions that allow the exposed pulp to heal and allow the treated tooth to continue development. Vital pulp therapy is most effective when performed 24 to 48 hours after the fracture has occurred.

Vital pulp therapy may also be a part of an orthodontic treatment plan, when crown reduction is used to prevent further oral trauma in certain malocclusions, as an alternative to active orthodontic movement.

Root canal therapy

Animal Dental Clinic: endo-treatment-root-canal-therapy
Dr. Farcas completes root canal treatment on a feline patient.

Even non-vital teeth can be saved.

In root canal therapy, infected or non-vital pulp is removed from the pulp canal, the canal is disinfected and sealed, and the canal is filled with a biocompatible material. A restoration is then placed over the exposed dentin surfaces. This treatment preserves the structure and function of the tooth, removes the source of pain, and prevents or treats the development of apical root abscess. Root canal therapy is recommended in cases of chronic pulpitis, pulp necrosis, and apical abscesses.

For added protection and strength, a tooth that has undergone root canal therapy may benefit from placement of a custom-prepared metal crown.

Tooth extraction

14. Post Root Extraction

Illustration of a recent tooth extraction site. Red: healing tissue; Dark red: healthy gingiva over extraction site.

The alternative to continued pain and/or infection if a tooth can’t be saved.

While generally considered a last resort and done when saving a tooth is either not an option or not in the animal’s best interest, tooth extraction has its place in the treatment of certain cases of endodontic disease. The tooth roots of our pets are significantly larger in comparison to the visible part of the crowns, so extraction and proper closure of the alveolar cavity (socket) requires oral surgery.