Dental Care

Dental care is vital to the health and longevity of exotic pets. Unlike dogs and cats, who often make their dental woes obvious by coming to you with “death breath”, the signs of dental malaise and discomfort in our exotic pets can be so subtle as to go unnoticed until they result in severe health issues. This is another reason regular wellness exams are so important.

The front teeth (incisors) in rabbits and and herbivorous rodents such as chinchillas, guinea pigs, degus and prairie dogs are open rooted or aradicular; meaning they never form true tooth roots. They are also elodont, meaning that they continually grow throughout their life. Germinal tissue, located at the base of the teeth, continuously forms enamel to cover each tooth as the teeth constantly grow. Because of this, there is no anatomic difference in the tooth above or below the gum line like dogs and cats have.

The 4 large incisors have a sharp edge and scissor-like action that are mainly used to slice through tough plant material. Except for guinea pigs, most rodent species have hard yellow – orange enamel on the front of the incisors. Rabbits do not have this enamel, and have a small extra pair of incisors behind the upper incisors call peg teeth, which differentiates them from rodents.

The molars and premolars, referred to as cheek teeth, are used for grinding food into smaller pieces. In rabbits, guinea pigs and chinchillas, the cheek teeth are open rooted like the incisors and grow throughout life. This helps them process the high fiber plants that make up their diet. Omnivorous rodents such as rats and mice have rooted cheek teeth. Rabbits have 22 cheek teeth, and most rodents have a total of 16-20 teeth.

The cheek teeth of most herbivore species we see (rabbits, guinea pigs, chinchillas) are cylindrical and curve naturally as they grow. The flat grinding surface (also called the occlusal plane) of the upper or maxillary cheek teeth curves out toward the cheek, while the occlusal surface of the bottom (mandibular) cheek teeth curves toward the tongue.

The dental structure of a rabbit

Rabbit skull: (A) Cheek teeth. (B) Diastema. (C) Four maxillary (upper) incisors, including the 2 smaller peg teeth situated directly behind the larger set of incisors, and 2 mandibular (lower) incisors (Photo: Capello et al).

If their diet is insufficient in fiber, such as a pellets-only diet, they will be unable to properly wear down their teeth. When teeth do not meet properly in this way, it is called a malocclusion. The crowns (the visible section of the tooth) can then grow higher and meet the opposing teeth abnormally, leading to abnormal wear and the eventual development of sharp edges or points (also called spurs). Sharp tooth edges are painful and can get long enough to cut the tongue and the inside of the cheeks. Maloccluded teeth can also create abnormal pressure against one another, which can cause the tooth roots to become impacted, elongated and inflamed. Tooth root impaction is extremely painful and will eventually lead to an infection in the bone, frequently presenting as a lump on the jaw called an abscess.

Overgrown teeth cause painful ulcer in rabbit cheek

Intra oral view of a rabbit, notice how the left mandibular (lower) cheek teeth have penetrated into the tongue creating a painful ulcer. Filing the teeth is a temporary fix, but surgical extraction provides a long term management.

CAUSES

Dental disease results from any anatomic or physiologic abnormality that interferes with eruption or wear of incisors and/or cheek teeth; they can be congenital (from birth) or acquired (develop during adulthood).

Severe incisor malocclusion in a rabbit

Incisor malocclusion on a rabbit. Most of the time this is congenital but it can also be due to trauma, infection or systemic disease. Surgical extraction of all incisors is the treatment of choice.

Acquired causes of dental disease include trauma, systemic disease, neoplasia (cancer), and improper nutrition. Systemic disease that causes any change in their normal diet and eating patterns may lead to dental disease. A systemic disease that involves decreased calcium levels may result in changes in jawbones and altered tooth placement.

Improper nutrition is the most common cause of dental disease seen in our practice. Improper food items prevent normal tooth wear, eventually leading to dental disease.

CLINICAL SIGNS

Chinchilla tooth overgrowth cutting into the cheek

Intra oral view of a Chinchilla, notice how the right maxillary cheek teeth have penetrated into the buccal mucosa creating a lot of pain. Filing will ease the pain but assessing the rest of the teeth is important to make a long term treatment plan.

Being prey species, rabbit and rodent patients tend to hide clinical signs of illness until they are remarkably debilitated. Clinical signs are directly related to the severity of the disease. If the disease is mild, they  may not show any signs. However, once one tooth is affected, over time the dental disease will affect other teeth. The following clinical signs may be associated with dental disease:

* Oral pain can cause anorexia and difficulty eating. Changes in fecal output, size, and appearance will often accompany this symptom.

* Excessive drooling or area of wetness or hair loss under the chin.

* Nasal discharge. Elongation of roots, especially the maxillary (upper) incisors, may irritate sinuses, resulting in nasal discharge.

* Matting of hair on forelimbs.

* Increased tearing or eye bulging.

* Facial masses or swellings can be caused by abscesses forming around the affected teeth.

* Bruxism (tooth grinding) can be an indication of pain

DIAGNOSIS

Like most diseases we see, a thorough patient history and physical examination are a must. An endoscopic oral examination with the patient under sedation is our next step. We also recommend a blood analysis to better evaluate the patient and understand the disease process.

Dental radiography is an essential diagnostic tool that should be performed for all patients with suspected dental disease. The bulk of the teeth and the supporting structures are below the gum line, hidden from view during the oral exam, which shows only about 20-30% of the actual tooth substance.

Dental radiography shows how much of the tooth is below the gumline

Area highlighted in green is within the mandibular bone.

Anatomical lines show severity of disease progression

There are set anatomical lines that can be projected into the radiograph that help us further stage the disease process. (Photo E. Böehmer).

Dental radiograph showing severe dental disease

In advanced dental cases like the image above prognosis usually is poor.

In our practice we have found that skull/dental CT scans are far more sensitive than conventional radiographs (x-rays) and provide a better evaluation of the nasal passages, spaces behind the eyes and middle ear structures which may be affected in cases of advanced dental disease. We can create 3-D reconstructions and panoramic views to better understand the disease process.

Our CT imaging provides much more detailed views than traditional radiography

This is a CT image of a Chinchilla’s skull. Yellow arrows point to root elongation and penetration of bone in the maxilla and mandible.

Our CT allows for 3-D and panoramic views which far surpass traditional radiographic methods

Panoramic view of a rabbit’s oral cavity.

TREATMENT

Crown height reduction (trimming of teeth) can often be curative in early stages when accompanied by diet correction and other preventive measures. In moderate to severe cases they will need to be performed repeatedly. Overgrown incisors or cheek teeth should be trimmed using a dental bur or trimming forceps designed specifically for crown reduction. Nail trimmers and other manual cutting tools should never be used because they can result in root damage, tooth fractures or splinters, and abnormal regrowth.

Tooth extraction with the patient under general anesthesia is recommended for any tooth that is loose, infected/abscessed, fractured, or severely maloccluded. They can be performed intra-orally or extra-orally, depending on the accessibility of the diseased tooth and the size of the patient.

Abscess management of infected teeth can be a very involved and prolonged process. Mandibular abscesses are more common than maxillary abscesses and often present as palpable masses. Radiography or CT will help in determining the site of origin. The goal is to remove the cause, which is generally one or more infected teeth or bone. Further treatments may include repeated lancing and flushing, systemic antibiotics, complete surgical excision, and antibiotic bead impregnation. These are painful procedures so pain management and nutritional support are needed before, during and afterward.

PREVENTION

Proper nutrition and husbandry are essential for the prevention of dental disease. Feed unlimited, good-quality grass hay (timothy, brome, orchard), and a handful of fibrous, green, leafy vegetables. Pellets are not a necessary for adult animals, if pellets are fed, they should be timothy hay based, not alfalfa based, with no extra fruit, corn or other additives. Only 1-2 tbsp should be fed daily. UV-B light supplementation has been proven to improve Vitamin D3 production in chinchillas and guinea pigs and may be of benefit to animals with dental disease.