Video: Oral examination in rabbits and rodents
Video created and narrated by M. Scott Echols, DVM, Dipl. ABVP-Avian.
Oral examination in rabbits and rodents is an essential part of the physical exam. A wide range of dental abnormalities may be seen in rabbits (Oryctolagus cuniculus), guinea pigs (Cavia porcellus), and chinchillas (Chinchilla laniger) including tooth overgrowth, dental fractures, and dental spurs or spikes of the cheek teeth. Severe dental disease can even lead to bridge-like malocclusion and tongue entrapment in guinea pigs.
Small herbivores with dental disease may present with a host of clinical signs including anorexia, weight loss, jaw swelling, hypersalivation, bruxism, and an inability to fully close the mouth. Tearing, exophthalmos, or even ocular proptosis can be seen when an impacted or diseased tooth invades the orbit. Oral examinations should be performed during each complete physical examination, for both symptomatic and clinically normal individuals alike.
Certain physical examination findings may suggest dental disease:
- Carefully palpate the cheek and jaws for evidence of swelling
- Evaluate your patient for signs of facial asymmetry
- Check for evidence of drooling or ocular discharge
- Rabbits and rodents with heavy drooling may even present with moist dermatitis on the chin or the skin folds of the dewlap
Because oral examination can be quite stressful, this procedure is typically performed last after the remainder of the exam has been completed.
Evaluate the incisors
Incisors can be easily inspected during routine physical examination. Normal incisors have a characteristic chisel shape, and the tips of the mandibular incisor normally rest behind the maxillary incisors. Also note incisor color. The enamel of normal rabbits and guinea pigs should be white (Fig 1), while most rodents possess yellow incisors (Fig 2).
Oral examination is challenging in rabbits and rodents due a number of unique anatomic features:
- The opening to the oral cavity is relatively narrow, making access to the teeth challenging
- The long, narrow oral cavity contains redundant tissue along the sides and a relatively large, fleshy tongue makes visualization difficult
- The occlusal planes of the cheek teeth are also angled in guinea pigs
To perform an oral exam, you will need a flat surface on which to place your patient and a towel to securely wrap the animal (Box 1). Proper examination of the rabbit or rodent also calls for an assistant to safely and securely restrain the patient.
|Box 1. Equipment needed for the small herbivore oral exam|
In the conscious patient, use a mouth speculum with a bright light source to examine the oral cavity. One of the most effective instruments is a human nasal speculum. Many small mammal veterinarians specifically recommend Welch Allyn’s illuminated bivalve nasal speculum (Fig 5 below). A less effective instrument for oral examination is an otoscope with a long otoscope cone (Fig 3).
Guinea pigs, and to a lesser degree chinchillas, tend to hold some food in their cheeks. Use cotton tipped applicators to gently swab out the mouth as needed.
- Hold the head securely either by grasping the head like a football with the palm on top of the head and perpendicular to the nose OR
- Grasp the head with the palm of your hand running parallel to the nose and your index and middle finger spread with a finger placed on each side of the muzzle (Fig 4).
- Insert the speculum into the diastema or the space between the cheek teeth and incisors (Fig 5).
- Open the speculum and carefully inspect the gums, tongue, and all of the teeth on that side of the mouth.
- Repeat the procedure on the other side of the mouth.
- The normal small herbivore will often begin normal rotary chewing motions as soon as the speculum is introduced. Inspection of the oral cavity is best performed when the animal pauses in between chews. Take advantage of the chewing motions, to evaluate your patient’s ability to move its tongue.
Since the mandibular teeth grow inward and the maxillary teeth grow outward, this will determine the location of any possible spurs or sharp spikes. Spikes and spurs from mandibular cheek teeth may develop over the tongue (Fig 6), while maxillary points are directed into buccal mucosa (Fig 7).
Oral examination under chemical restraint
Detecting a dental abnormality in the conscious patient can be rewarding, however a negative oral exam in the conscious small herbivore cannot possibly be used to rule out dental disease because of all the special challenges encountered. Instead heavy sedation or general anesthesia is indicated when a detailed evaluation is required (Fig 8). Chemical restraint is also recommended for oral exams in particularly uncooperative or anxious individuals.
As your patient’s head is manipulated during the exam, it will be the responsibility of the anesthetist to insure the neck remains extended (Fig 9).
In addition to a better field of view, chemical restraint also allows the use of oral endoscopy. Endoscopic examination allows detailed observations of the cheek teeth, mucosal surfaces as well as the tongue and hard palate.
Carefully examine all parts of the oropharynx in the sedated patient including the angle of occlusion. Also apply lateral pressure to the crowns to check for evidence of purulent discharge.
Even when using oral endoscopy, it can be difficult to accurately judge whether chinchilla cheek teeth are normal. Proliferation of the gingiva is sometimes associated with dental disease. This gingival hypertrophy can be misleading as it can make an abnormally long crown appear normal on exam. Regions of gingival proliferation should always be explored with a probe.
Dental formulas and charting
|Table 1. Dental formulas of select small mammals|
Visit Rabbit Dental Chart and Rodent Dental Chart for diagrams and clinical forms for download.
If the patient’s clinical condition allows, skull radiographs should be taken at the same time an oral exam is performed under chemical restraint in all small herbivores. A complete radiologic examination should include lateral, ventrodorsal, and oblique projections.