Exotic animal dentistry (Proceedings)

Anesthesia

Limitations

For small pets, such as most domestic rabbits, guinea pigs, chinchillas, and hedgehogs (the exceptions being ferrets and large rabbits), intubation is generally not an option given the equipment available at most veterinary hospital. Pre-anesthetic blood panels, or at least a PCV/TP, should be run on those patients large enough to perform venipuncture. These same patients should also have intravenous catheters placed for emergency access +/- fluid administration. However, the great majority of pocket pets do not have veins large enough to allow this access. Pre-anesthetic fasting should be avoided, as these small patients are at a higher risk for hypoglycemia.

Pre-medication

Most pocket pets benefit from pre-medication to reduce the stress associated with induction, and to provide pain management. Some procedures, such as oral examinations, can be done using only chemical restraint. Drugs such as ketamine, hydromorphone, midazolam, medetomidine, and glycopyrrolate are commonly used to provide sedation.

Induction

A small cat or kitten anesthetic mask on a non-rebreathing system can be used to induce general anesthesia with isoflurane and O2 administration. For hedgehogs and small rodents, chamber induction must be used. In the absence of a chamber, a large canine anesthetic mask places over the patients with the mask's d diaphragm pressed firmly against the table will do.

Maintenance

Maintaining your patient once induced, while still allowing access to the oral cavity, can be challenging. In larger patients where intubation is unsuccessful, a small anesthetic mask can be placed over the pet's nose only. In tiny patients, stretching a dental dam or the palm of an examination glove over the end of the Bain system anesthetic hose, and cutting a "X" into the stretched rubber with a scalpel blade, then placing the patient's nose through the "X" will allow anesthetic and oxygen delivery while freeing the mouth. This improvised "mask" will require one person dedicated to holding it onto the nose to keep it in place. This person can also be dedicated to anesthetic monitoring.

Monitoring

Monitoring can be done via pediatric stethoscope, Doppler blood pressure monitor (crystal can be taped directly over the fur of the chest in most patients), or a lingual SPO2 sensor places on the foot, ear, or scrotum. Visualization of the mucous membrane color (tongue is especially useful) and the chest movements of respirations is essential. Special care must be taken to ensure that the patient's body temperature is maintained. Circulating warm water blankets, microwavable oat bag, and exam gloves filled with warm water can all be used.

Pain management

This is includes any narcotics used in premedication. NSAIDs such as meloxicam can also be used pre, intra, and post-operatively. Local anesthesia is usually impossible, and assessing pain in these patients can be difficult, so every patient who has undergone a potentially painful procedure should be given pain relief. Some signs that pain relief is not adequate are teeth grinding, hiding, depression, and anorexia.

Oral antomy & dentition

Lagomorphs & rodents [lagomorphs 2(i2/1:c0/0:pm3/2:m3/3); guinea pigs &chinchillas 2(i1/1:c0/0: pm1/1:m3/3); rat/mouse/hamster 2(i1/1:c0/0:pm0/0:m3/3)]

It is very difficult to perform a complete oral examination on the awake patient, as the small and often long and narrow oral cavity of these animals allows only the anterior portion of the mouth to be readily visualized. Using an otoscope to assess the check teeth of awake rabbits, chinchillas, and guinea pigs can be helpful.

The primary dental different between lagomorphs (rabbits) and rodents (guinea pigs, chinchillas, rats, mice, hamsters) is that lagomorphs have 4 maxillary incisors – 2 anterior and 2 posterior. These posterior incisors are commonly referred to as "pig teeth." Rodents have only 2 maxillary incisors. The extra incisors of lagomorphs are important in chewing. Rabbit chew in a side-to-side, scissors-like fashion, with the 2 lower incisors cutting back and forth between the peg teeth and larger, anterior upper incisors.

Another important different between lagomorphs and most rodents (the exceptions being guinea pigs and chinchillas) is that all the teeth of lagomorphs (and guinea pigs and chinchillas) grow continuously and must be worn down – either by chewing or by human intervention. In rodents other than guinea pigs and chinchillas, only the incisors continue to erupt.

The enamel on the incisors of both rodents and lagomorphs is thickest on the facial surface, thinning at the distal and mesial surface. During normal wear, this results in a sharp, chisel-like tooth. Also, the incisor teeth of most rodents are normally a yellow-orange in color.

Ferrets 2(I3/3:C1/1:PM3/3:M1/2)

Because ferrets are carnivores, their oral anatomy appears more like the anatomy most of us are accustomed to seeing in dogs and cat. In fact, their teeth and oral cavity are very similar to the cats.

Hedgehogs 2(I1-3/2-3:C1/0-1:P3-4/2-4:M3-4/3)

As a member of the order Insectivora, the oral anatomy of hedgehogs is quite different than other pocket pets. Anatomical characteristics of insectivores include small, long, narrow snouts, and a primitive tooth structure. The incisors are used as forceps for picking up small prey, and the canines often resemble incisors or first premolars. Hedgehogs can have from between 30-46 teeth. A complete oral examination of hedgehogs requires anesthesia or chemical restraint because of their self-protective behavior of rolling into a tight ball when stressed.

Dental problems

The lack of close personal contact and of the ability to regularly examine the mouths of most exotic patients can greatly delay the detection of oral problem until they are well advanced and cause such clinical signs as anorexia and weight loss.

Lagomorphs & rodents

a common dental problem seen in both lagomorphs and rodents is malocclusion, causing overgrowth of incisors +/- cheek teeth. Secondary tongue entrapment, soft tissue lacerations of the tongue and buccal mucosa, and excess salivation ("slobbers") can occur. Malocclusions are classified as traumatic, resulting from a traumatic injury to a tooth causing a loss of a portion of the crown and subsequently the loss of wear on the opposing tooth; or atraumatic, normally resulting from hereditary conditions such as a mandible which is too narrow or too short, nutritional deficiencies, weakness of the jaw, or behavioral problems. Traumatic malocclusions are treated by smoothing the edges of the traumatized tooth to reduce soft tissue injuries, capping the pulp with calcium hydroxide if exposed, and performing routine crown height reduction (also referred to as occlusal leveling or odontoplasty) on the opposing tooth until the traumatized tooth regrows. Atraumatic malocclusions can be treated with routine odontoplasty (usually every 6-8 weeks), extraction, dietary changes such as increasing the amount of roughage vs. pellets in the diet, or reducing the animal's stressors in case of behavioral problems such as cribbing or barbering.

Other problems seen in rodents and lagomorphs include tooth root abscesses, often treated with antibiotics, lancing, and/or extraction (if a tooth is extracted, extraction of the opposing tooth should be considered to prevent its overgrowth); oral viral papillomas in rabbits; gingival hemorrhage and loose teeth in guinea pigs secondary to scurvy; cheek pouch impaction causing stomatitis in hamsters (treated by removing the impacted material and using antibiotics); and gingivitis, stomatitis, and excessive salivation caused by rough edges on water bottles, feeders, or cages. Periodontal disease is uncommon, except in hamsters, which may present with facial swelling ventral or rostral to the eye resulting from abscessed tooth roots due to periodontal disease. Cheek pouch eversion can also occur in hamsters. The pouch should be replaced and sutured through the cheek to prevent re-eversion.

Ferrets

Fractured teeth, especially canine teeth, and periodontal disease are common reasons that ferrets present for dental treatment. Dental prophylaxis, extractions, and endodontic procedures are nearly identical to those performed in the cat.

Hedgehogs

Periodontal disease has been described in both captive and wild hedgehogs, though the cause and frequency are not clear. Owners will often present their hedgehogs because they have noticed a bad smell associated with the pet, and/or inappetance. Treatment involves antibiotics and extraction of the diseased teeth.

Dental instruments

Many specialized dental instruments exist for pocket pets. These are designed for the particular needs of accessing small, long narrow mouths, retracting cheek pouches, and cutting, filing, and extraction of continuously erupting teeth.

A useful set of instruments would include:

     – rodent incisor luxator

     – rodent molar/premolar luxator

     – Crossley rabbit luxator

     – rodent molar/premolar extraction forceps

     – rodent mouth gag

     – pouch dilators

     – molar/premolar rasp

     – rodent tongue depressor (or use regular wooden tongue depressor split in half lengthwise)

     – low-speed burs to use for crown height reduction (HP5, HP8, HP558)

     – high speed burs for use in incisor trimming and extraction (FG330, FG701)

     – rodent molar/premolar cutters if no drill available

Other useful "tools" include magnifying loupes; 18G needles to use as luxators for extracting hedgehog teeth; a saliva ejector suction tip fitted with a urinary catheter to suction fluid and debris from the mouth; and cotton tipped applicators to staunch blood flow from extraction sites, absorb fluid from the mouth, and to remove debris and bits of teeth from the mouth.

Husbandry & homecare

Post-operative care

Patients who have had oral surgery may need nutritional support until healed. Rodents and lagomorphs may be offered or force-fed a variety of soft foods, such as Oxbow Critical Care, yogurt, or hay, vegetables, and water pureed in a blender. Ferrets and hedgehogs may be fed high-protein canned cat food such as Hill's a/d2. 35 ml syringes with catheter tips work well to force feed ferrets and larger rabbits; abscess-flushing syringes with tips trimmed off halfway work well to force feed small rabbits, chinchillas and guinea pigs; and 1-3 ml syringes work well for tinier patients.

Distasteful medications like enrofloxacin may be mixed with apple or other juices in the dosing syringe to improve palatability.

If the patient has had extra-oral surgery, such as abscess lancing, bedding and debris may stick to the site. Owners should be advised to keep the area clean using a cloth and warm water several times daily. A "weak-tea" solution of povidone-iodine and water, or sterile saline can be used to flush abscesses once or twice a day.

Prevention

To aid in preventing dietary-related malocclusions, owners should be encouraged to feed rabbits, guinea pigs and chinchillas the majority of their diets as roughage, such as Timothy Hay, fresh greens and vegetables, and at most 1/3 of their diet should consist of commercial pellets. Guinea pigs must also be given Vitamin C supplementation to prevent scurvy. Stress can often be reduced by enlarging the animal's cage, removing or adding companions, or adding stimulation such as toys and mazes. Chew aids, such as wooden blocks, can help wear down rodent incisors.

Ferrets can be trained to have their teeth brushed daily to prevent periodontal disease just like cats and dogs, and using the same products. Routine dental prophylaxis under general anesthesia is recommended for these patients.

Reference

Clarke, DE. The Veterinary Clinics of North America Exotic Animal Practice: Oral Biology, Dental and Beak Disorders. Philadelphia: WB Saunders, 2003.

Holmstrom SE, Frost P, Eisner ED. Veterinary Dental Techniques for the Small Animal Practitioner. Philadelphia: WB Saunders, 1998.

Kertesz P. A Colour Atlas of Veterinary Dentistry and Oral Surgery. London: Wolfe, 1993

Quesenberry KE, Carpenter JW. Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery. Philadelphia: WB Saunders, 2003

Wiggs RB, Lobprise HB. Veterinary Dentistry: Principles and Practice. Philadelphia: Lippincott-Raven, 1997