Brief Overview of Dental Disease in Pet Rabbits

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Definition
Dental disease in rabbits can be congenital or acquired, and can involve incisors, cheek teeth, or both. Primary disease of incisors often produces secondary disease of cheek teeth, or vice versa. 

Incidence/Prevalence
Exact data on the incidence of dental disease in rabbits are unavailable; however, exotic animal practitioners report it as a common presentation in practice. There appears to be no sex predilection.

Causes
Congenital dental disease is secondary to jaw malformation. For acquired dental disease, there are 2 leading theories regarding the cause: 1) inadequate wearing of teeth due to inappropriate diet (ie, a diet low in high-fiber hay), and 2) metabolic bone disease leading to thinning of the jawbone and alveolus. Dental disease is also produced by traumatic injury to the jaw or teeth.

Risk Factors
Rabbits that are receiving inappropriate diets (low-fiber pellet mixtures, grains, seeds, and nuts) appear at higher risk and comprise the majority of patients in clinical practice. However, many rabbits receiving poor diets do not develop severe dental disease, suggesting that other unknown factors may play a role.

Pathophysiology

All rabbit teeth continually grow throughout the life of the animal. In the normal rabbit, incisors and cheek teeth are maintained at proper length and shape by the action of teeth upon teeth during normal chewing and jaw movements. Any condition that disrupts normal wear can lead to elongation and dental disease. 

Signs
History. Some owners may notice substantially abnormal or overgrown incisors, or facial swellings produced by dental abscesses. However, patients can present with a variety of clinical signs, many seemingly un-related to disease of the oral cavity.

Physical Examination. Any of the signs noted in Table 1 can be detected at physical examination. Careful examination of the incisors can reveal subtle deviations in length and shape. Examination of the oral cavity of the conscious rabbit with an otoscope or other similar device can reveal abnormalities of cheek teeth. However, dental lesions are commonly missed with this technique; it must never be used to rule out dental disease in patients with clinical signs or histories suggesting otherwise. 

Diagnosis

Definitive Diagnosis
Complete evaluation of dental disease in rabbits requires at minimum full oral examination performed under anesthesia and skull radiographs. Anesthetic protocols for rabbits are described elsewhere. Oral examination is greatly facilitated by endoscopy. Proper instrumentation is required for thorough evaluation (Table 1, Figure 1).

Figure 1

Imaging
Dental radiology is critical for evaluating tooth roots, staging dental disease, and determining the degree of overgrowth (Figure 2). Radiographs taken after a procedure help determine whether correction or reduction is adequate. Five views are required for complete evaluation: lateral, right oblique, left oblique, dorsal/ventral or ventral/dorsal, and rostral/caudal. Dental radiographs must be of excellent quality in terms of both technique and positioning. Computed tomography of the skull is extremely useful to help characterize dental disease in rabbits.

Figure 2

Treatment

The goals of treatment of dental disease are to restore incisors and cheek teeth to as close to normal length and shape as possible; control infection (including abscesses), inflammation, and pain; and address secondary disease processes.

Restoration of Length & Shape
Normal length and shape are restored by using precision dental equipment (Figure 3). Efficacy of treatment is determined by oral examination and evaluation of postprocedural radiographs. 

Figure 3

The ideal handpiece is straight, with long-shank burs rotating at 25,000 to 50,000 revolutions per minute. Higher speeds are too dangerous and lower speeds are less effective and can create excessive thermal injury as more pressure is used to compensate for inadequate speed. Burr shape is largely based on surgeon preference. The author prefers conical silicon and round metal burs.

The use of cutting instruments to reduce the length of teeth should be avoided-they cannot restore normal shape and can result in rough, jagged edges and iatrogenic fracture of the reserve crown, leading to dental abscesses. 

Extractions
Teeth that are loose or abscessed should be extracted by using intraoral or extraoral approaches, depending on tooth location and accessibility (Figure 4). In addition, early extraction of traumatically fractured teeth prevents the onset of secondary complications.

Figure 4

Extraction of normal opposing cheek teeth is not recommended because the procedure is difficult, and every effort should be made to maintain normal teeth for as long as possible. Normal wide grinding motions often result in adequate wear of teeth, despite extraction of an opposing tooth. 

However, loss of both primary maxillary or mandibular incisors will require lifetime reduction of the length of the opposite teeth, or extraction. Similarly, loss of several adjacent cheek teeth often necessitates lifetime reduction of the opposite cheek teeth. In most cases, irreversible damage to tooth roots results in progressive dental disease, which will require lifetime treatment.

Abscesses
Many options exist for treating dental-related abscesses, and most authorities agree that treatment success depends on wide excision of the abscess, capsule, and diseased teeth or bone. 

Options for wound management after surgery include closure with application of antibiotic-impregnated polymethylmethacrylate beads or other materials. The author prefers marsupialization of the abscess site for repeated flushing and debridement until healing by second intention occurs (See Procedures Pro: Surgical Treatment of Periapical Mandibular Abscess in Rabbits, September 2006, available at www.cliniciansbrief.com). Simple lancing of dental abscesses without aggressive removal of diseased teeth and bone rarely results in resolution. 

Since many dental abscesses involve anaerobic organisms, aerobic and anaerobic culture and sensitivity help plan antibiotic therapy. For some cases of severe osteo-myelitis, humane euthanasia may be the best alternative.

Treatment of Secondary Complications
Many rabbits with advanced dental disease are moderately debilitated and may not return to normal food consumption right away. Treatment plans often include fluids, analgesia, and support feeding. Anorexic rabbits can be hand fed by syringe feeding of liquid critical care diets for convalescing herbivores (Critical Care, www.oxbowhay.com). Rabbits that refuse hand feeding may require feeding by nasogastric tube.

Nutritional Aspects
Increasing the amount of high-fiber hay in the diet of rabbits with acquired dental disease may slow down disease progress because consumption of hay increases grinding motions of teeth. All rabbit owners should be encouraged to feed their rabbit unlimited high-quality grass hay. 

Follow-Up

Client Education
Owners must understand the extent and severity of their pets' dental disease, and the level of commitment in terms of aftercare and finances that will be required for management. 

Prevention
Acquired dental disease due to insufficient wear can be prevented by feeding the rabbit high-quality high-fiber hay, with limited hay-based pellets and greens. It is uncertain how dental disease due to metabolic bone disease can be prevented, as this appears to be a consequence of early nutrition and may exist before the rabbit is acquired. Rabbit breeders must strive to provide high-quality nutrition to gestating and lactating rabbits and to their young.

Complications
Complications of treatment for dental disease include anesthetic death, damage to oral structure during treatment, and (in the case of treatment of dental abscess and osteomyelitis) jaw fracture, in particular, mandibular fracture.

In General

Relative Cost
Treatment of congenital incisor malocclusion (incisor extraction) is expensive but offers the possibility of complete cure ($$$). Treatment of acquired dental disease, with the exception of very mild abnormalities, is lifelong and therefore cumulatively expensive ($$-$$$ per treatment). The most expensive aspect of treatment of dental disease is treatment of severe dental abscess and osteomyelitis, which can involve advanced techniques, such as hemimandibulectomy ($$$$-$$$$$).

Prognosis
With excellent owner compliance, prognosis for management of acquired dental disease is good. Cure is unlikely, with the exception of very mild early acquired disease, traumatic injuries, or congenital incisor malocclusion. Failure to manage acquired dental disease results in increasing debilitation and death from starvation or secondary complications.

See Aids & Resources for references, contacts, and appendices.

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Table 1. Instrumentation for Diagnosis & Treatment of Dental Disease in Rabbits

Rabbit mouth speculum

Tabletop rabbit  mouth gag

Cheek spreaders, various sizes

Spatula

Crossley cheek tooth extractor

Crossley incisor extractor

Dental probe

Extraction forceps

Moist cotton tip applicators

Variable-speed dental equipment for burring

Figure Credit
Figures reprinted from Rabbit and Rodent Dentistry Handbook. Lennox AM (ed)-Ames, IA: Blackwell Publishing, 2005, with permission from Blackwell.   

BRIEF OVERVIEW OF DENTAL DISEASE IN PET RABBITS • Angela M. Lennox
Suggested Reading

Rabbit and Rodent Dentistry Handbook. Lennox AM (ed)-Ames, IA: Blackwell Publishing, 2005.
Small mammal dentistry: Parts I and II. Crossley D, Aiken S. In Quesenberry K, Carpenter J (eds): Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery-Philadelphia: Saunders/Elsevier, 2003, pp 370-382.
Textbook of Rabbit Medicine. Harcourt-Brown F -New York: Butterworth-Heinemann, 2002.