Rabbits, guinea pigs, chinchillas, and prairie dogs are herbivorous species.
They have a very specialized nutrition and nutritional requirements.
Complications due to dental disease are wider and more severe when compared to those of carnivores.
The "syndrome" that most rabbit/rodent dental diseases are referred to is called acquired dental disease (ADD).
Clinical exam: Symptoms of dental disease can be varied.
Poor coat quality
Reduced or abnormal feces
Soft or watery feces
Dewlap, facial, and inguinal dermatitis
Mandibular and/or maxillary masses
Dentition of Rabbits
Dental formula: 2I 0C 3P 3M/1I 0C 2P 3M
4 upper incisors: 2 rows of 2 incisors per row; the caudal most upper incisors are much smaller and are called the "peg teeth".
2 lower incisors: In a resting position, the lower incisors occlude with the peg teeth or in a small notch between the rostralmost upper incisors and the peg teeth.
Premolars and Molars
Collectively referred to as the "cheek teeth"
No functional difference between premolars and molars
Each upper arcade has 6 cheek teeth.
Each lower arcade has 5 cheek teeth.
Roots of the upper cheek teeth lie extremely close to the orbit and the nasolacrimal duct.
All teeth in the rabbit are elodont (open-rooted). They continuously grow throughout the life of the rabbit.
In the rostrocaudal view of the skull, the upper and lower cheek teeth are out of occlusion; the upper cheek teeth lie in a more lateral position and the lower cheek teeth are medial.
Acquired Dental Disease of the Incisor Teeth
Commonly, the lower incisors will elongate and protrude rostrally, while the upper incisors will elongate and curl inwards.
Incisor teeth can appear out of occlusion, at abnormal angles, appearing in various states of deterioration.
Congenital (not considered an acquired dental disease, since it is congenital)
Mandibular/maxillary abnormalities (e.g., tumors, jaw fractures, etc., that disrupt incisor occlusion or growth)
Secondary to ADD of the cheek teeth
Traumatic (fractures of the incisor teeth)
Metabolic (e.g., poor nutrition, lack of sunlight)
Acquired Dental Disease of the Cheek Teeth
Three main etiologies have been proposed for the pathophysiology of ADD:
Insufficient wearing of occlusal planes
Fractures due to inappropriate food
The diet of pet rabbits is not identical to that of free ranging rabbits
Even rabbits allowed to graze freely likely do not consume grasses with the same types and amounts of silicates
Nearly 100% of pet rabbits will develop ADD during their lifetime, and many cases will be mild or inapparent
Nearly 100% of the owners feed rabbits improperly
Insufficient wearing leads to excessive elongation of crowns and roots, with bending of the axis of the cheek teeth, deformation of apexes and development of spurs
Physiology of chewing: 4 basic movements in the rabbit
Rostrocaudal, caudorostral, lateral, and vertical
The degree of lateral motion of the jaw is partially determined by the type of food consumed
Hay or natural fibrous vegetable food produces wide lateral movements with reduced vertical motion
Concentrated pelleted food or grains produces reduced lateral movements and more extensive vertical motion (more pressure on roots, less wearing)
Metabolic bone disease, a.k.a. nutritional secondary
Frances Harcourt-Brown proposed this pathophysiologic hypothesis based on the following observations
Many rabbits who live outdoors with exposure to natural sunlight do not develop ADD
Most rabbits with metabolic bone disease demonstrate demineralization of the skull bones
A study performed on more than 80 rabbits with ADD and MBD demonstrated parathyroid (PTH) level much higher than normal levels
The rabbit is prone to hide or minimize clinical symptoms. History is always incomplete, absent, or misleading.
The rabbit is eating nothing or less than normal? How much less than normal?
Complete review of diet offered and consumed
Quantity/quality of stool
Does the rabbit chew frequently without food present?
Is the rabbit interested in food, but dysphagic?
Is the rabbit drinking?
Clinical Exam - Without Anesthesia
Thorough dental evaluation must always be performed in rabbits and rodents, even in the absence of significant history supporting dental disease.
It is mandatory to perform inspection of oral cavity always after the clinical exam without sedation.
Clinical Exam - With Anesthesia
In cases of suspected or confirmed acquired dental disease, it is mandatory to perform a complete clinical examination under anesthesia.
During clinical examination under anesthesia, additional diagnostic testing is very important.
Basic Principles of Anesthesia and Analgesia
Most dental procedures depend on the anesthetic protocol for induction.
Compare and contrast induction with injectable vs. inhalant drugs.
Induction with Injectable Anesthesia
Option 1 (deep sedation)
Option 2 (mild-moderate sedation)
Other injectable sedation options exist.
After 5–10 minutes, rabbit should be sufficiently sedated
From there, administer:
Oxygen (when possible)
Oxygen + isoflurane at 1%–3% if a greater depth of anesthesia is needed
Quicker induction time (2–5 minutes)
Less stressful for most patients
Quicker achievement of surgical anesthetic plane
Respiratory depth and frequency, cardiac activity, blood pressure: more depressed than inhalant agents alone
Longer recovery time (although administering atipamezole at the end of the procedure can be used to reverse the dexmedetomidine and allow for a faster recovery)
Induction with Inhalant Anesthesia
Oxygen + isoflurane at 3%–5% (by face mask)
Longer induction time
Constant restraint of the patient needed during the induction phase
Risk of apnea in rabbits
After induction, the proper surgical anesthetic plane is still not achieved
Respiratory depth and frequency, cardiac activity, blood pressure: less depressed than injectable agents
Quicker recovery time
Patient Intubation for Anesthesia - Is It Always the Best Choice?
Intubation provides more direct delivery of anesthesia to the lungs, provides emergency respiratory access, and can prevent accidental aspiration.
Rabbits can usually be intubated, with some exceptions; special techniques are required for intubation.
The endotracheal tube may interfere with taking radiographs of the skull, and with certain dental procedures.
Nasal intubation, nasotracheal intubation, and orotracheal are all possible options depending on the procedure performed.
Author's preferred anesthetic regimen for diagnosis, initial evaluation, and treatment of dental disease:
Induction of anesthesia with injectable agents
Maintenance of anesthesia with supplemental isoflurane as needed
Maintenance with oxygen alone, if anesthetic plane is deep enough
Allow the patient to breathe room air only if the patient is well oxygenated (can monitor with pulse oximeter)
Removal of the face mask at the instant collection of radiographs
Maintenance of supplemental isoflurane (by face mask or orotracheal intubation) during oral endoscopy
Maintenance of supplemental isoflurane (by face mask or orotracheal intubation) during intraoral dental procedure
Maintenance of supplemental isoflurane (by face mask or orotracheal intubation) during the extraoral procedures
Know your equipment, get accustomed to correct setting for rabbit skull views
Mammography x-ray film provides much greater detail and high resolution
Review different radiographic projections in class: lateral, ventrodorsal, left and right obliques, and rostrocaudal; and (optional) intraoral projection
Normal radiographic appearance: lateral skull radiograph
Lower incisors should occlude with peg teeth
Lines drawn parallel to roof of maxilla and floor of mandible should converge if extended way past the film; parallel or diverging lines are abnormal
Zig-zag line to represent occlusal surface of cheek teeth
Strong uninterrupted line of cortical bone at base of mandible below tooth roots
Normal radiographic appearance: VD radiograph
First upper premolar teeth visible
Evaluate symmetry and quality of tympanic bullae
Evaluate zygomatic arches, orbit, etc.
Normal radiographic appearance: oblique views
Allows evaluation of a non-superimposed view of the cheek teeth
Primarily evaluating the lower cheek teeth roots
May also be able to view upper cheek teeth roots
Normal radiographic appearance: rostrocaudal projection
Evaluate another view of the occlusal surfaces and the resting position of the upper and lower cheek teeth
Nasolacrimal duct can be evaluated radiographically with contrast media
Specialty rabbit/rodent dental instrumentation
Mouth gag cheek dilators spatula
Table top mouth gag device (great investment!)
2.7-mm rigid 30-degree bevel endoscope
Light cable, light source
Videocamera for endoscope recording device
Why Oral Endoscopy?
Technically simple procedure
Requires no special skill or specialization Allows a thorough inspection of the oral cavity offers a magnified perspective of dental disease Highly reduces risk of missing lesion
Facilitates coronal reduction and other therapeutic procedures
Can facilitate endotracheal intubation
Allows recording of pictures for veterinarian's database and for demonstration to the owner
Additional Diagnostic Testing
Culture and sensitivity
Early stage of cheek teeth malocclusion
"Wave mouth" and "step mouth"
Spurs (lower cheek teeth usually get lingual spurs; upper cheek teeth get buccal spurs)
Mid- to late-stage cheek teeth malocclusion
Tongue lesions (ulcerations)
Cheek soft tissue lesions (ulcerations)
Rabbit dental disease is a complex subject
This was just an introduction to the topic
Practicing on rabbits requires familiarity with the complexity of dental disease and dental anatomy, since it is extremely common
Continuing education is exotics is key to success!