Rabbits and Rodents

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					DENTISTRY IN RABBITS AND RODENTS
Dr David E. Clarke
BVSc., Diplomate AVDC, Fellow AVD, MACVSc, MRCVS
Registered Specialist, Veterinary Dentistry

Dental Care for Pets
PO Box 5015
Hallam, Vic, 3803
Phone: (03) 9702 4432
Fax: (03) 9703 1291
david@dentalcareforpets.com.au


Rabbit

The permanent dental formula for the rabbit is I: 2/1 C: 0/0 P: 3/2 M: 3/3. The rabbit
has a deciduous dentition but it is usually shed prior to birth. All permanent teeth are
continuously growing and have an open root structure. There are 4 maxillary incisors,
which are composed of two large and two small (or peg) incisors. The peg teeth side
caudal to the large incisors. There are two mandibular incisors. The cusps of the
mandibular incisors side and occlude between the large and peg incisors. Enamel is
much thicker on the mesial surface of the incisors and on the lateral surfaces of the
premolar and molar teeth, essentially forming a cutting blade. The premolars and
molars have a relatively flay horizontal surface with transverse enamel folds. The
cutting surface does not occlude at rest. There are no canine teeth.

Rodent

The permanent dentition of the rodent is: guinea pig I: 1/1 C: 0/0 P: 1/1 M: 3/3 and rat
I: 1/1 C: 0/0 P: 0/0 M: 3/3. The majority of rodents only have one set of teeth. They
have one maxillary incisor (and this is the major difference between them and the
rabbit). The guinea pig has a complete mouth of continuously growing open rooted
teeth, whereas the rat has continuously growing open rooted incisors but no-erupting,
closed rooted molars. The incisors are very long and in the rat the mandibular incisor
‘root’ extends ventral to all the molars.

Dental disease signs

Many signs are non-secific, but inapetance, difficulty prehending food or swallowing
may be noticed by the client. Weight loss, unkept body hair, maxillo-facial swellings,
drooling, ocular and nasal discharges may be seen. Incisor protrusin is an obvious
sign as well.

Incisor malocclusion

Common in rabbits. If early age – brachygnathism of genetic origin resulting g
in lack of occlusion and overgrowth. If older age – general illness, lack of
chewing, change of diet, infections or tooth fractures may reduce attrition of
tooth and result in overgrowth.

A common problem is owners and veterinary staff ‘clipping’ mandibular
incisors of guinea pigs too short and the guinea pig starving, as the incisors
are longer in guinea pigs compared to rabbits.
Ideally tooth height adjustment can be performed every 3-6 weeks with
appropriate diet change and/or tooth extraction.

Incisor-premolar-molar malocclusion

This syndrome occurs in rabbits from irregular chewing of the premolar/molar
occlusion plane results in a step-mouth or a wave- with hooks and spikes of
elongated enamel that penetrate the tongue or soft buccal pouches, resulting
in pain and inappetance. The end result may be submandibular or maxillo-
facial abcsess formation. Periodontal disease, with increased mobility of and
pathological diastema formation between teeth.

Progression of acquired dental disease in rabbits

Grade 1. Normal
Grade 2. Root elongation and inappetence
Grade 3. Loss of supporting bone and change in bone or tooth position. See
difficulty grooming, tongue lacerations, salivation, drooling, abscesses, tooth
mobility.
Grade 4. Cessation of tooth growth. Root apex destroyed, crowns fracture off
Grade 5. End stage disease. Abscesses, osteomyelitis, mobile teeth.

Treatment involves occlusal adjustment, extraction of affected teeth, abscess
debridement, euthanasia.

Most cases of molar maloccusion in guinea pigs is related to Vitamin C
deficiency. Prevention by supplement with Vitamin C powder 30-50mg per
day or add in parsel,y green capsicum or oranges.

Treatment odontoplasty of affected teeth every 14 days, increase fibrous diet.

Oral examination

Rabbits and rodents have small mouth openings and a long incisor-premolar
diastema, and a long narrow oral cavity. Examination in a conscious animal is
all but impossible. Using an otoscope can give the operator an idea, but
general anaesthesia is required to complete the examination and perform any
work. Inhalation with Isoflurane is easily performed with a face mask, following
by tubing and maintenance with Isoflurane. The tube can be palpated in the
trachea. The use of a speculum over the incisor teeth and buccal cheek
dilators allow better visualisation. Good lighting is mandatory. A tongue
depressor can help as well. A periodontal probe and explorer is indicated to
assess tooth mobility and increased probing depth.

Radiology is necessary to assess periapical pathology and root pathology.
The use of a dental radiograph machine and dental periapical film makes life
a lot easier.

Odontoplasty (crown height reduction)

Odontoplasty of the incisor teeth can be performed using a high speed drill
and bur. Ideally thermal damage can be reduced with a water spray but
anaesthesia is needed to avoid drowning the animal. Clipping with nail
clippers should be avoided to prevent fracturing the tooth. A tongue depressor
can be placed behind the incisor to protect the tongue. The correct angle of
occlusion should be maintained. The use of a cutting disk is not
recommended as they tend to traumatise the soft tissues. Dremel tools should
not be used since they have electrocuted veterinarians and animals in the
USA. Occlusal adjustment of the premolars and molars can be initially be
performed with a pair of molar cutters/ronjeurs and then smoothed with a
hand-held file or a slow speed bur with a bur guard attached. The guard
reduced the chance of soft tissue trauma. If the pulp is inadvertently exposed
then direct pulp capping should be performed, which requires placement of an
intermediate restorative, such as calcium hydroxide over the pulp. The hard
setting composites should not be used as they do not wear like a normal
tooth.

Extractions

General anaesthesia and tube is recommended. Nasal endotracheal
intubation is recommended as it allows a greater space in the oral cavity to
work in. Incisor teeth are exceptionally long and initial separation of the
epithelial attachment with a scalpel blade is recommended. The use of a
curved deciduous root elevator and be used, but care and patience is the best
advice. The other instruments are a 20 gauge needle bent with a curve similar
to a 20 cent piece edge, or a cislak EX-9. The elevator is placed into the
periodontal space and gradually moved in an apical direction, slowly working
it around the circumference of the root. Eventually the tooth will become loose
and it can be extracted with forceps. Early traction, leverage or torque in
excess of what is needed may break the tooth.

Extraction of the premolar and molar teeth are difficult because of the long
thin open ended root. Ways to extract these include, the intra-oral non-
surgical, extra-oral surgical and buccal approach. Intra-oral extraction is
difficult as it requires the tooth periodontal ligament to be separated.
Extraction using a buccotomy, incising the cheek to gain access makes the
extraction easier but post operative care is often worse than the initial dental
problem. Extraction following opening the ventral mandible border or the
maxillary area over the tooth is often easier, and the tooth can repulsed
similar to a horse. Extraction of one tooth from each arcade generally does
not affect the occlusion, but more than this often will result in uneven war and
the need for more frequent odontoplasty.

Treatment of abscess

Abscesses can be generally assumed not to be treatable, but it worth trying
before the rabbit euthanased, as palliative care can be achieved,
Debridement, extractions and life-long antibiotics are needed. The abscess
must be completely cleaned out and any teeth in the area removed. Long life
antibiotics such as Baytril, Keflex or Zithromax can be given. Dosages: Baytril
15mg/kg sid for rabbits and 10 mg/kg for guinea pigs and rats; Keflex 125 mg
powder 30mg/kg bid for rabbits (in conjunction with Questran for gut
protectant), Zithromax 600mg powder for suspension 15 mg/kg bid for rabbits.

 An alternative method is to pack the abscess cavity with calcium hydroxide
paste, but it is very caustic and can result in bone necrosis. Another option is
to pack the cavity with antibiotic impregnated methylmethacrylate beads, but
has not shown a lot of promise. A newer treatment is a pack the area with
Doxirobe, a doxycycline impregnated polylactic acid gel, which degrades over
weeks and releases doxycycline into the area.

References

Crossley DA (1995). Clinical aspects of lagomorph dental anatomy: the rabbit
(Oryctolagus cuniculus). Journal of Veterinary dentistry, 12:137-140.

Crossley DA (1995). Clinical aspects of rodent dental anatomy. Journal of Veterinary
Dentistry. 12:131-135.

Crossley DA, Penman S (1995).
B.S.A.V.A. Manual of Small Animal Dentistry 2nd Ed. Cheltenham: British Small
Animal Veterinary Association.

Verstraete FJ (1999) Rabbit and Rodent Dentistry in Small Animal Dentistry. UC
Davis, School of Veterinary Medicine. Department of Surgical and Radiological
Sciences.

				
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