(Nomenclature in this paper for anatomical orientation of the teeth will
be the standard dental terms: Coronal and Apical, for direction towards or
relationships to, the Distal and Proximal extremities of the tusk respectively.)
Ten Pacific walrus aged between 4 and 6 years were housed in Moscow Zoo.
Seven of the animals developed bilateral tusk abrasions, where the teeth were worn down to
within 4.0 to 1.0 cm of the gingival margins. This occurred through normal "digging" behaviour
at the bottom and the sides of their concrete lined pools. The animals exhibited various degrees
of malaise and depression for over one year that gave cause for concern. Three of the fourteen
tusks had their pulp cavities exposed. Facial swellings developed in all the affected animals
and five walrus exhibited facial sinus tracts medial to the eyes, with a purulent discharge. The
infections responded to oral antibiotic treatment, but recurred after the medication was
The anatomy of the permanently dilated apical foramen of the walrus tusk
does not allow thorough debridement and precise obturation of the pulp cavity, which is a
prerequisite of root canal therapy. Therefore endodontic treatment of these teeth is
Eight walrus were treated by bilateral tusk extractions under inhalation
anaesthesia. One of the animals operated on was developing bilateral cataract and had his
healthy tusks extracted for prophylactic reasons, as he was becoming increasingly disorientated
with his environment and likely to damage his tusks.
Walrus tusks may be extracted by an internally collapsing technique or
through a mucoperiosteal flap procedure. The walrus tusk, even when exhibiting a pulp cavity
exposure, will have an irregular, reparative dentine plug of variable depth obstructing the
canal. This barrier can extend close to the apical extremity of the tusk obliterating the
guidance the pulp cavity may afford, thereby making the creation of a symmetrical, hollow tusk
that is required for longitudinal sectioning, unpredictable.
The position of the walrus on the operating table was determined by the
anaesthetist's requirements to maintain the animal. Sternal recumbency made access in performing
the internally collapsing technique difficult and time consuming.
Thirteen tusks were removed through a flap procedure, while three were
extracted through the internally collapsing technique. Most of the animals were eating within 24
hours after surgery. The sinus tracts healed, and the facial swellings or purulent discharges
did not reoccur in any of the animals over a follow-up period of ten months.
On examining decalcified sections of one of the infected tusks, a thin layer
of largely acellular dentine lined the pulpal surface of the dentinal wall. The junction of the
dentinal plug and the pulpal wall of the tusk did not form a seal and pus extended to the
abraded coronal surface. Some chronically inflamed pulp remains were observed in the infected
tusk's pulp cavity. The microscopic features support a diagnosis of pulpitis and pulpal
necrosis, which were secondary to pulpal exposure from the abraded surface. It appears that the
speed of the abrasion was too fast to allow the formation of an organised secondary dentine
barrier that could produce an impermeable seal.
Walrus tusks which have suffered severe abrasion to their coronal
extremities should be judged to have had the vitality of their pulp tissues compromised and
their extraction ought to be considered at signs of related pain, malaise, swelling or
infection. At the same time such surgery must not be taken lightly and the team should be
prepared for all eventualities. Depending on the operating position the animal is maintained in
by the anaesthetist, in the author's opinion a flap procedure appears to be the most predictable
for their tusk extraction. Conservative treatment for abraded or infected walrus tusks is not
PK wishes to thank Andrew Greenwood and John Lewis of the International
Zoo Veterinary Group for the immobilisation and peri-operative care of the animals; Maria
Kouznetsova, Senior Veterinary Surgeon at Moscow Zoo for the long term pre- and postoperative
care of the walrus; Anna Pavlova, Head Walrus Keeper at Moscow Zoo for her exceptionally caring
and skilful management of the animals; Swissair who were very kind in carrying the team and the
equipment; and Tanya Arzhanova, Assistant to the Director of Moscow Zoo for being the magician
who made the complicated logistics of the whole procedure gel together.