Zoodent International, London, UK; Dental Consultant to the International
Zoo Veterinary Group and the Zoological Society of London
Captive sea lions between the age of 18 months and three years often
exhibit severe damage to their permanent dentition, with exposures of their pulp cavities. The
affected teeth are usually the mandibular incisors, canines and premolars. It is suspected that
the loss of tooth substance is caused through abrasion with non-dental structures. The aetiology
of the condition is unclear as some animals have been observed to play with pebbles, or chew the
structure of their pool, whilst other sea lions that show signs of severe tooth wear have not
been observed to engage in such behaviour.
Because sea lions have a long growth period before reaching maturity, and do
not have a postnatal primary dentition, the teeth of these animals, especially the roots of the
canine teeth, have a prolonged period of development. Due to this long period of development the
pulp cavities remain large and the apices stay dilated to facilitate root growth to maturity.
These large pulp cavities have the feature of maintaining the vitality of the exposed pulp
through the formation of "pulp polyps", but at the same time afford a very large space for
harbouring bacteria once the pulp tissue has become necrotic.
Pulp necrosis is followed by periapical abscess formation, where the animals
often exhibit a mandibular swelling, malaise and localised pain. The infection responds to
systemic antibiotics, but usually recurs, occasionally forming an extra-oral sinus tract at the
ventral aspect of the mandibular symphysis.
The principles of dental treatment in a veterinary environment must be
balanced between three primary objectives:
Predictability of treatment--avoiding any therapy that would not afford a very high
degree of long term success.
of therapy--not jeopardising the animal's life through an unnecessarily prolonged general
Minimal Surgical Trauma
In a captive environment these teeth do not have a functional use in the
sea lion. Also the immature state of the pulp cavities and the apical foraminae are not
commensurate with the principles of root canal treatment. At the same time pulp therapy to
maintain the vitality of these teeth cannot be considered to be predictable, and the many teeth
that are usually involved in each animal would require a very long general anaesthetic with no
long-term benefit to the animal. Therefore in these cases extraction of the damaged teeth offers
the most practical and beneficial therapy.
Extraction of the sea lion's canine teeth follows standard oral surgical
principles, but the bulbous roots require judicious removal of alveolar bone before elevation is
attempted so as not to fracture the mandible. The suture line of the mucoperiosteal flaps
frequently breaks down in the aquatic environment, but the sockets heal through secondary
intention within a short period of time. Postoperatively the animals exhibit normal feeding
behaviour and the mandibles continue to develop normally.
Sea lions in captivity very frequently develop a black coating on their
teeth. The gingival condition adjacent to these deposits is usually healthy. Histopathological
opinion is that they are most likely to be the result of the activity of oral chromogenic
bacteria and are not pathogenic to the animals.
Infrequently young animals may exhibit juvenile periodontosis, where there
is a rapid progression of periodontal disease with alveolar bone destruction, purulent gingival
discharge and tooth drifting in the jaws. There is usually a strong odour of halitosis.
Macroscopically the teeth appear healthy and clean. The cause of the syndrome is almost
certainly a host immune response, which is generally recognised as one of the most important
factors in the aetiology of periodontal disease. Dental host response is described as the
individual's resistance or susceptibility against the bacterial endotoxins being liberated from
the bacterial plaque on the teeth. Juvenile periodontosis does not respond well to antibiotic
therapy and extraction of the teeth is the treatment of choice.
Some old sea lions can exhibit pain from their canine teeth that
superficially appear healthy. Examination under sedation can reveal deep periodontal pockets
with a purulent discharge, although the teeth that have bulbous roots will still be well
retained in their sockets. A short-term course of antibiotics will control an acute phase of
infection, but in the long term extraction of the effected teeth is the treatment of choice. The
removal of these teeth can be challenging as these older animals have fully formed roots to
their canines and the consistency of the alveolar bone is much less flexible than encountered in
young animals. Equipment and instruments that match the size of the structures being worked on
should be used to speed up the operation, otherwise the length of the anaesthesia will be
PK wishes to thank John Lewis and Andrew Greenwood of the International
Zoo Veterinary Group for the immobilisation and long term veterinary care of the animals; and
the many genuinely caring marine mammal keepers for their help and enthusiasm.