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Veterinarian Technician February 2013 (Vol 34, No 2)

Dental Checkup: Extraction of Fractured Teeth in Captive Sea Lions

by Kathy Istace, CVT, VTS (Dentistry)

    California sea lions (Zalophus californianus)1 are members of the order Pinnipedia.2 Pinnipeds are aquatic relatives of terrestrial members of the order Carnivora and are thought to have diverged from an arctic carnivore that belonged to the same branch of carnivores as domestic dogs.3 Pinnipeds are generally found in the polar and subpolar seas. They hunt in the sea and return to land or ice to give birth and nurse their young.3 California sea lions are faster swimmers than other sea lions, and male California sea lions, unlike other sea lions, do not have a pronounced “lion” mane.

    Glossary

    Alveolus—bone surrounding a tooth’s root(s)
    Brachyodont—pertaining to teeth with crowns that are short relative to the root length
    Carnivore—an animal whose primary food source is the flesh of other animals
    Dentition—an organism’s tooth type, position, and arrangement within the dental arch
    Diphyodont—pertaining to a set of exfoliating deciduous teeth that are replaced by a set of permanent teeth
    Family—a taxonomic category above a genus and below an order
    Order—a taxonomic category above a family and below a class

    Dentition

    Pinnipeds are carnivores. Most feed on fish and crustaceans, but some also eat birds or young seals. The normal diet of California sea lions is fish and squid.4 Pinniped dentition is optimal for grasping—rather than chewing—prey, most of which is swallowed whole. California sea lions have brachyodont, diphyodont teeth; the deciduous teeth are shed before birth and replaced with 34 permanent teeth. The dental formula3 of California sea lions is I3/2, C1/1, PM 5/5 = 34.

    Dental Trauma

    Tooth fractures and abrasions are frequently observed in captive sea lions.2 These problems may result from chewing on manmade pools or metal cage bars or from picking up objects such as stones and toys. Pulp cavity exposure can lead to infection. Extraction is often the preferred treatment because captive sea lions do not need their teeth to catch prey.

    Our Patients

    Patient A is a 15-year-old, 101-kg (222.2-lb) female (FIGURE 1). Patient B is a 3-year-old, 60-kg (132-lb) female (FIGURE 2).

    The sea lion trainers had observed that patient A was reluctant to perform her tricks, so a veterinary dentist was consulted. On examination, both sea lions had teeth with pulp cavity exposure, so extractions were recommended. Both patients were administered oral clindamycin (10 mg/kg/d) and carprofen (2 mg/kg/d) for 2 days before the dental procedure.

    Challenges

    Performing any surgical procedure on California sea lions can be difficult due to their aquatic living environment and large size. Male California sea lions grow to 2 to 2.5 m in length and 200 to 400 kg (440 to 880 lb); females can grow to 1.5 to 2 m in length and 50 to 110 kg (110 to 242 lb).5 In this case, the sea lions were housed in a marine attraction venue, so the on-site medical facilities were limited. It was impractical to transport the sea lions to a veterinary hospital, so all of the equipment (e.g., surgical table, anesthesia machine, oxygen tank, anesthetic drugs, anesthesia monitoring equipment, dental radiographic unit and the associated sensor and software, periodontal surgery instruments and materials) and personnel (e.g., marine anesthesiologist, veterinary dentist, consulting veterinarians, veterinary technician specialist in dentistry) were brought to the site to perform the dental procedures. Planning was required to determine how to get the heavy equipment into the habitat; how to proceed with anesthetic premedication, induction, maintenance, and recovery; and where to perform the dental surgeries. All personnel involved in the cases met on the morning of the surgeries to discuss these issues.

    The Oral Surgeries

    Full physical examinations were performed before administration of general anesthesia. Because collecting blood from awake sea lions is difficult, blood was collected for a complete blood count and a chemistry panel while the patients were anesthetized. Patient A was premedicated with medetomidine (0.03 mg/kg IM) and midazolam (0.15 mg/kg IM) in a squeeze cage (FIGURE 3). General anesthesia was induced using isoflurane by mask, then the patient was intubated with a #12 endotracheal tube and maintained on isoflurane and oxygen (FIGURE 4). The patient was continually monitored using a capnograph, pulse oximeter, respiratory monitor, and heart rate monitor. Because patient A was too heavy to be lifted onto the surgery table, the procedure took place on baffle boards on the floor of a pen in the sea lion habitat. Once the patient was anesthetized, a complete oral examination was performed and dental radiographs were obtained. Teeth 401, 404, and 405 were confirmed to be fractured and have pulp cavity exposure. Bupivacaine 0.5% (2 mg) was placed in the right middle mental foramen (FIGURE 5). Teeth 401, 404, and 405 were extracted, and infected tissue was debrided from the alveoli (FIGURE 6). The extraction sites were flushed with a chlorhexidine gluconate solution and closed with 4-0 absorbable monofilament suture (FIGURE 7). Atipamezole (0.15 mg/kg IM) was given postoperatively. Recovery from anesthesia was uneventful (FIGURE 8). An additional 200 mg of carprofen was given orally that evening. Clindamycin was administered orally for another 10 days, and carprofen was given orally for 3 more days.

    Patient B was premedicated with medetomidine (0.03 mg/kg IM) and midazolam (0.15 mg/kg IM) in a squeeze cage, anesthetized with isoflurane by mask, intubated with a #11 endotracheal tube, and maintained on isoflurane and oxygen. The patient was continually monitored using a capnograph, pulse oximeter, respiratory monitor, and heart rate monitor. Patient B was lifted onto the surgery table for the procedure (FIGURE 9). A complete oral examination was performed, and dental radiographs were obtained (FIGURE 10). Teeth 205, 301, 302, 304, 305, 306, 307, 308, 401, 402, 404, 405, 406, and 407 were found to be either fractured with pulp cavity exposure or abraded with pulp exposure (FIGURE 11). An infraorbital nerve block was performed on the left maxilla, and inferior alveolar blocks were performed on both mandibles using bupivacaine 0.5%. All teeth listed above were extracted, infected tissue was curetted, and the extraction sites were rinsed with a chlorhexidine gluconate solution and closed with 4-0 absorbable monofilament suture. Atipamezole (0.15 mg/kg IM) was given postoperatively. Patient B recovered smoothly from anesthesia. An additional 125 mg of carprofen was given orally that evening. Clindamycin was administered for another 10 days and carprofen for 3 more days.

    Follow-Up

    Both patients’ extraction sites have healed completely (FIGURE 12), and the sea lion trainers now brush both patients’ teeth twice daily, so further, obvious oral pathology should be noticed early (FIGURE 13).

    1. Vaughan TA, Ryan JM, Czaplewski NJ. Mammalogy. 5th ed. Sudbury, MA: Jones and Bartlett Publishers; 2011:362.

    2. Gearhart SA. Basic clinical medicine of pinnipeds. Proc North Am Vet Conf Small Anim Exotics 2006:1503-1505.

    3. University of Edinburgh. Natural History Collections: Otaridae, Phocidae and Odobenidae. www.nhc.ed.ac.uk/index.php?page=493.172.293. Accessed September 2012.

    4. Sweeney JM. Diet Estimation in California Sea Lions, Zalophus californianus. Society for Marine Mammalogy; 2011;27:4.

    5. National Oceanic and Atmospheric Administration. California Sea Lion(Zalophus californianus). www.nmfs.noaa.gov/pr/species/mammals/pinnipeds/californiasealion.htm. Accessed September 2012.

    References »

    NEXT: Educating Clients on Postoperative Care of Orthopedic Patients

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