In treating fractured teeth in carnivores and omnivores, the decision-making process is a straight forward one; it must be determined if the tooth is required for function (i.e., biting/feeding, tongue retention, or identity). The teeth that are most often identified with being functionally necessary are the canines and first molars. Root canal therapy on these teeth has been, and continues to be, a vital part of the treatment for the animal who has fractured its tooth/teeth; however, root canal therapy by itself far too frequently leads to an unsatisfactory end result. Retaining the tooth in a nonfunctional state or worse, failure of the treatment due to vertical fracture of the tooth and/or coronal leaking of the access restoration leading to reinfection of the periapical area, does not serve our patients well. However, exposing our patients to a second ‘knock down’ to cement a cast restoration is hardly medically or fiscally responsible.

With a bit of prior planning, good teamwork, and the use of some of our newer dental laboratory materials, it is possible to provide a very high level of service to our patients with a reduction of the risks associated with that second appointment.

This paper will discuss the techniques involved in root canal therapy from a dentist’s perspective and provide a “cookbook” outline of the complete procedure from start to finish in the context of the case study that led me to design this timetable.

The patient is a seven-year-old male American black bear (Ursus americanus) at the Heritage Park Zoo in Prescott, Arizona. His zookeepers noticed a change in the appearance of his maxillary left canine tooth. His weight was estimated at 450 pounds (200 kg). He had been observed chewing on the chain link fence of his enclosure in the past. The patient's diet consists of pig chow, senior dog food (kibble), omnivore biscuits, carrots, and fruits of various kinds. Rick Smith, DVM, along with his team, would lead the procedure and be responsible for the sedation and well-being of Shash. I was contacted and asked to consult regarding treatment options.

Patient was anesthetized for the initial evaluation with Telazol IM (5.5 mg/kg) administered with a jab stick. This did not achieve adequate anesthesia, so our weight estimation was increased to 475–500 pounds (215–227 kg) and a second dose of Telazol (2.2 mg/kg) was given about 30 minutes after initial dose.

Once the bear had been confirmed ‘down’, visual examination revealed a compound fracture of the maxillary left canine. More than 10 mm of the incisal tip was missing, fractured horizontally, supragingivally, exposing the pulp. An additional portion of the tooth (5x10x2+ mm thick piece) was fractured vertically on the buccal. This fractured piece extended more than 5 mm subgingivally and was still attached to the gingiva in that area. It was this aspect of the fracture that prompted me to treatment plan a cast crown for restoration of this tooth. Preoperative radiographs were taken at this time.

The discussion of the treatment process that ensued highlighted the concerns of the zoo director, Dan Mazur, and Dr. Smith in having to re-sedate the bear, as well as the concerns of the handlers and myself, that, because of the nature of the fracture and the probable source, refracturing the tooth (possibly irreparably) was also something to be avoided.

The decision was made to proceed with the treatment recommended and schedule the second appointment three to four weeks later for maximum safety during sedation. The second anesthetic procedure was Telazol (7 mg/kg) again administered IM via jab stick. The initial dose gave good anesthetic depth but was supplemented at 45 minutes with Telazol (3 mg/kg). Recovery from both procedures was uneventful. Now, 16+ months later, the crown is present and functioning, the periapical lesion is resolved, and patient is as good as new.

A variety of factors required that the optimum treatment for Shash be accomplished in two appointments; however, the concerns expressed by all concerned and in discussions with other practitioners regarding their ‘less than optimal results’, lead me to develop this treatment schedule which allows for complete treatment in one appointment/sedation.

The following is a “cookbook” list of materials and a timetable that I, as a general dentist and lab owner, know is possible to achieve. The key to doing this type of service is establishing yourself with a dental laboratory close to your office or zoo beforehand and letting them know what you need time-wise. The following is a list of the actual materials that I use. There are other materials that may allow you to achieve the same results. I do not have any sort of financial interest in any of the companies represented here.

Materials

• Impression materials
  Correct Plus VPS (Hydrophilic impression material)
  Pentron Corp., P.O. Box 724, Wallingford, CT 06492, 800-551-0283
• Impression trays
  Cat and Dog Impression Trays
  Dr. Shipp’s Laboratories, 351 N. Foothill Road, Beverly Hills, CA 90210, 800-442-0107
• Casting Investment
  “1700” and Die Stone: Die Master Die Stone
  Talladium, Inc., 25031 Anza Drive, Valencia, CA 91354, 800-221-6449
• Bonded Resin Cement
  Panavia
  J. Morita USA, Inc., 9 Mason, Irvine, CA 92618, 888-566-7482
• Endodontic Lubricant
  RC Prep
  Sultan Chemists
• Endodontic Sealer
  Vitapex DiaDent Japan or Endo Rez Ultradent Products, Inc.
  505 West 10200 South, South Jordan, UT 84095, 800-552-5512
• Casting Alloy
  NPG+2
  AalbaDent, Inc., 400 Watt Drive Cordelia, CA 94585, 800-227-1332
• Laboratory vibrator, electric hand piece, apex locator, assorted burs, sodium hypochlorite 5.25%, irrigating syringe and needles, gutta percha points, paper points, absolute alcohol

Timetable

• 0:00—Start.
  Sedation is confirmed.
  Exam and Evaluation.
  Evaluate tooth for periodontal health, trans-illuminate for possible vertical fractures, pre-op x-rays. Do not wait for X-rays to develop!
• 0:05—Assuming all is favorable for keeping the tooth (i.e., [a] clinical crown is 2–3 mm minimum, [b] pulp is exposed but no vertical fracture, [c] tooth is ‘necessary’) then immediately start preparing the tooth for crown utilizing a circumferential chamfer preparation. Attempt parallel axial walls, a uniform reduction of remaining tooth structure and margins at or very slightly below gingival contour. For domesticated animals 0.5–0.75 mm is the minimum reduction. For the large or exotic animals, a 1.5–2.0 mm is the minimum reduction. Avoid trauma to the gingiva. The resultant bleeding/oozing will only complicate the impression. If, however, it is unavoidable, Visine works great as a hemostatic agent.
• 0:15—Wash and dry tooth/prep. Make impression in rigid tray (upper and lower) with VPS impression material. Mix quick-set die stone and vibrate into the prep impression. Mix the lab stone and vibrate into the opposing impression.
• 0:25—Transport impression to dental lab. This can be either your staff or the laboratory’s staff.
• 0:30—Perform access with #6, 8, or 10 round bur. Review pre-op x-ray. Determine test file length using #15 file and apex locator. Take test-file verification x-ray. Process. Instrument pulp out of canal using RIC Prep, alternating with hypochlorite rinses in a crown down approach.
  (The * instructions are for the Laboratory)
• 0:40*—Arrive at dental lab. Separate models from impressions. Pindex die for crown and pour base for die with quick set stone.
• 0:45*—Cut out die and trim. Apply Die lube and mount models.
• 1:00—If post is needed to obtain adequate retention for crown, prepare post space. (Remember posts do not reinforce the tooth and are only used to provide additional retention for crown.)
• 1:00*—Wax up crown. Remember only primates have lateral excursions and then, only minor excursions. Must be waxed to a more scissor-like up and down occlusion than humans. Sprue into crucible former.
• 1:10*—Invest wax pattern with “1700” investment.
• 1:30—Final rinse of canal with hypochlorite. Dry canal with absolute alcohol and paper points. Fit master gutta percha cone. Mix endodontic sealer and introduce into canal. Obturate. Cement post or fill access with amalgam. Clean area. If necessary, Prophylaxis can be done now.
• 1:25*—Put investment into hot oven, burn out 30 minutes.
• 1:55*—Cast, divest, polish, and provide sandblasted finish to interior of crown.
• 2:00*—Transport crown back to patient.
• 2:10-15—Crown arrives at Patient.
• 2:20—Try in crown, etch and prime tooth with Panavia primer. Mix paste/paste, load crown, and seat. Apply air inhibitor. (Panavia sets very quickly in anaerobic environment.)
• 2:30—Clean up. Make patient comfortable. Finished.