Dental Acrylic and Circlage Wire Repair of a Mandibular Fracture in a Harbor Seal
A 30-year-old female harbor seal (Phoca vitulina) during a routine physical examination bit down upon a metal ring encircling a hoopnet and was thought to have fractured a tooth. Further evaluation via radiography and thorough oral examination under general anesthesia revealed a rostral unilateral simple complete closed fracture with mild ventral angulation of the rostral fracture segment of the left mandible caudal to the first premolar. No other abnormalities were detected except slight laxity in mandibular symphysis.
Multiple techniques are available to the veterinary surgeon to facilitate fracture repairs. Fixation may be achieved internally with bone plates, screws, stainless steel wire or externally a myriad of splint types including those made with dental acrylic. The use of intraoral acrylic splinting for this type of fracture have been well established in small animal medicine (1) and intraoral splints that are wire reinforced are stronger than those that use either alone (2). A modification of the stout multiple loop technique, interdental wiring and an intraoral splint was used successfully in this case.
The initial attempt at repair used a hybrid of interdental and interfragmentary wiring technique. 18 gauge stainless steel circlage wire was placed thru the mandible distal to the break and brought up and around the left lower canine. This failed due to inadequate rigid fixation on the 6th day.
The 73.6 kg patient was premedicated with 2.5 mg of atropine sulfate intramuscularly and 10 mg of diazepam intravenously. Subsequently she was coaxed into a custom built cylindrical anesthesia chamber where 5% isoflurance was delivered. Approximately ten minutes later she was tracheally intubated and maintained on 2 ½% isoflurane. After the teeth were cleaned and polished the loose circlage wires were removed and the site was surgically prepped and debrided. Using a procedure involving modifications of the before mentioned techniques, three 18 gauge stainless steel circlage wires, 6 total, were preplaced on either side of the fracture with the wire placed interdentally and the wires were pulled ventrally on both lingual and buccal surface around the mandible. The wire ends were then extended through the skin ventral to the mandible (Figure. 1). The wire was loosened slightly and a loop of each wire protruded approximately 5mm above the gingiva at each respective interdental placement. Interdental wiring technique was used between the lower canine to tighten up any laxity within the symphysis. After the fracture was aligned multiple layers of acrylic resin and polymethyl methacrylate (Lang Dental MFG Co, Wheeling, IL 60090 http://www.langdental.com/) were applied to a full thickness of approximately 8mm covering the teeth and wires. Within 10 minutes the dental bridge was rigid and the circlage wires were tightened in the conventional manner (Figure. 2). A burr on a high speed dental drill was used to smooth the acrylic edges. 300 mg carprofen and 150 mg of ceftiofur were given subcutaneously during the perioperature period.
Within eight hours the patient was eating normally and back in her pool. As an analgesic she was given 75mg of flunixin orally once daily for three days and 1 gram of amoxicillin twice daily for 10 days as an antibacterial. There was moderate soft tissue swelling over her left jaw for five days. Fibrin tags extended from the external wire ends for nearly three weeks.
Since the patient was eating and behaving normally six months passed before she was presented for a recheck examination that involved anesthesia and radiographs. The bridge remained stable but an ill defined lucency of the fracture site remained thus the osseous healing was deemed incomplete. The site was not inflamed and no evidence of lysis or any type of infectious process was found.
Due to the physiologic stress and logistical challenges in transporting the patient to the veterinary hospital for anesthesia and radiographs, the patient was not radiographed again for another 6 months. During that time she underwent behavioral conditioning to facilitate pool side images without sedation. The 12 month post operative films demonstrated sufficient osseous healing to be able to plan removal of the acrylic splint. The wiring and splint will be removed at approximately 13 months duration.
Dental acrylic is an inexpensive versatile product that is a good addition to the veterinary armament. It has proven its success with canine and equestrian species (3), and efficiently demonstrated its ability in this case with a large carnivore in captivity.
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Figure 1. Interdental wiring between canines for symphysis laxity stabilization. Looping of circlage wiring interdentally, running ventral down buccal and lingual surface and then out of the skin ventral to mandible. Prior to acrylic splint deposition.
Figure 2. Interdental wiring with intraoral acrylic splint, approximately 8mm thick covering the wiring and teeth of the left mandible and mandibular symphysis.
Special thanks to: Ken Lytwyn, Judy Tuttle, Marian Brown, Dr. Paul Rist DVM, Dr. Wendy Baltzer DVM, Dr. Craig Mosely DVM.
1. Holmstrom SE, et al.; Veterinary Dental Techniques--for the Small Animal Practitioner, 2nd Ed. WB Saunders. Philadelphia, 1998.
2. Kern DA, et al.; Evaluation of bending strength of five interdental fixation apparatuses applied to canine mandibles. Am J Vet Res. 54:1177, 1993.
3. Slatter, D, et al; Textbook of Small Animal Surgery, 3rd Ed. WB Saunders. Philadelphia, 2003.