Originally published in the October 2015 issue of Veterinary Practice News. Enjoyed this article? Then subscribe today!
I recently had the opportunity to teach at the AOVET craniomaxillofacial trauma and reconstruction course in Las Vegas. This is one of my favorite CE courses because it brings together veterinary dentists, veterinary surgeons, seasoned general practitioners and a human oral and maxillofacial surgeon to discuss approaches to various maxillofacial trauma cases.
We all come away from the weekend realizing there is more than one way to repair a jaw fracture. The key is having multiple tools in your armamentarium. In this article, we’ll discuss one of various methods.
Mandibular fractures in dogs and cats are most commonly due to fights with other dogs and cats, motor vehicle trauma and falls from a height. However, periodontal or endodontic disease can result in a pathologic mandibular fracture. Aggressive cancers also can cause pathologic mandibular fractures, but these are much less common than pathologic fractures due to perio/endo bone loss.
Dogs usually fracture their mandibles through the mandibular body, with common sites being mesial or distal to the mandibular first molar, or just behind the mandibular canine tooth.
When traumatized, cat mandibles usually incur a symphyseal separation or parasymphyseal fracture, which may be coupled to a caudal mandibular fracture in the area of the ramus or mandibular condyle.
What to do with teeth in the fracture line? Each case is different, and a decision needs to be made about whether the jaw fracture repair will be more successful if teeth are maintained or extracted.
If the fracture is pathologic due to periodontal/endodontic disease, the infected tooth needs to be extracted or hemisected to allow for healing. If the teeth appear to be relatively healthy on dental radiographs, they can increase stability of the fracture repair by using them as anchors in the fixation, so I tend to avoid extractions at the time of jaw fracture repair when possible.
Dr. John Lewis
Composite splint placed over the wire provides a synergy similar to reinforcement bars within concrete.
The three main goals of jaw fracture repair include obtaining a bony union, restoring normal occlusion—or restoring whatever occlusion was “normal” for the patient prior to trauma—and avoiding iatrogenic trauma to teeth during the repair process whenever possible.
One principle of fracture repair is, whenever possible, the fracture repair device should be placed on the tension surface of the bone. The tension surface of the mandible is the dorsal surface. Since the crowns of the teeth are located at the dorsal mandible, the only fracture repair technique that utilizes the tension surface is one that incorporates the teeth into the repair device.
Interdental wiring and composite splinting take advantage of the tension surface without irreversibly damaging the teeth.
Prior to placement of wire or composite, the teeth are scaled but not polished. Wire is placed in a way to incorporate at least two teeth in front of and two teeth behind the fracture site to allow the teeth to serve as anchors of stability.
The most common form of interdental wiring is called the Stout multiple loop. It is created by weaving 24-gauge wire (28-gauge in cats) between the teeth, which when tightened, pulls the dorsal surface of the mandibular fracture together.
After the wires are placed and tightened, the surfaces of the crowns are dried. Enamel etchant (40 percent phosphoric acid) is placed on the crowns and after 20 seconds it is gently rinsed off onto gauze to avoid irritation of the soft tissue from contact with this concentrated acid. The teeth are air dried with the air syringe of a dental unit, and if the etching was successful, a chalky white appearance to the enamel will be seen.
Once the teeth are etched, rinsed and dried, chemical cured composite is strategically placed over the wire in areas that won’t affect normal occlusion. The most common type is a chemical cured composite that mixes through what looks like a caulking gun used in human dentistry. (Two examples are MaxiTemp and Protemp.)
Special mixing tips allow the two separate components within the gun to be evenly mixed, and then the composite hardens within a few minutes. The material by itself is not strong enough, but it works very well to supplement interdental wire techniques and to allow for coverage of sharp portions of the wire.
The composite is built up on the lingual surface mostly with only a thin layer on the outer (vestibular) surface of the mandible since the maxillary teeth occlude lateral to the mandibular teeth. After placement of the wire and splint, the occlusion is checked to ensure there is no trauma from the opposing maxillary occlusion and to allow for full closure of the mouth.
During the procedure, the occlusion can be checked by a variety of means. The patient can be extubated and reintubated to check occlusion, but this is not the best option because the occlusion might need to be checked at multiple times during the procedure. A short endotracheal tube can be used so that when the occlusion needs to be checked, the cuff can be briefly deflated and the tube pushed behind the incisors.
Pharyngotomy intubation or temporary tracheostomy also may be done. A variation on the traditional pharyngotomy intubation technique was recently described in which the endotracheal tube exits the caudal oral cavity medial and ventral to the mandibular first molar tooth. This technique is referred to as the transmylohyoid oroendotracheal intubation technique.1
An alternate wire/splint technique has been described using circumferential wires embedded in the composite splint. This technique may not be as “stout” a repair as the Stout multiple loop, but it may prove handy in edentulous patients.
References and Recommended Reading
- Soukup JW, Snyder CJ. Transmylohyoid orotracheal intubation in surgical management of canine maxillofacial fractures: an alternative to pharyngotomy endotracheal intubation. Vet Surg 2015; 44(4): 432-436.
- Hall BP, Wiggs RB. Acrylic splint and circumferential mandibular wire for mandibular fracture repair in a dog. J Vet Dent 2005; 22(3): 170-175.
- Legendre L. Intraoral acrylic splints for maxillofacial fracture repair. J Vet Dent 2003; 20(2): 70-78.
- Niemiec BA. Intraoral acrylic splint application. J Vet Dent 2003; 20(2): 123-126.