Dental and Oral Surgery
Gregg DuPont, DVM, Fellow AVD, Diplomate AVDC
This session will concentrate on three of the most common of the many different types of dental and oral surgery; mandibular fracture repair, surgical extraction, and oro-nasal fistula repair.
The most common injury after oral trauma is fractured teeth that require either root canal treatment or extraction, depending on the importance of the tooth and the severity of the injury. Other injuries include fractures of the maxilla or the mandible, soft tissue injuries of the tongue, the lips, palate, or gingiva. Fracture and soft tissue repair of most oral structures is quite routine. However, repair of the mandible presents several challenges.
Mandibular fracture repair
Mandibular fracture is a relatively common injury. The presence of tooth roots occupying the body of the fractured bone, and no appreciable marrow space, complicates surgical repair. Consequently, most fractures in the horizontal ramus do not lend themselves to plates or pins. Attempts to use plates or pins pose a high risk of damaging the roots, requiring eventual endodontic treatment or extraction. Another complicating factor is the importance of maintaining a functional occlusion.
When a mandibular fracture has healthy teeth both mesial and distal to it (i.e. a fracture anywhere forward of the lower first molars), the teeth can be used as part of a solid external fixator. An acrylic or composite resin splint applied directly to the crowns of the teeth provides extremely solid fixation along the tension side of the fractured bone.
Do not extract any teeth that are firmly in position, regardless of their proximity to the fracture. They can contribute to the repair, and future root canal treatment or extraction can be done as needed after the jaw has healed. The first step is to place interdental wires to stabilize the mandible, ideally including a minimum of two teeth on each side of the fracture. The wiring serves to hold the fragments in alignment and the teeth in correct occlusion while making the splint. There are multiple wiring techniques that can be used; a simple and very adequate technique is Stout’s multiple loop wiring technique (See figure). The loops of the wires should be bent up into the interproximal areas to avoid interfering with occlusion against the insides of the upper teeth when the mouth is closed. The next step is to close soft tissue defects using an absorbable suture material. Then place either acrylic (i.e. Jet Dental Repair Acrylic, Lang Dental Manufacturing Co.) or composite (i.e. Protemp Garant, ESPE) over the tooth crowns, incorporating the wires. The final step is to remove any acrylic or composite that would interfere with occlusion when the mouth is closed, and to smooth any areas that would be sharp or uncomfortable to the tongue, lips, or cheeks.
When deciding whether to use acrylic or composite resin, each of the materials has advantages and disadvantages and may be better suited to specific cases and patients. Acrylic is inexpensive, and is resistant to cracks or fractures. The best placement method is to layer it onto the teeth, alternately placing powder and a drop of liquid as the splint is built up. This method avoids high heat build-up from a large mass polymerizing at once. It also allows the fluid plastic to conform perfectly to the teeth and wire, creating perfect mechanical retention. The disadvantage of the acrylic is the time it takes to apply, set, adjust and smooth the splint. Composite resin, on the other hand, is very fast and easy to apply when using an auto-mix product. These are designed for human dental work to quickly make a temporary crown while waiting for the lab to craft the final crown. The material is extruded from an application gun onto the teeth and wires. The set is so fast that the animal can be extubated during application so the mouth can be closed and the teeth occluded as it hardens, thereby preventing any interference of the final splint. The disadvantages are the cost of the materials, and the brittle nature of the material that can be more easily fractured by external forces. On the positive side, this brittle nature makes the splint much easier to remove than the acrylic splints.
The splints are removed in 4 to 5 weeks using a combination of chipping (careful for the teeth!) and high speed and low speed burs.
This method provides solid fixation with good occlusion, and is non-invasive to minimize further trauma to the surrounding tissues.
Tooth elevation and simple extraction of periodontally compromised teeth, and frequently of healthy single root teeth, is often simple and routine. However, multi-rooted teeth and some single-rooted teeth require cutting of tooth and/or supporting tissues. Multi-rooted teeth often have divergent roots, or root tips that curve towards each other. Also, it is difficult, and sometimes not possible, to elevate on the side of a root toward a furcation unless the tooth is first sectioned. For roots that are long and narrow, or very large, a surgical approach provides access and a safer root elevation by removing supportive bone in a controlled manner rather than traumatizing or fracturing bone plates as a result of applying excessive force. Extraction should always be an exercise in patience, not force.
Multi-rooted teeth should always be sectioned, cutting the crown through its furcations to separate it into two or three single-rooted teeth, as the first step in extraction. At this point, gentle dental elevation is attempted. If the individual tooth roots do not quickly begin to loosen, then a surgical approach is indicated. Generally, whenever the operator feels that an extraction is requiring either too much time or too much force, then it is time to remove some supportive bone.
Ideally, when fashioning a muco-gingival flap for surgical extraction, a horizontal marginal incision and one vertical releasing incision is sufficient. For canine teeth, the vertical releasing incision is made at the distal aspect of the interproximal space between the first and second premolars. For upper 4th premolars, the vertical releasing incision is placed at the mesial aspect of the interproximal space between the 3rd and 4th premolars. Vertical releasing incisions should always be …. vertical. Do not angle incisons to make a “wide-based” flap, since this will cut across blood vessels in the mucosa. Buccal bone is then removed over the root, and the tooth gently elevated from the alveolus. The incision is closed with a simple interrupted suture pattern of 4-0 absorbable suture. Gut works well in the mouth due to knot security, short duration, and soft nature for comfort. If a root is fractured during an extraction attempt, it must be retrieved if the tooth is endodontically involved. For this, a surgical length bur is used to bur a trough around the root tip. The trough provides purchase for a dental elevator, and the root tip is delivered from the alveolus. Be aware of the regional anatomy; the infra-orbital vessels and nerve pass through the canal that is in the bone close to the root tips of the mesio-buccal and palatal roots of the upper 4th premolar. Aggressive bone removal in this area could result in excessive hemorrhage if these vessels are damaged. Similarly, the inferior alveolar vessels exit the mental foramen close to the root tip of the lower canine tooth. Isolate and protect these structures. Another caution – always take pre-operative radiographs to discover complicating conditions such as root fractures, compromised regional bone, tumors, etc. Take extreme care when extracting the lower first molar; the mandibular bone may be severely weakened in this area if there were chronic periodontitis, increasing the risk of iatrogenic mandibular fracture.
Oro-nasal fistula repair
Deep periodontal pockets palatal to the maxillary canine teeth, left untreated, frequently extend through the palatal alveolar bone plate and into the nasal cavity. The resultant oro-nasal fistula is lined with epithelium, and forms a chronic communication between the oral and nasal cavities. Food material and oral bacteria then have direct access to the nasal cavity, resulting in sneezing and chronic rhinitis. Surgical repair of the defect is often complicated by loss of gingival tissue on the buccal aspect, as well as the lack of solid support of the surgical flap covering the defect. With single-flap techniques, a good strong sneeze by the patient could open a surgical site and delay or prevent healing. A double-flap repair technique results in a more predictable outcome by providing a large recipient bed for the relocated flap, providing support for the suspended tissue, and providing an epithelial surface toward the nasal cavity to assist healing.
First, the margins of the fistula are de-epithelialized. This can be accomplished using a high-speed long diamond bur, or using a scalpel blade to scrape the epithelium. A split-thickness palatal flap is raised from almost mid-palate extending to the palatal margin of the defect, with a width equal or greater than the width of the defect. The flap is developed thin enough to avoid damaging the palatine vessels underneath. Once lateral to these, it can be deepened right to the bone, but stop short of the defect margin; this edge of the flap remains attached. This attachment acts as a hinge, and the flap is inverted into the defect. The inverted flap provides an epithelium to line the nasal cavity. Two sutures are placed from each corner of the flap to adjacent periosteum or other tissue, to gently hold the flap inverted during surgery. Then a full-thickness muco-gingival flap is raised subperiosteally extending dorsally from the labial aspect of the defect, with mesial and distal vertical incisions extending straight upwards. The width of this flap should be slightly wider than the palatal flap. The periosteum must be incised at the apical extent of the flap to release it, otherwise it will not be mobile enough to be palatally repositioned without tension. This flap is then placed all the way over the defect, extending beyond it to cover the donor site of the palatal flap. The palatal flap donor site provides an excellent recipient site for the repositioned labial flap due to the excellent blood supply and solid bony support.
Surgery in the oral cavity heals quickly and well, as long as tissue trauma is avoided, circulation is not compromised, and wounds are closed without tension. The excellent blood supply in the area can complicate the surgery, but contributes to an outstanding ability to heal.