B. Niemiec1; K. Stewart2
Challenging extractions are best performed via a surgical approach. Canine and carnassial (maxillary fourth premolar and mandibular first molar) teeth are typically considered “difficult.” However, it is also beneficial for teeth with root malformations or pathology (i.e., ankyloses) and retained roots. A surgical approach allows the practitioner to remove buccal cortical bone, promoting an easier extraction process.
Envelope flaps are created by incising the interdental gingiva and then releasing the gingival attachment with a periosteal elevator along the arcade including one to several teeth on either side of the tooth or teeth to be extracted. The advantages to this flap are:
- Decreased surgical time
- Blood supply is not interrupted
- Less suturing
- Less chance of dehiscence
The more commonly used flap includes one or two vertical releasing incisions. This method allows for a much larger flap to be created, which (if handled properly) will increase the defects which can be covered. The incisions should be made slightly apically divergent. Once created, the entire flap is gently reflected with a periosteal elevator. Care must be taken not to tear the flap, especially at the muco-gingival junction.
Following flap elevation, buccal bone can be removed. Again, this author favors a cross cut taper fissure bur. The amount is controversial, with some dentists removing the entire buccal covering. However, this author prefers to maintain as much as possible and starts by removing 1/3 of the root length of bone on the mandible and ½ for maxillary teeth. If ankylosis is present, a significant amount of bone removal may be required.
Following bone removal, multirooted teeth should be sectioned. Then follow the steps outlined for single root extractions for each piece. After the roots are removed the alveolar bone should be smoothed before closure.
Closure is initiated with a procedure called fenestrating the periosteum. Since the periosteum is fibrotic, it is inflexible and will interfere with the ability to close the defect without tension. The buccal mucosa however, is flexible and will stretch to cover large defects.
The fenestration should be performed at the base of the flap. This can be performed with a scalpel blade, however a LaGrange scissor allows superior control.
After fenestration, the flap should stay in desired position without sutures. If this is not the case, then tension is still present and further release is necessary prior to closure. Once the release is accomplished, the flap is sutured.
Maxillary Fourth Premolar
The first step when extracting this tooth is to create a gingival flap. Classically this is a full flap with one or two vertical releasing incisors. This will allow good exposure, However, an envelope flap is sufficient for small and toy breed dogs, as well as cats.
Following flap creation, buccal bone is removed to a point approximately ½ the length of the root. Next, the tooth is sectioned. The furcation is fairly deep, so make sure that you have it fully sectioned by placing an elevator between the teeth and twisting gently. If fully sectioned, the pieces will move opposite each other easily.
Mandibular First Molar
In canine patients, these extractions are further complicated by a groove on the distal aspect of the mesial root. In addition, the mesial root is often curved. Finally, in small breed dogs, there is commonly a significant hook at the apex. Moreover, this tooth is the most common place for an iatrogenic mandibular fracture and it is possible to damage the mandibular nerve and vessels.
The first step when extracting this tooth is to create a gingival flap. Classically this is was full flap with one or two vertical releasing incisors. However, this author finds that an envelope flap is sufficient in virtually all cases. Following flap creation, buccal bone is removed. Next, the tooth is sectioned and the extraction proceeds as for single rooted teeth.
Maxillary canines are a very challenging extraction due to the significant length of the root. In addition, the very thin (less than 1 mm) plate of bone between the root and the nasal cavity often results in the creation of an oronasal fistula.
Vertical incisions are usually necessary for exposure and closure. At least a distal incision should be performed, and performing a mesial and distal incision will allow for increased tissue for closure.
The distal releasing incision is typically created at the mesial line angle of the first premolar. This is to allow sufficient exposure for bone removal, as the root curves back to over the second premolar. Following the creation of the vertical incisions, the flap is carefully elevated. If it is not elevating fairly easily, ensure that the interdental tissue is fully incised.
Once the flap is raised, approximately ½ of the buccal bone is removed. Make sure to remove some of the mesial and distal bone as the tooth widens just under the alveolar margin. Once the tooth is elevated to a point of being very loose, it can be carefully extracted with forceps.
Closure is initiated with fenestration of the periosteum. When this is performed the tissue should stay in position over the defect. If it does not, tension is present and the flap will dehisce.
These are quite simply the most difficult extraction in veterinary dentistry. This is due to the length and curve of the root, the hardness of the mandible, and the minimal bone near the apex. Furthermore, extraction of this tooth will greatly weaken the jaw and further predispose the patient to an iatrogenic fracture.
The flap for this extraction is generally triangular with just one distal vertical flap. A horizontal incision is created along the arcade to the mesial line angle of the first premolar. Then a distally divergent vertical incision is created. Next, the flap is carefully elevated and the buccal bone is removed to a point about 1/3 of the way down the root. More bone can be removed if necessary. The tooth is then carefully elevated and extracted. Debridement and closure is as above.
Extraction of Retained Roots
Root fracture is a very common problem in veterinary dentistry. While it seems that removal of retained root tips is a daunting task, with proper technique and training it can be fairly straightforward. The first step is to create a gingival flap. Depending on the anticipated amount of exposure necessary to retrieve the fragments, this can either be an envelope flap or a full flap with one or two vertical releasing incisions.
Following flap creation, buccal cortical bone is removed with a carbide bur to a point somewhat below the most coronal aspect of the remaining root. If necessary, the bone can be removed 360 degrees around the tooth, but this author tries to avoid this aggressive approach.
Once the root(s) can be visualized, careful elevation with small, sharp elevators is initiated. Once the tooth is mobile, it can be extracted normally. After radiographic confirmation that the tooth is fully extracted, the bone is smoothed and the defect closed.
Oronasal Fistula Repair
In most cases, the single layer mucogingival flap technique is sufficient to repair ONFs, especially when done correctly the first time. This is the most common surgical treatment used to repair ONFs and therefore will be presented here.
The single layer mucogingival flap is created with either one or two vertical incisions. Proper design of the mucogingival flap will allow maximum exposure of the area for extraction of the tooth (if necessary), debridement of the fistula, and critically important tension-free closure.
When making flap incisions, adequate pressure should be placed to ensure full thickness of the soft tissue is incised down to the bone. Any vertical incisions should be created slightly divergent as they proceed apically. Divergent incisions allow for adequate blood supply for the newly created flap.
The mucogingival flap is gently elevated off the bone using a periosteal elevator. Any margins of the flap associated with the oronasal fistula should be debrided using a LaGrange scissors or coarse diamond bur to remove 1–2 mm of tissue, leaving fresh epithelial edges. As with any closure in the oral cavity, the key to success is to ensure there is no tension on the incision line.
Fenestration of the inelastic periosteum (see previous section on surgical extractions) is performed to increase the mobility of the flap and allow for a tension free closure. This is accomplished by a combination of sharp and blunt dissection with a LaGrange scissors to ensure the overlying mucosa is not damaged.
The gingival flap is then placed over the defect so that it remains in position without being held. Once this is accomplished (i.e., no tension is present), the flap is ready to be sutured into place.