Southern California Veterinary Dental Specialties, Dentistry, San Diego, CA, USA
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.
A surgical extraction is initiated by creating a gingival flap. This can be a horizontal flap along the arcade (an envelope flap) or a flap with vertical releasing incisions.
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 flap is created by incising the gingiva in the interdental spaces gingiva along the arcade and then releasing the tissue to or below the level of the mucogingival junction (MGJ).
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. Classically, the vertical incisions are created at the line angle of the target tooth, or one tooth mesial and distal to the target tooth. Line angles are theoretic edges of teeth. However, if there is space between the teeth, either a naturally occurring diastema or from previous extraction, the incision can be made in the space rather than carrying to a healthy tooth.
The incisions should be made slightly apically divergent. It is important that the incisions be created full thickness and in one motion. A full thickness incision is created by incising all the way to the bone, and the periosteum is thus kept with the flap. 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 1/2 for maxillary teeth. This should only be performed on the buccal side. If this does not allow for extraction after a decent amount of time, more can be removed. 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 (and radiographic proof obtained) the alveolar bone should be smoothed before closure. Closure is initiated with a procedure called fenestrating the periosteum. The periosteum is a very thin fibrous tissue which attaches the buccal mucosa to the underlying bone. 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 very flexible and will stretch to cover large defects. Consequently, incising the periosteum takes advantage of this attribute. The fenestration should be performed at the base of the flap, and must be very shallow as the periosteum is very thin. This step requires careful attention, as to not cut through or cut off the entire flap. This can be performed with a scalpel blade, however, a LaGrange scissor allows superior control.
After fenestration, the flap should stay in the 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, as well as providing sufficient tissue for closure. However, an envelope flap is sufficient for small and toy breed dogs, as well as cats.
Full flaps are created by making full thickness, slightly divergent incisions at the mesial and distal aspect of the tooth. These incisions should be carried to a point a little apical to the mucogingival junction. Be careful to avoid cutting the infraorbital bundle as it exits the foramen above the third premolar. The flap is then gently elevated with a periosteal elevator.
Following flap creation, buccal bone is removed to a point approximately 1/2 the length of the root. Next, the tooth is sectioned. The mesial roots are separated from the distal by starting at the furcation and cutting coronally. Next, the mesial roots are separated by sectioning in the depression between the palatal and buccal roots. Another way to visualize this is to follow the ridge on the mesial aspect of the tooth. When performing this step, a common mistake is not fully sectioning the tooth. 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.
Following these steps, extraction proceeds as described in the last lecture for single rooted teeth.
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. This is much more likely in small and toy breed dogs, because the roots of these teeth are much larger in proportion to the mandible than large breeds. Bony resorption can significantly weaken the bone and predispose to a mandibular fracture. It is advised to warn clients of these potential complications. Dental radiographs are required to demonstrate the level of remaining bone. Finally, consider referral for these extractions (or possible root canal therapy).
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. 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. An exception exists if the first premolar is very close to the canine. In this case, carrying the horizontal component to the mesial line angle of the second premolar is recommended. This is to allow sufficient exposure for bone removal, as the root curves back to over the second premolar.
If a mesial incision is performed, it should be in the diastema between the canine and third incisor. Classically it was made at the line angle of the canine or third incisor. However, in this author’s opinion, the mesial line angle of the canine does not allow sufficient exposure and there is no reason to risk damaging the third incisor and increase surgical trauma. It is critical to fully incise the interdental gingiva to avoid tearing the flap. This is particularly challenging in the area mesial to the canine. Make sure to cut all the way to the bone. 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 1/2 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.
After the bone removal, elevate the tooth carefully. Do not torque the crown too much buccally as this will lever the apex into the nasal cavity. Once the tooth is elevated to a point of being very loose, it can be carefully extracted with forceps. The bone is then smoothed with a coarse diamond bur.
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. It is critically important to relieve all tension if an oronasal fistula is present. Close the flap starting at the corners to avoid having to start over if it does not close correctly.
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 either during or after surgery. This tooth often holds the tongue in, and therefore it is not uncommon for the tongue to hang out following the extraction. Finally, the patient loses the function of the tooth. Therefore, it is strongly recommended to avoid extraction of this tooth. Referral for root canal therapy is a much better solution, if possible.
Some authors recommend a lingual approach to this extraction since less bone needs to be removed as to tooth curves lingual apically. However, this author prefers the standard buccal approach. This is because superior exposure is afforded and the flexible buccal mucosa allows for easier closure.
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, but be careful with creating a larger flap or taking more bone as the mental nerve and artery exit approximately 3/4 of the way down the root. 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 straight forward. 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. Depending on the size and location of the fistula as well as presence of the offending tooth, a horizontal interdental incision may also be necessary for successful repair. 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.
Incisions are created with a number 15 or 11 scalpel blade. As described previously, the vertical incision(s) were classically started at the line angle of the teeth. A line angle is a theoretic corner of a tooth. When repairing an ONF associated with a maxillary canine tooth, the distal incision is made at the mesial line angle of the first premolar, and the mesial incision is started at the mesial line angle of the canine (if present). However, it is not necessary to cut over to a line angle if there is a diastema. If the tooth is already absent, the incisions are made at the mesial and distal edges of the fistula.
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 pedicle flap. It is important to choose the location of the incisions to ensure that sutured margins will have adequate bony support and will not lie over a defect.
The mucogingival flap is gently elevated off the bone using a periosteal elevator.
Approximately 2–3 mm of palatal mucosa is also gently elevated/lifted off the palatal bone so that fresh epithelial edges are created. 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.
A coarse diamond bur on a high-speed handpiece is used to smooth the edges of the remaining maxillary bone (if necessary) and to remove any epithelial remnants between the fistula and the nasal cavity.
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.
1. Niemiec BA. Dental Extractions Made Easier. Tustin, CA: Practical Veterinary Publishing. www.practicalvetpublishing.com. (VIN editor: Link not accessible).