Surgical extraction and oronasal fistula repair (Proceedings)

Anesthesia and pain management

While it is true that many patients with dental problems are geriatric, anesthesia is generally safe and predictable. Routine precautions should be taken with preoperative assessment, not to determine whether or not to administer anesthesia, but to determine how to do it safely. Every patient should receive intraoperative IV fluids, and be monitored with respiratory monitors, electrocardiogram, pulse oximetry, and ideally expiratory CO2. They should also have support of body temperature, ideally with forced warm air over and something under the patient.

Pre-emptive and peri-operative pain management is indicated for any oral surgery. There has been a trend over the past decade towards adding local or regional anesthetic blocks using mepivacaine, bupivocaine, or similar drugs. This is based on their use in humans. In humans, local blocks have a notoriously high failure rate and often require a second injection. Similarly, they have a variable time of onset and variable duration of action. In humans they often lose their effectiveness during a procedure and require an additional injection. These factors are not evaluated in veterinary patients where there is tremendously more anatomical variability. In addition, the injection itself causes tissue and nerve trauma, and there is a risk of a patient self-mutilating if the tongue is chewed while it is still numb. If you choose to use local blocks, do not give the injection and assume it will do the job when this is highly questionable; add some other form of predictable pain management such a pre- and intra-operative narcotics, intra-operative infusions of pain-blocking agents, and use of anti-inflammatory medications.

Surgical extraction

Pre-operative radiographs should always be made prior to extraction to identify adjacent pathology such as fractured roots, ankylosis, resorption, alveolar bone loss from periodontitis with impending mandible fracture, etc.

Many tooth extractions are relatively straightforward and can be accomplished with simple elevation and removal of the tooth with a few sutures to close. However some teeth, for example the canine and carnassial teeth, require mucogingival surgery to predictably atraumatically remove them. Some complicating factors that can convert a routine extraction into a surgical one include unusual tooth position, adjacent anatomy, compromised regional tissues, jaw anomalies, concurrent adjacent trauma, fractured root, root resorption, alveolar bone loss, communication of the alveolus with another cavity or tissue space, very young patients with fragile roots, or geriatric patients with ankylosis. Even a routine extraction can become surgical due to procedural complications such as iatrogenic root fracture or collateral trauma.

During simple extraction, a dental elevator is used to expand the periodontal ligament by gently inserting and rotating it between the root and alveolus. This stretches and tears the periodontal ligament (PDL) at the same time as it expands the alveolar bone on the opposite side of the root. In large or multi-rooted teeth, this applied force can cause trauma and bone plate fractures due to the strong attachment of large roots. Mucogingival surgery involves tissue flaps to access and remove of supportive coronal bone to assist dental elevation for PDL fatigue. Gentle but sustained elevation forces then gain the advantage, allowing the PDL to tear more easily.

Steps for surgical extraction are incision of the epithelial attachment, subperiosteal elevation of a mucogingival flap when needed, removal of alveolar bone when needed, root luxation and elevation to incise and rupture the periodontal ligament fibers and expand the alveolus, delivery of the tooth from the alveolus, alveolar curettage and flushing, osteoplasty if needed, and suturing the defect. The wound is always closed primarily; they are not left open for drainage.

The teeth generally considered to be difficult to extract are those with large roots, those with fragile peridental structures, and those with "interesting" root shapes. Most other tooth extractions are usually relatively routine.

Maxillary canine tooth

The challenge here is to gently elevate the tooth without levering the root tip through the wall of the nasal cavity. A sulcular incision is made around the tooth to incise the epithelial attachment. The easiest way to continue the horizontal incision distally is to extend it to the buccal sulcus of the first premolar and then to the distal aspect of the interproximal space between the first and second premolars where the vertical incision is made. A more elegant, but more difficult, design that avoids damage to the periodontium of the first premolar can be used in large breed dogs or when there is sufficient attached gingiva. For this approach, the horizontal incision is placed completely in the attached gingiva between the gingival margin of the first premolar and the mucogingival line. It should also extend to the level of the distal aspect of the interproximal space to facilitate closing the flap later. At the distal point of the horizontal incision a vertical releasing incision is made directed dorsally towards the apex of the canine tooth root. The root and apex can be located by feeling for the root prominence (misnamed the "jugum" in veterinary literature). Incisions are made boldly to the bone to include the periosteum. The flap is gently elevated subperiosteally with a periosteal elevator. The flap can be retracted and protected using the flat side of Pritchard PR-3 while the bone is "painted away" from the root surface using a #2 round bur in a high speed hand piece. When some buccal bone has been removed and the root has been separated mesially and distally from the bone, a dental elevator is inserted into the PDL on the palatal side of the tooth and gently rotated to force the tooth labially. The elevator can also be placed into the developed groove on the mesial and distal sides of the root and rotated in the same manner until the tooth is mobile. Forces placed using the elevators should be gentle, firm and sustained. Short-duration heavy forces allow the ligament to stretch and recover as it normally does during mastication. When the tooth is mobile, it can be grasped with a dental extraction forceps, gently rotated slightly to complete tearing of the PDL fibers, and delivered from the alveolus. The bone at the apex of the alveolus is then curetted to remove granulomatous tissue. Any sharp bone edges are smoothed with the round bur so the flap can sit atraumatically over the bone. If ridge maintenance or augmentation is desired, an osseous implant (such as Consil™) can be placed prior to closure. There should be no gaps present when the flap is placed across the defect. If the edges do not approximate without tension, then a periosteal release incision should be made on the periosteal surface of the flap close to the deep attachment prior to closure. Closure is done using 4-0 absorbable suture on a cutting needle. Gentle pressure on the flap for about twenty seconds aids in flap adaptation and blood clot removal to assist healing.

Mandibular canine tooth

Extraction of the mandibular canine tooth is similar to the maxillary except for the adjacent anatomy. In many patients the root takes up more area than the supportive bone in the rostral mandibles. If there is additional bone loss from periodontal disease, there is an increased risk of mandibular fracture during extractions. This is true for both dogs and cats. This is one reason that it is generally much better to treat fractured canine teeth with root canal treatment rather than extraction. However, they may require extraction due to hopeless periodontitis or due to complicating factors that make root canal treatment a poor option.

The horizontal incision is generally sulcular if it extends distal to the first premolar since the attached gingiva is narrow in this area. The tough fibrous attachment of the frenulum is incised with the scalpel since elevation with a periosteal elevator is difficult. The middle mental foramen can be palpated and should be identified to avoid injury to the neurovascular bundle that exits the foramen and travels rostrally. The bundle can be elevated along with the soft tissues rostral to the foramen, and the tissues caudal to the foramen can also be elevated from the mandible. However, when removing bone in the area remember that the vessels and nerve travel caudally in the bone; do not remove bone immediately caudal to the foramen. Removal of the labial bone plate to the level of the foramen is usually adequate to allow the tooth to be elevated, with the remaining apical root delivered from the alveolus. After the bone has been removad, a dental elevator is alternately inserted into the mesial, distal, and lingual periodontal ligament spaces and rotated, as described above, until the tooth is mobile enough to be easily removed with extraction forceps.

Some operators prefer a lingual approach. While it is more sparing of bone removal in the apical half of the root and it avoids the area of the mental foramen on the buccal side, it does require more bone removal in the coronal half of the root. It can also be more challenging due to the difficulty in elevating and mobilizing the soft tissues on the lingual side of the mandible compared to those on the buccal/vestibular side. However this is an issue of personal preference.

Maxillary fourth premolar

The first step during extraction of any multi-rooted tooth is to make a horizontal incision along the sulcular epithelial attachment completely around the tooth, followed by sectioning the tooth with a #2 round bur into its individual crown-root segments. The cut is started in the furcation and extended to the occlusal aspect of the crown. A dental elevator can then be used in the sectioned crown to lever the individual crown-root segments against each other. Again, theses forces need to be very gentle, but sustained. If any of the three segments begins to loosen more than the others, concentrate more on the other two in an attempt to loosen them all simultaneously, to allow continued use of each segment against the others. Do not lever against an adjacent tooth that is not going to be extracted. If the segments become mobile quickly, then they can be extracted without developing a mucogingival flap. However it is often necessary to make a flap anyway to close the defect. If the segments do not quickly loosen,. One vertical incision is made extending dorsally from the mesiobuccal line angle of the tooth. Identify the infraorbital foramen and take extreme care to avoid incision of the infraorbital vessels and nerve. The incision should either not extend dorsal to the level of the foramen, or if it does then it should remain caudal to the foramen. Once the tooth was been extracted and the alveoli curetted, then osteoplasty, flushing and closure are done in the same manner as described above. Again, a periosteal release incision is usually required to allow tension-free closure. The mesial corner of the flap is sutured to the palatal tissues that were adjacent to the palatal root. Then additional sutures are placed without tension to completely close the tissues.

Maxillary molars

These teeth can be deceptive, in that they may be mobile enough to tempt the operator to attempt a forceps extraction without sectioning the tooth. This will often result in root tip fractures of the fragile and often curved mesiobuccal and distal root tips, turning what should have been a simple extraction into a much more complicated one. Surgical retrieval of these root tips is challenging because the bone separating the root tip from the ventral orbit is sometimes only one or two millimeters thick. The root fragment can easily be pushed into the orbit, or the orbital structures can be injured. Always section the tooth even if it is mobile, be very patient, particularly with the MB and distal roots; do not try to rush the extraction or apply a heavy force against these segments, and do not use an extraction forceps to rotate the segments that have curved roots. A finger stop should be used when inserting dental elevators or luxators to prevent trauma to the globe if the instrument slips. If necessary, a buccal (vestibular) flap can be made to allow removal of buccal bone over the lateral roots and to help with closure of the defect.

Mandibular first molar

A preoperative radiograph is particularly valuable for this tooth to remind the operator to be gentle and be patient. Small breed dogs have a high tooth-to-bone ratio (i.e. very little mandibular bone) here, predisposing them to iatrogenic mandible fracture during extraction. Additional bone loss from periodontitis further weakens the mandible. The tooth is always sectioned, and the flap is made with two vertical incisions, one at the mesiobuccal line angle and one at the distobuccal line angle, and both extending ventrally past the mucogingival line. Bone is removed and the tooth extracted as above. Be aware of the position of the mandibular canal that can be between the buccal bone and the root tip in small breed dogs.

Oronasal fistula repair

Dachshunds and some other dogs that have fragile facial bones commonly have deep periodontal pockets on the palatal side of the maxillary canines that progress all the way to oronasal fistulation. Once the defect communicates with the nasal cavity, osseous regeneration surgery carries a poor prognosis. The tooth must be extracted and the defect repaired. Routine flap-repositioning surgery can fail due to thin tissue spanning a large defect, tension on the sutures, lack of bony support of the tissue flap, or an aggressive sneeze by the patient. For this reason, the author generally uses a double-flap technique.

The first flap is harvested from the palate as a split-thickness flap. A U-shaped incision is made from the mesio-palatal line angle of the defect to the disto-palatal and extending medially across the palate as far as needed to cover the defect when it is reflected, but always at least two mm short of the midline, particularly when repairing bilateral defects. The incision is made only one-to-two mm deep to avoid transecting the palatal vessels. Then a scalpel is used to develop this thin flap from the medial incision towards the tooth. If the palatal vessels are inadvertently cut, gentle firm pressure with a gauze pad for a few minutes will generally stop it. The edge of the epithelium toward the defect is left intact to act as a hinge, and the flap is flipped inverted so the previous palatal epithelium is now lining the nasal cavity. The second flap is harvested as a sliding flap from the vestibular side of the defect. It is made wider than the palatal flap with vertical incisions on each side that are vertical or very slightly divergent dorsally. These incisions are made to the bone and the flap is raised subperiosteally as a full-thickness flap. The periosteum must be horizontally incised at the dorsal extent of this flap to release it, otherwise the flap will not be mobile. This flap must sit without tension in the recipient site prior to any suturing. Be careful NOT to excise your flap when the periosteum is released! To do this, the flap is held under tension with a thumb forceps, and a scalpel is used to gently cut the periosteum. As it is cut, the flap will visibly release and muscle tissue will show through the incision. Any intact epithelium on the mesial and distal margins of the defect is removed with a scalpel or a bur. The first inverted flap is sutured with one or two stay sutures to the periosteum to temporarily hold it inverted. The second vestibular flap is positioned to cover the inverted flap and the entire donor site where the palatal flap was harvested.

This technique provides multiple advantages. There is an epithelium lining both the nasal and oral cavities, there are two layers of tissue positioned with their vascular sides towards each other to add support to the repair, and the freshly exposed tissues from the palatal donor site are an ideal recipient bed for fast healing of the repositioned second flap. Dehiscence of this type of repair is rare.

Conclusions

Surgical extractions and mucogingival surgery follows the same rules as surgery elsewhere – no tension, attention to vascular supply, and gentle handling of tissues. Differences include the moist bacterial environment of the surgery site and the excellent vascularity of most sites and speed of healing. With adequate preparation and equipment, knowledge of the anatomy, familiarity with the procedures, appropriate time scheduled, preoperative radiographs, client and patient preparation, pain management, meticulous technique, and patience, oral surgery is rewarding, fun and successful.