National Pet Dental Health Month is here, which means it’s a great time to promote dental health and encourage dental exams and cleanings. However, with every thorough oral exam, you never know what challenges may present. Will it be a straightforward prophylaxis or advanced periodontal disease with multiple extractions? No matter your question or dilemma, our dentistry team is always available and glad to help. We also welcome any topics you would like to have covered in the future.
One common dilemma we frequently receive questions about are oronasal fistulas: how to avoid them, and how to treat them. Oronasal fistula [ONF] (or oroantral fistula if it connects with the maxillary recess) is a common sequela to advanced periodontal disease, palatal trauma, or following extractions (Figure 1). If basic tenets of oral surgery are followed, repair can be simple and serious complications can be avoided.
Figure 1. Pre-operative picture of a geriatric dachshund that had both maxillary canines extracted due to periodontal disease. Ten months later, the bilateral ONFs were still present.
This is by far the most important rule in oral surgery. If there is any tension on your closure, it will almost always fail. There are two ways to avoid tension for ONF repair. The first is to make a gingival flap. Even if the extraction didn’t require a flap (such as in cases of advanced periodontal disease, commonly on the maxillary canines), if there is communication with the nasal cavity, the site will not heal or granulate in on its own. When such a large tooth is removed, you simply can’t just oppose the sides and hope for the best. Divergent vertical incisions should be made at the mesial and distal aspects of the defect; the base of the flap should be 1.5-2X the width of the defect to provide good blood supply (Figure 2). The second way to extend the reach of your gingival flap is to fenestrate the periosteum. By cutting the fibrous periosteal layer of your full-thickness mucogingival flap, you allow the much more pliable mucosa to stretch further, thus creating a tension free flap. This technique is easy to practice on cadavers and will greatly improve the ease and success of your gingival flaps even for basic extractions. The resulting flap should remain in the desired position even without sutures; this is how you can test if there is any tension at all on your incision.
Figure 2. Illustration of margins for gingival flap created for closure. The buccal wound edge would also be debrided to allow fresh margins for closure.
While this is often not possible with larger ONFs, it is ideal to place your incision over bone to avoid excess tension and motion. If the suture line is not over bone, you can get a “trampoline” effect each time the patient breathes in and out, putting stress on your closure. If there is enough bone in the palate to achieve this, you can debride the soft tissue and move your incision towards midline to close over bone. However, it is more important to close without tension, so take care when removing healthy tissue.
By definition, a fistula is an epithelial-lined connection between two organs or cavities. In cases of ONF, the body has laid down epithelial cells along the edges of the defect. Even if you make a gingival flap, if you do not debride the palatal aspect of the defect and simply close to that tissue, the repair is likely to fail. It is important to debride all edges of the defect prior to closure (Figure 3). Remember that in doing so your ONF may get significantly larger and require a bigger flap to close without tension.
Figure 3. Illustration of palatal aspect of defect where epithelialization will prohibit wound healing unless it is fully debrided.
Postoperative care is essential to successful ONF repair. Elizabethan collars are important; a quick paw to the face or rub of the nose on the floor is enough to disrupt your careful closure. Exercise restriction can be helpful to avoid excessive stress on the incision from the trampoline effect. Softened food is critical. Chews and toys should be avoided until the surgical site is fully healed. Advise the client that mild epistaxis may be noted for 48-72 hours following surgery. Also, in some cases the lip may be tight or even roll in; this often improves over time, although it should be monitored carefully for any trauma from the opposing mandibular teeth. At the 2 week recheck, things should be completely healed. If they are not, it may be necessary to revise the repair.
Due to the importance of Rule #1, with each repeated repair attempt the difficulty and the risk of failure increase significantly. However, by following these basic rules, many defects can be closed successfully (Figure 4). Should you have any questions following the first attempt, do not hesitate to give us a call. We are always happy to help.
Figure 4. Postoperative picture of the ONF repair.
As always, communication is key; so discussing these risks with your clients before surgery can smooth the path later, even if complications arise. Be prepared for ONF repair with any maxillary canine extraction and document the case with dental charts, pictures, and dental radiographs if possible.
For additional resources for you, your team, and your clients, visit the AVMA’s Pet Dental Health toolkit (avma.org), the American Veterinary Dental College (avdc.org), or the Veterinary Oral Health Council (vohc.org).
Figures 5-7. Pre and postoperative pictures of the contralateral side in the same patient. Note that the flap on the right side was smaller, as the defect was also smaller. Healing was complete at the two week recheck.
