Oronasal or oroantral fistula is a communication from the oral cavity to the nasal cavity or sinuses. Causes of fistula formation include overly aggressive extraction technique (penetration of extraction instruments through the alveolar bone), periodontal disease (especially on the palatal aspect of the maxillary canine tooth), tipping of the crown of the maxillary canine tooth during extraction buccally resulting in the apex of the root penetrating into the nasal cavity and neoplasia. Fistula formation secondary to neoplasia is more involved and surgical intervention will not be discussed in this paper.
General surgical principles in mucogingival flap surgery are: development of an appropriately sized flap, taking large bites with your suture, do not suture over the defect and the flap must be tension free.
For most fistula repairs, a single mucogingival flap is sufficient. (Figure 1) The margins of the fistula are debrided, and a mucogingival flap is elevated with diverging vertical releasing incisions starting at the mesial and distal aspect of the fistula. (Figure 2) The incisions extend apically into the buccal mucosa. (Figure 3) The gingiva and periosteum are gently elevated from the underlying bone with a periosteal elevator. The periosteum is incised with a new scalpel blade at the base of the flap to allow the flap to stretch. (Figure 3) After making sure all edges to be sutured are freshened to bleeding tissue, the flap is sutured with an absorbable suture in a simple interrupted pattern. (Figure 4)
For chronic fistulas, or fistulas with prior failed surgical attempts, a double flap technique can be used. With this technique, a mucogingival flap is elevated as above. The second flap is elevated from the palatal tissue. Mesial and distal incisions are made in the palatal mucosa and connected. (Figure 5) It is very important to accurately measure the distance needed for the flap as the palatal tissue does not stretch. If your flap is too short, there is no second chance. The full thickness flap is elevated and rotated back over the defect and sutured. (Figures 6,7) If there is insufficient connective tissue to suture to, holes can be placed in the bone surrounding the defect with an IM pin and the suture placed through the holes. The mucogingival flap is stretched and sutured over the inverted palatal flap and the donor site. (Figure 8)
Post-operative care includes antibiotics if indicated and analgesics. Soft food should be fed and chew toys withheld for 14 days. (Figure 9)