Oroantral Fistula

Oroantral fistula is a persistent, epithelialised tract between the oral cavity and the maxillary sinus, most often after extraction of an upper molar or premolar. A communication that persists for more than about 3 weeks is usually considered a fistula, and it does not heal spontaneously.

It is typically the sequel of an untreated or failed acute communication, and chronic maxillary sinusitis is frequently present. Other causes are cyst or tumour surgery, trauma, implant failure, osteonecrosis, radiotherapy and infection.

Pathophysiology. The roots of maxillary molars lie close to the sinus floor. After a communication opens, oral bacteria and food enter the sinus, causing infection that prevents closure, and epithelium grows along the tract.

A mature fistula is lined by oral and sinus epithelium and stays patent as long as infection and tension persist.

Fluid or food passing into the nose, air escape from the mouth to the nose, hypernasal speech, difficulty drinking through a straw or smoking, a foul taste and smell, and signs of chronic sinusitis: unilateral nasal discharge, facial pain or pressure, and nasal blockage.

An opening may be seen in the palatal or buccal alveolus, with polypoid mucosa or purulent drainage.

• Clinical examination and a blunt probe through the tract into the sinus, taking care not to enlarge it.
• Nose blowing test with the nostrils pinched: air bubbling through the defect.
• Cone beam CT of the sinuses and alveolus: size and position of the tract, thickened sinus mucosa, fluid, retained roots and foreign bodies, the state of the ostium and the sinus floor.
• Nasal endoscopy for ostiomeatal obstruction and polyps.
• Culture of purulent discharge when infection persists, and biopsy of unhealed or unusual tissue to exclude tumour.

Differential diagnosis.

• Acute oroantral communication (within 3 weeks)
• Chronic maxillary sinusitis of dental or nasal origin
• Implant migration into the sinus
• Osteonecrosis with oroantral extension
• Maxillary sinus malignancy or granulomatous disease (tuberculosis, vasculitis)
• Cleft palate or palatal fistula
• Odontogenic cyst or tumour perforating the sinus floor

• Treat sinus infection before closure: amoxicillin with clavulanic acid 500 mg and 125 mg orally three times daily for 7 days (or 875 mg and 125 mg twice daily), or doxycycline 100 mg twice daily in penicillin allergy. Reduce amoxicillin with clavulanic acid when eGFR is under 30 (500 mg and 125 mg every 12 hours). Saline nasal irrigation twice daily.
• Surgical closure of the fistula, after excision of the epithelialised tract and debridement of the sinus floor:
  • Buccal advancement flap (a trapezoid flap with a releasing incision of the periosteum) for small to moderate defects, with tension free closure.
  • Palatal rotation advancement flap, or a combined flap, for larger defects, and buccal fat pad flap for large or recurrent defects.
  • Bone graft or collagen membrane when the defect is large, for example when an implant is planned.
• Endoscopic sinus surgery or a Caldwell-Luc approach when chronic sinusitis with polyps, a foreign body or a cyst is present.
• Post-operative care for 2 weeks: no nose blowing, sneezing with the mouth open, avoiding straws, smoking and air travel, a soft diet, chlorhexidine 0.12% to 0.2% mouthwash 10 mL twice daily, and decongestant for 3 to 5 days only when needed (xylometazoline 0.1% one spray each nostril up to three times daily for no more than 5 to 7 days).
• Analgesia: paracetamol 1 g every 6 hours (maximum 4 g daily) with ibuprofen 400 mg every 8 hours with food.
• Closure is successful in over 90% of cases with a well planned flap.

Monitoring. Review at 1 week, 2 weeks and 6 weeks to check the flap, healing and sinus symptoms. Repeat imaging for persistent symptoms.

Referral and escalation. Refer to oral and maxillofacial surgery, with ENT for sinus disease. Urgent referral for suspected tumour, orbital signs or spreading infection.