Oroantral fistula

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Oroantral fistula (OAF) is an abnormal condition of the face where the maxillary sinus is exposed to the oral cavity through an epithelialised fistula. This term signifies pathology and it is not to be confused with oroantral communication (OAC). OAC if left untreated can either heal spontaneously or progress into OAF. The fistulous opening may be situated on the alveolus.

Video Oroantral fistula

Signs and symptoms

Maps Oroantral fistula

Cause

The maxillary sinus is known for its thin floor walls and close proximity to the posterior maxillary teeth. Dental procedures such as extraction of these teeth sometimes cause OAC. The posterior maxillary molars and maxillary sinus are innervated by the same branch of nerves which is the maxillary division of trigeminal nerve. This innervation complicates the situation as the pain from maxillary sinus might be indistinguishable from a posterior maxillary toothache. Other known causes of OAC are fracture across the antral floor typically Le Fort I, displacement of posterior maxillary molar roots into antrum, and direct trauma. Extraction of primary teeth are not considered a risk of OAC due to the presence of developing permanent teeth and the small size of a developing maxillary sinus. OAC can happen for many other reasons, such as acute or chronic inflammatory lesions around the apex of tooth root present in close proximity with the maxillary antrum, necrotic lesions of the maxilla, failure of sublabial incision to heal after Caldwell-luc antrostomy, multiple and extensive fractures of the facial region, osteomyelitis of the maxilla, injudicious use of instruments during oral procedures, malignancy of the maxillary sinus, Syphilis, malignant granuloma, radiotherapy, implant denture, removal of a large cyst or resection of large tumour involving maxilla, development of tumour causing bone destruction and loosening of teeth.

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Diagnosis

Clinical examination and x rays can help diagnose the condition. For examples :

• Valsalva test (nose blowing test): Ask the patient to pinch the nostrils together and open the mouth, then blow gently through the nose. Observe if there is passage of air or bubbling of blood in the post extraction alveolus as the trapped air from closed nostrils is forced into the mouth through any oroantral communication. Gentle suction applied to the socket often produces a characteristic hollow sound.
• Perform a complete extra- and intra-oral examination using a dental mirror under good lighting, look for granulation tissue in the socket and openings into the antrum.
• Panoramic radiograph or paranasal computed tomography can help to locate the fistula, the size of it and to determine the presence of sinusitis and other foreign bodies. Other methods like radiographs (occipitomental, OPG and periapical views) can also be used to confirm the presence of any oroantral fistulas.
• To test the patency of communication the patient is asked to rinse the mouth or water is flushed in the tooth socket.
• Unilateral epistaxis is seen in case of collection of blood in the sinus cavity.
• Do not probe or irrigate the site, because it may lead to sinusitis or push foreign bodies, such as contaminated fragments, or oral flora further into the antrum. Hence, leading to the formation of a new fistula or widen an existing one.

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Complications

OAF is a complication of oroantral communication. Other complications may arise if left untreated. For example:

• Candidal infection
• Chronic maxillary sinus infection of bacterial origin
• Osteomyelitis
• Rhinosinusitis
• Sinus pathology

Therefore, OAF should be dealt with first, before treating the complications.

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Prevention

Studies have shown that sinusitis is found in about 60% of the cases on the fourth day after the fenestration of sinus. Moreover, patient may develop an acute sinus disease if OAC is not treated promptly upon detecting clear signs of sinusitis. So, early diagnosis of OAC must be conducted in order to prevent OAF from setting in.

Spontaneous healing of small perforation is expected to begin about 48 hours after tooth extraction and it remains possible during the following two weeks. Patient must consult the dentist as early as possible should a large defect of more than 7mm in diameter or a dogged opening that requires closure is discovered so that appropriate and suitable treatment can be swiftly arranged or referral to Oral Maxillofacial Surgery (OMFS) be made at the local hospital, if required.

A comprehensive preoperative radiographic evaluation is a must as the risk of OAC can increase due to one or more of the following situations :-

• Close relationship between the roots of the maxillary posterior teeth and the sinus floor
• Increased divergence or dilaceration of the roots of the tooth
• Marked pneumatization of the sinus leading to a larger size
• Peri-radicular lesions involving teeth or roots in close association with the sinus floor

Hence, in such cases:

• Avoid using too much of apical pressure during tooth extraction
• Perform surgical extraction with roots sectioning
• Consider referral to OMFS at local hospital

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Treatment

The primary aim of treatment of a newly formed oroantral communication is to prevent the development of an oroantral fistula as well as chronic sinusitis. The decision on how to treat OAC/OAF depends on various factors. Small size communications between 1 and 2 mm in diameter, if uninfected, are likely to form a clot and heal by itself later. Communications larger than this require treatments to close the defect and these interventions can be categorised into 3 types: surgical, non-surgical and pharmacological.

Surgery

Small OACs can be closed by suturing the gingiva over the defect. A soft tissue flap is required when suturing is not able to close the defect. The aim of this is to encourage the growth of new bone between the oral and antral cavites. Here the blood clot within the socket is protected to prevent infection of the antrum while bone formation and organization takes place. If surgical management is to be delayed or contraindicated then an acrylic base plate can be used to support the clot or dressings like Whiteheads varnish can also be used to suture across the defect.

In long standing defects that have developed into a fistula, the associated epithelial lining must also be completely excised. Additional bone grafting may be required in conjunction with soft tissue flaps, when soft tissue flaps alone are not sufficient to provide closure or there is a need to correct the associated bone defect

Most surgical techniques are based on the principle of mobilising the tissue and advancing the resultant flap into the defect. The buccal advancement flap technique is the most commonly used method for closing OAC/OAF. This flap design provides good blood supply and has a high success rate. It can also be used in combination with Caldwell-Luc operation to clear the antrum of any pathology. The main disadvantage of this technique is the significant reduction in vestibular or sulcus depth after closure, which can affect the provision of removable dentures post-surgery. Alternatively, a pedicled buccal fat pad flap may be used to overcome the issue of sulcus depth loss.

The palatal rotational flap technique is an alternative flap design which can be used for communications larger than 1 cm. This flap is more robust and can also overcome the issue of buccal sulcus depth reduction. However, complications such as palatal bone exposure and roughening and deepening of the flap may occur with this design.

Non-surgical interventions

These interventions employ the principle of placement of materials into the defect without flap closure. These materials may act as a mechanical barrier and/or promote the healing process of the communication. Different materials, such as synthetic graft materials, xenografts, fibrin glue, synthetic absorbable implant and acrylic splints has all been reported as potential material to use.

Medication

Medications may be needed as an adjunct to assist the closure of the defect. Antibiotics can help control or prevent any sinus infections. Preoperative nasal decongestants usage can reduce any existing sinus inflammation which will aid surgical manipulation of the mucosa over the bone.

Postoperative care

Following all methods of OAC/OAF closure, the patients are instructed to avoid activities that could produce pressure changes between the nasal passages and oral cavity for at least 2 weeks due to risk of disruption to the healing process. Nose blowing and sneezing with a closed mouth are prohibited. A soft diet is also often advocated during this period. Following surgery, nasal decongestants and prophylactic antibiotics are often prescribed to prevent postoperative infection.

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References

Source of article : Wikipedia