Trismus caused by migration of orthodontic archwire into the infratemporal fossa: a case report.

Introduction: Soft tissue injuries are known complications of orthodontic treatment. Most of the injuries are mild, but severe complications can arise from deeper penetration or dislodgement of brackets and other foreign bodies into the surrounding tissues of the oropharynx and infratemporal fossa.

Patient concerns: The patient, accompanied by his parents, presented to the Children's Emergency Department with the concern of gradual limitation of mouth opening and eventual trismus, which occurred over a span of 2 weeks.

Clinical findings: The patient presented with trismus and slight discomfort at the left cheek region. He reported a history of gradual limitation to his mouth opening 2 weeks prior. He was wearing upper and lower fixed orthodontic appliances and the left distal end of the maxillary archwire was found to have migrated into the left infratemporal fossa.

Primary diagnoses: Left medial pterygoid muscle inflammation, or bleeding and haematoma formation, or infection within the infratemporal region.

Interventions: The maxillary archwire was removed in the Children's Emergency Department and a computed tomography (CT) scan performed subsequently confirmed the diagnosis of left medial pterygoid muscle inflammation. The patient was started on an intravenous (IV) antibiotic and a 2-day course of IV dexamethasone to reduce the muscle inflammation.

Outcome: By the second day, the patient was able to achieve a mouth opening of 6 mm, and by the second week, the mouth opening had returned to normal.

Conclusion: The potential risk of soft tissue injury and complications from orthodontic treatment is generally mild and limited. Soft tissue injuries can be avoided with careful management by the operator with the proper precautions taken. Clinicians should be familiar with the surrounding soft tissue anatomy and be aware of the potential for more severe complications and provide management or referral to the appropriate specialty accordingly.