Any significant force applied to the mandible can cause fractures to this ring-like structure. Open fractures are common, including laceration of the gum overlying a fracture.
The mandible is the third most commonly fractured facial bone, following nasal and zygomatic fractures. Most frequently, fractures are a result of trauma, such as motor vehicle accidents, personal violence, industrial accidents, or contact sports.
Vehicular accidents and altercations are the primary causes of mandibular fractures in the United States and throughout the world. In urban trauma setting, altercations accounted for most fractures (50%), and motor vehicle accidents were less likely (29%).
Mandibular fractures are uncommon in children under age of 6. When they occur, they are often greenstick fractures.
Because of its ring-like structure, multiple fractures are seen in more than 50% of cases. The most common fractured area is the body (29%), followed by the condyle (26%), angle (25%), and symphysis (17%). The ramus (4%) and coronoid process (1%) are rarely fractured. In automobile accidents, the condyle was the most common fracture site; whereas, the symphysis was most commonly fractured in motorcycle accidents. In assault cases, the angle is the most common fractured site.
Mandible fractures can be classified by favorableness, based on the association between the direction of the fracture line and the way muscle distraction affects the fracture fragments. Mandibular fractures are favorable when muscles tend to draw the fracture fragments together and unfavorable when muscle forces displace fracture fragments.
Depending on the fractured areas, the patient can present with trismus, dental malocclusion, swelling, and tenderness externally and intraorally. Damage to the inferior alveolar nerve may result in anesthesia to the lower lip.
Patients with mandibular fractures frequently have other associated injuries (43%). The most common associated injuries include head injuries (39%), head and neck laceration (30%), midface fractures (28%), ocular injuries (16%), nasal fractures (12%), and cervical spine fractures (11%).
The presence of lower wisdom teeth may increase the risk of fracture of the angle of the mandible. Patients with a mandibular fracture that have wisdom teeth also have a higher infection risk (16.6%) when compared with the ones without wisdom teeth (9.5%).
In the pediatric population, any fracture of the mandible may damage permanent teeth. Follow up with the oral and maxillofacial surgeon is indicated.
Patients will present with mandibular pain, facial asymmetry, deformity, and dysphagia. Malocclusion, a decreased range of movement of the temporomandibular joint, trismus, or lower lip numbness can also be present. Eliciting the mechanism of injury is important. In a vehicular motor accident, the patient usually suffers from multiple, compound, or communicated mandibular fractures. Mandibular fracture of a patient from an altercation is usually single, simple, and nondisplaced.
On physical examination, one should inspect the maxillofacial area for deformity, including ecchymosis and swelling. One should also look for any malocclusion, trismus, or facial asymmetry. A careful intraoral examination should be performed; sublingual hematoma is suggestive of an occult mandibular fracture.
The tongue-blade bite test is a quick and inexpensive diagnostic tool for predicting mandibular fractures. It has a sensitivity of 88.5% and a specificity of 95%. It can be performed by asking the patient to bite down strongly on a tongue depressor and keep the tongue depressor clenched between the teeth. The examiner should twist the tongue blade. If there is no fracture of the mandible, the examiner should be able to break the blade. In the presence of a mandibular fracture, the patient opens his or her mouth because they experience pain from the fracture, and the tongue depressor remains intact.
Diagnosis of mandibular fractures requires radiographic imaging studies, including mandibular series, panorex, and CT scan. Mandibular series include anteroposterior view, bilateral oblique views, and Towne view. They are best for evaluating the condyles and neck of the mandible. Dental panoramic view, or panorex, is best for evaluating the symphysis and the body of the mandible. CT scan is indicated if associated facial fractures are suspected. A chest radiograph is necessary for an unconscious patient with missing teeth to rule out aspiration.
Laboratory studies are generally not indicated unless urgent or emergency surgery is anticipated. In those situations, basic screening labs should be obtained including complete blood count, complete or basic metabolic panel, type and screen, and prothrombin time or INR for patients who are on warfarin for anticoagulation.
Patients with mandibular fractures frequently have associated injuries. Initial treatment should be directed toward immediate, potentially life-threatening injuries such as airway obstruction, major hemorrhage, cervical spine injury, and intracranial injury. If oral intubation cannot be performed, cricothyrotomy is indicated. Nasotracheal intubation should not be performed if midface or nasal fractures are suspected. Patients with mandibular fractures should also be placed on cervical spine immobilization.
Mandibular fractures with mucosal, gingival, or tooth socket disruption are considered open fractures, and antibiotics with intraoral anaerobic pathogens coverage should be given to reduce the risk of infection. The appropriate antibiotic agent includes penicillin, ampicillin/sulbactam, and clindamycin for penicillin-allergic patients. Tetanus prophylaxis is also indicated in open fractures. Pain control should be achieved with acetaminophen, NSAID, or opioid.
Fractures of the body, angle, ramus, and symphysis will require splinting by placing arch bars to accomplish interdental fixation, also known as "wiring the jaw shut." Fixation limits fracture motion and decreases the patient's pain and discomfort. It normally takes 4 to 6 weeks to achieve satisfactory healing.
Patients with linear, nondisplaced, or greenstick fractures can be treated as an outpatient with a soft diet, analgesic, and urgent follow up with the oral and maxillofacial surgeon for elective operative repair that can be performed as an outpatient procedure in 3 to 5 days. Barton's bandage, an ace wrap over the top of the head and underneath the mandible, should be placed to stabilize the fracture and help relieve pain.
Hospital admission is indicated in patients with significantly displaced fracture. An oral and maxillofacial surgeon should be consulted for open fractures which require operative repair. Patients with airway compromise, patients who are unable to tolerate POs and secretions, and patients with inadequate pain control will also require hospital admission.
Differential diagnosis includes mandibular contusion, mandibular dislocation, and isolated dental trauma. In a mandibular dislocation, if a single condyle is dislocated, the jaw will deviate away from the side of the dislocation. In mandibular fracture, the jaw will deviate toward the side of the fracture.