General Principles of Mandible Fracture and Occlusion 

Updated: Sep 15, 2021
Author: Edward W Chang, MD, DDS, FACS; Chief Editor: Arlen D Meyers, MD, MBA 

Overview

Background

The mandible is the second most common facial fracture, with the nasal bone being the first. Knowledge of the anatomy of the mandible and the muscular forces applied to it is the key to proper reduction of mandibular fractures. The goal in reduction is to restore premorbid occlusion, allowing patients to resume masticatory functions. Prior to repair, patients must be thoroughly evaluated.

As with any trauma, the fundamentals of good trauma care must be followed. The airway must be secured, and breathing and circulation must be confirmed. Possible cervical spine (C-spine) injury needs to be ruled out. With mandibular fractures, earlier reduction is associated with better outcomes. Although, if other injuries dictate, repair may be delayed 5-7 days, surgical correction is recommended as soon as possible. Current concepts include early intervention with wide surgical exposure to allow for precise alignment and rigid fixation.

An image depicting mandible anatomy can be seen below.

Anatomy of the mandible. Anatomy of the mandible.

History of the Procedure

The first descriptions of treating mandible fractures date back to Egypt around 1650 BC. Hippocrates talked of reapproximation and immobilization. Proper occlusion was first addressed in 1180 in Salerno, Italy. Fixation of the maxilla to the mandible was first used in 1492. In the 1950s, the Arbeitsgemeinschaft für osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF) was founded. Early AO plates were stainless steel. Other materials included cobalt-chromium and titanium. Most internal fixation systems use titanium or a titanium alloy. Currently, resorbable plates are being investigated.

Early techniques used to immobilize mandible fractures included bandage immobilization and intermaxillary fixation. During World War II, realignment with open access and wire fixation was popular. More recently, a tremendous amount of fracture management with rigid plate fixation has occurred. Plates were made to span and stabilize the fracture. Plates were then developed to be either compression or noncompression. Furthermore, the compression plates could be made to compress the fracture in an eccentric manner. Compression is achieved by inclines built into the plate. When the screws adjacent to the fracture are activated, the fracture segments are forced together, resulting in primary bone healing. These forces can be directed at the inferior compression site of the mandible or superiorly to the tension aspect of the mandible.

Champy describes using a noncompression, monocortical plate in the region of the external oblique ridge. Ellis has had excellent clinical results using this technique for angle fractures of the mandible.[1]

Current management consists of early surgical intervention with wide exposure of the fracture and placement of rigid fixation. The trend toward rigid fixation is noted in the treatment of comminuted fractures of the mandible. Historically, it was held that closed reduction minimized the stripping of the periosteum of the small bony fragments and was the treatment of choice. Currently, rigid fixation avoids closed reduction and utilizes reconstruction plates and good soft tissue coverage.[2]

Problem

When an external force is imposed on the mandible that is strong enough to cause the mandible to fracture, the surgeon must anticipate associated injuries. Although a single blow to the mandible can yield an isolated fracture, more commonly, 2 sites are involved. The surgeon should always be wary if only one fracture site is identified. For example, trauma to the side usually yields an ipsilateral body fracture and a contralateral subcondylar fracture. A classic severe blow to the symphysis produces a symphyseal fracture and bilateral subcondylar fractures. With bilateral fractures, parasymphyseal or body, always protect the airway from obstruction by the retrodisplaced tongue. In a motor vehicle accident or a gunshot wound, multiple fractures should be suspected along with injuries to the soft tissue, C-spine, and central nervous system. These concomitant injuries are seen in as many as 30% of facial trauma cases.

These injuries may be life threatening and should be dealt with as a high priority. As in all patients with traumatic injuries, the airway should be secured, the patient should be breathing, and the circulation should be stable. The C-spine should always be assessed radiologically and clinically, and injuries here should be ruled out prior to manipulation of the neck. Some C-spine injuries can be asymptomatic. Appropriate consultations should be made to assess the patient. The secondary survey can then be performed, including a full head and neck examination.

Airway compromise often accompanies mandible fracture. Causes can include intraoral bleeding, edema, loose teeth or dentures, and posterior displacement of the mandible and/or tongue due to a flailed segment of the mandible. Consider an emergent tracheotomy or a cricothyrotomy when an obstruction persists despite use of basic cardiopulmonary resuscitation (CPR).

Treatment goals are to restore function and premorbid occlusion. Mastication, speech, and normal range of oral motion should be achieved. Contour defects must be corrected. Early treatment curtails the possibility of infection.

Epidemiology

Frequency

The areas of the mandible most commonly fractured include the condylar-subcondylar region, body, and angle.[3] Location of the fractures and associated frequency are as follows:

  • Condyle - 29%

  • Angle - 24% (If there is only one fracture in the mandible, the angle is the most common site of fracture rather than the condyle.)

  • Symphysis - 22%

  • Body - 16%

  • Ramus - 1.7%

  • Coronoid - 1.3%

The types of fractures commonly seen due to motor vehicular accident have decreased significantly with the use of restraint devices. The symphyseal and bilateral parasymphyseal fractures caused by the mandible striking the steering wheel or dashboard are rarely seen in patients using a seat belt.

The average number of mandibular fractures per patient is 1.5-1.8. Ten percent of patients have more than 2 fractures.

Multiple fractures are more common than single-site fractures. Additionally, current literature still supports that younger males are more prone to mandibular fractures.[4, 5]

Because of the inherent design of the mandible, a unilateral fracture is rare. Children younger than 6 years make up only 1% of the total number of cases. Of note, children with mandibular fractures often have other associated injuries.

The literature indicates that fractures are seen in a higher frequency in males 21-30 years of age.[6]

Etiology

With increased use of vehicular restraints, the incidence of maxillofacial trauma resulting from motor vehicle accidents has been on the decline. On the other hand, the number of mandibular fractures resulting from assault has risen. Other causes include injury from a fall, sports-related injuries, and bicycle accidents. Causes are summarized as follows:

  • Vehicular accidents - 43%

  • Assaults - 34%

  • Work related - 7%

  • Fall - 7%

  • Sporting accidents - 4%

  • Miscellaneous - 5%

Presentation

History can help in the diagnosis. Underlying bone disorders and previous mandibular trauma may predispose a patient to traumatic fractures. The type and direction of force are important, as is the object causing the fracture. Symptoms often described include pain, trismus, difficulty chewing, and anesthesia or paresthesia of the lower lip and chin.

On examination, findings include abnormal mandibular movements, malocclusion, change in facial contour and mandibular arch form, tenderness, swelling, redness, lacerations, hematoma, and ecchymosis. Loose and fractured teeth should be evaluated and counted. If teeth are missing, consider a chest radiograph to rule out aspiration.

Premorbid occlusion can be confirmed by examining the wear facets on the surfaces of the opposing teeth. Patients are quite sensitive to changes in their occlusion and can appreciate displacements smaller than 1 mm. It must be remembered that not all patients have ideal occlusion (ie, only 74% of the population have an Angle class I bite). The remainder has either retrognathia (Angle class II, 24%) or prognathia (Angle class III, 1%).

Angle classification is based on the relationship of the mesial-buccal cusp of the maxillary first molar to the buccal groove of the mandibular first molar. (Mesial is anterior in reference to the sagittal plane and distal is posterior to that same plane.) Anatomy is shown in the image below.

Anatomy of the first molars. Anatomy of the first molars.

Oral and maxillofacial surgeons also use the relationship of the canine teeth to determine the occlusal class. Class I occlusion refers to the mesial-buccal cusp of the maxillary first molar's contact with the mandibular first molar's buccal groove. The mesial-buccal cusp lies in front of (or mesial to) the groove in class II occlusion. In Angle class III occlusion, the mesial-buccal cusp of the maxillary first molar falls behind (or distal to) the groove.

Fractures that occur in the region of the teeth are considered to be compound fractures, which can be predisposed to bacterial contamination from the oral cavity. An open laceration and bleeding from the site also may be evident with compound fractures. These types of fractures should, therefore, be prophylactically treated with antibiotics. If the mucosa has not been violated, then clinical findings can be limited to ecchymosis. If the third division of the trigeminal nerve (the inferior alveolar or mental nerve) has been injured, the patient may have paresthesia or anesthesia of the chin. Documenting this and the function of the marginal mandibular nerve (branch of cranial nerve VII) is important prior to surgical intervention. The nerve course is shown in the image below.

Course of the facial nerve. Course of the facial nerve.

Spasm of the muscles of mastication due to trauma can result in trismus, limiting a proper oral examination. Facial edema, erythema, and pain are also associated with mandibular fractures. Bilateral parasymphyseal/body and, at times, subcondylar fractures can result in the posterior displacement of the tongue, leading to airway compromise. In accordance with the tenets of trauma care, the airway should always be addressed first.

The fracture may be classified as simple, greenstick, compound, comminuted, or pathologic. Furthermore, classification can take into account forces influenced by muscular distraction. Muscular force can act favorably (nondisplaced fracture) or unfavorably (displaced fracture). Displacement can occur in either the horizontal or the vertical plane. Favorable and unfavorable fractures are shown below.

Favorable and unfavorable fractures. Top: Horizont Favorable and unfavorable fractures. Top: Horizontal reference. Bottom: Vertical reference.

Indications

Generally, some form of therapy is needed for a fracture of the mandible. Perform the most conservative treatment that allows for reduction of the fracture while preserving the premorbid occlusion.

Observation

Historically, for minimally displaced fractures that were of a favorable type, a Barton-type head bandage gave enough support for the fracture to heal. This was especially true in children. A liquid or pureed diet was maintained for 4 weeks. The trends currently advocate early surgical intervention, wide access to the fracture site, and complete immobilization with rigid fixation.

Factors affecting fragment displacement include the direction and intensity of the traumatic force, direction and bevel of the fracture line, presence or absence of teeth in the fragments, direction of muscle pull, and extent of soft-tissue injury. In a favorable fracture, the muscle pull promotes splinting of the segments; muscle pull distracts the segments in an unfavorable fracture.

Muscles involved in opening the mouth include the anterior belly of the digastric muscle and the mylohyoid, geniohyoid, and genioglossus muscles. Oral closure is provided by the action of the temporalis, masseter, and the internal (or medial) pterygoid muscles. The only protrusion from the mandible is the external, or lateral, pterygoid muscle. The forces of these muscle groups, along with the bevel and angle of the fracture, determine whether or not a fracture is favorable or unfavorable.

Maxillomandibular fixation and closed reduction

If external dressings are not sufficient, closed reduction can be accomplished with maxillomandibular fixation (MMF), formerly known as intermaxillary fixation (IMF; shown in the image below).

Maxillomandibular fixation using arch bars retaine Maxillomandibular fixation using arch bars retained with composite resin.

Cawood has described many ill effects of MMF when arch bars and ligatures are used. To avoid these types of issues, 4-point MMF can be used, as depicted in the image below. Otherwise, arch bars are placed with wire ligature (24-26 gauge) or composite resin.

Four point fixation for maxillomandibular fixation Four point fixation for maxillomandibular fixation.

Some authors indicated in their cost analysis studies that closed reduction and MMF was more cost-effective when compared with ORIF.[7, 8]

Open reduction

Open reduction is an excellent modality for fracture segment reduction.[9, 10]  After MMF, an incision is made to allow for direct alignment of the segments. Access can be achieved via either an intraoral or extraoral incision, depicted below. To maintain fixation, titanium plates and screws or stainless steel wire may be used. Even with an incision, percutaneous access may be needed for the placement of plates, screws, or wire.

Facial incisions. Facial incisions.

External fixation, shown in the image below, was popular in World War II but currently is not often employed. Principle indications are sites that have been infected or pathological fractures. It can also be used in edentulous patients with unstable fractures. Stainless steel pins and composite resin placed lateral to the mandible keep the fracture rigidly reduced.

When an infection or severe comminution is present When an infection or severe comminution is present, an external fixation device may be used.

Other alternatives include use of the patient's dentures to reduce the fracture. The dentures act as a splint, and with the use of circumferential mandibular wires, they can stabilize the fracture, as shown below. The upper and lower dentures can be wired together to maintain MMF. If the patient is edentulous but without dentures, a Gunning-type splint can be fabricated and used in the same manner as dentures.

When dentures are available, they can be used with When dentures are available, they can be used with the circummandibular wire technique.

Relevant Anatomy

The mandible is derived from the first branchial arch. Its bone is membranous in nature. Ossification is by direct mineral deposition into the organic matrix of mesenchyme or connective tissue. Bone matrix is 35% organic and 65% inorganic, and 90% of the organic component is type I collagen. Hydroxyapatite makes up most of the inorganic portion of bone.

The mandible is divided into the condylar, subcondylar, ramus, angle, body, parasymphyseal, symphyseal, coronoid, and dental alveolar regions.

The structure of the mandible is such that masticatory force trajectories are transmitted to the skull base, but the jaw usually fractures prior to penetration of the middle cranial fossa. This design permits great forces on the mandible to be distributed along its frame, shown in the image below. If the stress is great enough, the mandible fractures and absorbs the impact, thereby lessening the forces on adjacent vital structures.

Anatomy of the mandible. Anatomy of the mandible.

Knowledge of the anatomy of the mandible and surrounding soft tissues aids in the proper reduction of fractures. The third division of the trigeminal nerve enters the mandible, at the lingula, as the inferior alveolar nerve (IAN). The lingula is also the point of attachment for the sphenomandibular ligament. The IAN gives off dental branches before exiting the mental foramen, located between the first and second premolar teeth, in the lower third of the mandible as the mental nerve, shown below. Knowledge of the path of the nerve and the length of the teeth is important in planning the placement of titanium plates and screws.

Intraoral access with identification of the mental Intraoral access with identification of the mental nerve.

Dental occlusion is determined by the opposition of teeth of the upper and lower arches. Primary dentition starts with the incisors at 6 months of age, and all 20 teeth are present by age 2.5 years. The permanent teeth start with the eruption of the first molars around age 6 years, and the completion of the dentition takes place at age 16-20 years. The surfaces of the teeth help determine the premorbid occlusion. Wear facets can be identified and guide the surgeon to the proper occlusion. The cutting surface anteriorly is referred to as the incisal surface. The posterior teeth have occlusal, lingual, mesial, and distal surfaces. Between the teeth are embrasures or interdental spaces, which are used to place wire ligatures. This anatomy not only helps in the planning and execution of surgery, but it also is useful in communicating with other members of the surgical team.

Contraindications

Prior to the management of mandibular fractures, the patient should be properly assessed. Reduction of fractures can be delayed until the patient is stable. Ideally, fracture reduction should be performed within 7-10 days. After this period, the risks of malunion, malocclusion, and facial asymmetry increase.

In some situations, MMF may not be the best therapy, and open reduction with internal fixation may be a better alternative.

Poor candidates for MMF include the following:

  • Patients who are noncompliant

  • Patients with alcoholism, seizure disorder, severe pulmonary dysfunction, mental retardation, psychosis, or poor nutrition (eg, patients with diabetes)

  • Patients who are pregnant

  • Patients with multiple injuries

  • Patients who are unwilling to make the change in lifestyle that is needed for 4-6 weeks

Currently, no real absolute contraindications for open reduction with internal fixation exist. Two relative contraindications include poor bone height, and a pediatric mixed dentition that limits the placement of fixation devices.

 

Workup

Laboratory Studies

See the list below:

  • Routine preoperative laboratory studies are ordered in preparation for surgery.

Imaging Studies

See the list below:

  • A CT scan is extremely useful in maxillofacial trauma. Obtain images in both the axial and coronal planes.

  • A panoramic radiograph (Panorex) affords an excellent 2-dimensional representation of the mandible. The entire mandible and the dentoalveolar structures can be viewed with the Panorex. Historically, the symphyseal region was limited due to overlap wash out, but current orthopantograms give an excellent view of the mandible.

  • Several types of plain films add to the evaluation of mandibular fractures.

    • The dental periapical view gives fine detail to the teeth and their roots.

    • The dental occlusal view helps determine whether the fracture is vertically favorable or unfavorable. It delineates the medializing effects of the internal pterygoid posterior to the first molar and the mylohyoid anterior to the first molar.

  • The mandibular series includes several views to help identify the fracture.

    • The Caldwell is a coronal view that shows displacement in the horizontal plane.

    • The oblique views highlight the ramus angle and posterior body.

    • The reverse Towne view depicts the condylar/subcondylar region well.

  • Obtain a chest radiograph when evidence of a broken denture or missing tooth is present.

 

Treatment

Medical Therapy

Nonoperative therapy is reserved for minimally displaced favorable fractures. Children often incur an incomplete fracture called a greenstick fracture, which is amenable to conservative therapy. Elderly edentulous patients with minimal displacements can be treated in a similar manner. Dressings help relieve the discomfort of the fracture. Minimal occlusal load is recommended when this mode of therapy is used.

The use of preoperative and perioperative antibiotics in the treatment of mandible fractures has been accepted to reduce the risk of infection, but continuing this antibiotic regimen into the postoperative period did not further improve the infection rate.[11, 12]

Surgical Therapy

Goals of treatment include anatomic reduction of fracture segments, restoration of premorbid occlusion, and avoidance of complications. Ideally, treatment should be instituted within 7 days. Options to consider include closed or open reduction. Closed reduction maintains the segments by maxillomandibular fixation. Open reduction allows for direct evaluation of the mandibular segments and further for internal or external fixation. Internal fixation can be accomplished by wire (used more historically and in children), titanium plate, and screw fixation.

The Joe-Hall-Morris appliance is an example of an external-pin fixation device. It was used extensively in World War II but has dropped out of favor. Surgeons should be familiar with this technique and have it as part of the surgical armamentarium. It is particularly useful in edentulous patients with a comminuted fracture.

Oblique fractures, especially in the parasymphyseal region, are amenable to lag screws or to the lag technique, in which the proximal segment is drawn towards the distal segment. See the images below.

Radiograph of an oblique parasymphyseal fracture a Radiograph of an oblique parasymphyseal fracture amenable to use the lag screw technique.
Reduction using the lag screw technique. Reduction using the lag screw technique.
Fracture reduced with 2 screws used in the lag scr Fracture reduced with 2 screws used in the lag screw fashion.
Using percutaneous access in the difficult angle r Using percutaneous access in the difficult angle region.

Although 3 screws are ideal, 2 screws are sufficient to hold the segments in proper reduction. When determining the mode of therapy, consideration must be given to patient age, general health, and reliability, as well as position, stability, and severity of the fracture. One must not overlook the patient's dental and periodontal status, the availability of materials and instrumentation for repair, availability of dental consultation, and the skill and experience of the surgeon.

Preoperative Details

Perioperative antibiotics are recommended, especially in fractures that go through areas with teeth. These are considered compound fractures, and should be treated as such. Chole and Yee showed a 43% infection rate in the study group without antibiotics, compared to an 8.9% infection rate in the group with antibiotics.

It is important to obtain appropriate diagnostic studies to aid in the localization of fractures. Developing a careful patient treatment plan but being prepared to deviate from the treatment plan as needed is also crucial. A dental evaluation helps to determine the condition of the teeth and allows appropriate fabrication of a dental appliance when needed.

Intraoperative Details

Occlusion is always set first. The occlusion can be maintained by maxillomandibular fixation. Simply, 4 titanium screws can be placed, 1 in each dental quadrant, to permit wire fixation of the upper and lower arches. Stainless steel ligatures with eyelets can be passed interdentally to be used for MMF.

More commonly, Erich arch bars are placed and secured with wire. Stainless steel wires (24-26 gauge) are placed around available molar, premolar, or canine teeth. Anterior teeth should not be used for fixation because of their conical shape, which will cause them to be distracted out of the socket by the wire. Erich arch bars are outfitted with prongs that permit the upper and lower bars to be held together with looped wires. An alternative for attaching the arch bar to the mandible and maxilla other than wires involves light-cured resin composites. One caveat, if a subcondylar fracture is present, immobilization must not exceed 2 weeks. Physiotherapy is instituted to prevent ankylosis of the condyle.

Open reduction necessitates a mucosal or skin incision, shown below, for direct access to the fracture site.

Facial incisions. Facial incisions.

Fixation can then be accomplished with either wires or titanium plates and screws. Open reduction is used when closed reduction is insufficient to achieve anatomic alignment and immobilization. It should also be considered when contraindications to MMF arise.

The condyle can be approached intraorally with a sulcus incision or extraorally through a preauricular incision. Abdel-Galil and Loukota concluded that level I evidence indicates supporting superior functional results following open reduction and internal fixation of condylar fractures.[13]

The angle can be addressed with a sulcus incision, percutaneous access, and/or a posterior angle incision. Sometimes, a combination of access is needed, especially at the angle of the mandible. The body and parasymphyseal area is generally easily approached intraorally with a sulcus incision. With any incision, the surgeon must be cognizant of the course of the marginal mandibular branch of cranial nerve VII. The nerve is more at risk from an external access incision than percutaneous access.

Once the fracture is localized, some important concepts must be kept in mind. Mandibular tensile forces exist superiorly at the dentoalveolar area, and compressive forces exist at the inferior border. To combat the distraction of the segments, place a tension band superiorly along with an inferior plate. The tension band can take the form of an arch bar if teeth are present proximal and distal to the fracture line. If no teeth are found proximally, a small plate may be placed on the external oblique ridge of the mandible to act as a tension band. This concept is exemplified in Champy's technique. Ellis has had great success with noncompression, monocortical plates, fashioned in 2 planes at the external oblique ridge, for nondisplaced angle fractures.[1] The 2-dimensional bend counteracts forces in both horizontal and vertical planes. See the images below.

A minimally displaced posterior mandible fracture. A minimally displaced posterior mandible fracture.
Intraoperative view with external oblique ridge in Intraoperative view with external oblique ridge in view, situation ideal for Champy technique.
A monocortical plate configured in 2 dimensions to A monocortical plate configured in 2 dimensions to fit at the external oblique ridge.
Postoperative radiograph. Patient had an open redu Postoperative radiograph. Patient had an open reduction with internal fixation (ORIF) using the Champy technique and is not in maxillomandibular fixation.

For the inferior aspect of the mandible, a compression plate may be used. The medial screws are placed laterally in the screw hole and, as they engage the bone, they slide medially, compressing the mandibular segments together, shown below.

Top: Inferior compression plate. Bottom: Eccentric Top: Inferior compression plate. Bottom: Eccentric compression plate.

An eccentric compression plate also exists, in which the medial screws bring the inferior portion of the mandible together while the lateral screws draw the superior aspect of the mandible together. Various sizes of plates and screws exist, and newer resorbable plates are currently under investigation. At present, the resorbable plates are being used in non–load-bearing areas, such as the periocular area. The surgeon should be familiar with the many plate sizes as well as the specifications of the different companies' products.

Employing three-dimensional models and finite element analysis to compare five plating techniques for unilateral subcondylar fracture, Darwich et al reported that the trapezoidal plate, used singly, most successfully resisted displacement and exhibited the least amount of cortical bone strain, while a single straight plate exhibited the most displacement and the greatest amount of cortical bone strain. The other plating techniques tested were the use of two parallel straight plates, two angulated straight plates, and one square plate.[14]

Postoperative Details

Patients left in MMF should have a nasal trumpet until fully awake. Wire cutters should be taped to the head of the bed, and a tracheotomy tray should be in the room.

Teach patients to use a 60-cc syringe, with a 3-inch trimmed red rubber catheter attached at the end of the syringe, for feeding. The catheter is placed into the sulcus adjacent to the fixated arches so liquids and pureed food can then be easily delivered from the syringe.

Patients must practice strict oral hygiene. Chlorhexidine (Peridex) oral rinses after meals and at bedtime should be prescribed if an intraoral incision is used.

Follow-up

Patients should be seen on a weekly basis. The condition of the arch bars, as well as the tension on the MMF wires, can be checked and tightened as necessary. Children are kept in MMF for 4 weeks, adults for 6 weeks, and elderly patients for 8 weeks. Patients with condylar fractures must be taken out of MMF by 2 weeks, and aggressive physiotherapy must be instituted to prevent ankylosis. Measure the oral opening on each follow-up visit. Normal interincisal distance is 40 mm. If open reduction and internal fixation is performed, many feel that MMF is not needed. By not having the patient in MMF, the ill effects are avoided and the patient's comfort level is increased.

Complications

Complications can arise with delayed treatment, inadequate treatment, poor patient constitution, or poor postoperative care. Acute complications are the result of trauma itself. Intermediate complications are caused during MMF, and late ones occur after MMF. The overall complication rate is 3 times as high if the fracture is treated more than 10 days after initial injury.

The greatest potential for respiratory distress occurs with bilateral body, parasymphyseal, or condylar fractures. Muscular action pulls the distal mandibular segment posteriorly, causing the tongue to obstruct the oropharynx. Depending on the degree of neural injury, nerve function may or may not return. In neurapraxia, function returns in 4-6 weeks, whereas in neurotmesis, function may or may not return for approximately 18 months.

An infection increases the chance of delayed union, nonunion, osteomyelitis, and loss of teeth and bone structure. Infection prolongs hospitalization and disability and increases the financial burden. With any open fracture or fractures involving teeth, antibiotics are recommended. A study by Li et al indicated that in patients undergoing rigid internal fixation of mandibular fracture, independent risk factors for multidrug-resistant bacterial (MDRB) infection include obesity, preoperative infection, and open fractures. The Chinese study included 933 patients, 16 of whom (1.71%) developed an MDRB infection.[15]

A bony union is expected to result within 4-8 weeks with proper reduction and immobilization. Any time longer than 8 weeks is considered a delayed union and is seen when MMF is released prematurely. Pain and mobility require MMF to be reinstituted and within 8 weeks, a union is eventually formed.

Nonunion occurs when no future potential exists for the bone to ultimately heal. Usually, a pseudoarthrosis is present, in which surgery is required to allow for union. Approximately 2.4% of fractures result in nonunion. Malunion occurs when the bone heals with improper alignment.

Ankylosis is seen with an interincisal opening smaller than 5 mm. The normal oral opening is 40 mm, measured from incisal edge to incisal edge of the anterior teeth. The ankylosis is either fibrous or bony. Aggressive physiotherapy may release a fibrous ankylosis, but surgery is required in the latter case.

Outcome and Prognosis

With proper treatment planning and surgical technique, mandible fractures have a favorable prognosis. The overall infection rate is 6-6.5% for rigid fixation and around 12.9% for conservative treatment. Ultimately, more than 90% of mandible fractures that are treated achieve a bony union.

Future and Controversies

Although great success has been seen with the titanium plate and screw systems, the use of resorbable plate and screw systems is currently being investigated. Initial studies were started over 40 years ago. Resorbable plates are used in craniofacial reconstructive surgery. Their greatest benefits include the lack of translocation as the child grows and, with resorption, lack of interference with the growth centers. Indications include fractures of bones that are non-weightbearing in the periocular and midface regions. Due to the great muscular forces, success has been limited in the mandible. Current efforts will determine if the new generation of resorbable plates will be strong enough to maintain reductions in mandibular fractures.

Studies, such as the report from Mizuhashi, have investigated the characteristics of resorbable plates under dynamic loading.[16] Neither dynamic loading nor degree of load were shown to clearly affect the degree of hydrolytic degradation. The original shape and bending strength were maintained for up to 4 weeks.

Another area that has gained increased reports in the literature is the treatment of fractures of the condyle. This is still an area of controversy.[17] Treatments have been conservative or surgical. Eulert et al reviewed 1812 patients treated between 1981 and 2001.[18] Their statistical analysis revealed that surgical osteosynthesis was superior to conservative therapy. Schoen reported functional results of endoscopic-assisted open treatment of bilateral condyle fractures.[19] The conclusion of the report was that surgical therapy was reliable, and the long-term results revealed good temporomandibular joint (TMJ) function without risk of facial nerve damage and visible scarring.

Intermaxillary fixation screws have been gaining more and more popularity. A 2007 article by Coletii et al concluded that the IMF self-drilling/tapping screws have been shown to be a useful modality to establish MMF.[20] It was felt to be safe, and time sparing; however, it was not without limitations or potential consequences.

These are exciting areas that the reader should gain more experiences in for the care of the fractures of the mandible.