Definition & Overview
The application of an interdental fixation device is a procedure used in the treatment of mandibular fractures. Its purpose is to stabilise or reduce a fracture. There are several types of interdental fixation devices in use these days, including arch bars, Ernst ligatures, interdental wiring, and metallic splints, among others. Such devices are widely used, are highly effective, and have low complication rates.
Who Should Undergo and Expected Results
The application of an interdental fixation device is beneficial for patients who suffer from mandibular fractures. The devices can stabilise and reduce the fracture. The procedure is considered as a closed reduction method but is also used as an adjuvant treatment alongside open reduction.
A mandibular fracture is a fracture of the jaw or when the jawbone is broken. It is most often due to trauma. This injury is very common because of the jawbone’s lack of support and the jaw’s prominence in the face. Statistics show that the majority of such injuries occur due to vehicular accidents. The rest are caused by assaults, work-related accidents, accidental falls, and sporting accidents. These fractures can affect either the body of the jawbone, the condyle, or the angle of the mandible. They can also be simple or close, compound or open, or comminuted (in which the bone is crushed or splintered).
There are two main types of interdental fixation devices: tooth-borne devices and bone-borne appliances.
Tooth-borne devices are ideal for patients who have complete, healthy teeth. This means that they are not suitable for those with multiple missing teeth, carious or weak teeth, dental crowns, or dental bridges. If the patient does not qualify for tooth-borne devices, doctors will use bone-borne devices.
Bone-borne appliances work through bone-to-bone fixation. Some examples of these devices include:
- IMF (intermaxillary fixation) screws – These are self-drilling and self-tapping stainless steel screws with an elongated head. They contain two holes that allow wire placement.
- Hanger plates
- Interarch miniplates
IMF screws and other bone-borne devices are considered as a reserve method. They are most commonly used for emergency cases or if the patient’s condition or circumstances make it impossible to apply an arch bar. They are, however, not advisable for comminuted, segmented fractures, and severe displacement. They are also not used on children whose tooth buds are still in place.
Interdental fixation devices are effective in restoring a broken jawbone and keeping it fixed in place after an injury.
How is the Procedure Performed?
The specific method used in applying interdental fixation devices tends to vary depending on the device being used.
For arch bars, the following steps are followed:
- The arch bar is prefabricated based on the patient’s specific needs. Its shape and length can be adjusted, if needed. Doctors make sure the bar adapts closely to the dental arch and should fit between the dental equator and the gingiva without damaging the gingiva.
- The bar is then trimmed. Doctors make sure it does not extend past the most distal tooth. This makes sure the patient will not experience any discomfort or irritation once the device is in place.
- The bar is positioned symmetrically to achieve calculable tension forces.
- A ligature is prepared in the premolar region.
- The arch bar is fixed using a wire twister.
- The wire is cut and the ends are turned away from the gingiva.
- The wire loop is placed over the maxillary and mandibular parts of the bar. It is then tightened.
- Wire fixation using at least three wires completes the procedure.
- Patients are then asked to use postoperative training elastics, especially if they suffer from condylar fractures.
For IMF screws, the following steps are performed:
- The doctor first checks the position of the tooth roots and nerves.
- In applying interdental fixation devices, the screws should be positioned asymmetrically from jaw to jaw. Doctors also make sure it does not interfere with the operative approach or existing internal fixation devices.
- The doctor determines the most appropriate screw placement pattern to use. This is based on the location of the fracture.
- The screws are then directly introduced into the mucosa. The doctor makes sure the screw head does not compress the gingiva.
- Two or more IMF screws are placed on the opposite side of the jaw.
- For mandibulomaxillary fixation, the wire ligature is wrapped around the screw’s head grooves using 0.4mm wires.
- The fixation is adjusted to achieve the correct occlusion.
- The wires are then tightened.
- Additional wiring in an X pattern is then added for greater stability.
Possible Risks and Complications
Tooth-borne fixation devices are associated with several potential problems, such as:
- Poor oral hygiene
- Extrusion of teeth
- Loss of tooth vitality
- Ulcers of the buccal and labial mucosa
Bone-borne fixation devices, on the other hand, are associated with fewer risks, but they have to be applied properly to achieve good stability. IMF screws, for one, may not be so stable because of the elastic wires that are used to support them. Also, when the wires are tightened too much, it can cause the fragment to rotate in a lateral direction.
“Coding for Trauma and Fractures.” American Association of Oral and Maxillofacial Surgeons. http://www.aaoms.org/images/uploads/pdfs/traumaandfractures.pdf
Sahoo NK, Mohan R. “IMF Screw: An ideal intermaxillary fixation device during open reduction of mandibular fracture.” J Maxillofac Oral Surg. 2010 Jun; 9(2): 170-172. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3244099/