Causes, prevention, and management of inferior alveolar nerve injury during implant dentistry

Although implant dentistry has become widely accepted to restore esthetics and function of teeth, it is not without risks. One serious complication that can occur is alteration of sensation due to nerve injury. Some reports place this occurrence as high as 13%. For dental practitioners, thorough understanding of anatomy, surgical procedures, and implant systems along with proper planning of treatment are essential to reduce this complication.

An article in the current issue of the Journal of Oral Implantology provides an overview of causes, prevention, and management of inferior alveolar nerve injury. This nerve is a branch of the nerve in the jaw that contains both sensory and motor fibers.

Injury to the inferior alveolar nerve can cause alteration of sensation in varying degrees from mild numbness to loss of pain sensation to complete loss of perception of stimulation. The condition usually improves in a few months, but in some cases it can be permanent.

The authors note that proper localization of the nerve before the procedure is an essential preventive step. Conventional radiography is most commonly used, but tomography and computerized tomography and even surgical exposure are also options.

Additionally, practitioners should perform standard neurosensory examinations, before and after treatment, to determine any degree of change in sensation. Many of these are simple tests such as the patient determining the location of a light touch to the face or the direction of a brush's movement, or feeling heat and cold.

Severe nerve injuries are often the result of drilling too deep—past bone into the nerve—or placing the implant itself upon a nerve. Accurate measurement of the available bone or the use of a drill guard can prevent over-penetration. The authors recommend a type of implant that can be removed or unscrewed a few threads after placement to relieve pressure on the nerve.

When injury does occur, determining the cause also determines the response. A radiograph could confirm if the implant was the problem rather than the drilling. Steroids or other anti-inflammatory drugs should be prescribed to control inflammatory reactions. Sensation may return slowly, but if improvement is not observed within two months, the authors state that referral to a microneurosurgeon is necessary. Degeneration of the nerve can take place four to six months after nerve injury, so swift action is essential.