Glossary

The word “necrosis” originates from the Greek word νέκρωσης, which refers to the act of death or decay. In the English language, necrosis is the result of cell injury that causes the premature death of living tissue cells via autolysis, or in simpler terms, the death of body tissue. When too little oxygenated and nutrient-rich blood reaches tissue, it begins to go through autolysis, or the process of self-digestion by its own enzymes. Necrosis can be caused by exposure to chemicals, radiation, and injury, and cannot be reversed. Once begun, tissue death can only be stopped — the destroyed tissue won’t regenerate without the help of a grafting procedure. In implant dentistry, necrosis of the jaw is a common obstacle to implant procedures. Tooth loss, periodontal disease, and other conditions can cause or contribute to the loss of bone in the jaw. A bone graft may be needed to support an implant.

In medical terminology, neoplasia is described as abnormal tissue growth as a result of the rapid division of mutated cells. Normally, the body’s cells multiply, divide, and extinguish in an orderly manner. Although cells normally divide quickly when the human body is growing, when it reaches adulthood, cells typically only do this as needed when cells die or become injured and require replacement. This is regulated by the body’s unique genetic code contained within the DNA. Neoplasms, or the abnormal tissue that is the result of neoplasia, are often seen in various forms of cancer as a malignant growth. The cells within a neoplasm have mutated and no longer respond to the instructions given by host DNA. They multiply rapidly and don’t die when they ought to, resulting in the unregulated growth of abnormal tissue — in other words, a tumor. While neoplasms are frequently seen with malignancy, they can also be benign or precancerous.

Nerve lateralization, also known as nerve repositioning or nerve transpositioning, is a surgical procedure whereby the course of the inferior alveolar nerve is redirected to allow the placement of longer implants in a mandible with extensive resorption of the posterior ridge. Nerve repositioning requires a portion of the lower jaw be opened to provide access to the nerve. To close this access, a bone graft is required following the placement of the implants. Nerve lateralization is considered a more aggressive procedure in implant surgery as the nerve can sustain long-term or even permanent damage. The inferior alveolar nerve provides feeling and sensation to the lower jaw, lip, and chin and most patients experience varying degrees of numbness following the surgery. Since there are other options for implant placements, such as blade implants, nerve repositioning surgery is generally not the first choice when dealing with patients with extensive posterior ridge resorption.

Nerve repositioning, also known as nerve lateralization or nerve transpositioning, is a surgical procedure whereby the course of the inferior alveolar nerve is redirected to allow the placement of longer implants in a mandible with extensive resorption of the posterior ridge. Alveolar nerve repositioning may also be done as part of a procedure to remove cysts or benign tumors of the mandible. For implant patients experiencing edentulous atrophy in posterior mandibles, repositioning of the alveolar nerve is often the only way a fixed prosthesis or implant can be properly placed. Due to the risks involved in repositioning the alveolar nerve, extreme care and precision must be demonstrated during surgical procedures to avoid damage to the nerve. Damage can cause short-term, long-term, or permanent issues and impair a patient’s ability to experience sensory information. It can also cause pain, numbness, and in some cases, paralysis. Nerve repositioning is done if there are not other suitable implant placement options.

Neurapraxia is the name given to a mild nerve injury that has been caused by either compression or retraction. In neurapraxia, there is no violation of the nerve trunk and no axonal degeneration and spontaneous recovery of the motor and/or sensory functions most often occurs within one to four weeks from the time of injury. Neurapraxia in dentistry is commonly caused by an injury to the inferior alveolar nerve or to the lingual nerve and may occur due to several possibilities including third molar extractions, anesthetic injections, oral disease, and surgical, orthodontic, and endodontic treatments or procedures. Neurapraxia symptoms include numbness, loss of sensation, motor paralysis, and tingling. Though neurapraxia typically does not require any specific treatment, patients should report their symptoms to their practitioner for monitoring and follow-up. In some cases, additional imaging may be needed to ensure there is not another underlying cause for the neurapraxia that must be addressed to promote healing.

Neurotmesis is a nerve injury involving a complete severance of the nerve trunk leading to Wallerian degeneration. Due to the severing of the nerve trunk, sensory and/or motor functions are impaired with the potential for recovery being very small. In implant dentistry, neurotmesis may be caused by an accidental incision of the nerve or any of the factors leading to axonotmesis. Neurotmesis may be caused in several different ways during a surgical procedure. First, the needle used in the injection of numbing medications prior to the surgery can nick, damage, or lacerate the nerve trunk. In addition, the medication itself may cause chemical damage if it is injected directly into the nerve. During the surgery itself, the nerve and/or nerve trunk may also be damaged due to excess movement or manipulation or through compression. A direct surgical mistake which leads to the severe laceration or severing of the nerve trunk can also be the cause of neurotmesis.