Injuries to peripheral nerves in the jaw and face have been a part of life since the existence of humanity. However, understanding and treating the effects of nerve injuries have not been possible for centuries because of the misinformation about the primary regions of sensory perception in ancient times. Accurate information about the nerve mechanism was obtained through investigations after the world wars. The destructive effects of these injuries began to attract attention especially in the last three centuries; as a consequence, studies were initiated to find effective therapies based on a scientific foundation (Miloro 2013).
Peripheral nerves are the basic connections among the body, brain, and spinal cord. Peripheral axons are found in almost every area of the body, including muscles, connective tissue, skin, and meninges surrounding the brain. The peripheral nervous system separates itself from the central nervous system by consisting of only neurons located in the brain and medulla spinalis. One of these distinctions is that peripheral nerve cells are quite different in terms of their response to injuries and diseases compared to the cells that react to them in the central nervous system. In the neuroscience literature, peripheral nervous system cells are emphasized as neurons that can demonstrate regeneration of axons in response to damage, unlike the central nervous system cells. The presence of axons that can demonstrate regeneration in neuropathies is an important fact. However, this regeneration is rather slow and may never occur if the distances to the target tissues are long (Zochodne 2008).
Nerve injuries formed during oral and maxillofacial surgical operations occur usually by crush or tension-type damages rather than incisions or ruptures (Kalender et al. 2014). Considering this type of injury, a successful functional recovery can be expected with spontaneous regeneration that may occur in the distal nerve stump (SEDDON 1943; Sunderland 1990; Kalender et al. 2014). Such nerve injuries can be treated with pharmacological agents without surgical intervention. The aim of medical treatment is to restore the function of the injured nerves, to shorten the period of regeneration, and to improve the life quality of patients (Cornwall and Radomisli 2000; Er et al. 2016).
Oral and maxillofacial surgeries that are performed especially in the lower jaw including impacted third molar surgery, dental implant applications, cyst or tumor operations, orthognathic surgery, pre-prosthetic surgery, arthroscopic surgery, salivary gland surgery, operations in maxillofacial trauma, and injection injuries can damage the inferior alveolar nerve, mental nerve or lingual nerve by crushing or compressing it (Cornwall and Radomisli 2000; Er et al. 2016; KÜÇÜKKURT et al. 2018). The total percentage of the inferior alveolar nerve and lingual nerve injuries varies between 0.5% and 5% after the extraction of the lower third molar (Swanson 1991; Valmaseda-Castellón et al. 2001; Kanagasabapathy and BrigitEapen 2014). The percentage of lingual nerve injuries has a lower frequency compared to inferior alveolar nerve injuries, with 0.02% to 1% (Renton and McGurk 2001; Kanagasabapathy and BrigitEapen 2014).
As a result of these damages, complaints such as permanent anesthesia, dysesthesia, pain, paresthesia (burning, stinging, numbness or tingling sensation) related to the affected region can be observed (Seo et al. 2018; KÜÇÜKKURT et al. 2018). Generally, spontaneous recovery is observed in most of the patients within 6-8 weeks, but the sensory loss may persist for 6 months or longer, and permanent neuropathic disorders may occur in such cases (Smith and Lung; Pogrel and Kaban 1993; KÜÇÜKKURT et al. 2018).
There are current studies on drugs that are thought to be successful in treating peripheral nerve injuries. However, the studies on the inferior alveolar, mental and lingual nerves are small in number. Current clinical approaches are mostly on systemic applications. The aim of this study was to determine and compare the effects of dexamethasone, B vitamin complex and nerve growth factor (NGF) on peripheral nerve regeneration with a local application on the inferior alveolar nerve.