DCA03TM Third Molar Surgery, 5th Edition _____________________________________________________
gual aspect of the impacted third molar is retracted during an extraction (Lin et al., 2023). The dynamics of the LN injury may progress in the following manner: Occasionally, the roots of the distoangular impacted third molar are directed lingually (lingual version). During their development, they can perforate the lingual cortical plate of bone and cause its dehiscence or fenestration. This can make the deficient lingual cortex fragile and easy to fracture with minimal effort (and can occur during the tooth extraction). A deficient lingual plate takes away the osseous barrier and exposes the lingual surface of third molar roots straight to the lingual nerve. Therefore, clinicians can- not depend on the lingual plate of bone to protect the lingual nerve from surgical trauma. If this happens in cases of high lateral position of the LN, the nerve and the tooth come into direct contact. Extraction of the third molar in this situation may dramatically increase the probability of LN stretching and resultant temporary LN injury (neurapraxia, axonotme- sis) or permanent LN injury (neurotmesis) that may not be recognized by the operating surgeon intraoperatively. Statis- tics for permanent injury to the lingual nerve have exhibited variation based upon the population studied. The incidence of injury to the LN following a third molar extraction is rare, with most injuries healing spontaneously and with a range of approximately 0.04% to 0.60% for a permanent injury (Lee et al, 2023). Because the LN can exist at variable levels within the tissue on the lingual surface of the third molars, clinicians must use extreme care when manipulating mucosal tissue dur- ing the extractions of third molars, whether they are impacted or completely erupted. The LN can easily be bruised or even severed during third molar surgery when the tissue on the lin- gual surface is retracted, when the surgical purchase of forceps has inadvertently secured soft tissue, when instruments slip and make contact with the LN, or when a bur used to section a third molar engages the lingual aspect of the soft tissues. If a lingual flap is prepared and retracted during the extraction of a mandibular third molar the incidence of permanent dam- age to the lingual nerve is 0.60% compared to 0.20% when a lingual flap is not utilized. (Zaccheo et al, 2024).
NEUROSENSORY ABNORMALITIES FOLLOWING LOWER THIRD MOLAR SURGERY Two nerves—the inferior alveolar nerve (IAN) and lingual nerve (LN) —are in proximity and could be involved during the extraction of lower third molars (teeth #17 and #32). The IAN is a bilateral nerve positioned inside the body of the mandible in the inferior alveolar canal (IAC). It begins on the internal surface of the ramus and exits at the parasymphyseal area of the mandible as a mental nerve. This sensory nerve supplies the skin of the lower lip and chin, as well as the mucosa of the lower vestibule and teeth, and can be traumatized upon the removal of impacted mandibular wisdom teeth (Loureiro et al., 2020). The IAC curves at the angle of the mandible and can be very close to the impacted mandibular third molar. The approximate location of the IAC can usually be identified on the preoperative panoramic radiograph, and the possibility of nerve injury can and should be discussed with the patient based on this proximity (Choi et al, 2025). A high anatomical position of the IAC, deep (infrabony) impaction of the lower third molar, root apices that are near or below the neurovascu- lar bundle, root dilacerations and ankylosis, and greater bone density increase the risk of nerve injury and postoperative alteration in sensation (Shaukat et al., 2023). The LN cannot be identified on a routine radiograph (only on a specialized CT scan or more easily on an MRI scan) because of its location in the soft tissue on the lingual (tongue) side of the ramus and body of the mandible. It provides an ipsilateral sensation (feeling) to the anterior two-thirds of the tongue, sublingual mucosa, and mandibular lingual gingiva. Through the chorda tympani connection with a facial nerve (parasym- pathetic fibers), the LN is responsible for a taste sensation in the same area. A frequently described intimate proximity of the LN in the retromolar tissue to the impacted third molar and a deficiency of the lingual cortex can place the two structures (the lingual nerve and the mandibular third molar) very close to one another and be responsible for intraoperative nerve injury. RISK FACTORS FOR DAMAGE TO THE LINGUAL NERVE The IAN enters the mandibular foramen and remains within the body of the mandible until it emerges at the mental fora- men at the buccal aspect of the bicuspids. The LN is exterior to the lingual cortical plate of bone in the area of the mandibular third molar and remains embedded in the muscular tissue and the connective tissue in this area. The position and branching of the LN are variable in its relationship to third molars, which further complicates attempts to predict a definitive location. The LN is more prone to trauma when the tissue on the lin-
Self-Assessment Question 2
2. The lingual nerve: A) Can be identified on a routine panoramic radiograph. B) Provides ipsilateral sensation to the anterior two-thirds of the tongue. C) Lies interior to the lingual cortical plate. D) Has a definitive relationship relative to the mandibular third molars.
130
EliteLearning.com/Dental
Powered by FlippingBook