The objective of this study was to investigate the incidence of sensory impairment of the lingual nerves following lower third molar removal and to compare the outcome with various operative variables. A total of 1200 mandibular third molars were removed under local anaesthesia. Predictor variables were categorized as lingual flap retraction, tooth sectioning, and buccal guttering. The outcome variable was the presence or absence of lingual nerve impairment. Different operative techniques were performed to identify independent predictors. Of the 1200 patients, 67 (5.6%) experienced transient sensory impairment at the 1-week follow-up. In all cases this resolved completely during the study period, except for four (0.3%) patients who suffered permanent impairment of lingual nerve function. Factors that predicted lingual nerve injury were lingual flap retraction, tooth sectioning, and buccal guttering. The incidence of lingual nerve injury was greater when combinations of these operative variables were used.
Impacted mandibular third molar teeth are in close proximity to the lingual, inferior alveolar, mylohyoid, and buccal nerves. The most serious and often discussed postoperative complication that arises from third molar surgery is trigeminal nerve injury, specifically with involvement of either the lingual or inferior alveolar nerve. The majority of injuries result in transient sensory disturbances, but in some cases permanent paraesthesia (abnormal sensation), hypoaesthesia (reduced sensation), or, even worse, some form of dysaesthesia (unpleasant abnormal sensation) can occur. Sensory loss lasting longer than 6 months is mostly permanent. The subsequent distorted sensory sensation can result in significant impairment in speech and chewing, and taste loss from the ipsilateral anterior segment of the tongue, which has a negative impact on socializing and the patient’s psychological well-being.
These nerves can be damaged as a result of direct or indirect forces. Due to the anatomical location of the nerve, direct trauma to the lingual nerve may occur during various surgical procedures, e.g. those carried out for the management of trauma, cysts, tumours, and pre-prosthetic problems, orthognathic surgery, damage caused by the use of instruments, and most commonly removal of the third molars. Indirect injury to the nerves can also be a result of physiological phenomena, including pressure from hematomas and postsurgical edema.
The overall risk of lingual nerve injury associated with third molar removal ranges from 0.2% (permanent disturbance) to 22% (sensory disturbances in the early postoperative period). The reported rate of permanent lingual nerve injury is generally in the range of 0–2%.
This study sought to identify the incidence of lingual nerve damage following the removal of mandibular third molars.
Materials and methods
The present prospective hospital-based study included 1200 patients who underwent the removal of mandibular third molar teeth under local anaesthesia; both male and female patients were included, and they ranged in age from 18 to 45 years. The study design was quasi-experimental. Patients with any neurological disorder were excluded from the study as they might have unfairly influenced the outcome. The third molar on only one side was removed for each patient. All mandibular third molar surgeries were performed by a senior surgeon with more than 5 years of experience. Ethical clearance was obtained for this clinical study.
Prior to surgery, a panoramic and intraoral peri-apical radiograph was taken. Assessment of the impacted tooth was done for determination of the angulation and of the position of the tooth in relation to the ramus of the mandible and the second molar (based on Winter’s classification and the Pell and Gregory classification ; Table 1 ). Mandibular third molar teeth with a class III relation and position C depth were not included in the study. Prior to the procedure, the patients were informed of the possible outcome in their own language and written consent was obtained. At 1 week following surgery (at the time of suture removal), the patient was questioned regarding any alteration in sensation and underwent a clinical examination.