CBCT radiological features as predictors of nerve injuries in third mandibular molar extraction

Aim: The surgical extraction of impacted mandibular third molars exposes the patient to the risk of periphereal neurological injuries. The rst aim of this work was to study the distribution of radiographic proximity of the third molar to the inferior alveolar canal, considering Maglione’s Classi cation, in a population at risk. The second aim was to evaluate the in uence of speci c factors (age, gender, operator experience, duration of surgery, depth of impaction, absence of corticalization) on the development of neurological complications. Methods: This prospective observational cohort study was conducted on 378 patients, undergoing third mandibular molar’s extraction, in a year’s time. The patients were informed about the study procedure and informed consent was obtained. Surgical procedures were performed in a standardized way, using the same surgical and pharmacological protocols. Each patient underwent rst radiologic investigations (OPT and/or intraoral radiography) and 193 patients underwent CBCT scan, because of diagnostic suspect of NAI proximity. Preoperative and postoperative data were collected. The patients were visited again for suture removal after seven days and postoperative neurological disorders were investigated. A therapy with ALAnerv® was prescribed and a thorough follow up at 14 days was applied in order to monitor the development of symptoms until the eventual resolution. At the end of one year period, data collected were statistically processed using the Pearson chi-square test for evaluating variables distributions within the population with paresthesia with respect to patoents without complications. Results: Results showed a signi cant prevalence of teeth belonging to 3a and 3b classes, according to Maglione classi cation, in which the mandibular canal runs touching the tooth apically or buccally. 12 patients (3.17%) developed a neurological complication. 1 patient (0.26%) showed a permanent NAI paresthesia. 6 patients (1.58%) suffered IAN complications, 4 patients (1.06%) LN complications, 1 patient (0.26%) IAN and LN complications, 1 patient LN and BN complications. 1 patient showed dysesthetic symptoms in the region innervated by IAN. Third molar’s lingual position in close contact with IAN (classes 4a and 4b) was correlated with increased risk of paresthesia. Age older than 25 years was statistically associated to neurological risk, probably due to the differences in bone biodynamics and regenerative capacity of nerve trunks in youth age. A statistically signi cant correlation was noted between longer duration of surgery procedures and neurological injuries. Operative time could in uence postoperative edema and could be directly proportional to the intrinsic dif culty of surgical extraction. Conclusions: Classes 4a and 4b of Maglione’s classi cation, age older than 25 years and operative duration longer than 30 minutes represent indicators of increased risk for neurological complications in mandibular third molar surgery.