Impacted mandibular third molars are one of the most commonly performed oral and maxillofacial surgical procedures.[1] The treatment is recommended for recurrent pericoronitis, caries, periodontal pathology, and other complications that can cause postoperative neurosensory disturbances, such as injury to the inferior alveolar nerve (IAN).[2] This type of injury may result in abnormalities of sensation, numbness, or dysesthesia of the lower lip and chin, which could interfere with activities of daily living and quality of life.[3] This varies depending on the relationship of the roots of the tooth to the mandibular canal, the depth and angle of impaction, and the surgical approach used. Therefore, reducing nerve injury is a prime concern in choosing a suitable treatment for the extraction of mandibular third molars. [4, 5]

The incidence of IAN dysfunction after removing third molars is highly variable according to patient selection, radiographic risk factors, surgical complexity, and the type of measurement for sensory function.[6] In 2023, an IAN injury was reported in 3.9% of the 539 impacted mandibular third molars in a retrospective cohort study. The teeth with osseous impaction showed the highest incidence (7.18%), and those with higher root contact with the inferior alveolar canal also had a higher risk. These results highlight the importance of both anatomy and complexity of surgical removal in nerve dysfunction.[7]

Pre-operative evaluation of the relationship of the mandibular third molar with the inferior alveolar canal is crucial to determine high-risk cases and to plan the surgery. In patients with radiographically identified risk features, a pooled IAN injury risk of 9.52% (95% CI 7.18–12.53%) was reported in a systematic review and meta-analysis that was published in 2026.[8] In selected high-risk cases, the risk of IAN injury was 14.76% (95% CI 11.37–18.94%). A lack of separation of the mandibular canal from adjacent structures was particularly associated with an increased risk. These facts emphasize the need for proper imaging, patient selection, and controlled bone removal to minimize postoperative neurosensory complications.[9]

The two popular methods for impacted removal of mandibular third molars are the lingual split and the buccal trough.[10] The 'lingual split' technique is a controlled split of the lingual aspect of the mandible to allow for removal of the tooth, while buccal troughing is the removal of the buccal bone in order to elevate and deliver the tooth.[11] Both methods seek to provide good access with less removal of unwanted bone and trauma to surrounding structures.[12] Their effects on nerve function, however, may vary depending on tooth morphology, the amount of bone that was removed, the direction of the force, and the position of the tooth compared to the mandibular canal.[12]

Although there has been a good progression in the development of preoperative images and the planning of the surgery, there are not a lot of direct comparisons of the inferior alveolar nerve dysfunction after the lingual split and buccal troughing methods, especially in a local clinical setting. Standardized pre- and post-surgery neurosensory assessment could be utilized in comparative evaluation to identify if either technique is associated with a lower incidence of neurosensory disturbance. Hence, the present study was conducted to compare the prevalence of inferior alveolar nerve dysfunction after surgical extraction of impacted mandibular third molar using lingual split approach versus buccal troughing approach. The findings could help support evidence-based surgical decision-making, patient pre-operative counseling, and efforts to reduce nerve-related complications.

The study was carried out with a comparative analytical study design at the Armed Forces Institute of Dentistry (AFID), Rawalpindi, Pakistan, in the Department of Oral and Maxillofacial Surgery. The study was conducted for six months, from February 2026 to July 2026, and involved comparing the lingual split technique with the buccal troughing method for the surgical extraction of impacted mandibular third molars, in terms of inferior alveolar nerve (IAN) dysfunction. A sample of 150 patients was established, 75 in each of the lingual split group and the buccal troughing group. The number of students in the study was determined to be reasonable for the six-month study duration. This study was designed to assess the incidence of postoperative inferior alveolar nerve dysfunction in the two procedures. Non-probability consecutive sampling was used to recruit eligible patients presenting to the department during the study period. Patients were randomized to either the lingual split or buccal troughing group by the surgical technique chosen by the operating surgeon based on clinical and radiographic examination. The sample sizes of the two groups were to be matched. Patients aged 18–40 years of either sex who required surgical removal of an impacted mandibular third molar and had normal preoperative sensation in the distribution of the inferior alveolar nerve were included. Patients with pre-existing sensory abnormalities of the lower lip or chin, previous surgery or trauma to the mandibular nerve, any mandibular pathology requiring extensive surgery, systemic or neurological disorders that may compromise sensory function, or incomplete assessment of follow-up were excluded. Demographic and clinical data were obtained following approval from the institutional ethical review committee and informed written consent of each participant, and were recorded on a structured proforma. The variables collected were age, sex, medical history, impacted side, angulation and depth of the impacted tooth, radiographic relationship of the roots of the impacted tooth to the mandibular canal, surgical technique, and surgery duration. Preoperative radiographs were examined to evaluate the relationship between the impacted tooth and the mandibular canal, and the panoramic radiographs and cone-beam computed tomography (CBCT) when indicated. Patients were split into two groups based on the method by which the tooth was removed. In the lingual split group, the bone was controlled split into the lingual aspect of the bone to help remove the impacted tooth. For the buccal troughing group, the bone in the buccal area was removed to allow for adequate space for tooth elevation and delivery. Other surgical procedures such as flap design and irrigation were recorded, and tooth sectioning (if necessary) and wound closure were also recorded. They were carried out by experienced OMF surgeons who followed conventional surgical techniques. Standardized clinical neurosensory examinations were used to evaluate inferior alveolar nerve function pre-operatively and at follow-up after surgery. These consisted of light-touch sensation, pinprick discrimination, and two-point discrimination of the lower lip and chin on the operated side, compared to the other side. Inferior alveolar nerve dysfunction was defined as a new postoperative alteration or loss of sensation in the distribution of the nerve compared with the preoperative assessment. The main outcome was the incidence of IAN dysfunction after surgery in each surgical group. Patients were evaluated at 1 week, 1 month, and 3 months post-surgery to identify and report sensory abnormalities and their improvement. Temporary dysfunction was defined as sensory impairment that resolved during follow-up; persistent dysfunction was defined as impairment that was detected at the last three-month evaluation. Data were analyzed using IBM SPSS Statistics, version 26. The quantitative data such as age and duration of surgery were presented as mean±standard deviation. Categorical variables such as sex, type and depth of impaction, surgical technique, and occurrence of IAN dysfunction were presented as their frequency and percentage. Comparisons of the frequency of IAN dysfunction between the two groups were performed using the chi-square test and Fisher's exact test. An independent-samples t-test was applied to compare continuous variables, depending on their distribution. Age, sex, impaction characteristics, radiographic proximity to the mandibular canal, and duration of surgery were also evaluated for possible association with IAN dysfunction. A p-value of less than 0.05 was considered statistically significant.

A total of 150 patients were included in the study, with 75 patients in each surgical group. The mean age was 27.8 ± 5.6 years in the lingual split group and 28.4 ± 5.2 years in the buccal troughing group. There were no statistically significant differences in the demographic and baseline clinical characteristics, including age, sex, side of impaction, angulation, impaction depth, and proximity of the impacted tooth to the mandibular canal between the two groups (p > 0.05). (Table 1).

Table 1. Demographic and baseline characteristics of patients

The mean surgical time was shorter in the lingual split group (24.6 ± 7.2 minutes) than in the buccal troughing group (29.1±8.1 minutes; p < 0.001). There were no significant differences among tooth sectioning requirements, flap design, or surgeon category (p > 0.05). At 3 months, the follow-up completion rate was >94% for both groups. (Table 2).

Table 2. Surgical characteristics and duration of surgery

Postoperative inferior alveolar nerve (IAN) dysfunction was more frequent in the lingual split group at all follow-up intervals, although the differences were not statistically significant. Dysfunction at one week was noted in 12.0% of patients in the lingual split group and 8.0% of patients in the buccal troughing group, with no difference between the two (p=0.42). The frequency was reduced gradually and amounted to 2.7% and 1.3%, respectively, at 3 months (p =0.56). Likewise, the differences in light-touch sensation, pinprick sensation, and 2-point discrimination were not statistically significant (p > 0.05). (Table 3).

Table 3. Comparison of postoperative inferior alveolar nerve dysfunction

The radiographic proximity to the mandibular canal (p = 0.03) was found to be statistically significant with regard to all three cases of IAN dysfunction, which were present in patients with high-risk radiographic features, at three months. Surgical technique (p = 0.08), age (p > 0.05), sex (p > 0.05), and duration of surgery (p > 0.05) were not significantly associated with persistent dysfunction. (Table 4).

Table 4. Factors associated with IAN dysfunction at three months

The present study compared postoperative inferior alveolar nerve (IAN) dysfunction following surgical removal of impacted mandibular third molars using lingual split and buccal troughing techniques. IAN dysfunction was observed in 12.0% of patients in the lingual split group and 8.0% in the buccal troughing group at one week, decreasing to 2.7% and 1.3%, respectively, at three months. Although dysfunction was numerically more frequent following lingual splitting, the differences were not statistically significant (p > 0.05). The results are similar to the direct comparison between lingual splitting and buccal guttering in 36 patients conducted by Kharmawlong et al. (2025), who found that the lingual splitting technique had a lower mean operating time, while the buccal guttering technique had a higher mean number of postoperative nerve-related complications. Their study, however, did include specifically impacted third molars and they reported temporary paraesthesias of the lingual nerve, which is not directly comparable to the IAN-specific outcome of the present study.[13] The overall incidence of IAN dysfunction in the present study can also be compared with Kuang et al. (2023) who retrospectively analyzed 539 high-risk impacted mandibular third molars and found that IAN injury occurred in 3.9% of cases. They found that deeper impaction and greater contact between roots and inferior alveolar canal were associated with a greater number of injuries. The present study showed a higher incidence of early postoperative dysfunction, but the percentage who were affected at three months was not high. Variation may reflect the differences in patient selection, anatomical risk and postoperative assessment. Importantly, both studies indicate that the anatomical association of the affected tooth with the mandibular canal should be taken into account when assessing postoperative nerve complications.[7] In a similarly descriptive study, Maqbool et al. (2024) examined 163 patients at Ayub Teaching Hospital, Abbottabad, Pakistan, and found that 1.2% of patients sustained IAN injuries. They found no statistically significant association between nerve injury and age, sex, impaction characteristics, tooth splitting, bone cutting, or surgical duration. They confirmed that most demographic and surgical variables were not associated with their findings, which is similar to the current study. Overall nerve injury rate, however, varied, and these differences should be viewed in light of the case selection and patient numbers in both studies.[12] Cherian et al. (2025) conducted a prospective study of 350 patients, showing neurosensory disturbances after surgery in 10.9%, of which 2.3% had persistent disturbances 1 year after surgery. The results of these studies are fairly similar to the early postoperative dysfunction seen in the present study. Radiographic characteristics like root deflection and the loss of the radiopaque border of the mandibular canal were also shown to be important prognostic factors for postoperative sensory disturbance by Cherian et al. The present study similarly found an association between radiographic proximity to the mandibular canal and IAN dysfunction at three months (p = 0.03). However, there is a limitation in comparing long-term results because of the different lengths of follow-up periods.[14] Yadav et al. (2026) performed another retrospective cohort study that involved 165 impacted mandibular third molars and reported 7.3% of neurosensory deficit symptoms following the surgical removal. They documented relationships with the depth of penetration, angulation with the mandibular canal, and the length of surgery. Similar to the current study, radiologic proximity was also found to be statistically significant, and depth of impaction was associated but not statistically significant (p = 0.08). In contrast, age, sex, and surgical duration were not significantly associated with dysfunction in the present study. This difference could be due to differences in sample characteristics and/or statistical precision. Also, Yadav et al. considered a composite of inferior alveolar and lingual nerve injury, whereas the present study considered a composite of only IAN dysfunction.[15] Thereza-Bussolaro et al. (2026) also suggested a radiographic proximity association, as their systematic review and meta-analysis of 11 studies yielded a pooled IAN injury risk of 9.52%, with a pooled injury risk of 14.76% for selected high-risk patients. The authors noted significant differences based on the position of the mandibular canal, its morphology, and the integrity of the bone overlying the canal. The patients in the present study with three-month dysfunction all had high-risk radiographic features, mirroring the observation of their findings. The limited number of events does, however, not allow for a reliable estimate of the size of this association, and the meta-analysis itself indicated low to very low certainty for the available evidence.[9] In this regard, Robbins et al. (2022) conducted a systematic review of seven randomized controlled trials (RCTs) that compare panoramic imaging with additional cone-beam computed tomography (CBCT) for high-risk third molars of the mandible. In six trials, there was no statistically significant decrease in nerve injury when using CBCT. Although radiographic proximity was associated with IAN dysfunction in the present study, this does not establish that routine CBCT would reduce postoperative complications. The findings, however, reinforce the value of identifying anatomical risk factors at the time of preoperative assessment, and further imaging as indicated clinically.[16] Reia et al. (2021) performed a Systematic Review and Meta-Analysis of CBCT versus panoramic radiography for the prediction of intraoperative IAN exposure. They found CBCT to be more sensitive than panoramic radiography (95.1%) in identifying anatomical relationships that may be significant for surgical planning. This is in line with the significance of X-ray risk assessment as seen in the current study. Prediction of the intraoperative nerve exposure, however, is not the same as prediction of postoperative sensory dysfunction, and superior performance of either imaging technique in minimizing nerve injury cannot be concluded from the present results.[17] Lee et al. (2023) analyzed 27 studies in a systematic review and meta-analysis about the effect of surgical technique on nerve-related complications. They found that there was a higher risk of temporary lingual nerve injury with lingual flap retraction and lingual split techniques, but there was not enough evidence to conclude whether there was permanent injury. The present study noted a higher number of IAN dysfunctions after lingual splitting, but the results should not be interpreted as confirmation of the results found by Lee et al., because these two studies evaluated different nerves. The difference between these, however, is significant and should be evaluated when discussing the neurologic outcome of 3rd molar surgery, as inferior alveolar nerve injury is different from lingual nerve injury.[4] Abu-Mostafa et al. (2021) conducted a systematic review to compare the anatomical risk of coronectomy with the complete extraction of high-risk mandibular third molars, also highlighting the importance of anatomical risk and surgical selection. The authors found temporary IAN injury of 0–2.20% after successful coronectomy versus 0–16.66% after complete extraction and permanent IAN injury of 0–3.63% after extraction. Surgical management and patient risk factors might influence reported nerve injury frequencies, although no evaluation of coronectomy was performed in the present study. The comparison does not allow drawing any conclusions as to the relative effectiveness of splitting in the mouth and in the buccal trough.[18] The present study also found that the mean operative time for lingual splitting was significantly shorter than the mean operative time for buccal troughing (24.6 ± 7.2 versus 29.1 ± 8.1 minutes; p < 0.001). The surgical duration, however, at three months did not have a significant association with the IAN dysfunction (p = 0.12). This is a finding rather than proof that there is a difference in the operative time between the techniques and a difference in neurological outcome. The interpretation should be careful due to the complexity of the impaction, the morphology of the teeth, and the surgical approach used for the patient. The study needs to be interpreted within the following limitations. The study took place at one institution in 75 patients in each surgical group, and technique selection was at the discretion of the clinical and radiographic judgment of the investigator. Therefore, there is residual confounding by anatomical or procedural characteristics that can not be ruled out. There were only three patients with detectable dysfunction at the final assessment, making comparisons and the assessment of associated factors less precise. Follow up was limited to three months, and thus, dysfunction at three months is not considered to be permanent. In addition, the final estimates may have been impacted by incomplete follow-up. Comparisons would be more meaningful if larger prospective studies with appropriate adjustment for baseline surgical risk, standardized neurosensory assessments and longer follow up were available. Overall, the present study found no statistically significant difference in postoperative IAN dysfunction between the lingual split and buccal troughing techniques. Operative duration was correlated with lingual splitting; and at 3 months, dysfunction was correlated with radiographic proximity to the mandibular canal. The results presented here should be regarded as preliminary comparative results and not as proof of the equivalence or superiority of both surgical procedures in the central nervous system.

The present study found no statistically significant difference in postoperative inferior alveolar nerve dysfunction between lingual split and buccal troughing techniques for impacted mandibular third molar removal. Lingual splitting was significantly correlated with a shorter operative duration; however, there was a gradual improvement in sensory disturbances in both techniques during the three-month follow-up. Radiographic proximity to the mandibular canal was significantly associated with dysfunction at three months.