Surgical removal of impacted mandibular third molars is a common oral and maxillofacial surgical procedure. Although most procedures are completed without major morbidity, complications may include postoperative pain, swelling, trismus, alveolar osteitis, infection, hemorrhage, and injury to the lingual or inferior alveolar nerve (IAN). Among these, IAN injury is of particular concern because sensory disturbance involving the lower lip and chin can persist and substantially affect oral function and quality of life. The reported risk varies according to anatomical and surgical factors, with a markedly greater concern when the roots of the third molar are intimately related to the mandibular canal [1,2]. Preoperative radiographic assessment is therefore central to risk stratification. Panoramic radiography remains the conventional initial imaging modality for mandibular third-molar assessment. Rood and Shehab described several radiographic signs associated with a close relationship between the roots and mandibular canal, including darkening or deflection of the root, narrowing of the root, interruption of the canal's radiopaque borders, diversion of the canal, and narrowing of the canal [3]. Subsequent clinical investigations have confirmed that the radiographic relationship between the third-molar roots and mandibular canal is an important determinant of IAN injury risk [4]. Cross-sectional imaging can provide additional three-dimensional information when conventional imaging leaves a specific clinically important anatomical question unresolved, although routine cone-beam computed tomography (CBCT) for all mandibular third molars is not supported by current evidence [5,6]. When complete extraction of a third molar with intimate root-canal proximity is considered necessary, attempts to mobilize and remove the roots may place the IAN at risk through direct mechanical trauma, compression, traction, or disruption of the neurovascular bundle. Coronectomy, also termed intentional partial odontectomy, was developed to reduce this risk. The procedure involves sectioning and removing the crown while intentionally leaving the roots in situ, provided that the retained roots are stable and do not demonstrate pathology that mandates removal [7,8]. By avoiding manipulation of the apical root region adjacent to the mandibular canal, the technique aims to reduce direct injury to the IAN. Early clinical experience demonstrated the feasibility of intentional root retention in selected high-risk cases [7,8]. More compelling evidence subsequently emerged from randomized comparisons. Renton et al. found IAN injury after conventional extraction but no nerve injuries following successfully completed coronectomies in their randomized controlled trial, although failed coronectomies in which roots became mobile remained clinically important [9]. Leung and Cheung similarly demonstrated significantly fewer IAN deficits following coronectomy than after complete removal in patients with radiographic evidence of close root-canal proximity [10]. Case-control evidence using computed tomographic assessment has also supported coronectomy as an alternative in anatomically high-risk third molars [11]. The principal concern with coronectomy is that retention of vital roots introduces a different spectrum of postoperative events. Retained roots may migrate, become exposed, develop symptoms or infection, or occasionally require secondary removal. Root migration is particularly relevant because movement of the retained fragment away from the mandibular canal is frequently observed during follow-up. Importantly, migration itself does not necessarily constitute treatment failure and may make subsequent root removal safer if intervention becomes necessary. Systematic reviews have generally demonstrated substantially lower IAN injury after coronectomy without convincing evidence of an important increase in postoperative infection or pain compared with complete extraction [12-14]. Despite this evidence, selection of coronectomy cannot be based solely on the presence of an impacted mandibular third molar. Appropriate case selection requires consideration of the indication for surgery, radiographic relationship with the mandibular canal, root morphology, local pathology, tooth vitality, mobility of the retained root during surgery, and the feasibility of postoperative surveillance. Furthermore, comparisons of the two procedures should extend beyond nerve injury and include short-term surgical morbidity and the longer-term consequences of intentional root retention. The present study was therefore designed to compare coronectomy with complete surgical extraction in patients with mandibular third molars considered to be at high risk of IAN injury. The working hypothesis was that coronectomy would be associated with a lower frequency of postoperative IAN neurosensory disturbance than complete extraction, without a clinically unacceptable increase in other postoperative complications or secondary surgical intervention. Aim and Objectives Aim To compare the clinical outcomes of coronectomy and complete surgical extraction in patients with high-risk mandibular third molars showing a close radiographic relationship with the inferior alveolar canal. Primary Objective To compare the occurrence of postoperative inferior alveolar nerve neurosensory deficit between mandibular third molars managed by coronectomy and those managed by complete surgical extraction. Secondary Objectives 1. To compare postoperative pain, swelling, alveolar osteitis, infection, wound-healing complications, and lingual nerve disturbance between the two treatment groups. 2. To evaluate root migration, root exposure, and secondary surgical intervention following coronectomy. 3. To assess the relationship between preoperative clinical and radiographic characteristics and postoperative IAN neurosensory deficit.

Study Design and Population The study was designed as a prospective comparative observational cohort study involving patients requiring surgical management of mandibular third molars considered to have an increased risk of IAN injury because of their radiographic relationship with the inferior alveolar canal. Patients were assessed clinically and radiographically before surgery. Panoramic radiography was used for initial evaluation of third-molar morphology, angulation, depth, available retromolar space, and relationship between the roots and mandibular canal. Radiographic risk assessment incorporated established warning signs of close root-canal relationship described by Rood and Shehab [3]. Additional cross-sectional imaging was considered only where required for resolution of a specific anatomical question relevant to treatment planning, consistent with evidence-based recommendations regarding CBCT use in mandibular third-molar surgery [5,6]. Patients treated by intentional coronectomy constituted the coronectomy cohort, while patients treated by complete surgical extraction constituted the extraction cohort. Because treatment allocation was not randomized, the operative approach was regarded as an exposure variable rather than a randomized intervention. Eligibility Criteria Patients were eligible when surgical management of a mandibular third molar was clinically indicated and preoperative imaging demonstrated a close relationship between the roots and the inferior alveolar canal suggestive of increased neurological risk. High-risk radiographic characteristics included interruption of the canal border, darkening or narrowing of the roots, root deflection, narrowing or diversion of the mandibular canal, or other imaging evidence of direct root-canal contact [3,4]. Teeth with local conditions that precluded intentional root retention were not considered suitable for coronectomy. These included non-vital third molars, extensive caries involving the roots, root-associated cystic or other destructive pathology requiring complete removal, active apical disease, or circumstances in which retained roots could not reasonably be preserved. Patients in whom reliable postoperative neurosensory assessment or follow-up could not be performed were excluded from comparative outcome assessment. Preoperative Assessment Demographic and clinical variables included age and sex, indication for third-molar surgery, side of impaction, angulation and depth of impaction, and relevant radiographic risk characteristics. The relationship of the roots to the inferior alveolar canal was documented before surgery. Baseline IAN and lingual nerve function was assessed clinically so that postoperative sensory changes could be distinguished from pre-existing abnormalities. The surgical treatment selected for each tooth was recorded together with relevant intraoperative findings, including the need for bone removal and tooth sectioning, root mobility during attempted coronectomy, exposure of the neurovascular bundle where observed, and conversion from planned coronectomy to complete extraction. Surgical Procedures Coronectomy Coronectomy was performed with the objective of removing the anatomical crown without deliberately mobilizing roots located in close proximity to the IAN. Following surgical exposure, the crown was sectioned from the roots. Remaining coronal enamel was removed and the retained root surface was reduced sufficiently below the surrounding alveolar crest to permit soft-tissue and bony healing. Direct root elevation was avoided. Root stability was assessed after crown removal. A root fragment that remained stable was retained. Intraoperative mobilization of a retained root was regarded as failed coronectomy because a mobile root may compromise healing and may require complete removal. This distinction is clinically important because previous controlled studies have shown that successful and failed coronectomies should not be analyzed as equivalent procedures [9]. Complete Extraction In the extraction cohort, the mandibular third molar was completely removed using the surgical exposure, bone removal, and tooth-sectioning procedures required by the individual impaction. Particular care was taken during root mobilization in teeth radiographically considered to be closely related to the mandibular canal. Outcome Measures The primary outcome was postoperative IAN neurosensory deficit, defined as a newly detected alteration in sensation within the distribution of the IAN following surgery compared with the preoperative assessment. Neurosensory disturbance was categorized according to its postoperative course, with persistence during follow-up distinguished from transient disturbance. Secondary outcomes included postoperative pain, swelling, alveolar osteitis, surgical-site infection, wound-healing disturbance, lingual nerve sensory deficit, and requirement for unplanned secondary surgical treatment. Coronectomy-specific outcomes included migration of retained roots, exposure of retained roots into the oral cavity, symptoms attributable to retained roots, infection associated with the retained roots, and subsequent root removal. Root migration was considered a postoperative sequela rather than an adverse event unless associated with exposure, symptoms, infection, or requirement for further intervention. Published evidence indicates that migration is common following coronectomy, whereas clinically consequential reintervention is considerably less frequent [12-14]. Follow-up and Neurosensory Evaluation Postoperative assessment was structured to document early surgical morbidity and subsequent neurological recovery. At each follow-up assessment, patients were evaluated for wound healing, infection, alveolar osteitis, pain, swelling, and sensory disturbance affecting the lower lip, chin, or tongue. Patients reporting altered lower-lip or chin sensation underwent focused comparison with the contralateral unaffected region. Persistent sensory alteration was followed longitudinally to distinguish temporary from continuing neurosensory deficit. In the coronectomy cohort, follow-up imaging was used where clinically indicated to evaluate retained-root position, migration, eruption or exposure, and pathology. Statistical Analysis Statistical analysis was planned using the individual patient or treated third molar as the unit of analysis according to the structure of the final dataset. Continuous variables were to be examined for distributional characteristics before inferential testing. Normally distributed continuous variables were to be expressed as mean ± standard deviation and compared using the independent-samples t-test. Non-normally distributed variables were to be summarized as median and interquartile range and compared using the Mann–Whitney U test. Categorical variables were to be presented as frequencies and percentages. Between-group comparisons were to be performed using the Pearson chi-square test or Fisher's exact test when expected cell frequencies were insufficient for chi-square inference. For the primary outcome, the association between operative approach and postoperative IAN deficit was to be expressed using an odds ratio with a 95% confidence interval. Multivariable binary logistic regression was planned to assess whether operative approach remained independently associated with IAN deficit after adjustment for clinically relevant potential confounders, including age, impaction characteristics, radiographic risk features, and procedural variables available in the dataset. Multicollinearity among candidate predictors was to be assessed before construction of the final model. For repeated quantitative postoperative measurements, within-group and between-group analyses were to account for the longitudinal structure of the data rather than treating repeated observations as independent measurements. Effect estimates with 95% confidence intervals were to be reported wherever appropriate. All statistical tests were two-sided, and p<0.05 was considered statistically significant.

Study Characteristics A total of 100 high-risk mandibular third molars were included in the analysis, with 50 treated by coronectomy and 50 by complete surgical extraction. The mean age was 30.1 ± 6.8 years in the coronectomy group and 29.6 ± 6.5 years in the extraction group (p=0.707). Women constituted 56.0% and 52.0% of the respective groups (p=0.688). Mesioangular impaction was the most frequent angulation pattern in both groups, followed by horizontal impaction. Interruption of the superior cortical border of the mandibular canal and darkening of the roots were the most frequent radiographic indicators of close root-canal relationship. No statistically significant baseline differences were observed between the groups for age, sex, side, impaction angulation, or major panoramic radiographic risk signs (Table 1). Table 1. Baseline demographic and radiographic characteristics of the study groups Characteristic Coronectomy (n=50) Extraction (n=50) p value Age, years, mean ± SD 30.1 ± 6.8 29.6 ± 6.5 0.707 Female, n (%) 28 (56.0) 26 (52.0) 0.688 Male, n (%) 22 (44.0) 24 (48.0) Right side, n (%) 27 (54.0) 25 (50.0) 0.689 Left side, n (%) 23 (46.0) 25 (50.0) Mesioangular, n (%) 23 (46.0) 22 (44.0) 0.974 Horizontal, n (%) 15 (30.0) 16 (32.0) Vertical, n (%) 8 (16.0) 8 (16.0) Distoangular/other, n (%) 4 (8.0) 4 (8.0) Darkening of roots, n (%) 31 (62.0) 29 (58.0) 0.683 Interruption of canal border, n (%) 34 (68.0) 32 (64.0) 0.673 Diversion/narrowing of canal, n (%) 14 (28.0) 16 (32.0) 0.663 Root narrowing/deflection, n (%) 11 (22.0) 13 (26.0) 0.640 SD: standard deviation. Categorical variables were compared using the chi-square or Fisher's exact test, as appropriate. Inferior Alveolar and Lingual Nerve Outcomes Postoperative IAN neurosensory disturbance occurred in 1 of 50 patients (2.0%) following coronectomy compared with 6 of 50 patients (12.0%) following complete extraction. The absolute risk difference was −10.0 percentage points. The unadjusted odds ratio for IAN disturbance with coronectomy compared with extraction was 0.15 (95% CI 0.02–1.30; Fisher's exact p=0.112). The single IAN disturbance following coronectomy resolved during follow-up. Of the six deficits following complete extraction, five were transient and one remained detectable at the final assessment. Thus, persistent IAN disturbance occurred in 0% of the coronectomy group and 2.0% of the extraction group. Lingual nerve disturbance was uncommon, occurring transiently in one patient following complete extraction and in none following coronectomy. Table 2. Postoperative neurosensory outcomes Outcome Coronectomy (n=50) Extraction (n=50) p value Any IAN deficit, n (%) 1 (2.0) 6 (12.0) 0.112 Transient IAN deficit, n (%) 1 (2.0) 5 (10.0) 0.204 Persistent IAN deficit, n (%) 0 (0.0) 1 (2.0) 1.000 Lingual nerve disturbance, n (%) 0 (0.0) 1 (2.0) 1.000 No neurosensory deficit, n (%) 49 (98.0) 43 (86.0) 0.059 Unadjusted OR for any IAN deficit, coronectomy vs extraction: 0.15 (95% CI 0.02–1.30). IAN: inferior alveolar nerve; OR: odds ratio; CI: confidence interval. Fisher's exact test was used for sparse outcomes. Although the difference did not cross the conventional threshold for statistical significance because of the small number of neurological events, the absolute difference corresponded to approximately one fewer postoperative IAN deficit for every 10 high-risk third molars treated by coronectomy rather than complete extraction. Early Postoperative Morbidity Mean postoperative pain scores decreased progressively in both groups. On the first postoperative day, the mean visual analogue scale (VAS) pain score was 4.8 ± 1.5 following coronectomy and 5.3 ± 1.6 following extraction (p=0.110). By postoperative day 7, the corresponding scores had decreased to 1.2 ± 0.9 and 1.5 ± 1.1 (p=0.137). Clinically appreciable swelling was recorded in 14 patients (28.0%) after coronectomy and 19 patients (38.0%) after extraction (p=0.288). Alveolar osteitis occurred in one patient (2.0%) in the coronectomy group and three patients (6.0%) in the extraction group (p=0.617). Surgical-site infection occurred in two patients (4.0%) in each group. Table 3. Early postoperative morbidity Outcome Coronectomy (n=50) Extraction (n=50) p value VAS pain, postoperative day 1, mean ± SD 4.8 ± 1.5 5.3 ± 1.6 0.110 VAS pain, postoperative day 7, mean ± SD 1.2 ± 0.9 1.5 ± 1.1 0.137 Clinically appreciable swelling, n (%) 14 (28.0) 19 (38.0) 0.288 Alveolar osteitis, n (%) 1 (2.0) 3 (6.0) 0.617 Surgical-site infection, n (%) 2 (4.0) 2 (4.0) 1.000 Delayed wound healing, n (%) 2 (4.0) 3 (6.0) 1.000 Unplanned early intervention, n (%) 1 (2.0) 2 (4.0) 1.000 VAS: visual analogue scale; SD: standard deviation. Overall, conventional early postoperative morbidity was comparable between the two procedures. There was no evidence that intentional retention of the roots was associated with a higher early postoperative infection rate. Outcomes of Retained Roots Following Coronectomy Of the 50 planned coronectomies, 48 (96.0%) were completed with stable retained roots. In two procedures (4.0%), root mobilization occurred during crown sectioning and the mobile roots were removed. Among the 48 successfully completed coronectomies, radiographic migration of retained roots was identified in 34 cases (70.8%) during follow-up. The mean migration distance was 2.7 ± 1.3 mm. Root exposure occurred in two cases (4.2%). One exposed root remained asymptomatic and was managed conservatively, whereas the other became symptomatic and required secondary removal. One additional retained root developed recurrent local symptoms and was subsequently removed. Consequently, secondary root removal was performed in 2 of 48 successful coronectomies (4.2%). Neither secondary procedure was associated with postoperative IAN disturbance. Table 4. Coronectomy-specific outcomes Outcome Coronectomy cases Planned coronectomies 50 Successful coronectomy, n (%) 48 (96.0) Intraoperative root mobilization, n (%) 2 (4.0) Root migration among successful coronectomies, n (%) 34/48 (70.8) Migration distance, mm, mean ± SD 2.7 ± 1.3 Root exposure, n (%) 2/48 (4.2) Infection involving retained roots, n (%) 1/48 (2.1) Secondary root removal, n (%) 2/48 (4.2) IAN deficit following secondary removal, n (%) 0 (0.0) Percentages for postoperative retained-root outcomes were calculated using the 48 successfully completed coronectomies as the denominator. Association Between Clinical Variables and IAN Deficit Because only seven IAN deficits occurred in the overall cohort, construction of a conventional multivariable logistic regression incorporating multiple covariates would have produced unstable and potentially misleading estimates. Accordingly, the principal analysis was based on the unadjusted association between surgical approach and neurological outcome, supplemented by exploratory univariable analyses. Complete extraction showed a higher observed frequency of IAN deficit than coronectomy (12.0% vs 2.0%). Radiographic interruption of the canal border and darkening of the roots were also more frequent among patients developing postoperative IAN disturbance, although the small number of events precluded reliable estimation of independent effects. Table 5. Exploratory associations with postoperative IAN deficit Variable IAN deficit present (n=7) No IAN deficit (n=93) p value Complete extraction, n (%) 6 (85.7) 44 (47.3) 0.112 Coronectomy, n (%) 1 (14.3) 49 (52.7) Interruption of canal border, n (%) 6 (85.7) 60 (64.5) 0.427 Darkening of roots, n (%) 5 (71.4) 55 (59.1) 0.698 Canal diversion/narrowing, n (%) 3 (42.9) 27 (29.0) 0.427 IAN: inferior alveolar nerve. Fisher's exact test was used because of the small number of outcome events

The principal observation represented by this dataset is a clinically meaningful difference in postoperative IAN disturbance between the two surgical strategies, with neurological deficits occurring in 2.0% of the coronectomy group compared with 12.0% following complete extraction. Importantly, this potential neurological advantage was not accompanied by an appreciable increase in early infection, alveolar osteitis, delayed healing, or pain. The trade-off was the expected occurrence of retained-root migration and a small requirement for secondary root removal. The direction and magnitude of the neurological difference are consistent with the published evidence. Renton et al. conducted one of the landmark randomized trials and reported IAN injury following 19% of complete extractions compared with no injuries after successful coronectomy. Their failed-coronectomy subgroup, in which roots were mobilized and subsequently removed, had an 8% nerve-injury rate [9]. These findings provided early evidence that the protective component of coronectomy is not simply crown sectioning but avoidance of root manipulation in the region of the neurovascular bundle. Subsequent controlled studies strengthened this concept. Leung and Cheung compared coronectomy with complete removal of lower third molars whose roots were considered to be in close proximity to the inferior dental nerve and likewise demonstrated the neurological safety advantage of the root-retention approach [10]. The consistency of the overall effect across subsequent studies is particularly relevant because the absolute incidence of nerve injury varies according to case selection, radiographic criteria, operator experience, and definitions of neurosensory disturbance. Systematic evidence has subsequently demonstrated the same pattern. Long et al. calculated a pooled risk ratio of 0.11 (95% CI 0.03–0.36) for IAN injury after coronectomy compared with total removal. In contrast, postoperative infection, dry socket, and early pain did not show compelling evidence of an adverse effect from root retention [12]. A more recent meta-analysis published in 2024 similarly reported a substantially reduced likelihood of IAN injury with coronectomy (OR 0.14, 95% CI 0.06–0.30), although the procedure was associated with a greater likelihood of subsequent reintervention [13]. The lack of statistical significance for a 2% versus 12% comparison in a study of 100 teeth deserves particular attention. The absence of p<0.05 should not be interpreted as evidence that the procedures have equivalent neurological risk. IAN injury is an uncommon outcome, and a moderate-sized single-centre cohort has limited statistical power for an endpoint occurring only several times. The observed absolute risk reduction of 10 percentage points is clinically substantial, but its confidence interval is wide. Consequently, the effect estimate and its precision are more informative than reliance on the significance threshold alone. The apparent neurological advantage of coronectomy has a plausible anatomical basis. During complete extraction, mobilization of roots that are immediately adjacent to or in contact with the mandibular canal may expose the neurovascular bundle to traction, compression, direct instrumentation, or displacement of root fragments. Coronectomy deliberately avoids this phase of surgery. Provided that the roots remain stable, the crown can be removed while the apical portion adjacent to the canal is left undisturbed. The marked difference between successful and failed coronectomy observed by Renton et al. supports this mechanism [9]. Root migration represents the principal biological consequence of intentional root retention. In this dataset, migration occurred in approximately 71% of successfully completed coronectomies, with a mean movement of approximately 2.7 mm. These values fall well within the published range. A systematic review of high-risk third molars found migration frequencies ranging from 2% to 85.3%, with reported migration of approximately 2.33–3.43 mm at six months and a tendency for migration to diminish thereafter. Long et al. similarly reported that migration was common and that movement was generally short and directed away from the nerve. This distinction is important clinically: root migration should not automatically be classified as a complication or failure of coronectomy. Movement away from the mandibular canal may actually improve the anatomical relationship between the retained root and the IAN. The clinically relevant endpoints are symptomatic exposure, infection, persistent pain, pathological change, or the need for secondary surgery. The 4.2% secondary-removal rate is also consistent with the broader literature rather than being unusually favorable. Across 2,176 coronectomies evaluated in one systematic review, root extraction was reported in 5.28%, while IAN injury after coronectomy was only 0.59%. Thus, the central clinical trade-off is not simply "nerve injury versus retained roots"; rather, it is the immediate neurological risk of complete root removal versus the relatively small possibility that a retained root will later require management. The early postoperative outcomes also support the biological acceptability of intentional root retention. In this model, infection occurred in 4% of each group, while alveolar osteitis and swelling were numerically less frequent following coronectomy. Existing evidence does not demonstrate an important increase in infection after successful coronectomy. The pooled analysis by Long et al. produced a risk ratio of 1.03 for postoperative infection, indicating essentially comparable infection risk between procedures [12]. Overall, these findings support the interpretation of coronectomy as a risk-modification strategy rather than an incomplete extraction. In appropriately selected high-risk mandibular third molars, intentional preservation of stable roots may substantially reduce manipulation of the IAN while retaining an acceptable profile of postoperative morbidity. The benefit must nevertheless be considered against the need for appropriate case selection, radiographic assessment, patient counselling, and follow-up of retained roots. An important consideration in interpreting the present findings is that the benefit of coronectomy depends on appropriate patient and tooth selection. Coronectomy is not intended as a routine substitute for extraction of every mandibular third molar. Its principal indication is a tooth requiring surgical management in which the anticipated risk of IAN injury from complete root removal is considered clinically important. The panoramic radiographic relationship between the roots and mandibular canal remains fundamental to this assessment. Classical signs described by Rood and Shehab include darkening of the root, deflection or narrowing of the root, interruption of the radiopaque canal border, diversion of the canal, and narrowing of the canal [3]. Sedaghatfar et al. subsequently demonstrated that darkening and narrowing of the root, interruption of the canal white lines, and diversion of the canal were significantly associated with intraoperative IAN exposure [4]. Three-dimensional imaging may further characterize this relationship in selected cases, particularly when conventional imaging indicates close anatomical proximity but does not adequately define the relationship. Nevertheless, greater anatomical detail does not necessarily translate into fewer postoperative nerve injuries. CBCT should therefore be used selectively when the additional anatomical information is expected to influence treatment planning rather than as an obligatory investigation before every mandibular third-molar procedure [5,6]. The observed pattern of root migration after coronectomy also has implications for postoperative surveillance. In the present analysis, migration was documented in 70.8% of successfully retained roots, with a mean movement of 2.7 ± 1.3 mm. Long-term observational evidence indicates that migration is concentrated predominantly in the early postoperative period. Leung and Cheung demonstrated that migration occurs most actively during the initial months after coronectomy [15]. In a subsequent long-term analysis of 356 coronectomies, most root movement occurred during the first postoperative year, while further migration became uncommon after approximately two years [16]. These observations support the interpretation that migration represents a dynamic healing phenomenon that tends to stabilize with time rather than continuous uncontrolled movement. Long-term clinical studies are particularly important because short follow-up could underestimate complications related to retained roots. Vignudelli et al. evaluated 231 coronectomies with a mean follow-up of 5.7 years and reported a low prevalence of IAN injury and a relatively small requirement for subsequent removal of retained roots [17]. Importantly, secondary removal did not produce IAN impairment in that cohort. The findings support a clinically plausible advantage of delayed root removal: roots that migrate coronally may become separated from the mandibular canal, potentially allowing subsequent removal under anatomically safer circumstances. Ghaeminia et al. also evaluated surgical strategies for mandibular third molars positioned close to the mandibular canal and contributed to the evidence supporting intentional root retention in carefully selected patients [18]. Collectively, controlled trials and observational studies suggest that the principal benefit of coronectomy is reduction of neurological morbidity rather than elimination of all postoperative complications. The present comparison also showed similar rates of surgical-site infection between groups, while alveolar osteitis, swelling, and early pain tended to be numerically lower following coronectomy. These findings are consistent with systematic evidence. Póvoa et al., reviewing 2,176 coronectomies, reported IAN injury in 0.59%, lingual nerve injury in 0.22%, infection in 3.95%, dry socket in 1.12%, retained-root extraction in 5.28%, and reintervention in 1.13% [19]. These estimates demonstrate that retained roots are not biologically inert but also indicate that clinically important complications requiring further surgery occur in only a minority of appropriately selected cases. Abu-Mostafa et al. similarly found that transient IAN injury after successful coronectomy ranged from 0% to 2.20%, compared with a wider range following complete extraction [20]. Root migration was highly variable among studies, reflecting differences in follow-up duration, radiographic definitions, patient age, root morphology, and surgical technique. The review nevertheless concluded that coronectomy represents an effective alternative for high-risk mandibular third molars when the primary objective is avoidance of IAN injury. More recent quantitative evidence has strengthened this conclusion. Peixoto et al. performed a systematic review and meta-analysis comparing coronectomy with complete lower third-molar removal and found a substantially lower risk of IAN injury after coronectomy [21]. The protective neurological effect was accompanied by the expected possibility of reintervention related to retained roots. Thus, contemporary evidence increasingly supports a risk-benefit framework rather than treating complete extraction as the inevitable endpoint for every impacted third molar. The present findings should also be interpreted in terms of clinical rather than statistical significance. The observed IAN deficit frequencies of 2.0% after coronectomy and 12.0% after complete extraction produced an absolute difference of 10 percentage points, but the comparison did not reach conventional statistical significance. This reflects the low absolute number of neurological events and consequent imprecision of the effect estimate. Failure to achieve p<0.05 in a relatively small study does not establish equivalence between the procedures. The direction of effect, absolute risk difference, confidence interval, and consistency with external evidence are therefore more informative than the p value considered in isolation. Another methodological issue concerns adjustment for confounding. Because the present study was observational, the choice between coronectomy and extraction may have been influenced by clinical and radiographic characteristics. A multivariable logistic regression model was initially considered; however, only seven IAN events occurred. Including several covariates in such a model would yield unstable coefficients, excessively wide confidence intervals, and substantial risk of overfitting. Exploratory univariable analyses were therefore considered more appropriate. Larger multicentre cohorts would permit more reliable adjustment for anatomical and surgical factors. The relationship between radiographic risk signs and neurological outcome also deserves cautious interpretation. In the present analysis, interruption of the mandibular canal border and darkening of the roots were numerically more common among patients who developed IAN disturbance. The small number of events prevented firm statistical conclusions. Nevertheless, the direction of these associations is consistent with the established literature showing that specific panoramic features identify third molars with an increased likelihood of intimate root-canal contact [3,4]. The operative technique itself remains an important determinant of success. Coronectomy requires removal of the crown without mobilization of the roots. Renton et al. demonstrated the clinical importance of this distinction by separating successful from failed coronectomies [9]. Once the roots become mobile, their retention may no longer be appropriate, and conversion to complete removal may become necessary. Consequently, the neurological advantage associated with coronectomy cannot automatically be extrapolated to procedures in which substantial root manipulation has already occurred. Patient counselling is equally important. Patients considered for coronectomy should understand that the objective is intentional preservation of the roots to minimize neurological risk. They should also be informed that retained roots commonly migrate, that radiographic surveillance may be required, and that a minority may subsequently require removal because of exposure, symptoms, infection, or other pathology. This differs fundamentally from describing retained roots as an unintended incomplete extraction. Long-term evidence is reassuring in this regard. Root migration generally decreases considerably after the early postoperative period, and the frequency of secondary intervention remains relatively low [16,17]. Furthermore, migration away from the mandibular canal may reduce the neurological risk associated with later root removal. Consequently, the possibility of secondary intervention should be balanced against the potentially much more consequential morbidity associated with persistent IAN injury[18-20]. Taken together, the available evidence and the present comparative findings support a selective approach to high-risk mandibular third molars. Complete extraction remains appropriate when removal of the entire tooth is required and neurological risk is acceptable. Coronectomy becomes particularly relevant when imaging indicates an intimate root-canal relationship and the roots themselves do not demonstrate pathology requiring removal. The clinical decision should therefore integrate the indication for surgery, tooth vitality and pathology, anatomical relationship with the mandibular canal, patient characteristics, surgeon experience, and feasibility of follow-up. Clinical Implications Coronectomy should be considered a nerve-sparing surgical option rather than an incomplete form of extraction. In mandibular third molars with radiographic features indicating a high risk of IAN injury, preservation of stable and disease-free roots may reduce direct manipulation of the neurovascular bundle [21,22]. The decision should remain individualized. Teeth with root-associated pathology, non-vital roots, extensive root caries, or other conditions requiring complete removal are unsuitable for intentional root retention. Intraoperative root mobility also alters management because a mobile retained root may compromise healing and may require removal. Postoperative counselling should emphasize that migration of retained roots is common and does not itself constitute treatment failure. Follow-up should focus on clinically meaningful outcomes, particularly pain, infection, root exposure, pathological change, and requirement for secondary intervention. Strengths and Limitations A major strength of the study was the direct comparison of two clinically relevant management strategies among mandibular third molars selected because of increased neurological risk. Assessment extended beyond IAN disturbance to conventional postoperative morbidity and coronectomy-specific outcomes, including root migration, exposure, infection, and secondary removal. Separating successful coronectomy from procedures complicated by intraoperative root mobilization also provides a more clinically meaningful assessment of the technique. Several limitations require consideration. First, the observational design prevents the same degree of control over treatment allocation as a randomized trial and permits residual confounding by anatomical or clinical factors influencing procedure selection. Second, IAN injury was uncommon, resulting in limited statistical power and wide confidence intervals. The small number of neurological events also precluded a reliable multivariable regression model. Third, root migration can be assessed only in patients with adequate postoperative radiographic follow-up, introducing potential follow-up bias. Differences in postoperative observation duration may additionally influence detection of root exposure and secondary intervention. Fourth, sensory assessment based predominantly on clinical examination may be less sensitive than a standardized battery of quantitative neurosensory tests. Finally, findings from a modest cohort of high-risk third molars may not be generalizable to routine mandibular third-molar extraction in which the roots are clearly separated from the mandibular canal. Future prospective multicentre studies should employ standardized definitions of neurological injury, validated neurosensory testing, predefined imaging criteria, and sufficiently long follow-up to capture delayed retained-root complications. Larger datasets would also permit robust multivariable adjustment and subgroup analysis according to anatomical risk.

Coronectomy represents a clinically relevant alternative to complete extraction for mandibular third molars with a high-risk relationship to the inferior alveolar canal. In the present comparative analysis, postoperative IAN disturbance was less frequent after coronectomy, while early postoperative pain, infection, alveolar osteitis, and wound-healing outcomes were broadly comparable between procedures. Migration of retained roots was common but usually represented an expected postoperative phenomenon rather than treatment failure, and only a small proportion required secondary removal. These findings are consistent with controlled trials, long-term observational studies, and systematic reviews supporting coronectomy as a nerve-sparing strategy in appropriately selected cases. The procedure should nevertheless be undertaken with careful case selection, technically appropriate root retention, patient counselling, and follow-up. Larger prospective studies are required to define more precisely which anatomical and clinical subgroups derive the greatest benefit.

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