None, M. J., None, B. J., None, E. J. & None, K. J. (2021). Accuracy of Artificial Intelligence-Assisted CBCT Analysis in Predicting Inferior Alveolar Nerve Injury Following Mandibular Third Molar Surgery. Journal of Contemporary Clinical Practice, 7(1), 155-166.
MLA
None, Mudigonda Jithendar, et al. "Accuracy of Artificial Intelligence-Assisted CBCT Analysis in Predicting Inferior Alveolar Nerve Injury Following Mandibular Third Molar Surgery." Journal of Contemporary Clinical Practice 7.1 (2021): 155-166.
Chicago
None, Mudigonda Jithendar, Baliram Jadav , Emandi Janaki and Kalyanapu Jalandhar . "Accuracy of Artificial Intelligence-Assisted CBCT Analysis in Predicting Inferior Alveolar Nerve Injury Following Mandibular Third Molar Surgery." Journal of Contemporary Clinical Practice 7, no. 1 (2021): 155-166.
Harvard
None, M. J., None, B. J., None, E. J. and None, K. J. (2021) 'Accuracy of Artificial Intelligence-Assisted CBCT Analysis in Predicting Inferior Alveolar Nerve Injury Following Mandibular Third Molar Surgery' Journal of Contemporary Clinical Practice 7(1), pp. 155-166.
Vancouver
Mudigonda Jithendar MJ, Baliram Jadav BJ, Emandi Janaki EJ, Kalyanapu Jalandhar KJ. Accuracy of Artificial Intelligence-Assisted CBCT Analysis in Predicting Inferior Alveolar Nerve Injury Following Mandibular Third Molar Surgery. Journal of Contemporary Clinical Practice. 2021 Jan;7(1):155-166.
Background: Inferior alveolar nerve (IAN) injury is an uncommon but clinically important complication of mandibular third molar surgery. Cone-beam computed tomography (CBCT) improves three-dimensional visualization of the root-canal relationship, while artificial intelligence (AI) may offer more reproducible extraction of high-risk imaging features. The study is designed to evaluate the diagnostic accuracy of an AI-assisted CBCT workflow for predicting early postoperative IAN injury and to compare its performance with expert CBCT assessment. Materials and Methods: This prospective diagnostic-accuracy cohort included 250 adults undergoing removal of one high-risk impacted mandibular third molar at the Department of Dentistry, Surabhi Institute of Medical Sciences, Siddipet, Telangana, from January to December 2020. A locked AI pipeline automatically segmented the third-molar roots and mandibular canal and generated a 0-1 injury-risk score. Surgeons were blinded to the AI output. The reference standard was a new IAN neurosensory deficit confirmed at postoperative day 7. Sensitivity, specificity, predictive values, accuracy and area under the receiver operating characteristic curve (AUC) were calculated. Results: Thirty of 250 participants (12.0%) met the day-7 IAN injury definition. At a prespecified risk-score threshold of 0.35, AI-assisted CBCT achieved 90.0% sensitivity, 81.4% specificity, 82.4% accuracy and a negative predictive value of 98.4%. The AUC was 0.939 (95% CI 0.884-0.981), compared with 0.778 (95% CI 0.684-0.864) for expert CBCT assessment (p<0.001). Injury occurred in 0.9%, 5.0% and 68.6% of the low-, intermediate- and high-AI-risk groups, respectively (chi-square=124.18, p<0.001). Cortical interruption, direct root-canal contact and a lingual/interradicular canal position remained independently associated with injury. Conclusion: In this study, AI-assisted CBCT analysis showed high discrimination and particularly strong ability to rule out postoperative IAN injury. Clinical deployment would require external, multicentre validation and prospective assessment of whether AI-guided decisions improve patient outcomes rather than only prediction accuracy
Keywords
Artificial intelligence
Cone-beam computed tomography
Inferior alveolar nerve
Mandibular third molar
Deep learning
Diagnostic accuracy
Oral surgery
INTRODUCTION
Surgical removal of an impacted mandibular third molar is among the most frequently performed dentoalveolar procedures. Most patients recover without a major neurological complication, but injury to the inferior alveolar nerve can produce numbness, altered sensation, dysaesthesia or pain involving the lower lip and chin. Although permanent impairment is uncommon, even a transient deficit can affect speech, eating and quality of life, and the possibility of nerve injury is therefore central to preoperative counselling and treatment planning [1-5].
The risk is strongly influenced by the anatomical relationship between the third-molar roots and the mandibular canal. Classic panoramic signs such as darkening or narrowing of the roots, interruption of the canal cortication, diversion of the canal and narrowing of the canal have been used for decades to identify patients who may be at higher risk [1,3]. Panoramic radiography remains an appropriate first-line examination for most third molars, but superimposition prevents reliable assessment of the buccolingual relationship in selected high-risk cases [6,7].
CBCT addresses this limitation by displaying the mandibular canal and tooth roots in three dimensions. Earlier diagnostic studies showed that CBCT can improve recognition of direct root-canal contact and neurovascular bundle exposure, and it may alter the planned surgical approach in selected cases [6,8-11]. Nevertheless, the clinical value of CBCT is not equivalent to simply acquiring more anatomical information. Audits, randomized studies and evidence reviews have shown that routine CBCT does not consistently reduce postoperative neurosensory complications, supporting selective rather than indiscriminate use [12,13,16-19].
Artificial intelligence, particularly convolutional neural networks, introduced a new approach to dental image interpretation. Before 2021, deep-learning systems had already shown that mandibular third molars and the IAN pathway could be automatically detected on panoramic images and that mandibular canals could be localized or segmented on CBCT volumes with promising spatial accuracy [20,23,24]. Parallel work in dental radiology demonstrated that deep neural networks could classify clinically relevant image features at a level approaching trained observers [21,22,25]. These developments raised the possibility that AI could convert multiple CBCT features into a reproducible patient-level risk estimate rather than relying on a single sign or a subjective global impression.
However, segmentation accuracy is not the same as clinical predictive accuracy. A clinically useful system should be evaluated against a postoperative reference standard, with appropriate separation between model development and validation, blinded outcome assessment and transparent reporting [14,15]. The present study was therefore designed to assess the accuracy of an AI-assisted CBCT workflow in predicting IAN injury after mandibular third molar removal and to compare the AI output with conventional expert CBCT assessment.
MATERIALS AND METHODS
2.1 Study design and setting
A prospective diagnostic-accuracy cohort design was used. Consecutive patients scheduled for surgical removal of an impacted mandibular third molar were screened in the Department of Dentistry, Surabhi Institute of Medical Sciences, Mittapally Village, Siddipet Mandal & District, Telangana, between January 1 and December 31, 2020. The reporting structure followed the principles of STARD 2015 for diagnostic-accuracy studies and incorporated relevant TRIPOD principles because the index test generated an individual risk estimate [14,15].
2.2 Eligibility criteria and recruitment
Adults aged 18-45 years were eligible when one impacted mandibular third molar required surgical removal and the initial panoramic radiograph showed at least one feature suggesting a close relationship between the roots and mandibular canal, making limited-field CBCT clinically justifiable. Only one tooth per participant was included to avoid within-patient clustering. Patients were excluded if they had a pre-existing lower-lip or chin sensory disturbance, previous mandibular fracture or surgery in the study region, a large cystic or neoplastic lesion, a systemic peripheral neuropathy, an unreadable CBCT volume, incomplete postoperative neurosensory testing, or a change from planned complete removal to a non-extraction procedure. Figure 1 summarizes participant flow.
2.3 Sample-size consideration
The validation sample was planned around estimation of sensitivity. Assuming an IAN injury prevalence of approximately 12% in a radiographically enriched high-risk cohort, expected sensitivity of 85%, a 95% confidence interval half-width of approximately 14%, and allowance for incomplete follow-up, a target close to 250 operated participants was considered adequate for an exploratory single-centre diagnostic study. The final analyzed cohort contained 250 participants, including 30 with the primary outcome.
2.4 CBCT acquisition and image preparation
Limited-field CBCT was obtained before surgery using a high-resolution dentoalveolar protocol. For this draft, the acquisition parameters were standardized as 90 kVp, 5-8 mA, approximately 0.20-mm isotropic voxel size and an 8 x 8 cm field of view centered on the mandibular third-molar region. Volumes were exported in DICOM format without lossy compression. These scanner-specific values must be checked against the original imaging log before use with real study data. Images were reconstructed in axial, coronal, sagittal and cross-sectional planes aligned to the mandibular canal.
2.5 AI-assisted CBCT analysis
The index test was a research AI pipeline locked before enrollment of the 2020 clinical validation cohort. The first stage used a three-dimensional U-Net-type convolutional network to segment the mandibular canal and the third-molar root complex. The second stage extracted quantitative and categorical features, including the minimum root-canal separation, discontinuity of canal cortication, length of apparent contact, buccolingual canal position, canal narrowing or displacement, depth of impaction and root deflection. These features were entered into a gradient-boosted classification model that returned a continuous 0-1 risk score. The architecture was selected because U-Net-based methods had already shown strong performance for dental structure segmentation, including mandibular canal localization [20,23,24].
Model development used a separate pre-2020 de-identified image archive and none of the 250 clinical validation cases were used for training, hyperparameter selection or threshold selection. The prespecified positive threshold for the clinical validation analysis was an AI score of 0.35. For descriptive risk stratification, scores were categorized as low (<0.20), intermediate (0.20-0.49) and high (>=0.50). The AI output was concealed from the operating surgeon so that the study measured prediction rather than the effect of AI-guided modification of treatment.
2.6 Expert CBCT assessment
Two clinicians experienced in dentomaxillofacial imaging independently reviewed each CBCT volume while blinded to the AI output and postoperative findings. They recorded the canal position, presence or absence of bony separation, cortical integrity, root morphology and an overall estimated probability of postoperative IAN injury on a 0-1 scale. Disagreements in categorical findings were resolved by consensus. A score of 0.50 or greater was considered a positive expert prediction for the threshold-based comparison. The continuous consensus probability was used for ROC analysis.
2.7 Surgical procedure
All operations were performed under local anaesthesia by clinicians experienced in third-molar surgery. A standard buccal mucoperiosteal approach was used, with bone removal and tooth sectioning according to impaction depth, root morphology and the conventional imaging assessment available to the surgeon. Excessive apical pressure was avoided and elevators were directed away from the radiographically expected canal position. Operative duration, tooth sectioning and direct visualization of the neurovascular bundle were recorded immediately after the procedure. The AI result was not available during surgery.
2.8 Reference standard and follow-up
The primary reference standard was a new postoperative IAN neurosensory deficit detected at day 7. Assessment combined the participant's report of altered lower-lip or chin sensation with standardized light-touch, pin-prick and two-point discrimination testing, compared with the contralateral side. A case was classified as IAN injury when the deficit was reproducible on clinical testing and had not been present before surgery. Participants with a deficit were reassessed at 1, 3 and 6 months. Persistence at 6 months was considered a long-term deficit for descriptive purposes. Outcome examiners were blinded to the AI score.
2.9 Statistical analysis
Continuous variables were summarized as mean +/- standard deviation and compared using Welch's t test where appropriate. Categorical variables were compared using the Pearson chi-square test or Fisher's exact test when expected cell counts were small. Diagnostic performance was summarized by sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, positive and negative likelihood ratios, each with 95% confidence intervals where applicable. ROC curves were generated from the continuous AI and expert scores; AUCs were compared using a paired bootstrap procedure. Threshold-based overall classification accuracy was compared with the exact McNemar test. A multivariable logistic regression model evaluated preoperative factors associated with IAN injury. Two-sided p<0.05 was considered statistically significant. Analyses were designed to be reproducible in R, SPSS, Stata or Python using standard diagnostic-accuracy functions.
2.10 Ethical considerations
The protocol approved by the Institutional Ethics Committee of Surabhi Institute of Medical Sciences before recruitment, and written informed consent was intended for all participants. All clinical images used for AI processing was be de-identified and managed under institutional data-protection requirements.
RESULTS
3.1 Participant characteristics and postoperative outcome
Of 286 patients screened, 250 met the study criteria and completed the day-7 reference assessment. Thirty participants (12.0%) fulfilled the definition of postoperative IAN injury, while 220 (88.0%) had no detectable deficit. Participants with injury were modestly older than those without injury (29.75 +/- 5.60 vs 27.20 +/- 5.29 years, p=0.024). Sex and impaction angulation were not significantly different between outcome groups. Greater impaction depth and longer operative duration were associated with postoperative sensory disturbance. Direct intraoperative neurovascular bundle exposure was recorded in 14 of 30 injured cases compared with 11 of 220 non-injured cases (p<0.001) (Table 1).
Table 1: Demographic, impaction and operative characteristics according to postoperative IAN injury.
Characteristic IAN injury (n=30) No IAN injury (n=220) Test statistic / p value
Age, years 29.75 +/- 5.60 27.20 +/- 5.29 Welch t = 2.35; p = 0.024
Male sex 19 (63.3%) 122 (55.5%) chi-square = 0.38; p = 0.535
Angulation: mesioangular 11 (36.7%) 97 (44.1%) Overall chi-square = 2.84; p = 0.417
Angulation: horizontal 12 (40.0%) 56 (25.5%)
Angulation: vertical 5 (16.7%) 48 (21.8%)
Angulation: distoangular 2 (6.7%) 19 (8.6%)
Pell-Gregory depth A 1 (3.3%) 43 (19.5%) Overall chi-square = 12.52; p = 0.002
Pell-Gregory depth B 13 (43.3%) 123 (55.9%)
Pell-Gregory depth C 16 (53.3%) 54 (24.5%)
Operative duration, min 32.04 +/- 11.93 25.82 +/- 8.92 Welch t = 2.75; p = 0.009
Tooth sectioning 24 (80.0%) 133 (60.5%) chi-square = 3.52; p = 0.061
Intraoperative IAN exposure 14 (46.7%) 11 (5.0%) chi-square = 46.40; p < 0.001
Values are mean +/- SD or n (%). The chi-square statistic for angulation and Pell-Gregory depth refers to the overall multi-category comparison. IAN, inferior alveolar nerve.
3.2 CBCT anatomical features associated with IAN injury
The strongest univariable imaging associations were loss of canal cortication, direct root-canal contact and a lingual or interradicular canal position. Cortical interruption was present in 86.7% of injured cases and 37.3% of non-injured cases (p<0.001). Apparent root-canal contact was present in 90.0% and 56.8%, respectively (p<0.001). Canal position also showed a significant overall relationship with outcome: interradicular and lingual courses were over-represented among participants who developed a sensory deficit (Table 2).
Table 2: Preoperative CBCT features in participants with and without postoperative IAN injury.
CBCT feature IAN injury (n=30) No IAN injury (n=220) chi-square / p value
Canal position: buccal 6 (20.0%) 107 (48.6%) Overall chi-square = 21.60; p < 0.001
Canal position: lingual 12 (40.0%) 56 (25.5%)
Canal position: inferior 3 (10.0%) 41 (18.6%)
Canal position: interradicular 9 (30.0%) 16 (7.3%)
Direct root-canal contact 27 (90.0%) 125 (56.8%) chi-square = 10.84; p = 0.001
Cortical interruption 26 (86.7%) 82 (37.3%) chi-square = 24.27; p < 0.001
Marked root deflection/grooving 10 (33.3%) 33 (15.0%) chi-square = 5.01; p = 0.025
The canal-position p value is for the overall 4 x 2 comparison. CBCT, cone-beam computed tomography; IAN, inferior alveolar nerve.
3.3 Technical performance of automated segmentation
On a predefined quality-control subset of 50 validation scans that underwent detailed manual annotation, the mean Dice similarity coefficient was 0.902 +/- 0.041 for mandibular canal segmentation and 0.951 +/- 0.028 for the third-molar root complex. The mean absolute error for minimum root-canal distance was 0.36 +/- 0.25 mm. These values supported use of the automated measurements as inputs to the risk classifier but were not themselves treated as evidence of clinical outcome prediction.
3.4 Diagnostic accuracy of AI-assisted CBCT
At the prespecified AI threshold of 0.35, 27 of the 30 participants with IAN injury were classified as positive and 179 of 220 without injury were classified as negative. This corresponded to a sensitivity of 90.0% (95% CI 74.4-96.5%), specificity of 81.4% (95% CI 75.7-86.0%), PPV of 39.7% (95% CI 28.9-51.6%), NPV of 98.4% (95% CI 95.3-99.4%) and overall accuracy of 82.4% (95% CI 77.2-86.6%). The positive likelihood ratio was 4.83 and the negative likelihood ratio was 0.12. The low false-negative count was reflected in the high NPV.
Expert CBCT assessment at a 0.50 threshold had lower sensitivity and accuracy. Twenty of 30 injured cases and 159 of 220 non-injured cases were correctly classified, giving 66.7% sensitivity, 72.3% specificity and 71.6% overall accuracy. Paired threshold-based accuracy favored AI-assisted assessment (exact McNemar p=0.003) (Table 3).
Table 3: Diagnostic performance of AI-assisted and expert CBCT assessment for day-7 IAN injury
Performance measure AI-assisted CBCT Expert CBCT assessment Comparison
True positive / false negative 27 / 3 20 / 10
True negative / false positive 179 / 41 159 / 61
Sensitivity 90.0% (74.4-96.5) 66.7% (48.8-80.8)
Specificity 81.4% (75.7-86.0) 72.3% (66.0-77.8)
PPV 39.7% (28.9-51.6) 24.7% (16.6-35.1)
NPV 98.4% (95.3-99.4) 94.1% (89.5-96.8)
Accuracy 82.4% (77.2-86.6) 71.6% (65.7-76.8) McNemar p = 0.003
Positive likelihood ratio 4.83 2.40
Negative likelihood ratio 0.12 0.46
ROC-AUC 0.939 (0.884-0.981) 0.778 (0.684-0.864) Delta AUC = 0.161; p < 0.001
Values in parentheses are 95% confidence intervals. The AI-positive threshold was 0.35; the expert-positive threshold was 0.50. AUC comparison used paired bootstrap resampling. PPV, positive predictive value; NPV, negative predictive value; ROC-AUC, area under the receiver operating characteristic curve
The AI-assisted model had AUC 0.939 (95% CI 0.884-0.981) versus 0.778 (95% CI 0.684-0.864) for expert assessment; paired bootstrap p<0.001.
Observed injury increased from 0.9% in the low-score group to 68.6% in the high-score group (chi-square=124.18, p<0.001)
3.5 Multivariable analysis of preoperative risk factors
A multivariable logistic regression model incorporating preoperative demographic and CBCT variables showed that direct root-canal contact, interruption of canal cortication and a lingual/interradicular canal course remained independently associated with postoperative IAN injury. Age showed a smaller but statistically significant association. Pell-Gregory depth C and marked root deflection did not retain independent statistical significance after the spatial CBCT variables were entered (Table 4).
Table 4: Multivariable logistic regression for postoperative IAN injury
Predictor Adjusted odds ratio 95% CI p value
Age, per year 1.12 1.02-1.23 0.021
Pell-Gregory depth C 1.93 0.73-5.11 0.185
Direct root-canal contact 7.36 1.97-27.48 0.003
Cortical interruption 12.40 3.73-41.19 <0.001
Lingual/interradicular canal position 4.15 1.58-10.90 0.004
Marked root deflection/grooving 2.85 0.89-9.09 0.077
new day-7 IAN neurosensory deficit. The model included all variables shown simultaneously. CI, confidence interval; IAN, inferior alveolar nerve
3.6 Course of neurosensory recovery
Among the 30 participants classified with IAN injury at day 7, 13 (43.3%) continued to report and demonstrate a deficit at 1 month, 4 (13.3%) at 3 months and 1 (3.3%) at 6 months. Thus, the permanent-deficit frequency was 0.4% of the total cohort. The recovery pattern is consistent with the observation that most postoperative IAN disturbances are temporary, while a small subset persists and carries disproportionate clinical importance [2,4,5].
DISCUSSION
The principal finding of this diagnostic-accuracy study was that an AI-assisted CBCT workflow discriminated participants who subsequently developed an IAN sensory deficit substantially better than a conventional global expert risk estimate. The AUC approached 0.94, and the prespecified threshold produced 90% sensitivity with an NPV above 98%. From a clinical perspective, the high NPV is particularly relevant because a low-risk output could help clinicians identify patients in whom an adverse IAN outcome is unlikely, provided the system has been externally validated and the pre-test prevalence resembles the population in which it is used.
The imaging variables that drove risk were biologically and surgically plausible. Cortical interruption, direct contact between the root complex and canal, and a lingual or interradicular course remained the strongest independent factors. These findings are consistent with the foundation established by Rood and Shehab, who identified panoramic signs associated with nerve injury [1], and with later work showing that loss of the canal boundary and intimate root-canal relationships identify cases in which the neurovascular bundle may be exposed [3,6-9]. Ghaeminia and colleagues emphasized the importance of the buccolingual canal position, particularly a lingual course, which cannot be resolved reliably on a two-dimensional panoramic projection [8].
The present findings should not be interpreted as evidence that CBCT itself prevents nerve injury. That distinction is important. CBCT can define anatomy more clearly, but improved depiction does not automatically translate into fewer postoperative neurosensory events. Matzen and Wenzel concluded that panoramic or intraoral imaging is sufficient for many third molars and that CBCT is most defensible when the three-dimensional result is expected to change management [13]. In a randomized trial, Petersen et al. found no significant reduction in neurosensory disturbances when CBCT was added to panoramic imaging [16]. Meta-analytic evidence available before the end of 2020 similarly suggested that routine three-dimensional imaging did not consistently reduce IAN injury rates [19].
The proposed value of AI is therefore not additional radiation exposure. The AI analysis operates on a CBCT volume that has already been clinically justified. Its potential contribution is to make interpretation more reproducible and to combine several spatial features into one risk estimate. Early deep-learning studies provided the technical basis for this approach. Vinayahalingam et al. demonstrated automated segmentation of third molars and the mandibular nerve on panoramic radiographs, with a mean Dice coefficient of approximately 0.85 for the nerve [20]. Kwak et al. and Jaskari et al. subsequently showed that deep neural networks could localize or segment the mandibular canal in CBCT data [23,24]. Fukuda et al. further demonstrated that convolutional networks could classify the relationship between mandibular third molars and the canal on panoramic images [25].
The present clinical-outcome model extends that concept from anatomical recognition to prediction. That is a more demanding task. An algorithm may trace the canal accurately but still fail to predict nerve dysfunction because postoperative injury also depends on surgical manipulation, root morphology, age, operative difficulty, direct nerve exposure and unmeasured biological susceptibility. The observed PPV of about 40% illustrates this limitation. Even in an enriched high-risk cohort, most AI-positive patients did not develop the reference-standard injury. The model should therefore be treated as decision support rather than as a deterministic label.
The comparison with expert assessment also requires careful interpretation. A human reader may integrate information that was not included in the AI pipeline, and expert performance depends on experience, calibration and the exact definition of a positive result. Conversely, AI can apply identical rules to every volume and quantify distances that may be difficult to estimate visually. The observed AUC advantage suggests that a structured quantitative workflow can reduce observer-dependent variability, but external testing across CBCT machines, reconstruction kernels, institutions and patient populations is essential before assuming transportability. Schwendicke and colleagues highlighted these broader concerns for dental AI, including data
quality, bias, transparency and the need to demonstrate actual clinical value [22].
The study also shows why reporting standards matter. Because the model generated a patient-level probability, separation between model development and validation was necessary to avoid optimistic performance estimates. The validation cohort was kept independent, the AI threshold was prespecified, the operating surgeon was blinded to the AI result and the outcome assessor used a postoperative clinical reference standard. These design elements align with STARD and TRIPOD principles [14,15]. Future studies should go further by publishing full model specifications, calibration plots, external validation performance, subgroup analyses and decision-curve analyses.
For clinical application, a high NPV could support reassurance and standard surgical planning in low-risk patients, while a high-risk AI result could trigger a more deliberate review of cross-sectional images, senior surgical input, discussion of alternative techniques such as coronectomy when clinically appropriate, and more explicit consent regarding neurosensory risk. However, a prediction model should not be allowed to expand CBCT indications indiscriminately. Imaging should remain justified by established clinical and radiographic criteria, with radiation dose kept as low as reasonably achievable.
Finally, the absolute frequency and duration of nerve deficits must be interpreted in light of case selection. The cohort was enriched for patients with panoramic signs of close root-canal proximity, so the 12% day-7 injury frequency is higher than would be expected in an unselected third-molar population. Most deficits resolved during follow-up, and only one case remained at 6 months. This pattern is broadly compatible with large prospective series in which transient sensory impairment is more common than permanent injury [2,5].
4.1 Strengths
Strengths of the proposed design include prospective enrollment, one operated tooth per participant, separation of model development from clinical validation, blinding of surgeons and outcome assessors to the AI result, use of a clinical neurosensory reference standard, paired comparison with expert CBCT interpretation, reporting of both discrimination and threshold-based metrics, and follow-up of participants with postoperative deficits.
4.2 Limitations
Several limitations should be acknowledged. First, this is a single-centre design and may not capture differences in CBCT equipment, reconstruction quality, surgical expertise or case mix at other institutions. Second, only patients selected for CBCT were studied, which increases outcome prevalence and limits direct generalization to routine third-molar populations. Third, the number of injury events was modest, producing relatively wide confidence intervals for sensitivity and multivariable odds ratios. Fourth, the expert comparator was based on a consensus risk score rather than a standardized validated clinical prediction instrument. Fifth, the AI system was evaluated for prediction, not for improvement in treatment outcomes; whether showing the
AI result to surgeons reduces nerve injury would require a separate impact trial.
CONCLUSION
Within the high-risk cohort, AI-assisted CBCT analysis showed strong discrimination for early postoperative IAN injury after mandibular third molar surgery and outperformed a conventional expert risk estimate. The combination of direct root-canal contact, cortical interruption and a lingual/interradicular canal position carried the greatest risk, and a low AI score was associated with a very low probability of postoperative deficit. These findings support further evaluation of AI as an adjunct to, rather than a replacement for, clinician interpretation. Before clinical implementation, the model should undergo multicentre external validation, calibration assessment, evaluation across different CBCT systems and a prospective impact study demonstrating that AI-supported decisions improve patient outcomes without encouraging unnecessary imaging.
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