Automated detection of C-shaped canals in mandibular second molars from panoramic radiographs: comparing single and ensemble convolutional neural networks within a 2-stage pipeline


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Çakmak Y. E., Er K.

CLINICAL ORAL INVESTIGATIONS, cilt.30, sa.5, ss.1-18, 2026 (SCI-Expanded, Scopus)

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 30 Sayı: 5
  • Basım Tarihi: 2026
  • Doi Numarası: 10.1007/s00784-026-06868-x
  • Dergi Adı: CLINICAL ORAL INVESTIGATIONS
  • Derginin Tarandığı İndeksler: Scopus, Science Citation Index Expanded (SCI-EXPANDED), MEDLINE
  • Sayfa Sayıları: ss.1-18
  • Akdeniz Üniversitesi Adresli: Evet

Özet

Objectives

This study aimed to develop and validate a two-stage deep-learning workflow that automatically localizes mandibular second molars on panoramic radiographs and classifies C-shaped canal presence as an explainable, clinically deployable decision-support tool.

Materials and methods

A total of 1,252 panoramic radiographs (2015–2025) were retrieved from a digital archive. Stage 1 employed YOLOv8 to detect teeth #37 and #47. Stage 2 applied three CNNs (DenseNet-169, EfficientNet-B6, ConvNeXt-Base) and ensemble approaches to classify C-shaped canals on YOLO-derived crops. Data were split 70/15/15 for training/validation/testing. Detection was evaluated using IoU and mAP; classification via accuracy, sensitivity, specificity, F1-score, and AUC. Pairwise AUC comparisons used DeLong test with Bonferroni correction. Grad-CAM provided visual explanations.

Results

YOLOv8 achieved high localization performance, reliably supplying regions of interest to classifiers. ConvNeXt-Base demonstrated the most consistent discrimination with top-tier accuracy and F1-score. A binary EfficientNet-ConvNeXt ensemble performed comparably to the best individual model, while the tertiary ensemble showed no improvement. DeLong analysis revealed statistically significant AUC advantage of ConvNeXt-Base over DenseNet-169 for tooth #47 after correction.

Conclusions

This two-stage pipeline enables accurate, automation-ready detection of C-shaped canals from routine panoramic radiographs, potentially informing patient triage and CBCT indication decisions. Multicenter validation is warranted before clinical deployment.

Clinical relevance

This AI system offers a practical screening tool using existing panoramic radiographs to identify high-risk patients, potentially improving treatment planning efficiency, reducing unnecessary CBCT referrals, and alerting clinicians to complex anatomy before endodontic therapy.