From CBCT to Synthesized Extraoral Bitewing: A Patient-Specific Pipeline for Dose- and Cost-Free 2D Information Presentation and Clinical Decision Support.

Abstract

Objectives: To evaluate whether synthesized extraoral bitewing views generated from existing CBCT scans can support posterior-tooth assessment when CBCT is the initial imaging modality, without additional radiographic acquisition.

Methods: We retrospectively assembled 60 CBCT scans from three datasets encompassing diverse posterior jaw morphologies. We developed a computational pipeline to compute a patient specific dental arch, define a focal trough, and simulate extraoral bitewing acquisition using a panoramic inspired rotating source trajectory. Synthetic projections were generated using a Beer-Lambert forward model implemented in TIGRE and reconstructed into right and left synthesized extraoral bitewing views. Eight observers, including dental students and residents in endodontics, periodontics, and oral radiology scored posterior teeth for caries, periapical lesions, and periodontal bone loss using original CBCT images and synthesized extraoral bitewing views in separate sessions. A consensus of two oral radiology experts served as the reference. Performance was evaluated with false positive and false negative rates, specificity, F1 score, and AUC. Inter observer agreement was assessed with (weighted) kappa. Differences in AUC (ΔAUC) between CBCT and synthesized extraoral bitewing views were evaluated using bootstrap-derived 95% confidence intervals.

Results: Compared with CBCT alone, synthesized extraoral bitewing views were associated with lower overdiagnosis for dental caries and periapical lesions (95% CI, 5.87-12.00 and 3.87-8.12,respectively) and reduced underdiagnosis for periodontal bone loss (95% CI, 10.12-18.37). Synthesized extraoral bitewing views showed higher ordinal AUC for dental caries and periodontal bone loss (mean ΔAUC,-0.12 to - 0.05 and -0.11 to - 0.04,respectively). No consistent improvement was observed for periapical lesion AUC, possibly due to small sample size and limited power.

Conclusion: When CBCT is the initial imaging modality, synthesized extraoral bitewing views derived from the existing scan may provide a complementary two-dimensional visualization for posterior-tooth assessment. In this reader study, the derived views were associated with shorter interpretation time and task-dependent changes in diagnostic performance.