Cone-beam computed tomography (CBCT) provides three-dimensional imaging at low radiation doses relative to medical CT, and has become a selective adjunct to periapical radiography in modern endodontics.
CBCT is recommended when conventional imaging is insufficient to answer a diagnostic or planning question. Major indications include:
- Complex anatomy — maxillary molars (MB2), mandibular second molars (C-shaped), dens invaginatus.
- Persistent disease after treatment — differential diagnosis of missed canals, vertical root fracture, extra-radicular infection.
- Diagnosis of resorption — internal vs. external, cervical resorption staging.
- Trauma — root fractures, lateral luxations, apical dilacerations.
- Pre-surgical planning — proximity to mental nerve, maxillary sinus, adjacent root anatomy.
- Streak and beam-hardening artifacts from existing fillings, posts, gutta-percha.
- Limited soft-tissue detail.
- Voxel size vs. dose tradeoff — small FOV, high-resolution scans preferred for endodontics.
- Radiation exposure — still higher than PA radiographs; justify each scan.
- Small field of view (FOV) — 5×5 cm or smaller; focuses dose and reduces artifact.
- High resolution — voxel ≤100 μm for endodontics.
- Single-tooth imaging when anatomy allows; switch to larger FOV for trauma or multi-tooth evaluation.
- Positioning — stable head; bite block; parallel occlusal plane.
- MB2 detection — look at axial slices 2–3 mm apical to the chamber floor; the MB2 orifice sits palatal to MB1, sometimes under a dentinal shelf.
- Vertical root fractures — sagittal/coronal slices, look for J-shaped or halo radiolucencies. Absence of a fracture line does not rule it out.
- Resorption — axial slices at the lesion level are most discriminating.