Is CBCT safer than a medical CT?

It delivers much less radiation for comparable dental tasks, but it is still ionising radiation. The ALARA principle applies — prescribe only when the answer to a clinical question cannot be obtained from a lower-dose exam.

Can CBCT replace medical CT?

For bony dental and maxillofacial indications, usually yes. For soft-tissue disease, oncologic staging and emergency trauma, no — the contrast resolution is insufficient.

Are CBCT Hounsfield units reliable?

No. Voxel values are manufacturer-dependent and are best used for visual assessment rather than quantitative bone density. If you need calibrated density, ask for a medical CT.

CBCT vs CT scan — Differences, dose, uses in dentistry

How each technology works

Medical multi-slice CT (MSCT) uses a narrow fan-shaped beam and a ring of detectors. The patient moves through the gantry and the scanner acquires contiguous axial slices, which are reconstructed into 3D data. Helical acquisition and multiple detector rows allow sub-millimeter slice thickness over the entire body.

Cone-beam CT uses a cone-shaped X-ray beam and a single 2D flat-panel detector. The tube and detector rotate once (180° to 360°) around the patient, capturing hundreds of basis projections. A Feldkamp-type algorithm reconstructs an isotropic volume, usually of the head and neck only.

Radiation dose — the headline difference

Effective dose for a full-skull CBCT scan typically ranges from 30 to 200 μSv depending on field of view and exposure settings. A medical head CT usually delivers 1,500 to 2,000 μSv — roughly 10× more. This is why CBCT is acceptable for routine dental indications where medical CT would be hard to justify.

Dose rises with larger field of view, higher mA·s and smaller voxel size. Most practices use a mid-range FOV (around 8–10 cm) for implant planning and keep high-resolution protocols for specific tasks like endodontic re-treatments.

Resolution and image quality

CBCT wins on isotropic spatial resolution — voxels are typically 0.1 to 0.4 mm on a side, which is better than most medical CT protocols for hard tissue. This matters for root canal anatomy, implant planning and periodontal defects.

Medical CT wins on soft-tissue contrast and dynamic range. Hounsfield values are calibrated and reliable, which is essential for oncology or vascular assessment. CBCT voxel values are not true Hounsfield units and vary between manufacturers and even between scans on the same machine.

When to pick which

Pick CBCT for: implant planning, complex endodontics, impacted teeth assessment, orthodontic planning of the jaws, TMJ bony assessment, airway volumetrics, evaluation of pathology confined to bone, and sinus assessment for lateral window sinus lift.

Pick medical CT (or MRI) for: staging of head and neck malignancy, suspected cervical spine injury, evaluation of soft-tissue masses, salivary gland disease that is not calcified, or any indication where Hounsfield calibration matters clinically.

CBCT vs medical CT — what is actually different