Cone-beam computed tomography (CBCT) is a dental X-ray that builds a 3D volume of the teeth, jaws, and face. A cone-shaped beam rotates once around the head. A flat-panel detector records a few hundred projections. Reconstruction software turns those into a stack of voxels you can scroll, reformat, or render.
It is not a medical CT. A hospital scanner uses a fan beam and many helical rotations, with the patient lying down, and is built for soft tissue. A dental CBCT uses one rotation (typically 360° or a half-scan), the patient sits or stands in an open gantry, and the image is for hard tissue: bone, teeth, air, and canals such as the inferior alveolar nerve. Dose is lower. Soft-tissue contrast is worse — that is an MRI job.
How a CBCT scan is made
- Source + cone. One X-ray tube, cone-shaped field. That is the difference from fan-beam CT.
- Flat-panel detector. Each projection is a digital radiograph. Late-1990s panels replaced image intensifiers and made compact dental units possible.
- Reconstruction. Software back-projects the projections into a volume. The unit of that volume is a voxel (a 3D pixel). Smaller voxels resolve finer canals and fracture lines; they also raise dose and file size for the same field of view.
Field of view (FOV) is the other knob. A small FOV (one tooth, a few centimetres) is the default for endodontics or a single implant. A large FOV (both jaws, or the skull) is for orthodontics, airway, or orthognathic work. Match the FOV to the question. Do not scan the whole face for a lower-molar implant.
Where it came from
Yoshinori Arai in Japan and Piero Mozzo in Italy developed dental CBCT independently in the 1990s. The first commercial unit, the NewTom 9000 (QR, Verona), shipped in Europe in 1996. US clearance followed in 2001. Early-2000s machines such as the 3D Accuitomo made the format small enough for a dental operatory. Overview: cone-beam CT on Wikipedia.
CBCT vs the other pictures in the chair
A panoramic is a 2D wrap of both jaws — good first look, no depth. A bitewing or periapical is 2D of crowns and nearby bone — caries and follow-up. Medical CT is 3D with real soft-tissue contrast and a much higher dose. CBCT sits in the gap: 3D hard-tissue detail at a dental dose.
| Method | Typical dose | Dimensionality | Detail | Cost | Used for |
|---|---|---|---|---|---|
| Bitewing / periapical | ~5–10 μSv | 2D | Crowns, caries | Low | Cavities, follow-up |
| Panoramic | ~10–20 μSv | 2D | Overview | Low | First look at both jaws |
| CBCT | ~20–500 μSv | 3D | Bone and teeth | Moderate | Implants, endo, ortho, jaw surgery |
| Medical CT | ~500–2000 μSv | 3D | Soft + hard tissue | High | Trauma and complex medical work |
Those μSv bands are typical published ranges for dental protocols, not a prescription. They move with kV, mAs, and FOV. A small-FOV endo scan sits at the low end of CBCT; a large-FOV ortho or airway scan sits at the high end. Medical head CT is higher still.
What it is used for
- Implants. Bone height and width, sinus floor, and the inferior alveolar canal before you pick a fixture.
- Endodontics. Extra canals, root fractures, and periapical lesions a periapical film can miss.
- Orthodontics / impacted teeth. 3D position of canines and their relationship to roots and the nasal floor.
- Oral surgery, TMJ, airway. Jaw relationships, condyles, and upper-airway cross-section. Useful for planning. Not a substitute for a sleep study.
Benefits and limits
| Factor | Benefit | Limit | Clinical note |
|---|---|---|---|
| Image detail | True 3D of bone and teeth | Artifacts can look like disease | Use 3D when 2D cannot answer the question |
| Radiation | Lower than medical CT | Still ionizing radiation | Smallest FOV that answers the question; extra caution in children |
| Cost | Can avoid a wrong implant or a missed canal | Higher than a panoramic or bitewing | Not a routine checkup film |
| Diagnostics | Canals, impacted teeth, jaw relationships | Poor soft-tissue contrast vs MRI | MRI if the question is disc, muscle, or other soft tissue |
| Time | Acquisition is usually 20–60 seconds | Reading the volume takes training | Budget time for reformats, not only the spin |
Artifacts that look like disease
Metal restorations and implants produce beam-hardening and metal streaks — dark bands that can be mistaken for a root fracture. Scatter from dense objects does the same. Read around restorations; do not call a streak a crack. Same family of problems as on medical CT; the dental version is worse around amalgam and fixtures. If the question is soft tissue, order MRI, not another CBCT.
What the patient actually does
Remove glasses, jewelry, and removable metal from the head and neck. Sit or stand in an open gantry (not a closed CT bore). Stay still. The rotation is typically 20–60 seconds. No contrast. No recovery. A dentist or an oral and maxillofacial radiologist reads the volume; the treating dentist gets the report and the reformats.
PYCAD builds custom web DICOM viewers when that volume has to live in a clinic app rather than a desktop workstation. Case studies.