Dental Cone-Beam CT
Cone-beam volumetric X-ray imaging optimized for dental + maxillofacial anatomy. Distinct from medical CT: lower dose, higher spatial resolution for fine bone detail, smaller footprint, lower capital cost. Typically combined with 2D panoramic + cephalometric imaging in a single dental imaging unit.
Physics
Single rotation around the patient's head. A cone-shaped X-ray beam + flat-panel detector acquires ~200-400 projection images in a ~20-40 sec sweep. Reconstruction produces a 3D volume — typically anisotropic (higher resolution in the transverse plane than axial) compared to medical CT's isotropic voxels.
Clinical applications
- Dental implant planning — bone quality + quantity, nerve proximity (inferior alveolar), sinus floor position
- Endodontics — root canal anatomy, additional canals, periapical pathology
- Orthognathic surgery planning — skeletal relationships + airway analysis
- Orthodontics — impacted teeth localization, root resorption, TMJ assessment
- Oral surgery — cysts, tumors, fractures
- TMJ evaluation — bony architecture
- Airway analysis — sleep apnea workup (increasingly common)
Key specs
- Field of view options:
- Small FOV (~5 × 5 cm) — single-tooth endo / single implant
- Medium FOV (~10 × 10 cm) — single-jaw, implant planning in larger regions
- Large FOV (~20 × 17 cm) — full maxillofacial, airway, orthognathic
- Voxel size — 75-400 μm typical (often configurable per protocol)
- Dose — 50-1000 μSv typical (far lower than medical CT's ~10 mSv head CT)
- Reconstruction time — 20 sec to 2 min
- Pan + ceph integration — typical on dental-office units
Image characteristics
Dental CBCT has known artifacts:
- Beam hardening + metal scatter — metal restorations (crowns, implants, amalgam) produce star-burst artifacts that limit clinical read in the immediate periphery
- Motion artifacts — patient motion during 20-40 sec sweep creates blurring
- Limited Hounsfield-unit fidelity — unlike medical CT, dental CBCT's grayscale values are not reliably calibrated to HU. Density measurements for bone-quality assessment are qualitative, not quantitative.
Systems
- Planmeca ProMax 3D family
- Dentsply Sirona Orthophos (SL + other variants)
- Carestream CS 9600
- J. Morita Veraviewepocs
- Vatech Pax-i3D
Service reality
- Detector aging — flat-panel detectors lose DQE over ~10 years
- Positioning laser drift — patient alignment errors = asymmetric reconstructions
- PC hardware obsolescence — workstation OS compatibility ages faster than the imaging hardware
- Calibration phantoms — monthly water-density phantom catches drift
Regulatory
- FDA Class II (510(k))
- State radiation registration
- Lower dose than medical CT → less state scrutiny but still regulated
- Dental-specific radiation safety training for techs + doctors