What Is a CBCT Scan?
Cone Beam Computed Tomography (CBCT) is a specialized dental imaging technology that uses a cone-shaped X-ray beam rotating 360 degrees around the patient's head to produce three-dimensional images of teeth, jawbone, and facial structures. According to the American Academy of Oral and Maxillofacial Radiology (AAOMR, 2023), CBCT delivers an effective radiation dose of 10-200 microsieverts (µSv)—approximately 1/10 to 1/20 the dose of conventional medical CT scanners—making it the preferred imaging modality for dental implant planning, root canal diagnosis, and oral surgery assessment with minimal radiation exposure.
CBCT provides 3D imaging with 10-40 second scan time and significantly lower radiation than medical CT
How Does CBCT Work?
Key Imaging Findings
Cone-Shaped X-Ray Beam
Unlike medical CT that uses a fan-shaped beam, CBCT uses a cone-shaped X-ray beam that captures a entire volume in a single rotation. This design is specifically optimized for dental and maxillofacial imaging.
360-Degree Rotation
The X-ray source and detector rotate 360 degrees around your head in a single motion. During this rotation, hundreds of 2D images are captured from different angles.
3D Image Reconstruction
A computer reconstructs the 2D projection images into detailed 3D volumetric data. This can be viewed in multiple planes (axial, coronal, sagittal) and manipulated for detailed analysis.
Variable Field of View (FOV)
CBCT machines can adjust the scan area from a few teeth to the entire head and neck. This flexibility allows focused imaging with minimal radiation for the specific clinical need.
CBCT vs. Traditional Dental X-Rays
| Feature | CBCT | Traditional Dental X-Ray |
|---|---|---|
| Image Dimension | 3D | 2D (flat) |
| Radiation Dose | Low-medium | Very low |
| Scan Time | 10-40 seconds | Seconds |
| Image Detail | Excellent bone detail | Good for basic assessment |
| Cost | $150-750 | $25-150 |
| Common Uses | Implants, root canals, surgery | Cavities, basic bone assessment |
What Does a CBCT Machine Look Like?
Most CBCT machines look similar to panoramic dental X-ray machines you may have seen. Key features include:
- U-shaped arm containing the X-ray source and detector
- Chin rest and forehead stabilizer to keep your head still
- Handlebars for you to hold during the scan
- Open design - not enclosed like medical CT machines
- Seating or standing options depending on the machine
You won't be enclosed in a tube, making CBCT much more comfortable for claustrophobic patients compared to medical CT scanners.
What CBCT Scans Show
What Else Could It Be?
Shows complete tooth structure including roots, canals, and surrounding bone; Can see pathology not visible on 2D X-rays
3D assessment of bone height, width, and density; Shows bone quality and quantity for implants
Visualizes inferior alveolar nerve, maxillary sinuses, nasal cavity; Critical for avoiding complications
Shows bony components of temporomandibular joint; Helps diagnose arthritis and other joint issues
Common Uses of CBCT in Dentistry
What Happens Next?
Dental implant planning
CBCT is the gold standard for implant planning. It shows bone height, width, density, and location of vital structures like nerves and sinuses. This allows precise implant placement and reduces complications.
Root canal treatment
CBCT can find extra canals, detect fractures, and identify pathology that 2D X-rays miss. It's especially valuable for diagnosing failed root canals and planning retreatment.
Impacted tooth evaluation
Wisdom teeth and impacted canines are precisely localized. CBCT shows relationship to nerves, sinuses, and adjacent roots, helping prevent complications during removal.
Jaw cyst and tumor evaluation
CBCT characterizes jaw lesions, determines extent, and aids in diagnosis. The 3D visualization helps differentiate between cysts and tumors.
Orthodontic assessment
Evaluates impacted teeth, root position, airway, and jaw relationships. Helps with comprehensive treatment planning.
TMJ disorder evaluation
Visualizes the bony components of the jaw joints to diagnose arthritis, degenerative changes, and other TMJ problems.
Radiation Safety: How Safe Is CBCT?
CBCT radiation exposure is minimal compared to medical CT. According to the National Council on Radiation Protection and Measurements (NCRP Report No. 177, 2022), the effective radiation dose from dental CBCT ranges from 10-200 microsieverts (µSv) depending on the field of view—representing only 1/10 to 1/20 the radiation dose of a conventional medical CT scan of the head (1,500-2,500 µSv).
| Imaging Procedure | Effective Dose | Equivalent Background Radiation |
|---|---|---|
| Small FOV CBCT | 10-50 µSv | 1-5 days |
| Medium FOV CBCT | 50-150 µSv | 5-15 days |
| Large FOV CBCT | 100-200 µSv | 10-20 days |
| Medical CT Head | 1,500-2,500 µSv | 150-250 days |
| Background radiation (annual) | 3,000 µSv | 1 year |
Modern CBCT machines follow the ALARA (As Low As Reasonably Achievable) principle, using the lowest radiation dose necessary to obtain diagnostic images. The benefit of accurate diagnosis and treatment planning generally far outweighs the minimal radiation risk.
What to Expect During Your CBCT Scan
- Preparation: Remove jewelry, glasses, hair accessories, and removable dental appliances
- Positioning: Sit or stand in the machine; rest your chin on the chin rest
- Stabilization: The technologist may use foam pads or bite blocks to keep you still
- The Scan: Remain still for 10-40 seconds while the machine rotates around you
- Completion: You're done! No recovery time needed
The entire appointment takes 15-30 minutes, but the actual scan is usually less than a minute.
Who Should NOT Have CBCT?
CBCT may not be recommended if:
- You are pregnant (especially first trimester) - unless absolutely necessary
- You have certain medical implants that could be affected (though most are safe)
- A 2D X-ray would provide sufficient information for your case
Always discuss any concerns with your dentist.
Frequently Asked Questions
Q: Is CBCT painful? A: No, CBCT scanning is completely painless. You simply sit or stand still while the machine rotates around your head. There's no injection and no discomfort.
Q: Will I feel claustrophobic? A: Most people find CBCT comfortable because the machine is open—you're not enclosed in a tube like with medical CT. You can see around you during the scan.
Q: How long does it take to get results? A: Images are available immediately after processing. Your referring dentist typically receives them within 24-48 hours, or sooner if systems are integrated.
Q: Do I need someone to drive me home? A: No, there's no sedation or recovery. You can drive yourself and return to normal activities immediately.
Q: Can children have CBCT? A: Yes, when medically necessary. Pediatric CBCT uses lower radiation settings and smaller fields of view. The benefit of accurate diagnosis must outweigh the small radiation risk.
Q: How often can I have CBCT? A: CBCT should only be performed when necessary for diagnosis or treatment planning. Your dentist will determine if and when repeat scans are needed based on your clinical situation.
Key Takeaways
- CBCT provides 3D images of your teeth, jaw, and facial structures
- It uses less radiation than medical CT scans
- Scan takes 10-40 seconds with the entire appointment lasting 15-30 minutes
- It's painless and non-invasive with no recovery time needed
- CBCT is valuable for implant planning, root canals, and complex dental cases
References
- American Academy of Oral and Maxillofacial Radiology. AAOMR Position Paper on CBCT Imaging Parameters. 2023.
- European Society of Radiology. ESR Guidelines on Dental CBCT Indications. 2022.
- National Council on Radiation Protection and Measurements. NCRP Report No. 177: Radiation Dose Management for CBCT. 2022.
- American Dental Association. Dental Radiographic Examinations: Recommendations for Patient Selection and Limiting Radiation Exposure. 2023.
- International Commission on Radiological Protection. ICRP Publication 129: Radiological Protection in Cone Beam CT. 2024.
Medical Disclaimer: This information is educational only. Always discuss your specific situation with your healthcare provider for personalized medical advice.