What is CBCT (Cone Beam Computed Tomography)?
CBCT is a specialized three-dimensional X-ray imaging technique that uses a cone-shaped radiation beam to capture detailed volumetric data of the maxillofacial region, providing sub-millimeter resolution with significantly lower radiation exposure (10-100 times less) than conventional CT scans. 1, 2
Technical Fundamentals
CBCT operates by rotating an X-ray source and detector around the patient's head in a single rotation (10-70 seconds), capturing divergent cone-shaped X-ray beams that are reconstructed into three-dimensional images. 1, 3 The technology produces multiplanar reconstructions in axial, sagittal, and coronal planes, allowing visualization of hard tissues and surrounding soft tissues with minimal distortion. 1, 2
Key technical features include:
- Sub-millimeter spatial resolution providing high diagnostic quality for bony structures 1
- Adjustable field of view (FOV) ranging from small (single tooth) to large (entire maxillofacial region), which should be minimized to reduce unnecessary radiation exposure 4
- Significantly reduced radiation dose compared to medical-grade CT, making it more appropriate for dental applications 5, 6
Clinical Applications in Dentistry
Level II (Advanced) Imaging Modality
CBCT functions as a level II examination, indicated only when level I investigations (periapical radiographs and panoramic imaging) fail to provide sufficient diagnostic information for treatment planning. 4 This hierarchical approach follows the ALARA (As Low As Reasonably Achievable) principle for radiation protection. 4
Essential Indications (Strength A Recommendations)
CBCT is essential for assessing the relationship between third molars and critical anatomical structures (mandibular canal for lower molars, maxillary sinus floor for upper molars). 4
When 2D imaging cannot clarify anatomical relationships of teeth with surrounding structures or when internal root structure needs better definition, CBCT is recommended. 4
For complex root canal anatomy, CBCT is the essential technique for accurate assessment, particularly when C-shaped canals or other anatomical variations are suspected, as these are challenging to predict on conventional 2D imaging. 7
Specific Clinical Scenarios
In dental trauma cases, CBCT is indicated when clinical evaluation and periapical radiographs are insufficient, particularly for:
- Confirming suspected root fractures and evaluating fracture lines on the buccal-lingual plane 4
- Assessing tooth luxation that is difficult to evaluate on 2D imaging 4
- Evaluating alveolar bone fractures 4
For dental impactions, CBCT is useful when assessing tooth transpositions associated with impaction. 4
In sinonasal disease, CBCT demonstrates high accuracy for evaluating odontogenic and nonodontogenic sinusitis, with strong agreement between CBCT and sinus endoscopy. 4
Important Limitations and Caveats
CBCT is limited in evaluating soft-tissue structures and is not the imaging modality of choice when extrasinus disease or soft-tissue pathology is suspected. 4 In such cases, contrast-enhanced medical CT or MRI may be more appropriate.
CBCT should never be used as a screening tool or initial diagnostic examination. 4 It must be justified based on inadequate information from conventional radiography, following the principle that all medical exposures involving ionizing radiation require justification. 4
Field of view must be minimized to the specific area of interest to reduce patient radiation exposure while maintaining diagnostic quality. 4
Regulatory Context
All dental radiological practices involving pediatric patients (ages 0-18) must be considered "special practices" requiring periodic dosimetric assessments by a medical physics expert. 4 CBCT equipment requires quality assurance programs, acceptance testing, and performance testing to ensure clinical adequacy. 4