Cone Beam Computed TomographyEdit

Cone Beam Computed Tomography (CBCT) is a radiographic imaging modality that has become central to modern dental and maxillofacial practice. By acquiring a series of two-dimensional projection images with a cone-shaped X-ray beam as the patient or gantry rotates, CBCT reconstructs a three-dimensional volume of the region of interest. This 3D capability provides detailed visualization of hard tissues such as bone and teeth, as well as complex spatial relationships that are difficult to appreciate with traditional two-dimensional radiographs. While CBCT delivers high-resolution images suitable for planning and assessment, it also requires careful justification and dose management, since it generally involves higher radiation exposure than plain dental radiography but less than many medical CT examinations.

CBCT is widely used in dentistry and related disciplines for diagnostic and treatment-planning tasks. Its isotropic voxel data enable precise measurements and virtual simulations for implant placement, endodontic assessment, orthodontic work, and surgical planning. Because CBCT scans cover a defined volume, they can be tailored to the clinical question, balancing image quality with radiation dose. In addition to hard-tissue visualization, CBCT can aid evaluation of the paranasal sinuses, the temporomandibular joint, the airway, and certain pathologies encountered in the maxillofacial region. For many clinicians, CBCT complements conventional radiographs by offering a spatially accurate 3D map of a patient’s anatomy, which can improve diagnostic confidence and the predictability of outcomes.

History

Cone-beam CT emerged from advances in medical imaging in the late 20th century and was adapted for dental and maxillofacial use in the 1990s and early 2000s. Early devices emphasized compact design and affordability for dental offices, while subsequent generations improved detector technology, rotation speed, and reconstruction algorithms. The technology rapidly gained acceptance as clinicians recognized its potential to improve implant planning, endodontic access, and surgical guidance, among other applications, while striving to reduce radiation exposure through optimized protocols and tighter field-of-view options. For contemporary practice, CBCT is now a standard reference in many dental imaging workflows, with ongoing refinements in image quality, dose management, and dose-tracking practices guided by professional organizations such as American Dental Association and American College of Radiology.

Technology and image formation

CBCT uses a rotating gantry that houses a cone-shaped X-ray beam and a two-dimensional detector. As the gantry rotates around the patient, the system collects hundreds of projection images. These projections are reconstructed into a three-dimensional volume, typically with isotropic voxels that preserve geometric accuracy in all directions. Reconstruction methods for cone-beam geometry differ from traditional fan-beam CT and often rely on variants of back-projection algorithms, such as the Feldkamp–D Davis–Kress, adapted for cone-beam geometry. The resulting data set allows clinicians to view multiplanar reformats (axial, coronal, sagittal) and to perform linear and angular measurements with precision.

Key terms to know include the field of view (FOV), which describes the scanned region and can range from small, focused volumes to larger areas that encompass the entire craniofacial complex. The choice of FOV directly influences radiation dose and image detail. CBCT systems also vary in detector technology, voxel size (often in the 0.08–0.4 mm range for clinical work), exposure settings, and image-processing features such as artifact reduction and contrast enhancement. While CBCT excels at hard-tissue imaging, its soft-tissue contrast is generally inferior to that of dedicated medical CT or magnetic resonance imaging (MRI), which is a consideration in cases where soft-tissue detail is crucial.

Radiation safety and dose management are central to CBCT practice. Clinicians follow the principle of ALARA (ALARA) to justify imaging and to optimize acquisition parameters. Dose considerations include not only the selected FOV and exposure parameters but also patient factors such as age and the presence of multiple scans over time. Protective measures, dose tracking, and adherence to evidence-based guidelines help minimize unnecessary exposure, particularly in pediatric patients where sensitivity to ionizing radiation is greater.

Clinical applications

CBCT is employed across a range of dental and maxillofacial scenarios. Common applications include:

Implant planning and placement planning, where accurate assessment of bone quantity and quality, nerve canal anatomy, and sinus anatomy guides implant position. See also Dental implant.
Endodontics, where complex root canal morphology, accessory canals, and periapical pathology can be evaluated in three dimensions. See also Endodontics.
Orthodontics and dentofacial orthopedics, including assessment of tooth position, jaw relationships, and airway dimensions. See also Orthodontics.
Oral and maxillofacial surgery, for assessment of impacted teeth, pathologies, fractures, and surgical approach planning.
Temporomandibular joint (TMJ) evaluation and craniomaxillofacial analysis, to understand joint morphology and degenerative changes.
Pathology and incidental findings, where CBCT can help characterize cysts, tumors, infections, and other osseous lesions in the craniofacial region. See also Pathology.
Airway and sinus evaluation, including assessment of airway patency and sinus anatomy, which can inform treatment planning in sleep-disordered breathing and other conditions. See also Airway and Paranasal sinuses.

Each application benefits from standardized imaging protocols and site-specific interpretation by qualified radiologists or dental specialists. The use of CBCT should be justified by the clinical need and balanced against potential radiation exposure, with consideration given to alternative imaging modalities when appropriate.

Safety, regulation, and ethics

Radiation safety is a core element of CBCT use. Professional guidelines emphasize justification of each scan, optimization of acquisition parameters, and ongoing assessment of cumulative radiation dose, particularly for patients who may require multiple scans over time. In pediatric dentistry, the emphasis on minimizing exposure is heightened due to higher radiosensitivity and longer life expectancy for potential radiation effects. See also Radiation dose and Pediatric radiology.

CBCT imaging also raises considerations about incidental findings—anomalies discovered during imaging that may fall outside the initial diagnostic question. Clinicians must be prepared to manage such findings, including communication with patients and coordination with other specialists as needed.

Limitations and challenges include artifact susceptibility (e.g., beam hardening from metallic restorations), limited soft-tissue contrast, and potential for misinterpretation if the scanner’s technical specifications or the chosen protocol are not appropriate for the clinical task. As with all imaging modalities, CBCT benefits from ongoing education, quality assurance programs, and adherence to evidence-based indications to ensure that the benefits outweigh the risks.

Limitations and artifacts

Metal artifacts from dental restorations or implants can degrade image quality and obscure adjacent anatomy.
Beam hardening and scatter can reduce contrast in regions near dense structures.
Limited soft-tissue contrast makes CBCT less suitable for diagnosing soft tissue pathology without correlation to other imaging modalities.
Patient motion can blur volumes and degrade diagnostic usefulness.
Field-of-view choices may constrain the assessment of adjacent regions if the pathology lies outside the scanned volume.