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CBCT in Dentistry

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Cone-beam computed tomography (CBCT) has rapidly become a popular and frequently used imaging modality in dentistry. Read the article to know more.

Medically reviewed by

Dr. Lekshmipriya. B

Published At March 26, 2022
Reviewed AtAugust 9, 2023

Introduction:

Cone beam computed tomography (CBCT) equipment revolutionized the field of oral and maxillofacial radiology. Due to its small size, low cost, and reduced ionizing radiation exposure as compared to medical computed tomography scans, CBCT was quickly adopted into dentistry settings. The CBCT provides minimally distorted 3D (three-dimensional) examination of the craniofacial area, similar to medical CT (computed tomography) scan.

How Image Reconstruction And Processing Takes Place in CBCT?

Cone beam imaging technology, most commonly called cone-beam computed tomography (CBCT), radiographically images the object in question in the axial, coronal, and sagittal planes.

In computed tomography, the structure of an object is always obtained by penetration of X-rays. The detector cells acquire X-ray measurements that measure the amount of radiation penetrating the source in different directions. This is referred to as image acquisition. After the completion of image reconstruction in different planes (mainly sagittal, coronal, and axial), the computer components will store and make the CT (computed tomography) image available for display in any form of imaging software.

Unlike CT scanning, CBCT uses collimators that block the X-ray emission into undesired areas other than the object to be exposed or imaged. Immediately after the step of image reconstruction, the image needs to be processed by choosing a field of view (FOV), a region in space where the image is obtained.

How Is the Image Attenuation and Accuracy With CBCT?

Attenuation in radiography is the process by which the number of particles through the radiating X-ray beam is absorbed and scattered so that the radiation exposure to the subject is reduced. Attenuation is measured in absolute events of inverse length (mm-1 or cm-1). In CT and CBCT, attenuation is measured in Hounsfield units (HU).

The importance of attenuation in CT and CBCT scanning is that the reconstructed image is converted to HU and then made available for display in the imaging software in the computer systems. However, as a result of CT attenuation, there are certain artifacts or radiographic changes like beam hardening. Beam hardening is mainly seen in two different manifestations of either streaking or cupping artifacts. In streaking, the image obtained appears to be distorted with multiple dark bands, while in cupping artifacts, the center of the image is affected and appears dense. If these artifacts are left without any rectification in the final image then the resultant image not only appears dense but also distorted which can be differentiable only to clinicians.

In CBCT, the image dimension is represented by voxels. The voxel elements are isotropic, meaning they represent the absorption of the X-rays uniformly in every direction (which is a great advantage because in all the three major orthogonal planes), the image acquired can be measured equally in terms of voxel elements. The voxel sizes used in CBCT also vary as they are available in different sizes as in 0.2 mm, 0.3 mm, and 0.4 mm. The voxel size depends on the size of the unit detector of CBCT. In advanced CBCT imaging, a lesser voxel size is used as the greater the voxel size, the lesser the resolution of the resultant radiographic image.

What Are the Components of CBCT?

Along with these design changes, better stabilization devices for the patient's head and chin rest have been modified over the years. Mechanical changes included the switch to smaller, flat-panel silicon detectors with better image quality compared with the bulkier, cumbersome, and more costly image-intensifier detectors. The main components of a CBCT system are:

  • A rotating gantry in which the patient stands or sits (that moves the X-ray to the object source and fires the beam to the detector cells).

  • The X-ray source.

  • Detector arrays with rejection grids (silicon detectors or amorphous silica detectors).

  • A computer that runs imaging software for image reconstruction and storage.

The stored image is then displayed.

What Are the Applications of CBCT?

Oral and maxillofacial radiology over the last few decades has rapidly advanced as a result of the continuously expanding newer age concepts on which CBCT is based upon.

  • Apart from the advantage of minimal distortion, two-dimensional radiography in dental imaging like OPG (orthopantomogram) often is associated with superimpositions or distortions that are not captured in three-dimensional imaging of CBCT software.
  • The user-friendly software of CBCT offers basic imaging and editing tools to the operator and helps them to observe the view of captured tissues in different modes. For example, CBCT software can be used to assess the tissues in multiplanar views, oblique slicing, curved slicing, and also in cross-sectional or oblique and coronal views. This multidimensional study is of the highest use to the dentist as morphologic characteristics, and the dimension of alveolar bone can be properly assessed prior to dental implant placement.
  • One more major application of CBCT software is that it enables the viewer to generate projections of the captured image virtually without any magnification or distortion. The volume visualization of the image is also done efficiently, thus excluding all gray values. Direct and indirect volume rendering functions are a part of all CBCT software for proper image assessment and manipulation to accuracy.
  • Over the course of the past 15 years, there are now numerous CBCT applications in many software formats that are helpful but not limited to dental diseases or anomalies like vertical root and dentin fractures, jaw tumors, prosthodontic evaluations, and advances in orthodontic or orthognathic and implant patient evaluations.
  • Mechanisms for surgical or prosthetic splint design and the CBCT scan data capacity to bridge with computer-aided design or manufacturing image files are useful for the fabrication of various dental restorations. CBCT is now a well-accepted diagnostic tool for the care of dental patients.
  • The ability of CBCT manufacturers to use various aspects of imaging technology in cost-effective and efficient practicality makes the numerous CBCT applications widely used in the imaging for nine different yet main branches of dental medicine ranging from implantation, oral surgery, and endodontics or root canal treatment. It facilitates implant and prosthodontic rehabilitation by synchronously planning and subsequently milling coronal restorations for teeth and root form implants.

The dentistry related applications also include;

  • Dentoalveolar abnormality detection in maxilla and mandible (upper or lower jaw), vertical root fractures, jaw tumors, dental cysts, and sinus infections.

  • Prosthodontic evaluations.

  • For assessment of patients in orthodontic or orthognathic surgery.

  • Implant patient evaluations.

Conclusion

CBCT is the pioneer of dental three-dimensional imaging. Currently, it is used for a wide array of applications. The software is specially used for surgical and prosthodontic splint design. Its capability to scan data for the bridge with CAD (computer-aided-design)/CAM (computer-aided-manufacture)image files and for fabrication of various dental restorations makes it the most reliable technology at hand. As the demand for CBCT technology increases, so will the number of new applications for improved diagnostic techniques.

Frequently Asked Questions

1.

What Are the Advantages of CBCT in Dentistry?

The advantages of CBCT in dentistry are:
 - Lower effective radiation doses.
 - Lower costs.
 - Fewer space requirements.
 - Easier image acquisition.
 - Interactive display modes such as multiplanar reconstruction are helpful in maxillofacial imaging

2.

What Is the Need for CBCT?

 - Oral implantology: for planning dental implants to determine, measure, and localize jaw bone. 
 - Dento-maxillofacial surgery: diagnosis of dental trauma, impacted teeth, visualization of abnormal teeth, cleft palate.
 - Image-guided surgical procedures: implants, impaction, orthodontic treatments.
 - Endodontics: root canal treatments
 - Orthodontics: orthodontic treatment for malaligned teeth and orthodontic surgery.
 - Assessment of dentomaxillofacial region

3.

What Is the Difference Between CBCT and CT?

Difference between CT and CBCT:
 - CT is a fan-shaped X-ray beam, while CBCT is a cone-shaped X-ray beam.
 - CT device requires a large space in which a patient bed is inserted, while CBCT is more compact and suitable for dental clinics with limited space availability.
 - Based on the device's design, the patient's position during a CBCT is placed inside the device in a standing, sitting, or supine position. A bite peg for patients to bite on to stabilize the head and separate dental arches. In a CT scan, the instructions are the same as in a CBCT, but the scan is done in the supine position, in which the patient’s head is rested inside the holder lined with foam sheets or pads.
 - CBCT is designed for dental use; the viewing software is tailor-made for dental purposes, whereas the CT device is not only specific to dentistry. Users must export data to CBCT viewing software or a third-party DICOM viewer.
 - CBCT is designed to visualize bony structures in the dental and maxillofacial regions, does not visualize soft tissues, and is disadvantageous compared to CT.
 - CBCT has lower radiation than CT.

4.

What Are the Three Limitations of CBCT Imaging?

The limitations of CBCT imaging:
 - Detection of isthmuses.
 - Does not image soft tissues.
 - The movement of the patient causes artifacts.

5.

Is CBCT Advised for Root Canal Treatment?

CBCT is optional in all cases of root canal treatment, as it is not a common screening tool. But it can be a standard tool in some endodontic therapies.

6.

What Are the Advantages of CBCT Over OPG?

 - CBCT is more accurate than OPG.
 - Lower radiation dose.
 - Improved image quality.
 - Increased flexibility.

7.

Does CBCT Determine a Cracked Tooth?

CBCT can be used to detect a cracked tooth as it provides high-resolution 3-D images of dental structures, including the roots and surrounding structures, which allows more accurate detection of cracks in teeth. It also includes information about the extent and location of the crack that aids in the treatment plan.

8.

How Much Does a CBCT Imaging Cost?

CBCT costs vary and depend on several factors, such as location, facility, and type of scan performed. However, the benefits and accuracy of tests outweigh the costs.

9.

Does CBCT Help in Diagnosing Tooth Decay?

CBCT helps diagnose tooth decay, but clinical examination plays an important role. As CBCT scans provide 3D images of dental structures, including teeth, they allow for early detection of decay or cavities, along with the location and extent of the cavity.

10.

How Much Time Does a CBCT Scan Take?

A CBCT scan takes a few minutes, depending on the type of scan performed and the machine used. The patient preparation time is shorter and involves the removal of jewelry, metal objects, and dentures that interfere with the scan. The average time ranges from 15 to 30 minutes.

11.

When Does a Dentist Ask for a CBCT Scan?

A dentist asks for a CBCT scan in certain conditions, such as dental implant planning and root canal treatment, when a detailed and comprehensive understanding of dental anatomy is needed to evaluate jaw bone quality and quantity and the placement of dental implants.

12.

Will CBCT Help in Pathological Diagnosis?

CBCT scans evaluate osseous pathology in the maxillofacial skeleton, such as cysts, benign and malignant tumors, inflammatory conditions, paranasal sinus disorders, and soft-tissue calcifications.

13.

Which Is Better, CBCT or CT?

CBCT is better as it has lower radiation exposure, lower costs, a smaller space requirement, easier image acquisition, and interactive display modes such as multiplanar reconstruction. In addition, CBCT provides more accuracy than CT.
Source Article IclonSourcesSource Article Arrow
Dr. Achanta Krishna Swaroop
Dr. Achanta Krishna Swaroop

Dentistry

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3d dental scancbct scan
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