Main imaging modalities in dentistry
The dentist's toolkit includes a wide range of imaging modalities. Basic methods include extraoral, intraoral, and panoramic radiography, as well as orthopantomography. For more complex diagnostic tasks, computed tomography (CT) and magnetic resonance imaging (MRI) are used. In specific situations, contrast-enhanced methods (sialography, fistulography, maxillary sinusography) and radionuclide diagnostics are employed.
Intraoral radiography can be performed using any x-ray diagnostic equipment, but specialized dental units are considered optimal. There are four techniques, one of which is intraoral periapical radiography. In this method, the patient holds the x-ray film against the oral mucosa of the alveolar bone using their finger from inside the oral cavity.
The problem with traditional 2D methods
Intraoral radiography and rotational panoramic radiography have long been the backbone of diagnostics. However, their main drawback lies in transforming complex three-dimensional anatomical structures into a 2D image. This inevitably leads to projection magnification and geometric distortion. As a result, the clinician receives inaccurate spatial measurements, which can become a critical error when planning orthopedic or surgical interventions.
Cone-beam computed tomography (CBCT) — the 3D imaging standard
Cone-beam computed tomography (CBCT) solves the problem of flat images by providing accurate 3D visualization of the maxillofacial bone structures with high spatial resolution.
The operational principle of the method is similar to panoramic imaging: a diverging pyramidal beam of radiation is used. The system rotates around the patient in an arc from 180 to 360 degrees, capturing a series of basic frames that are then integrated into a volumetric dataset. CBCT is indispensable for surgical navigation and orthodontics, but it has two strict limitations:
- It is unable to visualize soft tissues (unlike MRI or traditional CT).
- It is not suitable for accurate caries diagnostics due to prominent streak and dark-zone artifacts (caused by beam hardening from dense dental restorations).
CBCT in pediatric practice and safety considerations
The field of view (FOV — Field of View) of modern CBCT units ranges from 5 to 13 cm in height. In pediatric practice, it is critically important to adjust the FOV strictly to the area of interest to protect radiosensitive organs, such as the thyroid and salivary glands. If a large field of view is selected, capturing the skull base and cervical spine, the scan must be interpreted by a radiologist, as these areas fall outside the dentist's scope of practice.
CBCT image quality improves when the tube rotation angle is increased to 360 degrees, but this inevitably increases the radiation dose. For orthodontics and implant planning in children, low-dose protocols with a 50% reduction in tube current are frequently used. The radiation dose from CBCT is generally lower than that of standard CT, but noticeably higher than that of conventional dental radiography.
Radiological monitoring in implantology
The success of dental implantology is based on osseointegration — the process of establishing a direct structural and functional connection between the surface of the metal structure and the bone tissue. The primary factor for success is the implant material itself (usually titanium), which must be non-toxic and corrosion-resistant.
On orthopantomograms or tomograms, successful osseointegration is confirmed by:
- The absence of signs of bone rarefaction around the structure.
- The absence of a gap (radiolucent line) between the implant surface (threads) and the bone bed.
- Clinical immobility of the implant (ankylosis).
CBCT excels at "seeing" bone in 3D, but is "blinded" by fillings (beam-hardening artifacts) and completely fails to differentiate soft tissues.
Class and exam questions
How does CBCT differ from traditional computed tomography?
CBCT uses a diverging pyramidal beam and rotates in an arc, compiling a 3D model in a single revolution. It is comparable to or even surpasses CT in the level of detail of skull bones, but, unlike helical CT, it cannot visualize soft tissues.
How is intraoral periapical radiography performed?
This is a technique where the patient holds the x-ray film against the oral mucosa of the alveolar process with their finger from inside the mouth, after which the exposure is taken.
Why is CBCT not recommended for detecting caries?
Due to the beam-hardening effect from metallic or dense restorations, artifacts appear as dark zones and streaks, which can mask or mimic carious lesions.
What else to study on this topic
- Pediatric MRI: sedation methods and motion artifact reduction
- Application of contrast agents in dentistry: sialography and maxillary sinusography
- Low-dose 3D head CT protocols for facial skeleton assessment
- Methods for protecting radiosensitive organs during CT examinations
- Radionuclide diagnostics in maxillofacial surgery
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