Planar (2D) radiography
Conventional methods remain the first line of diagnostics for inflammation, deformities, and trauma. Their main drawback is the conversion of three-dimensional objects into a flat image, which inevitably leads to inaccurate measurements.
- Intraoral radiography. Performed using dental units. There are four techniques, the most common being contact (periapical) radiography. In this method, the patient presses the X-ray film against the mucosa of the alveolar process with their finger.
- Orthopantomography (OPG). Provides an excellent overview of the jaws, all teeth, periapical tissues, and adjacent nasal sinuses at a minimal radiation dose. Note: lateral panoramic views are preferred to reduce errors.
- Extraoral radiography. Used to evaluate the temporomandibular joint (TMJ), skull bones, and sinuses in direct, lateral, axial, semi-axial, oblique, and tangential projections.
- Zonography. Used as an adjunct to OPG. Due to smaller tube rotation angles, thicker slices are formed, which helps reduce the radiation dose.
Three-dimensional (3D) visualization
Planar images are insufficient for precise orthodontic treatment planning and surgical navigation. Low-dose volumetric imaging methods are employed.
- Cone-beam computed tomography (CBCT). Operates on a principle similar to panoramic imaging, but utilizes a diverging pyramidal beam. The system completes a 180–360 degree rotation. Allows selection of a field of view (FOV) from 5 to 13 cm depending on the clinical task (ranging from a localized area to the entire face).
- Visiography. New-generation units provide digital, volumetric, and color data. They help assess the quality of surgical intervention, bone density, and the relationship of teeth to critical structures (floor of the maxillary sinus, mandibular canal).
- Low-dose 3D CT. Used in pediatrics (Helical spiral mode, 100 kV, pitch 0.6). To protect radiosensitive organs in children, modern tube current modulation algorithms in the anteroposterior projection (over the thyroid and mammary glands) are used instead of bismuth shields.
Contrast techniques
Employed for the visualization of ducts, cysts, fistulae, and vascular anomalies using water-soluble agents or iodolipol.
- Sialography: assessment of duct status and detection of sialoliths. Varying volumes are injected: 2–2.5 ml for the large parotid gland, and 1–1.5 ml for the submandibular gland. Contrast volume changes in pathology (increases in parenchymal sialadenitis, decreases in sialolithiasis).
- TMJ arthrography: contrast medium is injected into the joint cavity, followed by zonograms at various positions of the condylar process.
- Maxillofacial angiography: when a vascular neoplasm is suspected, the tumor is punctured, contrast is injected, and radiographs are taken in direct and lateral projections.
Diagnostic radiology of odontogenic sinusitis
Maxillary sinusitis originating from dental roots most commonly follows a chronic course. Patients complain of a feeling of heaviness, purulent discharge with an unpleasant odor, hyposmia (reduced sense of smell), and asymmetric nasal breathing.
Diagnostics are invariably comprehensive (ultrasound, paranasal sinus radiography, targeted radiographs). OPG plays a critical role, allowing the physician to screen for:
- Periapical foci of bone destruction at the roots of molars and premolars.
- Quality of endodontic treatment (root canal fillings).
- Foreign bodies in the sinus (filling material, instrument fragments).
- Deep periodontal pockets.
Mnemonic for sialography dosages: the parotid gland is anatomically larger, thus requiring 2–2.5 ml of contrast, whereas the submandibular gland is smaller—1–1.5 ml is sufficient.
Class and exam questions
How to test for maxillary sinus perforation following tooth extraction?
A nose-mouth breathing test is performed. The patient attempts to exhale through a closed nose: if a perforation is present, an air jet will pass into the oral cavity through the socket of the extracted tooth.
What does the appearance of pus from the tooth socket immediately after extraction indicate?
This is a polyetiological symptom. It may indicate concurrent sinusitis, perforation of the sinus floor (pus draining from the sinus), an infected cyst, or acute periodontitis.
How to prepare an infant for computed tomography?
Neonates and infants are examined while awake using immobilization devices or the "feed-and-wrap" technique. Sedation is reserved exclusively for cases of severe developmental delay and lack of compliance.
What is the limitation of automatic tube current modulation (ATCM) in CT?
The current is automatically increased in dense anatomical areas. Furthermore, in younger children, the cross-sectional shape of the body is more rounded, rendering angular current modulation ineffective.
What else to study on this topic
- Specifics of pediatric CT protocols: selection of reconstruction kernel, pitch, and tube rotation time.
- Patient protection: dynamic collimators to mitigate excess longitudinal radiation (over-ranging).
- Radiographic presentation of chronic jaw osteomyelitis.
- Fistulography of congenital facial and neck fistulae.
- Additional salivary gland imaging modalities: pneumosubmandibulography and digital subtraction sialography.
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