Dental Radiography Basics
- Dental radiographs, commonly known as X-rays, are used to diagnose hidden dental structures, masses, bone loss, and cavities.
- X-ray radiation penetrates oral structures at different levels, appearing lighter in teeth and darker in caries, infections, and bone density changes.
- The dosage of X-ray radiation received by a dental patient is typically small, equivalent to a few days worth of background environmental radiation exposure.
- Lead shields and aprons are used to reduce incidental exposure for both patients and technicians.
- Digital X-rays are replacing film, offering faster processing and lower radiation exposure.
Intraoral Radiographic Views
- Intraoral radiographic views involve placing the film or sensor inside the mouth.
- Periapical views evaluate the tooth's periapical area and surrounding bone.
- Periapical radiographs are used to detect inflammation, assess periodontal problems, diagnose trauma or fractures, plan extractions, detect unerupted teeth, evaluate endodontic treatments, and assess implants.
- Bitewing views visualize the crowns of posterior teeth and the alveolar bone in relation to the cementoenamel junctions.
- Occlusal views reveal the skeletal or pathologic anatomy of the mouth or palate.
Extraoral Radiographic Views
- Extraoral radiographic views place the film or sensor outside the mouth.
- Lateral cephalogram evaluates dentofacial proportions and malocclusion.
- Antero-posterior radiograph provides a face-forward view.
- Lateral cephalometric radiography is used in orthodontics and orthognathic surgery.
- Panoramic films show a greater field of view, including mandibular condyles and maxillary sinuses.
- Panoramic films were developed by the US Army for quick assessment of soldiers' oral health.
- Panoramic films can detect and localize mandibular fractures and pathologic entities.
- Computed Tomography (CT) scans offer high-quality images and accuracy.
- Cone Beam Computed Tomography (CBCT) generates 3D images and overcomes the limitations of 2D imaging.
Localisation Techniques
- Parallax is used to assess relationships of structures in a 3D object.
- Parallax is used to determine the position of an unerupted tooth in relation to the erupted ones.
- Radiographic localization techniques are used in endodontics, fracture assessment, and bone evaluation.
- Horizontal parallax involves taking two radiographs at different horizontal angles.
- Vertical parallax involves taking two radiographs at different vertical angulations.
- The SLOB rule states that the more distant object will appear to move in the same direction as the tube shift.
- The MBD rule is commonly employed in endodontics to determine the position of the buccal root or canal.
- CBCT can replace parallax radiographs and provide 3D information on impacted teeth.
Faults and Image Quality
- Faults in radiographs can arise due to various factors such as image receptor type, X-ray equipment, and processing materials.
- Some film faults include dark film, pale image, grainy digital image, and foreshortening/elongation of structures.
- Other faults include overlapping proximal surfaces, slanting of the occlusal plane, and cone cut appearance.
- A set of criteria for acceptable image quality has been created.
- Grades are assigned to radiographic images based on their diagnostic acceptability.
- Film reject analysis helps identify and address common errors in radiographs.
- Regular analysis of rejected films can improve the quality of future radiographs.
Dental radiographs, commonly known as X-rays, are radiographs used to diagnose hidden dental structures, malignant or benign masses, bone loss, and cavities.
| Dental radiography | |
|---|---|
| ICD-9-CM | 87.0-87.1 |
A radiographic image is formed by a controlled burst of X-ray radiation which penetrates oral structures at different levels, depending on varying anatomical densities, before striking the film or sensor. Teeth appear lighter because less radiation penetrates them to reach the film. Dental caries, infections and other changes in the bone density, and the periodontal ligament, appear darker because X-rays readily penetrate these less dense structures. Dental restorations (fillings, crowns) may appear lighter or darker, depending on the density of the material.
The dosage of X-ray radiation received by a dental patient is typically small (around 0.150 mSv for a full mouth series), equivalent to a few days' worth of background environmental radiation exposure, or similar to the dose received during a cross-country airplane flight (concentrated into one short burst aimed at a small area). Incidental exposure is further reduced by the use of a lead shield, lead apron, sometimes with a lead thyroid collar. Technician exposure is reduced by stepping out of the room, or behind adequate shielding material, when the X-ray source is activated.
Once photographic film has been exposed to X-ray radiation, it needs to be developed, traditionally using a process where the film is exposed to a series of chemicals in a dark room, as the films are sensitive to normal light. This can be a time-consuming process, and incorrect exposures or mistakes in the development process can necessitate retakes, exposing the patient to additional radiation. Digital X-rays, which replace the film with an electronic sensor, address some of these issues, and are becoming widely used in dentistry as the technology evolves. They may require less radiation and are processed much more quickly than conventional radiographic films, often instantly viewable on a computer. However digital sensors are extremely costly and have historically had poor resolution, though this is much improved in modern sensors.
It is possible for both tooth decay and periodontal disease to be missed during a clinical exam, and radiographic evaluation of the dental and periodontal tissues is a critical segment of the comprehensive oral examination. The photographic montage at right depicts a situation in which extensive decay had been overlooked by a number of dentists prior to radiographic evaluation.
