Extraoral radiography Flashcards
Extraoral radiography
Extraoral radiography: outside the mouth.
Extraoral radiography are taken whe large areas of the skull or jaw must be examined or when a patient cannot open his or her mouth for film placement.
Extraoral radiography do not show the details as well as intraoral radiographs do. Extraoral radiography are useful for evaluation large area of the skull and jaws, they are not adequate for detecting subtle changes such as the early stages of the dental caries or periodontal disease.
There are many types of extraoral radiographs. some types are used to view the entire skull, other types are focused on maxilla and mandible.
Panoramic radiographs
Panoramic radiographs: helps visualiz e the entire dentition in both crches, along with maxillary sinuses and nasal cavity.
Panoramic radiographs shows dentition and related structures on a single film. some types of Panoramic units operate with the patient in seated position. other tpes require the patient to be in a standing position. Regardless of the type of machine, you must follow the manufacture’er instructions carefully.
Term panorama means “ an unobstructed view of the region in any direction”
Panoramic radiography, the film and tube head rotate around the patient to produce a series of indivdual images. when the series of images are combined onto a single film, an overall view (panorama) of the maxilla and mandible s created.
Facts: becuase the image on the panoramic film are not as clear or well defined as the images on intraoral film, bite-wings are used to supplement a panoramic film to detect caries or periapical lesions.
The focal trough
The film for extraoral radiographs comes in various size, but it is much larger in size than intraoral films. it comes in packages of 50-100 films per box and is extremely light sensitive (even to the darkroom light if it left exposed) It must be handled and loaded into the cassettes in darkroom. The film cassette is opened, a film is placed inside and the cassette is closed and securely latched. You check the latch to ensure that the film is closed into the cassette properly and box of film is covered to avoid exposure to light.
The focal trough: imaginary horseshoe shaped three-dimensional area. This is a very important concept because many errors in technique are caused by improper positioning of the patient’s jaws within the focal trough.
when the jaws are positioned with this area, the radiograph will be clear. when jaes are positioned ouside this area, the images on the radiograph will appear blurred or indistinct.
Components of panoramic unit
- panoramic x-ray tube head
- head positioner
- exposure controls
The head positioner
each panoramic unit has a head positioner that is used align tthe patient’s teeth as accurately as possible. each head positioner consists of chin rest, notched bite-block, forehead rest, and lateral head supports or guides.
Each panoramic unit is different, and opertor must follow the manufacturer’s instructions on how to position the patient in the focal trough. several errors can occurs in panoramic radiograph if patient is not properly prepared an positioned.
- Ghost image: caused by teh failure to remove earrings, dentures, other radio dense object. looks like a real object except that it appears on the opposite side of the film.
-Lead apron artifact: if lead aprone is placed too high, or if lead apro with a thryoid coolar is used a corne shaped radiopaque results.. to avoid this error, place the lead apron lower around the patient’s neck.
- Improper tongue placement: if the tongue is not placed on the roof of the mouth, a radiolucent shadow will be superimposed over the apices of the maxillary teeth.
Chin tipped upward: if chin is tipped upward, the radiograph will exhibit a “ reverse smile line” and detail will be lose.
Chin too low: when the chin tipped downward the radiograph exhibits an “exaggerated smile line” and the condlyes are not visible.
POsitioning of the teeth
be sure that the patient’s anterior teeth are in the frooves of the bite block. if the patient’s teeth are not positioned in the groove on the bite-block and are either too far back on the bite block or posterior to focal trough, the anterior teeth appear “fat” and out of fouce on the radiograph.
If the patient’s anterior teeth are not positioned in the groove on the bite block and are either too far forward or anterior to the focal on the bite block and are either too far forward or anterior to the foral trough, the teet will appear “skinny” and out of focus. If the patient’s spine is not straight, the cerical spine will appear as a radiography artifact in the center of the film and obscure diagnostic information.
Skull radiography
several types of skull radiography
- Lateral cephalometric projection: most common type. used to evaluate bones of the face and skull incclusing trauma, disease, or facial abnormalities. it is used for orthodontic purposes.
- Posteroanterior projection: used to evaluate facial growth and trauma, disease, and facial development.
-submentovertex projection: not common, use in dental offices evalutes the position of the condyles, base of the skull ,and fractures if the zygomatic arch.
- Reverse towne’s projection: not common use in enatl office, evaluates fractures of the condylar neck and ramus.
water’s projection: used to evaluating fractures of the face, sinuses, the maxilla, zygomatic arches, the orbits of the eyes, and coronoid process.
Extraoral radiographs
Extraoral radiographs provide images of lager area such as sull and jaws. In some instanes, and extraoral film might be necessary for a handicapped patient who is unable to tolerate the plamement of intraoral film. Extraoral film also is useful in patient’s who are uncooperative and refuse to open their moths
Extraoral radiographs can taken with the use of the standard inteaoral x-ray machine. special head position and beam- alignment devices can be added to the standard x-ray unit to aid patient positioning. Panormaic x-ray units also can be fitted with a sprcial device know as a cephalostat (films holder and head positioner that allow the operator to easily position the patient).
A grid is device used to decrease film fog increase the contrast of the radiographic images. it does this by reducing th amout of the scatter radiation ( x-ray that bounce off bones and teeth) reaches and extraoral film during expoure.
Lateral jaw projection
Lateral jaw projection: view the posterior region of the the mandible. this type f projection is very useful for patients with limited jaw opening or cannot( or will not) tolerate intraoral film placement. Does not provides as much diagnosis information as a panormaic radiograph.
Lateral jaw projection techniques:
- Body of mandible projection: evaluate posterior region of the mandible, including impaced teeth, fractures and lesions. The cassette is palced directly on the patient’s chehk. One disadvantage is that patient must hold the cassette.
- Ramus of mandible projection: evaluate impacted third molars, large lesions, and fractures that extend into the ramus of the mandible. the ramus form the angle of the mandible to the condyle is visible in this projection.
Digital radiography
advances in digital technology have led to a unique “filmless’ imaging system know as digial radiography.. Introduced in 1987, digital radiography has influenced both how dental disease is recongized and howit is diagnosed. in the last two years, the use of the digita radiography has increased rapidly in general and specualty dental practice. serveral companies are producing digital radiography systems.
Digital radiography equipment
equipment for Digital radiography
- dental x-ray
- intraoral sensor
- computer
Digital radiography used sendor, instead of film to capture a radiographic image. the x-ray beam strikes the sensor and an electrinic charge is produced on the surface pieces and the information is transmitted to computer. software on the computer is used to store the image electronically. the image is displayed on computer screen rather than on film. the term image (not radiograph) is used to describe the pictures that are produced.
Types of Digital radiography
-Direct
-Indirect
- storage phosphor
the difference between these methods lies in how image is obtained and what size the receptor plates are available (example; panoramic).
Digital radiography requires much less x-radiation than conventional radiograph because the sensor is more sensitive to x-rays than is conventional film. Exposure times for digital radiography are 50-80% less than that required for radiography sing conventional film. With less than that required for radiography using conventional film. With is radiation, the does absorbed by the patient is significantly lower.
No film is a Digital radiography component .
