P. 663

B.A. Niemiec1
1Southern Califormia Veterinary Dental Specialties, Dentistry, San Diego, USA
Dental Radiograph Units:
Radiographic exposure is controlled by 3 components: kVp (kilovolt peak), MA (milliamperage), and exposure time. KVp controls the “quality” of the x-ray beam. This is the power of each particular x-ray particle which controls the penetration of the beam through tissues.
The quantity of the exposure is controlled by MA and time of exposure. The higher the MA, the more X-rays produced over the time period. Multiply this number by the exposure time and you will get the total number of x-ray units.
Since there is not a signi cant amount of variation
of tissues in oral radiology, the KVP and MA are
set constant on dental radiology units. The only
variable factor is time. This is measured in seconds or pulses. One pulse is equal to 1/60 of a second. Most standard (human) dental radiology units have a digital control for the exposure and it is set by the operator based on a technique chart. Recently, however, veterinary speci c machines have become available which has a computer that sets the exposure based on the size of the patient, the speed of dental  lm used, and the particular object tooth. This can take a lot of the guesswork out of the exposure setting. However, with
a little experience and practice, it is easy to  gure out a setting.
Dental Radiographic Film:
Dental  lm is non-screen  lm. This means that it is directly exposed by the x-ray and does not require an intensifying screen. This gives much more detail than standard radiographic  lm, but requires a higher amount of exposure. It is packaged in its own paper or plastic sleeve, to protect it from light and the oral environment.
There are two types of dental  lm commonly used
in dental radiology. These are Ultra-speed “D” and Ektaspeed “E”  lm. Recently “F” speed  lm has become popular. The difference is in the size of the silver halide crystals and secondary to this the amount of exposure required to expose the dental  lm. “E” speed  lm requires approximately 1⁄2 the amount of radiation for exposure than “D” speed  lm, and “F” speed even less. This decreases exposure to the patient and staff as well as decreases the wear and tear on the x-ray unit. There is
a slight decrease in resolution with faster  lms due to
the larger crystal size, but according to most experts,
the difference is negligible. Therefore, it is recommended in human dentistry to use “E or F” speed to decrease exposure time. They are more technique sensitive, however, in both the exposure and development of the image. This may be frustrating for the novice, therefore
it is generally recommended that practitioners start with “D” speed and advance to “E or F” speed when they are more comfortable with the settings and positioning.
There are several different sizes of dental  lm available (4, 3, 2, 1, and 0). The most common sizes used in veterinary medicine are 4, 2, and 1. Size 3 are bite wings and are generally not used in veterinary medicine. Size
4 (occlussal)  lm is the largest available, it is used mostly in large breed dogs or when taking whole mouth radiographs. For small dogs and cats and most any single tooth radiograph, size 2 (standard) is commonly used. For the mandibular  rst and second premolars, and very small cats and puppies size 1 (or 0) (periapical) are used.
Another consideration in selecting  lm size is cost. Size 4  lm is about 3 times the cost of size 2. Therefore,
if you can use a size 2, it is recommended. However,
it is much easier to position size 4  lms, allowing for much more latitude in positioning. This will result in less retakes. Therefore, the less experienced may consider practicing with size 4  lm and graduating to size 2 when a level of skill is obtained.
Digital Dental Radiology: There are numerous human veterinary digital systems. These are excellent means of obtaining dental radiographs. The only major problem currently is the lack of a number 4 sensor. The major advantages to these systems are the decrease in radiation exposure, rapidity of the development, and that you can reposition the sensor if the view is not correct the  rst time. There is one company, however which makes a size 4 phosphor plate (CR).
Taking a dental radiograph:
Step 1: Patient positioning
Position the patient so that the area of interest is convenient to the radiographic beam. In general
this is where the object is “up”. For maxillary teeth,
the patient should be in ventral recumbency. For mandibular canines and incisors the pet should be in dorsal recumbency. Finally, for maxillary cheek teeth, the patient should be in lateral recumbency with the affected side up. This being said, in our practice virtually all radiographs are exposed in lateral recumbancy. This takes some getting used to, but decreases the number of times a patient must be rolled when doing surgical or endodontic procedures.
An Urban Experience

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