Paralleling Technique Dental radiography advantages and disadvantages
Paralleling Technique (Advantages)
There are two techniques for taking periapical films, the paralleling and the bisecting angle techniques. When comparing the two techniques, the advantages of the paralleling technique are:
1. Better dimensional accuracy: the paralleling technique results in less distortion of the image of the teeth. (The shape of the teeth and the relationship of the teeth to surrounding structures is more accurate).
2. When using the paralleling instrument with the aiming ring, the alignment of the x-ray beam is simplified.
3. It is easier to standardize films. Because you are using the positioning instrument, it is easier to position the film in approximately the same position at different appointments. This can be helpful if you are trying to compare the appearance of a periapical lesion from one visit to the next.
4. Head position is not as critical. Because of the paralleling instrument, with its aiming ring, it is easy to properly align the x-ray beam no matter how the head is positioned.
When the long axis of the film is parallel with the long axis of the tooth, the image of the tooth on the film looks the same as the tooth itself (no distortion). The image will be slightly larger than the actual tooth (magnification), but the shape is the same.
Paralleling Technique (Disadvantages)
When comparing the paralleling and bisecting angle techniques, the paralleling technique is:
1. Less comfortable. Because the film is usually more upright when using the paralleling technique, it impinges more on the palate or floor of the mouth, thus making it more uncomfortable.
2. More limited by the anatomy of the patient’s mouth. A shallow palate or floor of the mouth makes it harder to position the film using the
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