Dental Assistant Practice Exam

Which radiographic technique is based on the concept of isometry?

1. Paralleling technique

2. Occlusal technique

3. Bisecting angle technique

4. Bitewing technique

The correct answer is: Bisecting angle technique

The bisecting angle technique is grounded in the concept of isometry, which involves the geometric relationship between two triangles. In dental radiography, this technique requires the film or sensor to be positioned at an angle between the long axis of the tooth and the angle of the resultant central ray of the x-ray beam. By doing this, it ensures that the geometry of the resulting radiograph accurately reflects the shape and dimensions of the tooth and its surrounding structures. This technique is predicated on the idea that if two triangles share a common side and the angles opposite to that side are equal, the two triangles are of equal size and shape. By bisecting the angle formed by the tooth and the film, a radiograph can depict the tooth’s anatomy without distortion, providing a more accurate representation of the tooth compared to other techniques. In contrast, other techniques such as the paralleling technique maintain a fixed relationship between the film and the tooth, which is not dependent on the concept of isometry, while the bitewing technique focuses on capturing the interproximal surfaces of teeth, and the occlusal technique is used to view the occlusal surfaces. Each of these methods serves specific purposes in dentistry, but they do not employ the isometric principles