The paralleling technique produces the least image distortion because the tooth and the image receptor are positioned parallel to each other, and the X-ray beam is directed perpendicularly to both. This ensures that the image accurately represents the true dimensions of the tooth without foreshortening or elongation. In contrast, the bisecting angle technique relies on estimating the bisecting line, increasing the chance of distortion. Proper alignment in the paralleling technique also reduces superimposition and produces more consistent, reproducible images, essential for accurate diagnosis and treatment planning.

Reference: White and Pharoah, Oral Radiology, 7th Edition.