Paralleling Technique — MFDS Part 1 MCQ
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Correct answer: B — It reduces dimensional distortion of the tooth image
Explanation lettering: D = shown as A · A = shown as B · B = shown as C · C = shown as D
A is correct. In the paralleling technique, the receptor is positioned parallel to the long axis of the tooth and the central X-ray beam is directed perpendicular to both. This geometry reduces foreshortening and elongation, giving a more dimensionally accurate and reproducible image than the bisecting-angle technique. Some magnification can still occur, so B is too absolute. The technique does not inherently shorten exposure time; this depends on the receptor and equipment. A receptor holder and accurate beam alignment are normally required, making D and E incorrect. The bisecting-angle technique may be used when anatomical limitations prevent satisfactory parallel receptor placement, but it is more susceptible to geometric distortion.
Reference: Yen M, Yeung AW. The Performance of Paralleling Technique and Bisecting Angle Technique for Taking Periapical Radiographs: A Systematic Review. Dentistry Journal. 2023;11(7):155. https://pubmed.ncbi.nlm.nih.gov/37504221/