Parallax Technique Ectopic Canine — MFDS Part 1 MCQ

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ModerateRadiologyParallax Technique Ectopic CanineMFDS Part 1

A 12-year-old patient has a clinically suspected ectopic maxillary canine. There are no clinical features suggesting adjacent-root resorption, and conventional imaging is expected to provide adequate information. Which radiographic investigation is most appropriate for localising the canine in the buccopalatal plane?

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Correct answer: C — Paired maxillary periapical radiographs using horizontal parallax

The correct answer is C. Two maxillary periapical radiographs taken with a horizontal tube-head shift apply the parallax principle and permit buccopalatal localisation of the ectopic canine. If the canine image moves in the same direction as the tube shift it is palatal; movement in the opposite direction indicates a buccal position. Bitewings do not normally demonstrate the full canine region sufficiently for localisation. A lateral cephalogram and a panoramic radiograph alone provide limited buccopalatal information because of superimposition. Small-field CBCT can show the three-dimensional position and adjacent-root resorption, but UK guidance does not recommend it routinely; it is reserved for selected cases where conventional radiographs do not provide enough information for treatment planning.

Reference: Royal College of Surgeons of England, Faculty of Dental Surgery. Management of the Palatally Ectopic Maxillary Canine, Radiographic Examination and Table 1. 2022, revised 25 January 2023. https://www.rcseng.ac.uk/-/media/files/rcs/fds/guidelines/2management-of-the-palatally-ectopic-maxillary-canine--revised-with-edits-25-jan-2023.pdf