A panoramic radiograph shows a tooth impacted in the area of the upper right canine. The primary canine is present with an intact root. What is the impacted tooth?

Correct answer: C. Tooth #6 (permanent maxillary right canine)

• A. Tooth C is the primary canine, which the stem tells you is present in the arch with its root intact. It cannot simultaneously be the impacted tooth.
• B. An odontoma is a radiopaque mass of disorganised dental tissue, not a recognisable single tooth with normal crown and root form.
• C. CORRECT. The primary canine is visible with an INTACT root — so the primary tooth is accounted for and is not the impacted one. The retained primary canine with an unresorbed root is itself the classic clue to an impacted permanent successor, because normal resorption of the primary root is driven by the erupting permanent tooth. The impacted tooth in the maxillary right canine region is therefore TOOTH #6.
• D. A supernumerary in this region (a mesiodens is the commonest) would typically be smaller and morphologically atypical, and would not explain the retained primary root.

Note: A retained primary canine past the expected exfoliation age warrants a radiograph — impacted maxillary canines are the second most commonly impacted tooth after third molars, and early detection allows interceptive extraction of the primary tooth.