A peg-shaped maxillary lateral incisor is most commonly associated with which of the following?

Correct answer: A. An impacted or palatally displaced maxillary canine

• A. CORRECT. The root of the maxillary lateral incisor acts as the eruption GUIDE for the canine. When the lateral is peg-shaped, diminutive or absent, that guidance is lost and the canine frequently becomes palatally displaced or impacted. This is the guidance theory of canine impaction and is well supported.
• B. Central incisor impaction is usually caused by a supernumerary tooth (mesiodens), an odontoma or trauma to the primary predecessor — not by lateral incisor form.
• C. Peg laterals do occur in cleft patients, but they occur far more commonly as an isolated finding or as part of generalized microdontia and hypodontia.
• D. Primary molar ankylosis (infraocclusion) is unrelated to lateral incisor morphology.

Note: Practical screening: palpate for the canine bulge buccally at ages 10–11. If it is not palpable, or if there is asymmetry between sides, take a radiograph. Extracting the primary canine at the right moment can redirect a palatally displaced permanent canine and avoid surgical exposure altogether — but only if you catch it early.