A patient has an impacted upper second molar. They were wearing a lower retainer, but the upper retainer broke, causing spacing on the left side. What is the most likely cause of the unerupted upper second molar?

Correct answer: A. Lack of space

• A. ✅ Correct. The broken upper retainer allowed teeth to drift, creating insufficient space for the upper second molar to erupt. Lack of arch space is the most likely direct cause.
• B. ❌ No supernumerary tooth is described in the case.
• C. ❌ While improper retainer use led to the spacing issue, the direct cause of non-eruption is the resulting lack of space.
• D. ❌ Ankylosis would present differently and is not supported by the case description.