A 12-year-old patient completed orthodontic treatment. The upper right second molar has erupted but the upper left has not. What is the most likely explanation?

Correct answer: D. Normal variation in eruption timing

• A. ❌ A retained primary molar was not mentioned in the case.
• B. ❌ Arch space would have been addressed during orthodontic treatment.
• C. ❌ Impaction requires radiographic evidence — cannot be assumed without imaging.
• D. ✅ Correct. Asymmetric eruption of up to 6 months between sides is considered within normal limits. Without radiographic evidence of impaction or pathology, normal eruption timing variation is the most likely explanation.