A child's bitewing shows teeth S, T, and first molar (tooth #30) erupted. What is the approximate age?

Correct answer: C. 6-7 years old

• A. By 8-9 years, the first permanent molar would already be well-established, not recently erupted.
• B. At 5-6 years, the permanent first molar may not yet have fully erupted. The presence of the erupted first molar suggests at least age 6.
• C. Tooth S (upper right primary second molar) and T (upper left primary second molar) are primary teeth that remain until ages 10-12. The FIRST PERMANENT MOLAR (tooth #30 / mandibular right first permanent molar) erupts around age 6-7. If the bitewing shows both primary second molars (S, T) still present AND the permanent first molar has just erupted — the patient is approximately 6-7 years old.
• D. 7-8 years is possible but the key finding is the JUST-ERUPTED first molar, which places the age at 6-7 (the first permanent molar erupts ~age 6, giving it the nickname 'the 6-year molar').