Using the teeth formula, how many teeth would a child have at 18 months?

Using the teeth formula, how many teeth would a child have at 18 months?

• A. 12
• B. 14
• C. 16
• D. 18

Answer: (A)

The concept here is the eruption timeline of teeth in the primary dentition. By 18 months, a child typically shows the incisors and the first molars in both jaws, giving a common total of 12 erupted teeth. In the primary set there are 20 teeth overall (10 in each arch), and eruption follows central incisors first, then lateral incisors, then first molars, then canines, then second molars. By 18 months, all four central incisors and all four lateral incisors have erupted (8 teeth) plus the four first molars (one in each quarter of the mouth), totaling 12. Canines and second molars usually come in later, so they aren’t counted at this age.

The concept here is the eruption timeline of teeth in the primary dentition. By 18 months, a child typically shows the incisors and the first molars in both jaws, giving a common total of 12 erupted teeth. In the primary set there are 20 teeth overall (10 in each arch), and eruption follows central incisors first, then lateral incisors, then first molars, then canines, then second molars. By 18 months, all four central incisors and all four lateral incisors have erupted (8 teeth) plus the four first molars (one in each quarter of the mouth), totaling 12. Canines and second molars usually come in later, so they aren’t counted at this age.