Tooth J is a primary second molar.
Here's a breakdown of primary teeth and their designations, according to the provided reference:
| Tooth Designation | Type |
|---|---|
| A, J, K, T | Primary second molars |
| B, I, L, S | Primary first molars |
| C, H, M, R | Primary canines |
Therefore, based on the reference, the designation 'J' specifically refers to a primary second molar.
