The amount of soothing that a teething necklace does is highly dependent on bead size and the surface finish of the beads
Larger beads have more of the active soothing agent, succinic acid, than smaller beads.
And a burnished or unpolished surface has more surface area that can transfer that succinic acid. That is because the surface is porous. A polished surface has all the pores closed and succinic acid is blocked.
These necklaces are often INCORRECTLY called raw. There is no such thing as a raw bead. Beads are shaped by polishing. The degree of polishing is the key
Lightly polished or burnished beads are what these are. And they are the most effective.