My 9 year old son is getting the Herbst Device to move his jaw forward. He is also getting braces. Is the most up to date treatment for a lower jar not developing properly?

It's my understanding these devices work well on developing jaws. But, I'm not an orthodontist, so I don't know for sure. If you are unsure about the treatment your son is getting from the ortho you've selected, you might consider having a few other consults. If you are in the US these consults are usually free. Treatment plans can vary a lot from doctor to doctor, so it's important to pick a doctor and treatment plan you are happy with.

It should be OK. Why not trust your orthodontist?

However, braces are painful sometimes.

The Herpst appliance is the normal treatment for under-developed jaws. The orthodontist probably won't put the braces on until all of your sons baby teeth have fallen out (usually around age 12)