Do braces elastics have an effect on the jaw bone?

You can use elastics for all kinds of things. You can use it to close the bite, you can use it to shift the jaw forward and backwards. Elastic is a very broad term, so it depends again on the case, what your dentist is trying to achieve. Basically elastics just pull things together so you can use it in lots of different applications. Whether it really affects the jawbones, probably not too much. It’s more like it moves the teeth more than the jaw bone. It’s quite hard to actually get bone movement in an adult. As for the jaw, the lower jaw may slide. There’s no real way to know, some corrections are a bit more unstable. Unstable meaning that after you finish the braces and stop the elastics, the jaw starts to slide back into the original position again.