I have got a few questions in to my other blog about Twin Blocks, so I'll answer them here. The most common ones are about speaking with twin blocks and twin blocks making the lower jaw seem prominent. This article is about the lower jaw and chin.
Typical questions are along the lines of:
Help, I'm 13 and just got my twin blocks this week and it makes my chin look massive!
Will my face look like this forever?
I can't give specific orthodontic advice to people that aren't my own patients, so the general advice I give is to talk to your orthodontist about your own situation - but here's a general answer.
Twin Blocks are one of the most commonly used braces for sorting out big overjets* fast, so it’s not an unusual thing for an orthodontist to suggest if that's the main problem. They tend to work on both jaws, pulling the top teeth back, pushing the lower teeth forward, encouraging some extra growth in the lower jaw, and discouraging it in the top.
All of these things take time to happen, but the only difference you can see at the start is the lower jaw coming forward, because that’s the only one that moves!
When you wear the twin blocks together, the jaw muscles have to stretch and act a bit like an elastic band pulling the top teeth back and the lower ones forward. Over time, you can expect that the lower jaw won’t be as far forward as it is now because the top teeth have come back a bit to meet it.
The chin is at the front of the lower jaw, and that's usually well in front of the teeth, so when twin blocks are made they're designed to move the lower teeth forward until they meet the top teeth at the front, so the chin comes even further forward and is more noticeable.
You chin might seem even more prominent since you're used to it being much further back before you started wearing the twin blocks!
Orthodontists expect that any correction that they can get will slip back a bit, so they usually try to "Over-correct" which in this case means moving the lower teeth to a point further than they'll end up because it's pretty much inevitable that they'll move back another millimetre or three.
So if you combine that with the forward movement of the lower teeth that you will get, and the backward movement of the upper teeth you can expect that the lower jaw will not be nearly as prominent as it looks when you start the twin blocks.
How far should the lower jaw go forward? Well you can have a look at the blog post I did on profiles of famous actresses and look at these. If you draw a line between their chin and their nose their lower lip should be on that line (although in many cases in this group it's a little behind the line).
Hope that helps!
