We took DS1 privately to an orthodontist just when he was 7yo because he had a high narrow palate, caused by a posterior tongue tie which had gone undiagnosed until then.
His lower jaw was already bigger than the top one and he could not put his bottom teeth behind his top ones and it was clear that there was not going to be enough room for his adult teeth.
His tongue tie was revised and he began wearing braces and headgear to expand his palate and draw out his upper jaw and mid section of his face.
This also opened up his nostrils and stopped the mouth breathing which had probably been the cause of the underbite. He stopped snoring and grinding and his sleep became much more peaceful.
2 years on, he is just wearing the braces at night as a retainer and we are waiting to see how his adult teeth end up before deciding if he needs fixed braces.
Without this early intervention, he would certainly have been looking at multiple extractions, possibly jaw surgery, who knows.
I have tried to post a picture of his braces, not sure if it will work! They didn't hurt and worked very gently to guide the growth of his jaws.
I am absolutely delighted with the results and know that it was 100% worth every single penny.