I also have a sister who is turning 9 in a couple of weeks. She has had an open mouth posture for most of her childhood, and still has it now, due to adenoid hypertrophy. Her palate is very narrow, and she shows facial lengthening and narrowing, and a tooth pattern that seems like a class 2 division 1 maloclussion. She has very crowded lower incisors. I have urged her to do proper tongue posture, but she finds it very difficult, and still has her lips and teeth apart. She also fails to be diligent in chewing gum one hour per day. Is there anything that I can do to improve her condition? My parents are considering conventional orthodontics for her.
Read this:
http://www.debugyourhealth.com/orthodontics-and-cranial-structure/ . It was posted from a fellow user a few days before, pretty interesting read. And here with tongue they used something that will keep it on the top like something sticky, I mean read it, you are not going to regret it. Then again, I dont expect that you will start the procedures like the massages in the topic since you are only her brother and not a parent and they most likely wont trust you or believe you.
She most likely might often be with stuffed nose and not be able to breath through it. Plus not only that, I have told the thing about the maxilla to at least 6 adults my age and no one cares even the slightest. Just one took interest, but he just listened to what I told him about tongue and posture and does it, but has not researched the topic himself in any way. Even my ex, who studies orthodontic and teeth medicine(literal translation sorry lol), has worn orthodontic devices for 8 years, which were removed like a year ago and has no place for her teeth, so they start moving the moment she stops wearing those devices and her doctor wants to remove some of her teeth to make place. Despite this, she has absolutely no interest in orthotropics, tongue posture etc. My point is, what is left for a kid, pretty small chance she realises what you are trying to tell her, so she can be like oooohhh and start doing it with motivation. So try to convince your parents of the orthotropics and that most likely wont definitely be easy. Last resort, speak with the orthodontist himself, get out of your comfort zone(saying it in case you are pretty shy, but want to do the right thing), search for an orthodontist who believes in what the orthotropics teach, some users of this site have managed to find such people. But I believe that you should work with your parents in the first place. And if she has stuffed nose, dont use bought medicine, there are some pretty good ways to wash the nose, which I still havent done though, so read about them.
So, considering I saw absolutely amazing results from chewing gum for 6 months(not to me, but to another fella) I have been wondering how so many of you chew gum but barely have results, because that dude changed the shape of his whole head for such a short time. And I just came to realisation. The point of chewing gum is to streghten the muscles which in turn reshape the face. Thing is, I realised, most of you are not in caloric surplus but just chewing and just like any other muscle most likely those masseter muscles neither get bigger nor stronger (same reason my squat and bench press have stayed the same for a whole year, but man I need to eat 5 times a day for a surplus), so you are just doing nothing. So for your case, try to enter a surplus, at the same time start lifting if you are not, because in my opinion being in caloric surplus is much much harder than lifting, so hey, dont miss the opportunity.
Another thing, if your sister is that bad, I dont know how wise it is to chew gum everyday like this. When the maxilla is recessed is not in optimal position for chewing and here comes the TMD, what happened to me on the second day, popped my TMJ. Since she is just 9, start with tongue I guess.
Also, sadly, I have no idea about the wisdom teeth. I have been wondering the same, since I am already in the age in which they come out, but still havent had any pain. I wonder if the are impacted or even when my maxilla is narrow if there is place, since I also dont wont to remove them. But since yours are already impacted, I dont know man, I dont see how if you dont remove them, you are going to straighten them, so they dont make a problem and if inflammation starts etc. But hey, dont let that make you sad, I just dont know, not saying that there is no way, just keep searching..