I'm 56 yrs. old, and have an overbite that was never corrected. My bottom teeth were shifting and the lower left front tooth was totally 'tipping' over, causing a large gap which looked like I had a cracked tooth in front!
I've been wearing the trays for over 10 months now, and the bottom teeth are lined up very nicely, and the top teeth have been pushed back and look good.
However, it's difficult for the orthodontist to move the teeth as minor new problems arise as the teeth shift. I would recommend this treatment for older people who just want to straighten up their teeth somewhat.
I wouldn't recommend this for young people who need their bite adjusted, you really need metal braces for that.