I am 1.5 years into this process of reversing extraction orthodontics.
Estimating around 6 more months to go.
On the upper arch I have already re-opened 7 mm of space for bicuspids. (you need around 7.5mm of space for implant)
On the bottom I am around 6 mm.
So at this point I am already 90% there as far as re-opening the space for the bicuspids. And I’m 24 years old. Most orthos will tell you it can’t be done, but I am proof it can. They may tell you as an adult you have stopped growing, however the truth is even as adults humans never stop growing. We are constantly replacing our cells, and with appliances it is possible to create new bone growth at the suture that runs in the middle of the maxilla, gradually over time your palate itself actually gets wider.