So my argument starts with the MSE device (Maxillary skeletal expander), which is a device that will expand your maxilla, as the name says. The way it works, is by putting a device in the roof of your mouth (the palate) attached to your mollars and premollars, then u have to put a tiny screw into the device and pull it, that is gonna apply pushing force (about 10-20 pounds (4.5–9.1 kilograms) per side, or 20-40 total. But can make up to 50-100 pounds (22.7–45.4 kilograms) if the sutures not open), Isaacson & Ingram (1964,
Angle Orthodontist), Lee et al. (2016,
Korean Journal of Orthodontics) And the force applied is NOT continouos, its just a burst of force applied, and then gradually decreases as tissue adapts. Even tho, towards the last phase of the MSE the device does use a passive retention force (2-4 pounds(1kg-1.8kg) after some hours, 0.1-1 pound(0.0445kg, 0.5kg) a day or two after) , its a force lower than the active force (the one that uses a screw).
Thumbpulling, as the MSE, its about applying presure on specific points in your palate to widen your maxilla. The principles are the same, the difference are the means.
As i said before, the MSE has about 10-20 pounds of pressure applied on the roof of your mouth when activated, which means thats about enough force to move the soft part of the palate. Well, a single thumb, on an average male , can push 15-25 pounds (6.8kg -11.3kg) or also 30-50 pounds total (13.6–22.7 kilograms)), (
https://www.mdpi.com/2076-3417/10/1/194)
Which is clearly more than enough to move your maxilla. Of course, u cant be using all of your force all the time because you are gonna get tired, but the change is possible, even if u can only use your thumbs, thats what im trying to proof.
The counter, of course, is that it doesnt have any passive retention to keep the tissue expanded. HOWEVER, we do have mewing, which is not near to the MSE resting force, but is the most similar thing i could think about. When mewing the tongue applys 1 pound of force or 0.5 kg.