Posted by: @dawurkz

From orthotropics video 

Orthotropics4 years ago

Important note; modern adults (or anyone over the age of 9) tend to have a molar width of 29 to 34mm. Anyone with 35 to 38mm will find it much easier but still very hard to make progressive improvements without any formal therapy, and as a rule of thumb when I finish therapy any one who can maintain 38mm or more without retainers tends to maintain good alignment almost indefinitely, with a minimal effort. During childrens treatment expand to 42mm for a girl and 44mm for a boy, clearly some of this is tipping of the molars. Ancient man had an inter-molar width in the high 40's to low 50's. #mikemew

I just watched that video making before making that thread, I already know know about the imw for a long time but I'm also wondering about the inter canine width which I can find anything on.