Elizabeth Vroom, (orthodontist, mother of a youngman with dmd) said -I do have the article mentioned in the ppt's about dental development in dmd. In an australian article (Dental characteristics of patients with Duchenne Muscular Dystrophy Symons A.L., Townsend G.C., Hughes T.E. Journal of dentistry for Children 2002
they suggest (and I am sure this is correct) that mouth breathing make things worse. I myself believe you should start at a young age to train them to hold there tongue more retruded. One of the tricks is to let them click (like you do when you are horseback riding) with their tongue as soon as you see them with their tongue hanging out. Both is NOT evidence based! No "trials" so far.
Ryan will post Elizabeth's ppt. in the next day or so.