“…The literature reports that children who have chronic mouth breathing may show significant changes in the craniofacial development, with changes in both bone and muscle tissues, that is, several structural changes of the speech organs, such as: hypotonia of the jaw elevators (masseter muscles) , tongue hypotonia, changes in the tongue resting posture, as well as in the orbicularis oris (the short upper and everted lower lip) 29 and mentalis muscles, all of which impair the stomatognathic functions, such as speech, swallowing and chewing in addition to vocal changes [29][30][31][32][33] . As shown in Table 3, the assessment of the orbicularis oris muscles was included in 9 studies (64.2%) 15,17,20,21,[23][24][25]28,30 and this is due to the fact that the perioral muscles, including the orbicularis oris and mentalis muscles 17,21 , will act more actively in order to restore the lip sealing required to adequate breathing 34,35 , which arouses the interest of researchers to evaluate both subjectively and quantitatively with electromyographic results, correlating with swallowing 14 , chewing 15,18 and speech 24 functions.…”