A long-term study of incidence of tongue thrust from ages 4 to 18 found the dysfunction disappearing in some individuals and appearing in others. A small study of the effect of tongue-thrust therapy on stability of overjet correction suggested a beneficial effect. Among 34 subjects, mean age 22:

-- Orthodontic treatment alone did not eliminate tongue thrust (12 of 17 were still tongue thrusting)

-- Of 17 subjects who had received therapy, only 3 were tongue thrusting after treatment

-- Mean relapse in overjet among subjects who had received therapy: 0.56mm Among no therapy subjects: 1.94mm The difference was statistically significant

-- The results suggested that tongue thrust therapy will help in preventing overjet relapse after orthodontic treatment and that patients who have undergone therapy will tend to maintain proper tongue function

Andrianopoulos, M.V., and Hanson, M.L. (1987). Tongue thrust and stability of overjet correction. Angle Orthodontist, 57, 121-135.