When Should Therapy Begin?    
For the elimination of a tongue thrust, therapy is generally initiated when all upper permanent front teeth (incisors) have erupted.  Children of seven or eight years of age are often mature enough to receive complete training.  However, the age of the patient is not so important as is the maturity level and motivation to succeed.  And of course, adults of any age are capable of success in their treatment program.  The bottom line is the commitment one brings to achieve optimum health.

Therapy can be conducted before, during or after orthodontic treatment.  Correcting and eliminating this underlying Orofacial Myofunctional Disorder can help achieve the orthodontic goal and safeguard against "ortho relapse".  Therefore, following the therapy program will retrain patterns of muscle function and aid in the creation and maintenance of a healthy, stable orofacial environment.  

For elimination of digit sucking habit, a child as young as five should be evaluated as these noxious habits could continue and contribute to the development of OMDs.  Between the ages of four and prior to the eruption of the permanent teeth, much of the damage that occurs to the palatal structure can be reversed.  Therefore, preventative steps go a long way.  

The thumb's pressure can create a narrow and high palatal vault that results in a cross bite occlusion.  Orthodontic treatment can involve a palatal expander to widen the palate back to its natural shape.  If the sucking habit is eliminated before age five then the palate will reshape itself - perhaps eliminating the need for orthodontic intervention. 
The most important factor in treatment is the motivation of the patient of any age to commit to the work.  With a positive attitude and a real commitment, children, teenagers and adults of all ages are capable of success in treatment.  The key is motivation to succeed!