This book contain the study of radiographical and histological effect of ultra sound waves on the mandibular condyle growth in subjects who are in their maximum growth spurt and to see the posibility of skeletal class II due to mandibular undergrowth treatment by these waves in future also to be as a subsitute for the traditional myofunctional appliances that are used in the tratment of such cases.and that due to the difficulties that facing the orthodontist in using these appliances because of it's large and huge nature in mouth that need large cooperation from the young patient towear them for long duration in day.