Functional appliances are ordinarily worn full time in adolescence between 11 and 14 years with a discrepancy between their upper and lower jaws. The reason it is worn between these ages is to avail of the pre pubertal growth spurt, evidence for full time wear is merely empirical.If this appliance only had to be worn part time it would have a significant change in orthodontics in terms of patient acceptance and compliance.The investigators plan on recruiting 84 patients to the study and these subjects will be referred from hospital colleagues. The investigators will randomly allocate the subjects into 2 groups, Group 1 will wear the appliance Full Time(24hours), group 2 will wear the appliance part time(12hours).