Materials and methods of study: The sample of study consisted of (30) patients divided into two groups (G1):group one included (15) patients was treated by Korn mandibular advancer appliance, and (G2): group two included (15) patients was treated by Herbst appliance. In both groups fixed functional appliances were applied concurrently with fixed orthodontic appliance. Lateral cephalograms were taken and analyzed before treatment and after treatment. Statistical analyses were used to analyze data by (Kolmogorov smirnov, K-S) and student's t tests. Statistical significance was set at P<0.05.

Results: For both FFAs, improvement of soft tissue profile was achieved after treatment, straightening of the profile was found in Herbst and Korn appliance patients. Significant reduction of overjet and overbite was noticed in both groups. Retrusion and posterior displacement of upper lip was observed in both groups. Nasolabial angle was decreased significantly in Herbst appliance but in Korn appliance improvement of this angle was noticed which increased insignificantly. Decrease in angle between upper incisor and palatal plane was significant in Herbst appliance more than Korn appliance.

Conclusions: Treatment related dental and facial changes included position of Lips, overjet and overbite could be regarded similar in class II patients treated with Herbst or Korn appliances. Treatment related change that was specific for Herbst appliance could be identified in Significant increase in angle between lower incisor and mandibular plane.