Abstract : 
The definition of Skeletal class II is a paraphrase of Angle classification base on cephalometrics. but it is only the diagnosis in sagittal dimension. There are lack of diagnostic criteria in vertical and transversal dimension. From tremendous human evolution and growth studies, we can conclude human skull has more growth in vertical dimension than transversal and sagittal ones. Skeletal discrepancy is result of unbalanced vertical growth, which is termed as rotational growth, including Clockwise rotation（CW）and Counter Clock Wise (CCW) rotation. We use 6 keys to differentiate skeletal discrepancy: 1. Sagittal difference, 2.Mandible plane angle, 3. Posterior occlusal plane, 4. Upper front teeth exposure, 5. Transversal and symmetry. 6. Masticatory muscle force. Successful treatment is based on comprehensive diagnosis. Treatment plan need to be addressed with each diagnosis. We will demonstrate the interaction of diagnosis and treatment by presenting several cases.

Learning objectives : 

• Evolutionary background of skeletal discrepancy
• Learning the basic of growth pattern and mandible rotation
• 6 keys of Skeletal Class II diagnosis
• Vertical control