Abstract: Abstract： Objective　To investigate the optimal treatment timing of CICE appliance for class II malocclusion according to Quantitative Cervical Vertebral Maturation(QCVM). Methods　60 cases of Class II malocclusion (an average age of 12.5 years) with normal maxilla and retruded mandible were selected and the patients were divided into three groups I-II-III according to QCVM. For each group, mandibular protraction was achieved with CICE appliance for 6 months before fixed orthodontic treatment. Cephalometric analysis was compared pre-treatment and post-treatment. Results　After 6 months of CICE appliance therapy, harmany profile and remarkable advancement of the mandible were obtained in all of these cases. Class II occlusions were changed to Class I relationship. During QCVM II, the skeletal parameters were changed more significantly than dental parameters before and post treatment. The order of the parameters variation in different QCVM groups is QCVM II＞QCVM I＞QCVM III. Conclusion　CICE appliance contacts comfortable, invisible, concise, efficient, but the optimal treatment timing of mandibular protraction is also significant.

Key words: Key words： quantitative cervical vertebral maturation, functional appliance, class II malocclusion