고정식 기능성 교정장치 사용 시의 발치와 고정원

Extraction Decision and Anchorage Consideration for Fixed Functional Appliance Treatment

Fixed functional appliance (FFA) is widely used in recent years because it does not require patient cooperation. The force vector of the FFA tends to push the upper molar posteriorly and the lower incisor forward. These characteristics can affect the extraction site decision and the amount of anchorage required. This case report shows treatment of a patient with severe lip protrusion and large overjet using Forsus, a type of FFA. Upper and lower first premolars were extracted and orthodontic mini-implants (OMIs) were placed to reinforce the anchorage in the lower arch. It seems that the pushing force of Forsus and retraction force of OMIs helped to prevent opening of mandibular plane in this patient with a vertical skeletal pattern. To treat the Class II protrusion patient using FFA, differential anchorage evaluation methods and extraction strategies should be used to obtain the successful occlusal and facial changes.