Severe Skeletal Class III Correction with Class III Elastics & Bite Turbos｜【Chris Chang Ortho】CC490

Summary
This 25 years old patient came for treatment to correct his prominent chin. Intraoral examination revealed: three missing teeth, anterior and posterior crossbite, Class III molar relationship, and discrepancy between CO and CR position. The profile was good at CR position. A smaller SNA and a larger SNB resulted in severe skeletal Class III. The Discrepancy Index was scored at 42 points, indicating a difficult Class III malocclusion. The patient rejected the treatment plan to open up the edentulous space in the maxilla, substitute the missing teeth with two implants and use two buccal shelf mini screws to retract the mandibular dentition due to costs. An alternative treatment plan was devised to extract the lower first premolars, and use bite turbos and Class III elastics to correct anterior crossbite. Further retraction of the mandibular dentition by two buccal shelf miniscrews was planned if necessary. After 30 months of treatment his profile was significantly improved. The 3 key factors to the successful camouflage Class III treatment are, first, a positive prognosis indicated by Lin’s 3-Ring diagnosis; second, carefully monitored torque control of lower incisors to ensure bodily tooth movement; third, closing large space with simultaneous lingual and buccal forces to prevent binding of the archwire due to a molar mesial-in rotation.
摘要
此25歲患者想要改善突出的下巴。口內檢查發現三顆缺牙，前後牙齒錯咬，大臼齒是第三類咬合關係。他CO，CR的位置不同。當咬合位在CR時，側面輪廓比較好。SNA 角度稍小， SNB 角度稍大，顯示為嚴重的骨性第三類咬合。術前評量DI 值為42分，屬於十分困難的案例。由於患者基於費用考量，不願意採用打開上顎缺牙區，以兩支植體取代缺牙，下顎用迷你螺絲把牙齒往後拉的治療計畫。最後選定的替代治療計劃是：先拔除下顎兩顆第一小臼齒，用第三類橡皮筋把下顎牙齒往後拉，上顎牙齒往前推，來改善錯咬，若有需要再用迷你螺絲把下顎牙齒往後拉。經過30個月的治療後，這患者的外觀和咬合都有顯著改善。成功完成保守掩飾式第三類咬合不正治療的三個關鍵在於1. 根據林錦榮老師的三環診斷，預後良好。2. 持續控制好下門齒牙根角度，確保牙齒是整體移動。3)關閉大空間時要同時以頰和舌側橡皮筋內外同時施力，以避免臼齒向近心方向旋轉，卡住主線。