【Chris Chang Ortho】436. Nonsurgical Mechanism to Correct Class III w/ open bite and crossbite

Abstract

The treatment of a full-cusp Class III malocclusion, combined with anterior open bite and posterior cross bite, is very challenging and orthognathic surgery is usually indicated. However, patients often reject surgical correction due to costs, and associated risks and pain. In this case, a 27-year-old male with the said diagnosis came for non-surgical correction to his malocclusion. The Discrepancy Index score of this case was 110. After 33 months of treatment, ideal alignment and a Class I canine and molar relationship were achieved without surgery or TAD application. There were three keys in this treatment. First, correct the open bite by extracting all 1st premolars and closing extraction spaces. Second, fix the posterior cross bite by expanding the upper arch and applying cross elastics. Third, compensate the torque loss due to Class III mechanics through proper torque selections, using standard torque brackets on the upper and super-high torque brackets on the lower anteriors. Also, use 0.016x0.025- inch 34 mm Pre-Torque CuNiTi archwires and apply 3rd order bends on the mandibular 0.016x 0.025- inch stainless steel archwires to increase torque. Additionally, install single torquing springs to correct torque on an individual teeth. With these mechanism non-surgical correction of a complex Class III malocclusion can be achieved effectively.
摘要

Full-cusp第三類咬合不正合併前牙開咬和後牙錯咬非常難以治療，通常需要透過手術矯正。然而患者常因為手術相關費用，疼痛以及風險，所以拒絕此治療方式。此一27歲男性患者即屬於這類案例，因此前來尋求以非手術的方式治療他的咬合不正問題。此案例的術前DI評分為110分。經過了三十三個月的治療，達成了理想的第一類咬合關係，治療過程中也未使用手術以及迷你骨釘。此類案例治療有三個重點，第一：拔掉第一小臼齒，透過關閉空間以解決開咬問題；第二：透過擴張主線，擴大上顎合併佩戴錯咬橡皮筋，以改正後牙錯咬；第三：為補償Class III的力學機制所喪失的扭矩，上顎選擇標準扭矩，下顎選擇高扭矩矯正器；為了矯正前牙錯咬和關閉拔牙空間所需的額外扭矩，可使用0.016x0.025 Pre-torque 34 mm 20° CuNiTi 的主線，以及在0.016x0.025 stainless steel線上進行第三級彎折（ 3rd order bends），提供額外扭矩；3. 使用單顆torquing-spring來微調單顆牙齒的扭矩。藉由上述的力學機制，複雜第三類咬合不正病例也可以透過非手術，簡單而有效的方式治療。

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