【Chris Chang Ortho】447. 3D lever Arm v.s. Power Chains and VISTA

Abstract

This 18 year old female came for consultation with a chief complaint of impacted upper canines. She had sought treatment and been rejected in three other dental clinics prior to this visit. The diagnosis was Class I malocclusion with bilaterally impacted and transposed upper canines in high position. Her profile was good and her dental arches showed no crowding. The treatment plan is to access the impacted #13 by performing vestibular incision subperiosteal tunnel access(VISTA) and retract with a backward force by a power chain connected to an IZC screw. Meanwhile, considering the crown of tooth 23 was located between the root apex of tooth 21 and 22, a 3D lever arm connected to an IZC screw is designed to give the impacted tooth 23 an outward, backward, and downward force vectors to bring it into the dental arch. In the 15th month, #23 was erupted while #13 showed little progress. The left 3D lever arm was then removed and a 3D lever arm was added to the right side and #13 was subsequently erupted ten months later. In the finishing stage, torquing springs were used to correct the torque of tooth 12, 13, and 23, and gingival-plasty was done with laser to improve both the tooth proportion and gingival outline. The total treatment time was 42 months. The ABO CRE score revealed buccal-lingual inclination problems, a predictable side effect of non-extraction cases with significant arch expansion but with no functional or esthetic concerns. Both the patient and her family were satisfied with the result and the original good profile was preserved. The low left upper buccal frenum stretches the gingival margin of #23, and is advised to be surgically repositioned in the follow up appointment to improve esthetics.
摘要

此案例為一18歲女性，主訴為上顎犬齒阻生，之前求診三家診所表示無法拉回正常位置。其診斷為一級咬合異常，齒列並不擁擠，合併上顎雙側犬齒高位阻生，以及犬齒、側門齒錯位；外觀輪廓良好。治療計劃為植入兩隻IZC迷你骨釘，合併微創的VISTA術式，右側單純拉powe chain給予阻生犬齒向後的拉力，左側則以3D lever arm給予阻生犬齒向後且向外的拉力，待犬齒確定拉到正常的萌出位置，再拔除兩顆滯留乳牙。第15個月時左側犬齒、側門齒錯位已改正，但右側進度相對落後，因此拆除左側3D lever arm的同時，並加裝3D lever arm於右側，給予阻生牙向外的分力，於是右上齒錯位也獲得改正。完工階段，上顎前牙的torque以torquing spring微調，最後以雷射調整上顎牙齦緣輪廓，提升功能與美觀。本案例總治療時間為42個月，外觀輪廓維持良好； CRE在buccal-lingual inclination被扣比較多分，是因為不拔牙的案例大幅牙弓擴張必然的副作用，但不影響功能或美觀。患者與家屬都非常滿意治療結果，原來良好的輪廓也得以保留。左上頰繫帶太低，很靠近左上3牙齦緣，影響美觀，日後追蹤時建議患者以手術修除。

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