Orthodontic management of a non-syndromic patient with concomitant bimaxillary hypohyperdontia: a case report

ABSTRACT Introduction: Tooth agenesis is one of the most common dental anomalies; however, the concomitant occurrence of opposite dental numerical variation of hypohyperdontia is extremely rare. Objective: To report the successful orthodontic management of a patient with non-syndromic concomitant bilateral agenesis of mandibular canines and two midline inverted supernumerary maxillary teeth. Case report: 21-year-old female patient with a chief complaint of protrusive right maxillary central incisor. The patient was diagnosed with a mild Class II skeletal base, Angle Class III molar relationship and increased overjet associated with hypohyperdontia. Anterior open bite accompanied with tongue-thrusting habit were also observed. Two temporary anchorage devices (TADs) were implanted at the buccal side of the maxillary molar region to control vertical height. Anterior teeth retraction was done after extraction of the maxillary first premolars, to improve the excessive overjet. The treatment mechanics involved lingual brackets system for the maxillary arch and transpalatal arch for anchorage control. Results: The total active treatment period was 35 months. Acceptable occlusion with increased bite force and contact area as well as functional excursion were established without interference, following complex orthodontic treatment with premolar substitution. The resultant occlusion and a satisfactory facial profile were maintained after 29 months of retention. Conclusion: The present case report provides implications regarding the orthodontic treatment of hypohyperdontia-associated substitution for missing teeth as an effective option for improving aesthetic and functional aspects.摘要 引言：牙发育不全（tooth agenesis）是最常见的牙科发育异常之一，但同时伴随少多牙症（hypohyperdontia）——即少牙与多牙共存的反向牙数目变异——的情况极为罕见。 目的：报告1例非综合征性双侧下颌尖牙缺失，伴上颌中线区2颗倒置多生牙的患者，经正畸治疗获得成功的病例。 病例报告：21岁女性患者，主诉为右上颌中切牙前突。患者诊断为轻度Ⅱ类骨骼型基底、安氏Ⅲ类磨牙关系，伴覆盖增大及少多牙症，同时观察到前牙开𬌗及吐舌习惯。在上颌磨牙区颊侧植入2颗临时支抗装置（Temporary Anchorage Devices, TADs）以控制垂直高度。拔除上颌第一前磨牙后进行前牙内收，以改善过度覆盖。治疗方案采用上颌弓舌侧托槽系统，并辅以腭杆进行支抗控制。 结果：总主动治疗时长为35个月。经前磨牙替代的复杂正畸治疗后，建立了咬合关系良好、咬合力及接触面积增加、功能侧方运动无干扰的正常咬合。保持治疗29个月后，咬合关系及满意的面部侧貌得以维持。 结论：本病例报告提示，针对少多牙症伴发牙缺失的正畸替代治疗，是改善美观与功能的有效方案。