Department of Orthodontic Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Department of Orthodontic Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Am J Orthod Dentofacial Orthop. 2020 Jul;158(1):114-125. doi: 10.1016/j.ajodo.2019.03.033.
Impaction and an abnormal eruption of a second molar occur because of a lack of retromolar space, premature eruption of the mandibular third molar, and ankyloses. The prognosis must be carefully considered when extracting a damaged permanent tooth. In addition to extraction for orthodontics, this enables the establishment of an effective force system to align the impacted tooth. A 21-year-old woman exhibited maxillary anterior crowding, deviation of the maxillary midline, and deeply impacted mandibular second molars bilaterally. The molar relationship was Class II. The cephalometric analysis demonstrated a skeletal Class I relationship (ANB angle, 1.4°); maxillary and mandibular incisors were lingually inclined. Cone-beam computed tomography images indicated that root resorption, caries, and periodontitis were absent in all mandibular molar. Mandibular second premolars were extracted to relieve crowding and achieve Class I molar relationships. The second molars moved mesially on both sides, and there were no signs of ankylosis. We used improved super-elastic nickel-titanium alloy wire (ISW) to upright the mesioangular second molars. We heat-treated the anterior portion of the ISW, including the first molar area, to increase wire stiffness; the posterior portion of the ISW, including the impacted second molar area, remained untreated to ensure that its super-elasticity was preserved. We alleviated crowding, corrected the maxillary midline, and created ideal occlusion with Class I relationship. This case shows that the alignment of a deeply impacted tooth with a heat-treated ISW, combined with voluntary adjustment of wire stiffness, can be a simple and useful treatment option for adult patients.
由于缺乏磨牙后间隙、下颌第三磨牙过早萌出和关节强直，第二磨牙发生嵌塞和异常萌出。在拔除受损恒牙时，必须仔细考虑预后。除了为正畸而拔牙外，这还可以建立有效的力系统来对齐埋伏牙。一位 21 岁的女性表现为上颌前牙拥挤、上颌中线偏斜和双侧下颌第二磨牙严重埋伏。磨牙关系为 II 类。头影测量分析显示骨骼 I 类关系（ANB 角为 1.4°）；上颌和下颌切牙均向舌侧倾斜。锥形束 CT 图像显示所有下颌磨牙均无牙根吸收、龋齿和牙周炎。为了缓解拥挤并实现 I 类磨牙关系，拔除了下颌第二前磨牙。第二磨牙在两侧均向近中移动，没有出现关节强直的迹象。我们使用改良超弹性镍钛合金丝（ISW）来直立近中角度的第二磨牙。我们对 ISW 的前半部分（包括第一磨牙区）进行热处理，以增加丝的硬度；ISW 的后半部分（包括埋伏的第二磨牙区）保持未处理状态，以确保其超弹性得以保留。我们缓解了拥挤，纠正了上颌中线，并通过 I 类关系建立了理想的咬合。本病例表明，使用热处理的 ISW 对齐深埋伏牙，并结合丝硬度的自愿调整，可能是成人患者的一种简单而有用的治疗选择。
