Klaus Katharina, Kleinert Tobias, Ruf Sabine
Department of Orthodontics, Justus Liebig University Giessen, Schlangenzahl 14, 35392, Giessen, Germany.
Private Practice, Balingen, Germany.
J Orofac Orthop. 2024 Aug 27. doi: 10.1007/s00056-024-00545-y.
Adverse side effects of fixed retainers in terms of unwanted tooth movements have been described for both the upper and lower jaw, but data about the extent and movement patterns for the maxilla are scarce. The purpose of the present retrospective case-control study was to analyze the amount and direction of unwanted tooth movements despite upper bonded retainers as well as to analyze possible predisposing pretreatment- and treatment-related factors.
Plaster casts of 1026 patients who completed orthodontic treatment and a subsequent retention phase of 2 years were screened for unintentional tooth movements. The study group comprised 57 patients with visually obvious tooth movements in the upper jaw, while 57 randomly selected patients without visible tooth movements served as control group. For all patients, plaster casts after debonding of multibracket appliance (T1) and after supervised retention (T2) were digitized, and superimposed digitally using a stable palatal reference area. Thereafter, translational and rotational movements were measured in all three planes of space. Pretreatment- and treatment-related factors of the study and control groups were compared by χ test, exact Fisher test, Mann-Whitney U test, and the T‑test for independent samples.
The mean translational movements ranged between 0 and 0.6 mm and the average rotational movements between 0 and 1.3°. Large individual movements up to 2.7 mm translation and 15.9° rotation were seen. A movement pattern around the Y‑ and Z‑axis with an opposite rotational peak at the canines ("upper twist effect") was identified. Compared to the control group, patients of the study group showed a significantly smaller intercanine width pretreatment. Also, study group patients presented a larger intercanine expansion and a slightly larger overjet reduction during treatment, and were more often affected by retainer bonding site detachments and wire fractures, but without reaching statistically significance.
Upper bonded retainers show a similar unwanted movement pattern ("twist effect") like the one described for mandibular retainers.
上颌和下颌固定保持器均存在导致不必要牙齿移动的不良副作用，但关于上颌牙齿移动程度和模式的数据较少。本回顾性病例对照研究的目的是分析佩戴上颌粘结保持器后不必要牙齿移动的量和方向，并分析可能的预处理及治疗相关易感因素。
对1026例完成正畸治疗并随后进行2年保持期的患者的石膏模型进行筛查，以确定有无意外的牙齿移动。研究组包括57例上颌牙齿有明显可见移动的患者，而随机选择的57例无可见牙齿移动的患者作为对照组。对所有患者，将多托槽矫治器拆除后（T1）和监督保持后（T2）的石膏模型进行数字化处理，并使用稳定的腭部参考区域进行数字叠加。此后，在空间的所有三个平面上测量平移和旋转运动。通过χ检验、确切概率法、曼-惠特尼U检验和独立样本T检验比较研究组和对照组的预处理及治疗相关因素。
平均平移运动范围在0至0.6毫米之间，平均旋转运动在0至1.3°之间。观察到有个体移动较大者，平移达2.7毫米，旋转达15.9°。确定了一种围绕Y轴和Z轴的移动模式，犬齿处有相反的旋转峰值（“上扭转效应”）。与对照组相比，研究组患者治疗前的尖牙间宽度明显较小。此外，研究组患者在治疗期间尖牙间扩展更大，覆盖减小略大，并且更常受到保持器粘结部位脱离和钢丝断裂的影响，但未达到统计学意义。
上颌粘结保持器表现出与下颌保持器类似的不必要移动模式（“扭转效应”）。
