Graduate Orthodontic Program, University of Michigan, Ann Arbor 48109-1078, USA.
Am J Orthod Dentofacial Orthop. 2010 Nov;138(5):582-91. doi: 10.1016/j.ajodo.2008.12.026.
The objective of this prospective clinical study was to evaluate the dentoalveolar and skeletal effects induced by rapid maxillary expansion (RME) therapy in mixed dentition patients with Class II Division 1 malocclusion compared with a matched untreated Class II Division 1 control group.
The treatment sample consisted of cephalometric records of 50 patients with Class II malocclusion (19 boys, 31 girls) treated with an RME protocol including an acrylic splint expander. Some patients also had a removable mandibular Schwarz appliance or maxillary incisor bracketing as part of their treatment protocol. Postexpansion, the patients were stabilized with a removable maintenance plate or a transpalatal arch. The mean age at the start of treatment of the RME group was 8.8 years (T1), with a prephase 2 treatment cephalogram (T2) taken 4.0 years later. The control sample, derived from the records of 3 longitudinal growth studies, consisted of the cephalometric records of 50 Class II subjects (28 boys, 22 girls). The mean age of initial observation for the control group was 8.9 years, and the mean interval of observation was 4.1 years. All subjects in both groups were prepubertal at T1 and showed comparable prevalence rates for prepubertal or postpubertal stages at T2. Independent-sample Student t tests were used to examine between-group differences.
Class II patients treated with the described bonded RME protocol showed statistically significant increases in mandibular length and advancement of pogonion relative to nasion perpendicular. The acrylic splint RME had significant effects on the anteroposterior relationship of the maxilla and the mandible, as shown by the improvements toward Class I in the maxillomandibular differential value, the Wits appraisal value, and the ANB angle. Patients treated with the bonded RME showed the greatest effects of therapy at the occlusal level, specifically highly significant improvement of Class II molar relationship and decrease in overjet. Treatment with the acrylic splint RME had no sustainable effects on the skeletal vertical dimension, maxillary skeletal position, or maxillary dentoalveolar dimensions.
This study suggests that the protocol described including treatment with a bonded rapid maxillary expander used in the early mixed dentition in Class II Division 1 patients can help to improve the Class II malocclusion as a side-effect, both skeletally and dentally. Evidence for this phenomenon was based previously on anecdotal data; the results of this study show that the improvements are far more pervasive than anticipated.
本前瞻性临床研究的目的是评估快速上颌扩张（RME）治疗在混合牙列 II 类 1 错牙合患者中的牙牙槽和骨骼效果，并与未经治疗的 II 类 1 错牙合对照组相匹配。
治疗组由 50 名 II 类错牙合患者（19 名男孩，31 名女孩）的头颅侧位片组成，这些患者接受了 RME 方案治疗，包括丙烯酸夹板扩弓器。一些患者还使用了可摘式下颌 Schwarz 矫治器或上颌切牙矫正器作为其治疗方案的一部分。扩弓后，患者使用可摘式保持器或腭弓进行稳定。RME 组患者的治疗起始年龄平均为 8.8 岁（T1），4 年后（T2）拍摄了二期治疗前的头颅侧位片。对照组来源于 3 项纵向生长研究的记录，由 50 名 II 类受试者（28 名男孩，22 名女孩）的头颅侧位片组成。对照组的初始观察平均年龄为 8.9 岁，观察间隔平均为 4.1 年。两组所有受试者在 T1 时均处于青春前期，在 T2 时具有相似的青春前期或青春后期的患病率。采用独立样本 t 检验比较组间差异。
采用描述的粘结式 RME 方案治疗的 II 类患者下颌长度和颏部相对于前颅底垂直方向的前突明显增加。丙烯酸夹板 RME 对上颌和下颌的前后关系有显著影响，表现为上颌下颌差异值、Wits 评价值和 ANB 角向 I 类的改善。采用粘结式 RME 治疗的患者在咬合水平上的治疗效果最大，特别是 II 类磨牙关系的显著改善和覆牙合的减少。采用丙烯酸夹板 RME 治疗对骨骼垂直尺寸、上颌骨骼位置或上颌牙牙槽尺寸无持续影响。
本研究表明，包括在 II 类 1 错牙合早期混合牙列中使用粘结式快速上颌扩张器的描述性方案治疗可以帮助改善 II 类错牙合，这是一种骨骼和牙齿方面的副作用。这种现象的证据以前基于轶事数据；本研究结果表明，这种改善比预期的更为普遍。
