Battagel J M, Ryan A
Department of Orthodontics, St. Bartholomew's, London, England.
Am J Orthod Dentofacial Orthop. 1998 Feb;113(2):133-43. doi: 10.1016/s0889-5406(98)70285-9.
This study describes the spontaneous changes that occurred in the lower arches of 41 children in whom orthodontic treatment was restricted to the upper arch only. In one group, lower second molars were extracted (n = 18), whereas in the other, these teeth remained in situ (n = 23). A two-phase treatment involved distal movement of the buccal segments with an "en masse" appliance and extraoral traction, followed by edgewise mechanics to retract or align the anterior teeth. Only study casts were examined. The occlusal aspects of the lower casts were recorded with the reflex microscope. Models were examined at the start of treatment, at the completion of buccal segment retraction, and when active appliance therapy was complete. The following arch measurements were recorded: intercanine and intermolar width, arch length and perimeter, and the degree of crowding in both the labial segment and the arch as a whole. In the extraction sample, upper buccal segment retraction was associated with increases in all lower arch dimensions and a reduction of crowding. In the nonextraction group, the response was inconsistent. Although arch length and perimeter reduced, intercanine and intermolar dimensions enlarged with minimal alteration in the labial segment crowding. During the second stage of therapy, dimensions generally decreased: arch length, perimeter, and the intercanine width returned to their pretreatment values in the extraction group and were further reduced in the nonextraction sample. However, both arch length and perimeter remained significantly longer in the extraction group. Intermolar width remained stable in both groups, whereas crowding increased. Over the 2-year observation period, arch length, arch perimeter, and crowding exhibited statistically significant differences in behavior between the two groups.
本研究描述了41名儿童下牙弓的自发变化，这些儿童的正畸治疗仅局限于上牙弓。一组拔除了下第二磨牙（n = 18），而另一组这些牙齿保留原位（n = 23）。两阶段治疗包括使用“整体”矫治器和口外牵引使颊侧段远中移动，随后采用方丝弓矫治技术内收或排齐前牙。仅检查研究模型。用反光显微镜记录下模型的咬合面情况。在治疗开始时、颊侧段远中移动完成时以及主动矫治器治疗结束时检查模型。记录了以下牙弓测量值：尖牙间宽度和磨牙间宽度、牙弓长度和周长，以及唇侧段和整个牙弓的拥挤程度。在拔牙组，上颊侧段内收与所有下牙弓尺寸增加及拥挤程度减轻相关。在非拔牙组，反应不一致。虽然牙弓长度和周长减小，但尖牙间和磨牙间尺寸增大，唇侧段拥挤程度改变极小。在治疗的第二阶段，尺寸通常减小：牙弓长度和周长以及尖牙间宽度在拔牙组恢复到治疗前的值，而在非拔牙组进一步减小。然而，拔牙组的牙弓长度和周长仍显著更长。两组磨牙间宽度均保持稳定，而拥挤程度增加。在2年的观察期内，牙弓长度、牙弓周长和拥挤程度在两组间表现出统计学上显著的行为差异。
