Krey Karl-Friedrich, Walter Frank, Dannhauer Karl-Heinz
Department of Orthodontics, Dental School, University of Leipzig, Germany.
J Orofac Orthop. 2008 May;69(3):177-88. doi: 10.1007/s00056-008-0738-1.
Surgically-assisted rapid maxillary expansion is a frequently employed procedure for expanding the maxilla in adults to treat pronounced transversal discrepancies of the upper jaw. Several studies have shown how the position of the anchorage teeth changes due to SRME. However, there is little detailed information available on the transversal movement of each tooth, its change in inclination and subsequent alterations of the arch length, width and sagittal arch form.
In our study we investigated those changes in 31 patient casts after SRME, following the active phase, and after a 3-month retention period whereby the Hyrax appliance remained blocked in situ. The casts were examined using a 3-dimensional reflex microscope.
After active treatment the second molars moved 28% less than the amount of total expansion. At 9.6 degrees (first bicuspid) and 11.6 degrees (first molar), the anchorage teeth were also more buccally tipped than the second molars (7.4 degrees ). Unlike with conventional maxillary expansion, the measured increase in arch length here corresponded to the amount of anchorage teeth expansion. The sagittal arch decreased significantly during the retention phase in those teeth in front of and behind the anchorage teeth. Three months later we found that only 68% of the original expansion had occurred in the canines and second molars. The inclination of the teeth decreased slightly but significantly. We observed an only temporary increase in the sagittal dimension after appliance activation. There was an average loss of 0.83 mm at the end of the retention phase. Moreover, the anterior dental arch length only experienced a 50% increase in space over the expansion achieved initially.
To minimize relapse rates in cases of severe crowding, we recommend that the canines and second molars be included in the appliance.
外科辅助快速上颌扩弓是成人上颌扩弓常用的治疗方法，用于矫治上颌明显的横向差异。多项研究表明了由于外科辅助快速上颌扩弓（SRME），支抗牙的位置如何发生变化。然而，关于每颗牙齿的横向移动、倾斜度变化以及随后牙弓长度、宽度和矢状弓形态的改变，几乎没有详细信息。
在我们的研究中，我们调查了31例患者在SRME后的模型，在激活期之后以及3个月的保持期后，此时Hyrax矫治器仍原位锁定。使用三维反射显微镜检查模型。
主动治疗后，第二磨牙的移动比总扩弓量少28%。在9.6度（第一双尖牙）和11.6度（第一磨牙）时，支抗牙也比第二磨牙（7.4度）更向颊侧倾斜。与传统上颌扩弓不同，此处测量的牙弓长度增加与支抗牙扩弓量相对应。在保持期，支抗牙前后的牙齿矢状弓明显减小。三个月后，我们发现尖牙和第二磨牙仅发生了原始扩弓量的68%。牙齿倾斜度略有但显著降低。矫治器激活后矢状径仅暂时增加。保持期末平均减少0.83mm。此外，前牙弓长度在最初扩弓后仅增加了50%的间隙。
为使严重拥挤病例的复发率降至最低，我们建议矫治器纳入尖牙和第二磨牙。
