Park Jae Hyun, Bayome Mohamed, Zahrowski James J, Kook Yoon-Ah
Postgraduate Orthodontic Program, Arizona School of Dentistry & Oral Health, A. T. Still University, Mesa, Ariz; Graduate School of Dentistry, Kyung Hee University, Seoul, Korea.
Graduate School, Catholic University of Korea, Seoul, Korea; Department of Postgraduate Studies, Universidad Autonoma del Paraguay, Asuncion, Paraguay.
Am J Orthod Dentofacial Orthop. 2017 Jan;151(1):105-117. doi: 10.1016/j.ajodo.2016.06.026.
The purpose of this study was to analyze displacement and stress distribution in the maxilla during maxillary expansion followed by protraction using bone-borne and conventional tooth-borne palatal expanders and a facemask via 3-dimensional finite element analysis.
A finite element model of an adolescent skull was created, and 4 different types of appliances were integrated into it: facemask (type A); facemask with paramedian bone-borne expander (type B), facemask with palatal-slope bone-borne expander (type C), and facemask with conventional expander (type D). Expansion of 0.25 mm followed by 500 g of force per side was applied.
Type A showed anterior displacement of the dentition combined with downward displacement of posterior teeth and upward displacement of anterior teeth. The combination of protraction and expansion in type D showed the greatest anterior displacement. In types B and C, the expansion forces resulted in posterior displacement decreasing the net displacement of the combination. Stresses concentrated around the miniscrews in types B and C. In types A and D, stresses concentrated at the first premolar and first molar. Type B had the highest stresses followed by type C and then D.
The conventional tooth-borne expander (type D) enhanced the effect of maxillary protraction. Facemask alone (type A) resulted in more anterior displacement of the maxilla than the combination of facemask and bone-borne expanders (types B and C). The clinician should be aware of the initial stresses and movements from different expanders with facemask found in this study and confirm the movements in future clinical Class III studies.
本研究的目的是通过三维有限元分析，分析使用骨支抗和传统牙支抗腭扩展器及面罩进行上颌扩展和前牵引时上颌骨的位移和应力分布。
创建了一个青少年颅骨的有限元模型，并将4种不同类型的矫治器整合到其中：面罩（A型）；带正中旁骨支抗扩展器的面罩（B型），带腭斜骨支抗扩展器的面罩（C型），以及带传统扩展器的面罩（D型）。施加0.25毫米的扩展，随后每侧施加500克的力。
A型显示牙列向前移位，后牙向下移位，前牙向上移位。D型的前牵引和扩展相结合显示出最大的向前移位。在B型和C型中，扩展力导致后牙移位，减少了联合移位的净位移。B型和C型中应力集中在微型螺钉周围。在A型和D型中，应力集中在第一前磨牙和第一磨牙处。B型应力最高，其次是C型，然后是D型。
传统牙支抗扩展器（D型）增强了上颌前牵引的效果。单独使用面罩（A型）导致上颌骨比面罩和骨支抗扩展器联合使用（B型和C型）有更多的向前移位。临床医生应了解本研究中发现的不同扩展器与面罩产生的初始应力和移动情况，并在未来的临床III类研究中确认这些移动情况。
