Li Zixin, Yu Min, Jin Shanshan, Wang Yu, Luo Rui, Huo Bo, Liu Dawei, He Danqing, Zhou Yanheng, Liu Yan
Laboratory of Biomimetic Nanomaterials, Department of Orthodontics, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, Beijing, China.
Biomechanics Lab, Department of Mechanics, School of Aerospace Engineering, Beijing Institute of Technology, Beijing, China.
Front Pharmacol. 2019 Oct 24;10:1263. doi: 10.3389/fphar.2019.01263. eCollection 2019.
Periodontal ligament (PDL), as a mechanical connection between the alveolar bone and tooth, plays a pivotal role in force-induced orthodontic tooth movement (OTM). However, how mechanical force controls remodeling of PDL collagenous extracellular matrix (ECM) is largely unknown. Here, we aimed to evaluate the stress distribution and ECM fiber remodeling of PDL during the process of OTM. An experimental tooth movement model was built by ligating a coil spring between the left maxillary first molar and the central incisors. After activating the coil spring for 7 days, the distance of tooth movement was 0.324 ± 0.021 mm. The 3D finite element modeling showed that the PDL stress obviously concentrated at cervical margin of five roots and apical area of the mesial root, and the compression region was distributed at whole apical root and cervical margin of the medial side (normal stress < -0.05 MPa). After force induction, the ECM fibers were disordered and immature collagen III fibers significantly increased, especially in the apical region, which corresponds to the stress concentration and compression area. Furthermore, the osteoclasts and interleukin-1β expression were dramatically increased in the apical region of the force group. Taken together, orthodontic loading could change the stress distribution of PDL and induce a disordered arrangement and remodeling of ECM fibers. These findings provide orthodontists both mechanical and biological evidences that root resorption is prone to occur in the apical area during the process of OTM.
牙周韧带（PDL）作为牙槽骨与牙齿之间的机械连接，在正畸牙齿移动（OTM）过程中起着关键作用。然而，机械力如何控制PDL胶原细胞外基质（ECM）的重塑在很大程度上尚不清楚。在此，我们旨在评估OTM过程中PDL的应力分布和ECM纤维重塑。通过在上颌左侧第一磨牙和中切牙之间结扎螺旋弹簧建立实验性牙齿移动模型。激活螺旋弹簧7天后，牙齿移动距离为0.324±0.021mm。三维有限元建模显示，PDL应力明显集中在五个牙根的颈部边缘和近中牙根的根尖区域，压缩区域分布在整个根尖牙根和内侧的颈部边缘（正应力＜-0.05MPa）。力诱导后，ECM纤维紊乱，不成熟的III型胶原纤维显著增加，尤其是在根尖区域，这与应力集中和压缩区域相对应。此外，力作用组根尖区域破骨细胞和白细胞介素-1β表达显著增加。综上所述，正畸加载可改变PDL的应力分布，诱导ECM纤维排列紊乱和重塑。这些发现为正畸医生提供了机械和生物学证据，表明在OTM过程中根尖区域容易发生牙根吸收。
