Jónsdóttir S H, Giesen E B W, Maltha J C
Department of Orthodontics and Oral Biology, Radboud University Nijmegen Medical Centre, The Netherlands.
Eur J Orthod. 2006 Dec;28(6):547-52. doi: 10.1093/ejo/cjl050. Epub 2006 Nov 13.
The aim of this study was to describe the mechanical behaviour of the periodontal ligament (PDL) in response to loading with different forces for a period of 5 hours. Seven young adult male beagle dogs (age 1.0-1.5 years) were used. After extractions and placement of implants, custom-made appliances on both sides of the mandible were used to measure the displacement of the second premolars. Tooth displacement was measured during 5 hours of force application. Each dog underwent two measurement sessions. One premolar was moved with a force of 100 cN in the first session and with 50 cN in the second. The contralateral premolar was moved with forces of 100 and 300 cN, respectively. Time-displacement curves showed a rapid instantaneous response lasting only a few seconds followed by a slowly decreasing creep displacement. The instantaneous response demonstrated a large individual variability, caused by both a dog and a force effect. Differences in tooth and PDL anatomy and in the orientation of the periodontal fibres are probably important in this respect. The individual variability faded after the first seconds of tooth displacement, when the viscoelastic properties of the periodontal fibres became more pronounced. The force effect was non-linear for the first minute. Higher forces did not lead to proportionally larger displacements. The non-linearity decreased in the second response. The PDL is a complex material that might be considered as a non-linear fibre-reinforced poroviscoelastic material.
本研究的目的是描述牙周韧带（PDL）在不同力加载5小时后的力学行为。使用了7只年轻成年雄性比格犬（年龄1.0 - 1.5岁）。拔牙并植入种植体后，在下颌两侧使用定制装置测量第二前磨牙的位移。在施加力的5小时内测量牙齿位移。每只狗进行两次测量。在第一次测量中，一颗前磨牙用100 cN的力移动，在第二次测量中用50 cN的力移动。对侧前磨牙分别用100和300 cN的力移动。时间 - 位移曲线显示出仅持续几秒的快速瞬时响应，随后是缓慢下降的蠕变位移。瞬时响应表现出较大的个体差异，这是由狗和力的效应共同引起的。在这方面，牙齿和PDL的解剖结构以及牙周纤维的方向差异可能很重要。在牙齿位移的最初几秒后，当牙周纤维的粘弹性特性变得更加明显时，个体差异逐渐消失。在第一分钟内，力的效应是非线性的。较高的力并不会导致成比例的更大位移。在第二次响应中，非线性程度降低。PDL是一种复杂的材料，可被视为非线性纤维增强多孔粘弹性材料。
