Owman-Moll P, Kurol J, Lundgren D
Department of Orthodontics, Faculty of Odontology, Göteborg University, Sweden.
Eur J Orthod. 1996 Apr;18(2):141-50. doi: 10.1093/ejo/18.2.141.
The aim of this clinical and histological study was to compare the effects of two controlled, continuous forces of 50 cN (approximately 50 g) and 100 cN (approximately 100 g) on tooth movement and root resorptions. The patients, consisting of 32 individuals, 14 boys and 18 girls (mean age 13.1 years), were divided into four groups of eight individuals. The experimental periods were 4 and 7 weeks. In this investigation, designed as an inter-individual study, only the maxillary first premolar on the right side was utilized. The test tooth was buccally moved by means of a fixed orthodontic appliance. A continuous, weekly controlled force of 50 cN was applied to 16 premolars and a force of 100 cN to the remaining 16 test teeth. The force declined on average 22 per cent during the first week when 50 cN was applied and 27 per cent when 100 cN was applied. Tooth movements were studied on dental casts using a coordinate measuring machine. After 4 and 7 weeks, the tooth movements ranged between 0.5 and 3.4 mm (4 weeks) and 2.7 and 7.1 mm (7 weeks) for 50 cN and between 1.0 and 2.9 mm (4 weeks) and 2.2 and 8.3 mm (7 weeks) for 100 cN, with no significant difference when the force magnitude was doubled. Root resorptions were registered in histological sections in all experimental teeth, more frequently after application of 50 cN compared with 100 cN after 7 weeks. However, the severity of root resorption (extension and depth of resorbed root contour and size of root area on histological sections) did not differ significantly when the applied force was doubled to 100 cN. Great individual variations were noted regarding both the magnitude of tooth movement and amount of root resorption.
这项临床与组织学研究的目的是比较50 cN（约50 g）和100 cN（约100 g）这两种可控持续力对牙齿移动和牙根吸收的影响。患者共32人，其中14名男孩、18名女孩（平均年龄13.1岁），被分为四组，每组8人。实验周期为4周和7周。在这项作为个体间研究设计的调查中，仅使用了右侧上颌第一前磨牙。通过固定正畸矫治器使测试牙颊向移动。对16颗前磨牙施加50 cN的每周持续可控力，对其余16颗测试牙施加100 cN的力。施加50 cN时，力在第一周平均下降22%；施加100 cN时，力在第一周平均下降27%。使用坐标测量仪在石膏模型上研究牙齿移动情况。4周和7周后，50 cN组的牙齿移动范围在0.5至3.4 mm（4周）和2.7至7.1 mm（7周）之间，100 cN组的牙齿移动范围在1.0至2.9 mm（4周）和2.2至8.3 mm（7周）之间，力的大小加倍时牙齿移动无显著差异。所有实验牙的组织学切片均记录到牙根吸收情况，7周后，与100 cN相比，50 cN组牙根吸收更频繁。然而，当施加力加倍至100 cN时，牙根吸收的严重程度（组织学切片上吸收牙根轮廓的延伸和深度以及牙根面积大小）无显著差异。在牙齿移动幅度和牙根吸收量方面均观察到较大的个体差异。
