Matsumoto Yoshiro, Sringkarnboriboon Siripen, Ono Takashi
Department of Orthodontic Science, Division of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Private Practice, Bangkok, Thailand.
Korean J Orthod. 2018 Sep;48(5):339-345. doi: 10.4041/kjod.2018.48.5.339. Epub 2018 Aug 8.
The purpose of this study was to clarify the effects of continuous force application for extrusive tipping movement and occlusal interference on periapical root resorption in the rat mandibular first molar.
We constructed an appliance comprising a titanium screw implant with a cobalt-chromium post as the anchorage unit and a nickel-titanium closed coil spring (50 cN) as the active unit. Force was applied on the mandibular left first molar of rats for 8 (n = 10) and 15 days (n = 10; experimental groups), with the tooth in occlusion. Five rats were included as a non-treated control group to examine the body effect of the appliance. Active root resorption lacunae, identified using tartrate-resistant acid phosphatase, were evaluated in terms of the length, depth, and area.
The rat mandibular first molars were mesially tipped and extruded in the occlusal direction. This mesio-occlusal tipping movement and occlusion resulted in the formation of a compression zone and active root resorption lacunae in the distoapical third of the distal roots. However, there was no significant difference in the amount of root resorption between the two experimental groups. The control group did not exhibit any active root resorption lacunae.
Periapical root resorption was induced by continuous extrusive tipping force and occlusal interference in rat mandibular molars. These data suggest that we orthodontists had better take care not to induce occlusal interference during our orthodontic treatment.
本研究旨在阐明持续施加外力使下颌第一磨牙进行伸长倾斜移动以及咬合干扰对大鼠根尖牙根吸收的影响。
我们构建了一种矫治器，其包括以钴铬桩为锚固单元的钛螺钉种植体以及以镍钛闭合曲弹簧（50 cN）为施力单元。对大鼠下颌左侧第一磨牙施加力8天（n = 10）和15天（n = 10；实验组），牙齿保持咬合状态。纳入5只大鼠作为未处理的对照组，以研究矫治器对机体的影响。使用抗酒石酸酸性磷酸酶鉴定活跃的牙根吸收陷窝，并对其长度、深度和面积进行评估。
大鼠下颌第一磨牙向近中倾斜并沿咬合方向伸长。这种近中 - 咬合倾斜移动和咬合导致在远中牙根根尖三分之一处形成压缩区和活跃的牙根吸收陷窝。然而，两个实验组之间的牙根吸收量没有显著差异。对照组未出现任何活跃的牙根吸收陷窝。
持续的伸长倾斜力和咬合干扰可诱导大鼠下颌磨牙根尖牙根吸收。这些数据表明，正畸医生在正畸治疗过程中最好注意避免诱导咬合干扰。
