磁共振成像扫描仪静磁场中牙保持器上的磁位移力和转矩

Magnetic displacement force and torque on dental keepers in the static magnetic field of an MR scanner.

作者信息

Omatsu Mika, Obata Takayuki, Minowa Kazuyuki, Yokosawa Koichi, Inagaki Eri, Ishizaka Kinya, Shibayama Koichi, Yamamoto Toru

机构信息

Radiological Technology Section, Reseach Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.

出版信息

J Magn Reson Imaging. 2014 Dec;40(6):1481-6. doi: 10.1002/jmri.24500. Epub 2013 Nov 20.

DOI:10.1002/jmri.24500

PMID:24259448

Abstract

PURPOSE

To evaluate the effect of the static magnetic field of magnetic resonance (MR) scanners on keepers (ie, ferromagnetic stainless steel plate adhered to the abutment tooth of dental magnetic attachments).

MATERIALS AND METHODS

Magnetically induced displacement force and torque on keepers were measured using 1.5 Tesla (T) and 3.0 T MR scanners and a method outlined by American Society for Testing and Materials (ASTM). Changes in magnetic flux density before and after exposure to scanner static magnetic field were examined.

RESULTS

The maximum magnetically induced displacement forces were calculated to be 10.3 × 10(-2) N at 1.5 T and 13.9 × 10(-2) N at 3.0 T on the cover surface. The maximum torques exerted on the keeper (4 mm in diameter) were 0.83 N × 4 mm at 1.5 T and 0.85 N × 4 mm at 3.0 T. These forces were considerably higher than the gravitational force (7.7 × 10(-4) N) of the keeper but considerably lower than the keeper-root cap proper adhesive force. The keepers' magnetic flux density remained less than that of the Earth.

CONCLUSION

Magnetically induced displacement force and torque on the keeper in the MR scanner do not influence the keeper-root cap proper adhesive force.

摘要

目的

评估磁共振（MR）扫描仪的静磁场对固位体（即附着于口腔磁性附着体基牙上的铁磁性不锈钢板）的影响。

材料与方法

使用1.5特斯拉（T）和3.0 T的MR扫描仪以及美国材料与试验协会（ASTM）概述的方法，测量固位体上的磁感应位移力和扭矩。检测暴露于扫描仪静磁场前后磁通密度的变化。

结果

在覆盖表面，1.5 T时计算出的最大磁感应位移力为10.3×10⁻² N，3.0 T时为13.9×10⁻² N。施加在固位体（直径4 mm）上的最大扭矩，1.5 T时为0.83 N×4 mm，3.0 T时为0.85 N×4 mm。这些力远高于固位体的重力（7.7×10⁻⁴ N），但远低于固位体与牙根帽之间的固有粘合力。固位体的磁通密度仍低于地球的磁通密度。