The korean journal of orthodontics (대한치과교정학회지)

The Korean Association Of Orthodontists (대한치과교정학회)
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Cortical bone strain during the placement of orthodontic microimplant studied by 3D finite element analysis

3차원 유한요소법을 이용한 교정용 마이크로임플란트 식립 시의 피질골 스트레인 해석

  • Nam, Ok-Hyun (Department of Orthodontics, School of Dentistry, Kyungpook National University) ;
  • Yu, Won-Jae (Department of Orthodontics, School of Dentistry, Kyungpook National University) ;
  • Kyung, Hee-Moon (Department of Orthodontics, School of Dentistry, Kyungpook National University)
  • 남옥현 (경북대학교 치의학전문대학원 교정학교실) ;
  • 유원재 (경북대학교 치의학전문대학원 교정학교실) ;
  • 경희문 (경북대학교 치의학전문대학원 교정학교실)
  • Published : 2008.08.30
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Abstract

Objective: The aim of this study was to evaluate the strain induced in the cortical bone surrounding an orthodontic microimplant during insertion. Methods: A 3D finite element method was used to model the insertion of a microimplant (AbsoAnchor SH1312-7, Dentos Co., Daegu, Korea) Into 1 mm thick cortical bone with a pre-drilled hole of 0.9 mm in diameter. A total of 1,800 analysis steps was used to simulate the 10 turns and 5 mm advancement of the microimplant. A series of remesh in the cortical bone was allowed to accommodate the change in the geometry accompanied by the implant insertion. Results: Bone strains of well higher than 4,000 microstrain, the reported upper limit for normal bone remodeling, was observed in the bone along the whole length of the microimplant. At the bone in the vicinity of the screw tip, strains of higher than 100% was recorded. The insertion torque was calculated at approximately 1.2 Ncm which was slightly lower than those measured from the animal experiment using rabbit tibias. Conclusions: The insertion process of a microimplant was successfully simulated using the 3D finite element method which showed that bone strains from a microimplant insertion might have a negative impact on physiological remodeling of bone.

식립 후 힘의 부하가 조기에 이루어지는 마이크로임플란트의 경우 식립 시의 골응력 혹은 스트레인의 관리가 그 안정성에 있어 중요한 요인으로 작용할 수 있다. 이에 본 연구에서는 3D 유한요소법을 사용하여 교정용 마이크로임플란트 식립 시 피질골에 발생하는 응력(스트레인)을 해석하였다. 0.9 mm 직경으로 미리 드릴링한 1mm 두께 피질골에 마이크로임플란트(AbsoAnchor SH1312-7, Dentos, Daegu, Korea)가 식립되는 전체 과정(10회전, 식립 깊이 5 mm)의 모사를 위해 총 1,800 step의 유한요소해석을 실시하였다. 식립 진행과 더불어 생기는 나사산 주위 피질골의 기하학적 형상변화를 유한요소해석에 반영하기 위하여 지속적인 remesh를 실행하였으며, 빠른 수렴을 위해 마이크로임플란트는 강체로, 피질골은 강소성체로 모델링하였다. 해석 결과, 마이크로임플란트 식립 시 피질골에 발생되는 스트레인은 임플란트 주위골 전체에서 정상적인 골개형을 위한 한계치로 보고되고 있는 $4,000\;{\mu}$-strain을 상회하였고, 나사산 첨부 인접골에서는 스트레인이 100% 이상에 달하였다. 계산된 피질골 식립토오크는 약 1.2 Ncm 정도로 가토 경골에 동일 모델의 마이크로임플란트을 식립하며 측정한 값에 약간 미달하였으나 근접한 수치를 보였다. 본 연구를 통해, 마이크로임플란트의 식립과정을 3D 유한요소법으로 재현할 수 있음을 확인하였고, 또한 마이크로임플란트 식립에 의해 피질골에 발생하는 스트레인 크기는 생리적인 골개형을 저해할 수 있는 수준임을 확인할 수 있었다.

Keywords

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