Korean J Orthod.  2008 Aug;38(4):228-239. 10.4041/kjod.2008.38.4.228.

Cortical bone strain during the placement of orthodontic microimplant studied by 3D finite element analysis

• Nam O
• Yu W
• Kyung HM

• KMID: 2273364
• DOI: http://doi.org/10.4041/kjod.2008.38.4.228

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.

Keyword

Microimplant; Strain during insertion; 3D finite element method; Rabbit experiment

MeSH Terms

Animal Experimentation
Bone Remodeling
Finite Element Analysis
Sprains and Strains
Tibia
Torque

Figure

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  Fig 1. Geometry of microimplant and cortical bone specimen together with axis system and important dimensions (implant: rigid, cortical bone: rigid-plastic, unit: mm). A, Geometry model; B, initial mesh of the cortical bone constructed of 30,706 tetrahedral element.

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  Fig 2. Material property of cortical bone used in the present study (cf. Table 1).

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  Fig 3. A-L, Effective strain distribution in the cortical bone at 12 separate stages of microimplant insertion.

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  Fig 4. A-J, Strain distribution in the cortical bone at 9 separate stages of microimplant insertion with strains cut off at 4000μ-strain.

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  Fig 5. Estimated insertion torque during microimplant placement of FEM model.

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  Fig 6. Insertion torque measured during microimplant placement into a rabbit tibia of 1.0 - 1.5 mm thickness. A, Upper part of tibia; B, lower part of tibia.

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