Korean J Orthod.  2011 Dec;41(6):423-430. 10.4041/kjod.2011.41.6.423.

Three-dimensional finite element analysis for determining the stress distribution after loading the bone surface with two-component mini-implants of varying length

• Choi B
• Lee DO
• Mo SS
• Kim SH
• Park KH
• Chung KR
• Nelson G
• Han SH

• KMID: 2273190
• DOI: http://doi.org/10.4041/kjod.2011.41.6.423

Abstract

OBJECTIVE
To evaluate the extent and aspect of stress to the cortical bone after application of a lateral force to a two-component orthodontic mini-implant (OMI, mini-implant) by using three-dimensional finite element analysis (FEA).
METHODS
The 3D-finite element models consisted of the maxilla, maxillary first molars, second premolars, and OMIs. The screw part of the OMI had a diameter of 1.8 mm and length of 8.5 mm and was placed between the roots of the upper second premolar and the first molar. The cortical bone thickness was set to 1 mm. The head part of the OMI was available in 3 sizes: 1 mm, 2 mm, and 3 mm. After a 2 N lateral force was applied to the center of the head part, the stress distribution and magnitude were analyzed using FEA.
RESULTS
When the head part of the OMI was friction fitted (tapped into place) into the inserted screw part, the stress was uniformly distributed over the surface where the head part was inserted. The extent of the minimum principal stress suggested that the length of the head part was proportionate with the amount of stress to the cortical bone; the stress varied between 10.84 and 15.33 MPa.
CONCLUSIONS
These results suggest that the stress level at the cortical bone around the OMI does not have a detrimental influence on physiologic bone remodeling.

Keyword

Osseointegration; Mini-implant; Finite element analysis; Von-Mises stress

MeSH Terms

Bicuspid
Bone Remodeling
Finite Element Analysis
Friction
Head
Maxilla
Molar
Osseointegration

Figure

• 

  Fig. 1 When both intermaxillary elastic and intramaxillary elastic cannot be applied simultaneously, the head part of the C-implant can be easily changed from 1 mm to 2 mm. A, The 1 mm-long head part of the C-implant may not leave additional space for concurrent use of the second elastics; B, the head part of the C-implant can be easily removed; C, a new longer head part (2 mm) can be inserted to the screw part; D, both elastics can now be engaged to the C-implant simultaneously.

• 

  Fig. 2 Geometric design of the two-component mini-implant system.

• 

  Fig. 3 A, Schematic illustrations of the FE models containing the maxilla, maxillary first molar, maxillary second premolar, and mini-implant; B, magnified images of the models containing the mini-implant, first molar, and second premolar; C, the position of the mini-implant placement between the roots and the direction of lateral force loading.

• 

  Fig. 4 Stress distribution generated by friction fitting between the head part and screw part of the mini-implant. Contour plots of signed von Mises stress generated by placement of mini-implants having head lengths of 1 mm (A), 2 mm (B), and 3 mm (C).

• 

  Fig. 5 Contour plots of signed von Mises stress generated by mini-implants having head lengths of 1 mm (A), 2 mm (B), and 3 mm (C) after a 2 N lateral force is applied.

• 

  Fig. 6 A to C, Contour plots of the minimum principal (compressive) stress to the bone after a 2 N lateral force is applied; D to F, contour plots of the maximum principal (tensile) stress to the bone after a 2 N lateral force is applied.

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