Optimization of orthodontic microimplant thread design

Kwang-Duk Kim; Won-Jae Yu; Hyo-Sang Park; Hee-Moon Kyung; Oh-Won Kwon

doi:10.4041/kjod.2011.41.1.25

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Kim, Yu, Park, Kyung, and Kwon: Optimization of orthodontic microimplant thread design

Original Article

Korean Journal of Orthodontics

Korean Journal of Orthodontics 2011; 41(1): 25-35.

Published online: 28 February 2011

DOI: https://doi.org/10.4041/kjod.2011.41.1.25

Optimization of orthodontic microimplant thread design

Kwang-Duk Kim, DDS, MSD, PhD^a, Won-Jae Yu, DDS, MSD, PhD^b, Hyo-Sang Park, DDS, MSD, PhD^c, Hee-Moon Kyung, DDS, MSD, PhD^c, Oh-Won Kwon, DDS, MSD, PhD^c

^aGraduate Student, Department of Orthodontics, School of Dentistry, Kyungpook National University, Korea.

^bAssociate Professor, Department of Orthodontics, School of Dentistry, Kyungpook National University, Korea.

^cProfessor, Department of Orthodontics, School of Dentistry, Kyungpook National University, Korea.

Corresponding author: Won-Jae Yu. Department of Orthodontics, School of Dentistry, Kyungpook National University, 188-1 Samdeok-dong 2-ga, Jung-gu, Daegu 700-412, Korea. +82 53 420 4991; wonjaeyu@knu.ac.kr

Received 4 January 2010 Revised 5 June 2010 Accepted 9 June 2010

Abstract

Objective

The purpose of this study was to optimize the thread pattern of orthodontic microimplants.

Methods

In search of an optimal thread for orthodontic microimplants, an objective function stability quotient (SQ) was built and solved which will help increase the stability and torsional strength of microimplants while reducing the bone damage during insertion. Selecting the AbsoAnchor SH1312-7 microimplant (Dentos Inc., Daegu, Korea) as a control, and using the thread height (h) and pitch (p) as design parameters, new thread designs with optimal combination of h and p combination were developed. Design soundness of the new threads were examined through insertion strain analyses using 3D finite element simulation, torque test, and clinical test.

Results

Solving the function SQ, four new models with optimized thread designs were developed (h200p6, h225p7, h250p8, and h275p8). Finite element analysis has shown that these new designs may cause less bone damage during insertion. The torsional strength of two models h200p6 and h225p7 were significantly higher than the control. On the other hand, clinical test of models h200p6 and h250p8 had similar success rates when compared to the control.

Conclusions

Overall, the new thread designs exhibited better performance than the control which indicated that the optimization methodology may be a useful tool when designing orthodontic microimplant threads.

Keywords: Orthodontic microimplant, Thread, Design optimization, Insertion strain, Finite element analysis, Torsional strength

Figures and Tables

Fig. 1

Configuration of the Absoanchor SH1312-07 microimplant together with important dimensional data.

Fig. 2

Geometry of microimplant and cortical bone specimen. A, Geometry model (unit: mm); B, shape and dimensional data of cortical bone specimen, constructed of tetrahedral elements; C, sectional view of cortical bone specimen, where p is the thread pitch for each of the 5 microimplants and d is the inner bone diameter made by the microimplant (0.7 mm and 0.9 mm for self drilling and self tapping simulations respectively).

Fig. 3

SQ values varying as a function of two design parameters: thread height (h) and thread pitch (p).

Fig. 4

SEM images of four experimental microimplant models together with important dimensions: A, h200p6; B, h225p7; C, h250p8; D, h275p8 models.

Fig. 5

Radial strain development in the adjacent cortical bone at the final stage of self drilling placement of A, h200p6; B, h225p7; C, h250p8; D, h275p8; E, control models.

Fig. 6

Radial strain development in cortical bone near the tip (0.05 mm ahead of tip) and valley (0.1 mm apart from shank) of each of the 5 microimplant models during the course of self drilling microimplant placement.

Fig. 7

Radial strain development in the adjacent cortical bone at the final stage of self tapping microimplant placement of A, h200p6; B, h225p7; C, h250p8; D, h275p8; E, control models.

Fig. 8

Radial strain development in cortical bone near the tip (0.05 mm ahead of tip) and valley (0.1 mm apart from shank) of each of the 5 microimplant models during the course of self tapping microimplant placement.

Table 1

Mechanical properties (bone and implant materials)

Table 2

Microimplant models and design parameters (unit: mm)

Table 3

Torsional strength test results

SD, Standard deviation.

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