Effect of Different Head Hole Position on the Rotational Resistance and Stability of Orthodontic Miniscrews: A Three-Dimensional Finite Element Study.

Jin-Young Choi,Seong-Hun Kim,Kyu-Rhim Chung,Min-Jung Kim,Gerald Nelson

doi:10.3390/s21113798

Abstract

The orthodontic miniscrew is driven into bone in a clockwise direction. Counter-clockwise rotational force applied to the implanted miniscrew can degrade the stability. The purpose of this three-dimensional finite element study was to figure out the effect of shifting the miniscrew head hole position from the long axis. Two miniscrew models were developed, one with the head hole at the long axis and the other with an eccentric hole position. One degree of counter-clockwise rotation was applied to both groups, and the maximum Von-Mises stress and moment was measured under various wire insertion angles from −60° to +60°. All Von-Mises stress and moments increased with an increase in rotational angle or wire insertion angle. The increasing slope of moment in the eccentric hole group was significantly higher than that in the centric hole group. Although the maximum Von-Mises stress was higher in the eccentric hole group, the distribution of stress was not very different from the centric hole group. As the positive wire insertion angles generated a higher moment under a counter-clockwise rotational force, it is recommended to place the head hole considering the implanting direction of the miniscrew. Clinically, multidirectional and higher forces can be applied to the miniscrew with an eccentric head hole position.

Highlights

Almost all the values of Von-Mises stress were the lowest at 0◦ of wire insertion angle, and they increased as the insertion angle became steep (Tables 2 and 3)
A finite element model was established to analyze the stress distribution of two head hole positions and the maximum Von-Mises stresses and moments of the orthodontic wire inserted into the head hole with different implantation angles
As either wire insertion angles or counter-clockwise rotational angle of the miniscrew increased, the moment increased with the statistical significance

Summary

Introduction

The temporary skeletal anchorage devices (TSADs) are an established powerful tool for efficient tooth movement. Reports indicate more effective correction of severe malocclusions and dentofacial discrepancies [1,2,3,4], such as en-masse retraction of anterior teeth [2,5], molar uprighting [6], maxillary expansion [7,8,9,10], skeletal open bite or deep bite correction [11,12], and anteroposterior discrepancy correction [13,14]. The successful use of TSADs in the clinic is highly related to their stability [15,16,17]. Several studies consider miniscrew design according to the requirements of clinical stability [18,19,20,21,22,23,24]

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Methods

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Discussion

Conclusion