Primary Stability of Orthodontic Titanium Miniscrews due to Cortical Bone Density and Re-Insertion.

Gi-Tae Kim,Utkarsh Mangal,Jie Jin,Kwang-Mahn Kim,Kee-Joon Lee,Sung-Hwan Choi,Jae-Sung Kwon

doi:10.3390/ma13194433

Gi-Tae Kim, Utkarsh Mangal + Show 5 more

Open Access

https://doi.org/10.3390/ma13194433

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Abstract

The increasing demand for orthodontic treatment over recent years has led to a growing need for the retrieval and reuse of titanium-based miniscrews to reduce the cost of treatment, especially in patients with early treatment failure due to insufficient primary stability. This in vitro study aimed to evaluate differences in the primary stability between initially inserted and re-inserted miniscrews within different cortical bone densities. Artificial bone was used to simulate cortical bone of different densities, namely 20, 30, 40, and 50 pound per cubic foot (pcf), where primary stability was evaluated based on maximum insertion torque (MIT), maximum removal torque (MRT), horizontal resistance, and micromotion. Scanning electron microscopy was used to evaluate morphological changes in the retrieved miniscrews. The MIT, MRT, horizontal resistance, and micromotion was better in samples with higher cortical bone density, thereby indicating better primary stability (P < 0.05). Furthermore, a significant reduction of MIT, MRT, and horizontal resistance was observed during re-insertion compared with the initial insertion, especially in the higher density cortical bone groups. However, there was no significant change in micromotion. While higher cortical bone density led to better primary stability, it also caused more abrasion to the miniscrews, thereby decreasing the primary stability during re-insertion.

Highlights

Miniscrews are widely used as temporary anchorage devices in orthodontic treatments, thereby effectively preventing unwanted dentoalveolar side effects, as well as addressing poor patient cooperation and providing additional nonsurgical orthodontic treatment options [1]
Failure is mainly attributed to various factors related to weak integration between the miniscrew and bone, which leads to insufficient primary stability [4]
Insufficient primary stability leads to further orthodontic treatment, re-insertion of the miniscrew [6,7]

Summary

Introduction

Miniscrews are widely used as temporary anchorage devices in orthodontic treatments, thereby effectively preventing unwanted dentoalveolar side effects, as well as addressing poor patient cooperation and providing additional nonsurgical orthodontic treatment options [1]. Failure is mainly attributed to various factors related to weak integration between the miniscrew and bone, which leads to insufficient primary stability [4]. Bone quality is the main factor determining primary stability, while the insertion site characteristics, geometric design of miniscrew, operation technique, proximity to the root, periodontal. Insufficient primary stability leads to further orthodontic treatment, re-insertion of the miniscrew [6,7]. Thickness and density, plays the most critical role in primary stability. Some previous studies have reported that cortical bone thickness is the primary factor, as density does not affect primary stability when the thickness is sufficient (1.62 ± 0.57 mm in the maxilla and 2.13 ± 0.66 mm in the mandible), while others maintain that both factors are important [1,5,8]

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