Drilling Capability of Orthodontic Miniscrews: In Vitro Study.

Alessandra Marchi,Matteo Camporesi,Sara Izadi,Maurizio Festa,Giampietro Farronato,Luis Salvatierra

doi:10.3390/dj8040138

Alessandra Marchi, Matteo Camporesi + Show 4 more

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https://doi.org/10.3390/dj8040138

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Abstract

The aims of this study were to assess the values and mechanical properties of insertion torque (IT) of steel miniscrews inserted in artificial bone blocks (Sawbones, Pacific Research Laboratories, Vashon, WA, USA) with different bone densities and to detect any scratches on the surface of the miniscrews after insertion. Forty self-drilling miniscrews (Leone S.p.A. ø 1.75 mm, L 8 mm) have been inserted into bone blocks that mimic different stability conditions (density: 20 PCF—pounds per cubic foot, 40 PCF, and 30 + 50 PCF with 2 mm and 4 mm of cortical bone). Before insertion and after removal, all miniscrews were inspected with a stereomicroscope 5x and a SEM to detect potential microscopic cracks. Using an electronic surgical motor (W&H Dentalwerk Bürmoos GmbH, Werner Bader Str. 1, 5111 Bürmoos, Austria), the maximum insertion torque value was registered. Stereomicroscope and SEM examination did not indicate any morphological and surface structural changes to the miniscrews, irrespective of the bone density they were inserted into. The findings showed that IT increased significantly with increasing bone density. In each artificial bone block, morphostructural analysis demonstrated the adequate mechanical properties of the self-drilling miniscrews. IT measurements indicated torque values between 6 and 10 Ncm for blocks with a density of 30 + 50 PCF, whereas the suggested values are between 5 and 10 Ncm.

Highlights

Anchorage, an integral factor for limiting orthodontic movement to only some dental components, is one of the most critical aspects of orthodontic treatment, taking advantage of the stable resistance of other elements [1,2,3].Orthodontic miniscrews are devices designed to be mounted within the bones in order to provide orthodontic device anchorage [4,5,6]
In samples with 20 PCF density, maximum torque values were reached below 1 mm deep and had a linear pattern, without dropping below 2 Ncm +/− 0.8
In samples with 40 PCF density, the torque had an incremental trend throughout the insertion thickness

Summary

Introduction

Orthodontic miniscrews ( referred to as microscrews, micro/mini-implants, orthodontic implants, or TADs—temporary anchoring devices) are devices designed to be mounted within the bones in order to provide orthodontic device anchorage [4,5,6]. Simple-to-use surgical miniscrews (lightweight, self-drilling or self-threading machines) have been developed that are easy to use, highly biocompatible, and resistant to loads and corrosion. The peculiarity of these devices lies in the ability to establish, once implanted, mechanical retention (primary stability) without specifying bone osteointegration, which makes it simpler and less invasive to remove the device at the end of therapy. Insertion torque is associated with primary stability during miniscrew placement [7], but excessive torque can lead to

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