RESEARCH ARTICLE


Torque Loss After Miniscrew Placement: An In-Vitro Study Followed by a Clinical Trial



Marco Migliorati1, Sara Drago1, Fabrizio Barberis2, Irene Schiavetti3, Domenico Dalessandri4, *, Stefano Benedicenti5, Armando Silvestrini Biavati1
1 Department of Orthodontics, School of Dentistry, University of Genova, Viale Benedetto XV 6, 16132 Genova, Italy
2 Department of Civil, Chemical and Environmental Engineering (DICCA), University of Genova, Via Montallegro 1, 16145 Genova, Italy
3 Department of Health Sciences (DISSAL), University of Genova, Via Pastore 1, 16132 Genova, Italy
4 Department of Orthodontics, School of Dentistry, University of Brescia, Piazzale Spedali Civili 1, 25123 Brescia, Italy
5 Department of Surgical and Diagnostic Integrated Sciences, University of Genova, Largo Benzi 8, 16132 Genova, Italy


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© Migliorati et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/legalcode), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Department of Orthodontics, School of Dentistry, University of Brescia, 1, p.le Spedali Civili, Brescia, 25123, Italy; Tel: +39 030 3995783; Fax: +39 030 3996097; E-mail: dalessandridomenico@libero.it


Abstract

To evaluate torque loss a week after insertion, both in an in vivo and an in vitro experimental setup were designed. In the in vivo setup a total of 29 miniscrews were placed in 20 patients who underwent orthodontic treatment. Maximum insertion torque (MIT) was evaluated at insertion time (T1). A week later, insertion torque was measured again by applying a quarter turn (T2); no load was applied on the screw during the first week. In the in vitro setup a total of 20 miniscrews were placed in pig rib bone samples. MIT was evaluated at insertion time (T1). Bone samples were kept in saline solution and controlled environment for a week during which the solution was refreshed every day. Afterwards, torque was measured again by applying a quarter turn (T2). The comparison of MIT over time was done calculating the percentage difference of the torque values between pre- and post-treatment and using the parametric two independent samples t-test or the non-parametric Mann–Whitney test. After a week unloaded miniscrews showed a mean loss of rotational torque of 36.3% and 40.9% in in vitro and in in vivo conditions, respectively. No statistical differences were found between the two different setups. Torque loss was observed after the first week in both study models; in vitro experimental setup provided a reliable study model for studying torque variation during the first week after insertion.

Keywords: Anchorage, Anchorage, Bone implant contact, Bone relaxation, Implant design, Orthodontic mini-implant, Orthodontic miniscrews.