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
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
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
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.
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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: email@example.com