title: Torque Loss After Miniscrew Placement: An In-Vitro Study Followed by a Clinical Trial.
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.
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Genova, Viale Benedetto XV 6, 16132 Genova, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Migliorati
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Genova, Viale Benedetto XV 6, 16132 Genova, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Drago
authors.affiliation: Department of Civil, Chemical and Environmental Engineering (DICCA), University of Genova, Via Montallegro 1, 16145 Genova, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Barberis
authors.affiliation: Department of Health Sciences (DISSAL), University of Genova, Via Pastore 1, 16132 Genova, Italy.
authors.forename: Irene
authors.initials: I
authors.lastname: Schiavetti
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Brescia, Piazzale Spedali Civili 1, 25123 Brescia, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Dalessandri
authors.affiliation: Department of Surgical and Diagnostic Integrated Sciences, University of Genova, Largo Benzi 8, 16132 Genova, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Benedicenti
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Genova, Viale Benedetto XV 6, 16132 Genova, Italy.
authors.forename: Armando Silvestrini
authors.initials: AS
authors.lastname: Biavati
keywords: Anchorage; Bone implant contact; Bone relaxation; Implant design; Orthodontic mini-implant; Orthodontic miniscrews