title: Immediate versus delayed loading: comparison of primary stability loss after miniscrew placement in orthodontic patients-a single-centre blinded randomized clinical trial.
abstract: The aim of this randomized clinical trial was to compare torque recordings at insertion time and 1 week post-placement between immediately loaded orthodontic miniscrews and an unloaded control group.
  
  
  
  This RCT was designed as parallel with an allocation ratio of 1:1.
  
  
  
  Eligibility criteria to enroll patients were: needs of fixed orthodontic treatment, no systemic disease, absence of using drugs altering bone metabolism. All patients were consecutively treated in a private practice and the miniscrews were placed by the same author. Patients received ORTHOImplant (3M Unitek) miniscrews and they were blindly divided in two groups: group 1 screws were unloaded between T0 and T1, group 2 received immediately loaded screws with NiTi coil. For each patient, maximum insertion torque (MIT) was evaluated at T0. After 1 week, without loading, the screw torque was measured again (T1) and at the end of the treatment maximal removal torque was evaluated (T2). Torque variation in the first week was considered as the primary outcome.
  
  
  
  A randomization list was created for the group assignment, with an allocation ratio of 1:1.
  
  
  
  The study was single blinded in regard of the statistical analysis.
  
  
  
  Patients enrolled in the clinical trial were 51 for a total of 81 miniscrews. The recruitment started in November 2012 and the observation period ended in August 2014. Twenty-six and twenty-five patients were analysed in group 1 and 2, respectively. The MIT mean in each placement time was 18.25 Ncm (SD = 3.00), 11.41 Ncm (SD = 3.51) and 10.52 Ncm (SD = 5.14) at T0, T1, and T2 time, respectively. In group 1, the torque decrease between T1 and T0 was statistically higher compared to group 2 (P value = 0.003). Statistically significant effects of the placement times on MIT were found (P value <0.0001). No serious harm was observed.
  
  
  
  This study was performed using only direct force on the miniscrew and not using the miniscrew as an indirect anchorage. It was not possible to obtain quantitative data on bone quality or root proximity to miniscrews.
  
  
  
  A significant stability loss was observed in the first week in both groups; Group 1 showed a statistically higher torque loss in the first week when compared to the immediately loaded group. There were statistically significant effects of the measurement times on MIT and of the miniscrew location on MIT. The overall failure rate was 7.4%.
  
  
  
  This trial was not registered.
  
  
  
  The protocol was not published before trial commencement.
authors.affiliation: *Orthodontics Department, School of Dentistry, University of Genova, Italy, marco.migliorati@unige.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Migliorati
authors.affiliation: *Orthodontics Department, School of Dentistry, University of Genova, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Drago
authors.affiliation: **Section of Biostatistics, Department of Health Sciences, University of Genova, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Gallo
authors.affiliation: ***Private Practice, Gallarate, Italy.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Amorfini
authors.affiliation: ****Department of Orthodontics, School of Dentistry, University of Brescia, Italy, and.
authors.forename: Domenico
authors.initials: D
authors.lastname: Dalessandri
authors.affiliation: *Orthodontics Department, School of Dentistry, University of Genova, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Calzolari
authors.affiliation: *****School of Dentistry, University of Genova, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Benedicenti
authors.affiliation: *Orthodontics Department, School of Dentistry, University of Genova, Italy.
authors.forename: Armando
authors.initials: A
authors.lastname: Silvestrini-Biavati
mesh_terms: D000328:Adult; D001863:Bone Screws; D003799:Dental Stress Analysis / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D009532:Nickel; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation* / Q000379:methods; D016037:Single-Blind Method; D013997:Time Factors; D014025:Titanium; D019415:Torque; D016474:Weight-Bearing
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium