title: Insertion torque versus mechanical resistance of mini-implants inserted in different cortical thickness.
abstract: OBJECTIVE
  This study aimed to measure insertion torque, tip mechanical resistance to fracture and transmucosal neck of mini-implants (MI) (Conexão Sistemas de PróteseT), as well as to analyze surface morphology.
  
  
  METHODS
  Mechanical tests were carried out to measure the insertion torque of MIs in different cortical thicknesses, and tip mechanical resistance to fracture as well as transmucosal neck of MIs. Surface morphology was assessed by scanning electron microscopy (SEM) before and after the mechanical tests.
  
  
  RESULTS
  Values of mechanical resistance to fracture (22.14 N.cm and 54.95 N.cm) were higher and statistically different (P < 0.05) from values of insertion torque for 1-mm (7.60 N.cm) and 2-mm (13.27 N.cm) cortical thicknesses. Insertion torque was statistically similar (P > 0.05) to torsional fracture in the tip of MI (22.14 N.cm) when 3 mm cortical thickness (16.11 N.cm) and dense bone (23.95 N.cm) were used. Torsional fracture of the transmucosal neck (54.95 N.cm) was higher and statistically different (P < 0.05) from insertion torsional strength in all tested situations. SEM analysis showed that the MIs had the same smooth surface when received from the manufacturer and after the mechanical tests were performed. Additionally, no significant marks resulting from the manufacturing process were observed.
  
  
  CONCLUSIONS
  All mini-implants tested presented adequate surface morphology. The resistance of mini-implants to fracture safely allows placement in 1 and 2-mm cortical thickness. However, in 3-mm cortical thickness and dense bones, pre-drilling with a bur is recommended before insertion.
authors.forename: Renata Faria
authors.initials: RF
authors.lastname: Santos
authors.forename: Antonio Carlos de Oliveira
authors.initials: AC
authors.lastname: Ruellas
authors.forename: Daniel Jogaib
authors.initials: DJ
authors.lastname: Fernandes
authors.forename: Carlos Nelson
authors.initials: CN
authors.lastname: Elias
mesh_terms: D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D001842:Bone and Bones / Q000601:surgery*; D015921:Dental Implants; D004868:Equipment Failure; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008904:Miniaturization; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D013314:Stress, Mechanical; D013499:Surface Properties; D019415:Torque; D054159:Torsion, Mechanical
chemical_list: D015921:Dental Implants
keywords: Orthodontic anchorage procedures; Orthodontics; Torque