title: Effect of mini-implant diameter on fracture risk and self-drilling efficacy.
abstract: BACKGROUND
  The aim of this study was to evaluate the effect of mini-implant diameter on fracture risk and self-drilling efficacy.
  
  
  METHODS
  A sample of 405 mini-implants with 9 diameters from 1.2 to 2.0 mm was used. Ten mini-implants of each diameter were placed in artificial bone, and 25 were placed in pig iliac bone to evaluate placement torque (PT) and axial placement load (APL), which represents self-drilling efficacy. Ten mini-implants of each diameter were used to determine fracture torque (FT). The different diameters were compared regarding PT, FT, and APL. The fracture risk of each diameter was evaluated by the fracture resistance index (FT/PT × [FT-PT]). The PT and APL changes during placement were correlated.
  
  
  RESULTS
  Only PT and FT were different for all mini-implant diameter changes. PT and FT showed a strong correlation with the mini-implant diameter, but the APL was weakly to moderately correlated. The fracture resistance index was remarkably greater for each 0.1 mm added in diameter. The PT increased significantly, whereas the APL was progressively reduced during placement.
  
  
  CONCLUSIONS
  Increases in mini-implant diameters significantly influenced the increases of PT and FT on quantities that progressively reduced the fracture risk. The self-drilling efficacy was not strongly influenced by diameter.
authors.affiliation: Department of Orthodontics, Bauru Dental School, University of São Paulo, Bauru, Brazil. sergioestelita@yahoo.com.br
authors.forename: Sérgio Estelita
authors.initials: SE
authors.lastname: Barros
authors.forename: Guilherme
authors.initials: G
authors.lastname: Janson
authors.forename: Kelly
authors.initials: K
authors.lastname: Chiqueto
authors.forename: Daniela Gamba
authors.initials: DG
authors.lastname: Garib
authors.forename: Marcos
authors.initials: M
authors.lastname: Janson
mesh_terms: D000497:Alloys; D000818:Animals; D001696:Biomechanical Phenomena; D018786:Bone Substitutes / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D015921:Dental Implants; D004868:Equipment Failure; D007085:Ilium / Q000601:surgery; D008422:Materials Testing; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D010027:Osteotomy / Q000379:methods*; D011140:Polyurethanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013552:Swine; D014025:Titanium / Q000737:chemistry; D019415:Torque; D054159:Torsion, Mechanical
chemical_list: D000497:Alloys; D018786:Bone Substitutes; D003722:Dental Alloys; D015921:Dental Implants; D011140:Polyurethanes; C031462:titanium alloy (TiAl6V4); D014025:Titanium