title: Influence of cortical thickness on the stability of mini-implants with microthreads.
abstract: The objective of this study was to assess the influence of cortical thickness and bone density on the insertion torque of a mini-implant (MI) with microthreads. Mini-implants with lengths of 6 and 8 mm in the active part were inserted into synthetic bone blocks (polyurethane resin). The density of these blocks was 20 pounds per cubic foot (pcf), simulating bone marrow, and that of blocks 1, 2, and 3-mm-thick blocks was 40 pcf, simulating cortical bone. Blocks with uniform density of 40 pcf were also used to simulate bone areas of greater density. Insertion torque was quantified with a universal testing machine (EMIC). For both MIs, increasing insertion torque was associated with increasing cortical bone thickness. For the same MI length, significant differences were observed among all assessed groups. The insertion torque of the 6-mm-long MI inserted in a 3-mm-thick cortical bone was equivalent to that of the 8-mm-long MI inserted in a 1-mm-thick cortical bone. MIs inserted in bone blocks of greater density presented insertion torque values almost twice as high as those in other groups. The shorter MI, the lower the insertion torque, and the greater the cortical bone thickness, the greater the insertion torque. To minimize fracture risk, the size of MI should be selected according to the insertion site.
authors: Department of Orthodontics, School of Dentistry, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors: Giselle Naback Lemes
authors: GN
authors: Vilani
authors: Department of Orthodontics, School of Dentistry, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors: Antônio Carlos de Oliveira
authors: AC
authors: Ruellas
authors: Department of Orthodontics, School of Dentistry, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors: Cláudia Trindade
authors: CT
authors: Mattos
authors: Department of Materials Science, School of Engineering, Instituto Militar de Engenharia, Rio de Janeiro, RJ, Brazil.
authors: Daniel Jogaib
authors: DJ
authors: Fernandes
authors: Department of Materials Science, School of Engineering, Instituto Militar de Engenharia, Rio de Janeiro, RJ, Brazil.
authors: Carlos Nelson
authors: CN
authors: Elias
mesh_terms: D000704:Analysis of Variance; D015519:Bone Density; D001842:Bone and Bones / Q000033:anatomy & histology; D015921:Dental Implants; D003799:Dental Stress Analysis; D019544:Equipment Failure Analysis; D006801:Humans; D008422:Materials Testing; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation / Q000379:methods*; D016382:Orthodontic Appliance Design; D012016:Reference Values; D012307:Risk Factors; D018709:Statistics, Nonparametric; D013499:Surface Properties; D019415:Torque
chemical_list: D015921:Dental Implants