title: Effects of washer on the stress distribution of mini-implant.
abstract: OBJECTIVE
  To investigate the biomechanical effects of 'washer' designed for improving mini-implant stability.
  
  
  METHODS
  Four three-dimensional finite element models of the mini-implant and surrounding bone were constructed with washers in different spike lengths (1.5 mm, 2.0 mm, and 2.5 mm). The force was applied in two directions (45° and 90°). The stress distribution on surrounding bone and the displacement of the mini-implant were analyzed. Plots of tensile stress, compression stress, and displacement were calculated, and maximum values in each category were analyzed.
  
  
  RESULTS
  The stress distribution was different between the models with washer and without washer. However, no remarkable differences in stress distribution were observed among the models with washer, regardless of spike length. A significantly greater displacement value was observed in the model without washer compared to the models with washer, but no notable difference in displacement value was found among the models with washer. The plots of the displacement distribution of the models with washer presented notable pattern differences as compared with that of the model without washer.
  
  
  CONCLUSIONS
  With the use of the washer, a more homogeneous distribution of bone stress and less displacement of the mini-implant can be achieved.
authors.affiliation: Graduate School of Dentistry, Kyung Hee University, Seoul, South Korea.
authors.forename: Hyoung-Jun
authors.initials: HJ
authors.lastname: Jang
authors.forename: Soon-Yong
authors.initials: SY
authors.lastname: Kwon
authors.forename: Seong-Hun
authors.initials: SH
authors.lastname: Kim
authors.forename: Young-Guk
authors.initials: YG
authors.lastname: Park
authors.forename: Su-Jung
authors.initials: SJ
authors.lastname: Kim
mesh_terms: D001696:Biomechanical Phenomena; D003799:Dental Stress Analysis; D020342:Finite Element Analysis; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000295:instrumentation*