title: Revisiting the stability of mini-implants used for orthodontic anchorage.
abstract: OBJECTIVE
  The aim of this study is to comprehensively analyze the potential factors affecting the failure rates of three types of mini-implants used for orthodontic anchorage.
  
  
  METHODS
  Data were collected on 727 mini-implants (miniplates, predrilled titanium miniscrews, and self-drilling stainless steel miniscrews) in 220 patients. The factors related to mini-implant failure were investigated using a Chi-square test for univariate analysis and a generalized estimating equation model for multivariate analysis.
  
  
  RESULTS
  The failure rate for miniplates was significantly lower than for miniscrews. All types of mini-implants, especially the self-drilling stainless steel miniscrews, showed decreased stability if the previous implantation had failed. The stability of predrilled titanium miniscrews and self-drilling stainless steel miniscrews were comparable at the first implantation. However, the failure rate of stainless steel miniscrews increased at the second implantation. The univariate analysis showed that the following variables had a significant influence on the failure rates of mini-implants: age of patient, type of mini-implant, site of implantation, and characteristics of the soft tissue around the mini-implants. The generalized estimating equation analysis revealed that mini-implants with miniscrews used in patients younger than 35 years, subjected to orthodontic loading after 30 days and implanted on the alveolar bone ridge, have a significantly higher risk of failure.
  
  
  CONCLUSIONS
  This study revealed that once the dental surgeon becomes familiar with the procedure, the stability of orthodontic mini-implants depends on the type of mini-implant, age of the patient, implantation site, and the healing time of the mini-implant. Miniplates are a more feasible anchorage system when miniscrews fail repeatedly.
authors.affiliation: Graduate Institute of Clinical Dentistry and Department of Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Dental Department, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Chung-Chen Jane
authors.initials: CC
authors.lastname: Yao
authors.affiliation: Graduate Institute of Clinical Dentistry and Department of Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Dental Department, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Hao-Hueng
authors.initials: HH
authors.lastname: Chang
authors.affiliation: Graduate Institute of Clinical Dentistry and Department of Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Dental Department, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Jenny Zwei-Chieng
authors.initials: JZ
authors.lastname: Chang
authors.affiliation: Graduate Institute of Clinical Dentistry and Department of Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Dental Department, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Hsiang-Hua
authors.initials: HH
authors.lastname: Lai
authors.affiliation: Graduate Institute of Clinical Dentistry and Department of Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan.
authors.forename: Shao-Chun
authors.initials: SC
authors.lastname: Lu
authors.affiliation: Graduate Institute of Clinical Dentistry and Department of Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Dental Department, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: lcyj@ntu.edu.tw.
authors.forename: Yi-Jane
authors.initials: YJ
authors.lastname: Chen
mesh_terms: D000328:Adult; D000539:Alveolar Process / Q000601:surgery*; D016009:Chi-Square Distribution; D015921:Dental Implants / Q000592:standards*; D003799:Dental Stress Analysis; D004868:Equipment Failure / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D052280:Orthodontic Anchorage Procedures / Q000592:standards*; D012189:Retrospective Studies; D013624:Taiwan
chemical_list: D015921:Dental Implants
keywords: generalized estimating equation; miniplate; miniscrew; orthodontic anchorage