title: [The relationship between the stability of microimplants and factors of gender and age].
abstract: OBJECTIVE
  To summarize the clinical failure rate of 286 self-drilling microimplant anchorages and to investigate the relationship between the stability of microimplant anchorages and the patient's gender and age.
  
  
  METHODS
  The failure rate of 286 self-drilling microimplants placed in the maxillary posterior region for anterior teeth retraction was analyzed. All 143 cases were sorted into male group and female group by gender, as well as children group and adult group by age. The difference of failure rates was compared between male group and female group, as was done between children group and adult group. Besides, the incidence of failure in both sides of one patient was also compared between children group and adult group. The data were analyzed by Chi-square or U test with SPSS15.0 software package.
  
  
  RESULTS
  Totally 50 microimplants failed and the average failure rate of 286 microimplants was 17.5%. The failure rates were 23.1% and 20.7% in children male group and children female group, and 10.0% and 12.1% in adult male group and adult female group. No significant difference was found between different gender groups. The total failure rate in children group was 21.8%, and 11.2% in adult group. The difference was significant (P<0.05, Chi-square test, two-tailed test). The incidence of failure in both sides in children group was 8.2%, while 1.7% in adult group. The difference was also significant (P<0.05, U test, one tailed test).
  
  
  CONCLUSIONS
  In this study, the average failure rate of 286 self-drilling microimplants is 17.5%. There is no significant relationship between the stability of microimplants and gender. It seems more possible for microimplants placed in children to fail than those in adults.
authors.affiliation: Department of Orthodontics, Ninth People's Hospital, College of Stomatology, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Guo-ping
authors.initials: GP
authors.lastname: Ji
authors.forename: Quan
authors.initials: Q
authors.lastname: Yu
authors.forename: Gang
authors.initials: G
authors.lastname: Shen
mesh_terms: D000328:Adult; D015921:Dental Implants; D005260:Female; D006801:Humans; D008297:Male; D008437:Maxilla; D052280:Orthodontic Anchorage Procedures; D016382:Orthodontic Appliance Design
chemical_list: D015921:Dental Implants