title: A study on variances in multivariate analyses of oral implant outcome.
abstract: BACKGROUND
  Elaborate studies have shown that interdependency exists between implants being placed in the same patient/jaw. Therefore, interdependency ought to be an important aspect to address, whenever performing statistical analyses of oral implant outcomes. A Jackknife method could be an option when conducting statistical evaluations of oral implant failure prognoses.
  
  
  OBJECTIVE
  The aim of this study was to evaluate whether a statistical difference can be detected by using the Jackknife method in conjunction with life table analyses and/or a log rank test of four different combinations of jaw density and quantity.
  
  
  METHODS
  Four multicenter studies were pooled and adjusted in order to create a research database consisting of 486 patients and 1,737 implants in preparation for the Jackknife resampling method. Combinations of jaw shapes and bone qualities were constructed to select at-risk patients.
  
  
  METHODS
  Life tables with confidence intervals were calculated and a log rank test was used to determine whether a statistical difference between the combinations could be established.
  
  
  RESULTS
  Both statistical analyses, after the Jackknife resampling method, showed that patients with poor bone quality and resorbed jaws (combination IV) had a statistically higher risk of implant failure.
  
  
  CONCLUSIONS
  By rearranging data using the Jackknife method, standardized statistical tests seem to work well even when the study population tested was affected by interdependency.
authors.affiliation: Department of Oral and Maxillofacial Surgery, The Sahlgrenska Academy, Göteborg University, Göteborg, Sweden. irene.herrmann@lifecore.com
authors.forename: Irene
authors.initials: I
authors.lastname: Herrmann
authors.forename: Christina
authors.initials: C
authors.lastname: Kultje
authors.forename: Sture
authors.initials: S
authors.lastname: Holm
authors.forename: Ulf
authors.initials: U
authors.lastname: Lekholm
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D001862:Bone Resorption / Q000473:pathology; D016001:Confidence Intervals; D019992:Databases as Topic; D015921:Dental Implants / Q000706:statistics & numerical data*; D018865:Dental Research / Q000706:statistics & numerical data*; D019232:Dental Restoration Failure; D005260:Female; D006801:Humans; D007571:Jaw Diseases / Q000473:pathology; D015993:Life Tables; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015337:Multicenter Studies as Topic / Q000706:statistics & numerical data; D012307:Risk Factors; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants