title: Delayed versus immediate loading of implants: survival analysis and risk factors for dental implant failure.
abstract: OBJECTIVE
  The purpose of this study was to estimate 1-year survival for delayed versus immediately loaded implants and identify risk factors for implant failure.
  
  
  METHODS
  This was a retrospective cohort study, consisting of a sample of subjects who had greater than or equal to 1 Bicon dental implant (Bicon, Boston, MA) placed over a 13-year period. The primary predictor variable was method of implant loading: delayed (3 to 6 months after placement) or immediately after insertion. Secondary predictor variables were classified as demographic, anatomic, implant/abutment, and reconstructive. The outcome variable was implant failure, defined as removal of the implant, and was recorded as months of survival. Descriptive, Kaplan-Meier, and univariate Cox proportional hazards statistics were computed. Univariate associations with P <or= .15 and biologically relevant variables (eg, age, gender) were included in a marginal multiple Cox regression model. In the multiple model, a P value of <or= .05 was considered statistically significant.
  
  
  RESULTS
  The study sample consisted of 677 subjects who had 2,349 delayed-loaded dental implants and 178 patients who had 477 immediate-loaded implants. The unadjusted 1-year survival estimates for the delayed and immediate loading groups were 95.5% and 90.3%, respectively (P < .01). In the marginal multiple Cox regression model, immediate loading, current tobacco use, maxillary implants, and shorter implants were associated with failure (P <or= .05).
  
  
  CONCLUSIONS
  In this study, implants loaded immediately were 2.7 times (after adjusting) more likely to fail at 1 year compared with delayed-loaded implants.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital, Boston, MA 02114, USA. smsusarla@gmail.com
authors.forename: Srinivas M
authors.initials: SM
authors.lastname: Susarla
authors.forename: Sung-Kiang
authors.initials: SK
authors.lastname: Chuang
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Dodson
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D003758:Dental Implantation, Endosseous / Q000379:methods; D015921:Dental Implants; D019232:Dental Restoration Failure; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure; D012737:Sex Factors; D013997:Time Factors; D014029:Tobacco Use Disorder / Q000150:complications; D016896:Treatment Outcome; D016474:Weight-Bearing
chemical_list: D015921:Dental Implants