title: Influence of research center on overall survival outcomes at each phase of treatment.
abstract: BACKGROUND
  Clinical studies of dental implants tend to fall into two broad categories. Efficacy studies apply strict exclusion criteria under carefully controlled conditions to produce a narrow range of results. Effectiveness studies more closely model real-world treatment environments, with a more diverse patient sample and broader range of provider skills. In this multi-center study of more than 2,900 dental implants, study centers were grouped by implant survival scores in an attempt to draw attention to the influence of confounding variables associated with the treatment environment.
  
  
  METHODS
  Thirty-two study centers were ranked by implant survival scores at uncovering and assigned to three performance groups. Centers whose overall scores were within approximately one standard deviation of the mean were placed in the middle (70%) performance group (MPG). The remaining centers were placed in either the top (15%) performance group (TPG) or the lower (15%) performance group (LPG). Overall survival and survival by phase of treatment were recorded for each of six implant designs in each of the three performance groups.
  
  
  RESULTS
  From implant placement to 36 months, the TPG achieved survival rates from 100% (for 3 designs) to 95.5% (for one design), with an average of 97% for all designs. Increased variations in survival (97.2% to 73%) occurred in the MPG, with larger variations (96.4% to 48%) in the LPG. The HA-coated cylinder recorded consistently high survival scores (over 95%) in all performance groups and all phases of treatment. Failures for other designs in the MPG and LPG were concentrated in the healing period (placement to uncovering), except for the commercially pure titanium screw, which had the most failures between uncovering and prosthesis loading.
  
  
  CONCLUSIONS
  Implant design and treatment environment both play an important role in implant survival. Two design characteristics appear to enhance survival: 1) a surgical protocol involving minimal instrumentation at placement, and 2) hydroxyapatite (HA) coating. The HA-coated press-fit cylinder design was the least affected by the center's performance.
authors.affiliation: Dental Implant Clinical Research Group, VA Medical Center, Ann Arbor, MI, USA.
authors.forename: H F
authors.initials: HF
authors.lastname: Morris
authors.forename: S
authors.initials: S
authors.lastname: Ochi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000497:Alloys; D020099:Coated Materials, Biocompatible; D015986:Confounding Factors, Epidemiologic; D003722:Dental Alloys; D003758:Dental Implantation, Endosseous / Q000295:instrumentation / Q000379:methods; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D017886:Durapatite; D005260:Female; D005500:Follow-Up Studies; D006268:Health Facilities; D006801:Humans; D008297:Male; D008875:Middle Aged; D013499:Surface Properties; D016019:Survival Analysis; D014025:Titanium; D016896:Treatment Outcome; D014945:Wound Healing
chemical_list: D000497:Alloys; D020099:Coated Materials, Biocompatible; D003722:Dental Alloys; D015921:Dental Implants; C031462:titanium alloy (TiAl6V4); D017886:Durapatite; D014025:Titanium