title: AICRG, Part I: A 6-year multicentered, multidisciplinary clinical study of a new and innovative implant design.
abstract: OBJECTIVE
  Repetitive microstrains, which occur at the bone-implant interface during function, can lead to implant loss. In an attempt to improve survival by directing the stresses during function away from the dense cortical bone and toward the resilient trabecular bone, the Ankylos implant was developed with a roughened, progressive thread and a smooth cervical collar. The highly polished collar reduces the stresses in areas of the crestal bone. A precisely machined Morse taper prevents rotation of the abutment on the implant and eliminates the microgap present in many 2-stage implant systems. Clinical studies of other implants at different clinical research centers have demonstrated varying degrees of survival.
  
  
  OBJECTIVE
  The purpose of this paper was (1) to assess the overall clinical survival of this new implant design and (2) to compare implant stability (ie, Periotest values [PTVs]) over time with other implants.
  
  
  METHODS
  The investigation represented a comprehensive, multicentered, international clinical study conducted over a period of 6 years. It was conducted under an Investigational Device Exemption (IDE) protocol that was reviewed and accepted in the United States by the Food and Drug Administration (FDA). Over 1500 implants were placed and restored, and follow-up data were gathered for a period of up to 3 to 5 years.
  
  
  RESULTS
  Over 44% of the clinical research centers reported no failures (100% survival). A total of 63% of the centers had none or only 1 failure during the study. One center reported 6 failures in 1 patient, which were not related to the implant design. Overall survival for implants in function for 3 to 5 years was 97.5%. Using failure criteria of earlier studies of other implants, 5-year survival was 98.3%. Higher handpiece speeds were associated with an increase in the number of failures. This new design produced a slightly more resilient trabecular bone-implant complex with a difference of about 1 PTV in all bone densities when compared with other implants.
  
  
  CONCLUSIONS
  The following conclusions can be made: (1) the implant design was effective under all clinical conditions; (2) no significant and unexpected complications or risk factors were evident; (3) survival was found to be excellent; and (4) this implant is well suited for use in the restoration of masticatory function and esthetics in patients with missing natural teeth.
authors.affiliation: Dental Clinical Research Center, Ankylos Implant Clinical Research Group, Department of Veterans Affairs Medical Center, Ann Arbor, MI 48105, USA.
authors.forename: Harold F
authors.initials: HF
authors.lastname: Morris
authors.forename: Shigeru
authors.initials: S
authors.lastname: Ochi
authors.forename: Patricia
authors.initials: P
authors.lastname: Crum
authors.forename: Ira H
authors.initials: IH
authors.lastname: Orenstein
authors.forename: Sheldon
authors.initials: S
authors.lastname: Winkler
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D001863:Bone Screws; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D019232:Dental Restoration Failure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013499:Surface Properties
chemical_list: D015921:Dental Implants