AICRG, Part V: Factors influencing implant stability at placement and their influence on survival of Ankylos implants

Several factors influence primary stabilization of dental implants at placement surgery. These include implant design, bone quality, implant jaw location, and the use of a bone tap. This report evaluates clinical data gathered by the Ankylos Implant Clinical Research Group (AICRG) to assess (1) the influence of several variables on primary stability and (2) the potential for an Ankylos implant (Friadent GmbH, Mannheim, Germany) that is mobile at placement to integrate and survive for at least 3 years of clinical function. The Ankylos implant is a roughened grade-2 titanium screw. A total of 1554 implants were placed in 478 patients. At both the time of placement and abutment connection, the implants were tested for evidence of clinical mobility by attempting to rotate or move the implant with an application of force. Survival was recorded from placement and up to 36 months following placement. At placement, 2.8% were found to be mobile. In the maxillary posterior quadrant, 6.3% were clinically mobile. Implant mobility was frequent (12.2%) in jaw regions with poor-quality bone (BQ-4) or with short implants (8 mm = 8.3% mobile). Of the implants mobile at placement, 97.7% were stable at uncovering. The 3-year postplacement survival of initially mobile implants was 84.1% compared with 96.8% for implants not mobile at placement (chi2 test, P = .001). The Ankylos implant predictably promoted primary stability during surgical placement. Poor bone quality, short implants, and maxillary posterior jaw locations were all associated with a slightly higher rate of mobility at placement. Primary implant stability, while highly desirable, is not absolutely necessary for achieving osseointegration of Ankylos