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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.

This study examined 1) factors that contributed to implant stability at placement and 2) the likelihood for an implant that was mobile at placement to osseointegrate. Eighty‐one (3.1%) of 2,641 implants placed by the Dental Implant Clinical Research Group between 1991 and 1995 were found to be mobile at placement. Seventy‐six (93.8%) of the 81 mobile implants were integrated at uncovering compared to 97.5% for the 2,560 immobile implants. Variables that influenced mobility at placement included patient age, implant design and material, anterior‐posterior jaw location, bone density, and use of a bone tap. Hydroxyapatite (HA)‐coated implants were slightly more likely to be mobile at placement (P = 0.324) than non‐hydroxypatite (HA)coated implants. Of the 54 HA‐coated implants that were mobile at placement, all (100%) integrated, while only 17 (81.5%) of the 22 mobile non‐HA‐coated implants integrated (P = 0.003). Mean electronic mobility testing device values (PTVs) at uncovering for all implants mobile or immobile at placement that integrated were −2.9 and −3.6 respectively. PTVs for HA‐coated implants that were mobile (−3.5 PTV) or immobile (−4.0 PTV) at placement differed by 0.5 PTV, whereas non‐HA‐coated implants exhibited a greater difference of 1.2 PTVs at uncovering. HA‐coated implants, regardless of mobility at placement, integrated more frequently and exhibited greater stability than non HA‐coated implants. J Periodontol 1998;69:1404–1412.

The recommended prosthesis designs investigated in this study proved to be reliable, with encouraging success rates for an observation period of 36 months following placement.

Although implant stability at the time of placement is clearly desirable as seen in the superior 3-year survival of stable implants, it may not be an absolute prerequisite to osseointegration or to long-term survival. Several factors may influence the decision to remove or replace a mobile implant. HA-coating significantly improved the performance of both mobile and immobile implants at placement to 3 years post-placement (P < 0.001).

Primary implant stability and bone density are variables that have long been considered to be essential to achieving predictable osseointegration and long-term clinical survival. Although the dentist can control most factors associated with implant survival, bone density is the one factor that cannot be controlled. Measuring implant stability would assist in determining if an implant has integrated and is ready for the fabrication of the final prosthesis. Changes in implant stability in each type of Bone Quality (BQ-1, -2, -3, and -4), which may occur with time, have not been studied. Such information could help identify well-integrated implants and identify changes associated with impending implant failure. Several studies have used the Periotest instrument to study implant stability. Use of the Periotest implant stability will be studied during each phase of implant treatment for each bone density, and a range for clinically satisfactory integration will be suggested. Implant stability changes over time, and the changes are different for each bone density as the bone surrounding the nonhydroxyapatite implant becomes denser. This is clearly demonstrated in a postmortem histological specimen. The changes in implant stability (Periotest Values [PTVs]) are more apparent in BQ-1 and BQ-2 bone and less apparent in BQ-3 and BQ-4 bone. The Periotest is capable of providing valuable information concerning favorable or unfavorable changes in the bone-implant interface after uncovering. In addition, it can help identify when an implant is ready to be loaded. A new range of PTVs (-5 to -2) is suggested for monitoring the status of implants. Implants with PTVs more positive than -2 would indicate a bone-implant complex that may be marginal.

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

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