Survival and stability (PTVs) of six implant designs from placement to 36 months

Numerous new implant designs and materials have become available over the last decade, each with special claims of superiority in restoring complex cases. Differences in existing clinical databases, study designs, and methods of determining failures/survival are seldom standardized, which complicates comparisons of clinical performance of these new designs. Little information is available concerning the changes in stability of various designs and materials following clinical loading.

A total of 30 VA medical centers and 2 dental schools combined to form the Dental Implant Clinical Research Group (DICRG). More than 2,900 implants were placed, restored and data gathered from the time of placement to 36 months. Implant stability from uncovering to 36 months and survival from placement to 36 months were determined. Survival was determined using two different approaches--considering all implants removed at any time, regardless of the reason (DICRG approach), and considering only those that were removed following loading of the prosthesis (post-loading approach). Survival was also determined for each of the three phases of implant treatment--phase 1, from the time of placement to uncovering and abutment connection; phase 2, from uncovering to placement and loading of the prosthesis; and phase 3, from loading of the prosthesis to 36 months.

The two approaches to determining survival for each implant design and/or material included in the study showed differences in reported numbers ranging from 1.1% to 21.7%. The largest difference in survival was for the commercially pure titanium screw (used in this study only in the maxillary completely edentulous applications), which showed a 21.7% greater survival rate. With the DICRG approach, the hydroxyapatite (HA)-cylinder had the highest survival (97.5%). When considering the post-loading approach, the titanium-alloy screw had the highest survival (99.4%), with the HA-cylinder having the next highest survival (98.6%). The HA-cylinder did not show increased stability from uncovering to 36 months, and the HA-grooved implant became less stable.

HA-coated implants demonstrated the highest survival rate; 2) the post-loading analysis approach inflated survival; 3) non-HA implants showed increased stability following loading; 4) HA-coated implants showed a slight decrease or no change in stability; and 5) the clinical significance of the changes in implant stability must be determined for the long-term.