Spline implant prospective multicenter study: interim report on prosthetic screw stability in partially edentulous patients.
Loosening of implant abutment and prosthesis screws during functional loading is an industry-wide phenomenon that is especially well documented with the external hexagon implant connection. Although numerous efforts to reduce or eliminate screw loosening have been attempted, the problem still persists, especially with implant restorations in the partially edentulous patient. In 1992, the spline was developed as an alternative to the external hexagon implant-abutment connection. A prospective multicenter study was begun in 1996 to evaluate the abutment and prosthesis screw joint stability of Spline dental implants (Centerpulse Dental Division, Carlsbad, California) over 5 years of post-loading clinical follow-up. From October 1996 to December 2000, 73 partially edentulous patients were consecutively treated with 113 Spline implants placed in two private dental practices. Three patients with 1 implant each withdrew from the study for various reasons; of the remaining 110 implants in 70 patients who continued in the study, 82% (n = 90) were placed between 1997 and 1998. No cases of abutment or prosthesis screw loosening occurred with up to 54 months (mean = 38.95 mo; range, 3-54 mo; mode, 20 mo) of post-loading clinical follow-up. These interim findings of the ongoing study suggest that Spline dental implants may provide a stable prosthetic connection in partially edentulous cases during short-term clinical follow-up.