Background: There is a lack of clinical studies on the self-aligning attachment system (Locator(R); Zest Anchors, Inc. homepage, Escondido, CA, USA) for two-implant-retained overdentures in the edentulous mandible. Therefore, a comparison of the Locator with two traditional designs (a rotational gold matrix and a rubber O-ring type) in clinical 1-year use was conducted.
Materials and methods: From 2003 to 2007, 60 patients received two Osseotite(R) TG Standard implants (BIOMET 3i Implant Innovations, Palm Beach Gardens, FL, USA) in the intraforaminal area of the edentulous mandible. The implants were left unloaded for 3.5 months, randomized to three different attachment systems, and loaded through a mandibular overdenture. Twenty-three patients received a self-aligning attachment system (Locator) and 33 patients a ball attachment (Dal-Ro(R)[BIOMET 3i Implant Innovations]n = 25; TG-O-Ring(R)[Cendres & Metaux SA, Biel-Bienne, Switzerland]n = 8). After 12 months of delivery of the overdentures, the oral situation was evaluated: prosthodontic maintenance and biologic complications, subjective patients' experience, and oral health-related life quality (Oral Health Impact Profile [OHIP-G 49]).
Results: After 1-year of clinical service, 8 of 120 implants were lost (9.6%). The Locator system brought up 34 prosthetic complications, especially the need for change of the male parts or activation because of loss of retention. The TG-O-Ring patients showed 14 complications, most of them the change of the O-Rings. The patients with the Dal-Ro abutment had seven minor complications in 12 months of clinical use. Biologic complications and patients' oral health-related life quality showed no significant difference among the three experimental groups.
Conclusions: Prosthodontic maintenance was restricted to loss of retention for all systems. Within the observation period of this study, the self-aligning attachment system showed a higher rate of maintenance than the ball attachments. The patients' oral health-related life qualities as well as the biologic parameters do not differ when using the three abutment systems.