Clinical Performance and Material Properties of Single-Implant Overdenture Attachment Systems

Purpose: The aim of this study was to evaluate the mechanical properties of different attachment systems used for mandibular single-implant overdentures and to compare their wear/deformation features with clinical performance in patients after 1 year. Materials and Methods: Three attachment systems were evaluated: large 5.9-mm titanium nitride-coated ball attachments with plastic matrices, standard 2.25-mm uncoated titanium alloy ball attachments with Dalla Bona-type gold alloy matrices, and Locator attachments of titanium nitride-coated patrices and nylon matrices. The hardness and elastic modulus of the systems were determined using the nanoindentation technique. Twelve attachments from each system were used in 36 edentulous patients to support mandibular single-implant overdentures. After 1 year, 5 samples from each system were retrieved and evaluated for wear changes under a scanning electron microscope. Results: The titanium nitride-coated patrices, regardless of system, appeared unchanged and did not require any maintenance. Extensive wear was evident in the uncoated titanium alloy patrices and Dalla Bona-type gold alloy matrices, resulting in high maintenance (15 activations). Minimal wear was observed in the plastic matrices with minimal maintenance (2 replacements). The Locator nylon matrices showed extensive deformation and deterioration with a substantial need for maintenance (16 replacements). The performance of the patrices was related to hardness, while that of the matrices was related to the creep response. Conclusions: Large ball attachment systems of titanium nitride-coated patrices and plastic matrices reflect favorable wear behavior and clinical performance. These attachments are recommended for patients receiving mandibular single-implant overdentures.