ABSTRACT
PURPOSE: Factors affecting the retention of fixed prostheses to natural abutments are well understood. In contrast, little is known concerning factors influencing the retention of fixed prostheses cemented to implant abutments. The purpose of this study was to investigate the effect that varying implant abutment wall height, platform size, and screw access channel filling method has on the retention of castings cemented to implant abutments using TempBond. MATERIALS AND METHODS: Four 15 degrees preangled abutments (Nobel Biocare Replace Select Esthetic) of each platform size--narrow (NP), regular (RP), and wide (WP)--were used. In each group of abutments the screw access axial wall was either unadjusted, one-third removed, two-thirds removed, or completely removed. The screw access channels were either fully or partially filled with Memosil, a vinyl polysiloxane impression material. For each abutment a casting was constructed that incorporated an attachment to allow removal. Castings were cemented to abutments with TempBond. The tensile force required to separate the cemented castings from the abutments was measured using an Instron Universal load-testing machine. RESULTS: The mean peak removal force for comparable abutments was significantly different ( p < 0.05): (1) where the screw access channel was completely filled with Memosil compared with those partially filled with Memosil; (2) with platform sizes--WP > RP > NP; (3) with alteration of axial wall height--1/3 removed > unadjusted = 2/3 removed > total wall removal. CONCLUSIONS: The retention of castings cemented to implant abutments with TempBond is influenced by the wall height, platform size, and the filling modality of the screw access channel.
