Purpose: Attachments are widely used for the fixation, retention, and stabilization of prostheses. This study assessed the retentive forces of 3 types of attachments for root-retained overdentures.
Methods: The patrices of “O” ring plastic pattern anchor (OPA) attachments (No. 2; Inoue Attachments), magnetic attachments (MAs; 3513, Neomax), and coping telescopes (CTs) were cast with an Ag-Au-Pd alloy (Castwell, GC). For the OPA and MA, the “O” ring and magnet were fixed on the post anchor and keeper, respectively, by using autopolymerized polymethyl methacrylate (PMMA) resin (Unifast II, GC). For the CT, autopolymerized PMMA was used to connect the patrix coping and matrix framework. The retentive force (n=5, N) was measured at a crosshead speed of 20 mm/min as the maximum load when the connected patrix and matrix of either single or double retainers (30-mm apart) were separated under both dry and wet conditions. The results were analyzed using ANOVA/Tukey’s HSD test (α=0.05).
Results: In the case of a single retainer, the retentive force of the CT was significantly greater than those of the MA and OPA (P<0.05). However, the coefficient of variation of the CT was also greater. In the case of double retainers, the retentive forces of all the attachments were approximately twice the forces of single retainers.
Conclusion: Although the CT exhibited the greatest retention, the retentive force of each CT specimen varied widely. Consistent retentive values were obtained for the OPA and MAs because ready-made patterns of these attachments were used.