Evaluation of retention forces and resistance to fatigue of attachment systems for overdentures: plastic and metal components.

Purpose: To compare retention forces of 3 overdenture attachment systems with metal and plastic components.

Materials And Methods: Four samples of each system evaluated (Ball-Attachment [metal]; O-Ring, and ERA [plastic]) were prepared and underwent fatigue and retention force in a universal testing machine. Maximum retention force (N) was measured at 6 time points (from 0 to 36 months-0.5 mm/min). Two-way analysis of variance and the Tukey test were used (α = 0.05).

Results: The Ball-Attachment group showed the highest retention values, statistically greater than the other systems, without differences during the trial (42.75-44.75). The ERA group had intermediate values and a statistically significant decrease during the trial (20.75-14). The lowest retention forces were found for the O-Ring group (13.75-11.75), with no statistical differences during the trial.

Conclusion: Retention forces are significantly affected by abutment type because the metal retainer was more retentive than plastics, possibly providing better fixation of the prosthesis in position, and more difficult to remove. After 6 months of simulation, retentiveness of both plastic components was similar. There was no fracture of any component.