[Comparative evaluation of retention loss in four types of attachments used on overdentures in function of time of use].

The aim of this study was to evaluate and compare the retentive capacity between two O-ring and O-SO system (Group I), and two ERA system types - white and gray retention caps - (Group II), respectively, in simulated function in database, 6 months, 1, 2, 3, 4, and 5 years later, with insertion and removal cycles. Two Brånemark implants were fixed in two trapezoidal metallic bases for the tests. Removal and insertion tests were done in a sewing machine, adjusted for this purpose using a belt and a pulley system, moving a steel crankshaft.