Retention force and fatigue strength of overdenture attachment systems

<jats:p><jats:bold><jats:sc>summary</jats:sc> </jats:bold> This study evaluated retention force and fatigue resistance of two overdenture attachment systems. Twenty samples (O‐ring and Bar‐Clip) from two manufacturers (Conexão Sistemas de Prótese and Lifecore Biomedical) were prepared and divided into four groups: (i) Conexão/O‐ring; (ii) Conexão/Bar‐Clip; (iii) Lifecore/O‐ring and (iv) Lifecore/Bar‐Clip, with five samples in each group. They were submitted to mechanical fatigue test using a servohydraulic machine performing 5500 cycles of insertion and removal (<jats:italic>f</jats:italic>=0·8 Hz), immersed in artificial saliva. Retention force values were obtained three times (0, 3000 and after 5500 cycles) simulating the clinical service, using a tensile strength at 1 mm min<jats:sup>−1</jats:sup> and load cell of 1 kN. Data were analysed with analysis of variance and Tukey's test at 5% level. Results showed that Conexão/Bar‐Clip specimens had significantly higher retention values than Lifecore/Bar‐Clip (44·61 and 18·44 N, respectively), Conexão/O‐ring specimens had significantly lower values than Lifecore/O‐ring (13·91 and 19·75 N, respectively). Conexão/Bar‐Clip values were always significantly higher than those of Conexão/O‐ring group (44·61 and 13·91 N, respectively). Lifecore (O‐ring and Bar‐Clip) presented similar values (19·75 and 18·44 N, respectively). The systems evaluated showed satisfactory retention force values, before and after fatigue testing. Conexão/Bar‐Clip specimens presented the highest values. A 5‐year simulation of insertion and removal did not decrease retention values or fracture components.</jats:p>