Clinical Relevance The use of resin-modified glass ionomers as cavity liners in the closed-sandwich technique reduced microleakage in Class II composite restorations.

The major objectives of this study are to identify the best activation procedure between commonly used procedures that can significantly reduce the conditioning duration and to understand the change in interfacial properties during conditioning. In order to do that, three on‐line activation procedures were employed for activating of identical MEAs in PEMFC and studied by polarization curve and electrochemical impedance spectroscopy (EIS). These methods are constant current (0.25 A cm–2) for 19 h, constant voltage (0.6 V) for 9 h, and USFCC protocol.The best performance was achieved by USFCC protocol within 15 h, but by constant voltage procedure, 96% of mentioned protocol was obtained during 6 h. So constant voltage activation proceeded remarkably fast, and most of the activation process was achieved in the first few hours.Obtained results from Nyquist plots during/after MEA conditioning indicate mentioned process are irreversible and interfacial structures of MEAs are different even after finishing of MEA break‐in. It could be affected the MEA performance and even its durability. These results are consistence with the obtained performance of activated MEAs either in H2/air or H2/O2 PEMFC. We found the mentioned constant current procedure consume long time without reaching to expectable performance even after 19 h.

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