Purpose: As one type of glass fiber reinforced resin composite, Estenia C&B EG fiber (EG) has superior fatigue resistance. However, with straight clasps, exfoliation of glass fibers and some cracks occurred after the constant displacement fatigue test. In this study, to prevent the exfoliation of glass fibers, the fatigue resistance of EG clasps strengthened with a surface coating (SC) was evaluated by thermal cycling testing and constant fatigue testing. Methods: 24 teeth (500A, Nissin Inc.)

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... re prepared to make GFRC clasps with SC. The EG/SC clasps were subjected to thermal cycling for 5,400 cycles to mimic 6 months of intraoral use. The constant displacement fatigue test was carried out with a constant deflection of 0.25 mm loaded on the EG/SC clasp for 1,800 cycles. After testing, the clasp surface was observed by an optical microscope. Results: The result of the cyclic fatigue test after the thermal cycling revealed a microscopic crack. However, the loading which required a displacement undercut of 0.25 mm did not change. Conclusions: A recall has been required within 3 months of applying the coating. After the 3-month recall, any clasps in which SC is observed to have cracked and fallen off should have the SC reapplied.