FDPs were etched with 5% hydrofluoric acid (Fórmula e Ação Farmácia, São Paulo, Brazil) for 1 min, rinsed with water, and dried. Adhesive and optimizer agent were applied following the same steps aforementioned.
A dual-cured resin cement (Variolink II, Ivoclar Vivadent, Schaan, Liechtenstein) was poured and mixed as recommended by the manufacturer and applied to the intaglio surfaces of the FDPs, which were seated on the preparations. Each bridge was then held in position by a metal rod (26.45 oz) positioned in the center of the occlusal surface, excess cement was removed, and each abutment was light-activated for 40 s on the buccal, lingual, and occlusal surfaces by a LED curing light with a wavelength ranging from 440 to 480 nm (Radii-cal, SDI). Then, the cemented sets (Fig. 3A ) were positioned in a rectangular metallic matrix, which was filled by polyurethane (F 16 and F 16 ISO, Axson Technologies, Eaton Rapids, MI, USA) until 1mm apart from the finishing line of preparations (Fig. 3B ). This made possible an easily insertion of the polyurethane blocks on the device designed for mechanical testing (Fig. 3C ). After the polyurethane was cured, the sets were stored in grade 3 distilled water for five days before the fatigue test.
A dual-cured resin cement (Variolink II, Ivoclar Vivadent, Schaan, Liechtenstein) was poured and mixed as recommended by the manufacturer and applied to the intaglio surfaces of the FDPs, which were seated on the preparations. Each bridge was then held in position by a metal rod (26.45 oz) positioned in the center of the occlusal surface, excess cement was removed, and each abutment was light-activated for 40 s on the buccal, lingual, and occlusal surfaces by a LED curing light with a wavelength ranging from 440 to 480 nm (Radii-cal, SDI). Then, the cemented sets (