The objective of this study will be: 1 - sintering thio-urethane oligomers and formulate experimental resin cement; 2 - evaluate the flexural strength and elastic modulus of the experimental resin cement with added thio-urethane oligomers 20wt% and commercials resin cement added thio-urethane oligomers to IPS e.max Press ceramic; e, 3 - evaluate the influence of thermal cycling and fatiugue on the µtensile bond test of the interface ceramic IPS e.max Press / experimental resin cement modified with thio-urethane oligomers and commercials modified thiourethane oligomers. Study 1 - The elastic modulus and flexural strength of the experimental and commercials resin cement with added thio-urethane oligomers 20wt% will be evaluated. The two properties will be measured in three-point bending mode (n=5). One hundred and twenty discs (15-mm diameter, 0.5-mm thickness) IPS e.max Press (Ivoclar Vivadent) will be obtained, etched with hydrofluoric acid at 10% for 20 seconds and silanized. The resin cements will be applied in the etched surface of the ceramic discs simulating the cementation process, forming ceramic-cement sets with a thickness of 120 ± 20 µm. The control group will be compound of samples of ceramic discs without resin cement: negative (unconditioned disc), positive (conditioning and silanized disc) and submitted to biaxial bending mode at a crosshead speed of 1.0 mm/minute until failure. Study 2 - One hundred and eight square ceramic blocks (8 mm x 8mm x 3 mm thick) will be made with PS e.max Press (Ivoclar Vivadent) ceramic, in accordance with the manufacturer's instructions and divide divided into 18 groups (n=6) and bonded with: Groups 1 to 3 - experimental resin cement; Groups 4 to 6 - experimental resin cement with thiourethane oligomers (aliphatic); Grupos 7 a 9 - experimental resin cement with thiourethane oligomers (aromatic) ; Groups 10 to 12 - RelyX Ultimate; Groups 13 to 15 - RelyX Ultimate with thiourethane oligomers (aliphatic); and, Groups 16 to 18 - RelyX Ultimate with thiourethane oligomers (aromatic). All specimens will be etched with 10% hydrofluoric acid for 20 seconds and two layer of silane will be applied on the ceramis surface. The ceramic blocks will be bonded to a block of the composite (Z250, 3M ESPE) according to the groups of 1 to 18. Light-activation will be performed for 40 seconds at right angles to each of the IPS e.max Press/Z250 margins (four activations) using an LED source (Radii Plus; SDI 5, Ultradent), with a final 40-second light exposure from the top surface. After bonding, all specimens will be stored in distilled water at 37oC for 24 hours. The specimens of groups 2, 5, 8, 11, 14 e 17 will be submitted to a fatigue test of 250,000 cycles; and the specimens of groups 3, 6, 9, 12, 15 e 18 will be submitted to 10,000 thermal cycles between 5oC and 55oC (dwell time of 30 seconds). The blocks will be sectioned perpendicular to the bonding interface to obtain sticks with a bonding area of 1 mm2 and submitted to the µtensile bond test at a crosshead speed of 1.0 mm/min until failure Data from the study will be submitted to appropriate statistical analysis.
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