RESUMO
This study aimed to evaluate the effect of three hydrofluoric acid (HF) etching periods on the micro-tensile bond strength between two CAD-CAM ceramic systems [Vita Suprinity (VS) and feldspathic CEREC blocs (CB)] and a composite resin. The ceramics were categorized into six groups based on the surface conditioning protocol used, as follows: G1: CB-HF 5% for 20 s; G2: CB-HF 5% for 40 s; G3: CB-HF 5% for 60 s; G4: VS-HF 5% for 20 s; G5: VS-HF 5% for 40 s; G6: VS-HF 5% for 60 s. Scotchbond Universal was applied onto the pretreated ceramic surfaces and covered with Filtek Z350 XT composite resin. After 24 h, the specimens were cut into microbars (n = 16) and a micro-tensile bond strength test (µTBS) was carried out. An optical microscope was used to examine the fractured microbars. The results showed statistically significant differences between the factors tested (p < 0.01). Moreover, the mean MPa of G1(17.27), G2(13.03), G3(12.82), G4(15.83), G5(21.66), and G6(14.50) was seen to significantly differ. The predominant failure type observed was adhesive, and all three periods of HF etching produced satisfactory bonding between the composite resin and CB. An etching time of 40 s provided the highest µTBS value for VS.