Comparison of Bond Strength of Different Indirect Composite Systems and CAD/CAM Composite Blocks between Dentin and Composite Surfaces: An in vitro study

Abstract

Abstract This study aims to compare the shear bond strength of different indirect restorative materials bonded to the microhybrid composite and dentin surfaces. A total of 192 cylindrical specimens (3mm height, 3mm diameter) were prepared from GradiaPlus, GC(GRA); CeramageBody, Shofu(CER); TesceraATL, Bisco(TES); and Lava Ultimate, 3M Espe(LAV) materials. In addition, 48 newly extracted molars were embedded in acrylic resin 2 mm below the cementoenamel junction and sliced horizontally using a cutting device (IsoMet 1000; Buehler, USA) to form flat dentin surfaces. Using a specially customized 4x2mm disc-shaped mold, 48 disc-shaped composite surfaces were obtained with the Z250 Microhybrid composite (3M Espe, USA) material by layering technique. A total of 2 cylindrical indirect composite specimens were cemented to each disc-shaped composite and flat dentin surfaces. Samples obtained from indirect composite were divided into 16 groups in total, with two different subgroups luted with RelyX U200(RX-U200) self-adhesive cement (3M Espe, USA) and RelyX Ultimate(RX-ULT) clicker dual-cure cement (3M Espe, USA) to the dentin and microhybrid composite surfaces (n = 12). Groups are respectively: 1)GRA + Dentin + RX-U200 2)TES + Dentin + RX-U200 3)CER + Dentin + RX-U200 4)LAVA + Dentin + RX-U200 5)GRA + Composite + RX-U200 6)TES + Composite + RX-U200 7)CER + Composite + RX-U200 8)LAVA + Composite + RX-U200 9)GRA + Dentin + RX-ULT 10)TES + Dentin + RX-ULT 11)CER + Dentin + RX-ULT 12)LAVA + Dentin + RX-ULT 13)GRA + Composite + RX-ULT 14)TES + Composite + RX-ULT 15)CER + Composite + RX-ULT 16)LAVA + Composite + RX-ULT (n = 12). The Shear Test was carried out by applying 0-400 N loading and 1 mm/min force to each sample at Instron Universal Testing Machine. Light microscopy and SEM were used to examine the failure type. The results obtained in the study were evaluated by using ShapiroWilk's test, Mann-Whitney U test and Chi-Square test.(p < 0.05) Significantly higher bonding values were obtained in the specimens bonded to the surface of Z250 microhybrid composite (3M ESPE, USA) compared to the specimens bonded to the dentin surface (p < 0.001). When the shear strength of indirect restoration materials is compared; the highest value was measured in the CER + Composite + RX-ULT(Av:91.41Mpa) group, and the lowest value was measured in the LAVA + Dentin + RX-U200(Mean:35.96Mpa) group(p < 0.001). When the bond strengths of the cement systems were compared, RX-ULT dual-cure cement showed higher bond strength values than RX-U200 self-adhesive cement on both dentin and Z250 Microhybrid composite surface (p < 0.05).