Adhesion to primary dentin: Microshear bond strength and scanning electron microscopic observation

To compare the bond strength to human primary dentin of a self-adhesive light-curing resin composite, a self-etch adhesive and a glass-ionomer cement by means of microshear bond strength (piSBS) test and scanning electron microscopic SEM observations. Methods: 75 human primary molars were sectioned to obtain a 2 mm-thick slab of mid-coronal dentin, randomly divided into three groups (n=25). Nine conical frustum-shaped buildups were constructed on the occlusal surface of each dentin slab using a self-adhesive light-curing resin composite (Vertise Flow; Group 1), bonding agent (Optibond All-in-One; Group 2) combined with resin composite (Premise Flow) and a glass-ionomer cement (Ketac-Fil; Group 3). After thermocycling, specimens were subjected to fiSBS test. All debonded specimens were observed at SEM. Data were analyzed by a mixed model and chi-square test. Results: The bond strength measured in Group 1 (9.0±4.5 MPa) was significantly lower than that one recorded in Group 2 (20.2±12.5 MPa) although it was significantly higher than the one recorded in Group 3 (4.8±2.3 MPa). Failures were mainly adhesive in all groups.