Microtensile bond strength of different adhesive systems to primary and permanent dentin.

Purpose: The aims of this in vitro study were to: (1) compare bond strength of different adhesive systems to primary and permanent dentin using microtensile test; and (2) evaluate the interaction of these materials to primary and permanent dentin by means of scanning electron microscopy (SEM). Methods: Middle-coronal dentin surfaces of 18 exfoliated primary and 18 extracted permanent molars were exposed and teeth were randomly divided, according to their adhesive system, into 3 groups (N=6 per group): (1) Clearfil SE Bond (SE); (2) One Up Bond F (OU); and (3) Single Bond (SB). Then, 5-mm high composite blocks were constructed. After bonding procedures, the teeth were stored in distilled water at 37oC for 24 hours prior to the specimens’ preparation. For the microtensile test, teeth (N=5 per group) were longitudinally sectioned into 2 axes rendering beam-specimens that were glued to special devices, which were mounted in a Universal Testing Machine to be loaded under a crosshead speed of 1 mm/min until fracture. One tooth of each group was prepared for SEM. Results: Microtensile bond strength mean values (MPa) to primary/permanent dentin were: (1) SE=60.0/61.4; (2) OU=54.5/53.3; and (3) SB=70.1/64.9. Two-way analysis of variance (ANOVA) showed no significant differences (P>.05) for the bond strength values among primary and permanent dentin groups, neither among groups SE×SB and SE×OU. SEM images of SE and SB showed a well-defined, uniform, and continuous hybrid layer. A continuous hybrid layer, however, was not found for OU. Conclusions: Bond strength and micromorphologic characteristics of the adhesive systems evaluated were not influenced by the substrate. OU achieved worse results. (Pediatr Dent 2005;27:457-462)