ESEM evaluation of three FRC post bonding systems

Objectives: The purpose of this study was to compare the interfaces formed by three different adhesive luting systems between endodontic posts and root canal dentine. Methods: A total of 120 extracted incisors and canines were treated endodontically and randomly divided into three groups of 40 specimens each. FRC Postec Plus posts (Ivoclar Vivadent, Liechtenstein) were inserted according to the manufacturers instructions using the following adhesive and luting systems (all Ivoclar Vivadent): Group 1: One-step total etching system Excite and Multicore Flow; Group 2: Two-step self-etching system AdheSe and Multicore Flow; Group 3: One-step self-etching system and luting resin Multilink Automix. After storage in 0.9% saline solution the teeth were sectioned longitudinally with a diamond saw at low speed and intense water coolant followed by acid etching. The specimens were evaluated by environmental SEM at cervical, middle and apical levels using morphological criteria. The data were statistically analyzed by means of Chi-square test. Results: The formation of a complete hybrid layer along the entire root was observed in 52.5, 45 and 35% of the cases within the groups 1, 2 and 3, respectively. There were significant differences between the groups in the cervical and middle third of the root. Deficiencies of the hybrid layer increased in apical direction, but statistical significance was only found in group 2. Cohesive defects of the post-dentine interface were not dependent on the material or the distance from the orifice. Corresponding to the imperfect hybrid layer, failures of the dentine-adhesive interface dominated in group 3; while in group 1 and 2 the adhesive-resin interface was more frequently disrupted. Conclusions: The total etching system showed the best quality of bond zones, followed by the two-step and the one-step self-etching system. Keywords: endodontic posts, ESEM, bonding systems, adhesion