Effect of Orthophosphoric Acid and Er:YAG Laser Etching on Micro-shear Bond Strength to Enamel: An In Vitro Pilot Study

Background: Dental conditioning is one of the most important phases during enamel bonding procedures to obtain clean surfaces, smear layer removal with collagen active sites and hydroxyapatite exposure. Objective: The aim of this study was to compare the micro-shear bond strength (μSBS) of different adhesive systems after two different etching techniques: 37% orthophosphoric acid (H3PO4) and Er:YAG laser. Methods: Ninety permanent extracted molars were embedded into epoxy resin blocks and sectioned longitudinally. Specimens were randomly assigned to one of the following groups (n=30), depending on the etching protocol: 37% H3PO4 for 30 s (Group 1), Er:YAG laser 100mJ-10Hz (Group 2), and Er:YAG laser 100mJ-10Hz followed by 37% H3PO4 for 30 s (Group 3). Each group was further divided into two subgroups depending on the bonding agent used on enamel (n=15): A) EE-Bond (Tokuyama) and B) Peak universal (Ultradent). A two-way analysis of variance (two-way ANOVA) was conducted and the level of significance was set to p=0.05. Results: The etching procedure was a significant factor influencing the results (p=0.006), while no differences were observed for the two adhesive systems tested (p>0.05). Group 3 recorded the highest bond strength values, according to the following sequel: Group 3 < Group 2 < Group 1 < 0.05. Conclusion: The combination of phosphoric acid etching with Er:YAG laser provided the most favourable bond strength to enamel. Further morphological studies are currently ongoing.