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

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.

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.

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.

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.

The combination of phosphoric acid etching with Er:YAG laser provided the most favourable bond strength to enamel. Further morphological studies are currently ongoing.