Shear Bond Strength of Orthodontic Brackets Luted with RMGIC After Er:YAG Laser Etching with Two Pulse Modes Using a Digitally Controlled "X-Runner" Handpiece

Objective: To compare the shear bond strength (SBS) values of orthodontic brackets luted using a resin-modified glass ionomer cement (RMGIC) on enamel surfaces etched using either an Er:YAG laser in two different working modes, or a conventional etching protocol, including phosphoric acid. Materials and methods: Sixty healthy human premolars were randomly allocated to three experimental groups (n=20) and etched with: Group 1: Er:YAG laser in super-short pulse (SSP) mode (100 mJ, 20 Hz, 2 W); Group 2: Er:YAG laser in quantum square pulse mode (120 mJ, 10 Hz, 1.2 W) using a digitally controlled handpiece ("X-Runner"); Group 3 (control): 5.25% sodium hypochlorite pretreatment, then 37% phosphoric acid for 15 sec. Stainless steel brackets were bonded using light-curing RMGIC for orthodontic bonding. After term cycling (1800 cycles), SBS testing was performed using a universal testing machine. After debonding, both enamel and bracket surfaces were examined to determine the amount of RMGIC still present on the surfaces. Results: Group 3 surfaces gave the lowest mean SBS (10.6104 +/- 2.66196 MPa), whereas Group 1 provided the highest 1 (13.1795 +/- 3.37904 MPa), which was significantly different from the control (Group 3, p=0.0226). Group 2 provided intermediate values (11.8486 +/- 0.59832 MPa) nonsignificantly different from the control or from SSP (p=0.4215 and p=0.3082, respectively). Conclusions: Er:YAG laser treatment in SSP mode of enamel surfaces for orthodontic bonding provided higher SBS and a shear behavior of the luting material similar to the conventional acid-etching procedures, making it a viable alternative to acid etching.