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\u2009=\u200920) and etched with: Group 1: Er:YAG laser in super-short pulse (SSP) mode (100\u2009mJ, 20\u2009Hz, 2\u2009W); Group 2: Er:YAG laser in quantum square pulse mode (120\u2009mJ, 10\u2009Hz, 1.2\u2009W) using a digitally controlled handpiece (\u201cX-Runner\u201d); Group 3 (control): 5.25% sodium hypochlorite pretreatment, then 37% phosphoric acid for 15\u2009sec. 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\u2009\ub1\u20092.66196\u2009MPa), whereas Group 1 provided the highest 1 (13.1795\u2009\ub1\u20093.37904\u2009MPa), which was significantly different from the control (Group 3, p\u2009=\u20090.0226). Group 2 provided intermediate values (11.8486\u2009\ub1\u20090.59832\u2009MPa) nonsignificantly different from the control or from SSP (p\u2009=\u20090.4215 and p\u2009=\u20090.3082, 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