Transbond xt light cure adhesive

One orthodontist (J.H.P.) bonded orthodontic brackets to the teeth of the RP model using transfer jigs. The surface of the RP model was treated with the bonding agent (Transbond™ XT Primer, 3M Unitek, Monrovia, CA, USA), and the brackets were bonded with the resin adhesive (Transbond™ XT Light Cure Adhesive, 3M Unitek, Monrovia, CA, USA). Although bonding agents and resin adhesive are bonding materials used for natural teeth, not for RP models, they were used to bond the brackets on the RP model in this study to reflect the clinical situation. The resin adhesive was cured with a light curing device (VALO, Ultradent, South Jordan, UT, USA). Then, the transfer jigs were separated from the orthodontic brackets bonded onto the surface of the RP model. After removing the jigs, RP models with the bonded brackets were scanned using an intraoral scanner (Trios 3, 3shape, Copenhagen, Denmark). The 3D information about each bracket position on the RP model was obtained through this process, and the images were converted to STL files to match with the scanned initial dental models, which were also converted to STL files.

The bonding procedure in the laser-irradiated and acid-etched groups followed the manufacturer's instructions. Stainless steel premolar brackets with a surface area of 10 mm² (American Orthodontic Co., Washington Avenue, Sheboygan, Wisconsin, USA) were used in this study and bonded by an adhesive paste (Transbond XT Light Cure adhesive primer and Transbond XT adhesive resin, 3M Unitek, Monrovia, California, USA). The braces were placed firmly on the tooth surface and cured with mini-LED (Acteon, France) for 40 s in the mesial, distal, occlusal, and gingival aspects (10 s each); then, they were placed in distilled water at 37°C for 24 hours.
To imitate the heat and humidity conditions of the oral cavity, all specimens were placed in an automatic thermocycling apparatus (SD Mechatronik Thermocycler, SD Mechatronik GmbH, Feldkirchen-Westerham, Germany) with water baths maintained at 5°C and 55°C for 30 s cycles, for a total of 500 cycles [22 ]. After 2 days of storage at room temperature in distilled water, a shear bonding test was performed.