Achieving reliable bracket adhesion to CAD/CAM provisional crowns is clinically challenging. This study evaluated various surface treatments to determine which method provides the strongest bond strength for metal orthodontic brackets. A total of 30 lower bicuspids and 180 provisional crowns were included and randomly assigned to six groups according to surface preparation: Group 1 (no treatment), Group 2 (diamond bur), Group 3 (sandblasting), Group 4 (Plastic Conditioner), Group 5 (diamond bur + Plastic Conditioner), and Group 6 (sandblasting + Plastic Conditioner). Natural teeth were etched with 37% orthophosphoric acid. Brackets were bonded using Transbond XT® Primer and Transbond XT® Paste. Samples underwent artificial aging before measuring shear bond strength. The adhesive remnants on crown surfaces were analyzed after bracket removal.
The strongest bond strength was recorded for natural teeth, followed closely by Groups 5 and 6. Group 1 had the weakest bonding values. Similar performance was observed between Groups 2 and 4, as well as between Groups 5 and 6. Statistical analysis indicated significant differences among most groups (p < 0.001), except between Groups 2 and 4 (p = 0.965) and Groups 5 and 6 (p = 0.941). Bracket adhesion to provisional crowns is less predictable than to natural teeth, as conventional phosphoric acid etching has minimal effect on provisional materials. Surface preparation combining either a diamond bur or sandblasting with Plastic Conditioner effectively enhances bond strength, achieving levels comparable to those on natural teeth.
