A new epoxy-based resin, Filtek Silorane, has recently been introduced for restorative dental fillings. This study aimed to assess its effectiveness for orthodontic bracket bonding on unground enamel. Shear bond strength was tested using two adhesives—Filtek Silorane and Transbond XT—paired with steel, ceramic, and polymer brackets. Filtek Silorane was applied following either its self-etching primer protocol or conventional phosphoric acid etching, while Transbond XT, etched only with phosphoric acid, served as the control. All specimens underwent 1000 thermo-cycles between 5 and 55 °C. Shear testing was performed using an Instron 3344 machine, and ARI scores were recorded. Results indicated that Filtek Silorane exhibited poor adhesion to unprepared enamel, regardless of the etching method (0.87–4.28 MPa), whereas the control group showed significantly higher bond strength (7.6–16.5 MPa). ARI analysis revealed that failures with Filtek Silorane occurred at the enamel-adhesive interface, while failures with Transbond XT predominantly occurred at the adhesive–bracket interface. Overall, the epoxy-based resin Filtek Silorane is unsuitable for bonding brackets to unground enamel.
