Shear Bond Strength of a Novel Silorane Adhesive to Orthodontic Brackets and Unprepared Bovine Enamel

Purpose: To evaluate the suitability of a novel epoxy-based resin, Filtek Silorane, for orthodontic bracket bonding on unprepared enamel. Materials and Methods: Shear forces to bovine enamel were measured for Filtek Silorane and Transbond XT in combination with steel, ceramic, and polymer brackets. For Filtek Silorane, etching was performed with the Silorane self-etching primer alone or an additional previous application of phosphoric acid. Transbond XT (conventional methacrylate) was used for the control group and the enamel was previously etched with 35% phosphoric acid. All samples were thermocycled (1000X, 5°to 55° C). Shear bond testing was done with an Instron 3344 at a crosshead speed of 1 mm/min. In addition, adhesive remnant index (ARI) scores were evaluated. Results: The shear forces showed a weak adhesion of Filtek Silorane to unprepared enamel both with the selfetching primer and conventional etching (0.87 to 4.28 MPa). The shear forces of the control group were significantly higher (7.6 to 16.5 MPa). The ARI scores showed a clear failure at the enamel/adhesive interface for all Filtek Silorane samples. For the combination of Transbond XT and different brackets, the failure was found at the adhesive/bracket interface. Conclusion: The novel epoxy-based resin Filtek Silorane is not appropriate for bonding of brackets to unprepared enamel. Keywords: shear force, silorane, adhesive, bonding