Effect of Silane Reaction Time on the Repair of a Nanofilled Composite Using Tribochemical Treatment.

Abstract

To investigate the influence of silane reaction time on the repair strength of an aged nanofilled composite and to characterize the bonding mechanism. Nanofilled composite disks (n = 110, Filtek Supreme XT) were aged for 90 days in water. After tribochemical treatment (CoJet-Sand), the specimens were assigned to 5 groups (n = 22), primed with silane (Espe-Sil), and left to react for 1, 2, 3, 4, and 5 min. A thin layer of adhesive (Visio-Bond) was applied and a new composite with the same dimension was placed and cured. Non-aged specimens immediately layered and cured using the incremental technique served as controls. After aging (30 days in water plus 5000 thermal cycles), the interface was subjected to a shearing force until failure. Failure mode was evaluated under a stereomicroscope and scanning electron microscopy (SEM). Additional aged and treated surfaces were evaluated for morphology as well as elemental and molecular composition using SEM/EDX and ATR-FTIR. The mean shear bond strength (SBS) of the repaired specimens was 53.9 ± 8.6 MPa, with no significant difference among the various reaction times, but significantly lower compared to the control (88.1 ± 12.5 MPa). Tribochemical treatment created an irregular surface morphology with particles imbedded in the aged surface. Interfacial SEM/EDX analysis showed a 5-μm non-uniform high atomic number zone rich in Al and Si. Tribochemical treatments for repairing composite using a short silane reaction period (1 min) are equally effective as the prolonged reaction periods (2 to 5 min), yielding interfacial shear strength of ~60% of unrepaired material.