A Novel Silane System for Amalgam Repair with Resin Composite: an in vitro Study

The aim was to evaluate in vitro the feasibility of using three silane coupling agents/blends: (I) 1.0 vol % 3-acryloxypropyltrimethoxysilane (ACPS), (II) a novel silane system: 1.0 vol % 3-acryloxypropyl trimethoxysilane + 0.5 vol % bis-1,2-(triethoxysilyl)-ethane (ACPS + BTSE), and (III) a novel silane system: 1.0 vol % 3-acryloxypropyl trimethoxysilane + 0.5 vol % bis[3-(trimethoxysilyl)propyl]amine (ACPS + BTMA), as adhesion promoters on the repair of dental silver amalgam with a resin composite with respect to various artificial ageing conditions. Two hundred and forty flowable composite resin stubs were bonded to freshly prepared dental silver amalgam discs. The discs were silica-coated and silanized with the 3 silanes. Another 20 resin stubs were bonded to the amalgam surface without any silica-coating or treated with silica-coating only. Then, the specimens were randomly distributed into 8 sub-groups for initial (control), thermal cycling (1000, 3000 and 6000) and DI water storage (1 day, 1 week, 1 month and 3 months). Shear bond strength (SBS) test was measured using a universal testing machine with a 1 mm/min cross-head speed. Failure modes were classified and SEM images were obtained. Two-way ANOVA was used to detect statistical differences. The initial SBS of the control groups were (Mean/SD) 20.2 ± 3.3 MPa for ACPS only, 16.6 ± 3.9 MPa for ACPS + BTMA, and 19.5 ± 3.3 MPa for ACPS + BTSE. A decreasing trend of SBS was observed by using the current artificial ageing methods, and ACPS and ACPS + BTSE produced statistically higher bond strengths compared to ACPS + BTMA under thermal cycling (p<0.05). An acrylate silane alone or blended with a cross-linking silane may effectively promote bonding of a dental flowable resin composite to dental amalgam, which could be a new method to repair the restoration.