How Silane Drying Time Effects Repaired Composite Shear Bond Strength?

Objectives: The aim of this study was to test the influence of silane drying time on the shear bond strength (SBS) of fresh to aged composite interfaces. Methods: Disc shaped composite specimens (Filtek Supreme XT/3M-ESPE /4X3 mm, 40s exp @ 700 mW/cm2) aged in water (37°C /30 days) were surface treated by Cojet sand (3M-ESPE) and classified into five groups (A-E, n: 25). The sandblasted surfaces were treated with silane coupling agent (ESPE-SIL/3M-ESPE) and let dry for 1, 2, 3, 4 and 5 min respectively. Fresh composite was added to the treated surfaces and cured as above, yielding two-layer composite cylinders (4X6 mm). A control group (F) of unrepaired composite (4X6mm, n: 25) was irradiated from top and bottom sites (2x40s). All specimens were stored in water (37°C/48h), thermal-cycled (5-55°C,1000X@2c/min) and subjected to shear debonding at the interface of the fresh and aged composite (groups A-E) or at the middle of the specimens (group F) (1mm/min). Data were analyzed by ANOVA and Tukey test (a:0,05). Failure mode of representative samples was analyzed by reflected light microscopy and SEM. Results: The SBS results of the five experimental groups were (MPa): A: 54.8(9.9), B: 50(7.9), C: 53.9(7.1), D: 54.9(9), E: 56.1(6.1) with no statistically significant difference (p>0,05). The shear strength of the control group was 88(12.5) MPa, significantly higher from all experimental groups (p<0,001). The failure analysis revealed a dominant mixed failure mode (adhesive-cohesive). Conclusions: There was no significant difference in bond strength of a fresh to aged composite for any silane drying times. All silane treatments resulted in lower strength that the shear cohesive strength of the fresh material.