Objectives: We wanted to evaluate how to optimize bond strength for the repair of Silorane composites. Different surface treatments were compared using the microtensile bond strength test. Methods: Silorane specimens were produced and aged by water-boiling for 24 h. The subsequent surface treatments were: no treatment, Silorane system adhesive bond (SSAB, 3M-ESPE), acetone, acetone+SSAB, silane, silane+SSAB. Another group made from Silorane without repair served as control. New Silorane was added to the specimens after surface treatment. More than 25 specimens per group were used. After another 24 h storage time half of the samples underwent thermo-mechanical fatigue simulation (FS) (2000 cycles, 5/55°C, 50000 mechanocycles: 50 N each). The microtensile bond strengths (MTS) were measured with beam-shaped sticks (1.0 x 1.0 x 10 mm) using a MTD-500 testing machine. Data were analyzed by one-way ANOVA and Scheffé's method (p=0.05).Results: The MTS data are summarized in the table as mean(standard dev)[MPa] without and with FS. The tensile strength of unrepaired Silorane (control group) was 54.7(6.5) MPa. The repair strength was always higher after FS but only for the group "Silane+SSAB" the difference was insignificant. Significant differences are visualized with different letters (capitals within a column, small letters within one row). SSAB and Silane+SSAB had the highest bond strength which achieved approximately 75 % of the unrepaired strength.
FS | No treatment | SSAB | Acetone | Acetone+SSAB | Silane | Silane+SSAB |
no | 17.1(11.1)A,a | 31.8(11.4)A,b,c | 26.4(12.2)A,b | 31.0(9.6)A,b | 28.4(12.0)A,b | 39.8(10.8)A,c |
yes | 38.8(14.5)B,a | 41.5(13.7)B,a | 38.2(11.2)B,a | 38.8(9.4) B,a | 38.2(7.7) B,a | 41.3(11.4)A,a |
Conclusion: An ongoing polymerization could explain the improved bond strength values after FS (= longer time before testing). SSAB improved the initial bond values but after FS the differences between all groups were insignificant. It seems that the influence of the post curing time on repair strength with Silorane material is higher than FS or surface treatment.