Effect of post-silanization drying on the bond strength of composite to ceramic.

Abstract

The temperature reported for thermally treating silanated ceramics to improve composite-ceramic bonding is often too high for chairside applications. This study investigated whether post-silanization drying with a stream of warm air could enhance the composite/ceramic tensile bond. Thirty-two ceramic blocks (6 x 6 x 9 mm), 16 of each ceramic, were fabricated and divided into 8 subgroups using 4 roughening procedures and 2 silanization protocols per ceramic (Eris and IPS Empress). Roughening included polishing to 1200 grit as control (P), airborne-particle abrasion (A), hydrofluoric acid etching (E), or a combination of abrasion and etching (AE). Silanated surfaces were dried with room-temperature air (SR) or 45+/-5 degrees C warm air (SH). An adhesive (Heliobond) was applied and light-polymerized before adding composite (Tetric Ceram). Thirty-three specimens (0.9 x 0.9 x 18 mm) were cut from a pair of blocks and stored in 37 degrees C distilled-water for 3 weeks. Each specimen was loaded under tension until failure in a universal testing machine (n=33). Strength (MPa) was calculated by dividing the failure load by the cross-sectional area. Mode of failure was investigated with scanning electron microscopy (SEM). Statistical analyses were performed with ANOVA and the Tukey HSD test (alpha=.05). The mean tensile bond strength values (SD) in MPa for P, A, E, and AE procedures were, respectively, 11.4 (5.4), 11.9 (5.4), 9.9 (2.6), and 15.8 (4.3) for Eris/SR; 17.8 (6.2), 20.4 (7.1), 18.0 (6.7), and 18.8 (3.9) for Eris/SH; 9.3 (2.8), 14.0 (4.0) 17.1 (3.7), and 23.2 (6.8) for IPS-Empress/SR; and 14.8 (4.5) 22.6 (4.8), 22.7 (5.0), and 28.7 (4.4) for IPS Empress/SH. ANOVA indicated the influence of ceramic material, roughening, and postsilanization drying was significant (P<.0001). The Tukey HSD test showed mean strength values higher for IPS Empress than for Eris, SH greater than SR, and AE producing the highest mean strength values. SEM examination showed there were greater areas of cohesive failure with SH specimens. Silane drying by a stream of warm air was effective in enhancing tensile bond strength of composite to ceramic.