One- vs. Two-Step Self-Etch Application Mode on Bond Strength

Objectives: to evaluate the effects of application mode and storage time on the microtensile bond strength (µTBS) of a self-etch adhesive (SEA) that can be applied as 1-step or 2-step modes.  Methods: Dentin surfaces from human teeth were exposed flat and polished on wet 320-grit sandpaper for 30s.  All Bond SE (ABSE) (Bisco) was applied according to manufacturer's instructions with or without the optional liner (HIX).  Light Core Blue composite (Bisco) was built-up and cured 40s each 1-2 mm increment.  Teeth were cut into 0.8mmX0.8mm beams and randomly distributed among selected time intervals and stored either in water (H₂O) or in mineral oil (Oil) at 37^◦C.  Specimens were tested until failure using Microtensile Tester (Bisco) at 0.5mm/min.  Averages below include all specimens regardless of fracture pattern.  Data was analyzed by 2-way ANOVA for each storage media (p³0.05).  Results: MPa (SD).

Storage Media	24 Hrs	3 Months	6 Months
ABSE/H2O	34.9(11.6) N=21 Aa	61.1(9.1) N=18 Bb	40.2(9.2) N=18 Aa
ABSE/Oil	45.4(12.6) N=15 Ab	60.6(13.1) N=17 Bb	63.5(14.1) N=17 Bb
ABSE+HIX/ H2O	49.6(8.1) N=19   Ab	38.3(8.1) N=16 Ba	58.5(12.2) N=16 Cb
ABSE+HIX/Oil	49.0(11.0) N=14 Ab	61.9(13.5) N=15 Bb	74.8(10.4) N=14 Cc

[Capital letters compare rows and lower cases compare columns.]

The use of two-step application mode significantly improved bond strength. Bond strength was significantly higher at 6 months storage when two-step mode was used. Conclusions: Improved bond strengths were obtained with the 2-step application mode at 6 months in water.  As expected, there was a trend in increasing bond strength for specimens stored in mineral oil.