Objectives: The study compared the effect of retraction pastes [CoSP2 (C, 3M ESPE), Expasyl (E, Kerr Corp.)] without rinsing and with rinsing for three different time periods on the bond strength of self-adhesive resin cements [RelyX Unicem Clicker (RX, 3M ESPE), Maxcem Elite (ME, Kerr Corp.)] on human superficial dentin. Methods: Specimens of 600-grit ground dentin were prepared (8/condition/cement/paste) without application of retraction paste (control) or with retraction paste (2 min residence time), which was then lightly dry wiped off the surface (0 sec) or rinsed for 5, 10, or 20 sec with clean water. Composite cylinders (Z250, 3M ESPE), 2.38 mm diameter, were fabricated using an Ultradent mold on top of mylar film and then micro-etched using 50 μm alumina. The cylinders were cemented to the dentin substrate and cement was cured with an LED curing light (Demi, Kerr Corp.) per manufacturer's instructions. The Ultradent shear strength was determined in an universal test machine (Instron 5866) at 1.0 mm/min. Data were analyzed statistically using analysis of variance and Fisher's PLSD at the 0.05 level of significance. Results: Means and standard deviations are shown in table.
Rinsing Time
Cement/Paste Control 0 sec 5 sec 10 sec 20 sec
RX/C 17.6(6.7) 12.4(3.9) 11.5(8.8) 10.4(4.0) 13.3(2.3)
ME/C 5.7(1.3) 13.7(3.7) 8.8(1.9) 6.4(1.3) 9.2(4.3)
RX/E 17.8(3.9) 9.1(3.2) 5.8(1.7) 6.3(1.7) 5.8(1.2)
ME/E 4.8(1.3) 8.1(2.4) 4.2(0.7) 4.8(1.3) 3.8(1.1)
Conclusions: Rinse time did not affect bond strength statistically. The bond strength of cement RX decreased when retraction paste was used. With respect to RX, paste E reduced bond strength significantly more than paste C. The bond strength of cement ME improved somewhat when placed on dentin that has been exposed to paste C both in the rinsed and unrinsed conditions. Project was funded in part by 3M ESPE.