Shear Bond-Strength of Modern Self-etched adhesives to Immediate-pretreated Teeth

Objectives: One of the major concerns with composite restorations is their ability to achieve effective initial bonding (Dent Mater 2006; 22: 875-883). The purpose of this study was to evaluate pre-treating time, 1, 2-seconds versus 20-seconds to teeth on the shear bond-strength (SBS) of composite restorations (Clearfil AP-X, Kuraray Noritake), pretreated with six self-etched adhesives (SEA, one-step): Prime & Bond elect, Dentsply/Caulk (PB); Scotchbond Universal, 3M ESPE (SU); OptiBond All-In-One, Kerr (OA); Adhese Universal, Ivoclar Vivadent (AU); G-Premio Bond, GC (GP); BeautiBond Multi, Shofu (BM); Clearfil SE Bond 2, Kuraray Noritake (SE2, two-step).
Methods: The surface of polished enamel and dentin (# 600) was pretreated as described above (1, 2 sec. versus 20 sec.). A Teflon mold with a cylindrical hole (diameter, 3.6 mm; height, 2 mm) was clamped onto the enamel and dentin surfaces and was filled with Clearfil AP-X. SBS were measured after one-day storage in water (37 ^oC). Statistical analyses were performed by t-Test (1, 2-sec. versus 20-sec, p=0.05, S: Significantly different, NS: Not significantly different).
Results: Summary: (SBS, Mean (S.D.), MPa, Number of tooth fractures, n=10)
PB SU OA AU GP BM SE2
To Enamel
1, 2-sec.: 17.6(2.8) 18.4(4.4) 16.2(4.2) 25.3(6.2) 24.5(4.8) 18.9(3.3) 25.8(4.0)
S S S NS NS S S
20-sec.: 22.1(4.3) 25.0(5.2) 24.1(5.4) 25.7(4.2) 25.0(3.9) 28.4(3.3) 39.4(2.8)

To Dentin
1, 2-sec.: 19.2(5.3) 24.2(4.6) 26.0(4.9) 25.8(5.2) 27.4(6.6) 24.7(4.7) 31.6(4.2)
S NS NS S NS S S
20-sec.: 29.2(5.4) 27.1(4.2) 29.1(5.1) 33.5(4.6) 27.6(4.9) 30.7(4.0) 37.9(3.6)
Conclusions: SBSs of all SEAs to tooth pretreated by 20-sec were significantly greater than 1, 2-seconds groups, except GP. The immediate-pretreating procedure is not an advisable procedure to enhance bonding ability.