Incomplete infiltration of the demineralized collagen network may result in a weak zone within the hybrid layer and between the hybrid layer and dentin. The current study evaluates whether reducing the etching time to 5 s from the recommended 15 s or increasing it to 30 s has an effect on dentin bonding. 108 extracted molars were assigned to 3 bonding agent groups (n = 36): (a) Single Bond (SB), (b) One-Step (OS), and (c) Syntac Single Component (SSC). Each group was further divided into three subgroups (n = 12) of different etching times: 5, 15, and 30 s. All groups were bonded with Z100 composite resin according to the manufacturers instructions. All specimens were thermocycled 300 times between ± 5°C and ± 55°C, and shear bond strength testing and mode of failure analysis were performed. The bond strength of SB (5 s: 15.5 MPa ± 4.4; 15 s: 16.5 MPa ± 3.1; 30 s: 16.8 MPa ± 3.2) and OS (5 s: 13.7 MPa ± 1.8; 15 s: 12.4 MPa ± 3.8; 30 s: 10.6 MPa ± 3.8) showed no significant differences (p < 0.05) for the different etching times. For SSC, different etching times showed significant differences (5 s: 10.9 MPa ± 1.8; 15 s: 7.5 MPa ± 2.5; 30 s: 6.4 MPa ± 2.1). The mode of failure for SB and OS was adhesive or mixed adhesive/cohesive. For SSC, all failures were adhesive. Etching times of less than 15 s do not seem to adversely affect bonding to dentin.
Keywords: etching time, dentin, shear bond strength, adhesion, single-component adhesive systems, dental materials