Influence of adhesive application duration on dentin bond strength of single-application bonding systems

This study examined the relationship between the bond agent application duration and the dentin bond strength of several single-application bonding systems. The restorative material/bonding systems used were Reactmer, with its single-application bonding system Reactmer Bond (RB, Shofu Inc, Kyoto, Japan); Palfique Estelite, with its single-application bonding system One-Up Bond F (OU, Tokuyama Co, Tokyo, Japan) and F2000 Compomer, with its bonding system Primer/Adhesive in Clicker (F2, 3M Dental Products, St Paul, MN 55144, USA). Bovine mandibular incisors were mounted in self-curing resin and wet ground with #600 SiC to expose labial dentin. Adhesives were applied for 5, 10, 20, 30 and 60 seconds, and restorative materials were condensed into a Teflon mold (O4 x 2 mm) on the dentin and light activated. Fifteen samples per test group were stored in 37degreesC water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/min. One-way ANOVA followed by Duncan test (p=0.05) was done. SEM observations of the treated dentin surface were also conducted. The dentin bond strength ranged from 6.9+/-2.4 to 11.2+/-2.8 MPa for RB, 8.9+/-2.2 to 12.2+/-1.9 MPa for OU, and 7.8+/-3.1 to 11.4+/-2.6 MPa for F2. No significant differences were found among the 10-60 second application duration groups for the systems used. From the SEM observations, demineralization of the dentin surface was more pronounced with longer application duration. The data suggest that the duration of single-application bonding systems was not a crucial factor for determining dentin bond strength, even though morphological changes were observed on the dentin surface.