Method: The occlusal enamel of fresh extracted human third molars was removed to expose the middle dentin. The specimens were randomly assigned into four groups namely, Group I total etch bonding system (Adper Single Bond 2/Filtek Supreme XT, ASB2/FSXT), Group II, two steps self-etch bonding system (Silorane System Adhesive/Filtek Silorane, SSA/FS), Group III two steps self etch bonding system (Adper SE Plus/Filtek Supreme XT, ASEP/FSXT) and Group IV one steps self etch bonding system (Easy Bond/ Filtek Supreme XT, EB/FSXT). Each group was further divided into two sub-groups according to the application time of the bonding agent (following manufacturer instructions and 30 sec more). The corresponding resin composite was applied in 4 increments of 0.5-1 mm thickness each to build resin composite stump of 3-4 mm height. Each increment was light polymerized for 20 seconds using LED at intensity 1000 mW/cm2. The specimens were stored in deionized water at 37 °C for 24 hrs. The specimens were cut into beams according to the non-trimming technique (n=20/group) with surface area of 0.81 mm2. The mTBS of the beams was tested using a microtensile device on a Universal testing machine at a cross-head speed of 1mm/min.
Result: Two-way ANOVA revealed a statistical significant difference in the two main effects, DBS (P=0.0024) and dwell time (P=0.0005). There was no statistical significant interaction between the two main effects (P=0.9257). The total etch DBS showed significant higher values than that of the one step self-etch DBS.
Conclusion: the application time for dentin bonding systems has a major role in achieving higher bond strength to dentin.