Comparing the Shear Bond Strength of Composite to Dentin Utilizing Two Self-etching Primers

Objectives: This study evaluated the shear bond strength of two self-etching primers on dentin with two different smear layer preparation techniques and four different dentin pre-treatments. Methods: Eighty extracted molar teeth were cleaned of debris, roots embedded in resin, and occlusal surfaces ground to expose a flat dentin surface. Teeth were assigned to two smear layer groups prepared with either 60 or 600 grit sandpaper. Each group was further subdivided into four dentin pre-treatment sub groups: sub group one was treated with each self etching primer as per manufacturer’s instructions, the second, third and fourth subgroups were treated with 40% phosphoric acid for 5, 10, or 15 seconds prior to application of the self etching primer. One half of the surface of each tooth was treated with one of the two primer systems: Clearfil SE Bond (Kuraray Co.,LTD Osaka, Japan), or Prompt-L-Pop (ESPE, Seefeld/ Oberbayern Germany)(more aggressive primer). Composite cylinders were formed utilizing a bonding mold insert (Ultradent, South Jordan, UT), and bonded to halves of the prepared dentin surface (2 cylinders per tooth). Shear bond strengths of each cylinder were tested utilizing an MTS Bionix 200 testing platform after thermocycling and randomization at a crosshead speed of 1 mm/min. Data was analyzed with a three–way ANOVA for the factors bonding agent (Clearfill SE, Prompt-L-Pop), smear layer preparation (60, 600 grit sandpaper), and dentin treatment (0, 5, 10, 15 second etch). Results: Significant differences were found in the shear bond strengths between the primer systems (Clearfill SE 18.8 +/- 7.6 MPa, Prompt-L-Pop 6.9 +/- 5.2 MPa) at p<0.001. Other factors were statistically insignificant in this study. Conclusions: In this study, the reported aggressiveness of self-etching systems in penetrating the smear layer, regardless of the way it was prepared, was not found to be an indicator of shear bond strength.