Bond Strength of Nanohybrid Composite to the Engineered Dentin Surface

Objectives: Evaluate affinity of a phage display derived peptide and a phosphorylated variant for apatite-based tissues using shear bond strength and surface adsorptions tests.
Methods: Forty fresh dentin specimens were randomized into four groups according to the type of peptide used (phosphorylated VTK vs non-phosphorylated) and application time (1 min. vs 10 min). Teeth were sectioned and mounted in PVC pipe rings, leaving the coronal dentin surface exposed. Dentin was etched for 15 seconds, rinsed and dried. 1mg crushed dentin and enamel was placed in filter plates and exposed to 250mL of peptide in solution (200mg/mL) for 3h. Filter plate was spun down and concentration measured using UV absorbance (l=205nm). This oligopeptides in 1mg solution were applied with a microbrush to the etched dentin and observed for 1 min or 10 min. An ultradent mold, 2.379 X 4 mm was placed over the exposed surface, bonding agent applied and light-polymerized for 20s. A nanohybrid composite was packed into the mold and light-polymerized for 20 seconds, with a Bluephase (G2) light. After 24 hours storage, specimens were placed in the bisco testing device with bonded surface parallel to the loading plane. Shear test to failure was performed and mean force was calculated in MPa.
Results: VTK adsorbed to dentin and enamel with a lower affinity than phosphorylated-VTK (11.3 and 28.1 nmol/mm2 vs 81.9 and 142.6 nmol/mm2 respectively). Shear bond strengths with peptide were lower than controls but not significantly different. There was no significant difference in bond strengths between phosphorylated and non-phosphorylated VTK at 1 min (19.96 MPa vs 18.08) or 10 min (17.86 MPa vs 16.8), p > 0.05.
Conclusions: Phosphorylated VTK had greater adsorption for dentin and enamel but shear bond strength to dentin was not enhanced with application of the phosphorylated peptide at either time point.