Purpose: The purpose of this study was to evaluate the effect of incorporation of
different concentrations of hydroxyapatite nanorods into two adhesives of two commercial
adhesive systems in order to evaluate the effect on rheological properties, microshear
bond strength and degree of conversion. Materials and Methods: One hundred
twenty specimens were used in the present study. The specimens were divided into two
main groups (n=60) according to the type of commercial adhesive used AdheSE Bond
(I) and Tetric-N Bond Universal (II). Then each group was subdivided into 4 subgroups
(n=15) according to the concentration of incorporated HAp nanorods 0( control), 0.2,
2, 10wt%HAp nanorods (A, B, C and D, respectively). Each subgroup was further
divided into 3 divisions according to the type of test performed (n=5). For rheological
properties measurements, a rheometer was used to measure the viscosity and the
viscoelastic behavior of the adhesives. For microshear bond strength testing (μSBS),
the specimens were tested by using a universal testing machine. The type of failure
was determined by using scanning electron microscope. The degree of conversion was
measured using Fourier Transform Infrared (FTIR) spectroscopy. The data were analyzed
using one-way analysis of variance (ANOVA) and Tukey's post hoc significance
difference tests. Differences were considered significant at p≤0.05. Two ways analysis
of variance ANOVA test was used to study the statistical significance of the interaction
between variables (material and HAp nanorods concentrations). Results: The viscosity
of experimental adhesives increased gradually with increasing the concentrations of
HAp nanorods. In μSBS test, the AdheSE containing 0.2 and 2wt.% HAp nanorods produced
significantly the highest values. Regarding degree of conversion (DC), Tetric-N
Bond containing 10wt.% HAp nanorods produced significantly the highest value of
DC. Conclusion: Incorporation of HAp nanorods with low concentration (0.2wt %) in
AdheSE Bond had a positive impact on the bond strength. However, HAp nanorods as
fillers were not suitable to be incorporated in Tetric-N Bond.