Effects of ethanol concentrations of acrylate‑based dental adhesives on microtensile composite‑dentin bond strength and hybrid layer structure of a 10 wt% polyhedral oligomeric silsesquioxane (POSS)‑incorporated bonding agent

Seyed Mostafa Mousavinasab, Mohammad Atai, Mehrdad Barekatain, Parisa Fattahi, Amir Fattahi, Vahid Rakhshan


Background: The aim of this study was to assess for the first time the effects of different amounts
of ethanol solvent on the microtensile bond strength of composite bonded to dentin using a
polyhedral oligomeric silsesquioxane (POSS)‑incorporated adhesive.
Materials and Methods: This experimental study was performed on 120 specimens divided into
six groups (in accordance with the ISO TR11405 standard requiring at least 15 specimens per group).
Occlusal dentin of thirty human molar teeth was exposed by removing its enamel. Five teeth were
assigned to each of six groups and were converted to 20 microtensile rods (with square cross‑sections of
1 mm × 1 mm) per group. The “Prime and Bond NT” (as a common commercial adhesive) was used
as the control group. Experimental acrylate‑based bonding agents containing 10 wt% POSS were
produced with five concentrations of ethanol as solvent (0, 20, 31, 39, and 46 wt%). After application of
adhesives on dentin surface, composite cylinders (height = 6 mm) were bonded to dentin surface. The
microtensile bond strength of composite to dentin was measured. The fractured surfaces of specimens
were evaluated under a scanning electron microscope to assess the morphology of hybrid layer. Data
were analyzed using one‑sample t‑test, one‑way analysis of variance (ANOVA), and Tukey tests (α = 0.05).
Results: the mean bond strength in the groups: “control, ethanol‑free, and 20%, 31%, 39%, and
46% ethanol” was, respectively, 46.5 ± 5.6, 29.4 ± 5.7, 33.6 ± 4.1, 59.0 ± 5.5, 41.9 ± 6.2, and
18.7 ± 4.6 MPa. Overall difference was significant (ANOVA, P < 0.0001). Pairwise differences were
all significant (Tukey P < 0.05) except those of “ethanol 0% versus 20%” and “20% versus 31%.” All
groups except “0% and 46% ethanol” had bond strengths above 30 MPa (t‑test P < 0.05).
Conclusion: Incorporation of 31% ethanol as solvent into a 10 wt% POSS‑incorporated
experimental dental adhesive might increase the bond strength of composite to dentin and improve
the quality and morphology of the hybrid layer. However, higher concentrations of the solvent might
not improve the bond strength or quality of the hybrid layer.
Key Words: Dental adhesive, bond strength, polyhedral oligomeric silsesquioxanes, solvent,

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