Nano-Layering Adds Strength to the Adhesive Interface

Kumiko Yoshihara, N. Nagaoka, A. Nakamura, T. Hara, Y. Yoshida, B. Van Meerbeek

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)


X-ray diffraction (XRD) surface analysis and ultrastructural interfacial characterization using transmission electron microscopy (TEM) confirmed that the functional monomer 10–methacryloyloxydecyl dihydrogen phosphate (10-MDP) self-assembles into nano-layers at adhesive-tooth interfaces. Self-assembled nano-layering is thought to contribute to the durability of bonding to tooth dentin, although this has not been proven yet. In order to disclose this potential bond-durability contribution of nano-layering, we observed the 3-dimensional (3D) spreading of nano-layering by a series of focused-ion-beam (FIB) milled cross sections by scanning electron microscopy (FIB-SEM) and examined the mechanical properties of self-assembled nano-layering using scanning probe microscopy (SPM). A commercial 10-MDP-containing 3-step self-etch adhesive partially demineralized dentin up to submicron depth, forming a submicron hydroxyapatite-rich hybrid layer. TEM chemically and ultrastructurally confirmed the formation of interfacial nano-layering. FIB-SEM 3D reconstructions disclosed a 3D network of self-assembled nano-layering extending from the hybrid layer up to within the adjacent adhesive-resin layer. SPM revealed that nano-layering within the adhesive-resin layer possessed a higher elastic modulus than that of the surrounding adhesive resin, hereby suggesting that nano-layering contributes to the mechanical strength of adhesives like filler particles do. Nano-layering’s 3D expanded structure is expected to strengthen the surrounding resin, as well to better interconnect the adhesive-resin layer to the hybrid layer. In conclusion, this exploratory study demonstrated that nano-layering constitutes a strong phase at the adhesive interface, which may contribute to the clinical longevity of the 10-MDP-based bond to dentin.

Original languageEnglish
Pages (from-to)515-521
Number of pages7
JournalJournal of dental research
Issue number5
Publication statusPublished - May 2021


  • adhesives
  • dental materials
  • dentin
  • electron microscopy
  • microscopy
  • nanostructures

ASJC Scopus subject areas

  • Dentistry(all)


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