SEM observation of novel characteristic of the dentin bond interfaces of universal adhesives

Toshiki Takamizawa, Arisa Imai, Eizo Hirokane, Akimasa Tsujimoto, Wayne W. Barkmeier, Robert L. Erickson, Mark A. Latta, Masashi Miyazaki

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Objective: The aim of this study was to observe the resin/dentin interfaces of universal adhesives by using scanning electron microscopy (SEM), and to compare their morphologies with conventional etch & rinse (ER) and self-etch (SE) adhesive systems. Methods: Two three-step and one two-step ER adhesives and two two-step and two single-step SE adhesives were used for comparison with seven universal adhesives in ER mode and SE mode, respectively. Bonded surfaces with bovine teeth were longitudinally sectioned and mirror-polished. Half of the samples were treated with HCl and NaOCl solutions. The interfaces were subjected to argon ion beam etching and then observed by scanning electron microscopy. Results: The thickness of the adhesive layer (AL) of most of the seven universal adhesives and single-step SE adhesives was similar. Universal adhesives in SE mode formed a hybrid smear layer as a high-density zone between the AL and dentin. The thickness of the hybrid layer (HL) of the universal adhesives in ER mode was ∼1–2 μm, with a high-density zone (reaction layer [RL]) below the HL. Conclusion: The morphological features of most universal adhesives in SE mode and single-step SE adhesives are similar. Although resin–dentin interfaces of universal adhesives in ER mode resemble those of ER adhesives, universal adhesives have a distinctive feature, an RL. Significance: The RL might be a sign of chemical bonding even when using universal adhesives in ER mode.

Original languageEnglish (US)
Pages (from-to)1791-1804
Number of pages14
JournalDental Materials
Issue number12
StatePublished - Dec 2019

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Dentistry(all)
  • Mechanics of Materials


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