Takamizawa T, Imai A, Hirokane E, Tsujimoto A, Barkmeier WW, Erickson RL, Latta MA, Miyazaki M. SEM observation of novel characteristic of the dentin bond interfaces of universal adhesives.
Dent Mater 2019;
35:1791-1804. [PMID:
31727447 DOI:
10.1016/j.dental.2019.10.006]
[Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 09/20/2019] [Accepted: 10/16/2019] [Indexed: 11/16/2022]
Abstract
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 ∼1-2μm, 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.
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