title: Ultramorphological evaluation of the dentin acid-base resistant zone of two-step self-etching systems after long-term storage in water.
abstract: OBJECTIVE
  To evaluate the morphological changes in the acid-base resistant zone (ABRZ) at the resin/dentin interface after long-term storage in water.
  
  
  METHODS
  Two-step self-etching adhesive systems, Clearfil SE Bond (SE) and Clearfil Protect Bond (PB) (Kuraray Medical) were used. Human dentin disk sandwiches with resin composite were prepared, sectioned, and embedded in epoxy resin. The specimens were stored in water for 1 day, 1, 3 or 6 months, and then subjected to demineralizing solution and 5% NaOCl. The specimens were finally sectioned again, polished, argon-ion etched, and observed with SEM.
  
  
  RESULTS
  The outer lesion (OL) thickness at 1 day ranged from 10 to 15 µm but increased to approximately 30 µm after 6 months, suggesting gradual loss of dentin stored in water. A lower electron density was noted in the adhesives at the locations that were exposed to water. The ABRZs were observed clearly in all groups; the thickness of the ABRZ at the mid-point of the OL gradually decreased with time for SE. For PB, the thickness was stable up to 1 month, but decreased after 3 months. The bottom of the ABRZ in SE formed a right angle with dentin; in contrast, in PB, it sloped down toward dentin with a broadening bottom.
  
  
  CONCLUSIONS
  Water storage resulted in changes both in the dentin substrate and the adhesive layer. An ABRZ was observed beneath the hybrid layer after long-term storage in water in both SE and PB. The ABRZ was thicker and relatively more stable in PB, probably due to fluoride release.
authors.affiliation: Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School, Tokyo Medicial and Dental University, Tokyo, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ichikawa
authors.forename: Toru
authors.initials: T
authors.lastname: Nikaido
authors.forename: Go
authors.initials: G
authors.lastname: Inoue
authors.forename: Alireza
authors.initials: A
authors.lastname: Sadr
authors.forename: Junji
authors.initials: J
authors.lastname: Tagami
mesh_terms: D001840:Dental Bonding; D003804:Dentin / Q000737:chemistry* / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D004356:Drug Storage; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008855:Microscopy, Electron, Scanning; D012044:Regression Analysis; D019279:Resin Cements / Q000737:chemistry*; D013997:Time Factors
chemical_list: C503075:Clearfil Protect Bond; C438313:Clearfil SE Bond; D017220:Dentin-Bonding Agents; D019279:Resin Cements