title: Effect of double-layer application on dentin bond durability of one-step self-etch adhesives.
abstract: OBJECTIVE
  The aim of this in vitro study was 1) to analyze the influence of a double-layer application technique of four one-step self-etch adhesive systems on dentin and 2) to determine its effect on the stability of the adhesive interfaces stored under different conditions.
  
  
  METHODS
  Four different one-step self-etch adhesives were selected for the study (iBondSE, Clearfil S(3) Bond, XenoV(+), and Scotchbond Universal). Adhesives were applied according to manufacturers' instructions or with a double-layer application technique (without light curing of the first layer). After bonding, resin-dentin specimens were sectioned for microtensile bond strength testing in accordance with the nontrimming technique and divided into 3 subgroups of storage: a) 24 hours (immediate bond strength, T0), b) six months (T6) in artificial saliva at 37°C, or c) five hours in 10 % NaOCl at room temperature. After storage, specimens were stressed to failure. Fracture mode was assessed under a light microscope.
  
  
  RESULTS
  At T0, iBond SE showed a significant increase in microtensile bond strength when the double-application technique was applied. All adhesive systems showed reduced bond strengths after six months of storage in artificial saliva and after storage in 10% NaOCl for five hours; however at T6, iBond SE, Clearfil S(3) Bond, and XenoV(+) showed significantly higher microtensile bond strength results for the double-application technique compared with the single-application technique. Scotchbond Universal showed no difference between single- or double-application, irrespective of the storage conditions.
  
  
  CONCLUSIONS
  The results of this study show that improvements in bond strength of one-step self-etch adhesives by using the double-application technique are adhesive dependent.
authors.forename: M
authors.initials: M
authors.lastname: Taschner
authors.forename: M
authors.initials: M
authors.lastname: Kümmerling
authors.forename: U
authors.initials: U
authors.lastname: Lohbauer
authors.forename: L
authors.initials: L
authors.lastname: Breschi
authors.forename: A
authors.initials: A
authors.lastname: Petschelt
authors.forename: R
authors.initials: R
authors.lastname: Frankenberger
mesh_terms: D000269:Adhesives; D001840:Dental Bonding / Q000379:methods*; D003804:Dentin; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning
chemical_list: D000269:Adhesives