title: Extension of a one-step self-etch adhesive into a multi-step adhesive.
abstract: One-step self-etch adhesives are undoubtedly the most user-friendly adhesives, but have been associated with lower bonding effectiveness as compared to two-step and three-step adhesives. Conversion of a one-step self-etch system into a two-step self-etch adhesive by adding a bonding step, or into a three-step etch&rinse adhesive by adding a beforehand etching step and a bonding step might be tempting in order to improve bond strength.
  
  
  OBJECTIVE
  The objective of this study was to investigate whether adding application steps influences the bond strength of a one-step self-etch adhesive.
  
  
  METHODS
  In this study, the bonding effectiveness of two experimental one-step self-etch adhesives and three different commercial adhesives to enamel and dentin was determined using a micro-tensile bond-strength protocol. This procedure was repeated for the experimental adhesives transformed into two-step self-etch and three-step etch&rinse adhesives. In addition, their interaction with tooth tissue was investigated using TEM and Feg-SEM.
  
  
  RESULTS
  Transforming a one-step into a two-step self-etch adhesive did improve the bond strength to enamel and dentin, though not significantly. By adding a preceding etching step, the bond strength to enamel was significantly improved, but that to dentin was decreased considerably. The latter must be attributed to hampered resin infiltration of the one-step self-etch adhesive within the relatively deeply exposed collagen fibril network.
  
  
  CONCLUSIONS
  Additional application of a hydrophobic bonding agent slightly improved bonding effectiveness. Adding a preceding etching step is beneficial for enamel but should be avoided for dentin as this will decrease bond strengths, and may even jeopardize the bonding durability.
authors.affiliation: Leuven BIOMAT Research Cluster, Department of Conservative Dentistry, School of Dentistry, Oral Pathology and Maxillo-Facial Surgery, Catholic University of Leuven, Kapucijnenvoer 7, B-3000 Leuven, Belgium.
authors.forename: K L
authors.initials: KL
authors.lastname: Van Landuyt
authors.forename: M
authors.initials: M
authors.lastname: Peumans
authors.forename: J
authors.initials: J
authors.lastname: De Munck
authors.forename: P
authors.initials: P
authors.lastname: Lambrechts
authors.forename: B
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D000096:Acetone / Q000737:chemistry; D000134:Acid Etching, Dental; D000269:Adhesives / Q000737:chemistry / Q000145:classification; D003094:Collagen / Q000648:ultrastructure; D001840:Dental Bonding / Q000379:methods*; D003743:Dental Enamel / Q000648:ultrastructure; D003804:Dentin / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000737:chemistry* / Q000145:classification; D000431:Ethanol / Q000737:chemistry; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D063065:Organophosphonates / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013718:Tensile Strength; D014233:Tricarboxylic Acids / Q000737:chemistry
chemical_list: D000269:Adhesives; C438313:Clearfil SE Bond; D017220:Dentin-Bonding Agents; D008689:Methacrylates; C469607:OptiBond FL; D063065:Organophosphonates; D019279:Resin Cements; C454540:Scotchbond etchant; D012997:Solvents; D014233:Tricarboxylic Acids; C407402:Unifil Bond; C477386:iBond; D000096:Acetone; D000431:Ethanol; C098756:4-methacryloxyethyltrimellitic acid; D003094:Collagen