title: Origin of interfacial droplets with one-step adhesives.
abstract: Contemporary one-step self-etch adhesives are often documented with interfacial droplets. The objective of this study was to research the origin of these droplets. Two HEMA-rich and one HEMA-free adhesive were applied to enamel and dentin, with the lining composite either immediately cured or cured only after 20 min. All one-step adhesives exhibited droplets at the interface; however, the droplets had two different origins. With the HEMA-free adhesives, droplets were located throughout the adhesive layer and were stable in number over time. With the HEMA-rich adhesives, the droplets were observed exclusively at the adhesive resin/composite interface, and their number increased significantly when the composite was delay-cured. Only the latter droplets caused a significant drop in bond strength after delayed curing. While the droplets in the HEMA-free one-step adhesives should be ascribed to phase separation, those observed with HEMA-rich adhesives resulted from water absorption from dentin through osmosis.
authors.affiliation: Leuven BIOMAT Research Cluster, Department of Conservative Dentistry, School of Dentistry, Oral Pathology and Maxillo-Facial Surgery, Catholic University of Leuven, B-3000 Leuven, Belgium.
authors.forename: K L
authors.initials: KL
authors.lastname: Van Landuyt
authors.forename: J
authors.initials: J
authors.lastname: Snauwaert
authors.forename: J
authors.initials: J
authors.lastname: De Munck
authors.forename: E
authors.initials: E
authors.lastname: Coutinho
authors.forename: A
authors.initials: A
authors.lastname: Poitevin
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshida
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.forename: P
authors.initials: P
authors.lastname: Lambrechts
authors.forename: B
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D000042:Absorption; D001840:Dental Bonding; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008964:Molar, Third; D009995:Osmosis; D044367:Phase Transition; D019279:Resin Cements / Q000737:chemistry*; D018709:Statistics, Nonparametric; D014867:Water
chemical_list: C505694:Clearfil S3 Bond; D017220:Dentin-Bonding Agents; C498353:G-Bond; D008689:Methacrylates; D019279:Resin Cements; D014867:Water; C005044:hydroxyethyl methacrylate