title: Influence of oxygen-inhibited layer on dentin bond strength of chemical-cured resin composite.
abstract: This study evaluated the influence of an oxygen-inhibited layer on the surface free energies of three single-step self-etch adhesives and on the bond strength of chemical-cured resin. Adhesives were applied to bovine dentin and light irradiated, and the oxygen-inhibited layer was either retained or removed. Surface free energies were determined by measuring the contact angles of test liquids placed on the cured adhesives. Dentin bond strengths of chemical-cured resin with and without the oxygen-inhibited layer were measured. Ultrastructural observation of the restorative-dentin interface was made by scanning electron microscopy. For all surfaces, values of the estimated surface tension component, Lifshitz-Van der Waals force (γS(LW)), were relatively constant. Values for the Lewis acid (γS(+)) component increased slightly when the oxygen-inhibited layer was removed, whereas those of the Lewis base (γS(-)) component decreased significantly. The bond strength of the chemical-cured resin composite was significantly higher in specimens without an oxygen-inhibited layer (7.6-8.0 MPa) than in those with an oxygen-inhibited layer (4.8-5.2 MPa). Small gaps between adhesive and resin composite were found for the group with an oxygen-inhibited layer. These results indicate that the absence of an oxygen-inhibited layer in single-step self-etch adhesives promotes higher dentin bond strength of the chemical-cured resin.
authors.affiliation: Department of Operative Dentistry, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Yamaji
authors.forename: Kensaku
authors.initials: K
authors.lastname: Koga
authors.forename: Akimasa
authors.initials: A
authors.lastname: Tsujimoto
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Keishi
authors.initials: K
authors.lastname: Tsubota
authors.forename: Toshiki
authors.initials: T
authors.lastname: Takamizawa
authors.forename: Masashi
authors.initials: M
authors.lastname: Miyazaki
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D003799:Dental Stress Analysis; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010100:Oxygen / Q000737:chemistry*; D033081:Shear Strength; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; D010100:Oxygen
keywords: chemical-cured resin; dentin bond strength; oxygen-inhibited layer; self-etch adhesive; surface free-energy