title: Effect of double-application of three single-step self-etch adhesives on dentin bonding and mechanical properties of resin-dentin area.
abstract: OBJECTIVE
  This study investigated whether double-application influences the bond strength of single-step self-etch adhesives and the mechanical properties of the resin-dentin area.
  
  
  METHODS
  Three single-step self-etch adhesives (EXL-683, experimental, 3M ESPE; Clearfil Tri-S Bond, Kuraray Medical; G BOND, GC) were applied on dentin surfaces by using the single-application or double-application method. The manufacturers' instructions stated use of the single-application method. Resin composite (Clearfil AP-X, shade A3, Kuraray Medical) was then placed and light cured for 40 seconds. The microshear bond test was carried out and the bond strength data were analyzed using one-way ANOVA with post hoc. The hardness (H) of the bonding layer, resin-dentin interface and dentin beneath the interface at depths of 10 microm and 100 microm were measured with a nanoindentation device (ENT-1100, Elionix). The H data were analyzed using two-way ANOVA, one-way ANOVA and the independent t-test at a significance level of alpha = 0.05.
  
  
  RESULTS
  The mean bond strength with single-applications of EXL-683, Clearfil Tri-S Bond and G BOND were 39.1, 36.9 and 30.0 MPa, respectively, while with the double-application, they were 46.9, 40.2 and 32.2 MPa. Double-application for EXL-683 to dentin showed significantly higher bond strength than single-application alpha < 0.05. However, there was no significant difference between the single- and double-application methods for the other two adhesives alpha > 0.05. The H of the bonding layer was significantly influenced by both the adhesive material and application method alpha < 0.001; the H of the bonding layer with a double-application was significantly improved compared to a single-application. The H of the resin-dentin interface was significantly affected by the application method alpha < 0.001, but not by the adhesive material (alpha > 0.05). Neither the H value of dentin at 10 microm nor a depth of 100 microm was affected by the adhesive material or application method (alpha > 0.05).
  
  
  CONCLUSIONS
  The double application of EXL-683 did improve the bond strength to dentin. The hardness of the bonding layer and resin-dentin interface was significantly affected by the double application for each material used.
authors: Tokyo Medical and Dental University, Cariology and Operative Dentistry, [corrected] Tokyo, Japan. weishenghua.ope@gmail.com
authors: Shenghua
authors: S
authors: Wei
authors: Yasushi
authors: Y
authors: Shimada
authors: Alireza
authors: A
authors: Sadr
authors: Junji
authors: J
authors: Tagami
mesh_terms: D045662:Dental Etching; D003799:Dental Stress Analysis; D003804:Dentin / Q000000981:diagnostic imaging; D006244:Hardness; D006801:Humans; D066298:In Vitro Techniques; D055115:Light-Curing of Dental Adhesives; D008689:Methacrylates; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements; D014463:Ultrasonography
chemical_list: C515604:Clearfil Tri-S Bond; C498353:G-Bond; D008689:Methacrylates; D019279:Resin Cements