title: Effect of Phosphoric Acid Pre-etching on Fatigue Limits of Self-etching Adhesives.
abstract: The purpose of this study was to use shear bond strength (SBS) and shear fatigue limit (SFL) testing to determine the effect of phosphoric acid pre-etching of enamel and dentin prior to application of self-etch adhesives for bonding resin composite to these substrates. Three self-etch adhesives--1) G- ænial Bond (GC Corporation, Tokyo, Japan); 2) OptiBond XTR (Kerr Corp, Orange, CA, USA); and 3) Scotchbond Universal (3M ESPE Dental Products, St Paul, MN, USA)--were used to bond Z100 Restorative resin composite to enamel and dentin surfaces. A stainless-steel metal ring with an inner diameter of 2.4 mm was used to bond the resin composite to flat-ground (4000 grit) tooth surfaces for determination of both SBS and SFL. Fifteen specimens each were used to determine initial SBS to human enamel/dentin, with and without pre-etching with a 35% phosphoric acid (Ultra-Etch, Ultradent Products Inc, South Jordan, UT, USA) for 15 seconds prior to the application of the adhesives. A staircase method of fatigue testing (25 specimens for each test) was then used to determine the SFL of resin composite bonded to enamel/dentin using a frequency of 10 Hz for 50,000 cycles or until failure occurred. A two-way analysis of variance and Tukey post hoc test were used for analysis of SBS data, and a modified t-test with Bonferroni correction was used for the SFL data. Scanning electron microscopy was used to examine the area of the bonded restorative/tooth interface. For all three adhesive systems, phosphoric acid pre-etching of enamel demonstrated significantly higher (p<0.05) SBS and SFL with pre-etching than it did without pre-etching. The SBS and SFL of dentin bonds decreased with phosphoric acid pre-etching. The SBS and SFL of bonds using phosphoric acid prior to application of self-etching adhesives clearly demonstrated different tendencies between enamel and dentin. The effect of using phosphoric acid, prior to the application of the self-etching adhesives, on SBS and SFL was dependent on the adhesive material and tooth substrate and should be carefully considered in clinical situations.
authors.forename: T
authors.initials: T
authors.lastname: Takamizawa
authors.forename: W W
authors.initials: WW
authors.lastname: Barkmeier
authors.forename: A
authors.initials: A
authors.lastname: Tsujimoto
authors.forename: D D
authors.initials: DD
authors.lastname: Scheidel
authors.forename: R L
authors.initials: RL
authors.lastname: Erickson
authors.forename: M A
authors.initials: MA
authors.lastname: Latta
authors.forename: M
authors.initials: M
authors.lastname: Miyazaki
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D001840:Dental Bonding / Q000379:methods; D003738:Dental Cements; D003743:Dental Enamel / Q000187:drug effects; D003799:Dental Stress Analysis; D003804:Dentin / Q000187:drug effects; D006801:Humans; D008422:Materials Testing; D010756:Phosphoric Acids / Q000494:pharmacology; D033081:Shear Strength
chemical_list: D003738:Dental Cements; D010756:Phosphoric Acids; C030242:phosphoric acid