title: Effect of phosphoric acid etching on the shear bond strength of two self-etch adhesives.
abstract: OBJECTIVE
  To evaluate the effect of optional phosphoric acid etching on the shear bond strength (SBS) of two self-etch adhesives to enamel and dentin.
  
  
  METHODS
  Ninety-six bovine mandibular incisors were ground flat to obtain enamel and dentin substrates. A two-step self-etch adhesive (FL-Bond II) and a one-step self-etch adhesive (BeautiBond) were applied with and without a preliminary acid etching to both the enamel and dentin. The specimens were equally and randomly assigned to 4 groups per substrate (n=12) as follows: FL-Bond II etched; FL-Bond II un-etched; BeautiBond etched; BeautiBond un-etched. Composite cylinders (Filtek Z100) were bonded onto the treated tooth structure. The shear bond strength was evaluated after 24 hours of storage (37°C, 100% humidity) with a testing machine (Ultra-tester) at a speed of 1 mm/min. The data was analyzed using a two-way ANOVA and post-hoc Tukey's test with a significance level of p<0.05. A field emission scanning electron microscope was used for the failure mode analysis.
  
  
  RESULTS
  Both adhesives evidenced a significant decrease in the dentin SBS with the use of an optional phosphoric acid-etching step (p<0.05). Preliminary phosphoric acid etching yielded significantly higher enamel SBS for FL-Bond II (p<0.05) only, but not for BeautiBond. FL-Bond II applied to un-etched dentin demonstrated the highest mean bond strength (37.7±3.2 MPa) and BeautiBond applied to etched dentin showed the lowest mean bond strength (18.3±6.7 MPa) among all tested groups (p<0.05).
  
  
  CONCLUSIONS
  The use of a preliminary acid-etching step with 37.5% phosphoric acid had a significant adverse effect on the dentin bond strength of the self-etch adhesives evaluated while providing improvement on the enamel bond strength only for FL-Bond II. This suggests that the potential benefit that may be derived from an additional etching step with phosphoric acid does not justify the risk of adversely affecting the bond strength to dentin.
authors.affiliation: SUNY at Buffalo, School of Dental Medicine Department of Restorative Dentistry, Buffalo, NY, USA. cs252@buffalo.edu
authors.forename: Camila
authors.initials: C
authors.lastname: Sabatini
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D000818:Animals; D002417:Cattle; D001840:Dental Bonding / Q000379:methods; D003743:Dental Enamel / Q000187:drug effects*; D019232:Dental Restoration Failure; D003804:Dentin / Q000187:drug effects*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids / Q000009:adverse effects / Q000737:chemistry*; D033081:Shear Strength; D013499:Surface Properties
chemical_list: D017220:Dentin-Bonding Agents; D010756:Phosphoric Acids; C030242:phosphoric acid
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