title: Acid etching concentration as a strategy to improve the adhesive performance on Er:YAG laser and bur-prepared demineralized enamel.
abstract: OBJECTIVE
  This study investigated the effect of phosphoric acid concentration on microshear bond strength (μSBS) of an etch-and-rinse adhesive system to demineralized irradiated enamel.
  
  
  BACKGROUND
  Er:YAG laser irradiation may increase acid resistance of enamel; however, its use is associated with reduced bonding effectiveness.
  
  
  METHODS
  Three experimental etching agents and one bonding agent were fabricated. Enamel pretreatment was tested in two levels (bur and laser) and phosphoric acid was tested in four levels (control and at 35, 45, or 55%). Commercially available phosphoric acid and a bonding agent were used as control. Enamel samples were submitted to a pH-cycling model to induce demineralization. Half of the exposed demineralized enamel area was prepared with diamond bur and half was prepared with an Er:YAG laser (λ=2.94 μm, 300 mJ, 2 Hz). Specimens were randomly allocated to receive different acid etching concentrations and either the experimental or the commercial adhesive system. Microshear bond strength and the adhesive remnant index (ARI) scores were determined. μSBS's data were evaluated by two way analysis of variance (ANOVA) and Tukey's test. Kruskal-Wallis followed by Dunn's method and Mann-Whitney test were used for ARI comparisons (α=5%).
  
  
  RESULTS
  For μSBS, no significant difference among the groups was found, either for phosphoric acid concentration or surface preparation. For ARI scores, statistically higher resin retention was found for lased groups (p<0.001).
  
  
  CONCLUSIONS
  The increase of phosphoric acid concentration did not impair bond strength regardless of surface preparation; however, increased retention was found when demineralized enamel was prepared with laser.
authors.affiliation: 1 Faculty of Pharmacy, Dentistry, and Nursing, Federal University of Ceará , Rodolfo Teófilo, Brazil .
authors.forename: Sarah F F
authors.initials: SF
authors.lastname: Guedes
authors.forename: Mary Anne S
authors.initials: MA
authors.lastname: Melo
authors.forename: Juliana P M
authors.initials: JP
authors.lastname: Lima
authors.forename: Caroline
authors.initials: C
authors.lastname: Ely
authors.forename: Antero J S
authors.initials: AJ
authors.lastname: Rôla
authors.forename: Evandro
authors.initials: E
authors.lastname: Piva
authors.forename: Lidiany K A
authors.initials: LK
authors.lastname: Rodrigues
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000269:Adhesives; D001840:Dental Bonding; D003743:Dental Enamel; D017220:Dentin-Bonding Agents; D005782:Gels; D006801:Humans; D066298:In Vitro Techniques; D053844:Lasers, Solid-State; D010756:Phosphoric Acids / Q000008:administration & dosage*
chemical_list: D000269:Adhesives; D017220:Dentin-Bonding Agents; D005782:Gels; D010756:Phosphoric Acids; C030242:phosphoric acid