title: Influence of Er:YAG laser irradiation distance on the bond strength of a restorative system to enamel.
abstract: OBJECTIVE
  The aim of the present study was to investigate in vitro the effect of Er:YAG laser on bonding to enamel, varying the irradiation distance.
  
  
  METHODS
  Tensile bond strength of an adhesive restorative system to non-irradiated and irradiated enamel surfaces was evaluated. Thirty caries-free human third molars were sectioned in mesio-distal direction and embedded in acrylic resin. Enamel was flattened, and a 3-mm-diameter bonding area was demarcated. Specimens were randomly assigned into six groups: groups I-V were treated with the Er:YAG laser (80 mJ/2 Hz), varying the irradiation distance (11, 12 mm-focused, 14, 16 and 17 mm, respectively), followed by 35% phosphoric acid etching. Control group (VI) received treatment with phosphoric acid alone. Single Bond adhesive system was applied on the conditioned enamel, and composite resin cones, bonded to enamel, were fabricated with Z250. After storage, samples were tested in tensile to failure (50 kgf and 0.5 mm/min).
  
  
  RESULTS
  Means in MPa were: I-9.67 (+/-3.44); II-13.29 (+/-2.65); III-13.33 (+/-2.22); IV-14.87 (+/-3.58); V-16.43 (+/-4.52); VI-22.90 (+/-3.03). ANOVA and Tukey test revealed statistically significant decrease of bond strength in group I (P < 0.05). Groups II-IV presented similar results, as did groups IV and V. Control group (VI) yielded the best overall performance (P < 0.05).
  
  
  CONCLUSIONS
  Er:YAG laser irradiation adversely affected adhesion to enamel. However, bond strength was influenced by the irradiation distance, thus being stronger with the increase of distance to the target tissue.
authors.affiliation: Faculdade de Odontologia de Ribeirão Preto/USP, Departamento de Odontologia Restauradora, Av. do Café, S/N Monte Alegre, Cep: 14040-904, Ribeirão Preto-SP, Brazil. dtchimello@yahoo.com.br
authors.forename: Daniela Thomazatti
authors.initials: DT
authors.lastname: Chimello-Sousa
authors.forename: Aline Evangelista
authors.initials: AE
authors.lastname: de Souza
authors.forename: Michelle Alexandra
authors.initials: MA
authors.lastname: Chinelatti
authors.forename: Jesus Djalma
authors.initials: JD
authors.lastname: Pécora
authors.forename: Regina Guenka
authors.initials: RG
authors.lastname: Palma-Dibb
authors.forename: Silmara Aparecida
authors.initials: SA
authors.lastname: Milori Corona
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000268:Adhesiveness / Q000528:radiation effects; D000535:Aluminum; D001840:Dental Bonding / Q000379:methods*; D003743:Dental Enamel / Q000528:radiation effects*; D017220:Dentin-Bonding Agents / Q000528:radiation effects*; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D010756:Phosphoric Acids / Q000008:administration & dosage; D013718:Tensile Strength; D015019:Yttrium
chemical_list: D017220:Dentin-Bonding Agents; D010756:Phosphoric Acids; C503779:yttrium-aluminum-garnet; D015019:Yttrium; D000535:Aluminum; C030242:phosphoric acid