title: Shear bond strength to enamel of primary teeth irradiated with varying Er:YAG laser energies and SEM examination of the surface morphology: an in vitro study.
abstract: OBJECTIVE
  This study aimed to assess in vitro the influence of Er:YAG laser energy on the shear bond strength of a total-etch adhesive system to lased enamel of primary teeth, and to observe by SEM the morphological appearance of laser-ablated enamel surfaces.
  
  
  METHODS
  For the SBS test, primary canines were assigned to four groups (n = 12): a control (G1) and three groups irradiated with different Er:YAG laser energies- 60 mJ/2 Hz (G2), 80 mJ/2 Hz (G3), and 100 mJ/2 Hz (G4). In all groups, enamel surfaces were acidetched, Single Bond was applied, and resin cylinders were fabricated from Z250 resin. Bond strength was tested in shear (0.5 mm/min). For morphological analysis, 21 specimens were irradiated using the same energies, with or without acid-etching, and observed by SEM.
  
  
  RESULTS
  SBS means, in MPa, were: G1-14.28 (+/-3.24); G2-18.48 (+/-4.58); G3-17.82 (+/-4.38); G4-16.59 (+/-5.40). Overall, Er:YAG laser ablation of primary teeth enamel, prior to the adhesive protocol, influenced the shear bond strength. Bond strengths recorded after irradiation with energies of 60 and 80 mJ were statistically similar among them (p > 0.05), and both were superior to those yielded by the acid-etched control group (p < 0.05). No significant difference (p < 0.05) was found between bond strengths recorded for control specimens and those irradiated with 100 mJ. SEM analysis revealed that the increase of laser energy resulted in increasingly uneven and microroughened surfaces, regardless of acid-etching association.
  
  
  CONCLUSIONS
  The favorable results of the present study suggest that Er:YAG laser irradiation may be a viable approach for the preparation and treatment of primary teeth enamel prior to the placement of adhesive restorative systems.
authors.affiliation: Department of Pediatric Clinic, Preventive and Social Dentistry, University of São Paulo (USP), Ribeirão Preto-SP, Brazil.
authors.forename: Rosimeyri L
authors.initials: RL
authors.lastname: Wanderley
authors.forename: Elisângela M
authors.initials: EM
authors.lastname: Monghini
authors.forename: Jesus D
authors.initials: JD
authors.lastname: Pecora
authors.forename: Regina G
authors.initials: RG
authors.lastname: Palma-Dibb
authors.forename: Maria C
authors.initials: MC
authors.lastname: Borsatto
mesh_terms: D003743:Dental Enamel / Q000528:radiation effects* / Q000648:ultrastructure; D006801:Humans; D007834:Lasers; D008855:Microscopy, Electron, Scanning