title: Effect of erbium-doped yttrium aluminium garnet laser parameters on ablation capacity and morphology of primary dentin.
abstract: OBJECTIVE
  To evaluate the ablation capacity of different energies and pulse repetition rates of an erbium-doped yttrium aluminium garnet (Er:YAG) laser on primary dentin by assessing mass loss and to analyze the surface morphology using scanning electron microscopy (SEM).
  
  
  BACKGROUND
  Previous studies have demonstrated the ability of the Er:YAG laser to ablate dentin substrate.
  
  
  METHODS
  Forty-eight sound primary molars were bisected in the mesiodistal direction. The dentin surfaces were flattened, and initial mass (mg) was obtained. A 4-mm2 area was delimited. Specimens were randomly assigned to 12 groups according to the combination of energy (160, 200, 250, and 300 mJ) and pulse repetition rate (2, 3, and 4 Hz). Er:YAG laser irradiation was performed for 20 s. After irradiation, the final mass was obtained, and specimens were prepared for SEM. The data obtained by subtracting the final mass from the initial mass were statistically analyzed using analysis of variance and Tukey test (alpha=0.05).
  
  
  RESULTS
  The pulse repetition rate of 4 Hz provided greater mass loss, and it was different from 2 Hz and 3 HZ. The energy of 300 mJ resulted in greater mass loss, similar to 200 and 160 mJ. SEM micrographs showed dentinal tubule obliteration, structural alterations, and the presence of cracked areas in all specimens.
  
  
  CONCLUSIONS
  The settings of 160, 200, and 250 mJ at 2 and 3 Hz promoted a good ablation rate with fewer surface alterations in primary dentin.
authors.affiliation: Department of Pediatric Clinic, Preventive and Social Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Andréa Soares
authors.initials: AS
authors.lastname: de Oliveira Ortolan
authors.forename: Carolina Paes
authors.initials: CP
authors.lastname: Torres
authors.forename: Jaciara Miranda
authors.initials: JM
authors.lastname: Gomes-Silva
authors.forename: Maria Angélica Hueb
authors.initials: MA
authors.lastname: de Menezes-Oliveira
authors.forename: Jesus Djalma
authors.initials: JD
authors.lastname: Pécora
authors.forename: Regina Guenka
authors.initials: RG
authors.lastname: Palma-Dibb
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Borsatto
mesh_terms: D000704:Analysis of Variance; D003804:Dentin / Q000528:radiation effects* / Q000648:ultrastructure; D006801:Humans; D053844:Lasers, Solid-State; D008855:Microscopy, Electron, Scanning; D008963:Molar; D011897:Random Allocation; D013499:Surface Properties; D014081:Tooth Extraction