title: Effect of Er:YAG laser parameters on ablation capacity and morphology of primary enamel.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the ablation capacity of different energies and pulse repetition rates of Er:YAG laser energy on primary molar enamel, by assessing mass loss and by analyzing the surface morphology with scanning electron microscopy.
  
  
  BACKGROUND
  Previous studies have demonstrated the capacity of the Er:YAG laser to ablate enamel substrate.
  
  
  METHODS
  Forty-two sound primary molars were bisected in a mesiodistal direction. The enamel surfaces were flattened and their initial mass (in milligrams) was obtained. An area of 4 mm(2) was delimited. The 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 on each specimen for 20 sec. After irradiation, the final mass was obtained and specimens were prepared for examination with scanning electron microscopy. The data obtained by subtracting the final mass from the initial mass were statistically analyzed using ANOVA and the Tukey test (p < 0.05).
  
  
  RESULTS
  The pulse repetition rate of 4 Hz provided greater mass loss, different from that seen with 2 Hz, and similar to that seen with 3 Hz. The energy level of 300 mJ resulted in greater mass loss, similar to that seen with 200 and 250 mJ. Scanning electron photomicrographs showed that there was non-selective enamel removal, with fused and cracked areas in all specimens.
  
  
  CONCLUSIONS
  The parameters of 200 mJ and 2 Hz produced a good ablation rate with fewer surface alterations in primary molar enamel.
authors.affiliation: Department of Pediatrics, Preventive and Social Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil. borsatto@forp.usp.br
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Borsatto
authors.forename: Carolina Paes
authors.initials: CP
authors.lastname: Torres
authors.forename: Michele Alexandra
authors.initials: MA
authors.lastname: Chinelatti
authors.forename: Jesus Djalma
authors.initials: JD
authors.lastname: Pécora
authors.forename: Silmara Aparecida Milori
authors.initials: SA
authors.lastname: Corona
authors.forename: Regina Guenka
authors.initials: RG
authors.lastname: Palma-Dibb
mesh_terms: D003731:Dental Caries / Q000532:radiotherapy*; D003737:Dental Cavity Preparation / Q000379:methods*; D003743:Dental Enamel / Q000528:radiation effects* / Q000648:ultrastructure; D006801:Humans; D053844:Lasers, Solid-State; D028022:Low-Level Light Therapy