Effect of Er:YAG laser parameters on ablation capacity and morphology of primary enamel.
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.
Borsatto
Maria Cristina
MC
Department of Pediatrics, Preventive and Social Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil. borsatto@forp.usp.br
Torres
Carolina Paes
CP
Chinelatti
Michele Alexandra
MA
Pécora
Jesus Djalma
JD
Corona
Silmara Aparecida Milori
SA
Palma-Dibb
Regina Guenka
RG
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