title: Effect of erbium:yttrium-aluminum-garnet laser energies on superficial and deep dentin microhardness.
abstract: This study evaluated the microhardness of superficial and deep dentin irradiated with different erbium:yttrium-aluminum-garnet (Er:YAG) laser energies. Seventy-two molars were bisected and randomly assigned to two groups (superficial dentin or deep dentin) and into six subgroups (160 mJ, 200 mJ, 260 mJ, 300 mJ, 360 mJ, and control). After irradiation, the cavities were longitudinally bisected. Microhardness was measured at six points (20 microm, 40 microm, 60 microm, 80 microm, 100 microm, and 200 microm) under the cavity floor. Data were submitted to analysis of variance (ANOVA) and Fisher's tests (alpha = 0.05). Superficial dentin presented higher microhardness than deep dentin; energy of 160 mJ resulted in the highest microhardness and 360 mJ the lowest one. Values at all points were different, exhibiting increasing microhardness throughout; superficial dentin microhardness was the highest at 20 microm with 160 mJ energy; for deep dentin, microhardness after irradiation at 160 mJ and 200 mJ was similar to that of the control. The lowest energy increased superficial dentin microhardness at the closest extent under the cavity; deep dentin microhardness was not altered by energies of 160 mJ and 200 mJ.
authors.affiliation: Department of Restorative Dentistry, Ribeirão Preto School of Dentistry, University of São Paulo (USP), Ribeirão Preto, 14040-904, São Paulo, Brazil. michinelatti@hotmail.com
authors.forename: Michelle Alexandra
authors.initials: MA
authors.lastname: Chinelatti
authors.forename: Walter
authors.initials: W
authors.lastname: Raucci-Neto
authors.forename: Silmara Aparecida Milori
authors.initials: SA
authors.lastname: Corona
authors.forename: Regina Guenka
authors.initials: RG
authors.lastname: Palma-Dibb
mesh_terms: D003737:Dental Cavity Preparation / Q000009:adverse effects / Q000379:methods; D003804:Dentin / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure; D006244:Hardness / Q000528:radiation effects; D006245:Hardness Tests; D006801:Humans; D066298:In Vitro Techniques; D053844:Lasers, Solid-State / Q000009:adverse effects / Q000627:therapeutic use*; D008855:Microscopy, Electron, Scanning; D008964:Molar, Third / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D011897:Random Allocation