title: Effect of light irradiation on tooth whitening: enamel microhardness and color change.
abstract: The aim of this study was to evaluate the influence of light exposure associated with 35% hydrogen peroxide (Pola Office, SDI, Melbourne, Vic., Australia) or 15% hydrogen peroxide (BriteSmile, Discus, Culver City, CA, USA) on the microhardness and color changes of bovine enamel. Experimental groups were Britesmile + Light (BL) (15% hydrogen peroxide + plasm arc; 4 x 20 minutes), Britesmile + No Light (BN) (BL, no light), Pola office + Light (PL) (35% hydrogen peroxide + LED; 4 x 8 minutes), and Pola office + No light (PN) (PL, no light). Color changes (DeltaE) and the CIELAB (Commission Internationale de l' Eclairage, L* a* b* color system) parameters (L*, a*, and b*) were assessed with a spectrophotometer before (B), immediately (A), 1 day and 7 days after bleaching. The microhardness was measured before (B) and after (A), the obtained data were submitted to a two-way analysis of variance, and DeltaE were submitted to t-test for each period. Only Pola Office, in which the peroxide is associated with the light, improved DeltaE when evaluated immediately after bleaching (p < 0.001). Light exposure did not influence DeltaE after 1 day or 7 days for either bleaching system. The enamel microhardness was not altered after bleaching for BriteSmile. However, enamel microhardness was reduced after bleaching for Pola Office, 283 MPa (+/-21) and 265 MPa (+/-27), respectively. It was concluded that these two bleaching systems were efficient regardless of the light systems used. However, the 35% hydrogen peroxide altered the enamel microhardness. CLINICAL SIGNIFICANCE Enamel microhardness was affected by a 35% hydrogen peroxide in-office bleaching therapy. Moreover, the in-office bleaching outcome was not improved by using the light associated with systems tested in this study. (J Esthet Restor Dent 21:387-396, 2009).
authors.affiliation: Department of Dental Materials, School of Dentistry, University of São Paulo, Av. Prof. Lineu Prestes, 2227,Cidade Universitária, 05508-900 São Paulo, Brazil. maungomes@usp.br
authors.forename: Mauricio Neves
authors.initials: MN
authors.lastname: Gomes
authors.forename: Carlos
authors.initials: C
authors.lastname: Francci
authors.forename: Igor Studart
authors.initials: IS
authors.lastname: Medeiros
authors.forename: Nívea Regina
authors.initials: NR
authors.lastname: De Godoy Froes Salgado
authors.forename: Heraldo
authors.initials: H
authors.lastname: Riehl
authors.forename: José Milton
authors.initials: JM
authors.lastname: Marasca
authors.forename: Antônio
authors.initials: A
authors.lastname: Muench
mesh_terms: D000818:Animals; D002417:Cattle; D003116:Color; D003743:Dental Enamel / Q000033:anatomy & histology / Q000528:radiation effects*; D006244:Hardness; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000528:radiation effects; D016877:Oxidants / Q000008:administration & dosage / Q000528:radiation effects; D010789:Phototherapy / Q000295:instrumentation / Q000379:methods; D011829:Radiation Dosage; D011897:Random Allocation; D013053:Spectrophotometry; D013696:Temperature; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D016877:Oxidants; D014867:Water; D006861:Hydrogen Peroxide