title: Influence of physical assessment of different light-curing units on irradiance and composite microhardness top/bottom ratio.
abstract: The aim of this study was to evaluate the influence of the physical assessment of different light-curing units from 55 dental offices on the irradiance and composite microhardness top/bottom ratio, and the influence of the radiometers for LED or QTH light sources on irradiance measurement. The irradiance of each light-curing unit was evaluated with two radiometers, either for LED or QTH light. A questionnaire regarding the type of source (LED or QTH), time of use, date of last maintenance and light-curing performance assessment applied. The physical assessments were evaluated regarding damage or debris on the light tip. For each light-curing unit, three composite specimens were made (diameter = 7 mm; thickness = 2 mm) with polymerizing time of 20 s, in order to perform the microhardness (Knoop) test. Data were analyzed by Kruskal-Wallis and Dunn test (α = 0.01). There was wide variation in irradiance (0-1000 mW/cm(2)). Approximately 50 % of the light-curing units presented radiation lower than 300 mW/cm(2); 10 % of light-curing units, especially those with LED source, presented values higher than 800 mW/cm(2), and 43 % of light-curing units worked with adequate irradiance between 301 and 800 mW/cm(2). In almost 60 % of cases, no maintenance of light-curing units was performed in a period of 3 to 10 years. The age of the light-curing units and the use of inadequate tips interfered negatively in irradiance. The data emphasize the importance of periodic maintenance of light-polymerizing, light-curing units.
authors.affiliation: School of Dentistry, Ibirapuera University, Avenida Interlagos, 4°. Andar, 1329-Chácara Flora, São Paulo, SP, 04661-100, Brazil.
authors.forename: Susana
authors.initials: S
authors.lastname: Morimoto
authors.affiliation: School of Dentistry, Ibirapuera University, Avenida Interlagos, 4°. Andar, 1329-Chácara Flora, São Paulo, SP, 04661-100, Brazil.
authors.forename: Renata Aló Maluza
authors.initials: RA
authors.lastname: Zanini
authors.affiliation: Department of Dental Materials, School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: Josete Barbosa Cruz
authors.initials: JB
authors.lastname: Meira
authors.affiliation: School of Dentistry, Ibirapuera University, Avenida Interlagos, 4°. Andar, 1329-Chácara Flora, São Paulo, SP, 04661-100, Brazil.
authors.forename: Carlos Martins
authors.initials: CM
authors.lastname: Agra
authors.affiliation: School of Dentistry, Ibirapuera University, Avenida Interlagos, 4°. Andar, 1329-Chácara Flora, São Paulo, SP, 04661-100, Brazil.
authors.forename: Fernanda Calabró
authors.initials: FC
authors.lastname: Calheiros
authors.affiliation: School of Dentistry, Ibirapuera University, Avenida Interlagos, 4°. Andar, 1329-Chácara Flora, São Paulo, SP, 04661-100, Brazil. dynagase@yahoo.com.
authors.forename: Denis Yudi
authors.initials: DY
authors.lastname: Nagase
mesh_terms: D001938:Brazil; D003188:Composite Resins / Q000737:chemistry*; D055117:Curing Lights, Dental; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006244:Hardness; D008422:Materials Testing; D055668:Photochemical Processes; D011829:Radiation Dosage; D013499:Surface Properties; D011795:Surveys and Questionnaires
chemical_list: D003188:Composite Resins
keywords: Dental offices; Hardness; Irradiance; Light output; Light-curing units; Radiometers