title: Vicker's hardness and Raman spectroscopy evaluation of a dental composite cured by an argon laser and a halogen lamp.
abstract: We present the results of the Vicker's hardness test and the use of near-infrared Raman spectroscopy (RS) to measure in vitro the degree of conversion (DC) of a bis(phenol)-A-glycidyl-dimethacrylate-based composite resin, photoactivated by both a halogen lamp (power density=478 mW/cm(2); 8-mm diameter spot) and an argon laser (power density=625 mW/cm(2); 7-mm diameter spot). The degree of conversion was estimated by analyzing the relative intensities between the aromatic C=C stretching Raman mode at 1610 cm(-1) and the methacrylate C=C stretching Raman mode (1640 cm(-1)) on top and bottom surfaces. For the hardness evaluation, the samples were embedded in polyester resin and three indentations with a 50-g load for 10 s were made on the top surface. The higher relative DC values achieved by the photoactivation of a composite resin by the argon laser suggest a better biocompatibility in the bottom surface. The correlation test showed that the higher Vicker's hardness number (VHN) values were associated with higher DC values. The derivative analysis showed a greater curing rate from 5 to 20 s of exposure. The comparison of VHN and DC values with both light sources at each curing time showed that a small change in conversion is related to a large change in hardness. Raman spectroscopy is more sensitive to changes in the first stages of curing reaction than later ones, and the Vicker's hardness assay is more sensitive to changes in the last stages.
authors.affiliation: University of Vale do Paraaiba-UNIVAP, School of Dentistry, Laboratorio de Espectroscopia Vibracional Biomedical, Av. Shishima Hifumi, 2911, Urbanova-CEP 12.224-000, Sao Jose dos Campos, Sao Paulo, Brazil.
authors.forename: Luís Eduardo Silva
authors.initials: LE
authors.lastname: Soares
authors.forename: Airton Abrahão
authors.initials: AA
authors.lastname: Martin
authors.forename: Antonio Luiz Barbosa
authors.initials: AL
authors.lastname: Pinheiro
authors.forename: Marcos T T
authors.initials: MT
authors.lastname: Pacheco
mesh_terms: D003188:Composite Resins / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D003764:Dental Materials / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects; D003793:Dental Restoration, Permanent / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D006244:Hardness; D006245:Hardness Tests / Q000295:instrumentation / Q000379:methods*; D007834:Lasers; D008027:Light; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D013059:Spectrum Analysis, Raman / Q000295:instrumentation / Q000379:methods*; D015040:Zirconium / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C083568:Z100 composite resin; D012822:Silicon Dioxide; D015040:Zirconium