Effect of light-curing units, post-cured time and shade of resin cement on knoop hardness

Brazilian Dental Journal

Rogério Vieira Reges²  Ana Rosa Costa²  Américo Bortolazzo Correr²  Evandro Piva¹  Regina Maria Puppin-rontani¹  Mário Alexandre Coelho Sinhoreti²  Lourenço Correr-sobrinho² 

[1] ,State University of Campinas Piracicaba Dental School Dental Materials DivisionPiracicaba SP ,Brazil

关键词: Knoop hardness;    dental ceramic;    resin cement;    light-curing unit;   

DOI  :  10.1590/S0103-64402009000500009

来源: SciELO

【 摘 要 】

The aim of this study was to evaluate the Knoop hardness after 15 min and 24 h of different shades of a dual-cured resin-based cement after indirect photoactivation (ceramic restoration) with 2 light-curing units (LCUs). The resin cement Variolink II (Ivoclar Vivadent) shade XL, A2, A3 and opaque were mixed with the catalyst paste and inserted into a black Teflon mold (5 mm diameter x 1 mm high). A transparent strip was placed over the mold and a ceramic disc (Duceram Plus, shade A3) was positioned over the resin cement. Light-activation was performed through the ceramic for 40 s using quartz-tungsten-halogen (QTH) (XL 2500; 3M ESPE) or light-emitting diode (LED) (Ultrablue Is, DMC) LCUs with power density of 615 and 610 mW/cm2, respectively. The Koop hardness was measured using a microhardness tester HMV 2 (Shimadzu) after 15 min or 24 h. Four indentations were made in each specimen. Data were subjected to ANOVA and Tukey's test (a=0.05). The QTH LCU provided significantly higher (p<0.05) KHN values than the LED LCU. When the post-cure times were compared for the same shade, QTH and LED at 24 h provided significantly higher (p<0.05) KHN values than at 15 min. It may be concluded that the Knoop hardness was generally dependent on the LCU and post-cure time. The opaque shade of the resin cement showed lower Knoop hardness than the other shades for both LCUs and post-cure times.

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