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Microhardness of a Resin Cement Polymerized by Light‐Emitting Diode and Halogen Lights through Ceramic
Author(s) -
Hooshmand Tabassom,
Mahmoodi Nasrin,
Keshvad Alireza
Publication year - 2009
Publication title -
journal of prosthodontics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.902
H-Index - 60
eISSN - 1532-849X
pISSN - 1059-941X
DOI - 10.1111/j.1532-849x.2009.00449.x
Subject(s) - materials science , indentation hardness , composite material , ceramic , cement , polymerization , curing (chemistry) , halogen lamp , light emitting diode , microstructure , polymer , optoelectronics , optics , physics
Purpose: This study evaluated the curing efficiency of light‐emitting diode (LED) and halogen [quartz tungsten halogens (QTH)] lights through ceramic by determining the surface microhardness of a highly filled resin cement. Materials and Methods: Resin cement specimens (Variolink Ultra; with and without catalyst) (5‐mm diameter, 1‐mm thick) were condensed in a Teflon mold. They were irradiated through a ceramic disc (IPS Empress 2, diameter 5 mm, thickness 2 mm) by high‐power light‐curing units as follows: (1) QTH for 40 seconds (continuous), (2) LED for 20 seconds, and (3) LED for 40 seconds (5‐second ramp mode). The specimens in control groups were cured under a Mylar strip. Vickers microhardness was measured on the top and bottom surfaces by a microhardness tester. Data were analyzed using analysis of variance (ANOVA) and a post hoc Bonferroni test at a significance level of p < 0.05. Results: The mean microhardness values of the top and bottom surfaces for the dual‐cured cement polymerized beneath the ceramic by QTH or LED (40 seconds) were significantly higher than that of light‐cured cement ( p < 0.05). The top and bottom surface microhardness of dual‐cured cement polymerized beneath the ceramic did not show a statistically significant difference between the LED and QTH for 40 seconds ( p > 0.05). Conclusions: The efficiency of high‐power LED light in polymerization of the resin cement used in this study was comparable to the high‐power QTH light only with a longer exposure time. A reduced curing time of 20 seconds with high‐power LED light for photopolymerizing the dual‐cured resin cement under ceramic restorations with a minimum 2‐mm thickness is not recommended.