2008 Volume 51 Issue 5 Pages 543-549
Curing units using blue light emitting diodes (LED) as a source of light are superior in energy efficiency with reduced heat generation. The curing units can be made compact, which is beneficial in clinical situations. Recently, high power density curing units which utilize blue LEDs whose spectral distributions fit those of photo-initiation have been used to polymerize visible light-cured restoratives. However, although new types of curing units using different LEDs have been available, little is known about their curing characteristics. The purpose of this study was to evaluate the curing irradiation characteristics of LED curing units in terms of curing depth, polymerization shrinkage, and Knoop hardness. The results were as follows: 1. Spectral distributions of the curing units were different and the peak wavelength was 453-465 nm for LED curing units, and 480 nm for halogen lamp curing units. 2. The power density of LED curing units ranged from 601 to 887 mW/cm2, and was 832 mW/cm2 for halogen lamp curing units. 3. The curing depth ranged from 1.93 to 2.87 mm for LED curing units, and from 1.92 to 2.47 mm for halogen lamp curing units. 4. Volumetric change ranged from 1.38 to 2.03% for LED curing units, and from 1.22 to 1.59% for halogen lamp curing units. 5. Knoop hardness number on the irradiated surface decreased as the distance from the center increased.
