JCDA - Canadian Dental Association

Background
Light-emitting diode (LED) curing lights last longer
and produce less heat than conventional quartz–
tungsten–halogen (QTH) curing lights. However, firstgeneration
LED curing lights did not perform as well as
conventional QTH curing lights. Second-generation LED
lights are now available, and they may offer better performance
and shorter curing times. This study compared a
second-generation LED light with a QTH light to determine
which was better at photopolymerizing a range of
resin composites.
Methods
The ability of a second-generation LED curing light,
used for 20 and 40 seconds, was compared with that of a
traditional QTH light, used for 40 seconds, in the curing
of a selection of 10 multipurpose, flowable and posterior
resin composites. The light output from each unit was
measured with a spectroradiometer. Three examples of each
type of curing light were used to irradiate the composites at
distances of 2 and 9 mm from the light guide. The 2-mm
distance represented the shortest distance from a cusp tip to
the composite in a Class I restoration. The 9-mm distance
represented a clinical situation with a deep proximal box in
a molar tooth. The Knoop hardness at the top and bottom
of the 1.6-mm thick composite specimens was measured
after 15 minutes in air and after 24 hours in water at 37°C.
The hardness values at the top and bottom of the specimens
irradiated at both distances were combined, and a
general linear model analysis with Sidak’s adjustment for
666 November 2003, Vol. 69, No. 10
A P P L I E D R E S E A R C H
Evaluation of a Second-Generation
LED Curing Light
• Richard B.T. Price, BDS, DDS, MS, FDS RCS (Edin), FRCD(C), PhD •
• Corey A. Felix, BSc, MSc •
• Pantelis Andreou, PhD •
A b r i d g e d V e r s i o n
The complete article can be viewed on the eJCDA Web site at: http://www.cda-adc.ca/jcda/vol-69/issue-10/666.html
© J Can Dent Assoc 2003; 69(10):666
This article has been peer reviewed.
multiple comparisons was used to compare the ability of
the lights to cure the composites to a depth of 1.6 mm.
Results
The 2 lights delivered similar power densities at 0, 2 and
9 mm from the light guide, but the spectral distributions
were very different. The second-generation LED lights
produced a narrow spectral output with a mean ± standard
deviation peak at 445.2 ± 0.3 nm. The QTH lights had
a much wider spectral bandwidth with a peak at 491.3
± 4.2 nm. The various curing lights and times did not have
the same effects on all of the composites (p < 0.01). Twentyfour
hours after irradiation, the LED light used for
20 seconds was able to cure 5 of the composites as well as
the QTH light used for 40 seconds (p > 0.01) and 7 of the
composites to more than 80% of the hardness obtained
when the QTH light was used. When the LED light was
used for 40 seconds, 6 of the 10 composites achieved
a hardness (after 24 hours) equivalent to when the
QTH light was used (p > 0.01), and all 10 composites
achieved more than 80% of the hardness developed when
the QTH light was used.
Conclusions
This LED light could not polymerize all of the composites
as well as the QTH light. However, when used for
40 seconds, more than half of the composites were cured as
well as when the QTH light was used (p > 0.01), and all of
the composites achieved a hardness comparable to that
produced with the QTH light. C
Journal of the Canadian Dental Association