Continuing Education 2
Light-Curing Considerations
for Resin-Based Composite
Materials: A Review. Part I
Neeraj Malhotra, MDS;1 and Kundabala Mala, MDS2
Abstract: There has been a continual advent of improved technologies in dentistry. Among these are the material sciences
of resin-based composites (RBCs). Since the introduction of light-cured RBCs, the problem of polymerization shrinkage and
the methods used to overcome this have concerned clinicians and researchers. Types of curing light and modes of curing
have been shown to affect the degree of polymerization and related shrinkage of RBCs. This review, which is divided into
two parts, discusses the contemporary light-curing units. Part I explores the evolution in light-curing units and different
curing modes. Part II highlights the clinical considerations regarding light curing of RBCs that are important for achieving
optimal curing and maximum polymerization of RBCs in a clinical setting.
T
he method of polymerization of resin-based composites (RBCs) determines the technique of insertion,
direction of polymerization shrinkage, finishing
procedure, color stability, and amount of internal porosity.
Initially, RBCs were chemically activated and supplied as two
pastes containing a benzoyl peroxide initiator and an aromatic
tertiary amine activator (N, N-dimethyl-p-toluidine). They
were bulk-filled with the direction of polymerization shrinkage toward the center of the mass,1 had internal pores that
Learning Objectives
After reading this article, the reader should be able to:
■
■
■
s ummarize the evolution of light-curing units for
resin-based composites.
iscuss the advantages and disadvantages of various
d
light-curing devices.
explain various light-curing modes.
inhibited polymerization during curing, provided no control
with the working time, increased the finishing time, and had
less color stability due to breakdown of tertiary amines. Then,
light-activated systems were introduced, which used ultraviolet (UV) light. Because these methods had the harmful
biologic effects of UV rays and poor penetration through the
tooth structure, they were replaced by visible blue light-activated systems.2,3 These commonly employ camphorquinone
(CQ) as the photoinitiator (474 nm) and an aliphatic amine
activator (dimethylaminoethyl methacrylate). They are filled
incrementally with the polymerization shrinkage directed
toward the light source.1 They have better depth of cure with
a controllable working time, no internal porosity, enhanced
color stability due to aliphatic amine, more translucency, and
improved esthetics. One of the major disadvantages of lightcured RBCs is polymerization shrinkage and associated stress
generation that may lead to clinical failure of RBC restorations.1-4 Light-cured RBCs generate higher polymerization
stresses as compared with chemical-cured RBCs. The type
of curing light and curing mode partly governs and influences
Assistant Professor, Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, India
1
Professor, Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, India
2
498
Compendium
September 2010—Volume 31, Number 7
the quantity and quality of RBC polymerization.5 Another
way to improve the degree of polymerization and reduce the
shrinkage stresses is by the use of extra-oral curing with pressure
and vacuuming.6,7 In Part 1, the authors explain the different
light-curing units, operating characteristics, and curing modes
for RBCs. The associated clinical considerations and factors
influencing the efficiency of light-curing units are discussed
in the second part of the review.
Neeraj Malhotra, MDS
Kundabala Mala, MDS
LIGHT-CURING UNITS
Various light-curing units belonging to different generations are available commercially. Usually, they are hand-held
devices with a light source and light guide of fused optical
fibers. A curing unit with a minimal light output of 550 lux
is considered appropriate for dental use.8
Quartz Tungsten Halogen
Quartz tungsten halogen (QTH) devices are the most widely
used light-curing units and contain a quartz bulb with a tungsten filament in a halogen environment. The units irradiate
both UV and white light that must be filtered to remove heat
and transmit light only in the violet-blue region of the spectrum
that matches the photoabsorption range of CQ. They are available in continuous, step-cure, or ramp-cure modes. Less than
0.5% of the total light produced in a QTH is suitable for curing, and most is converted to heat. To minimize heating, UV
and infrared band-pass filters are inserted just before the fiber
optic system is used. Orange filters are widely used because they
are complementary to blue and absorb blue radiation. A small
fan is employed to dissipate unwanted heat from the filters and
reflector. Usually, filters degrade with time due to the heating
and cooling cycles. QTH-curing lights work at wavelengths
of 400 nm to 500 nm5 with output ranging from 400 mW/
cm2 to 800 mW/cm2. QTH-curing lights have been shown to
produce the smallest amount of residual monomer in RBCs.9
Disadvantages:
They have a slower cure time (about 15 sec to 20 sec).
The units are relatively large and cumbersome.
The lights (bulbs) decrease in output with time and
thus need frequent replacement.
They have low-energy performance and generate
high temperatures.
They require a filter and ventilating fan.
■■ ■■ ■■ ■■ ■■ www.compendiumlive.com
Turbo tips provide greater curing intensity and faster
curing than QTH units; they become smaller as they exit
the curing light. More recently, enhanced halogen curing
lights have been introduced commercially. To date, mixed
data have been reported from in vitro studies regarding the
performance of these light-curing units. Hardness of RBC
specimens (2 mm) obtained following curing with some of
these high-intensity lights is found to be similar to conventional QTH- and LED-curing lights.10 However, other units
have shown greater polymerization shrinkage and less effective curing of RBC than with conventional QTH units.11
Thus, further research is required to identify their potential
in dental practices.
Light-Emitting Diode
Light-emitting diode (LED) lamps are based on LEDs
Initially, low-power blue LEDs using silicon carbide (firstgeneration LEDs) having a power output of 7 μW per LED
were introduced. Blue LEDs, or second-generation LEDs,
were built on gallium nitride technology and had a power
output of 3 mW (400-fold increase). The second generation
LEDs are considered to be more effective in curing composites than their predecessors.12 These units are cordless,
small, lightweight, and battery-powered.13 They do not
require filters because they emit light at a specific wavelength
within the 400-nm to 500-nm photoabsorption range of
CQ. Thus, all the emitted light is useful, resulting in highenergy performance of the curing light. The spectral output
falls between 410 nm and 490 nm or between 450 nm and
490 nm. These units show a constant effectiveness without
any drop in intensity with time because the diodes do not
require frequent replacement.13 Because no heat generation
occurs during curing, a cooling fan is not needed.
Compendium
499
Continuing Education 2
Disadvantages:
The batteries must be recharged.
They cost more than conventional halogen lights.
The curing time is slower than that of plasma-arc
curing lights and some enhanced halogen lights.
A literature review suggests LED devices and conventional
QTH-curing lights have no significant differences.14 LED
units are considered similar or better compared with QTH units
regarding the degree of polymerization,15-17 microleakage at
enamel and dentin margins,18,19 shrinkage strain behavior,20,21
wear rate of RBCs,22 flexural properties of cured RBCs,23 and
hardness of cured RBCs.24,25 Also, bond strength values for
dual-cure resin cements used in cementation of indirect RBC
restorations is found to be equivalent for LED- and QTHcuring lights.26 However, depth of curing with LED units is
higher than QTH devices,27,28 and QTH-curing lights tend
to show more yellowing of RBCs than LEDs.29 The variables
of water sorption and solubility of RBCs are not dependent
on the type of curing light used.30
Few authors consider conventional QTH-curing lights
to be better than LEDs.31,32 LEDs have been shown to take
longer for complete curing of microfilled and hybrid RBCs32
and do not satisfy manufacturers’ claims for minimum intensities.33 Thus, a necessary increase in the light intensity
of these units has been suggested.9 Future LEDs will need a
high power output to compensate for a narrow bandwidth
or broader frequency spectrum.5 Thus, the newer generation
units of LEDs are a good option as curing-light devices for
RBCs but need further improvements.
■■ ■■ ■■ Plasma Arc
Plasma-arc curing (PAC) lights are high-intensity lightcuring units. They have more intense light sources (fluorescent bulb-containing plasma), allowing for shorter exposure
times. Light is obtained from an electrically conductive gas
(xenon) called plasma that forms between two tungsten
electrodes under pressure. The light spectrum provided by
plasma is limited.5 The wavelength of high-intensity light
emitted is determined by the bulb-coating material and
filtered out to minimize transmission of infrared and UV energy and to allow emission of blue light (400 nm to 500 nm).
This also helps remove the heat from the system. Because a
high-intensity light is available at lower wavelengths, these
units are able to cure composites with photoinitiators other
than camphorquinone. The comparative clinical efficiency
of PAC lights largely depends on the type of photoinitiator
used.34 These units have a high energy output and short
500
Compendium
curing time. An exposure of 10 secs from a PAC light is
equivalent to 40 secs from a QTH light.6 These units have
been shown to have higher conversion rates35 and depths of
cure for RBCs as compared with QTH units.36 These sys­
tems work at wavelengths between 370 nm and 450 nm or
between 430 nm and 500 nm.
Disadvantages:
The heat production must be controlled.
They are expensive.
The lamp (bulb) replacement is costly.
Most devices are large, heavy, and bulky.
They have low-energy performance.
Filters and ventilating fan are required.
The results obtained from the QTH units are better than
those acquired from PAC units.5,34,37,38 RBCs cured with a PAC
unit have shown more polymerization shrinkage than with
QTH units.39 Despite rapid curing, a xenon lamp produces
marginal contraction with dentin bonding agents. The hardness
values of RBC specimens cured by the PAC units have been
shown to be significantly lower than LED and QTH units.10
The recommended time of 3 secs for PAC units is inadequate
and should be doubled to obtain optimal mechanical properties of RBCs.5 An incremental technique of 2 mm should be
followed. These units, when used in combination with QTH
units, have been shown to provide higher bond strength values
for dentin bonding agents.40 The devices are best suited for
cementation of orthodontic bands and brackets.41
■■ ■■ ■■ ■■ ■■ ■■ Argon Laser
Laser lamps are high-intensity lamps based on the laser principle. The emitted wavelength depends on the material used
(argon produces blue light). Argon laser lamps have the
highest intensity. These lamps work within a limited range
of wavelengths, do not require filters, and require shorter
exposure times for curing RBCs. The devices generate little
infrared output, so not much heat is produced. They work
at specific bandwidths of light in the ranges of 454 nm to
466 nm, 472 nm to 497 nm, and 514 nm. Because a laser is
a narrow beam of coherent light, no loss of power over distance occurs as in seen in QTH units. Therefore, argon laser
curing lights are the units of choice for inaccessible areas.5
Disadvantages:13
The curing depth is limited to 1.5 mm to 2 mm.
The curing tip is small, so more time is needed to
cure the RBCs.
They have narrow spectral outputs.
They are expensive.
■■ ■■ ■■ ■■ September 2010—Volume 31, Number 7
Malhotra and Mala
Studies have reported similar results for both laser and
QTH units.42,43 No difference in bond strength is seen between the argon laser and standard QTH units. Laser devices
have been shown to produce an increased degree and depth
of cure for RBCs.44 The laser systems have also demonstrated
greater material wear,45 more polymerization shrinkage, and
increased marginal leakage.46 Recently, a diode-pumped
solid-state (DPSS) laser (473 nm) was introduced, and its
effect on the degree of RBC polymerization has been tested.
One study demonstrated these units produce better or similar polymerization and color change than QTH and LED
devices do47 and possess high potential to be an alternative
to the other light-curing systems.48 These devices are not
available commercially. Thus, these laser-based units are
promising as curing lights for RBCs; their usage is still not
a widely accepted idea in clinical settings.
USE OF RADIOMETERS
The light intensity and output of a light-curing unit can
be monitored using a portable or built-in radiometer chairside. A radiometer measures the number of photons, unit
area, and unit time through a standard 11-mm diameter
window. Curing unit tips that are smaller or larger cannot be tested effectively. Usually, a minimal output higher
than 300 mW/cm2 is recommended. Also, the radiometer
measures all light energies and cannot discriminate the light
energy of the photoinitiator, limiting the measurement of
the real value.
LIGHT-CURING TECHNIQUES
Soft Start
One method to reduce polymerization shrinkage-associated
stresses and microleakage is by providing an initial low
rate of polymerization.5 This may reduce the stress buildup
by supplying extended time for stress relaxation before reach­
ing the gel phase. This can be accomplished by using a
soft-start curing technique in which the curing begins with
a low intensity and finishes with a high intensity.49 This
causes the maximal possible conversion to occur only af­ter much of the stress has been relieved. Various lightcuring units au­tomatically provide one or more soft-start
exposure sequences. Some produce a 100 mW/cm2 output
for 10 secs, followed by an immediate increase to 600 mW/
cm2 output for 30 secs. Soft-start polymerization is divid­ed
into three techniques: stepped, ramped, and pulse-delay2
(Figure 1).
www.compendiumlive.com
Ramped
During exposure, intensity is gradually increased or “ramped
up.” This can be in stepwise, linear, or exponential modes. For
ramped curing, the intensity is increased with time (30 secs)
either by bringing the light toward the tooth from a distance,
curing through a cusp, or using a curing light designed to
increase in intensity. This sequential curing of composite
from low to high intensity significantly reduced polymerization shrinkage without compromising the depth of cure.50
Ramped curing allows the light-cured material to have a
longer gel phase in which polymerization contraction stresses
are dissipated more readily.
Staged (Delayed Curing)
In this format, the restoration is initially cured at low intensity to contour and shape the restoration in occlusion,
followed by a second exposure to completely cure the restoration.2 This allows substantial relaxation of polymerization
stresses. The longer the period available for relaxation, the
lower the generation of residual stresses is. This method also
aids in the finishing of composite restorations—a partially
cured composite material can be easily finished as compared
with fully cured material. By filtering the light during an
initial cure, obtaining a soft, easily finished material is possible. Thereafter, the filter is removed and the composite is
cured completely.
Pulse Delay
In the pulse-delay method, a series of exposure pulses is used,
each separated by a dark interval. An initial exposure of up
to 1 J/cm2 is considered to be most efficient in reducing
shrinkage stresses. Another important parameter is delay
time between irradiances. During the dark period, polymerization reaction occurs at a reduced rate. Thus, longer delays
lead to a greater amount of chain relaxation. Significant
reductions in shrinkage stress and microleakage and increased microhardness have been reported for pulse-delay
methods, with dark periods from 1 min to 5 mins.51,52 For
pulse-delay curing, the greatest reduction of polymerization
shrinkage is achieved with a delay of 3 mins to 5 mins.5 No
statistically significant difference is reported in microleakage
of nanofilled and microhybrid RBCs cured with different
soft-start polymerization modes (pulse, ramp, and staged).53
High Intensity
High-intensity curing allows for shorter exposure times for a
given depth of cure. A depth of 2 mm can be cured in 10 secs
Compendium
501
Continuing Education 2
of light, heat, pressure, and vacuum to increase the degree of
polymerization and wear resistance of RBCs. Hardness and
depth of cure of an indirect RBC can be influenced by the
LPUs employed.58 It is reported that LPUs, which provide
light curing in conjunction with heat and nitrogen pressure, result in a significant increase in hardness and tensile
strength of RBCs.59
BIOLOGICAL SAFETY OF
LIGHT-CURING UNITS
Figure 1 Soft-start light-curing techniques. (A) Ramped. (B)
Staged (delayed curing). (C) Pulse delay.
with a PAC light and 5 secs with an argon laser-curing light,
as compared with 40 secs by a QTH lamp. A high-intensity
curing initiates a multitude of growth centers during an
initial irradiation period along with a final polymer with
higher cross-link density. Because the relationship between
energy density and post-gel shrinkage strain is considered to
be linear,54 high-energy densities may translate into increased
stress levels but do not result necessarily in high degrees of
conversion or superior mechanical properties. Therefore,
although high-intensity curing may lead to the same conversion rate, degree of polymerization shrinkage, and mechanical properties,5 it likely leads to greater shrinkage stresses.55
Disadvantages:
Short exposure times cause accelerated rates of curing
and insufficient time for stress relaxation.56 This leads
to greater shrinkage stresses and a poorer interface.
High-intensity light curing has a narrowed wavelength
range for the output. Therefore, the wavelength
range of the light source must be coincident with the
photoinitiator.
Heat is a significant problem.
It may not produce the same type of polymer network
during curing.
Using a higher intensity of light for shorter exposure
time is reported to result in more cytotoxicity than a
longer curing time with lower intensity.57
■■ ■■ ■■ ■■ ■■ Extra-Oral Curing
Usually, extra-oral curing is used for the fabrication of indirect RBC restorations (inlays, veneers, metal-free bridges,
etc) that are processed in the laboratory.6 These laboratory
photocuring units (LPUs) work with various combinations
502
Compendium
Various high-intensity light sources have been developed to
polymerize RBCs more rapidly. Since their introduction, any
associated adverse biologic effect of these units has concerned
clinicians and led to the evaluation of the biologic safety of
the high-intensity blue light units and sources. Wataha et al60
observed that when human monocytic cells were irradiated
with three light sources (QTH, plasma arc, and laser), the
secretion of TNF-a was not induced following exposure.
Thus, exposure to blue light cannot be considered a possible
inflammatory risk factor in dental tissues during curing of
composites. A reduction in toxicity associated with a RBC
is also possible if the curing mode is adapted to the type of
RBC used.61 It has been suggested additional cytotoxicity
tests in animal models are needed before confirmation of
the clinical risks can be made.60
Another concern is the electromagnetic interference with
cardiac pacemakers during the operation of contemporary
electrical dental equipment, including light-curing units.
Although initial reports have shown no deleterious effects of
these composite curing lights on the rate or rhythm of cardiac
pacemakers or implantable cardioverter-defibrilllators,62,63
more recent literature indicates that the battery-operated composite curing light may produce problems in certain patients.64
CONCLUSION
Polymerization shrinkage is the main disadvantage of RBCs.
Both curing lights and curing methods contribute greatly
to this shrinkage. The clinical performance of the new generation of light-curing units is reported to be similar to the
conventional units. These new generation systems have high
power density, high light intensity, and shortened exposure time, leading to reduced chairside time and enhanced
depth of cure. However, these high-intensity units have
disadvantages and are not readily used in dental practice.
Further modification and improvement of the light units
may help achieve the best outcome and successful RBC
restorations. Similarly, curing techniques, such as soft-start
September 2010—Volume 31, Number 7
Malhotra and Mala
polymerization, have been shown to improve the polymerization kinetics of RBCs. Thus, both the quantity and quality
of polymerization can be improved with a proper selection
of light-curing units and clinical curing techniques.
REFERENCES
1. Hilton TJ. Direct posterior esthetic restorations. In: Summitt
JB, Robbins JW, Hilton TJ, et al, eds. Fundamentals of Operative
Dentistry. Chicago, IL: Quintessence; 2001:260-305.
2. Rawls RH, Esquivel-Upshaw JF. Restorative resins. In: Anu­
sa­vice KJ, editor. Phillip’s Science of Dental Materials. 11th ed.
St. Louis, MO: Saunders; 2003:399-442.
3. Bayne SC, Thompson JY, Taylor DF. Dental materials. In:
Roberson TM, Heymann HO, Swift EJ, eds. Strudevant’s Art
and Science of Operative Dentistry. 4th ed. St. Louis, MO:
Mosby; 2002:134-234.
4. Katona TR, Winkler MM, Huang J. Stress analysis of a bulkfilled Class-V chemical-cured dental composite restoration. J
Biomed Mater Res. 1996;31(4):445-449.
5. Jiménez-Planas A, Martin J, Abalos C, et al. Developments in
16. Korkmaz Y, Attar N. Dentin bond strength of composites with
self-etching adhesives using LED curing lights. J Contemp Dent
Pract. 2007;8(5):34-42.
17. Ye Q, Wang Y, Williams K, et al. Characterization of photopolymerization of dentin adhesives as a function of light
source and irradiance. J Biomed Mater Res B Appl Biomater.
2007;80(2):440-446.
18. Attar N, Korkmaz Y. Effect of two light-emitting diode (LED)
and one halogen curing light on the microleakage of Class V
flowable composite restorations. J Contemp Dent Pract. 2007;
8(2):80-88.
19. Sensi LG, Junior SM, Baratieri LN. Effect of LED light curing
on the marginal sealing of composite resin restorations. Pract
Proced Aesthet Dent. 2006;18(6):345-351.
20. U hl A, Mills RW, Rzanny AE, et al. Time dependence of
composite shrinkage using halogen and LED light curing. Dent
Mater. 2005;21(3):278-286.
21. Lopes LG, Franco EB, Pereira JC, et al. Effect of light-curing units
and activation mode on polymerization shrinkage and shrinkage
stress of composite resins. J Appl Oral Sci. 2008;16(1):35-42.
polymerization lamps. Quintessence Int. 2008;38(2):e74-e84.
22. Ramp LC, Broome JC, Ramp MH. Hardness and wear resis-
6. Powers JM, Sakaguchi RL. Craig’s Restorative Dental Materials.
tance of two resin composites cured with equivalent radiant
12th ed. St. Louis, MO: Mosby; 2007:189-182.
7. Wakefield CW, Kofford KR. Advances in restorative materials.
Dent Clin North Am. 2001;45(1):7-29.
8. Williams PT, Johnson LN. Composite resin restoratives revisited. J Can Dent Assoc. 1993;59(6):538-543.
ex­posure from a low irradiance LED and QTH light-curing
units. Am J Dent. 2006;19(1):31-36.
23. Keogh P, Ray NJ, Lynch CD, et al. Surface microhardness of a resin composite exposed to a “first-generation” LED curing lamp,
in vitro. Eur J Prosthodont Restor Dent. 2004;12(4):177-180.
9. Filipov IA, Vladimirov SB. Residual monomer in a composite
24. Lima DA, De Alexandre RS, Martins AC, et al. Effect of curing
resin after light-curing with different sources, light intensities
lights and bleaching agents on physical properties of a hybrid
and spectra of radiation. Braz Dent J. 2006;17(1):34-38.
composite resin. J Esthet Restor Dent. 2008;20(4):266-275.
10. Yazici AR, Kugel G, Gül G. The Knoop hardness of a composite
25. de Araújo CS, Schein MT, Zanchi CH, et al. Composite resin
resin polymerized with different curing lights and different
microhardness: the influence of light curing method, composite
modes. J Contemp Dent Pract. 2007;8(2):52-59.
shade, and depth of cure. J Contemp Dent Pract. 2008;9(4):43-50.
11. Yap AU, Wong NY, Siow KS. Composite cure and shrinkage
26. Camilotti V, Grullón P G, Mendonça M J, et al. Influence of
associated with high intensity curing light. Oper Dent. 2003;
different light curing units on the bond strength of indirect res-
28(4):357-364.
in composite restorations. Braz Oral Res. 2008;22(2):164-169.
12. Park SH, Kim SS, Cho YS, et al. Comparison of linear polym-
27. Mills RW, Uhl A, Jandt KD. Optical power outputs, spectra
erization shrinkage and microhardness between QTH-cured
and dental composite depths of cure, obtained with blue light
& LED-cured composites. Oper Dent. 2005;30(4):461-467.
emitting diode (LED) and halogen light curing units (LCUs).
13. Christensen GJ. The curing light dilemma. J Am Dent Assoc.
2002;133(6):761-763.
14. Campregher UB, Samuel SM, Fortes CB, et al. Effectiveness
of second-generation light-emitting diode (LED) light curing
units. J Contemp Dent Pract. 2007;8(2):35-42.
15. Hasler C, Zimmerli B, Lussi A. Curing capability of halogen
and LED light curing units in deep class II cavities in extracted
human molars. Oper Dent. 2006;31(3):354-363.
www.compendiumlive.com
Br Dent J. 2002;193(8):459-463.
28. Owens BM. Evaluation of curing performance of light-emitting
polymerization units. Gen Dent. 2006;54(1):17-20.
29. Brackett MG, Brackett WW, Browning WD, et al. The effect
of light curing source on the residual yellowing of resin composites. Oper Dent. 2007;32(5):443-450.
30. Archegas LR, Caldas DB, Rached RN, et al. Sorption and
solubility of composites cured with quartz-tungsten halogen
Compendium
503
Continuing Education 2
and light emitting diode light-curing units. J Contemp Dent
Pract. 2008;9(2):73-80.
31. Cefaly DF, Ferrarezi GA, Tapety CM, et al. Microhardness
of resin-based materials polymerized with LED and halogen
curing units. Braz Dent J. 2005;16(2):98-102.
32. Leonard DL, Charlton DG, Roberts HW, et al. Polymerization
efficiency of LED curing lights. J Esthe Restor Dent. 2002;14(5):
286-295.
36. Hasegawa T, Itoh K, Yukitani W, et al. Depth of cure and mar­
ginal adaptation to dentin of xenon lamp polymerized resin
com­posites. Oper Dent. 2001;26(6):585-590.
37. Park SH, Krejci I, Lutz F. Microhardness of resin composites
polymerized by plasma arc or conventional visible light curing.
Oper Dent. 2002;27(1):30-37.
38. Millar BJ, Nicholson JW. Effect of curing with plasma light on
the properties of polymerizable dental restorative materials. J
33. Owens BM, Rodriguez KH. Radiometric and spectrophotometric analysis of third generation light-emitting diode (LED)
light-curing units. J Contemp Dent Pract. 2007;8(2):43-51.
34. Hofmann N, Hiltl O, Hugo B, et al. Guidance of shrinkage vec-
Oral Rehabil. 2001;28(6):549-552.
39. Park SH, Noh BD, Cho YS, et al. The linear shrinkage and
mi­cro­hardness of packable composites polymerized by QTH
or PAC unit. Oper Dent. 2006;31(1):3-10.
tors vs irradiation at reduced intensity for improving marginal
40. D’Alpino PH, Wang L, Rueggeberg FA, et al. Bond strength of
seal of class V resin-based composite restorations. Oper Dent.
resin-based restorations polymerized with different light-curing
sources. J Adhes Dent. 2006;8(5):293-298.
2002;27(5):510-515.
35. D’Alpino PH, Svizero NR, Pereira JC, et al. Influence of light-
41. Ishikawa H, Komori A, Kojima I, et al. Orthodontic bracket
curing sources on polymerization reaction kinetics of a restor-
bonding with a plasma-arc light and resin-reinforced glass iono-
ative system. Am J Dent. 2007;20(1):46-52.
mer cement. Am J Orthod Dentofacial Orthop. 2001;120(1):
58-63.
42. Ramos Lloret P, Lacalle Turbino M, Kawano Y, et al. Flexural
properties, microleakage, and degree of conversion of a resin
Online Only
polymerized with conventional light and argon laser. Quin­tes­
Visit www.compendiumlive.com to read:
Review of Intraoral Harvesting for
Bone Augmentation: Selection Criteria,
Alternative Sites, and Case Report
Federico Brugnami, DDS;
Alfonso Caiazzo, DDS;
and Cataldo Leone, DMD, DMSc
sence Int. 2008;39(7):581-586.
43. Rode KM, de Freitas PM, Lloret PR, et al. Micro-hardness
evaluation of a micro-hybrid composite resin light cured with
halogen light, light-emitting diode and argon ion laser. Lasers
Med Sci. 2009;24(1):87-92.
44. Fleming MG, Maillet WA. Photopolymerization of composite resin using the argon laser. J Can Dent Assoc. 1999;65(8):
447-450.
45. St-Georges AJ, Swift EJ Jr, Thompson JY, et al. Curing light
intensity effects on wear resistance of two resin composites.
Immediate Temporization of
Immediate Implants in the Esthetic Zone:
Case Reports Evaluating Survival and
Bone Maintenance
Oper Dent. 2002;27(4):410-417.
46. Sfondrini MF, Cacciafesta V, Pistorio A, et al. Effects of conventional and high-intensity light-curing on enamel shear bond
strength of composite resin and resin-modified glass-ionomer.
Am J Orthod Dentofacial Orthop. 2001;119(1):30-35.
47. Jung YH, Cho BH, Nah KS, et al. Effect of diode-pumped
Barry P. Levin, DMD
solid state laser on polymerization shrinkage and color change
Oral Factitious Injury in a Child
with Kabuki Syndrome
Rose Wadenya, DMD, MS;
Andres Pinto, DMD, MPH; and
Rochelle Lindemeyer, DMD
in composite resins [published online ahead of print February
10, 2009]. Lasers Med Sci.
48. Kwon YH, Jang CM, Shin DH, et al. The applicability of
DPSS laser for light curing of composite resins. Lasers Med Sci.
2008;23(4):407-414.
49. Davidson CL, Davidson-Kaban SS. Handling of mechanical
stresses in composite restorations. Dent Update. 1998;25(7):
274-279.
504
Compendium
September 2010—Volume 31, Number 7
50. Dennison JB, Yaman P, Seir R, et al. Effect of variable light
intensity on composite shrinkage. J Prosthet Dent. 2000;84(5):
499-505.
51. Pfeifer CS, Braga RR, Ferracane JL. Pulse-delay curing: influ-
presents
ence of initial irradiance and delay time on shrinkage stress
and microhardness of restorative composites. Oper Dent. 2006;
31(5):610-615.
52. Lopes LG, Franco EB, Pereira JC, et al. Effect of light-curing
units and activation mode on polymerization shrinkage and
Made in USA
shrinkage stress of composite resins. J Appl Oral Sci. 2008;16(1):
35-42.
53. Hardan LS, Amm EW, Ghayad A. Effect of different modes of
light curing and resin composites on microleakage of Class II
restorations. Odontostomatol Trop. 2008;31(124):27-34.
54. Silikas N, Eliades G, Watts DC. Light intensity effects on resin-composite degree of conversion and shrinkage strain. Dent
Mater. 2000;16(4):292-296.
55. Unterbrink G, Muessner R. Influence of light intensity on two
restorative systems. J Dent. 1995;23(3):183-189.
56. Ilie N, Felten K, Trixner K, et al. Shrinkage behavior of a resinbased composite irradiated with modern curing units. Dent
Mater. 2005;21(5):483-489.
57. Knezevic A, Zeljezic D, Kopjar N, et al. Cytotoxicity of composite materials polymerized with LED curing units. Oper Dent.
2008;33(1):23-30.
58. Tanoue N, Murakami M, Koizumi H, et al. Depth of cure
and hardness of an indirect composite polymerized with three
laboratory curing units. J Oral Sci. 2007;49(1):25-29.
SPECIAL
OFFER
50 FREE FG
DIAMONDS
WITH THE
PURCHASE
OF THIS
NEW LIGHT
OFFER
EXPIRES
11/1/10
BEST
POWER
FOR
THE
PRICE!
59. da Silva GR, Simamoto-Júnior PC, da Mota AS, et al. Mech­anical
properties of light-curing composites polymerized with different laboratory photo-curing units. Dent Mater J. 2007;26(2):
217-223.
60. Wataha JC, Lewis JB, Lockwood PE, et al. Response of THP-1
monocytes to blue light from dental curing lights. J Oral Rehabil.
2008;35(2):105-110.
61. Sigusch BW, Völpel A, Braun I, et al. Influence of different light
curing units on the cytotoxicity of various dental composites.
Dent Mater. 2007;23(11):1342-1348.
62. Miller CS, Leonelli FM, Latham E. Selective interference with
pacemaker activity by electrical dental devices. Oral Surg Oral
Med Oral Pathol Oral Radiol Endod. 1998;85(1):33-36.
63. Brand HS, Entjes ML, Nieuw Amerongen AV, et al. Interference
of electrical dental equipment with implantable cardioverterdefibrillators. Br Dent J. 2007;203(10):577-579.
64. Roedig JJ, Shah J, Elayi CS, et al. Interference of cardiac pace­maker
Special
Introductory
Price
and implantable cardioverter-defibrillator activity during electronic dental device use. J Am Dent Assoc. 2010;141(5):521-526.
For more information or to order,
call 800.800.1680 or fax 610.630.9730
www.compendiumlive.com
Product Specialist: [email protected]
www.SpringHealthProducts.com
Continuing Education 2
Quiz 2
Light-Curing Considerations for Resin-Based
Composite Materials: A Review. Part I
Neeraj Malhotra, MDS; and Kundabala Mala, MDS
This article provides 2 hours of CE credit from AEGIS Publications, LLC. Record your answers on the enclosed answer sheet or submit
them on a separate sheet of paper. You may also phone your answers in to (215) 504-1275 or fax them to (215) 504-1502 or log on
to www.compendiumlive.com and click on “Continuing Education.” Be sure to include your name, address, telephone number,
and last 4 digits of your Social Security number.
  1. A curing unit with a minimal light output of how
many lux is considered appropriate for dental use?
a.350
b.450
c. 550
d.650
  6. Argon laser curing lights are the units of choice for:
a.inaccessible areas.
b.anterior restorations.
c. underneath metal crowns.
d.composites that use seventh-generation bonding
techniques.
  2. QTH devices are the most widely used light-curing
  7. A radiometer measures the number of photons, unit
units and contain:
a.a quartz bulb.
b.a tungsten filament.
c. a halogen environment.
d.all of the above
area, and unit time:
a.by measuring reflected light in a sensor.
b.through a standard 11-mm diameter window.
c. only in dark ambient light conditions.
d.using a relativity-based algorithm.
  3. Less than 0.5% of the total light produced in a QTH
  8. For ramped curing, the intensity is increased with
a.bringing the light toward the tooth from a
b.curing through a cusp.
c. using a curing light designed to increase in intensity.
d.all of the above
is suitable for curing, and most is:
a.converted to heat.
b.the wrong wavelength.
c. the wrong frequency.
d.the wrong amplitude.
  4. Blue LEDs, or second-generation LEDs, were built on
which technology?
a.silicon carbide
b.gallium nitride
c. selenium fluoride
d.tungsten halide
curing lights units largely depends on the:
a.type of photoinitiator used.
b.distance between the source and composite.
c. type of transmission line used.
d.availability of a high-voltage electrical
commercial power source.
distance.
  9. For pulse-delay curing, the greatest reduction of po
  5. The comparative clinical efficiency of plasma-arc
time (30 secs) by:
lymerization shrinkage is achieved with a delay of:
a.3 to 5 secs.
b.3 to 5 mins.
c. 3 to 5 hours.
d.3 to 5 days.
10. Usually, extra-oral curing is used for the fabrication of
indirect RBC restorations (inlays, veneers, metal-free
bridges, etc) that are:
a.used in patients with excessive saliva.
b.in need of an immediate repair to a composite.
c. processed in the laboratory.
d.extremely shade-sensitive for esthetic situations.
Please see tester form on page 508.
ADA CERP is a service of the American Dental Association to assist dental professionals in identifying quality
providers of continuing dental education. ADA CERP does not approve or endorse individual courses or
instructors, nor does it imply acceptance of credit hours by boards of dentistry.Concerns or complaints
about a CE provider may be directed to the provider or to ADA CERP at www.ada.org/goto/cerp.
AEGIS Publications, LLC is an ADA CERP Recognized Provider.
Program Approval for
Continuing Education
Approved PACE Program Provider
FAGD/MAGD Approved
7/18/1990 to 12/31/2012
Approval does not imply acceptance
by a state or provisional board of
dentistry or AGD endorsement.