Download Use of Light Curing Units in Orthodontics

Annals of
Dental Research
Annals of Dental Research (2011) Vol 1 (1): 54-61
© Mind Reader Publications: All Rights Reserved
www.adres.yolasite.com
www.journalshub.com
Review Article
Use of Light Curing Units in Orthodontics: A Review
Goyal Amita, Jyothikiran Hb, Shivalinga BMb
a
Abstract
Department of Orthodontics and
Introduction: Because of their wide field of applications, light
Dentofacial Orthopedics, Guru Nanak
Dev Dental College, Sunam, Punjab,
India
b
Department of Orthodontics and
curing units are now indispensable for any orthodontist or a general
dentist, and hence it is very important to be familiar with the
various types of light curing units, their history, specifications,
advantages and disadvantages.
Dentofacial Orthopedics, J.S.S. Dental
Methods:
College, Mysore, Karnataka, India
review, a search was conducted in the following database: PubMed
To find the articles appropriate for this systematic
(from1966 to March 2010) using the terms ―curing lights
Correspondence to
Dr. Amit Goyal, Department of Orthodontics
and Dentofacial Orthopedics, Guru Nanak
Dev Dental College, Sunam, Punjab, India
Email: [email protected]
Phone: +91-8699347476
orthodontics‖ in the search box. Eligibility of the selected studies
was determined by reading the abstracts of articles identified by the
search. All the articles that seemed to meet the inclusion criteria of
the systematic review topic were selected and the actual articles
collected. The reference lists of the retrieved articles were also hand
searched for any applicable studies that may have been missed in
the database searches.
Article Info
Received: 21 August 2011
Revised: 20 October 2011
Accepted: 21 November 2011
Conclusion: When selecting curing lights for an office, many
variables need to be considered. Armed with knowledge about each
curing-light category, orthodontists can evaluate their unique
practice style and select the appropriate light or lights.
Annals of Dental Research (2011) 1(1), 54-61
Keywords:
Light curing units, Orthodontics.
Copyright: © 2011 Goyal et al. This is an open-access article distributed under the terms of the
Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction
in any medium, provided the original author and source are credited.
2011- A DR- 13
Light Cure in Orthodontics
Goyal et al
The light source first used for curing
Introduction
Since
the discovery of the bis-GMA
type of adhesive by Bowen, various methods
of bonding orthodontic brackets directly to
pre-conditioned tooth surfaces have been
composite resins was an ultraviolet light (UV),
which required 1 minute per millimeter of
resin thickness for curing. The benzoin methyl
ether component of composite resin was
studied by Newman 1, Mizrahi and Smith2, 3, 4,
sensitive to light in the 340 nm spectrum.
Retief, Dreyer and Gavron5, and Miura,
Because of safety concerns about the long term
Nakagawa and Masuhara6. Visible-light-cured
use of UV light, visible light curing (VLC) was
adhesives, now used by the vast majority of
orthodontists, were
first
described
by
Bassiouny7 in 1978.
Materials and methods
Studies satisfying the following criteria were
included in this systematic review:
I. Use of tungsten-quartz halogen curing
lights, argon lasers, plasma arc curing
lights or light emitting diodes for
curing orthodontic resins.
II. Cross sectional and longitudinal studies.
III. Articles in English
IV. Articles published from January 1966 to
March 2010
To find the articles appropriate for this
systematic review, a search was conducted in
the following database: PubMed (from1966 to
March 2010) and used the terms ―curing lights
orthodontics‖ in the search box.
Eligibility of the selected studies was
determined by reading the abstracts of articles
identified by the search. All the articles that
seem to meet the inclusion criteria of the
systematic review topic were selected and the
actual articles collected. The reference lists of
the retrieved articles were also hand searched
for any applicable studies that may have been
missed in the database searches.
History of curing lights
introduced around 19808. Compared with UVcured resins, VLC resins were found to have a
greater depth of curing. The curing of VLC
resins
is
based
on
the
presence
of
camphoroquinone, which is sensitive to light in
the range of 460 to 480 nm wavelength
spectrum, with an optimum at 468 nm.
The earliest visible light curing units
used halogen bulbs. Their spectrum of
radiation is continuous over the visible range,
with radiation intensity increasing significantly
towards the red end of the spectrum. Most
tungsten-quartz halogen lights produce an
energy density of approximately 400 mW/cm2,
with a broad bandwidth between 400 and 520
nm. The halogen based curing lights are still
popular in the market but despite their
popularity,
halogen
bulbs
have
several
shortcomings. These light curing units use
most of their energy to heat a tungsten filament
until it glows, creating light. Only 1% of the
total energy input is converted into light; the
remainder is generated as heat. The heat can
cause blistering of expensive light filters and
discoloration of reflectors. The cooling fan can
be noisy and bulky. Halogen bulbs have a
limited effective lifetime of approximately 40100 hours and have to be replaced thereafter.
Moreover, with a recommended curing time of
40 seconds per bracket, the light-curing time
for bonding both the maxillary and mandibular
ADR, Vol 1, Issue 1, 2011
55
Goyal et al
Light Cure in Orthodontics
arches can approach 15 minutes which can be
seconds of plasma irradiation cures many resin
inconvenient. So, reducing the curing time
composites to a hardness comparable with that
became the next immediate goal for the
achieved after 40 seconds with conventional
developers.
curing lights.
The first attempt to reduce curing time
In 1995, Mills et al11 proposed solid-
was undertaken with argon lasers in the late
state light-emitting diode (LED) technology
9
1980s . The purpose of these lamps is to
for the polymerization of light-activated dental
increase the output light energy to an intensity
materials. Instead of hot filaments used in
2
that approaches 800 mW/cm and to narrow
halogen bulbs, LEDs use junctions of doped
the wavelength to approximately 470 nm.
semiconductors to generate light. LEDs have a
Independent research has verified that argon
potential lifetime of over 10,000 hours and can
lasers can reduce the amount of light exposure,
be subjected to mechanical shock and vibration
but to equal the bracket bond strength of a 40-
with very low failure rates. The latest blue
second exposure to a conventional tungsten-
LEDs use indium gallium nitride technology
quartz halogen light, the laser must cure the
and can generate photons of a particular
composite resin for 10 seconds. This is still a
wavelength by varying the band gap. A wide
dramatic reduction in the required exposure
band gap material produces high-energy
time, from 15 minutes to 4. Nevertheless, the
photons near the blue region of the visible
argon laser has several disadvantages. The
spectrum. As current flows through the
laser units themselves are relatively large and
semiconductor chips, electrical energy is
expensive
converted directly into light, and little energy
costing
more
than
$6000;
replacement bulbs are nearly $2000.
is emitted as heat. This results in a stable,
Plasma arc curing lights (PACL) were
10
efficient, long lasting output of blue light of
introduced in mid 1990s . The light cure
440 to 480 nm.
source is a xenon gas that is ionized by 2
conversion of the LEDs has allowed the
electrodes with a large voltage potential, to
development of cordless light-curing units that
produce plasma. The emitted white light is
operate silently and have a very long life.
filtered to a bandwidth of 450-500 nm, and the
Effect of curing times on shear bond
power
strength
density
can
reach
more
than
2
2000mW/cm . These lights were made to be as
The efficient
energy
Each of the curing lights produces a
reliable as laser lights at a relatively lower cost
different
($3000-$4000). In contrast to lasers, plasma
resulting in different curing times required for
arc sources do not emit distinct frequencies
complete adhesive polymerization.
light
frequency
and
intensity,
but, rather, continuous frequency bands.
According to Lalani et al12 and Elvebak
However, these bands are much narrower than
et al13, at 300 mW power the argon laser has
those of incandescent lights (halogen bulbs).
the capability to maximally polymerize the
Consequently, less filtering of undesired
adhesive in as little as 5 seconds. Oesterle et
frequencies is required. Because of high
al14 and Signorelli et al15 found out that xenon
intensity, the manufacturers say that 1 to 3
56
ADR, Vol 1, Issue 1, 2011
Light Cure in Orthodontics
Goyal et al
plasma arc curing lamp exposure times of 6 to
9 seconds produced shear bond strengths equal
to those produced with 40 second exposures to
Effect of light guides and distance of
a conventional tungsten quartz halogen curing
light tip from the bracket on shear bond
16
17
light, in vitro. Silta et al , Usumez et al and
strength
Turkkahraman and Kucukesmen18 studied that
orthodontic brackets be photopolymerized for
atleast 20 seconds with the light emitting diode
light cure units before archwires are engaged
and that this is equivalent to 40 seconds of
halogen-based illumination. Based on the
above data it can be concluded that with
standard metal brackets, suggested curing
times for a complete cure are 15 to 20 seconds
on the mesial and distal of each bracket (total
40 seconds) using a halogen light, 10 seconds
mesial and distal (total 20 seconds) for LED
lights, 2-3 seconds mesial and distal (total 5
seconds) using an argon laser, and 3-4 seconds
mesial and distal (total 6-9 seconds) with a
plasma arc lamp. Recently, a new, highpowered halogen light was claimed to achieve
ideal bond strength with only 6 seconds of cure
time19. Ceramic brackets require half of the
Bishara et al21 studied the effects of
using a smaller diameter light guide on the
shear bond strength of orthodontic brackets.
They concluded that the use of the Mini Turbo
Light Guide (diameter 4mm) did not seem to
significantly influence either the shear bond
strength or the bracket/adhesive/enamel failure
site as compared to a standard curved light
guide (diameter 11mm). However, Evans et
al22 studied the effects of using Power Slot and
Turbo Tip light guides and concluded that
these light guides with their collimation of
visible light to increase its intensity can be
recommended as advantageous alternatives for
curing
composite
resins
for
orthodontic
bonding procedures.
The distance of the light tip to the
bracket can decrease bond strength. With
increased distance, bond strength degrades
total time for each light type, and the light
more significantly with LED lights than with
source should be aimed directly through the
other curing lights; if access is difficult, a non-
bracket20. Molar bonds require about 150%
LED light source should be considered. 23
longer curing times on each the mesial and
distal.
Temperature rise
Halogen, argon laser, and plasma arc
Effect of light intensity on shear bond
strength
lights all generate significant heat and require a
cooling fan. All of these instruments therefore
13
Elvebak et al compared the shear bond
generate significant noise during and after
strength produced by an argon laser at 4
operation. Although halogen lights have
different power settings (100, 150, 200 and
powerful fans to cool the unit, the intense heat
250 mW) and found out that brackets bonded
does damage the light bulb so that the effective
using the curing light of 150mW power
bulb life is only about 100 hours.24 The
exhibited the highest bond strength.
minimal heat generated by LED lights can be
easily dissipated by heat sinks, and these lights
ADR, Vol 1, Issue 1, 2011
57
Goyal et al
Light Cure in Orthodontics
can therefore operate noiselessly. Heat from
microleakage with quartz tungsten halogen
curing units is transferred to teeth during
(mean, 1.10 ± 1.05 mm) and the greatest
bonding procedures; this can, at times, cause
microleakage with plasma arc curing light
discomfort to patients. It is known that any
curing units (mean, 2.63 ± 1.49 mm). Serdar
increase in pulpal temperature exceeding 5°C
Arikan et al32 compared microleakage beneath
to 6°C may result in irreversible tissue
ceramic and metal brackets photopolymerized
25
showed that in vitro
with light emitting diode or conventional light
pulp chamber temperature increase from laser
curing units and observed microleakage along
units were significantly lower than that from
all bonding interfaces, regardless of the type of
26
bracket or LCU used. The tested light emitting
measured the temperature rise in the composite
diode curing unit provided a reduction in chair
samples with three different light sources, and
time but caused more leakage between
because of very short exposure time, they
adhesive-bracket
found a slight temperature rise with the high-
brackets were used. However Mustafa Ulker et
power plasma light. Cobb et al27 and Powell et
al33 found that the type of light-curing unit
al28 concluded that argon lasers should pose no
(Halogen, light emitting diode, plasma arc
threat to the pulp if used at recommended
curing) did not significantly affect the amount
energies. In fact, Powell et al25 stated that, at
of microleakage at the enamel-adhesive-
recommended curing times, in vitro pulp-
bracket complex.
chamber temperature increases from argon
Design considerations
damage. Powell et al
the conventional curing lights. Tarle et al
interface
when
metal
lasers were significantly lower than those of
The energy efficiency and minimal heat
the conventional curing lights. Aslihan Uzel et
generation of LED curing give them many
al
29
and Siddik Malkoc et al
30
found in their
characteristics that the other sources do not
study that halogen light induced significantly
have. Because they use minimal energy and do
higher intrapulpal temperature changes than
not need a cooling fan, LED lights are able to
did the LED and PAC. However, orthodontic
be marketed as cordless units with a
bonding with light-curing units did not exceed
rechargeable battery. And because they do not
the critical 5.5°C value for pulpal health.
have any moving parts or light filaments, they
Microleakage
better resist vibration and shock. 34 As there is
Asli
Baysal
et
al31
studied
the
no heat damage to the diodes, LED lights are
microleakage under bonded lingual retainers
effective for more than 10,000 hours of use
using high-intensity curing lights and found
with little output degradation.
that little or no microleakage occurs at the
Although their exact mechanisms are
composite/enamel interface with high-intensity
unknown, argon lasers uniquely restructure
light curing units. However, high-intensity
enamel-surface
light curing units allow more microleakage at
some demineralization resistance when used
the composite/wire interface and may not be
for
safe
synergistically with the protection imparted by
for
bonding
of
lingual
retainers.
Comparison of the results showed the least
58
bonding.
characteristics,
This
protection
conferring
increases
fluoride.35
ADR, Vol 1, Issue 1, 2011
Light Cure in Orthodontics
Each
of
the
Goyal et al
various
curing-light
2. Mizrahi E, Smith DC. Direct cementation of
varieties has a different design. Plasma arc and
orthodontic brackets to dental enamel. An
argon laser curing lights are cumbersome and
investigation using a zinc polycarboxylate
weigh between 9 and 15 pounds. Many owners
cement. Br Dent J. 1969 Oct 21;127(8):371-5.
of these lights mount the light on a rolling cart
3. Mizrahi E, Smith DC. Direct attachment of
or dedicate a single chair for bonding
orthodontic brackets to dental enamel. A
procedures and leave the curing light there.
preliminary clinical report. Br Dent J. 1971
Halogen lights occupy a small footprint and
May 4;130(9):392-6.
are often mounted chairside by each unit.
4. Mizrahi E, Smith DC. Direct attachment of
Corded LED lights have similar space
orthodontic brackets to dental enamel a
requirements to halogen lights, while their
preliminary clinical report. Oral Health. 1971
cordless counterparts can be left in any
Dec;61(12):11-4.
convenient location.
5. Miura F, Nakagawa K, Masuhara E. New
Conclusion
direct bonding system for plastic brackets. Am
When selecting curing lights for an
J Orthod. 1971 Apr;59(4):350-61.
office, many variables need to be considered.
6. Retief DH, Dreyer CJ, Gavron G. The direct
Each practitioner needs to evaluate the
bonding of orthodontic attachments to teeth by
infrastructure and patient flow of the office.
means of an epoxy resin adhesive. Am J
Some orthodontists choose to have a light at
Orthod. 1970 Jul;58(1):21-40.
each chair, while others are comfortable
7. Bassiouny MA, Grant AA. A visible light-
having one or two portable lights. The speed
cured composite restorative. Clinical open
offered by plasma arc curing can be coupled
assessment.
with the portability of an LED light to move
5;145(11):327-30.
from chair to chair. Some practitioners choose
8. Mills LF. Status report: dental visible light-
to do extensive gingival recontouring, and a
curing units. Council on Dental Materials,
laser could provide both high-speed curing and
Instruments, and Equipment. J Am Dent
hemostatic
Assoc. 1982 Apr;104(4):505.
surgical
potential.
Other
Br
Dent
J.
1978
Dec
practitioners may object to fan noise and use
9. Powell GL, Kelsey WP, Blankenau RJ,
LED exclusively. Armed with knowledge
Barkmeier WW. The use of an argon laser for
about each curing-light category, orthodontists
polymerization of composite resin. J Esthet
can evaluate their unique practice style and
Dent. 1989;1:34–37.
select the appropriate light or lights.
10.
Cacciafesta
V,
Sfondrini
MF,
Sfondrini G. A xenon arc light-curing unit for
bonding and
References
1. Newman
GV.
Epoxy
adhesives
for
bleaching.
J
Clin
Orthod
2000;34:94-6.
orthodontic attachments: progress report. Am J
11.
Mills RW. Blue light emitting diodes-
Orthod. 1965 Dec;51(12):901-12.
another method of light curing? Br Dent J
1995;178:169.
ADR, Vol 1, Issue 1, 2011
59
Goyal et al
Light Cure in Orthodontics
12.
Nazir Lalani, Timothy F. Foley,
halogen lamp. Am J Orthod Dentofacial
Robert
Voth,
Orthop. 2005;128: 749–54.
David
Banting,
Antonios
Mamandras. Polymerization with the Argon
20.
Laser: Curing Time and Shear Bond Strength.
overview. Clinical Impressions 2000;9:15-7.
Angle Orthod 2000;70:28–33.
21.
13.
Bryan S. Elvebak, P. Emile Rossouw,
Judy Zamtua. Effects of different types of light
Barbara H. Miller, Peter Buschang, Richard
guides on shear bond strength. Am J Orthod
Ceen. Orthodontic Bonding with Varying
Dentofacial Orthop 1998;113:447-51.
Curing Time and Light Power Using an Argon
22.
Laser. Angle Orthod 2006;76:837-44.
Craig Flickinger, Louis Taloumis, William
14.
J.
Oesterle,
Sheldon
JH.
Curing
lights:
an
Samir E. Bishara, Leigh VonWald,
Larry James Evans, Charles Peters,
M.
Dunn. A comparison of shear bond strengths
Newman, W. Craig Shellhart. Rapid curing of
of orthodontic brackets using various light
bonding composite with a xenon plasma arc
sources, light guides, and cure times. Am J
light. Am J Orthod Dentofacial Orthop
Orthod Dentofacial Orthop 2002;121:510-5.
2001;119:610-6.
23.
15.
Scribante A, Boehme A, Jost-Brinkmann PG.
Peter
Larry
Mayes
Michael D. Signorelli, Elizabeth Kao,
W.
Comparison
Ngan,
of
Marcia
bond
A.
strength
Cacciafesta
V,
Sfondrini
MF,
Gladwin.
Effect of light-tip distance on the shear bond
between
strengths of composite resin. Angle Orthod.
orthodontic brackets bonded with halogen and
2005;75:352–7.
plasma arc curing lights: An in-vitro and in-
24.
vivo study. Am J Orthod Dentofacial Orthop
Caughman WF, Khajotia S. Lifetime intensity
2006;129:277-82.
profiles of 11 light-curing units [abstract
16.
2897]. J Dent Res. 1996;75:380.
Charles
Y. Teresa Silta, William J. Dunn, and
B.
Peters.
Effect
of
shorter
25.
Rueggeberg
FA,
Twiggs
SW,
Powell GL, Anderson JR, Blankenau
polymerization times when using the latest
RJ. Laser and curing light induced in vitro
generation of light-emitting diodes. Am J
pulpal temperature changes. J Clin Laser Med
Orthod Dentofacial Orthop 2005;128:744-8.
Surg. 1999;17:3–5.
17.
26.
Serdar Usumez, Tamer Buyukyilmaz,
Tarle Z, Meniga A, Knezevic A,
AliIhya Karaman. Effect of Light-Emitting
Sutalo J, Ristic M, Pichler G. Composite
Diode on Bond Strength of Orthodontic
conversion and temperature rise using a
Brackets. Angle Orthod 2004;74:259–263.
conventional, plasma arc and experimental
18.
blue LED curing unit. J Oral Rehabil.
Hakan Turkkahramana, H. Cenker
Kucukesmen. Orthodontic Bracket Shear Bond
2002;29:662–667.
Strengths Produced by Two High-power Light-
27.
emitting Diode Modes and Halogen Light.
In
Angle Orthod 2005;75:854–857.
dentin/pulpal interface by using conventional
19.
Staudt
CB,
Mavropoulos
A,
Bouillaguet S, Kiliaridis S, Krejcid I. Light-
Cobb DS, Dederich DN, Gardner TV.
vitro
temperature
change
at
the
visible light versus argon laser. Lasers Surg
Med 2000;26:386-97.
curing time reduction with a new high-power
60
ADR, Vol 1, Issue 1, 2011
Light Cure in Orthodontics
28.
Goyal et al
Powell GL, Morton TH, Whisenant
BK. Argon laser oral safety parameters for
teeth. Laser Surg Med 1993;13:548-52.
29.
Aslihan Uzela, Tamer Buyukyilmazb,
Mustafa Kayaliogluc, Ilter Uzel. Temperature
Rise
During Orthodontic
Bonding
With
Various Light-curing Units—An In Vitro
Study. Angle Orthod 2006;76:330–334.
30.
Sıddık Malkoc , Tancan Uysal, Serdar
Usumez, Eren Isman, Aslı Baysal. In-vitro
assessment of temperature rise in the pulp
during orthodontic bonding. Am J Orthod
Dentofacial Orthop 2010;137:379-83.
31.
Asli Baysal, Tancan Uysal, Mustafa
Ulker, Serdar Usumez. Effects of HighIntensity Curing Lights on Microleakage under
Bonded Lingual Retainers. Angle Orthod
2008;78:1084-8.
32.
Serdar Arıkan, Neslihan Arhun, Ayca
Arman, Sevi Burcak Cehreli. Microleakage
beneath
Ceramic
and
Metal
Brackets
Photopolymerized with LED or Conventional
Light
Curing
Units.
Angle
Orthod
2006;76:1035-40.
33.
Mustafa Ulker, Tancan Uysal, Sabri
Ilhan Ramoglu, Huseyin Ertas. Microleakage
under Orthodontic Brackets Using HighIntensity
Curing
Lights.
Angle
Orthod.
2009;79:144–149.
34.
Mills RW, Jandt KD, Ashworth SH.
Dental composite depth of cure with halogen
and blue light emitting diode technology. Br
Dent J. 1999;186:388–91.
35.
Noel L, Rebellato J, Rose D, Sheats
RD. The effect of argon laser irradiation on
demineralization resistance of human enamel
adjacent to orthodontic brackets: an in vitro
study. Angle Orthod. 2003;73: 249–258.
Citation : Goyal A, Jyothikiran H, Shivalinga BM. Use of
Light Curing Units in Orthodontics: A Review. Annals of
Dental Research 2011; 1 (1): 54-61.
ADR, Vol 1, Issue 1, 2011
61