Polymerization Lamps and Photocuring in
Orthodontics
Theodore Eliades
The purpose of this article is to review the fundamentals of photocuring with
various types of lamps in orthodontics. Information on the characteristics of
lamps, photopolymerization, from the perspective of both the material com-
posite resin adhesive and source (lamp) are discussed, with reference to light
scattering, optimum filler size, extent of polymerization, and the degree of cure
of resins irradiated with different lamps. This discussion is followed by a review
of the clinically useful listing of properties of lamps and their application to
orthodontic bonding as these are reflected in 4 key properties of the material,
such as polymerization efficiency (degree of cure), mechanical properties (bond
strength), clinical performance (failure rate), and biological properties of blue
light. (Semin Orthod 2010;16:83-90.) © 2010 Elsevier Inc. All rights reserved.
T
he development of various types of light
sources for use in polymerization has re-
sulted in a multiplicity of factors taking an active
role in the polymerization kinetics of the poly-
meric material. The variation in intensity and
wavelength with selective filtering of undesired
wavelengths has also contributed to a multifac-
eted phenomenon in photo curing, which af-
fects the properties of the resultant polymer.
This article will not place emphasis on report-
ing the performance of various types of lamps
through the typical bond strength protocols.
Such a tactic would have resulted in a dull rep-
etition of data, which are often incoherent, and
in most cases clinically irrelevant. Because of the
lack of relevant evidence in the orthodontic pub-
lished data, the fundamentals of light curing will
first be provided, as this encompasses both the
material (composite resin adhesive) and source
(lamp) perspectives. In the introductory text,
light scattering, optimum filler size, extent of
polymerization, and the degree of cure (DC) of
resins irradiated with different lamps will be re-
viewed, whereas essentials of polymer reaction
and stages will be analyzed. This discussion will
be followed by a review of the clinically useful
listing of properties of lamps and their applica-
tion to orthodontic bonding as these are re-
flected in 4 key properties of the material, such
as polymerization efficiency (DC), mechanical
properties (bond strength), clinical perfor-
mance (failure rate), and biological properties
of blue light.
Light Intensity Variation in the
Material
When a light beam hits an orthodontic adhesive
surface, penetration of light into the relatively
thin layer of material depends on many factors
related to the light beam itself, the application
mode, and the material characteristics.
First, the distance of the source from the
surface and the path that the incident beam will
have to travel to reach the adhesive has a large
effect on the intensity of incident light.
1
The
well cited Lambert Law in this field describes the
variation of intensity with distance as
I = I
0
e
-d
where I is the light intensity at distance d, I
0
the
intensity departing from the source, and the
absorption coefficient of the medium.
From the Department of Orthodontics, School of Dentistry, Aris-
totle University of Thessaloniki, Greece.
Address correspondence to Theodore Eliades, DDS, MS, DrMed,
PhD, FIMMM, MRSC, MInstP, 57 Agnoston Hiroon, Nea Ionia
14231, Greece; Email: teliades@ath.forthnet.gr
© 2010 Elsevier Inc. All rights reserved.
1073-8746/10/1601-0$30.00/0
doi:10.1053/j.sodo.2009.12.008
83 Seminars in Orthodontics, Vol 16, No 1 (March), 2010: pp 83-90