Comparison of light emitting diode curing unit and halogen based light curing unit for the polyme /certified fixed orthodontic courses by Indian dental academy

“COMPARISON OF LIGHT EMITTING
DIODE CURING UNIT AND HALOGEN
BASED LIGHT CURING UNIT FOR THE
POLYMERIZATION OF ORTHODONTIC
RESINS – AN IN VITRO STUDY ”
Title:
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Introduction
 The development of firm attachment of
brackets to the teeth is one of the
prominent milestones in the orthodontic
field as it enables efficient movement
of the teeth. Firm attachment was
initially achieved by cementing bands on
all the teeth.

 In orthodontics, bonding with light
activated system is popular because the
extended working time allows for
precise bracket placement and ease of
manipulation. Once the bracket is
situated at the desired location rapid
set is accomplished through photo
activation.

Currently four different technologies
are available for curing of dental
composites by light.
 Halogen lamps
 Plasma arc lamps
 Lasers
 LED

 In 1995, Mills et al proposed solid state
light emitting diode for the
polymerization of light activated dental
materials. Rather than a hot filament as
used in halogen bulbs, LED‟s use
junctions of doped semiconductors (p-n
junctions) for the generation of light.

 The spectral output of gallium nitride
blue LED falls conveniently within the
absorption spectrum of camphoroquinone
photo-initiator (400-500 nm) present in
light activated dental materials, so that
no filters are required in LED LCU‟s.
 Furthermore LED‟s have an expected
lifetime of several thousand hours
without significant degradation of light
flux over time.

 The purpose of this study is to
compare the shear bond strength
of orthodontic brackets bonded to
teeth with conventional halogen
light curing unit and commercial
LED light curing unit.

 To compare the shear bond strength
of orthodontic brackets bonded to
teeth with conventional halogen light
curing unit and commercial LED light
curing unit.
 To determine the site of bond failure.
Objectives

Materials;
 Fifty extracted human bicuspid teeth
 Distilled water
 Pumice and rubber prophylactic cups
 Orthodontic metal brackets
 Light emitting diode-curing unit(3M ESPE Elipar
Freelight2)
 Halogen based light curing unit(3M ESPE Elipar
2500)
 Transbond XT light cure adhesive (3M-Unitek)
 Mounting jig
 Self cure acrylic
 Universal testing machine connected with computer.

METHOD :
A. Teeth:
Fifty human bicuspid teeth extracted in
the Department of Oral Surgery, College
of Dental Sciences, Davangere, for
orthodontic purposes were collected and
stored in distilled water.

The criteria for tooth selection included;
 Intact buccal enamel
 Not subjected to any pretreatment
chemical agent
 No caries
 No cracks caused by the pressure of
extraction forceps.

The teeth thus collected were randomly
divided into 2 groups of 25 each and
embedded in yellow and blue self curing
acrylic upto the level of the cemento-
enamel junction. The labial surfaces of
the teeth were kept perpendicular to
the bottom surface of the mold.

Cleaning and Etching :
The teeth were cleaned and polished with
pumice and rubber prophylactic cups. The
buccal surface of each tooth was etched
for 30 seconds with 37% phosphoric acid
gel3. Each tooth was then rinsed with a
water spray for 20 seconds and dried with
oil free air for 10 seconds3. The buccal
enamel surface of the etched teeth
appeared chalky white.

A light cured adhesive primer
(Transbond XT, 3M Unitek) was placed
on the etched enamel surface, lightly air
thinned and polymerized for 10 seconds
as recommended by the manufacturer.

 Brackets :
Premolar brackets of 0.022” slot MBT prescription
(3M-Unitek Gemini series) were used (Fig. 4). The
surface area of the bracket base was 10.61 mm2 as
described by the manufacturer.

Bonding Procedure:
The two groups were bonded in exactly the same
manner with the exception of the light source.
 Group 1 (Colour code: Yellow) : 25 teeth were
bonded using conventional halogen based light
curing unit (3M-ESPE Elipar 2500)

 Group 2 (Colour code: Blue) : 25 teeth were
bonded using LED light curing unit (3M-ESPE
Elipar Freelight 2) .

 The bracket adhesive interface was
cured for 20 seconds on the mesial side
of the bracket and for 20 seconds on
the distal side, for a total cure time of
40 seconds.

Technical Details
 The 3M ESPE Elipar 2500 halogen curing light
produce high intensity visible blue light in the
400 to 500 mm wavelength.
 The Elipar 2500 light has an optical filter
which reduces radiation above 520 mm. A 75
watt bulb is supplied in the unit. The bulb has
a minimum average life of 4000 cycles at 20
seconds each cycle (average lifetimes of
approximately 23 hours) .

 A single high intensity LED generates
light in the Elipar Freelight 2 LED
curing light. In contrast to
conventioned LED‟s high intensity LED‟s
use a substantially larger semiconductor
crystal which increases both the
illuminated area and light intensity

 Dissipation of heat generated by the
LED‟s during operation is crucial for
durabality of LED based systems. With
the Elipar Freelight 2 LED curing light,
heat is dissipated by a heat sink of
highly thermally conductive aluminium
integrated in the housing. This kind of
heat management is possible only with
the moderate amount of heat produced
by the LED, which represent less than
5% of the amount produced by the
halogen lamp

Shear Bond Strength Testing Procedure :
 Shear bond strength testing was done using a
Hounsfield universal testing machine which was
connected to a digital meter and the debonding
force was recorded automatically in Kgf.

 The test samples were stressed for debonding at a
crosshead speed of 1 mm/min until the bracket
debonded.

Adhesive Remnant Score;
 The amount of adhesive remaining on the tooth was
evaluated using a stereomicroscope (Olympus SZX12) .
The amount of adhesive remaining was scored on the
basis of a modified Adhesive Remnant Index (ARI) .

5 = No composite remained on the enamel
4 = Less than 10%of composite remained on
the enamel
3 = Greater than 10% & less than 90% of
composite remained on the enamel
2 = Greater than 90% of composite remained
on the enamel
1 = All of the composite with the impression
of the bracket base remained on the enamel

Statistical Analysis :
 The mean and standard deviations were
calculated for the shear bond strengths of
the two groups. Students „t‟ test was used to
compare the shear bond strength of the two
groups and the Mann-Whitney test was
performed to compare the ARI scores of
both the groups. A p-value of less than 0.05
was considered for statistical significance.

Results
The students„t‟ test revealed that Group
– I – Halogen based LCU (Mean 8.89
2.46) and Group II – LED LCU (Mean
8.30 1.51) exhibited almost the same
bond strengths and the difference
between the two groups is not
significant. (P>0.05)

ARI SCORES
It was found that there were no
significant differences in the debonding
characteristics of the two groups with
the majority of the bond failures
occurring within the adhesive

Graph 1 : SHEAR BOND STRENGTH
8.89
8.30
0.0
2.0
4.0
6.0
8.0
10.0
12.0
Group I Group II
MeanBS+/-sd(MPa)

5
6
8
7
11
7
1
4
0
1
0
2
4
6
8
10
12
No.ofsamples
Score 1 Score 2 Score 3 Score 4 Score 5
A R I Scores
Graph 2 : A R I Scores
Group I
Group II

Discussion
The most popular method of delivering blue
light has been with halogen based light curing
units. Halogen bulbs generate light when
electric energy heats a small tungsten
filament to high temperatures. Most of the
energy put into the halogen system is charged
into heat but a small portion is given off as
light.

 Despite their popularity, halogen bulbs have
several short comings. Halogen bulbs have an
effective lifetime of approximately 100
hours. High heat is generated degrading the
components of the halogen bulb over time
 The lamp reflector may lose its reflector
properties because of loss of reflective
material, or deposition of surface impurities.

 In contrast to halogen, LED‟s, produce visible
light by quantum mechanic effects. LED‟s
comprise a combination of 2 different
semiconductors, the „n-doped‟ and the „p-
doped‟ type. N-doped semiconductors have an
excess of electrons while P-doped
semiconductors require electrons, resulting in
electron „holes‟.

 In contrast to halogen, LED‟s produce light
with a narrow spectral distribution. This is
the main difference between light produced
by LED‟s and other light sources, as lights of
selected wavelengths can be preferentially
produced using LED‟s with appropriate band
gap energies. The spectral output of gallium
nitride blue LED‟s falls conveniently within
the absorption spectrum of the
comphoroquinone photoinitiator (400-500 nm)
present in light activated dental materials.

 The LED light used in this study (3M ESPE Elipar,
Freelight 2) has a single high intensity LED. In
contrast to conventional LED‟s a high intensity LED
uses a substantially larger semiconductor crystal,
which increases both the illuminated area and the
light intensity.
 In this study it was found that the shear bond
strength of the bracket bonded by the LED LCU
containing a single LED was comparable to the shear
bond strength of brackets bonded with halogen
LCU‟s(8.30+-1.51 and 8.89+-2.46 respectively).
 It has been suggested that bond strengths between 8
and 9 MPa are sufficient to withstand normal
orthodontic forces

 The ARI‟s suggested that most of the
composite remained on the tooth after
bracket debonding, regardless of light curing
type.
 The present study brings into significance the
fact that even though it has been previously
stated by Fujibayashi & Dunn & Bush that
lower the number of LED‟s in the LCU the
lower would be the performance, the single
LED LCU that was used in the present study
has given comparable bond strengths.

 With comparable shear bond strength
of the LED LCU‟s with the halogen LCU‟s
as found in this study the LED‟s have
certain advantages over halogen LCU‟s.
They are cordless, smaller and lighter
with estimated lifetime of over 10000
hrs. Additionally they have low
maintenance costs, and half the heat
production of halogen lights.

Conclusion
Based on the recorded data and the statistical
analysis the following conclusions were drawn: -
 There is no statistically significant difference in the
shear bond strength of the two groups.
 However, since the LED Light Curing Unit used in this
study contained only a single LED which is a
technological advancement over the previous LED
Light Curing Units containing multiple LED‟s the
comparable bond strengths become significant.
 The ARI scores showed no significant difference

For more details please visit

Comparison of light emitting diode curing unit and halogen based light curing unit for the polyme /certified fixed orthodontic courses by Indian dental academy

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (20)

Destacado

Destacado (18)

Similar a Comparison of light emitting diode curing unit and halogen based light curing unit for the polyme /certified fixed orthodontic courses by Indian dental academy

Similar a Comparison of light emitting diode curing unit and halogen based light curing unit for the polyme /certified fixed orthodontic courses by Indian dental academy (20)

Más de Indian dental academy

Más de Indian dental academy (20)

Último

Último (20)

Comparison of light emitting diode curing unit and halogen based light curing unit for the polyme /certified fixed orthodontic courses by Indian dental academy