Biosci. Biotech. Res. Comm. 10(3): 564-570 (2017)
Evaluation of two types of bleaching gel and light
source on whitening of teeth
Baharan Ranjbar Omidi
, Mohammad Nouri
and Negin Farahmandpour*
Assistant Professor, Dental Caries Prevention Research Center, Qazvin University of Medical Sciences,
Qazvin, Iran
Dentist, Tehran Iran
Restorative Dentistry Specialist, Kermanshah, Iran
Today, increasing desire for tooth brightening, make bleaching gel and light sources as a popular method for tooth
whitening. The aim of this study was effect of combination of bleaching gel and light source on the teeth whitening.
In this study 60 healthy human anterior teeth were randomly dividedin three groups (n=20). The  rst groupwas with-
outlight, the second one LED andon the third group QTH light was used. Each group was divided into two subgroups
whichhad two types of hydrogen peroxide bleaching gelsincluding 37.5% Pola of ce and 40% Opalescence Boost
which were applied to them. The primary colors of teeth were measured, and then kept intea (200ml) for 7 days. After
that each tooth color was measured for the second time. The teeth were bleached according to the protocol of each
group: Immediately, after 3, 7 and 30 days they were measured by spectrophotometer. Data were analyzed by statisti-
cal software SPSS 20 and One-way ANOVA and Tukey testin alpha 0.05. Bleaching effectiveness of QTH signi cantly
was increasedin both of bleaching gels as compared to LED and without using of light, at different times: instantly,
3 days and 7 days after bleaching, a month after bleaching, signi cant differences between the different methods
was not seen. The results of this study showed thatin-of ce bleaching, with or without light is an effective method
of beaching. QTH Light in the short term (one week) showed signi cant impact on teethwhitening in both bleach gel.
However, within a month therewere no signi cant differences in all groups.
*Corresponding Author:
Received 24
July, 2017
Accepted after revision 26
Sep, 2017
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DOI: 10.21786/bbrc/10.3/34
Baharan Ranjbar Omidi et al.
In recent years, cosmetic dentistry has become an
important part of restorative dentistry. In all ages,the
teethappearances for patients are one of important
aspects which in uences on satisfaction of them.Desire
of having a whiter tooth has increased due to attention
of people to this novel that brighter teeth are healthier
and morestylish (Barghi, 1998). The bleaching is very
effective on teeth with high Hue and yellow tint (Ishi-
kawa‐Nagai, Terui, Ishibashi, Weber, & Ferguson, 2004).
In fact, dental bleaching materials are oxidizing materi-
als which difference in various techniques still stay con-
troversial (Izquierdo-Barba, Torres-Rodríguez, Matesanz,
& Vallet-Regí, 2015) .
Today, several bleaching methods are used includ-
ing: in-of ce professional, in-home professional (dentist
supervised take-home) and products without a prescrip-
tion (over-the-counter) (Caneppele, 2013). To speed up
the bleaching process, increasing the concentration of
chemicals or use different light devices recommended,
(Sulieman, Addy, MacDonald, & Rees, 2004), (Buchalla
& Attin, 2007). Some advantages of in-of ce techniques
like prevention of swallowing and contacting with oral
soft tissue, reducing treatment time and controlling of
the healing process make it as a suitable technique for
most patients compared to other techniques (Luk, Tam,
& Hubert, 2004), (Tay, Kose, Loguercio, & Reis, 2009).
Two important factors in estimating the teeth whiten-
ing product performance are peroxide concentration and
the duration of its application. Studies have shown that
higher concentrations of peroxide is required a smaller
amount of gel (Sulieman et al., 2004). In today’s in-
of ce bleaching carbamide peroxide and hydrogen per-
oxide are used mainly by heat or light-activated devices
to accelerate the process of bleaching teeth (Sulieman
et al., 2004), (Zhang et al., 2007). Most studies have sug-
gested that light cure accelerated the degradation of per-
oxide (by increasing temperature) which led to thefor-
mations of higher free radicals(Sulieman et al., 2004),
(Joiner, 2004), (Lima et al., 2009). today various light cure
devices like Light-emitting diode(LED), halogen lamp,
plasma arc lamp(PAC) are available, however, applica-
tion of heat, light or laser devices should not be more
than 5.5°C temperature due to preventing pulp chamber
damage(Buchalla & Attin, 2007). Although, in recent
years the use of laser bleaching is generally available as
an energy source but LED require nearly low cost, and less
energy (Kurachi, Tuboy, Magalhães, & Bagnato, 2001).
There is controversy about the effectiveness of different
light on teeth bleaching. although some researchers have
reported bene ts,however others showed no effects on
bleaching, (Ishikawa‐Nagai et al., 2004, Lima et al., 2009,
Polydorou, Wirsching, Wokewitz, & Hahn, 2013).
Polydorou et al. (2013) have reported that QTH is
more effective than laser bleaching, while Hahn et al.
(2013) did not investigate any improvement with LED
and laser in bleaching teeth. In another study which
evaluated six different light resulted that the diode laser,
QTH and LED had a signi cant impact on Teeth Whit-
ening (Domínguez et al., 2011) Similarly, Kossatz et al.,
compared effect of LED and laser on 35% hydrogen per-
oxide bleaching gel and reported no signi cant differ-
ences (Kossatz et al., 2011).
In another study where 35% hydrogen peroxide was
used, LED, QTH, plasma arc lamp, argon laser was used
and they have been reported no effect on tooth bleach-
ing (Lima et al., 2009). Clinician should be aware of any
risks regarding to bleaching process (Alqahtani, 2014).
The aim of this study was to evaluate effect of LED and
QTH light on teeth whitening, since using of any type
of light as an additional device is questionable in-of ce
In vitro experimental study, the 60 human anterior teeth
were selected. First teeth were checked for any defects,
cracks, decays or  llings. Then selected teeth after scal-
ing, brushing (for 10 seconds with pumice and water
by prophylaxis rubber cup then cleaned with ultrasonic
cleaner, and stored for one week in the solution0.1%
Thymol at 4°C. While the entire of laboratory work used
gloves, surgical masks and face shields (Kohn et al., 2003),
(Kumar, Sequeira, Peter, & Bhat, 2005), (Lolayekar, Bhat,
& Bhat, 2007). The teeth were  xed in acrylic resin into
the mold which the angle of light cure is perpendicular to
the labial surface of the teeth. By creating four small holes
(depth of about 0.5 mm) with bur (No#1) created square-
shaped area (with dimensions of approximately 3 mm) in
the middle third of the labial teeth (Figure 1).
Labial surface of teeth were cleansed and brushed.
Then all the teeth stored in Ringer (Ringer’s Infu-
sion, Shahid Ghazi Pharmaceutical Co., Tabriz-Iran).
The teeth are completely dry with gauze and randomly
divided into three groups (20 = n) with different bleach-
ing protocols:The  rst group without light, the second
LED light cure system (Woodpecker Dental LED.D Cur-
ing Light, China), the third group QTH light cure system
(Coltolux 75 Curing Light-Coltene/Whaledent, USA).
Each group divided into two subgroups of 10 teeth the
rst subgroup, hydrogen peroxide 37.5% Polaof ce +
(SDI, Australia) and in the second subgroup of hydrogen
peroxide 40% Opalescence Boost (Ultradent Products
Inc, South ordan, UT USA) was used ( gure 1).
The samples were placed on holder plate, white paper
Leneta. Light source positioned at an angle of 45 degrees
Baharan Ranjbar Omidi et al.
FIGURE 1. Preparation of tooth for bleaching
to a line perpendicular to the surface and spectropho-
tometer device (KONIKA MINOLTA CS2000, Japan)
with an approximate angle of zero degrees relative to a
line perpendicular to the sample surface and they were
placed approximately 70 cm.
The device was set at 0.2 degrees. This angle makes
circular area with 2.4 mm in diameter in specimens.
Three measurements were taken for each sample and
average measurements were reported. Measurements
were conducted under laboratory conditions at approxi-
mately 25°C. The primary color of the teeth (M1) was
measured by spectroradiometer. for changing the color,
teeth were retained for 7 days in a mixture of tea (tea
bags Golestan) obtained by the method Sulieman et al
(Sulieman, Addy, & Rees, 2003). Teethwere brushed to
remove pigments.
Then the teeth color was measured for the second
time (M2). The teeth were bleached in all 3 groups
according to the protocol set for each group, while the
distance to the labial surface of the teeth were 5 mm to
light tip. The intensity of light rays was measured before
the start of each bleaching cycle using Radiometer (QTH
= 370mw/cm2, LED = 380mw/cm2) to ensure constant
light output is achieved at all stages of bleaching. In all
three groups, the use of bleaching gel and light were
performed exactly according to the manufacturer’s
instructions. A thin layer of (1 mm) Polaof ce bleaching
gel was placed on the labial surface of the teeth for 8
minutes, then using clean cotton it was cleansed by gel
then was stained with fresh gel.
This process was repeated three times (according to
the manufacturer’s instructions) and at the end all clear
gel, rinsed with water and dried and the bleaching gel
Opalescence Boost, a thin layer (mm1) of gel on the
labial surface of teeth put for 20 minutes (according to
the manufacturer’s instructions) and at the end all clear
gel, rinsed with water and dried. Light application in
groups 2 and 3 were three 8-minute for Polaof ce and a
20-minute period to Opalescence Boost.
Tooth color was measured immediately after bleach-
ing (M3). Samples were put on Ringer with 37 ° C which
switching with new Ringer every day then he teeth color
were measured after 72 hours (M4), 1 week (M5), one
month (M6). All stages of tooth color measurement sys-
tem were performed by spectrophotometer according to
CIE L*a*b* (Commission Internationale de I’Eclairage’s)
(Tavares et al., 2003). According to the ADA (American
Dental Association) tooth color measurement, device
located in the middle third of the labial surface of the
teeth ( gure 2).
Tooth bleaching ΔE values are directly in uenced
by the index tooth color difference between the initial
measurement and other measurements are shown and
using the formula: E = [(ΔL *) 2+ (Δa *) 2+ (Δb *) 2] 1 / 2Δ
(Δa = a * post - a * baseline, Δb = b * post - b * baseline,
ΔL = L * post - L * baseline) was achieved. Data were
collected with 20 SPSS statistical software and ANOVA
test value of P (P<0.05) were obtained and studied under
Tukey test was used pairs of groups.
ΔE averages and standard deviations for all groups and
in all stages after bleaching compared to after being in
tea shown in Table 1.
Baharan Ranjbar Omidi et al.
Signi cant difference between ΔE of groups (at times
immediately, three days and one week after white) one-
way ANOVA test was observed ( P-Value <= 0.05). ΔE
signi cant difference between the groups was observed
one after month the bleaching. (P = 0.57)
Comparing of pairs of groups by test Tukey, both of
bleaching, a signi cant difference in the effectiveness
of bleaching (ΔE) with the use of light QTH compared to
LED and without the use of light (in the time immedi-
ately after bleaching, three days and 7 days after bleach-
ing) showed that although a month later bleaching of
teeth whitening showedsigni cant difference in ef cacy
between any of these groups (Table 2).
To achieve lightening of teeth in a short time, bleach-
ing technique in the of ce, using a high concentration
hydrogen peroxide gel, with and without the use of light
is recommended (Luk et al., 2004), (Roberto et al., 2011).
Some studies have emphasized that light can be used
to catalyze the hydrogen peroxide, thus accelerates the
bleaching process (Dostalova et al., 2004), (Tavares et al.,
2003). This issue is still discussed in articles and reviews.
In the present study, the teeth ΔE after tea, signi cantly
increased (ΔE in all groups was higher than 3.3 means
the discoloration caused by tea in all groups were detect-
able by eye) ΔE, difference before and after exposure to
tea among all groups was not signi cant.
In this study, ΔE changes in groups (immediately, three
days and one week after bleaching), was signi cant,so
the applicationof Polaof ce with QTH showed whitening
effect. In the present study, the Tukey test results showed
that in both bleaching agent (Opalescence and Pola
of ce), QTH Light application signi cantly increased the
effectiveness of bleaching component compared to LED
or without light, immediately after bleaching teeth, 3 days
and 7 days after bleaching, Because QTH heat transfer
capability to the teeth is more than LED. QTH produce
more heat than light on the tooth surface which can form
groups that cause more tooth dehydration (Liang et al.,
2012). Also, previous studies which have examined differ-
ent types of light reported that QTH effect was remarkably
higher in immediately after bleaching (Sulieman et al.,
2005, Polydorou et al., 2013 Liang et al., 2012).
FIGURE 2. Evaluation of samples by spectrophotometer
Table 1.
1 month after
7days after
3 days after
Immediately after
6/74 (1/12) 3/92 (0/82) 4/95 (0/9) 3/8 (0/57) Polaof ce+without light
9/83 (2/78) 3 (0/8) 3/82 (0/77) 2/89 (1) Opalescence Boost without light
7/25 (0/88) 4/78 (0/49) 5/39 (0/58) 3/57 (0/56) LED Polaof ce+
7/17 (1/08) 98/3 (0/53) 4/21 (0/37) 3/28 (0/54) LED Opalescence Boost
6/58 (1) 10/84 (1/11) 10/3 (1/09) 8/82 (1/21) QTH Polaof ce+
6/32 (0/81) 8/44 (0/45) 8/08 (0/45) 7/28 (0/4) QTH+Opalecensce Boost
Signi cant difference between ΔE of all groups after being in tea using one-way ANOVA test was observed. (P = 0.47)
Baharan Ranjbar Omidi et al.
In this study, ΔE difference was not statistically sig-
ni cant a month after bleaching,in all groups, ΔE was
more than 3.3 which teeth bleaching was still detectable
after a month with eye. Tukey test results compare pairs
of groups after one month however no signi cant dif-
ference was observed between ΔE. This means that after
a month no statistically signi cant differences between
the different methods of bleaching as observed similar
results from studies have concluded the same, (Poly-
dorou et al., 2013) and (Alomari & El Daraa, 2010).
In this study, all groups showed obvious effect imme-
diately after bleaching, though there is noconsiderably
differences between one and three months. Although
some studies have reported the effects of light on tooth
whitening (Luk et al., 2004), (Domínguez et al., 2011),
(Ontiveros & Paravina, 2009), (Wetter, Barroso, & Pelino,
2004), but many studies have focused Light extremely
ineffectiveness on teeth whitening (Lima et al., 2009),
(Polydorou et al., 2013), (Roberto et al., 2011),(Bernardon
et al., 2010), (Marson, Sensi, Vieira, & Araújo, 2008),
(Mondelli, Francisconi, Almeida, & Ishikiriama, 2012),
(Hein et al., 2003), (Papathanasiou, Kastali, Perry, &
Kugel, 2002).
Although, in this study QTH had greater effectiveness
after 7 days, but after one month treatment relapse was
observed. In Polydorous study, the use of QTH for each
tooth was 4times in 8 minutes (Polydorou et al., 2013),
while in Liangs study, two sessions with7 days interval
3 times of 10 minute were applied (Liang et al., 2012).
So in both of these study groups, teeth were exposed
longer to QTH light. Relapse in treatmentin the Poly-
dorous study only occurred in a month after treatment
QTH group (Polydorou et al., 2013), which is similar to
the results of our study, while both groups in the Liangs
study showed relapse after a week with or without light
cure system (Liang et al., 2012).
For other groupsin the Polydorous study, relapse
occurred after 3 months (Polydorou et al., 2013), while
in Liangs it happened sooner (Liang et al., 2012). These
results can be explained by a lower concentration of
bleaching agent used in study (32% Beyond II Advanced
Formula Whitening Gel) compared with current study
(37.5% Polaof ce and 40% Opalescence Boost) and
Polydorou study (38% Opalescence Boost), although this
difference is negligible. Tooth dehydration can cause
brighter teeth immediately after bleaching so this can be
increased by the heat transferred to the teeth (Luk et al.,
2004). Tooth color becomes lighter during dehydration
however returning to normal mode after rehydration.
During in-of ce bleaching, many factors could cause
dehydration teeth, including teeth isolation, heat from
the light (Liang et al., 2012).
According to the results of this study at any time
after the teeth bleaching, a signi cant difference in the
effectiveness of the bleaching was observed regardless
of light cure application, Which could be due to the
concentration of these two bleaching gel (37.5% Pola
of ce + and 40% Opalescence Boost). Also, according
to the manufacturer’s instructions, each of bleaching
gel which hadless concentrations, longer exposure in
the tooth surface (37.5% Polaof ce 3 times for 8 min-
utes and 38% Opalescence Boost only 20 minutes)so the
effectiveness of bleaching materials weresimilar. Scien-
ti c community believe that light cure bleaching effec-
tiveness occurs due to reversible dehydration (Polydorou
et al., 2013) so in long-term we should expect relapse
of treatment. The results obtained in this study during
a month is not only con rmed the stability of tooth
Table 2.
After3 days
After 7days
After one
Polaof ce with Opalescence Boost Without light 0.450. 350. 440.31
Polaof ce with Opalescence Boost LED0.710.10. 280. 95
Polaof ce with Opalescence Boost QTH0.240.080. 080. 84
Without light Polaof ce + LED Polaof ce+0.980.930. 750. 93
Without light Polaof ce + QTH + Polaof ce*0.001*0.001*0.000. 99
Polaof ce + LED with QTH + Polaof ce +*0.00*0.002*0.000. 89
Without light + Opalescence Boost LED + Opalescence Boost0.920.870.50. 55
Whithout light + Opalescence Boost QTH + Opalescence Boost*0.001*0.00*0.000. 36
LED + Opalescence Boost QTH + Opalescence Boost*0.001*0.00*0.000. 94
ΔE Changes in groups at different times after bleach in arein Charts 1, 2 and 3.
Baharan Ranjbar Omidi et al.
color But also enhances the white color of the teeth in
both LED and without light cure system. The Greenwall
hypothesis is that during bleaching, teeth get aerated by
oxygen and oxidation processes caused by dehydration
change the visual characteristics of the teeth. This partly
is explained why teeth become whiter in this study after
a month. For this reason, after a two-week period, scat-
tered oxygen rehydrate and teeth show their true colors
(Greenwall, 2001).
While in current study, the majority of teeth bleached
within a month except QTH group which heat lead
to improve the effectiveness of treatment in few  rst
days,another parameter that can affect the outcome of
the study is the viscosity of bleaching gel. Opalescence
Boost was replaced with Opalescence Xtra Boost some
time ago, although, manufacturer claim no chemi-
cal change, but the foundation and consistency has
changed; the new bleaching gel is more viscous than
before. The composition and sticky bleaching gel affect
on the release of hydrogen peroxide which impact on
bleaching process (Christian Hannig, Weinhold, Becker,
& Attin, 2011), (Hannig, Zech, Henze, Dreier, & Attin,
2005), (Thitinanthapan, Satamanont, & Vongsavan,
1999). high viscosity bleaching agents compared to low
one shows higher peroxide emissions (Christian Hannig
et al., 2011).
This change in viscosity after bleaching can cause
different behavior because the viscosity of the material
affects the free movement of peroxide (peroxide release
kinetics). The clinical perspective, highlights light cure
effect on the con dence and satisfaction of patients to
continue bleaching. After a month there was no signi -
cant difference between the three groups and this shows
that bleaching by light relapse sooner and do not main-
tain long-term effect.
According to data obtained from this study, the fol-
lowing results can be obtained. In of ce- bleaching,
with and without light, is effective to bleach teeth.
In both type of bleaching, bleaching effectiveness of
QTH increases signi cantly compared to LED and with-
out the use of light, at times of instantly, 3 days and 7
days after bleaching.Light cure does not lead to increase
effectiveness of bleachingwithin a month.
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