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COMPARISON OF SHEAR BOND STRENGTH OF ORTHODONTIC METAL AND
CERAMIC BRACKETS BONDED USING MONOWAVE AND POLYWAVE LIGHT
EMITTING DIODE CURING UNITS - AN INVITRO STUDY
Dissertation submitted to
THE TAMIL NADU DR. M.G.R. MEDICAL UNIVERSITY
In partial fulfilment for the degree of
MASTER OF DENTAL SURGERY
BRANCH - V
ORTHODONTICS AND DENTOFACIAL ORTHOPEDICS
APRIL - 2017
DECLARATION BY THE CANDITATE
TITLE OF DISSERTATION
Comparison of shear bond strength of orthodontic metal
and ceramic brackets bonded using monowave and
polywave light emitting diode curing units – An invitro
study
PLACE OF STUDY K.S.R. Institute of Dental Science and Research.
DURATION OF COURSE 3 Years
NAME OF THE GUIDE Dr. K.P. Senthil Kumar, M.D.S.,
HEAD OF THE DEPARTMENT Dr. K.P. Senthil Kumar, M.D.S.,
I hereby declare that no part of the dissertation will be utilized for gaining financial assistance
for research or other promotions without obtaining prior permission of the Principal, K.S.R
Institute of Dental Science and Research, Tiruchengode. In addition, I declare that no part of
this work will be published either in print or electronic without the guide who has been
actively involved in dissertation. The author has the right to reserve for publish of work
solely with prior permission of the Principal, K.S.R Institute of Dental Science and Research,
Tiruchengode.
Head of the Department Signature of candidate
CERTFICATE BY THE GUIDE
This is to certify that dissertation titled “COMPARISON OF SHEAR BOND STRENGTH
OF ORTHODONTIC METAL AND CERAMIC BRACKETS BONDED USING
MONOWAVE AND POLYWAVE LIGHT EMITTING DIODE CURING UNITS” is a
bonafide research work done by Dr.R.B. Sri Meenakshi, in partial fulfillment of the
requirements for the degree of MASTER OF DENTAL SURGERY in the specialty of
Orthodontics and Dentofacial Orthopedics.
Date:
Place:
Signature of the Guide
Dr. K.P. Senthil Kumar, M.D.S.,
Professor.
K.S.R. Institute of Dental
Science and Research,
Tiruchengode.
ENDORSEMENT BY THE H.O.D, PRINCIPAL/ HEAD OF THE
INSTITUTION
This is to certify that the dissertation entitled “COMPARISON OF SHEAR BOND
STRENGTH OF ORTHODONTIC METAL AND CERAMIC BRACKETS BONDED
USING MONOWAVE AND POLYWAVE LIGHT EMITTING DIODE CURING UNITS
– AN INVITRO STUDY” post graduate student (M.D.S), Orthodontics and Dentofacial
Orthopaedics (Branch -V), KSR Institute of Dental Science and Research, Tiruchengode,
submitted to the Tamil Nadu Dr. M.G.R Medical University in partial fulfilment for
the M.D.S degree examination (April 2017) is a bonafide research work carried out by
him under my supervision and guidance.
Seal and signature of H.O.D Seal & signature of Principal
PROF. DR. K.P. SENTHIL KUMAR, M.D.S.,
PROFESSOR AND GUIDE
PROF. DR. G.S. KUMAR., M.D.S.
PRINCIPAL
K.S.R. INSTITUTE OF DENTAL SCIENCE AND RESEARCH
TIRUCHENGODE
` TABLE OF CONTENTS
S.NO
TITLE
PAGE NO.
1
INTRODUCTION
1
2
AIMS AND OBJECTIVES
4
3
REVIEW OF LITERATURE 5
4
MATERIALS AND METHODS 26
5
STATISTICAL ANALYSIS 38
6
RESULTS 39
7
DISCUSSION
44
8
SUMMARY AND CONCLUSION 49
9
BIBLIOGRAPHY 50
10
ANNEXURE 59
LIST OF FIGURES
FIGURE
NO: TITLE
PAGE NO:
1
Metal , Ceramic brackets used in the study
32
2
Monowave and Polywave LED light, Bonding materials 33
3
Teeth samples mounted in acrylic blocks
34
4
Light curing method
35
5
Universal testing machine and bond strength test 36
6
Optical stereomicroscope and the sample specimen
37
7
Stereomicroscopic picture to determine ARI
37
LIST OF TABLES
S.NO
Title
PAGE
NO.
1
Classification of samples into four groups
28
2
Shear force / peak load values and the bond strength values of
all four groups 39
3 Mean and SD of shear bond strength values in mega pascals
( MPa) for all groups 40
4 Comparison of shear bond strength of metal brackets cured with
monowave LED and polywave LED 41
5 Comparison of shear bond strength of ceramic brackets cured
with monowave LED and polywave LED 41
6 Comparison of shear bond strength of metal and ceramic
bracket cured with monowave LED 41
7
Comparison of shear bond strength of metal and ceramic
bracket cured with polywave LED 41
8
Comparison of shear bond strength of metal and ceramic
brackets 42
9
Frequency distribution of the Adhesive Remnant Index ( ARI )
and enamel fracture of the 4 groups evaluated 42
ACKNOWLEDGEMENT
With immense gratitude and respect, I thank Professor Dr.K.P. Senthil Kumar,
M.D.S., Professor and Head of the department and my guide for his valuable guidance,
support and encouragement throughout the study.
I owe my thanks and great honour to Professor Dr.S. Tamizharasi,M.D.S., for
helping me with her valuable and timely suggestions and encouragement.
I am grateful to my department staffs Dr.M .Karthi,M.D.S., Dr.S. Raja,M.D.S., Dr.K.
Prabhakar,M.D.S., for their guidance and support.
My sincere thanks to Professor Dr.G.S. Kumar,M.D.S., Principal, KSR Institute of
Dental Science and Research, for his kind support and encouragement and to chairman of
KSR group of institutions,Thiru Lion.Dr.K.S. Rangasamy, MJF for providing me the
opportunity to do postgraduation in this institution.
I take this opportunity to express my gratitude to my seniors and juniors, friends, non-
teaching staffs and colleagues for their valuable help and suggestions throughout this study.
I offer my heartiest gratitude to my family members for their selfless blessing.
I seek the blessings of the Almighty, the God, without whose benevolence, the study
would not have been possible.
Introduction
Page 1
INTRODUCTION
Orthodontic treatment has revolutionized with the development of new inventions and
innovations in materials and techniques. Bonding is an important orthodontic milestone that
replaced the arduous task of banding and then the evolution of fixed appliance became
popular. The ability to bond orthodontic brackets has reduced patient chairside time, reduced
the band space that needed to be closed at finishing, improved the esthetics and aided in the
improvement of oral hygiene. Direct bonding became popular after the contributions of the
pioneers such as Michael G. Buonocore (1955 )16
suggested a surface acid treatment of
enamel by 85% phosphoric acid for 30 seconds similar to that used in the paint industry to
render the enamel more receptive to adhesion. The basis of bonding material, the Bisphenyl
Glycidyl Dimethacrylate ( BISGMA) resin was introduced in 1956 by Rafael L. Bowen
which led to the first successful production of a composite resin for filling teeth. Newman
(1965 ) introduced direct bonding as a viable clinical technique and then orthodontic bonding
developed as an excellent alternative to banding.
The chemically activated curing system has limitations such as the short working time for the
operator and the light curing systems has advantages such as extended working time to
position brackets and clean up flash and ability to place archwires immediately. In the
development of light curing units due to safety and efficacy concerns the UV curing of
restorative materials was replaced in 1978 by visible light curing and then quartz tungsten
halogen units dominated the market for almost two decades and around 1995 Robin Mills
stated the possibility of LED units for curing24
and also QTH and UV units were heavy and
bulky compared to today‟s LED unit .
Introduction
Page 2
The quartz tungsten halogen produced a broad emission spectrum ( 300 – 1000 nanometer
range ) most of the light emitted in the UV and infra red regions that are outside the spectral
absorption of camporoquinone(CQ), the principal resin photoinitiator used in dentistry61
must
be blocked out using filter. QTH units gets hot and requires cooling fans. Plasma arc curing
and argon laser curing became popular because of rapid curing3,4
and benefits of saving time
but they were very expensive to purchase and maintain and are large units. Now small LED
units are replacing their QTH and PAC Predecessors.
In the generations of LED , early in first generation LED units delivered a narrow spectral
emission compared with QTH units and they require longer exposure times because of their
low radiant power output, manufactures designed LCU to fit multiple LED emitters ( some
had 64 LEDs in gun style)72
, some manufacturers managed to have nineteen LED in pen
style LED LCU which is battery powered. The second generation units resolved this problem
by using smaller but much powerful blue LED chips.
Further development on LCUs has seen the introduction of broad spectrum “Polywave” LED
LCUs that use upto four LED emitters each producing different wavelengths of light. These
units are designed to simulate the broader spectrum of QTH and PAC units for activating
materials containing alternative photoinitiators1. The benefits of broad spectrum polywave
LED units relative to blue LED „ monowave‟ unit is topic for debate given the majority of
practising dentists use exclusively CQ – initiated resin based materials. As Camporoquinone
has an intense yellow colour due to its absorption properties, alternative initiators are for
instance employed in the formulations of composites in bleach shades and colourless
protective varnishes. Polywave units may enhance the polymerization and surface properties
of resins that contain alternative photoinitiators in addition to CQ such as Lucirin TPO. This
photoinitiator has gained popularity because it completely bleaches out after the light reaction
is finished. The peak sensitivity of Camporoquinone is near 470 nm in the blue wavelength
Introduction
Page 3
range whereas for Lucirin TPO the peak absorption is around 390 nm nearing the UV range.
Polywave LED achieves a spectral peak at approx. 410 nm and 470 nm which covers the
wavelength range of 380 to 515 nm. In terms of light intensity their high intensity range
nears that of Plasma arc curing, so curing time can be reduced .
However , the output from current polywave LED units is not spatially or spectrally uniform
across the face of the light tip70
, also the shorter violet wavelengths do not penetrate through
the resin based composite as deeply as the blue light , the depth of cure may not be uniform.
Eventhough polywave LED is beneficial for a practitioner for curing not only the
conventional composite but also other restorative materials or liners or adhesives containing
non camporoquinone initiators, its orthodontic efficacy is need to be evaluated, so my study
is undertaken to compare the shear bond strength of orthodontic brackets bonded using the
second generation monowave LED with the newer generation polywave LED. Nowadays
ceramic brackets are an esthetic alternative to conventional SS metal brackets and because of
its high light transmission capacity through the bracket , the high intensity curing light can be
very efficient in curing ceramic brackets than the SS metal brackets. So in this study the shear
bond strength of ceramic brackets cured with monowave and polywave LED curing lights
are also evaluated.
Aim and Objectives
Page 4
AIM OF THE STUDY
The aim of the invitro study is to evaluate and compare the shear bond strength of
orthodontic metal and ceramic brackets bonded using monowave and polywave light
emitting diode curing units .
OBJECTIVES OF THE STUDY
1) To evaluate the shear bond strength of metal (stainless steel) and ceramic brackets
(polycrystalline) bonded using two different light emitting diode curing units
(monowave or single peak polymerization LED which is a second generation LED
and polywave LED or dual peak polymerization LED which is a third generation
LED).
2) To compare the shear bond strength of brackets bonded using monowave and
polywave LED curing units.
3) To compare the shear bond strength of metal and ceramic brackets.
4) To calculate the Adhesive Remnant Index scores for all four groups in this study.
Review of literature
Page 5
REVIEW OF LITERATURE
Chun-Hsi Chung, Blair W. Fadem, Harvey L.Levitt, Francis K. Mante13
(2000) did a
study to evaluate the effects of 2 adhesion boosters, Enhance LC and All-Bond 2, on the
shear bond strength of previously debonded/sandblasted brackets and of new brackets. In this
study 60 new brackets were divided into three groups and 60 sandblasted brackets were
divided into three groups. Group 1:Without use of booster (no booster); Group 2:Rebonded
brackets/no adhesion booster; Group 3:New bracket/ Enhance LC; Group 4:Rebonded
brackets/Enhance LC; Group 5:New bracket/All-Bond2; Group 6:Rebonded brackets/All-
Bond 2.The bond strength test was done using an universal testing machine and the results
showed that no difference was found among the 3 groups using new brackets and without use
of adhesion booster, sandblasted rebonded brackets yield significantly less bond strength
than new brackets and All-Bond 2 significantly increased bond strength where as Enhance
LC failed to increase bond strength when using sandblasted rebonded brackets.
Travis Q.Talbot, et al60
(2000) evaluated the effect of argon laser irradiation on shear bond
strength of orthodontic brackets and also investigated for their ability to confer
demineralization resistance on enamel. Three different laser energies (200,230,300mW) were
used in this study at 3 unique time points (before ,during or after bracket placement). One
hundred and fifty human posterior teeth were randomly assigned to 10 groups of 15 each-9
experimental groups and 1control group. The results showed that the mean bond strength was
significantly different between all 3 bracket placement groups and also the mean bond
strength of teeth lased after bonding was significantly higher than the control group.
Review of literature
Page 6
Larry J.Oesterle, et al33
(2001) did a study to test the efficiency of a xenon plasma arc light
versus a conventional tungsten-quartz halogen light in producing the bond strength for
orthodontic brackets. The adhesive used in this study were 3 light polymerized composite
resins such as TransbondAPC, the fluoride releasing light bond and another composite which
was developed for use with the xenon plasma arc light and the curing light used in this study
were the [Apollo 95E] xenon plasma arc light and the [Optilux 401] light a conventional
tungsten-quartz halogen light. The result of this study showed that the xenon light produced
equivalent bond strength at 3,6,9 seconds compared to tungsten-quartz halogen light of 40
seconds. However the bond strength of xenon plasma arc curing light with long exposure
showed higher values.
Maria Francesca Sfondrini, et al34
(2001) evaluated the shear bond strengths of a composite
resin and a resin modified glass ionomer cured using a conventional visible light unit and a
xenon arc light unit . One hundred and twenty freshly extracted bovine permanent mandibular
incisors were randomly divided into 1 of 8 groups; each group consisted of 15 specimens.
Two orthodontic light cured adhesive systems were evaluated. TransbondXT( a conventional
composite resin) and a Fujiortho LC(GC America) - a resin modified glass ionomer adhesive.
After testing in an universal testing machine the results showed that the bond strength of
composite resin was significantly higher than Fuji GC but no statistically significant
differences were found between the control group and those cured with visible light and
similarly no statistically significant differences were found between the control group and
those bonded with the xenon plasma arc curing system.
Ross S. Hobson, et al53
(2001) evaluated the bond strength of moisture insensitive primer
under dry, moist and blood contamination conditions. In this study ninety human premolars
were bonded in 3 equal groups and then shear bond strength was recorded using an Instron
Review of literature
Page 7
testing machine . The results of the study showed that higher bond strength for dry bonding
than moist bonding. Low bond strength for blood contaminated group but all the 3 groups had
required clinical bond strength, so Transbond MIP can be used for bonding on moist or blood
contaminated conditions.
Arndt Klocke, et al3(2002) compared the plasma arc curing lights with the halogen light by
an invitro investigation to evaluate the bond strength with two commercially available plasma
arc lights with curing time of 2 seconds and 6 seconds. 150 extracted human teeth of 75
premolars and 75 incisors were bonded with a composite adhesive. Five groups of 30 teeth
each involving 15 premolars and 15 incisors were formed. The bond strength testing was
performed in an universal testing machine . The results showed that a substantial reduction in
curing time was possible with plasma arc curing light but in case of premolar brackets, the
lowest bond strength values were found for plasma arc curing light with curing time of 2
seconds than those cured for 6 seconds whereas for incisor brackets 2 seconds of curing time
might be adequate to achieve an acceptable bond strength.
Larry James Evans, et al32
(2002) did a study to evaluate the effects of different curing times
, light sources and light guides on shear bond strength of orthodontic brackets bonded with
Transbond XT (3M Unitek,Monrovia,Calif) to bovine enamel. 240 bovine mandibular
incisors were randomly divided into 16 groups. The shear bond test was done using an
universal testing machine. The bond strength values were high in 24 hour groups compared
with the 5- minute shearing groups but statistically there were no differences. They concluded
that the power slot and turbo tip light guides with their collimation of visible light to increase
its intensity can be advantageous for curing resins.
Arndt Klocke, et al4(2003) had done an investigation to evaluate the bond strength when
using a plasma arc curing light to bond polycrystalline and monocrystalline ceramic brackets.
Review of literature
Page 8
240 extracted bovine mandibular incisors are bonded with composite adhesive and curing
intervals of 1, 3,& 6 seconds were choosen and the control group was cured at 10 seconds per
bracket. The results of the shear bond strength after testing in an universal testing machine
showed higher values for monocrystalline brackets than the polycrystalline in both 1 second
and 3 second curing interval methods. The study concluded that a curing interval of 3 seconds
with plasma arc curing light is advantageous over 1 second curing interval time.
Rognvald A. Linklater, et al52
(2003) did an invivo study to identify the presence and pattern
of differences in bond failure between two types when bonding brackets with the no-mix
chemically cured orthodontic composite adhesive Right-on. Bond failure of brackets were
recorded for 108 patients undergoing fixed orthodontic treatment with total of 1531
attachments (0.018inch brackets=549, 0.022inch brackets =914, tipedge=45, bonded molar
tubes=16, buccal buttons =7). The failure rates and the survival rates of the attachments were
noted and the results of this study confirmed that invivo bond survival is not uniform for all
teeth and varies significantly between tooth types, attachment and dental arches, both in
overall failure rates and patterns of bond failure. Posterior teeth had poor survival than
anterior teeth and the mandibular teeth had poor bond survival than maxillary teeth.
Bruno Manzo , Giuseppe Liistro, Hugo De Clerck.11
(2004) did a clinical trial to evaluate
the time saved with a plasma arc curing unit over a conventional curing unit for direct
bonding of brackets with resin adhesive. 608 brackets were bonded on a contralateral
quadrant pattern in fourty five patients. The survival analysis rate of brackets were also
carried out to compare the bracket failure rate over a period of 11± 3.2 months. The curing
time for each technique is recorded. The results of the study showed that there was no
significant differences in survival time between the 2 bonding methods but the plasma arc
Review of literature
Page 9
curing light can save chair time as the curing time per bracket was significantly reduced with
this curing when compared to conventional halogen curing unit.(65±19 vs 82±31seconds).
Ingrid Hosein, Martyn Sherriff, Anthony J.Ireland21
(2004) did an investigation to
compare the enamel loss at each stage of the bonding and debonding and clean-up with the
use of a self etching primer. The 4 enamel clean-up methods used were 1)use of high speed
tungsten carbide bur, 2)a slow speed tungsten carbide bur, 3)debanding pliers and 4)an
ultrasonic scaler. In this study a planer surfometer was used to measure the enamel surface
height. The enamel loss after conventional acid etching was -2.76µm where as with self
etching primer, the enamel loss was significantly lower -0.27µm.In both the conventional and
self etch groups the most enamel loss occurred after the use of ultrasonic scaler or high speed
tungsten carbide bur and least with the slow speed tungsten carbide bur or the debanding
pliers and there was also significant difference found in ARI scores of the two groups.
Maria Francesca Sfondrini, et al35
(2004 ) did a randomized clinical trial to evaluate the
clinical performance of brackets cured with conventional halogen light and plasma arc light.
It was a split mouth study design involving 83 patients with fixed appliance. In 42 patients
,the maxillary left and mandibular right quadrants were cured where as in the rest , maxillary
right and mandibular left quadrants were cured with the plasma arc light. Curing time for
conventional halogen light is 20 seconds for each bracket (totally 717 brackets) and the
curing time with plasma arc light is 5 seconds for each bracket (totally 717 brackets). Both
groups of patients were monitored for 12 months. The datas such as number, cause and date
of bracket failure were recorded for each light curing unit. The results of the study showed
that no statistically significant differences were found between the total bond failure rate
between two curing lights and also there is no significant difference in clinical performance
Review of literature
Page 10
of the maxillary versus mandibular arches. They concluded that the advantage of plasma arc
light over conventional light curing is that plasma arc light reduces the total curing time.
Timothy Swanson, et al64
(2004) in an invitro study evaluated the relationship between the
shear bond strength of orthodontic brackets bonded to enamel and the photopolymerization
duration with three LED curing units (GC e-light,UltraLume LED-2,Ellipar FreeLight) and
one halogen based light curing unit.(Ortholux). 240 extracted molars were collected and the
brackets were bonded and the specimens were divided into 12 groups of 20 teeth. For each
curing light, the curing time of 40,20 and 10 seconds were used . The results the shear bond
strength after testing in an universal testing Machine showed higher bond strength for
UltraLume LED-2 at 40 seconds and weaker bond strength with GC e-light at 10 and 40
seconds , but the bond strength for all groups were greater than 8 MPa even with a 10 second
curing time.
Vittorio Cacciafesta, et al68
(2004) conducted a randomized clinical trial to evaluate the
performance of adhesive-precoated brackets cured with a conventional halogen light and
plasma arc light. They did a split mouth study design in which maxillary left and mandibular
right quadrants were cured with halogen lights and the maxillary right & mandibular left
quadrants were cured with plasma arc light for 15 patients and for other 15 patients the
quadrants were inverted. The study was carried out for 12 months and the number, cause,
date of bracket failure were recorded. The results of the study showed that there is no
statistically significant difference between 2 groups in the bond failure rate or in the
performance of 2 curing lights but the advantage of using plasma arc is that it can enable the
clinician to reduce the curing time.
Review of literature
Page 11
Cornelia Speer, et al14
(2005) did an invitro study to compare whether disinfecting with
cholorherxamed fluid had an influence on shear bond strength of metal and ceramic
orthodontic brackets. Composite adhesives Transbond XT(light curing) and chemical curing
composite adhesive 224 bovine permanent mandibular incisors and divided into eight groups
of 28 each. Results showed that disinfection of metal brackets had no significant change on
shear bond strength where as disinfecting ceramic brackets showed significant reduction in
shear bond strength but the bond strength values were higher than 6-8 mpa, so the
disinfection of the ceramic brackets is a suitable procedure for clinical use.
Fabio Lourenco Romano, et al17
(2005) did a study to determine the shear bond strength of
metallic orthodontic brackets bonded to enamel prepared with Transbond plus self etching
primer(TPSEP). Forty human premolars were divided into four equal groups of 10 each.
Group 1 is the control group were Transbond XT was used and in group 2 TPSEP was used
with Transbond XT and in group 3 TPSEP was used with Z-100 and in Group 4 TPSEP was
applied and the brackets were bonded with Concise orthodontic product. Here 1 to 3 groups
were light cured whereas Concise orthodontic composite is cured by chemical activation. The
brackets were debonded using a universal testing machine and the results showed that there
was no significant difference between first 3 groups and also superior to group 4. The ARI
evaluation showed that the conventionally bonded Transbond XT showed better adhesive
results than using TPSEP groups(2,3,4)
HakanTurkkahraman, H.Cenker Kucukesmen 20
(2005) compared the shear bond strength
of orthodontic metal brackets by two high power light emitting diode modes and halogen
light. Here forty five SS orthodontic bicuspid brackets were divided into three groups of
fifteen each. In first group mini LED(Satelec,Merignac,France) fast mode LED for 20
seconds and second group helioux DLX(Vivadent ETS,Schoan,Leichtenstein) soft start mode
LED for 40 seconds, third group halogen light for 40 seconds were used. The shear bond
Review of literature
Page 12
strength of fast mode LED is similar to halogen based illumination, where as soft start mode
LED yielded higher shear bond strength than the other two groups.
M Dolores Campoy, et al38
(2005) did an invitro study to evaluate the effect of saliva
contamination on the shear bond strength at different stages of the bonding brackets using
Adper Prompt L-Pop (self etching primer) and Transbond XT (resin orthodontic adhesive
system). Seventy premolars were bonded with brackets and were divided into four groups:
group 1,uncontaminated control; group 2, saliva application before priming; group 3, saliva
application after priming and group 4, saliva application before and after priming. Shear bond
strength was measured with a universal testing machine. The results showed that there was
significant differences observed between group 1 and group 2 and group 4. The shear bond
strength of brackets contaminated before priming showed significant difference than the
control group.
Neslihan Eminkahyagil, et al42
(2005) did an invitro study comparing the shear bond
strength of a self etch primer adhesive and an antibacterial self etch primer adhesive for
orthodontic metal brackets. They assigned twenty four premolars into two equal groups. In
group 1- Transbond plus self etching primer was used and in group 2- antibacterial dentin
bonding system was used. The results showed that the difference between the groups was not
statistically significant. ARI score showed that the predominant mode of bracket failure for
both groups was the bracket adhesive interface leaving less than 25% of the adhesive on the
bracket base.
Raed Ajlouni, et al 48
(2005) compared the use of new self etching primer/adhesive effects on
shear bond strength of orthodontic metal brackets bonded to surface. Forty five maxillary
central incisor teeth were divided in to 3 group - group 1(control), here porcelain teeth were
bonded using 37% phosphoric acid, a sealant and composite adhesive. In group 2,
Review of literature
Page 13
microleaching of porcelain teeth, use of hydrofluoric acid and silane coupling agent and
composite agent and composite adhesive was used. In group III , the porcelain teeth were
etched using phosphoric acid and a new self etching primer / adhesive was applied before
bonding. The results showed low shear bond strength in group I and II, group III showed no
significant difference in shear bond strength. SEM study showed micro etching , use of
hydrofluoric acid produced greatest damage to porcelain surface when compared with the
new self etch / silane /adhesive combination.
Samir E.Bishara, et al 54
(2005) studied the effects of changing the cross head speed of the
testing machine on the shear bond strength of orthodontic metal brackets to enamel. They
standardized all the other variables. In this study 40 extracted human molars were bonded
using Transbond XT adhesive system and then divided into 2 groups. The test parameter such
as the cross head speed is 5mm/minute for the group 1 and 0.5mm/minute for group II. The
results showed significant difference in shear bond strength between two groups. The group
II showed higher shear bond strength (Mean = 12.2±4Mpa) higher compared to group I with
mean = 7.0±4.6Mpa respectively.
Y.Teresa Silta, et al72
(2005) did an invitro study to evaluate the effect of shorter
polymerization times when using the latest generation of light emitting diodes. Here two LED
light curing units (Ortholux LED ,Ultralume LED 5) and a quartz tungsten halogen light cure
unit (optilux) were used to bond orthodontic brackets for curing time of 20 seconds,10
seconds or 6 seconds .The results of the study showed significant differences in bond strength
when compared to different light types and curing time. The 6 seconds cured brackets
showed lower bond strength than the 20 second cured brackets and bond strength of brackets
cured for 20 seconds with optilux 501 QTH LCU and the ultralume LED 5 LCU were
significiantly high compared to 6 seconds cured brackets. Thus they recommend (at least ) 20
seconds of curing time with QTH or LED cutting lights.
Review of literature
Page 14
Zafer C. Cehreli, et al73
(2005 ) did an invitro study to compare the shear bond strength of 4
self etching primer and adhesive formulations. The self etching products tested were
PromptL-Pop, Clearfil SE Bond ,FL bond and one-up bond F. The conventional acid etch and
bond system was Transbond XT and also they used the non-rinse conditioner and acetone
based adhesive system(NRC and Prime and Bond NT). The brackets were bonded to 42
bovine mandibular incisors with 7 teeth each for 6 groups. The results of shear bond test after
testing in an universal testing machine showed significantly lower value than the control
group so they concluded that these products might not be suitable for orthodontic bracket
bonding in terms of shear bond strength.
Ascension Vicente, et al5(2006) in an invitro study evaluated the effects of three adhesion
promoters on the shear bond strength of orthodontic brackets. The promoters used in this
study were Ortho sol, All bond-2, Enhance LC and two adhesives were used-Transbond XT
and light bond. A total of 150 premolars were divided into 25 each of 6 groups. (1)Transbond
XT, (2)Transbond XT Plus All bond 2, (3) Transbond XT plus Ortho solo, (4)Transbond XT
Plus Enhance LC, (5)Light bond, (6)Light bond plus Enhance LC. The test was done in an
universal testing machine and the results showed highest bond strength for light bond plus
Enhance LC and none of the adhesion promoters significantly increased the bond strength.
Juliana Godoy-Bezerra, et al25
(2006 ) did an invitro study to evaluate the three different
enamel pretreatment on shear bond strength of resin modified glass ionomer cement after
different enamel pretreatments in saliva contaminated environment. 125 bovine incisors were
divided into three groups. Group I – received 10% polyacrylic acid moistened with saliva /
Fuji Ortho LC (FOLC), Group II - received 37% phosphoric acid, moistened with saliva /
FOLC, Group III was moistened with saliva / FOLC without acid etching, Group IV -10%
Review of literature
Page 15
polyacrylic acid, not moistened with saliva FOLC and Group V was used as control with
37%phosphoric acid / dry / TransbondXT. The results showed highest bond strength for
group V and similar bond strength noted for group II. There were no statistically significant
difference between groups I,III,IV. They concluded that the saliva moistened FOLC GIC
showed no statistically significant difference from Transbond XT group.
Julio Pedra e Cal - Neto, et al 26
(2006) evaluated the influence of a new self etching primer
on bracket shear bond strength . Forty extracted human premolar were divided into two
groups of 20 each . Group 1 ( control ), Phosphoric acid + Transbond XT primer and
adhesive ( 3MUnitek) and group 2, Adper Prompt L Pop - self etching primer, Transbond XT
adhesive paste was used and cured with Ortholux XT( 3M Unitek) visible light curing unit
.Instron universal testing machine was used to calculate the shear bond test.The results
showed no significant difference in the bond strengths of two groups evaluated . The ARI
was less for the new self etching primer as the amount of adhesive on the enamel after
debonding was significantly less than when using the phosphoric acid.
Maria Francesca Sfondrini, et al36(2006) did a study to assess the effect of light tip
distance on the shear bond strength of resin modified glass ionomer cured with three curing
units (high intensity halogen, LED and plasma arc). The shear bond strength test was done in
an universal testing machine and the results of the study showed that when the light tip
distance is 0 mm, there is no significant difference among three groups. At a light tip distance
of 3mm, the bond strength of halogen and plasma arc curing is similar and it is higher than
the LED curing light and at a light tip distance of 6mm, the bond strength of LED and
halogen is similar but lesser than the plasma arc curing light. Thus the plasma arc curing light
produced higher bond strength than other two light curing system. The ARI score is similar
for all groups except with the LED light at a distance of 3mm.
Review of literature
Page 16
Michael D.Signorelli, et al 39
(2006) did an invitro shear bond strength test and also an invivo
survival rate of orthodontic brackets bonded with either a halogen or a plasma arc light . 90
stainless steal brackets were bonded to the premolar teeth using a halogen light with 20
second curing time or a plasma arc light with 2,6 or 10 second curing time. Brackets were
tested within 30 minutes or after thermocycling for 24 hours. For invitro study ,they did a
spilt arch design to determine the brackets failure rate in 25 palients for a period of 1.1 years
(386 days). The results of the study showed no statistically significant differences in bond
strength and also the invivo study also showed no significant difference in bracket failure
Ascension Vincente, Luis Alberto Bravo6(2007) did a study to compare the shear bond
strength or the adhesive remaining on the tooth after debonding between APC plus precoated
and uncoated brackets using a self-etching primer. Forty premolars were divided into twenty
five for uncoated brackets and fifteen for precoated (APC Plus) brackets. The brackets are
bonded using TPSEP(self etching primer)/Transbond XT adhesive resin and light cured. The
results of the study showed that there is no significant difference in the shear bond strength
and also in the percentage of area of adhesive remaining on the tooth between two bracket
groups.
Hakan Bulut, et al19
(2007) in an invitro study investigated the shear/peel bond strength of
metal brackets bonded with three curing systems; No mix bonding adhesive(Unitek,3M
Unitek), 2-paste chemically cured bonding resin(Concise,3M Unitek), light cured adhesive
(Transbond XT). Each bonding group was separated into experimental (n=20) and control
groups (n=20). The control group was bonded only with their relevant bonding system where
as in the experimental group, an anti bacterial self etch adhesive was applied to the enamel.
The results of this study after testing in an universal testing machine showed groups 1 and 2
showed significant difference in bond strength than their control group where as group 3 did
not differ from the control group and all the results showed clinically significant bond
Review of literature
Page 17
strength so they concluded that the newly developed antibacterial self etch adhesives can be
combined with various bonding systems.
Kayo Saito, et al27
(2007) did an invitro study to assess the antibacterial efficacy of 4-
methacryloxyethyl Trimellitateanhydride /Methyl methacrylate –tri-n-butyl borane resin
containing benzalkonium chloride and the shear bond strength of orthodontic brackets
bonded using this material. The antibacterial activity of the BAC composite was measured by
the disk diffusion method using streptococcus mutans and streptococcus sobrinus agar plates.
The shear bond test was done using anuniversal testing machine and the results showed that
the bond strength declined with increase in BAC concentration and BAC composites showed
significant antibacterial activity and the bond strength of BAC composite groups also had
clinically significant bond strengths so they can be used as an orthodontic bonding adhesives.
Nikolaos Pandis, Sophia Strigou, Theodore Eliades43
( 2007) made a clinical assessment
with split mouth study to assess the long term failure rate of brackets bonded with a plasma
curing light or a high intensity (LED) curing light. Twenty five patients were bonded with
brackets according to a split mouth design with the 3M ortholite plasma or the high power
satelec mini LED curing light. Bracket failures were recorded and the results were analysed
with variables as light source (plasma or LED), arch(maxillary or mandibular), side(left or
right), and region(anterior or posterior) separately or simultaneously. The results showed that
the failure rates for plasma is less compared to the LED light source. The failure were found
more for the mandibular arch(150% higher incidence) than maxillary arch. The arch side
(right vs left) and location (anterior vs posterior) had no effect.
Review of literature
Page 18
Nirshpack, et al44
(2007) did a study to examine the ultimate accuracy of bracket placement
in labial Vs lingual systems and also in direct Vs indirect bonding techniques. 40 casts of 20
orthodontic subjects were selected and the subject were divided into four groups according to
the appliance bonding(labial / lingual) and technique of bonding (direct/indirect). For labial
system-Orthos brackets(Orcmo)were placed and (0.022x0.028 inch slot ) for lingual system
(lingual generation 7 brackets (Orcmo)(0.018x0.025 inch anteriors) and 0.022x0028 inch slot
premolars were placed.Tranbond XT was used for both direct and indirect bonding. labial
brackets were oriented with a Boone gauge and the lingual brackets were oriented with the
lingual-bracket jig system.Torque error (TqE) and rotation deviation were measured with a
torque geometric triangle and a toolmaker’s microscope.The results of the study showed that
the absolute TqE and Rot D values were significantly higher in direct that in indirect bonding
technique. No statistically significant differences were found between labial and lingual
system for the same bonding technniques.
Nuray Attar, et al45
(2007) did a study to assess and compare the effects of one and step self
etching primer and adhesive with conventional adhesive system(such as use of an enamel
conditioner, a primer and an adhesive resin to bond brackets) on the shear bond strength
brackets of orthodontic brackets.Forty two human premolars were randomly divided into
three groups including seven maxillary and seven mandibular premolars in each group.For
group 1(control group) - 40% phosphoric acid (k-etch) used as etchant and Kurasper F bond
was applied and light cured for 10 seconds .For group 2: clearfil protect bond ,a two step self
etchintg primer and adhesive was used and light cured.For group 3,clearfil tri- S bond ; a one
step self – etching primer and adhesive system was applied on the enamel for 20 seconds and
light cured for 10 seconds. Stainless Steel premolar brackets were used in all the groups and
light curing was performed with LED LCU (Elipar free light ,3MESPE,St Paul
,MN,USA).The results of the study after testing in an universal testing machine showed no
Review of literature
Page 19
statistically significant differences among three groups.TheARI scores showed that failure
was at the bracket adhesive interface with score of 1.
Rodney G.Northrup, et al51
(2007) compared the shear bond strength of two adhesives
(TransbondXT, Blugloo) and self-ligating and conventional brackets. Sixty extracted
premolars were divided into three groups of 20 teeth. In group 1 light cure conventional
bonding with Transbond XT primer & adhesive with conventional SS brackets were done, In
group 2 bonding with light cure self ligating brackets with Transbond XT primer & adhesives
were done, In group 3 they used light cured adhesive (Blugloo) and light cured primer
(orthosolo) to bond self ligating brackets. Results of shear bond test in an universal testing
machine showed lower shear bond strength for conventional brackets compared to the self
ligating brackets and ARI score for all groups were not stastistically different.
Samir E.Bishara, et al55
(2007) did a study to compare the shear bond strength of brackets
when self etching primer A, different brands and the brackets adhesive are light cured either
separately or simultaneously. Seventy five human molars are divided into five groups. The
five protocols were: group 1(control), the SEP Transbond plus was applied and light cured;
group 2, SEP Adper prompt L-pop was applied, light cured, brackets placed and light cured.
In group 3, SEP Adper prompt L-pop was applied, after placing the bracket with adhesive it
was light cured simultaneously. In group 4, SEP Clearfil S3 bond was applied and after
placing the bracket with adhesive it was light cured simultaneously. The results showed when
compared to control(group 1), the bond strength were higher for S3 bond(2 light exposure)
and S3 bond(1 light exposure), where as the Adper Prompt L-pop group(1 light exposure)
does not differ significantly than other two groups.
Review of literature
Page 20
Toshiya Endo, et al63
(2007) evaluated the bond strength of identical orthodontic brackets
bonded to maxillary deciduous and permanent teeth and also their modes of brackets
/adhesive failure. Metal premolar brackets were bonded to teeth in each group by acid etch
adhesive system and the shear bond strength test was performed using an universal testing
machine and the results showed low bond strength for deciduous teeth compared to the
permanent teeth but the bond strength of all 4 groups were higher than the clinically
significant range of 6 to 8 Mpa . ARI scores showed that bond failure at enamel –adhesive
interface occurred more frequently in the deciduous second molars compared to the
permanent 1st premolars and they concluded that the deciduous teeth could also be used as
anchor teeth in sectional mechanics.
Virna Cavalcante Patusco, et al67
(2007) tested the bond strength of metallic brackets after
at-home and in-office vital bleaching. Forty five human premolars were divided into three
groups of 15 each. First group served as control , second group is bleached with
10%carbamide peroxide, third group is bleached with 35% hydrogen peroxide. The results
of shear bond strength showed no satisfactory difference between group 1&2 where as group
3 had lower mean shear bond strength than group 1 &group2. This shows that in-office
bleaching significantly reduces bond strength and also the amount of resin remnant on the
tooth surface after the debonding procedure. rates between the two light sources.
Y.Sinasi Sarac, et al71
(2007) investigated an invitro study to evaluate the effects of three
surface conditioning methods on shear bond strength(SBS) of a feldspathic ceramic and also
investigated its surface roughness and compared the efficiency of three polishing techniques.
Three specimens were divided into three groups as air particle abrasion(APA) with 25-µm
aluminium trioxide(AL2O3)(Group A); hydrofluoric acid(HFA)(Group H); APA and
HFA(Group AH) .The surface conditioning methods employed are adjustments kit, diamond
polishing paste, adjustment kit +diamond polishing paste and 63 specimens were divided into
Review of literature
Page 21
three groups. The results of this study showed that lowest shear bond strength for group
H(Hydrofluoric acid group) compared to group A and AH and also the Ra value was lowest
for group H .The surface conditioning methods are equally effective to smooth the porcelain.
Asli Baysal, Tancan Uysal, Mustafa Ulker, Serdar Usumez 8
(2008) did a study to evaluate
the effects of high intensity light curing units (LED) and plasma arc curing on the
microleakage of flexible spiral wire retainers at the composite / enamel and composite / wire
interfaces. Three groups of 15 human mandibular incisors were bonded with multistranded
PentaOne wire of 0.0215 inch diameter and cured with three different light source. Group
1(Control ) – QTH for 10 seconds and group 2 : LED for 5 seconds and group 3 : PAC for 3
seconds were used .The samples were sealed with nail varnish, stained with 0.5 % basic
fuschine and sectioned. Under a stereomicroscope the transverse sections were evaluated and
scored for microleakage for the composite / enamel and composite / wire interfaces. The
results of the study showed at composite /enamel interface there were little or no
microleakage where as at composite /wire interface the microleacage was less in QTH group
than other two with statistically significant difference and there was no significant difference
between LED and PAC groups.
Jeff A. Foster, David W.Berzins, Thomas G.Bradley 23
(2008) did a study to evaluate
whether an amorphous calcium phosphate (ACP)-containing adhesive has an acceptablelevel
of shear bond strength when used as an orthodontic adhesive. In this study 60 brackets were
bonded to premolars which where randomly divided into three groups; Group 1: Transbond
XT-composite resin adhesive; Group 2: Aegisortho-ACP containing adhesive;Group 3: Fuji
ortho LC- Resin modified glass ionomer. After etching with 35%phosphoric acid for 15
seconds, Transbond XT light cured primer was applied to the teeth and then followed by
corresponding adhesive application in each group. An instron testing machine was used to
debond the brackets and the results of the study showed that the mean shear bond strength is
Review of literature
Page 22
greater for group 1(15.2±3.6 Mpa) than group 2(6.6±1.5 Mpa) and group 3(8.3±2.8 Mpa).
Group 1&3 exhibited lower ARI score than group 2 and they concluded that the ACP-
containing adhesive demonstrated a low but satisfactory bond strength needed to function as
an orthodontic adhesive.
Phillip D. Lowder, Tim Foley and David W.Banting46
(2008 ) did a study to investigate the
shear / peel bond strength (SPBS) of orthodontic brackets bonded with 1 of 4 orthodontic
adhesives (TransbondXT ,Blugloo,Light bond and APC plus applied over a filled resin
sealant(Proseal). 240 extracted premolars were collected and the teeth were randomly
assigned to 1 of 6 groups (40 teeth per group). There were 4 adhesive - sealant groups and 2
groups with adhesive (TransbondXT,Blugloo)only. The adhesive sealant groups were
Transbond XT/Proseal ,Light bond/Proseal, APC plus/Proseal, and Blugloo/Proseal. After the
brackets were cured, the shear bond test was done using a calibrated universal testing
machine (model 3345-Instron) and the results showed that three adhesive sealant
combination groups had lower shear bond strength than the 2 reference groups but the
lightbond/Proseal group had a higher mean SPBS compared with 2 reference groups.
Samir E.Bishara, et al56
(2008) did an invitro study to test the difference in brackets failure
characterstics when using a new ceramic debonding instrument when compared with the use
of conventional pliers.Ceramic maxillary premolar brackets (APC plus,clarityseries : 3M
Unitek) were used .The enamel surface was studied under transillumination with a fiber optic
light head and evaluatedfor enamel cracks.Teeth were bonded with Transbond SEP and
precoated brackets was placed and light cured with use of a halogen light.Teeth were divided
into two groups of 15 teeth each and in group 1 - utility pliers (3M Unitek) were used and in
group 2- new debonding instrument (3M unitek) were used. Once the brackets were
debonded the enamel surface of each tooth wasexamined under 10X magnification in an
stereomicroscope and the modified ARI score was used to evaluate the adhesive remained on
Review of literature
Page 23
the tooth. Results of the study showed statistically significant difference in bond failure
patterns between two groups and the brackets debonded with a new instrument showed more
adhesive to be removed from the tooth during debonding.
Selma Elekdag-Turk et al58
(2008) did a study to evaluate the effects of thermocycling on
the shear bond strength values of an self etching primer after 0,2000 and 5000 thermal cycles.
The results of the study showed that in the control group the shear bond strength does not
vary with thermocycling, whereas in the thermocycling group SBS decreased with 2000 and
5000 cycles. The ARI scores also varied when compared to control group with 5000 cycles
and SEP group with no thermocycling and with 5000 thermal cycles. Within the SEP group
also ARI scores varied with nothermocycling and with 5000 thermal cycles group. With this
results of the study they concluded that the bond strength values of SEP group is less than the
control but SEP provides clinically acceptable bond strength.
Matheus Melo Pithon,et al37
(2009) did a study to evaluate the effect of increasing storage
time after activation on the influence of shear bond strength of brackets bonded to enamel
with a self etching primer.210 brackets were divided into seven groups of 30 each. The self
etching primer were mixed, activated and stored inside a refrigerator at 8 degree celcius.
TPSEPs were kept activated for 30(group 30),21(group 21),15(group 15),7(group 7),3(group
3)or 1(group 1)days before bonding and in one group(group 0) was used immediately after
mixing, activated TPSEP was applied and brackets were bonded with Transbond XT and
light cured. The result of the study showed no significant difference in bond strength +ARI
score among 0 to 15 and among groups 21 to 30.They concluded that storing activated
TPSEP upto 15 days did not produce significant change on the shear bond strength.
Virna Cavalcante Patusco et al67
(2009) tested the bond strength of metallic brackets after
at-home and in-office vital bleaching. Forty five human premolars were divided into three
Review of literature
Page 24
groups of 15 each. First group served as control, second group is bleached with
10%carbamide peroxide, third group is bleached with 35% hydrogen peroxide. The results of
shear bond strength showed no satisfactory difference between group 1&2 where as group 3
had lower mean shear bond strength than group 1 & group 2. This shows that in-office
bleaching significantly reduces bond strength and also the amount of resin remnant on the
tooth surface after the debonding procedure.
Theorde Eliades61
(2010) reviewed the fundamentals of photocuring with various type of
lamps in orthodontics. The key properties such as polymerization efficiency(degree of cure),
mechanical properties(bond strength), clinical performance(failure rate) and biological
properties of blue light are reviewed to know their clinical usefulness in application to
orthodontic bonding. The light intensity , their penetration into the adhesive,(the composition
of the adhesives , their resin, fillers, initiators, inhibitors)are factors that can vary the
polymerization efficiency. For any light cure lamp its light intensity, wavelength and the
curing time are the important factors to be considered before its selection for the orthodontic
purpose. For evaluating the bond strength factors such as the bracket design, variation in load
application, loading rate, teeth storage and preparation, testing conditions can significantly
alter the results in addition to type of curing system used.
Adrian.C.Shortall, Will M Palin , Bruno Jacquot and Bruno Pelissier2(2012) described
the history of light curing in dentistry and about the four generations of LED and about
selection criteria for the clinician considering purchasing a new LED. The features of third
generation LED such as reduced power consumption , their ergonomic design features , either
battery powered or corded and broad spectral output with universal curing of photo activated
dental resins irrespective of initiator formulation shorter irradiance time made them popular
than the second generation blue LED. Now the LED is towards its fourth generation
Review of literature
Page 25
incorporating the features of third generation and also it has features of four different diode
wavelength selection for curing adhesives with minimized over heating issues and the
polymerization stresses are reduced due to its soft scan options.
Adrian.C.Shortall, R.B.Price, L.Mackenzie, F.J.T.Burke1(2016) discussed the
development of LCUs in dentistry and also about the selection, use and maintanence of LED
light-curing units. Early LED required longer exposure time because of their low energy
output. In order to increase their output they started fitting multiple LED emitters in gun style
or pen style models. The second generation LED units were smaller as they had powerful
blue LED chips. The newly introduced third generation polywave LED simulated the
broader emission spectrum of QTH and PAC units for activating materials containing
alternative photoinitiators which had 4 LED emitters each producing different wavelengths of
light. Manufacturers of polywave LED curing light are Ivoclar Vivadent, GC, Heraeus
Kalzer, Ultradent and their resins are benefited from polywave LED curing light as these
composite manufacturers market materials that use alternative photoinitiator other than
camphoroquinone.
Materials and Methods
Page 26
MATERIALS AND METHODS
MATERIALS
BRACKETS : [ Figure 1 ]
Metal brackets : Unitek Gemini metal brackets Forty stainless steel brackets [First and
second maxillary premolars of both sides] - 0.022 x 0.028 inch slots with MBT
prescription, with -7 degree torque and 0 degree angulation - REF 119 -142 ( 3M Unitek
Corp )
Ceramic Brackets : Unitek Gemini clear ceramic brackets. Forty polycrystalline ceramic
brackets [First and second maxillary premolars of both sides] - 0.022 x 0.028 inch slots
with MBT prescription with -7 degree torque and 0 degree angulation - REF 117 -100
(3M Unitek Corp )
The average bracket base area was 9.806 mm2 for metal brackets and 11.74 mm
2 for
ceramic brackets as given by the the manufacturer and it is also verified by an image
analysis software (CMEIAS Ver .1.28 operating in UTHSCSA image tool Ver.1.28).
LIGHT EMITTING DIODE CURING LIGHTS : LED – LCUs [ Figure 2 ]
Monowave LED curing light - Bluephase C5 ( Ivoclar Vivadent ) with light intensity of
500 mW/ cm2
and wavelength of 430-490 nm , corded operation , 10 mm black light probe.
Curing time recommended by the manufacturers is 20 seconds.
Poly wave LED curing light - Bluephase Style ( Ivoclar Vivadent ) with light intensity of
1,100 mW / cm2
and wavelength of 385 -515 nm, lithium - polymer battery , 10 mm black
light probe. Curing time recommended by the manufacturers is 10 seconds even for 4mm
bulk fill.
Materials and Methods
Page 27
Bonding Materials used [Figure 2 ]
Etchant - 34 % Phosphoric acid solution( Scotchbond – 3M ESPE )
Primer -Transbond XT –3 M Unitek
Composite Adhesive - Transbond XT – 3 M Unitek
TEETH SAMPLES
80 extracted human maxillary and mandibular premolars extracted for therapeutic purpose
as a part of fixed orthodontic treatment in the department of oral and maxillofacial surgery ,
KSR Institute of Dental Science and Research, Thiruchengode were used as the test samples.
Criteria for tooth selection :
1)Intact enamel with no developmental defects.
2)No pretreatment use of chemical agents.
3)No caries with normal tooth morphology.
4)No cracks due to the pressure of the extraction forceps.
Storage:
The samples were stored in distilled water at room temperature in an airtight humid
environment to prevent dehydration and it is periodically changed until their use.
Mounting: [ Figure 3 ]
Teeth were cleansed of soft tissue and embedded in cold curing acrylic ( DPI )
Materials and Methods
Page 28
Pink Acrylic group – Poly Wave
Clear Acrylic group - Monowave
Each tooth was oriented such that its labial surface would be parallel to the force during the
shear bond test.
Sample grouping
80 samples were divided into 4 groups such that there are twenty samples in each group.
The samples were grouped based on the type of bracket material ( metal brackets / ceramic
brackets) and their LED curing light ( monowave LED / polywave LED ).
Table 1 – Classification of samples into four groups
Bracket
material
Curing light Total number
of
samples/group
Curing
time / bracket
Group I
(Metal Monowave)
Metal MonoWave
LED
20 20 seconds
Group II
(Metal Polywave)
Metal Polywave LED 20 10 seconds
Group III
(CeramicMonowave)
Ceramic MonoWave
LED
20 20 seconds
Group IV
(Ceramic Polywave)
Ceramic Polywave LED 20 10 seconds
Materials and Methods
Page 29
METHODS
Method of bracket bonding for both metal and ceramic brackets for all 4 groups are as
follows
Cleaning - Before the bonding , the facial surface of each premolar was cleansed with a
mixture of water and fluoride free pumice with a rubber polishing cup for 10 seconds.
The enamel surface was thoroughly rinsed with water to remove any pumice or debris and
dried with an oil free air stream .
Etching -The buccal enamel surfaces were etched with 34 % phosphoric acid solution (
Scotchbond – 3M ESPE ) for 30 seconds followed by thorough washing and drying.
Priming- A thin , uniform film of the primer ( Transbond XT – 3M unitek ) were applied to
the etched surface of the tooth.
Light cure adhesive placement and bonding
The brackets with the adhesive were placed on the tooth near the center of the facial surface
with sufficient pressure to express excess adhesive which was removed from the margins of
the bracket base with a sickle scaler before polymerization.
Materials and Methods
Page 30
Curing Method (Figure 4)
Group I and III( Monowave LED ) : light – curing for 20 seconds / bracket, 10 seconds for
the mesial side and 10 seconds for the distal side at a distance of 1mm away from the
bracket.
Group II and IV(Polywave LED ) : light – curing for 10 seconds /bracket, 5 seconds for the
mesial side and 5 seconds for the distal side at a distance of 1mm away from the bracket.
The intensity check was done with an intensity meter to confirm whether proper light
intensity of light is emitted from the light source.
Immediately after bonding the samples were stored in distilled water at room temperature for
24 hours after which the testing was performed.
Shear bond testing procedure (Figure 5 )
The KALPAK universal testing machine- 121101( Kalpak Instruments and Controls , Pune
India) was used to test the shear bond strength of each tooth. The acrylic block is mounted
on a universal joint to ensure that the applied force was parallel to the tooth surface.The force
was applied with a beveled flattend steel rod at the bracket-tooth interface at a crosshead
speed of 0.5 mm per minute in a occlusogingival direction. The force values ( in Newton)
recorded at the point of failure were converted to shear stress by dividing by the bracket
surface area (mm2
) and were reported in megapascals ( N/ mm2) for all 80 samples by the
UTM software in computer connected to the testing machine.
Materials and Methods
Page 31
ARI scoring for all groups ( Figure 6)
After bracket failure , the enamel surface was examined under an optical stereomicroscope
magnification x10) and the amount of adhesive remaining on the tooth was imaged.
Analysis of residual adhesive on the tooth surface was done according to Artun and Bergland
– ARI score by visualizing in the microscope and the scores were made.
The criteria for scoring were as follows : 0 = No adhesive on the tooth
1= Less than half of the adhesive on the tooth
2= More than half of the adhesive on the tooth
3= All the adhesive on the tooth , with a distinct
impression of the bracket mesh.
Materials and Methods
Page 32
FIGURE 2 - METAL AND CERAMIC BRACKETS USED IN THE STUDY
FIGURE 1 – METAL AND CERAMIC BRACKETS USED IN THE STUDY
Metal Brackets
Ceramic Brackets
Materials and Methods
Page 33
FIGURE 2 – CURING LIGHT AND THE LIGHT CURE BONDING MATERIALS
FIGURE 3 - CURING LIGHT AND THE LIGHT CURE BONDING MATERIALS
Monowave LEDBluephase C5
( Ivoclar Vivadent )
Polywave LEDBluephase Style
( Ivoclar Vivadent ) Bonding materials
Monowave LED
Bluephase C5
(Ivoclar Vivadent)
Polywave LED
Bluephase style
(Ivoclar Vivadent)
Bonding Materials Bonding Materials Bonding Materials
FIGURE 3 - CURING LIGHT AND THE LIGHT CURE BONDING MATERIALS
Monowave LEDBluephase C5
( Ivoclar Vivadent )
Polywave LEDBluephase Style
( Ivoclar Vivadent ) Bonding materials
Bonding Materials
Bonding Materials
Materials and Methods
Page 34
FIGURE 3 – TEETH SAMPLES MOUNTED IN ACRYLIC BLOCKS
Total of 80 samples
4 groups of 20 samples Acrylic used for the blocks
Materials and Methods
Page 35
FIGURE: 4 - LIGHT CURING METHOD
FIGURE 4 - LIGHT CURING METHOD
Materials and Methods
Page 36
FIGURE 5 – UNIVERSAL TESTING MACHINE AND THE SHEAR TEST
FIGURE 5 - UNIVERSAL TESTING MACHINE AND THE SHEAR TEST
Materials and Methods
Page 37
FIGURE 6 – OPTICAL STEREOMICROSCOPE
FIGURE 7- STEREOMICROSCOPIC PICTURE OF TOOTH SURFACE TO
DETERMINE ARI
Statistical analysis
Page 38
STATISTICAL ANALYSIS
The mean and standard deviation were estimated for the four groups of samples.
To find out the significant difference between the groups and the Student’s t-test
were used.
The formula used to assess the student t-test was
t = d / SE (d)
Where
SE (d) = Standard error of d
S / √n ∑n
S = i=1 (di-d)2
n - 1
∑n di
d = i = 1
n
Where di is the difference of the observation at two time points
The frequency of distribution of the ARI scores obtained for all four groups were determined
using a Chi - square analysis and P value of less than 0.055 was considered to be statistically
significant.
Results
Page 39
Table 2 showing the values of shear force and the shear bond strength of all four
groups
Sample
No
Metal
bracket
base
surface
area
(mm 2)
Group I Group II Ceramic
bracket
base
surface
area
(mm2)
Group III Group IV
Peak
load
( N )
Shear
bond
strength
N/mm 2
Peak
load
( N )
Shear
bond
strength
N/mm 2
Peak
load
( N )
Shear
bond
strength
N/mm2
Peak
load
( N )
Shear
bond
strength
N/mm 2
1 9.806 113.031 11.52 87.760 8.94 11.74 96.560 8.22 434.711 37.02
2 9.806 80.658 8.22 168.055 17.13 11.74 320.561 27.30 144.845 12.33
3 9.806 107.979 11.01 274.719 28.01 11.74 287.060 24.45 185.075 15.76
4 9.806 101.053 10.30 86.083 8.77 11.74 188.264 16.03 443.510 37.77
5 9.806 30.127 3.07 46.411 4.73 11.74 476.638 40.59 389.987 33.21
6 9.806 171.047 17.44 65.874 6.71 11.74 310.084 26.41 129.315 11.01
7 9.806 51.463 5.24 142.785 14.56 11.74 344.331 29.32 463.168 39.45
8 9.806 46.970 4.78 73.359 7.48 11.74 299.980 25.55 207.531 17.67
9 9.806 55.387 5.65 72.604 7.40 11.74 302.226 25.74 261.996 22.31
10 9.806 100.307 10.22 94.873 9.67 11.74 387.564 33.01 295.301 25.15
11 9.806 195.003 19.88 100.121 10.21 11.74 145.973 12.43 245.338 20.29
12 9.806 88.516 9.02. 91.321 9.31 11.74 83.277 7.09 139.606 11.89
13 9.806 63.814 6.50 53.327 5.43 11.74 276.024 23.51 280.517 23.29
14 9.806 102.554 10.45 35.924 3.66 11.74 154.939 13.19 209.963 17.88
15 9.806 95.255 9.71 122.017 12.44 11.74 189.941 16.17 252.254 21.48
16 9.806 91.880 9.36 112.648 11.48 11.74 406.831 34.65 372.221 31.70
17 9.806 189.880 19.36 88.329 9.0 11.74 538.755 45.89 224.933 19.15
18 9.806 81.031 8.26 133.239 13.58 11.74 162.993 13.88 416.748 35.49
19 9.806 90.203 9.19 149.701 15.26 11.74 352.944 30.06 325.251 27.70
20 9.806 106.664 10.87 99.552 10.15 11.74 117.897 12.00 318.756 27.06
Results
Page 40
Table 3 showing mean and SD of shear bond strength values in mega Pascal’s ( MPa)
for all groups
Group N Bond strength (MPa)
Mean
SD
Curing
time /
bracket
I-Metal
Monowave
20 10.00 4.48 10
seconds
II- Metal
Polywave
20 10.69 5.39 10
seconds
III-Ceramic
Monowave
20 23.27 23.27 10
seconds
IV- Ceramic
Polywave
20 24.44 24.44 10
seconds
Bar chart 1 showing the mean shear bond strength values in mega Pascal’s ( MPa) for
all groups
0
5
10
15
20
25
30
Group I Group II Group III Group IV
Results
Page 41
Table 4: Comparison of shear bond strength of metal brackets cured with monowave
LED and polywave LED
Group N Mean SD t value p value
I 20 10.00 4.48 - 4.43 0.66
II 20 10.69 5.39
Inference : Table 4 depicts no statistically significant differences in the shear bond strength
of metal brackets cured with monowave LED and polywave LED
Table 5: Comparison of shear bond strength of ceramic brackets cured with monowave
LED and polywave LED
Group N Mean SD t value p value
III 20 23.27 10.72 - .3.73 0.71
IV 20 24.44 8.98
Inference : Table 5 depicts no statistically significant differences in the shear bond strength
of ceramic brackets cured with monowave LED and polywave LED
Table 6: Comparison of shear bond strength of metal and ceramic bracket cured with
monowave LED
Group N Mean SD t value p value
I 20 10.00 4.48 -5.12 < 0.001
III 20 23.27 10.72
Inference : Table 6 shows mean and standard deviation of shear bond strength of metal and
ceramic bracket cured with monowave LED. The shear bond strength of ceramic brackets is
higher than the metal brackets.
Table 7: Comparison of shear bond strength of metal and ceramic bracket cured with
polywave LED
Group N Mean SD t value p value
II 20 10.69 5.39 - 5.87 < 0.001
IV 20 24.44 8.98
Inference: Table 7 shows mean and standard deviation of shear bond strength of metal and
ceramic bracket cured with polywave LED. The shear bond strength of ceramic brackets is
higher than the metal brackets.
Results
Page 42
Table 8: Comparison of shear bond strength of metal and ceramic brackets
Group N Mean SD t value p value
Metal 40 10.35 4.91 -7.81 <0.001
Ceramic 40 23.86 9.78
Inference :Table 8 shows mean and standard deviation of shear bond strength of metal and
ceramic bracket. The shear bond strength of ceramic brackets is higher than the metal
brackets.
Table 9: Frequency distribution of the Adhesive Remnant Index ( ARI ) and enamel
fracture of the 4 groups evaluated
Group
ARI scores
0 1 2
3
Total Number
of samples
I 3 10 1 6 20
II 6 12 1 1 20
III 5 11 2 1 19 ( 1 enamel
fracture )
IV 10 8 1 0 19 ( 1 enamel
fracture )
Score 0 – no adhesive on the tooth
Score 1 – less than half of the adhesive on the tooth
Score 2 – more than half of the adhesive on the tooth
Score 3 – all adhesive on the tooth indicating distinct impression of the bracket mesh
Chi square value : 16.64 P Value = 0.055
As per the statistical result - the ARI showed broadly a similar pattern between these 4
groups and the chi-square analysis revealed no statistically significant difference between
them.
Results
Page 43
Bar chart 2 showing the frequency distribution of the adhesive remnant index of the 4
groups evaluated
0
2
4
6
8
10
12
14
Group I Group II Group III Group IV
score O
score 1
score 2
score 3
Discussion
Page 44
Every orthodontist and orthodontic patient prefer best treatment in shorter duration of time
but orthodontic treatment time can be greatly influenced by the frequency of debonding
occurring during treatment that can lead to lack of progress in the treatment and in some
cases even relapse. Therefore bond strength between the bracket and enamel has become an
important issue in research.
Many studies have shown that factors such as tooth conditioning5,21,45,53,73
, design of the
brackets base, type of adhesive system18,19,42,51
and the mode of cure3,10,20,32,59,60,64
can
influence the bond strength. The most important of these factors is whether the adhesive
composite has reached a level of polymerization that will adequately retain the bracket to the
tooth when orthodontic forces are applied.
As new curing systems to enhance bonding are constantly being introduced on the
market at a very rapid pace, the orthodontic practitioners should be aware of various types of
light sources, their lamp properties, performance, polymerization efficiency and their
application to orthodontic bonding.
The literature contains abundance of studies testing the different light cure units currently
available such as quartz tungsten halogen lamps, argon lasers, xenon plasma arc lights, light
emitting diode curing lights comparing their advantages and disadvantages.
First light cure unit had the ultraviolet light which had the disadvantage that one minute was
required per millimeter thickness of curing. Because of the safety concerns and long time use
of UV light, visible light curing was then introduced around 1980. The visible light activated
resin systems use a diketone absorber to create free radicals that initiate the polymerization
process. Most dental photo initiator systems use camphoroquinone as the diketone absorber,
with the absorption maximum in the blue region of the visible light spectrum at a wavelength
of 470nm.
Discussion
Page 45
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 temperature. Most of the energy put into the halogen system is changed into
heat but a small portion is given off as light. Selective filters screen the wavelength so that
only blue light is emitted producing an energy density of approximately 400 mW /cm2
with a
broad bandwidth between 400 and 520 nm. Despite their popularity, halogen bulbs have
several shortcomings.36
Halogen bulbs have an effective lifetime of approximately 100 hours.
High heat is generated degrading the components of the halogen bulb over time and also long
curing time is needed with conventional halogen lights11
.
The argon laser introduced in the late 1980’s and early 1990’s are capable of curing in
only 10 seconds for filled resins and 5 seconds for unfilled resins at a wavelength of 488 nm.
For argon laser ,the light intensity approaches to 800 mW/cm2 and a narrow wavelength in
the blue green spectrum (457.9 to 514.5 nm) corresponding to the peak area of absorption of
camphoroquinone reduces the curing time making it ideally suited to polymerize composite
resins. In a study by Travis Q.Talbot et al
64 showed the use of argon laser to bond orthodontic
brackets can yield excellent bond strengths in significantly less time.
In mid 1990s xenon plasma arc light units have been introduced for rapid light curing in
restorative dentistry. The curing time with plasma arc curing lights range from 2 to 9 seconds
per bracket is as short as those with argon lasers. The emitted white light is filtered to
bandwidth of 450 to 500 nm and the power density can reach more than 2000 mW/cm2.
A study by Michael D. Signorelli,et al39
showed the plasma arc light with shorter curing time
such as 6, 10 seconds can produce similar bond strengths and bracket failure rates as using a
halogen light of 20 seconds curing time. Another study by Arndt Klocke et al4 evaluated the
bond strength of ceramic brackets cured with the plasma arc lights and concluded that a
Discussion
Page 46
curing interval of minimum 3 seconds is recommended for both monocrystalline and
polycrystalline ceramic brackets.
Mills et al in 1995 proposed solid state light emitting diode (LED) technology for the
polymerization of light activated dental materials. LED’s produce visible light by quantum
mechanic effects.12,15
Recently attention towards making high power LED light source ( >
1000 mW/cm2
) is gaining popularity as with high power LED light source, more photons are
available for absorption by the photosensitizers which react with the amine and form free
radicals for polymerization. Nowadays alternative photoiniators to camporoquinone are
available because camporoquinone has an intense yellow colour, in the field of restorative
dentistry photo initiators such as lucirin TPO are employed in the formulations of composites
in shades and in colourless protective varnishes. The peak sensitivity of lucirin TPO is
nearing the UV range around 390 nm whereas for camporoquinone the peak sensitivity is
near 470nm in the blue wavelength. This made a shift towards polywave LED curing light1,72
as previously available curing units emitted narrower light spectra around 468 nm in the
absorption spectrum of camporoquinone whereas newer generation polywave LED achieves a
broader spectrum of wavelength ranging from 380 to 515nm, similar to the spectrum of
halogen.1,2
The polywave curing lights are therefore suitable for polymerizing the entire
range of photoinitiators and currently available materials .
In literature many studies have been published comparing the LED light polymerization with
halogen or plasma arc curing lights in evaluating their clinical efficiency.11,39
Studies by
Maria Francesca Sfondrini, et al34,35,36
compared the enamel shear bond strength of composite
resin and glass ionomer when using conventional and high intensity light curing35
, also did a
12 – month clinical study of bond failures when using plasma arc versus halogen light36
and
in our study second generation monowave LED lights were compared with the recently
available third generation curing light with polywave technology available with high energy
Discussion
Page 47
intensity similar to plasma arc lights so the curing time can be shorter than using monowave
LED. Some studies suggest that higher light intensity can contribute to higher contraction
strains during resin polymerization and contraction stresses may contribute to insufficient
shear bond strength.20,35
So the high intensity polywave LED is compared with low intensity
monowave LED curing light in curing orthodontic brackets.
In previous research by Hakan Turkkahraman et al,20
comparison of the shear bond strength
of orthodontic metal brackets by two high power light emitting diode modes and halogen
light were made. In this study, the shear bond strength results of fast mode LED curing of 20
seconds is similar to the halogen based illumination of 40 seconds.
In the present study the curing time for high intensity polywave curing light (bluepase style-
Ivoclar vivadent) group is less (10 seconds / bracket) and the mean bond strength obtained for
the metal bracket (metal polywave - group II) is 10.69 MPa which is similar to the result
obtained in the study conducted by Timothy Swanson et al62
where their 64 LED curing light
( GC e-light) group showed mean bond strength of 8.1 MPa and 19 LED curing light (Elipar
Free light)with mean bond strength of 13.5 MPa, 2 LED unit ( Ultra Lume LED 2) with mean
bond strength of 12.3 MPa. The LED lights used in other studies were second generation
monowave / single peak LED device. So the bond strength obtained with polywave LED is
clinically significant to withstand normal orthodontic forces. The mean bond strength
obtained with (Group I) monowave LED ( blue phase C5) is 10 MPa but the curing time of
bracket was 20 seconds / bracket. So using high intensity polywave LED is advantageous
over monowave LED in terms of shorter polymerization times.
Cornelia Speer et al14
conducted an invitro study in which the bond strength of ceramic
bracket bonded with Transbond XT adhesive ,Ortholux XT curing light (3M Unitek)
polymerization time of 20 seconds / bracket was 28.5 MPa and similar results were obtained
Discussion
Page 48
in the present study with ceramic bracket bonded with Transbond XT with mean bond
strength of 23.27 MPa for monowave LED (Group III ) and 24.44 MPa for polywave LED
(Group IV ). For ceramic brackets also the polymerization time is shorter for polywave LED
( 10 seconds / bracket ) than monowave LED ( 20 seconds / bracket ).
When the shear bond strength of metal and ceramic brackets are compared, the bond strength
of ceramic bracket is higher than the metal bracket for both the LED lights which is similar to
the studies involving metal and ceramic brackets.14,49
For ARI – Adhesive remnant index system, we followed the scores of Artun and Bergland to
evaluate the amount of adhesive left on the tooth after debonding in an optical
stereomicroscope under 10 X magnification and the ceramic brackets tend to have retained
their adhesive on the bracket base than the metal brackets but the results showed no
statistically significant difference in the frequency distribution of the ARI scores. In the
ceramic bracket groups(Group III, Group IV) there is an enamel crack in one tooth
corresponding to each group. Eventhough the enamel crack occurrence is rare, the ceramic
bracket always carries a risk of enamel fracture.49
Summary and Conclusion
Page 49
SUMMARY
This study evaluated the shear bond strength of orthodontic metal and ceramic brackets cured
with the two different LED curing units – the second generation LED light with monowave /
single peak polymerization technology and the third generation with the polywave /dual peak
polymerization technology with broad wavelength and high intensity which was projected
as the one that can cure all types of light cure products currently available in the market.
This study was done to know the orthodontic performance of the light cure units in curing the
metal and the ceramic brackets.
CONCLUSION
The shear bond strength test in an universal testing machine showed similar bond strength
for metal bracket cured with monowave and polywave LED but time of polymerization is less
for the polywave LED and also the results of ceramic bracket cured with polywave and
monowave LED were also similar. So polywave LED can efficiently serve the orthodontic
curing purpose and as the broad emission spectrum of wavelength produced by the polywave
LED can cure all the light cure materials currently available in the market, it is advantageous
for orthodontists to have a polywave LED in clinical setup.
References
Page 50
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