COMPARISON OF SHEAR BOND STRENGTH OF ORTHODONTIC … · 2018-12-07 · comparison of shear bond...

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.


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


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.


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


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


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.


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


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,


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.


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%


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.


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


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.


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


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.


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


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


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


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


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


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.


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 )


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


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.


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.


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.


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


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


Page 34

FIGURE 3 – TEETH SAMPLES MOUNTED IN ACRYLIC BLOCKS

Total of 80 samples

4 groups of 20 samples Acrylic used for the blocks


Page 35

FIGURE: 4 - LIGHT CURING METHOD

FIGURE 4 - LIGHT CURING METHOD


Page 36

FIGURE 5 – UNIVERSAL TESTING MACHINE AND THE SHEAR TEST

FIGURE 5 - UNIVERSAL TESTING MACHINE AND THE SHEAR TEST


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


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


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


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


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.

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Page 50

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