Download 7.3 - Rajiv Gandhi University of Health Sciences

Rajiv Gandhi University of Health Sciences, Bangalore,
Karnataka.
MDS ORTHODONTICS & DENTOFACIAL ORTHOPEDICS
Synopsis for Registration of Dissertation.
M. R. Ambedkar Dental College and Hospital
#1/36, Cline Road, Cooke Town,
Bangalore, Karnataka- 560005.
RAJIV GANDHI UNIVERSITY OF HEALTH SCIENCES
KARNATAKA, BANGALORE.
ANNEXURE II
SYNOPSIS FOR REGISTRATION OF DISSERTATION
1
2
NAME OF THE CANDIDATE AND
ADDRESS
NAME OF INSTITUTION
Dr. PRIYANKA
Dept. Of Orthodontics
M. R. Ambedkar Dental College & Hospital
#1/36, Cline Road ,Cooke Town
Bangalore-560005.
M. R. Ambedkar Dental College & Hospital
#1/36, Cline Road ,Cooke Town
Bangalore-560005.
3
COURSE OF STUDY AND SUBJECT
M.D.S ORTHODONTICS
4
DATE OF ADMISSION
18/04/2009
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TITLE OF THE TOPIC:
“COMPARISON OF SHEAR BOND STRENGTHS OF PRECOATED AND UNCOATED
BRACKETS USING LED AND HALOGEN CURING LIGHTS” – AN IN VITRO STUDY.
6
BRIEF RESUME OF WORK:
6.1
NEED FOR STUDY:
Success of a bond can be ascertained by a number of ways including measurement of bond
strength in vitro, measurement of the failed proportion of brackets in vivo, and ex vivo studies utilizing
finite-element analysis. In vitro shear bond strength recording is the easiest method among these.
Reynolds (1975) stated that successful clinical bonding can be achieved with bond strengths from 6-8
MPa and above.1 Adhesive remnant index (ARI; Artun and Bergland, 1984) and modified adhesive
remnant index (Bishara et al, 1999) can be used to determine the nature of bond failure and determine
the site of fracture when a bracket debonds.
One of the main objectives of the research of bonding procedures is to seek ways of reducing
chair side time. Adhesive Precoated Brackets (APCs) (introduced in 1991) have improved the quality
and accuracy of orthodontic bonding by reducing the steps in bonding procedures, owing to the
consistent quality and quantity of adhesive used, better asepsis, less wastage, easy flash removal and
a better control of inventory. Various studies comparing the bond strengths of APC brackets and
conventional uncoated brackets have yielded contradictory results. Certain in vitro studies shows that
APC brackets have a bond strength similar to conventional brackets whereas other studies maintain
that their bond strength is low.2
Visible light has been the most popular method of polymerizing orthodontic adhesives.
Application of visible light-curable composite for bonding was first described by Tavas and Watts
(1979) and subsequent studies have confirmed that adequate bond strength can be achieved with
visible light curing systems used for bonding on to enamel. Blue light generated by conventional
halogen light curing unit has been the most popular method of polymerizing orthodontic adhesives
despite its shortcomings like degradation of lamp, filter, reflector, reduced light intensity, broad
spectrum of light, and prolonged curing time which can be uncomfortable to patient. In 1995 Mills et
al and Nakamura et al proposed LED (light emitting diode) as an alternative to the halogen curing
light.
Several studies have evaluated the clinical efficacy of LED light for bonding orthodontic
brackets and have been unable to demonstrate a significant difference between the bond strength
obtained with an LED light curing and a halogen light curing device. Effect of curing at different
polymerization times has also been evaluated and bonding brackets with LED at shorter exposure
time seems to be a good alternative but further studies are still necessary if its use is to be
recommended in orthodontic practice. Therefore this study is undertaken to compare the shear bond
strength of adhesive precoated and uncoated brackets cured using two different curing units: a
conventional halogen light and a light emitting diode, to evaluate the effect of different exposure
times and different exposure methods (single exposure and exposure from two sides mesial and
distal) on shear bond strength of adhesive precoated brackets cured using light emitting diode and the
amount of remnant adhesive on tooth surface after debonding.
6.2
REVIEW OF LITERATURE:
An in vitro study was conducted to compare shear bond strength of precoated and uncoated
brackets. It was concluded that precoated ceramic brackets using a modified adhesive showed
similar shear bond strengths as provided by Transbond XT adhesive on uncoated brackets.
Precoated metal brackets showed lower shear bond strength than obtained with Transbond XT on
uncoated brackets. The difference in shear bond strength between the ceramic and metal brackets
were attributed to the combined effects of the changes in the composition of adhesive used and
retention mechanisms incorporated in different bracket bases. All bracket/adhesive combinations
provided clinically acceptable shear bond forces.3
A clinical study conducted to evaluate the LED versus halogen light curing of adhesive
precoated brackets showed no significant difference in bond failure rates. Significantly lower
bonding failures were observed in the maxillary arch when compared to the mandibular arch.
Clinical application of LED curing light associated with APC was a clinically valid procedure
which may reduce the time necessary to carry out bonding without leading to an increasing number
of detachments over time.2
A 15 months clinical study of bond failures of orthodontic brackets cured with the halogen light
and the LED unit showed no significant differences between the percentage of bond failures with
the two lights when the clinical performances of the maxillary versus mandibular arches and
anterior versus posterior segments were compared. LED was considered to be an advantageous
alternative as it significantly reduces curing time.4
An in vitro study evaluating the bond strength of metallic brackets photo- activated with light
emitting diode at different exposure times concluded that exposure time had no influence on the
shear bond strength values of brackets bonded using LED curing light and there was no difference
in bond strength of brackets cured using halogen light and LED. Bonding bracket with LED at
shorter exposure times of 5 or10 seconds was a good alternative for reducing chairtime.5
An in vitro study of shear bond strength of APC Plus precoated brackets and uncoated
brackets bonded with Transbond XT adhesive using self-etching primer Transbond Plus Self-
Etching Primer (TPSEP) proved the hypothesis that there was no significant difference in shear
bond strength between the two systems tested. The percentage of area of adhesive remaining on
tooth was more with TPSEP/Transbond XT than TPSEP/APC Plus.6
An in vitro study conducted to evaluate the effect of high intensity LED units at reduced
curing time on bond strength of orthodontic brackets revealed there was no difference in bond
strength between high intensity LEDs and halogen based light. The amount of adhesive remaining
on enamel after debonding was significantly higher when using high intensity LED units than when
using halogen based light and was advantageous as bond failure at the bracket-adhesive interface or
within the adhesive was more desirable than at the adhesive enamel interface, in order to avoid
enamel fracture at the time of debonding. Use of high intensity LED curing units was adequate for
orthodontic bonding, even if the exposure time was reduced to 10 seconds.7
6.3 AIMS AND OBJECTIVES OF THE STUDY:
The aim of this in vitro study is to:

Compare the shear bond strengths of conventional uncoated and adhesive precoated brackets
cured using two different light curing units: halogen and light emitting diode (LED).

Compare the shear bond strength of adhesive precoated brackets cured using light emitting
diode (LED) at different exposure times and using different exposure methods (single exposure
and exposure from two sides: mesial and distal).

To test the hypothesis that light emitting diode (LED) requires half the curing time as
compared to halogen curing light.

Compare the amount of remnant adhesive on the teeth after debonding.
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MATERIALS AND METHODS:
7.1 SOURCE OF DATA:

One hundred and forty extracted human premolars free from caries and fillings.

One hundred adhesive precoated and forty conventional uncoated metal brackets (Gemini
series, 3M Unitek, Monrovia, Calif.)

Adhesive: Transbond XT (3M Unitek Dental Products) with conventional primer.

Polymerization source:
Halogen light curing unit (3M ESPE, ELIPAR ,2500)
LED light emitting diode curing unit (3M ESPE, ELIPAR,S10 )
 Measuring shear bond strength with a universal testing machine (Instron 4301, Canton, Mass)
with a load of 10N.
7.2 METHODOLOGY:
 Investigation will be carried out on one hundred and forty human premolar teeth extracted for
orthodontic treatment with the consent of patient. Teeth will be washed, placed in 1% thymol
solution and stored in distilled water till further use.
 Buccal surfaces of teeth will be etched with 37% orthophosphoric acid gel for 30 seconds
followed by thorough washing and drying.
 One hundred and forty premolars will be divided into seven groups of twenty each. Adhesive
precoated and conventional uncoated brackets will be bonded following manufacturer’s
instructions. Adhesive precoated brackets will be divided into five groups and conventional
uncoated brackets will be divided into two groups and curing will be done using both LED
and halogen curing units according to the following -
SL. NO.
TYPE OF BRACKETS
CURING
LIGHT
TIME
EXPOSURE METHOD
1
Conventional
uncoated
Halogen
40
seconds
20 seconds each from mesial and distal
2
Conventional
uncoated
LED
20
seconds
10 seconds each from mesial and distal
3
Adhesive precoated
20 seconds each from mesial and distal
Halogen
40
seconds
10 seconds each from mesial and distal
LED
20
seconds
20
seconds
Single exposure
LED
Single exposure
LED
15
seconds
Single exposure
LED
10
seconds
4
Adhesive precoated
5
Adhesive precoated
6
Adhesive precoated
7

Adhesive precoated
Specimens will be immersed in distilled water for 24 hours and will be tested in a shear mode
on a universal testing machine (Instron 4301, Canton, Mass).

After debonding, each tooth will be assigned a modified adhesive remnant index (ARI) value.
The ARI scale ranges from 1 to 5:
1.
All of the adhesive remaining on the enamel, with the impression of the bracket base.
2.
More than 90 % of the adhesive remaining on the enamel surface.
3.
Less than 90 % but more than 10 % of the adhesive remaining on the enamel surface.
4.
Less than 10 % of the adhesive remaining on the enamel surface.
5.
No adhesive remaining on the enamel surface.
7.3 ANALYSIS OF DATA:
The data of shear strength will be evaluated by Weibull analysis. Differences between the groups
will be evaluated by a two- way analysis of variance (ANOVA). The chi-square test will be used
to determine significant differences in the adhesive remnant index ( ARI) scores between the
different groups.
DOES THE STUDY REQUIRE ANY INVESTIGATIONS TO BE CONDUCTED ON
7.4 PATIENTS ON OR OTHER HUMANS OR ANIMALS? IF SO, PLEASE DESCRIBE
BRIEFLY.
Not applicable.
HAS ETHICAL CLEARANCE BEEN OBTAINED FROM YOUR INSTITUTION IN CASE
7.5 OF 7.4
Yes
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REFERENCES:
1. Reyonlds IR. A review of direct orthodontic bonding. Br J Orthod. 1975;2:171-178.
2. Mirabella D et al. LED vs halogen light curing of adhesive precoated brackets. Angle Orthod.
2006;76:935-940.
3. Bishara SE, Olsen M, Wald VL. Comparison of shear bond strength of uncoated and precoated
brackets. Am J Orthod Dentofacial Orthop. 1997;112:617-621.
4. Krishnaswami NR, Chakravarti S. Light emitting diode vs halogen light curing of orthodontic
brackets: a 15 month clinical study of bond failure. Am J Orthod Dentofacial Orthop.
2007;132:518-523.
5. Rego EB, Romano FL. Shear bond strength of metallic brackets photo-activated with light
emitting diode (LED) at different exposure times. J Appl Oral Sci. 2007;15(5):412-415.
6. Vicente A, Bravo LA. Shear bond strength of precoated and uncoated brackets using a selfetching primer. Angle Orthod. 2007;77:524-527.
7. Palomares NB, Cal-Neto JP, Filho HS, Oliveira MA, Mendes JA. Effect of high intensity LED
units at reduced curing time on in vitro bond strength of orthodontic brackets. World J Orthod.
2008;9:203-208.
9.
10.
11.
11.1
11.2
11.3
SIGNATURE OF THE CANDIDATE
REMARKS OF THE GUIDE
NAME AND DESIGNATION OF THE GUIDE
DR. RABINDRA S.NAYAK
PROF. DEPARTMENT OF
ORTHODONTICS AND DENTOFACIAL
0RTHOPEDICS
SIGNATURE
NAME AND DESIGNATION OF CO-GUIDE
DR.AZAM PASHA
ASSO. PROF.
DEPARTMENT OF ORTHODONTICS AND
DENTOFACIAL 0RTHOPEDICS
SIGNATURE
11.4
HEAD OF THE DEPARTMENT
11.5
SIGNATURE
11.6
REMARKS OF THE PRINCIPAL
11.7
SIGNATURE
DR.K. A. MOHAN
PROF. AND HEAD OF DEPARTMENT OF
ORTHODONTICS AND DENTOFACIAL
0RTHOPEDICS