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1. A COMPARATIVE EVALUATION OF
SHEAR BOND STRENGTH OF
ORTHODONTIC BRACKETS BONDED TO
PORCELAIN FUSED METAL CROWNS
TREATED WITH DIFFERENT SURFACE
CONDITIONING TECHNIQUES – AN
INVITRO STUDY
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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2. CONTENTS







INTRODUCTION
AIMS AND OBJECTIVES
REVIEW OF LITERATURE
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION
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3. INTRODUCTION

The introduction of acid etch bonding technique by
Buonocore in 1955, brought the concept of bonding
various resins to enamel with applications in all fields of
dentistry, including orthodontics.

With the development of reliable and reproducible
bonding techniques to enamel surfaces, cemented bands
were replaced by bonded brackets on incisor, cuspid and
bicuspid teeth.

Newman 1965 was the first person who used epoxy resin
for bonding stainless steel brackets to enamel
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4. 
By the late 1970s bonding of orthodontic brackets had
become an accepted clinical technique in routine fixed
appliance treatment.

With the increased number of adults seeking orthodontic
treatment, clinicians often have to bond orthodontic
brackets to teeth that have different types of restorations,
including amalgam, gold, composite and porcelain.

Various methods have been tried to improve the bonding
of orthodontic brackets to porcelain surfaces by pretreating porcelain surface by mechanical or chemical
means, or by a combination of both.
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5. AIMS AND OBJECTIVES




(1) To compare the effect of different surface
conditioning methods on bond strength, when
orthodontic brackets are bonded to porcelain fused metal
surfaces.
(2) To compare the bond strength of brackets bonded to
porcelain-fused-to-metal surface with bonding on natural
teeth as control.
(3) To assess the type of bond failures using scanning
electron microscope
(4) To discuss a more reliable and least variable surface
conditioning method for bonding brackets to porcelain
fused metal surfaces.
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6. Review of Literature


Ozcan M, Vallittu PK et al., (2004) evaluated the effects
of 5 different surface conditioning methods on the bond
strength of polycarbonate brackets bonded to ceramic
surfaces with resin based cement.
The specimens were randomly assigned to one of the
following treatment conditions of the ceramic surface:
(1) orthophosphoric acid, primer, bonding agent,
(2) hydrofluoric acid gel, primer, bonding agent,
(3) tribochemical silica coating (silicon dioxide 30µm)
silane,
(4) airborne particle abrasion (aluminum trioxide 30µm)
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silane,

7. & (5) airborne particle abrasion (aluminum trioxide,
30µm) silane, bonding agent

Results showed that brackets treated with silica coating
with silanization had significantly greater bond strength
values (13.6 MPa,) than brackets treated with
orthophosphoric acid (8.5 MPa).
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8. MATERIALS AND METHODS

The present study was conducted in the Department of
Orthodontics and Dentofacial Orthopedics, Sibar
Institute of Dental Sciences, Takkellapdu, Guntur and
Department of Organic Coatings & Polymers, Indian
Institute of Chemical Technology, Habsiguda,
Secunderabad

Sixty human maxillary premolar teeth extracted for
therapeutic purposes from patients seeking orthodontic
treatment in the Department of Orthodontics and
Dentofacial Orthopedics, Sibar institute of dental
sciences were collected & stored in normal saline after
treating them with hydrogen peroxide for one week. 8
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9. Inclusion & Exclusion Criteria for Teeth
Selection:

Teeth with no signs of caries

Teeth free of restorations

Teeth with no cracks on the crown as a result of the
pressure of the extraction forceps.

Teeth with no cement remnants as a result of previous
orthodontic treatment.

Teeth with fluorosis, hypoplasia or abnormalities of
crown morphology, which may have affected bracket
bonding, were excluded.
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10. TEETH MOUNTED IN
ACRYLIC BLOCKS
GLASS IONOMER CEMENT USED TO
CEMENT PFM'S ON EXTRACTED 10
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MAXILLARY PREMOLARS

11. 
Fifty Porcelain Fused Metal crowns were fabricated over
the extracted maxillary premolar teeth after crown
preparation for the study purpose,

and ten extracted natural maxillary premolar teeth were
acid etched in conventional manner using 37%
phosphoric acid for 30 seconds

Composite bonding was done which acted as controls to
compare the bond strength with Porcelain Fused Metal
crowns.
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12. MATERIALS USED FOR
THE STUDY
DENTSPLY QHL75 LITE USA
VISIBLE LIGHT CURING UNIT
AND OTHER BONDING
MATERIALS USED IN THE
STUDY
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13. Methods

Bonding procedure: The teeth collected were grouped
into six groups of ten each (Group I to Group VI)

And Following six protocols were executed for surface
preparation.

Group I: Orthodontic brackets were bonded to enamel
surfaces on ten teeth in Group I which acted as control
group, teeth were acid etched with 37% phosphoric acid
gel for 30 seconds, thoroughly washed, and air dried using
3-in-1syringe, followed by application of primer &
bonding agent (Transbond XT 3M, light cured composite
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resin).

14. 
Group II: etched with 37% phosphoric acid gel for 30
seconds, teeth were thoroughly washed, and air dried using
3-in-1syringe, followed by application of primer & bonding
agent.

Group III: etched with 9% Hydrofluoric acid for 90
seconds

Group IV: were air abraded using 30 µm aluminum oxide
particles from 10 mm distance with 250 Kpa pressure for 23 seconds using sand blaster machine, & etched with 9%
Hydrofluoric acid for 90 seconds,.
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15. FINE DIAMOND BUR 30 µm
BRASSELER LEMGO
GERMANY
SAND BLASTING WITH 30 µm
ALUMINUM OXIDE PARTICLES
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16. 
Group V: were air abraded using 30 µm aluminum oxide
particles from 10 mm distance with 250 Kpa pressure for 23 seconds using sand blaster machine, followed by two
coats of silane coupling agent application and air dried.

Group VI: Orthodontic brackets were bonded on ten
Porcelain Fused Metal crowns belonging to Group VI,
which were roughened using Fine diamond bur 30 μm.

Subsequent to bonding, the samples were stored in
distilled water at physiological temperature (37ºC) for 1
day,
and thermocycled 500 times between 5°C and 55°C with a
dwelling time of 30 seconds using a computerised
thermocycling device (Nova Inc., Konya, Turkey) prior to
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shear bond strength testing.


17. SILANE APPLICATION
FINE DIAMOND BUR
ROUGHENING
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18. BRACKET PLACEMENT
LIGHT CURING AFTER
BRACKET PLACEMENT
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19. 
Shear Bond Strength Testing In order to maintain a
consistent debonding force in a controlled direction, teeth
were mounted on to an acrylic jig. Facial surface of the
porcelain crown was kept exactly parallel to the debonding
force or perpendicular to the floor.

SBS was recorded with a universal testing machine (Autograph
Model AGS 10 ANG, Shimadzu, Japan).

A crosshead speed of 1mm/min
was used.
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20. 
Debonded surfaces were observed under a scanning
electron microscope for the types of failures after the
debonding procedure.

Following debonding, the surfaces under the debonded
brackets were coated with gold and palladium solution to
prepare the specimens for viewing under scanning electron
microscope model Hitachi- S520, Japan; Oxford Link ISIS300 UK at 500x and 1500x magnifications.
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21. RESULTS

The data was normally distributed and the results were
tabulated and statistically analyzed using the S.P.S.S. 10
statistical analysis package software.

Shear bond strength in Megapascals (Mpa) and Standard
Deviation (±SD) for shear bond strength of brackets
bonded to porcelain fused metal surfaces were
represented individually by tables for easy observation.
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22. 
maximum mean shear bond strength of a sample

belonged to group V which was sandblasting with silane
application 12.34 ± 0.95 Mpa
and minimum belonged to group II which was acid
etching with 37% phosphoric acid gel for 30 seconds 5.51
± 0.88 MPa.

9% Hydrofluoric acid (group III) showed the second
highest shear bond strength mean values 11.48 ± 0.98
MPa.

group IV which was Sandblasting and 9% Hydrofluoric
acid showed a bond strength of 7.96 ± 1.07 MPa
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23. and group VI which was Fine diamond bur roughening with silane
application showed mean values of 9.28 ± 1.11 MPa
and group I which was control group (37% phosphoric acid) showed
shear bond strength mean values of 11.03 ± 1.63 MPa
Table I: Summary statistics according to groups
Groups
Minimum
Maximum
Range
Mean
Std.Dev.
SE
Median
Group I
9.01
13.61
4.60
11.03
1.63
0.51
10.84
Group II
3.82
7.01
3.19
5.51
0.88
0.28
5.52
Group III
10.11
13.54
3.43
11.48
0.98
0.31
11.29
Group IV
6.22
9.49
3.27
7.96
1.07
0.34
8.10
Group V
10.98
13.93
2.95
12.34
0.95
0.30
12.08
Group VI
7.27
11.21
1.11
0.35
9.16
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3.94
9.28
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24. 7.96
9.28
11.03
10.00
5.51
8.00
6.00
Group III
Group IV
1.11
1.07
Group II
0.95
0.98
2.00
0.88
4.00
1.63
Mean shear bond strength
12.00
11.48
14.00
12.34
Figure: Comparison of mean shear bond strength in six groups
0.00
Group I
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Mean
Group V
Std.Dev.
Group VI
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25. 
Parametric tests for comparison of six groups by one way
ANOVA test and Pair wise comparison of six groups by
Newman-Keuls multiple comparison post hoc
procedure were done.

Both the tests showed significant difference between and
within the groups in shear bond strength and P value also
was highly significant, i.e. ***p<0.001.
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26. Scanning Electron microscope Results

The SEM photomicrographs of all the six different surface
preparations revealed different surface morphologies.

For the porcelain-fused-metal crowns treated with 30 μm
Al2O3 and Fine diamond bur 30 μm, loss of the glazed
surface and mild roughening were seen.

Uniform peeling or an erosive appearance with shallow
penetration and undercuts was observed when compared
with chemical etching.
Hydrofluoric acid etching demonstrated mild roughening
of the surface and orthophosphoric acid etching produced
minimal change and did not appear to alter the glazed 26
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porcelain surfaces.


27. CONTROL GROUP
ORTHOPHOSPHORIC ACID AT
500 X (GROUP I)
CONTROL GROUP
ORTHOPHOSPHORIC ACID AT
1500 X(GROUP I)
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ORTHO PHOSPHORIC ACID AT 550 X
ORTHO PHOSPHORIC ACID AT
1500X(GROUP II)
(GROUP II)

28. HYDROFLUORIC ACID AT 500 X
(GROUP III)
HYDROFLUORIC ACID AT 1500 X
(GROUP III)
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SAND BLAST + HF ACID AT 500 X
SAND BLAST + HF ACID AT 1500 X 28
(GROUP IV)
(GROUP IV)

29. SAND BLSATING + SILANE AT
500 X
(GROUP V)
SAND BLSATING + SILANE AT
1500 X
(GROUP V)
FINE DIAMOND BUR ROUGHENING
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FINE DIAMOND BUR ROUGHENING AT
AT 1500 X(GROUP VI)
500 X(GROUP VI)

30. Discussion
 Even though the clinical relevance of in-vitro studies is
considered to be limited, the mean shear bond strengths of
metal brackets to ceramic surfaces in this study generally
exceeded acceptable limits (except for 37% phosphoric acid)
and therefore can be considered sufficient for clinical
situations.
 The clinical forces may dislodge the brackets in single
traumatic incident (comparable to the universal debonding
machine in vitro) or as a result of repeated stresses.
 To overcome the above said limitations thermocycling is
required to test the bond strength of brackets to ceramics, as
it induces artificial aging and stresses at the level of various
thermal expansion coefficients of metal, resin and ceramic
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materials.

31. Group I - 37% Phosphoric acid
 Orthodontic brackets bonded to enamel surfaces on ten
natural teeth gave clinically acceptable and significant
bond strength of 11.03 ± 1.63 MPa.
Group II - 37% Phosphoric acid
 Porcelain surface preparation using 37 % Phosphoric acid
gave significantly low SBS of 5.51 ± 0.88 MPa. These
results were not in acceptable range for the orthodontic
bonding.
Group III - 37% Hydrofluoric acid
 Preparation with Hydrofluoric acid (HFA) produced
significantly high bond strength of 11.48 ± 0.98 MPa,
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which was similar to the reports of previous studies.

32. 
Surface conditioning with HFA successfully increased
the adhesion of the composite resin to the porcelain
surfaces by producing physical or topographical changes
in the porcelain surface.

This was an expected result as HFA facilitates
micromechanical retention between porcelain and
composite resin.
When the two acids, HFA and Phosphoric acid were
compared, higher bond values were obtained in the HF
acid treated group.

- However, HFA should be used with great care as it is
capable of causing severe trauma to soft tissues and tooth
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substance (Hayakawa et al., 1992).

33. Group IV – Sand blasting + Hydrofluoric acid
 In the mechanical preparation we used sandblasting in
combination with 9% hydrofluoric acid etching and bracket
bonding with composite material.

Surface preparation with 30 µm Al2O3 particles produced a
uniform peeling appearance of the porcelain with deeper
penetration and more undercuts compared to roughening;
which increased potential mechanical retention.

Hydrofluoric acid further acted by dissolving the crystalline
and glassy phase of the ceramic(But this combination also
seemed to cause irreversible alteration to the porcelain surface)
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34. Group V – Sand blasting + Silane

Gave the maximum SBS value in this study, which is
12.34 ± 0.95 MPa.

These results were comparable to the previous studies done
by Kocadereli et al. and Schmage et al. In contrast,
Zachrisson reported earlier to these studies that silane
application to sandblasted porcelain did not provide
clinically acceptable bond strengths and suggested
abandoning this technique.
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35. 
In a study carried out by Tamer Türk et al. stated that
samples coated with silane, but not exposed to chemical or
mechanical roughening, were considered as the control
group but demonstrated bond failures during
thermocycling.

Barbosa et al. (1995) reported the premature loss of
brackets bonded to glazed ceramic surfaces coated with
silane after 7 days of water immersion.

They explained that this premature loss was due to the
high solubility of silane in water.
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36. Group VI – Fine Diamond Bur roughening + Silane
- Gave an SBS of 9.28 ± 1.11 MPa.
 Barbosa et al. (1995)In their study stated that roughening
with coarse diamond burs resulted in higher SBS when
compared with other groups, i.e. glazed and deglazed
surfaces with sandpaper disks.

Silane presents a chemical link between the dental
ceramic and the composite resin, and the organic portion
of the molecule enhances the wettability of the ceramic
surface, thereby displaying a closer micromechanical
bond (Lu et al., 1992).

However, in order to obtain a viable bond between the
orthodontic bracket and the ceramic surface, mechanical
or chemical roughening is inevitable (Wood et al., 1986;
Kao et al. , 1988 www.indiandentalacademy.com , 1995 ; Gillis and
; Barbosa et al.
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Redlich,1998 ; Huang and Kao, 2001

37. Shortcomings of the study

Although the results obtained in this study can be
helpful for selection of the most effective method for
bonding orthodontic brackets to PFM’s clinically, it is
important to be updated with the continuous
development of newer ceramic systems used these days.

This study was carried out only on feldspathic ceramics
with porcelain fused metal surfaces, and didn’t consider
all ceramic crowns, other ceramic types like Zirconia
based ceramics, leucite or lithium disilicate, composite
restoration surfaces.
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38. 



Conclusion
Sand blasting followed by application of Silane (group V)
produced maximum bond strength comparable or even
better than the control group followed by groups III and
VI.
37% Ortho Phosphoric acid (group II) produced least SBS
and hence not suitable for bonding Othodontic brackets in
a clinical scenario.
Even though groups III and VI produced clinically
acceptable SBS values, because of their technique
sensitivity and side effects, they have to be used with great
care and caution.
The best porcelain surface conditioning method
recommended clinically for bonding Orthodontic brackets
to porcelain fused metal crowns was sand blasting
followed by the application of Silane coupling agent. 38
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