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Braz J Oral Sci. October/December 2003 - Vol. 2 - Number 7
Evaluation in vitro of the shear bond
strenght of aluminun oxide recycled
brackets
Stenyo Wanderley Tavares1
Simonides Consani2
Darcy Flávio Nouer3
Maria Beatriz Borges de Araújo
Magnani3
João Sarmento Pereira Neto3
Fábio Lourenço Romano4
1
DDS, MS, PhD student, Department of
Orthodontics, University of Campinas –
Piracicaba Dental School - Brazil
2
DDS, MS, PhD, Professor, Department of
Dental Materials
3
DDS, MS, PhD, Professors, Department of
Orthodontics, University of Campinas –
Piracicaba Dental School - Brazil
4
MS student, Department of Orthodontics,
University of Campinas – Piracicaba Dental
School - Brazil
Abstract
The aim of this study was to evaluate the shear bond strength of
recycled brackets with 90 and 50 µm aluminum oxide blasting. It was
used 30 human bicuspids, whom it was accomplished brackets bonding with composite resin chemically activated. The teeth were separated in 3 groups (n = 10). In group I (Control) brackets bonded after
enamel acid etching. In groups II and III brackets were rebonded after
recycling, respectively, by 90 and 50 µm aluminum oxide blaster.
Shear bond test was made in the Instron machine, with 0,5 mm/
minute speed and the results were submitted to ANOVA and Tukey’s
test (5%). The results showed no significant statistical difference
between recycled brackets by aluminum oxide and control group.
Recycled brackets by 90 and 50 µm aluminum oxide showed no
significant statistical difference.
Key Words
Recycling; aluminum oxide; shear bond strength
Received for publication: June 16, 2003
Accepted: October 31, 2003
Correspondence to:
Stenyo Wanderley TAVARES
Rua Coronel Barbosa 333/44
São Judas - Piracicaba - SP
CEP: 13416-120
e-mail: [email protected]
378
Braz J Oral Sci. 2(7): 378-381
Evaluation in vitro of the shear bond strenght of aluminun oxide recycled brackets
Introduction
The low retentiveness of certain bracket bases and the action
of oclusal forces are also major factors causing brachet
debonding. This fact is a frequent problem in Orthodontics
practice causing stress and delays in Orthodontic treatment
are also an economic disadvantage.
Recycling consists basically in removal of the remnant
bonding agent of the bracket basis, making the used bracket
able to reutilization, without damages to retention mesh,
keeping the retentive features1. Although clinical use can
produce little distortion in brackets, the removal phase is
responsible for most distortion and damages observed 2.
Brackets recycling can be performed by the immediate method
in the clinical practice, or by mediate method, that is performed
by specialized companies, without alteration in the position
of the “slots”3.
Two methods are commonly used for bracket recycling: 1Heat application for adhesive burning, followed by
electrolytic polishing for removal of oxide; 2- Use of chemical
solvents for adhesive dissolution, combined with high
frequency vibrations and electrochemical polishing4-7.
The immediate debonded bracket recycling can be performed
with Aluminum Oxide air abrasion. The increase of retentivity
in bracket bonding to dental structure by Aluminum Oxide
air abrasion occurs due to the micro-roughness production
by the process in the base surface, increasing its union area
to the composite, essentially mechanical union caused by
bonding of the composite to the retention mesh and to
existent micro-roughness.
There is not an agreement in the literature, concerning
the size particle used in recycled brackets by oxide
aluminum. The 90 µm particle was used in the following
studies 8-11. However other autors 12-13 recommended the use
of 50 µm particle for brackets recycling.
Although Aluminum Oxide air abrasion is a widely used
method for recycling in private practice and research, the
technique originally was devised to increase mechanical
retention of new brackets14, facilitating the bracket bonding
in restored teeth as well as conditioning enamel surface15.
The aim of this work was to evaluate in vitro shear
resistance of brackets bonded with chemically activated
composite after recycled by 90 and 50 µm aluminum oxide
air abrasion.
Materials and Methods
Thirty human premolar teeth were extracted for orthodontic
reasons, in the Surgery Clinics of Piracicaba Dental School.
Teeth were stored in 0,9% NaCl, at 4ºC for a maximum time of
six months before use. All experimental procedures were
according to the specification TR 11405 of the International
Organization for Standardization (ISO)16.
Teeth were individually fixed by the root in PVC tubes filled
with chemically activated acrilic resin Vipi Flash (Dentalvipi,
379
Pirassununga, SP).
Enamel conditioning was performed with 37% Concise gel of
phosphoric acid (3M, Nova Odessa, SP), during 30 seconds.
Enamel was then washed in water for 20 seconds and dried
for 20 seconds with soft air jet.
The bicuspid metal brackets (Dental Morelli, Sorocaba, SP)
were fixed in the central region of the buccal aspect of the
teeth. The chemically activated composite resin Concise
Orthodontic (3M) was used for bonding. After bracket
fixation, the samples were randomly separed in 3 experimental
groups (n=10):
Group I - Control : Brackets bonded by conventional
technique.
Group II – Aluminum Oxide air abrasion: Debonded brackets,
etched with 90 µm Aluminum Oxide Bio-art (São Carlos, SP)
and rebonded.
Group III – Aluminum Oxide air abrasion: Debonded brackets,
etched with 50 µm Aluminum Oxide Bio-art (São Carlos, SP)
and rebonded.
Bracket debonding of groups II and III was performed by
using a nipper (Starlet). Then, the residual resin was
removed from the tooth surface with multilaminated burs
KG Sorensen 9114F with handpiece (Dabi Atlante) in low
velocity17. Burs were changed by new ones after used in 5
teeth.
The residual resin remotion from group II and III brackets
were made with Aluminum Oxide air abrasion, with 90 µm and
50 µm particles, respectively, using the micro-etcher (BioArt) during 15 to 30 seconds, depending on the amount of
residual resin, keeping a 10 mm distance of the bracket base
10-11
. The rebonding of both recycled brackets and new
brackets was performed as descrebed in the initial fase of
bonding. Teeth were stored in humid incubators at 37o C for
24 hours. Shear bond strengths were determined with an
INSTRON universal machine (model 4411, Instron Corp.,
Canton, Mass.). Debonding was accomplished with
crosshead speed of 0.5 mm/minute. The needed force for
bracket debonding was measured in kgf. This value was
divided by the bracket bonding surface (14.7 mm2) obtaining
the shear bond strength in kgf/mm2. The bracket surfaces
were observed in Scanning Electron Microscopy (LEO 435
VP, Cambridge, England) for mesh evaluation before (group
I) and after debonding, as well as the recycled ones (groups
II and III). The shear bond strength test results were
submitted to Analysis of Variance and Tukey´s test, with 5%
significance.
Results
The average shear bond strength, measured in kgf/mm2 of
the groups and the test are summarized in Table I.
That shows that there was no statistically significant
differences in shear bond strength between Group I (Control)
and Groups II and III (90 and 50 µm aluminum oxide).
Braz J Oral Sci. 2(7): 378-381
Evaluation in vitro of the shear bond strenght of aluminun oxide recycled brackets
Table 1 -Shear bond strength mean values
GROUPS
MEAN (SD)
GROUP I (control)
0,5478 (± 0.237) a
GROUP III (50mm)
0,3625 (± 0.126) a
GROUP II (90mm)
0,3575 (± 0.144) a
Average followed by distinct letters differ between themselves in
significance level of P<0,05 (n=10)
Discussion
There are few articles regarding orthodontic brackets
recycling and the comparison of our results with others is
difficult, due to the several laboratorial proceedings
addopted.
Recycling debonded brackets is used to reduce the costs in
reposition of Orthodontic accessories. Aluminum Oxide air
brasion came as an option in brackets recycling, offering a
simple and practical technique that can be performed in dental
practice, avoiding time wasting, since brackets do not have
to be sent for specialized companies13.
The present study did not show statistically significant
difference in shear bond strength between Group I (Control)
and aluminum oxide air abrasion recycled brackets (Groups
II and III) (table I). This is in agreement to previous studies
11, 10
and with the work of Sonis8 that used GAC brand bracket
with base area of 9.9 mm2 and light cured resin. These authors
concluded that there was no statistically significant
difference in retention of jetted recycled brackets and new
brackets. However, Willems 11 related that efficiency of
sandblasting depends on bracket type.
The improved mechanical retention of the bracket to tooth
promoted by aluminum oxide air abrasion is due to the microroughness in the bracket base caused by this method (Fig. 2
and 3), when compared to control group (Fig.1). This
increased the union area to the composite 13.
Fig. 1 – Photomicrographic view (SEM) in 200x magnification, of
new bracket base (Group I)
Fig. 2 – Photomicrographic view (SEM) in 200x magnificcation of
the bracket base recycled with Aluminum Oxide jet (Group II)
Fig. 3 – Photomicrographic view (SEM) in 200x magnificcation of
the bracket base recycled with Aluminum Oxide jet (Group III)
The present study (table 1) showed that 90 µm and 50 µm
particles (0.3575 kgf/mm2 and 0.3625 kgf/mm2 , respectively)
of aluminum oxide sandblasting were effective in the recycle
process, since no statistically significant difference was
found for shear bond strength when compared to control
group (0.5478 kgf/mm2). In a similar study, Penido et al.10
also verified no statistically significant difference between
bracket recycled with 90 µm particles (0.4543 kgf/ mm2)
aluminum oxide air abrasion and control group (0.3906 kgf/
mm2 ).
For brackets recycling was recommended the use of 50 µm
Aluminum Oxide particles, whom promoted increased
brackets retention due to roughness formation12-13. However,
Sonis 8; Penido et al. 10 and Tavares11, showed that the 90
micrometers particles also produced higher micro-roughness
in the surface of the bracket base, increasing the disposable
area for union with the composite.
The use of Aluminum Oxide with either 90 or 50 µm particles
for bracket recycling had similar efficacy, due to the absence
of statistically significant difference between groups II and
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Braz J Oral Sci. 2(7): 378-381
Evaluation in vitro of the shear bond strenght of aluminun oxide recycled brackets
III (Table I). Consequently, the micro-roughness created by
different sized aluminum oxide particles promotes similar bonding
force between recycled brackets and Control (Table I).
In this work, the time used for Aluminum Oxide jetting was
15 to 30 seconds, keeping a 10 mm distance of the bracket
basis, what usually caused no damages to the accessory
mesh (Fig. 2 and 3). The same time distance interaction was
utilized by Penido et al.10 and Tavares11, showing results
similar to our study, what corroborates the technique
effectiveness. Millet et al.14 utilizing only 3 seconds for jet
new brackets before bondage in tooth, obtained satisfactory
results increasing roughness, without mesh damage.
This work allowed to demonstrate that brackets recycling
by means of aluminum oxide air abrasion (90 and 50 µm) is
efficient and technically simple. The brackets reutilization in
these conditions could reduce costs for clinician, and
consequently, for the patient.
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
381
Maccoll GA et al. The relationship between bond strenght and
base surface area using conventional and micro-etched foil-mesh
bases. Am. J. Orthod. Dentofacial Orthop. 1996; 109: 338-9.
Oliver RG, Pal AD. Distorcion of edgewise orthodontic brackets
associated with methods of debonding. Am. J. Orthod. 1989; 71:
65-71.
Hixson ME et al. Changes in brackets slot tolerance following
recycling of direct-bond metallic orthodontic appliances. Am. J.
Orthod. 1982 ; 81: 447-54.
4.Buchman DJL. Effets of recycling on metallic direct-bond
orthodontics brackets. Am. J. Orthod. 1980; 77: 654-68.
Mascia VE, Chen SR. Shearing strengths of recycled direct-bonding
brackets. Am. J. Orthod. 1982; 82: 211-6.
Maijer R, Smith DC. Corrosion of orthodontic brackets bases.
Am. J. Orthod. 1982; 81: 43-8.
Buchwald A. A three-cycle in vivo evaluation of reconditioned
direct-bonding brackets. Am. J. Orthod. 1989; 95: 352-4.
Sonis AL. Air abrasion of failed bonded metal brackets: a study
of shear bond strength and surface characteristics as determined
by scanning electron microscopy. Am.J.Orthod. Dentofacial
Orthop. 1996; 110: 96-8.
Willems G, Carels CEL, Verberke G. In vitro peel/shear bond
strength evaluation of orthodontic brackets base design. J. Dent.
1997; 25: 271-8
Penido SMMO, et al. Avaliação da resistência ao ciasalhamento
de bráquetes reciclados e novos recolados. Rev Dental Press
Ortod Ortop Facial 1998; 3: 45-52.
Tavares SW. Estudo in vitro da resistência ao cisalhamento de
bráquetes reciclados e novos [Thesis]. Piracicaba: Faculdade de
Odontologia de Piracicaba, Universidade de Campinas; 2002.
Newman GV, et al. Update on bonding brackets: an in vitro
survey. J. Clin. Orthod. 1994; 28: 396-402
Pinto AS, et al. A reciclagem de bráquetes na clínica ortodôntica.
Ortodontia 1996; 29: 63-7
Millet D, Mccabe JF, Gordon PH. The role of sandblating on
the retention of metallic brackets appllied with glass ionomer
cemeut. Br. J. Orthod. 1993; 201: 117-22.
Senay C, Iiken K, Ela A. The effect of enamel air abrasion on
the retetion of bonded metallic orthodontic brackets. Am J
Orthod Dentofacial Orthop. 2000; 117: 15-9.
International Organization for Standardization – Guidance on
testing of adhesion to tooth structure. ISO/TC106/SC 1 N236,
Resolution 6 1. – CD 1994; TR 11405, trieste, October.
17. Gandini Junior LG, et al. Avaliação de diferentes métodos de
remoção da resina remanescente ao esmalte dentário após
descolagem de bráquetes ortodônticos. Ortodontia 1995; 28:
53-60.