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Mohammad Hossein Toodehzaeim et al.
INTRODUCTION
Requests for orthodontic treatment in patients especially
adults are increasing.(1) The patients often have differ-
ent dental restorations such as porcelain or buccal amal-
gam restorations.(2) Firm bonding of orthodontic brack-
ets to restoration surfaces is a challenge in orthodontic
treatment (1, 3). It has been shown that the conventional
method is not effective in bonding orthodontic brackets
to restoration surfaces (4, 5). In recent years, different
methods have been suggested to overcome this problem.
Sandblasting and use of intermediate resin containing
4-META is the most common method used for surface
preparation in amalgam restorations (6, 7). Derya Ger-
mec et al (1) evaluated the shear bond strength of bracket
bonded to amalgam with different intermediate resins
including metal primer, Power Bond™ OLC and One-Step
Plus. There were no statistically signi cant difference
in mean SBS between the amalgam bonding groups
but it was signi cantly lower than the control group
(enamel) One of the most common techniques of surface
preparation for porcelain is deglazing the surface with
a diamond bur or sandblasting with aluminium oxide
particles(4). Hydro uoric acid (HFA) is used as a chemi-
cal preparation of the deglazed porcelain (8, 9). Grewal
Bach GK et al conducted a systematic review regarding
orthodontic bonding to porcelain. They concluded the
best method was etching with HF for 1 minute and rins-
ing for 30 seconds then drying followed by application
of HF and saline (2). Recently Reliance has introduced a
new product named assure plus and claimed it has the
ability to bond to every dental surface such as normal
and atypical enamel, amalgam and porcelain. Regard-
ing the various methods for bonding orthodontic attach-
ments on different restoration surfaces such as amalgam
and porcelain, using a simple method is worthwhile. The
aim of this study was to compare the shear bond strength
(SBS) of metal brackets bonded to amalgam using the
conventional and Assure plus method and also to com-
pare the shear bond strength of brackets bonded to por-
celain using the conventional and Assure plus method.
MATERIALS AND METHODS
In this study, 60 human maxillary premolar teeth,
extracted for orthodontic reasons, were collected. The
sample teeth were examined to make sure of the absence
of crack lines, dental caries or restorations. Then all the
sample teeth were washed and then disinfected using
.1% thymol solution for one week. The root of the teeth
were mounted in self-curing acrylic resin (Cold cure
acrylic, Acropars, Marlic Inc., Iran) so that the buccal
surface of the teeth was parallel to the shearing force
exerted by the blade of the instron device (Zwick Ltd,
Here_fordshire, UK) then the teeth were divided to three
groups. Group1 contained 12 samples, whilst groups 2
and 3 groups contained 24 samples.
In group1, the buccal surfaces of the teeth were
cleaned by a rubber cap and pumice, then washed for
10 seconds and dried. After wards they were etched with
37% phosphoric acid gel (Fine etch Co, Chung-cheong-
nam-do, South Korea) for 30 seconds, rinsed thoroughly
with water and dried with air spray until a frosty white
surface was revealed. one coat of Assure plus was applied
by brush on all surfaces and lightly dried with air to
evaporate the solvent, the stainless steel bracket bases
(Dentarum GmbH & CO.KG, Ispringen, Germany) were
coated with Light Bond (Reliance Orthodontic Products,
Inc., Ill, USA) adhesive and were placed at four-milim-
eters from the buccal cusp tip and
pressed lightly in the
position, then the extra composite was removed with a
dental explorer and the adhesive was cured using a light
curing unit( LED curing, Morita, Kyoto, Japan) for 20
seconds.
In group 2 a cavity (width 6 mm, length 7mm, axial
depth 2mm) was prepared in the buccal surface of teeth.
The cavity was lled with Non- gamma 2 amalgam
(Nordiska Dental AB, Angelholm, Sweden) and bur-
nished with a hand instrument then placed in water at
37c for 48 hours. Then the amalgam surface was rough-
ened using 50μm aluminium oxide powder (Korox 50;
Bego, Bermen, Germany) for 3 seconds from a 10mm
distance then rinsed and dried. The amalgam specimens
were divided in 2 subgroups. In group1 a thin Assure
plus layer was applied to the amalgam surface of the
teeth and brackets were bonded with Light Bond adhe-
sive, the brackets were placed at four-milimeters from
the buccal cusp tip on the center of the amalgam sur-
face and was cured with a light curing unit for 20 sec-
onds. In group 2 the conventional method was used.
One coat of metal primer (RMP; Reliance orthodontic
products) was applied by brush to the sandblasted amal-
gam and dried for 30 seconds then the brackets were
bonded with composite resin and cured. In group 3, 24
glazed metal-ceramic crowns (Ceramco, Dentsply, York,
PA; Heraus Kulzer, Hanau, Germany) were fabricated
for maxillary premolar teeth, that were xed in a acri-
lyc block. The samples were then sandblasted at 2.5 bar
pressure for 4 seconds, rinsed and dried and then, ran-
domly divided in to 2 subgroups. In group 1 one coat of
porcelain conditioner (Silane BondEnhancer; Pulpdent
Corp) was applied and dried then one coat of Assure
Plus was applied on all surfaces and lightly dried with
air for 30 seconds. In group 2 samples were etched by
9.6% hydro uoric acid (ultra porcelain etch, ASA) for
4 min then rinsed for 30 seconds and dried. Then both
groups proceeded with application of composite resin
on bracket base and cured using a light curing unit.
BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS THE EFFECT OF ASSURE PLUS RESIN ON THE SHEAR BOND STRENGTH 83