Medical

Communication

Biosci. Biotech. Res. Comm. 10(2): 82-87 (2017)

The effect of assure plus resin on the shear bond

strength of metal brackets bonded to enamel and

surface of porcelain and amalgam restorations

Mohammad Hossein Toodehzaeim

, Alireza Haerian

, Isa Safari

and Rahele Arjmandi

Associate Professor, Department of Orthodontics, School of Dentistry, Shahid Sadoughi University of

Medical Sciences, Yazd, Iran

Assistant Professor, Department of Orthodontics, School of Dentistry, Shahid Sadoughi University of Medical

Sciences, Yazd, Iran

Post Graduate Student, Department of Orthodontics, School of Dentistry, Shahid Sadoughi University of

Medical Sciences, Yazd, Iran

ABSTRACT

This study evaluated the shear bond strength (SBS) of metal brackets bonded to amalgam and porcelain using the

conventional and Assure plus methods. 60 human maxillary premolar teeth used in this study. Group1 contained 12 samples;

groups 2 and 3 groups contained 24 samples. In Group 1, the specimens were after acid etching, Assure plus and light Bond adhe-

sive were applied to enamel surfaces. In group 2 a cavity was prepared in the buccal surface of teeth and sandblasted, then divided

to 2 subgroups. In subgroup1, the brackets were bonded with assure plus and light bond. In subgroup 2 were used conventional

method (metal primer and light bond adhesive). In group 3, 24 glazed metal-ceramic crowns were fabricated for maxillary premo-

lar teeth. The samples were sandblasted and randomly divided in to 2 subgroups. In subgroup 1 one coat of porcelain conditioner

was applied then Assure plus and light Bond adhesive were applied. Samples were etched by 9.6% hydro uoric acid and bonded

with light bond In subgroup 1. SBS was evaluated by a Universal testing machine. Statistical analysis was conducted by analysis

of variance (ANOVA) and Tukey tests. Group 1(enamel surface) showed a signi cantly higher value compare to other groups (14.52

MPa) (P<.05). There were no signi cant difference in SBS value between subgroups of amalgam and porcelain (7.70, 7.97 and

8.85, 8.54 MPa, respectively) (P>.05). Bracket bonding to amalgam and porcelain with assure plus resin produced suitable bond

strengths. Although they produced the lower bond strength compared with enamel surface.

KEY WORDS: ASSURE PLUS; SHEAR STRENGTH; ORTHODONTIC BRACKETS

ARTICLE INFORMATION:

*Corresponding Author: rahelearjomandi@yahoo.com

Received 27

Feb, 2017

Accepted after revision 12

May, 2017

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Online Contents Available at: http//www.bbrc.in/

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

Mohammad Hossein Toodehzaeim et al.

FIGURE 1. Testing machine with a specimen

inplace from frontal view.

Following the bonding of brackets, the specimens were

stored in separate glasses in distilled water for 7 days

prior to the shearing bonding test.

Shear bond strength (SBS) were measured using

a Dartec HC10 universal testing machine (Zwick Ltd,

Here_fordshire, UK) by application of 50 kgf of force

at .5 mm/min. the force was exerted to the bonding site

while the bracket base was parallel to the direction of

force. Shearing bond strength was measured in Newton,

which was converted in to Mpa by dividing the shear

bond force (Newton) by the bracket base area (mm

STATISTICAL ANALYSIS

Descriptive statistics including the mean and standard

deviation (SD) of SBS values were analyzed using the

SPSS16. The ANOVA and Tukey

post hoc test were used

to compare SBS of between the groups.

RESULTS

Table 1 shows the results of mean, standard deviation

and range of shear bond strength for the  ve groups.

The highest SBS (19.46 MPa) was observed in group 1

(enamel surface) and the lowest (5.29 MPa) was observed

in group 2 (amalgam+RMP). Table 2 shows Comparison

of the Mean Shear Bond Strength in the Study Groups.

There were no signi cant difference in SBS value

between subgroups of amalgam and porcelain (7.70,

7.97 and 8.85, 8.54 MPa, respectively) (P>.05), but group

1 (14.52 MPa) showed a signi cantly higher value com-

pare to others (P<.05)

DISCUSSION

Bonding orthodontic attachments to the restoration sur-

face is always challenging because of the high rate of bond

failure during orthodontic treatment. Many researchers

Table 1. Descriptive Statistics of Shear Bond Strength (MPa) in Five Groups

Range S D Mean(MPa) Study group

12.23-19.46 1.9431 14.5225 Enamel (Assure plus)

5.80-12.64 1.7359 7.7030Amalgam (Assure plus)

5.29-11.62 2.2034 7.9733 Amalgam (RMP)

5.38-11.14 1.6559 8.8575 Porcelain (Assure plus)

5.85-10.83 1.7665 8.5475 Porcelain (HF)

Table 2. Two by Two Comparison of the Mean Shear Bond Strength in the Study Groups

Signi cance Mean difference Study group

.000 6.8191 1(enamel), 2(amalgam+Assur plus)

.000 6.5491 1(enamel), 2(amalgam+RMP)

.000 5.6650 1(enamel),3(porcelain+Assur plus)

.000 5.9750 1(enamel),3(porcelain+HF)

.997 .2700 2(amalgam+Assur plus), 2(amalgam+RMP)

.560 1.1541 2(amalgam+Assur plus), 3(porcelain+ Assur plus)

.803 .8441 2(amalgam+Assur plus), 3(porcelain+HF)

.775 .8841 2(amalgam+RMP), 3(porcelain+ Assur plus)

.943 .5741 2(amalgam+RMP), 3(porcelain+HF)

.994 .3100 3(porcelain+ Assur plus), 3(porcelain+HF)

84 THE EFFECT OF ASSURE PLUS RESIN ON THE SHEAR BOND STRENGTH BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

Mohammad Hossein Toodehzaeim et al.

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS THE EFFECT OF ASSURE PLUS RESIN ON THE SHEAR BOND STRENGTH 85

have suggested modi ed bonding procedures. Bonding

to amalgam restoration carried out by sandblasting with

50μm aluminum oxide before bonding (6, 7, 10, 11) and

use of RMP (Reliance metal primer) in order to achieve

chemical bonding (7). Sandblasting and HF is used for

treating the porcelain surface (4, 12-15). Suggested sur-

face preparation methods can be harmful to soft tissues

or time consuming (12, 16). In recent years, different

alternative methods to achieve adequate surface treat-

ment have been proposed (4, 15). We used Assure plus

resin for bonding to enamel, amalgam and porcelain

surface and compared them with RMP and HF prepara-

tion in amalgam and porcelain restorations respectively.

The group1 (enamel group) demonstrates signi cantly

higher bond strength (14.52MPa) when compared with

other groups. the mean value achieved in our study was

comparable to that reported in other studies, that used

transband XT primer as the gold standard for bracket

bonding on enamel (bond strength ranging from 10.4

MPa to 20 MPa)(17-19). Hellak A et al evaluated Enamel

shear bond strength of two orthodontic self-etching

bonding systems (Prompt L-Pop and Scotchbond) com-

pared to Transbond XT that results showed All three

adhesives revealed similar bond strengths (15.49 ± 3.28

MPa ,13.89 ± 4.95 MPa, 14.35 ± 3.56 MPa respectively)

and was comparable with our study (14.52 Mpa) (20).

Our study found no signi cant difference between

the bond strength of amalgam subgroups (7.75 MPa and

7.97 MPa in amalgam+Assure plus and amalgam+RMP

respectively). This  nding was comparable with the

study of Germic D et al(1) that the brackets were bonded

with Unite (3M Unitek) using Reliance metal primer

(7.15 MPa) although their result showed less shear bond

strength. This lower amount is likely due to the ther-

mocycling process in Germic D

study. That decreases

the bond strength between resin composite and amal-

gam(21). Although some studies showed that the thermo-

cycling process minimally affected the bond strength of

composite resin to amalgam surface (6, 7). According to

Zachrisson BU et al (10) the mean tensile bond strength

to sandblasted amalgam surface was 3.4 Mpa to 6.4 Mpa

that showed lower mean strength compared with our

study. This is likely due to using a different intermedi-

ate resin (All bond2). Buyukyilmaz T (7) showed using

4_META primer (amalgam bond_plus, metal primer) cre-

ated signi cantly more effective bond strength to differ-

ent amalgam surfaces (Lathe-cut, admixed, and spheri-

cal amalgams) compared to All_Bond 2 primer, whereas

the control group of the study (bonded with Concise

to extracted mandibular incisor teeth) was comparable

with our study (13.2 Mpa). So in vitro, bonding to amal-

gam showed signi cantly lower strength than extracted

teeth (10).

Also there was no signi cant difference between sub-

groups of porcelain (8.85 MPa and 8.54 MPa in porcelain

+Assure plus and porcelain + HF respectively). Com-

parison of different studies in this  eld represents some

variations. Yadav S et(22) al and Hosseini MH(23) et al

used hydro uoric acid 9.5% and 9.6% respectively for

etching porcelain surface. The mean shear bond strength

Table 3. Box of 95 % con dence interval measurements and mean value of shear bond

strength in  ve group

Group 1: Enamel (Assure plus),

Group 2: Amalgam (Assure plus),

Group 3: Amalgam (RMP),

Group 4: Porcelain (Assure plus),

Group 5: Porcelain (HF)

Mohammad Hossein Toodehzaeim et al.

86 THE EFFECT OF ASSURE PLUS RESIN ON THE SHEAR BOND STRENGTH BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

was 9.9 MPa and 9.4 MPa respectively in that study.

Whereas Fan CH study(24) showed lower bond strength

(7.055 MPa) compared with our study, which likely was

the result of different methods or adhesives used. We

could was  nd no comparable study with our research

related to Assure plus resin bonding in improving adhe-

sion to amalgam and porcelain surface. According to

Reynolds

’

study (25) an affective clinical orthodontic

bonding requires a minimum bond strength of 6_8 MPa.

The  ndings of the present study show that enamel, por-

celain and amalgam treated with Assure plus can yield

bond strength values within the suitable clinical range.

It appears that using Assure plus as a multipurpose

resin not only produces suitable bond strengths but is

also a less time_ consuming, simple and safer method

compared with conventional methods because of more

time_ consuming process is needed for rinsing and dry-

ing when working with HFA (4min) and possible cause

to soft tissue burn if do not care completely also treat-

ing amalgam surface with Assur plus, do not require for

application of metal primer.

CONCLUSION

Considering the results of this study, we conclude the

following: (1) the group1 (enamel group) demonstrate

signi cantly higher bond strength compared with amal-

gam and porcelain groups. (2) There were no signi cant

difference in SBS value between subgroups of amalgam

and porcelain. (3) This study recommends using Assure

plus as multipurpose resin for bonding to enamel, amal-

gam and porcelain surface.

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