Medical

Communication

Biosci. Biotech. Res. Comm. 10(2): 324-329 (2017)

Comparative studies on the enamel demineralization

of cemented orthodontic bands using four different

cements

Mehrnaz Moradinejad

, S. Hojjat Shakib

* and Zeinab Eftekhari

Assistant Professor, Department of Orthodontics, School of Dentistry, Ahvaz Jundishapur University of

Medical Science, Iran

Postgraduate Orthodontic Resident, School of Dentistry, Ahvaz Jundishapur University of Medical Science, Iran

ABSTRACT

This study assessed the demineralization depth of the buccal and lingual surfaces of the premolars cemented by zinc

phosphate, glass-ionomer, resin-modi ed glass-ionomer (RMGI) and resin cement to receive orthodontic bands in

vitro. In this in vitro experimental trial, 80 intact premolars were collected and after cleaning, they were randomly

assigned into 4 groups. Orthodontic bands were cemented to the teeth using zinc phosphate, glass-ionomer, resin-

modi ed glass-ionomer and resin cements. The teeth were stored in the arti cial saliva at 37 °C for 7 days to simulate

cement solubility in the oral cavity while they were kept in the acidic gelatin solution (gelatin 17%, 1g/L hydroxyapa-

tite, 0.1% thymol, pH=4.3) for in vitro caries stimulations. These procedures were repeated for 4 times (total 8 weeks).

After bands removal, the teeth were coated by a nail varnish and only 2 small windows (2×2 mm) in the buccal (which

was not under the band and with no contact with cement) and lingual surfaces (under the band with a contact with

cement) were exposed. The teeth were kept in 10% methylene blue for 24 hours and after being washed by deionized

water, they were sectioned buccolingually. The sections were examined by a microscope in 50x magni cation and

depth of methylene blue penetrations were calculated. The depths of the demineralization were analyzed by one-sided

analysis of variance (ANOVA) and post hot Tukey tests. The demineralization depth in the lingual surfaces using the

cements of zinc phosphate, glass-ionomer, resin modi ed glass- ionomer and resin cement were 17.85 (±11.59), 15.55

(±9.44), 8.55 (±8.04) and 11.8 (±8.88) microns respectively while the values were 26.95 (±6.72), 25.75 (±5.66), 24.35

(±6.77) and 22.65 (±8.19) for the buccal surfaces. Signi cant differences were found regarding the demineralization

depth in the lingual surfaces in different cements (p=0.02), however, the differences were not signi cant in the buccal

324

ARTICLE INFORMATION:

*Corresponding Author: s.ho.shakib@gmail.com

Received 1

April, 2017

Accepted after revision 29

June, 2017

BBRC Print ISSN: 0974-6455

Online ISSN: 2321-4007 CODEN: USA BBRCBA

Thomson Reuters ISI ESC and Crossref Indexed Journal

NAAS Journal Score 2017: 4.31 Cosmos IF : 4.006

reserved.

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

Moradinejad, Shakib and Eftekhari

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS COMPARATIVE STUDIES ON THE ENAMEL DEMINERALIZATION OF CEMENTED ORTHODONTIC BANDS 325

surfaces as a control group. In lingual surfaces, signi cant differences were observed between zinc phosphate and

resin-modi ed glass-ionomer which was higher for zinc phosphate cement (p=0.02). Resin-modi ed glass-ionomer

showed the best results to prevent enamel demineralization adjacent to the orthodontic bands.

KEY WORDS: DEMINERALIZATION, BANDS, RESIN MODIFIED GLASS-IONOMER, DYE PENETRATION

INTRODUCTION

Enamel demineralization and adhesive bond strength are

quite controversial in orthodontic treatments. Although

brackets are a certain part of  x orthodontic treatment,

more than 85% of the orthodontists use orthodontic

bands for molars. If the bond linking the band and tooth

fails, decalci cation of the tooth surface, unplanned and

long visits as well as unsuccessful treatment mechan-

ics will be inevitable (Millett 2003 and Craig 2006). To

increase the resistance against occlusal forces, a more

stable treatment is applied to use the bands. Hence, it

is essential to place an appropriate retention in bands

using a mechanical or chemical method. The cement

used not only does provide chemical retention, but also

it provides a mechanical retention by  lling the pores

(Kvam 1983, Mosby 2002 and Millett 2009 Kashani

etal., 2012 Prabhavathi 2015).

One of the foremost causes of band loosening or why

a band has a bond failure is the dissolution of cement in

oral cavity. Clinically speaking, the degree of band reten-

tion and the extent to which cements dissolve in oral

cavity are important since the bands with low retention

and cements of high dissolution can accumulate plaque

under the bands in a way that enamel decays within

three weeks. Therefore, using cements with low disso-

lution in oral cavity can increase the ef ciency of the

orthodontic mechanics and reduce caries and microleak-

age (Norris 1986, Johnson 2000, Millett 2003, Buchalla

2000, Hajmiragha 2008, Sabouhi Prabhavathi 2015).

Since 1878, zinc phosphate cement has been used

to cement orthodontic bands. It has a high compres-

sive strength, low tensile strength and it dissolves more

quickly adjacent to organic acids (Norris 1986, Johnson

2000, Millett 2003). When cemented orthodontic bands

are removed by zinc phosphate, in some cases decal-

ci cations are observed a great deal which can be due

to the cement loss between the bands and tooth and a

more favorable environment for bacterial activity, (Craig

2006, Buchalla 2000).In addition to the biocompatibil-

ity with enamel and dentin, glass-ionomer cement has

various cariostatic effects. Fluoride ion activity in these

cements can cause remineralization although their bond

strength is clinically limited (Pithon 2006 Prabhavathi

etal., 2015).

To try to release  uoride and to improve bond

strength, resin modi ed glass-ionomer cements were

introduced by Rix (2001). This cement requires moisture

because of its speci c chemical composition and it can

be used in moisture atmospheres as a suitable element to

be applied in areas where dry isolation cannot be used.

It is chemically bonded to enamel and dentin. Also, it

has a similar thermal expansion coef cient compat-

ible with tooth structure (Valente 2002). Resin cements

are composites with small  ller particles and low  ller

ensuring there is a thin  lm thickness. They are much

stronger than light-cure glass-ionomers but they cannot

expand as light-cure glass-ionomers do. Resin cements

can be micromechanically bonded to a prepared enamel,

dentin, alloy and ceramics. They are offered in different

dyes (O’Brien 2002).The current study aims at comparing

the incidences of enamel decalci cation of zinc phos-

phate, glass-ionomer, resin-modi ed glass-ionomer and

resin cement to receive orthodontic bands.

MATERIALS AND METHODS

In this experimental research 80 intact premolars which

had no cracks, fractures or restorations were collected

and were extracted during a 6-month period for ortho-

dontic treatments. To remove debris, a non- uoride

lotion (13% hypochlorite for 24 hours) was used. After

dis-infecting them either in a normal saline or deionized

water, they were kept in room temperature (Foley 2002).

The teeth were then divided up into 4 groups with 20 in

each. The groups were zinc phosphate cements (Hoff-

mann, Germany), RMGI (GC Fuji, Japan), glass-ionomers

cements (GC Fuji, Japan) and Resin Cements (GC Fuji,

Japan).

Around the collected teeth, stainless steel orthodontic

bands (DENTAURUM,Germany) were installed and were

tightly  xed to reduce enamel dissolution. In each band

and each group, cement was added in a way that its

maker asserted. Care was taken in each group to remove

additional cement from the edges of cervical and occlusal

bands before they were polymerized so as to they do not

affect the results. Afterwards, cements were remained

untouched for 2 minutes in 25° C to solidify. (bench set)

After sub-dividing, the teeth were kept in plastic con-

tainers and then using an acrylic resin, they were  lled

high up to normal bones. Only the crowns were exposed

and the bands were located a few millimeters higher

than acrylic resin. We put the teeth in plastic bags and

the following procedures were followed for 4 times (in

an 8-week period):

Moradinejad, Shakib and Eftekhari

326 COMPARATIVE STUDIES ON THE ENAMEL DEMINERALIZATION OF CEMENTED ORTHODONTIC BANDS BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

To simulate in vitro caries in oral cavity, the samples

were put in an incubator at 37° C in arti cial saliva for

7 days. Then, all the teeth were kept in an acidic gela-

tin solution (17% gelatin,1 g/L hydroxyapatite, 0.1 %

thymol, 4/3 pH) in an incubator at 37°C for 7 days (fol-

lowing the recommendations made by Silverstone etal,

1985) (17). They were kept in deionized water subject to

demineralization gel.

In the next stage, the teeth were taken out of the

acrylic and bands were removed from them. Hav-

ing removed the leftover cements, the teeth were then

cleaned. Following that, they were protected applying

nail-varnish. Only two small windows of the enamel

(2×2 mm) were exposed. One was beneath the covering

band in the lingual surface which was subject to cement

and the other outside the covering band in the buccal

surface with no touch with the cement. The second one

is considered as the control surface for all the molars. In

this case, the enamel which was directly connected to

the cement and also the enamel which was 2 millimeters

far from cement was tested.

The teeth were then put in a 10% methylene blue

at 37°C for 24 hours and were washed using deionized

water. In this stage, all of them were kept in plastic con-

tainers to be prepared for cutting and using epoxy res-

ins, we  lled them one millimeter down to the cusps.

The mounted teeth of the epoxy resins were buccolin-

gually cut by a diamond disc with cold water along the

line between the buccal and lingual windows. The cuts

which were 50 times magni ed by a stereomicroscope

were then analyzed. Finally, the depth of caries lesions

was examined in microns via measuring penetration

rate of methylene blue.

We then compared the demineralization depth meas-

ures of the caries lesions in different sub-groups through

the one-way analysis of variance. In the lingual surfaces

of molars, the ANOVA test results were signi cant so

having used Tukey comparisons; we compared them two

by two.

RESULTS AND DISCUSSION

The demineralization depth of the caries lesions in lin-

gual surfaces cemented by zinc phosphate, glass-iono-

mer, resin-modi ed glass-ionomers and resin cements

were 17.85 (± 11.59), 15.55 (±9.44), 8.55 (± 8.04) and

11.8 (± 8.88) microns. (Table 1)

The demineralization depth of the caries lesions in

buccal surfaces cemented by zinc phosphate, glass-iono-

mer, resin-modi ed glass-ionomers and resin cements

were 26.95 (± 6.72), 25.75 (±5.66), 24.35 (± 6.77) and

22.65 (± 8.19) microns. (Table 2)

The results of the one-way ANOVA revealed signi -

cant differences in demineralization depth of the caries

lesions in lingual surfaces. (p=0.02). On the other hand,

the post hot Tukey test aiming at comparing two by

two groups showed signi cant differences between zinc

phosphate cements and resin modi ed glass-ionomer

(p=0.02), but in other two-by-two comparisons no sig-

ni cant difference was seen. (Table 3).

In buccal surfaces (control group), there was no sig-

ni cant difference in terms of demineralization depth

Table 1. Distribution indices of demineralization depth (in microns) in lingual surface of teeth for various cements

Group Mean Standard

Deviation

Standard

Error

95% con dence

interval/Low range

95% con dence

interval/High range

Minimum Maximum

Zinc

Phosphate

17.85 11.59 2.59 12.43 23.27 0 46.0

Glass-ionomer 15.55 9.44 2.11 11.13 19.97 0 48.0

Resin-modi ed

glass ionomer

8.55 8.04 1.79 4.79 12.31 0 24.0

Resin cement 11.8 8.88 1.99 7.64 15.96 0 26.0

Table 2. Distribution indices of demineralization depth (in microns) in buccal surface of teeth for various cements

Group Mean Standard

Deviation

Standard

Error

95% con dence

interval/Low Range

95% con dence

interval/high range

Minimum Maximum

Zinc Phosphate 26.95 6.72 1.5 23.8 30.09 9.0 38.0

Glass-ionomer 25.75 5.66 1.26 23.1 28.39 16.0 37.0

Resin-modi ed

glass ionomer

24.35 6.77 1.51 21.18 27.52 15.0 44.0

Resin cement 22.65 8.19 1.83 18.82 26.48 0 40.0

Moradinejad, Shakib and Eftekhari

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS COMPARATIVE STUDIES ON THE ENAMEL DEMINERALIZATION OF CEMENTED ORTHODONTIC BANDS 327

values of caries lesions in using various cements (one-

way ANOVA: p=0.24). As there was no signi cant dif-

ference in any of the comparisons, we did not compare

the results of the demineralization depth two by two.

Obviously, under these circumstances no signi cant dif-

ferences will be available among cement groups in terms

of demineralization depth values.

On the other hand, the demineralization depth aver-

age of caries lesions (Standard deviation ±) in all cements

was analyzed and it was 13.44 microns ±) 10.05) for

lingual surface of the teeth; whereas in buccal surface

it was 24.93 microns (±6.95) According to the results

driven from Student t test, signi cant differences were

observed in buccal and lingual surfaces of the molars

and in lingual surface it was signi cantly lower than

buccal surface. (p=0.0001)

What makes teeth capable for decalci cation and

caries when orthodontic bands are applied is that these

bands and their connections provide a suitable place

for plaque accumulation. It was discovered that 85% of

cervical and occlusal margins of orthodontic bands are

exposed to caries lesions (Radlanski 2003). Therefore,

using cements which can release  uoride can be effective

in preventing enamel decalci cation. As the  ndings of

this study indicate, signi cant differences were observed

in lingual surfaces in terms of demineralization depth

of the caries lesions when zinc phosphate cements and

resin modi ed glass ionomer were used (17.85 and 8.55

microns respectively). In addition, resin modi ed glass

ionomer had the most preventive effects of deminerali-

zation. The least capability of preventing demineraliza-

tion of caries lesions was for zinc phosphate and glass

ionomer cements and resin cements respectively. (15.55,

11.8 microns for glass ionomer and resin cements).

In buccal surfaces, which were the control group for

all the teeth, there was not any signi cant difference

in demineralization depth of the arti cial caries lesions

in zinc phosphate, glass ionomer, resin modi ed glass

ionomer and resin cements. Nevertheless, the lowest

demineralization depth with an average 22.65 microns

was observed for resin cements whereas resin modi ed

glass ionomers, glass ionomer and zinc phosphate fol-

lowed in ranking respectively, (demineralization depth

values: 24.35, 25.75 and 26.95 microns). The variations

in demineralization depth in different groups together

with high amount of released  uoride from resin modi-

 ed glass ionomer cements can be indicative of suitable

bond strength, high tensile strength and low solubility

(Foley 2002, Silverstone 1985, Radlanski 2003).

In this study, the highest values of demineralization

depth were observed around the cemented orthodontic

bands which used zinc phosphate. This can be due to

the fact that zinc phosphate cement did not contain any

 uoride and as a result it provided no excessive protec-

tion of enamel against acidic attacks of in vitro bacteria.

On the other hand, the dissolution of zinc phosphate

cement in in vitro cavity can make the teeth vulnerable

to caries (Foley 2002).

Also, resin cements have had comparatively more

suitable preventive effects of caries around orthodon-

tic bands than glass ionomer cements. Pressure strength

and higher tensile strength as well as low solubility and

micromechanical bond to the teeth are among the ben-

e ts of resin cements compared to glass ionomers. Resin

cements are recommended to be used under certain

conditions in which RMGIs cannot cause any retention

(Weiner 2008).

In 2015 in India, Prabhavathi etal. carried out an in

vitro experiment and analyzed demineralization values

of orthodontic cements (zinc phosphate, glass ionomer

and resin modi ed glass ionomer cement); and having

used acidic gelatin solution, they then stimulated acidic

cariogenic conditions and cut the teeth to measure car-

ies lesions by an electron microscope (Prabhavathi etal.,

2015). In this research, zinc phosphate cement had the

highest demineralization value while the value for glass

ionomer was the lowest. These results correspond with

the  ndings obtained from our study about zinc phos-

phate; nevertheless, RMGI cement of the current study

had the minimum demineralization depth and that was

different from the recent study.

In an in vitro study conducted in 2014 in India,

Hedge etal. (2014) used a similar research protocol and

they found out RMGI had the minimum demineraliza-

Table 3. The results of various comparisons of cement groups in terms of demineralization

depth in lingual surfaces of teeth. (Tukey test)

First Group Second Group Average differences P value

Zinc Phosphate Glass ionomer Resin modi ed

glass ionomer Resin cement

2.3

9.3

6.05

0.87

0.02

Signi cant

0.19

Glass-ionomer Resin modi ed glass ionomer

Resin cement

7.0

3.75

0.11

0.61

Resin modi ed glass ionomer Resin cement 3.25 0. 71

Moradinejad, Shakib and Eftekhari

328 COMPARATIVE STUDIES ON THE ENAMEL DEMINERALIZATION OF CEMENTED ORTHODONTIC BANDS BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

tion whereas zinc phosphate had the highest enamel

demineralization in banded teeth (Hegde 2014). It can be

concluded that the  ndings taken from this study cor-

respond with the current research. In 2012, in another

study in India, Goje et al. investigated the strength

against enamel demineralization after banding 4 ortho-

dontic cements in in vitro conditions and they suggested

that banded teeth which were cemented by glass ionomer

and RMGI had the lowest values followed by zinc poly

carboxylate and zinc phosphate (Goje etal. 2012). Same

 ndings could be observed from the current research.

Kashani etal., in 2012, investigated the enamel deminer-

alization depth of adjacent cemented orthodontic bands

using zinc polycarboxylate, glass ionomer and RMGI in

Iran. In their  ndings, the highest depth was for zinc

polycarboxylate; and the best result of preventing caries

in orthodontic bands was for RMGI (Kashani 2012).

The results taken from the recent study have been

reported in the current research in which RMGI was a

more suitable cement to prevent caries lesions. In another

research carried out in Canada in 2002, Foley etal. also

found out that zinc phosphate had more dye penetration

compared to zinc poly carboxylate cements and RMGI.

They also reported that RMGI is the best for long-term

orthodontic treatment (Foley 2002).As resin modi ed

glass ionomer possesses speci c features, researchers

consider it as a more suitable cement to prevent caries

lesions around and beneath orthodontic bands. There-

fore, considering the results of the observations (Foley

2002, Weiner 2008). We can conclude that resin modi-

 ed glass ionomer could be used as an intermediary for

orthodontic banding purposes. However, it is important

to consider all the consequences of this replacement

including clinical inspections.

It is proven that in the  rst three days of cement-

ing much more  uoride is released from orthodontic

cements. However, after three weeks  uoride release

decline considerably (Ogaard 1989). Having said that, it

is essential to conduct long term evaluations of demin-

eralization depth of caries lesions after applying ortho-

dontic cements.The lesions of enamel caries which are

arti cially created have all the histologic characteristics

of natural caries and they are successfully applied in in

vitro enamel demineralization researches (Casals 2007).

Moreover, stimulated enamel caries lesions are prepared

in a more homogenous way. As a result, a much more

reliable laboratory model is provided to survey deminer-

alization and remineralization depth values. Under these

condition the area in enamel in which carries form and

has a  xed depth in subsurface, can be used to evalu-

ate remineralization (Queiroz 2008). Generalizing lab

research results to oral cavity has its own limitations.

First of all, in oral cavity variables such as  uoride

weakening by saliva play an important role and hence

gaining access to various  uoride products and clean-

ing them cannot be stimulated in experimental lab stud-

ies (Damato 1990). Moreover, in oral cavity conditions,

there are variables related to host such as the mineral

concentrations of tooth and pellicle or the conditions

in which plaque can be formed that can affect demin-

eralization value. The factors related to saliva includ-

ing salivary  ow rate, its composition and buffering

capacity can have protective effects in tooth surfaces

(Marsh 1999). Increasing the remineralization capability

of saliva is also clinically important. As saliva is widely

found in oral cavity, the demineralization rate is de -

nitely lower than lab conditions; so more evaluations

are recommended in clinical environments and in situ.

CONCLUSION

It can be concluded that using resin modi ed glass iono-

mer has had the best results in preventing enamel dem-

ineralization under orthodontic bands.

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