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Keywords:

  • Adherence;
  • bacteria;
  • band cement;
  • radiolabel;
  • Streptococcus mutans

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

Background:  The aim of this study was to quantitatively determine the adherence of Streptococcus mutans to orthodontic band cements.

Methods:  Two hundred and ten blocks of seven different band cements for orthodontic prescription were made using a Teflon mould (4 × 4 × 1 mm). The obtained blocks were slightly polished and cleansed ultrasonically. Certified S. mutans ATCC 25175 were cultured with conventional methods for growth in Petri dishes and trypticase soy broth. Quantitative analysis was carried out with radioactive markers to codify the bacteria (3H). Subsequently, a combustion system was used to capture the residues, the radioactivity of the samples was measured, and the values recorded in disintegrations per minute (dpm). One-way analysis of variance (ANOVA) with a Scheffé test for multiple comparisons was realized with a significance level of ≤0.05.

Results:  Significant differences were found among different band cement materials (p < 0.001). Two band cement materials showed statistically lower values than the others (Transbond Plus Band Cem and Ketac Cem). In contrast, GC Fuji Ortho Band presented the highest adherence of S. mutans.

Conclusions:  Among the cements evaluated, Transbond Plus Band Cem and Ketac Cem showed lower adherence of S. mutans.


Abbreviations and acronyms:
ANOVA

analysis of variance

dpm

disintegration per minute

SEM

scanning electron microscope

Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

The oral cavity environment provides certain essential characteristics for the proliferation of bacteria that are capable of producing acids that demineralize the surface of the tooth enamel.1 Dentobacterial plaque has a crucial role in the adhesion of these microorganisms to the dental surface in such a way that the demineralization of the enamel originates with the organic acid production of microorganisms. Streptococcus mutans has been classified as the most cariogenic bacteria.1,2

Orthodontic treatment using fixed appliances (brackets, bands, archwires, ties) provides suitable conditions to facilitate the colonization of cariogenic microorganisms. As the fixed appliances facilitate the retention and adhesion of dentobacterial plaque, dental hygiene becomes more complicated and microorganisms increase the risk of enamel demineralization. Orthodontic bands are usually placed on the teeth for 2 years on average, and the proliferation of microorganisms, as well as the risk of enamel damage at the enamel-cement interface, increases. Demineralization of the enamel can occur from the first month after placement of fixed appliances.3 It has been estimated that the prevalence of white spot lesions in patients treated orthodontically is from 12.6% to 50%.4

The prevention of white spot lesions/caries and periodontal problems during orthodontic treatment is a significant challenge to the clinician and patient. Many strategies have been proposed and developed to minimize these biological consequences, which may include fluoride varnishes, tooth mousse and various toothpastes and mouthrinses. Moreover, new materials have been developed which are relatively insoluble (unlike the historical copper and zinc phosphate cements) and even include antibacterial and fluoride releasing characteristics.

Although the direct bonding of appliances is performed in the majority of teeth, cementation of orthodontic bands in molars is an essential procedure for clinical treatment in most common cases. The properties of the cements are different due to their structure and chemical composition. Recently developed materials present a great diversity between their physical properties, chemical composition, as well as the ultrastructure.5,6 These properties can cause positive or perhaps negative effects in bacterial aggregation, and the most undesirable effect during the orthodontic treatment is the appearance of incipient white spot lesions. Currently, different kinds of materials are available for cementing bands. However, the glass ionomer cement is the most commonly used, followed by hybrid materials such as glass ionomer modified with composite resin.

In this context, it is important to analyse the amount of bacterial accumulation in different cement materials used in orthodontics. Thus, the aim of this study was to quantitatively determine the adherence of S. mutans to orthodontic band cements.

Materials and methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

The following orthodontic cements were classified into seven groups: (1) Transbond Plus Band Cem (3M Unitek, Monrovia, CA, USA); (2) Ketac Cem (3M ESPE, Gmbh, Seefeld Oberbay, Germany); (3) Ortholy Band Paste (Fuji GC Corp, Tokyo, Japan); (4) GC Fuji Ortho Band (GC Corporation, Tokyo, Japan); (5) Multi-Cure Band (3M Unitek); (6) CX (Shofu, Kyoto, Japan); and (7) Optiband Ultra (Ormco, Glendora, CA, USA). The types of cements used are described in Table 1. The total sample size was 210 blocks (30 per group). The cement blocks were made using a Teflon mould of 4 × 4 × 1 mm. For the light curing materials (Groups 1, 4, 5 and 7), the procedure was performed covering the material with a micro-slide glass, followed by the application of the light curing lamp (Ortholux, 3M Unitek) with an intensity of 1600 mW/cm² for 60 seconds. The self-curing materials were handled according to the manufacturer’s instructions.

Table 1.   Tested materials
Trade nameCement typeCuring mechanism
1. Transbond Plus Band CemCompomerPhotopolymerization (light cure)
2. Ketac CemConventional glass ionomerChemical cure (acid-base reaction)
3. Ortholy Band PasteResin-modified glass ionomerPhotopolymerization (light cure)
4. Fuji Ortho BandResin-modified glass ionomerChemical cure (acid-base reaction)
5. Multi-Cure BandResin-modified glass ionomerTri-cure (acid-base reaction, light cure and self cure)
6. CXConventional glass ionomerChemical cure (acid-base reaction)
7. Optiband UltraResin-modified glass ionomerPhotopolymerization (light cure)

The obtained blocks were slightly polished with sand paper and diamond pastes of 6 μm (MetaDi II Diamond Paste, Buehler, Lake Bluff, IL, USA) and were cleaned ultrasonically for a minute to eliminate impurities. The samples were dried and stored in a humidity-free environment to avoid contamination. All the specimens were sterilized in ethylene oxide gas.

Certified S. mutans ATCC 25175 were cultured with conventional methods in Petri dishes and trypticase soy broth (BBL, Cockeysville, MD, USA).7 Subsequently, S. mutans were transferred to a liquid culture medium.

Quantitative analysis of the adhesion of the microorganisms to the surface of the materials was performed with radioactive markers to codify the bacteria (3H). The specific activity of the radioactivity was approximately 30 000 dpm per 108 cells.

Each cement block was suspended in labelled bacterial fluid at 37 °C for 2 hours. To eliminate the non-adhering bacteria, the cement blocks were removed from the test tubes and immediately washed thrice with PBS. Labelled bacteria that adhered to the cement blocks were collected using an automatic sample combustion equipment (ACS-113, Aloka, Tokyo, Japan). Tritium was recovered as H2O in Aquasol-2 (Packard) and radioactivity was measured using a liquid scintillation counter (LSC-900, Aloka).7–9 The results were recorded in disintegration per minute (dpm).

In addition, some representative samples were observed under a scanning electron microscope (SEM) at 2500× magnification for qualitative analysis, after submerging the specimens for 2 hours at 37 °C in a solution containing the cultured microorganisms which was continually stirred. For the SEM observation, the samples were chemically prefixed with glutaraldehyde and fixed with osmium tetroxide, dehydrated with an ascending series of ethanol and freeze-dried. The samples were coated with a thin layer of osmium.10

Statistical analysis

The data were registered and examined with software for statistic analyses (SPSS 18, International Business Machines Corp, New York, USA). Differences in the measured values among the band cements were tested by one-way analysis of variance (ANOVA) with a Scheffé test for multiple comparisons. A probability of less than 0.05 for similarity of distribution was considered to be statistically significant.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

The mean values of the quantitative radiolabelled S. mutans, expressed in dpm, and the Scheffèpost hoc test to determine the statistically significant differences (p < 0.001) are summarized in Table 2. Moreover, the distribution frequency and percentage of each band cement material is illustrated in Fig. 1.

Table 2.   Quantitative adherence of radiolabelled S. mutans to orthodontic band cements (values expressed in dpm)
Band cement groupsMean (dpm)SDScheffè test*
  1. *Groups with different letters vary significantly from each other.

G 1. Transbond Plus Band Cem1261.01202.85A
G 2. Ketac Cem1264.64197.22A
G 3. Ortholy Band Paste1394.58249.28A, B
G 4. Fuji Ortho Band1902.1257.91C
G 5. Multi-Cure Band1551.62284.54B
G 6. CX1492.49325.59A, B
G 7. Optiband Ultra1615.82376.79B
image

Figure 1.  Distribution frequency of quantitative S. mutans adherence.

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According to the dpm values, band cements with less adhesion of S. mutans were Transbond Plus Band Cem (1261.01 dpm) and Ketac Cem (1264.64 dpm), followed by Ortholy Band Paste (1394.58 dpm), CX (1492.10 dpm), Multi-Cure Band (1551.62 dpm) and Optiband Ultra (1615.82 dpm). However, the values of Transbond Plus Band Cem and Ketac Cem were significantly lower than Multi-Cure Band, Optiban Ultra and GC Fuji Ortho Band. Although the values yielded by Ortholy Band Paste and CX were higher than Transbond Plus Band Cem and Ketac Cem, they were not significant.

In contrast, the band cement material with the highest quantity of S. mutans adhered was GC Fuji Ortho Band (1902.67 dpm; this value was significantly higher than all groups).

The representative SEM images of the cement materials obtained after 2 hours of immersion in S. mutans solution are shown in Fig. 2. The results obtained in the quantitative analysis are consistent with the qualitative observation with SEM.

image

Figure 2.  SEM images of the orthodontic band cements immersed in a solution of S. mutans for 2 hours at 2500× magnification. (a) = Transbond Plus Band Cem; (b) = Ketac Cem; (c) = Ortholy Band Paste; (d) = GC Fuji Ortho Band; (e) = Multi-Cure Band; (f) = CX; and (g) = Optiband Ultra.

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Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

Bacterial adherence to composite resins has been analysed and measured. However, to the best of our knowledge, the adherence of S. mutans to orthodontic band cement materials has not been quantified. Orthodontic bands surround the molars and the accumulation of dental plaque is higher than other teeth. The enamel-cement interface is a vulnerable area to develop white spot lesions and enamel demineralization. In this context, the application of cement with lower adherence of these cariogenic bacteria might be beneficial to prevent or reduce the undesirable formation of white spot lesions. Enamel demineralization is principally a S. mutans–associated disease. Therefore, it is important to evaluate the interaction of orthodontic cements with these bacteria. Previous studies have been conducted with the same type of strain obtaining reliable conclusions.2,7

In this study, the quantification of S. mutans involved 3H (a radioactive marker) measured with a combustion system from which residue radioactivity as dpm is determined. This methodology has been widely employed and reported since 1970.7–9 The 2 hours of culture time followed the methodology described by Saku et al.7

In the present study, the two band cement materials that demonstrated lower adherence of S. mutans were Transbond Plus Band Cem and Ketac Cem. However, the relative contribution of cement to biofilm formation is uncertain and probably quite variable but the amount of cement exposed to the oral cavity should be quite minimal (unless the band is poorly fitted).

Transbond Plus Band Cem is a blue coloured, light cured compomer band cement in a single syringe commercial presentation that makes it easy to handle and differentiate from the tooth. It is convenient to use because it does not require mixing and is ready to be placed directly onto the orthodontic band, and as it is light cured the clinician can determine the best time for polymerization. On the other hand, Ketac Cem is a conventional white coloured glass ionomer cement in a commercial presentation of liquid and powder which must be mixed and has an established curing time of 3 minutes.

Gillgrass et al.11 evaluated band failure with different band cement materials and showed that the band failure rate of 2.8% for the conventional glass ionomer (Ketac Cem), is lower than the 5% band failure rate for the modified composite. Therefore, this conventional glass ionomer cement provides suitable properties to place orthodontic bands, yielding higher mechanical retention and lower adherence of S. mutans. Moreover, it has been shown that discs of Ketac Cem release a higher level of fluoride in vitro and have a greater antimicrobial effect. Furthermore, it has also been shown that conventional glass ionomers, resin modified glass ionomers and modified composites have the capacity for fluoride uptake in vitro.12–15

Microgap formation between the adhesive material and the enamel surface contributes to microleakage, permitting the passage of bacteria and oral fluids, which can cause white spot lesions or demineralization under the attachment surface area.16 Orthodontic applications usually involve thin layers of adhesives and lack areas of bulk material that would seem to favour chemical cure systems. However, orthodontic bands are susceptible to areas of variable cement thickness and have a physically greater barrier to irradiation than brackets.17

Ulysal et al.18 reported that different band cement materials showed significant microleakage results: Ketac Cem had the highest leakage scores between the cement-band (median, 3.50 mm) and cement-enamel (median, 2.88 mm) interfaces followed by Transbond Plus, with a microleakage in cement-band (median, 0.38 mm) and cement-enamel (median, 0.38 mm) interfaces and Multi-Cure cement-band (median, 0.25 mm) and cement-enamel (median, 0.38 mm) interfaces.

In this study, GC Fuji Ortho Band showed the highest bacterial adherence among all the cements evaluated. A possible explanation could be that this material has a different surface texture and some irregularities that can cause retention of microorganism, making it more susceptible to colonization (Fig. 2D).

Although GC Fuji Ortho Band and Ortholy Band Paste exhibit similar presentation and components, the mixing procedure is different (Ortholy Band Paste has an automixing cannula system), and the results of S. mutans adherence are significant. On the other hand, Cacciafesta et al.19 showed that GC Fuji Ortho Band released more fluoride than the remaining molar banding adhesives evaluated. Moreover, Multi-Cure Band was found to release more fluoride than Transbond Plus and Optiband. The highest fluoride release rate of GC Fuji Ortho Band could be due to some components, such as barium fluoride, in the inorganic phase of the adhesive.19 Perhaps fluoride release of GC Fuji Ortho Band is not sufficient to avoid adhesion of S. mutans to the material.

Fluoride released from the conventional glass ionomer and the resin modified glass ionomer is believed to contribute to antibacterial activity.20 The availability of the fluoride and its release into the immediate microenvironment in vivo are not well defined in most novel fluoride containing dental materials, including orthodontic cements. The fluoride concentration in a specific dental material’s composition does not reflect its rate of release. Thus, the antibacterial properties due to fluoride concentration are expected to vary from one material to another.21

A material’s ability to be recharged with fluoride or other antibacterial components might extend antibacterial activity for the duration of the orthodontic treatment, thus providing a superior preventive measure to orthodontic treatment.21 As some fluoride releasing cements presented higher adherence of S. mutans, further studies should be carried out to identify the bacteriostatic effects of the cements with the property to release fluoride against the adherence of S. mutans.

In this study, we evaluated the quantity of S. mutans adhered to different cements commonly used in orthodontics, as the application of a material with lower accumulation of this cariogenic microorganism might be beneficial. However, the white spot lesion is a multifactorial process found in patients treated with orthodontics due to oral ecologic changes, such as a low pH environment, increased retentive sites for S. mutans and increased retention of food particles, which may lead to increased numbers of bacteria.22–27 Additionally, oral hygiene methods must be emphasized, together with the auxiliaries mouthwashes, sprays or varnishes. Caution should be taken with the orthodontic material we choose so as to prevent these undesirable effects. In this connection, Nelson-Filho et al.28 reported the efficacy of the use of a mouthwash with 0.12% of chlorhexidine gluconate to significantly decrease the levels of S. mutans and we considered that this would be an alternative to control these levels and reduce the white spot lesions.28

Other important factors are the acid production potential, the solubility of the material, the distribution and volume of residual material, and the comparison between bonding agents. Therefore, further studies should be carried out to identify bacterial adhesion with different variables and to compare it with these results.

Conclusions

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

Among the cements evaluated in the present study, Transbond Plus Band Cem and Ketac Cem showed lower adherence of S. mutans. In this context, the application of a band cement material with lower adherence of these cariogenic bacteria might be beneficial to prevent or reduce the undesirable formation of white spot lesions.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

The authors thank the Asahi University for providing all the facilities for making this research possible and the Mexican Council of Science and Technology (CONACYT) for the support.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References