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Table of Contents   
ORIGINAL RESEARCH  
Year : 2011  |  Volume : 22  |  Issue : 1  |  Page : 44-49
Evaluation of demineralization adjacent to orthodontic bracket and bond strength using fluoride-releasing and conventional bonding agents


Department of Orthodontics and Dentofacial Orthopedics, KLES's Institute of Dental Sciences, Belgaum, India

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Date of Submission03-Oct-2009
Date of Decision26-Mar-2010
Date of Acceptance21-Apr-2010
Date of Web Publication25-Apr-2011
 

   Abstract 

Background and Objectives: One of the most difficult problems encountered in orthodontic treatment with fixed appliance is the control of enamel demineralization around the brackets. Fluoride-releasing bonding adhesives were introduced to aid in the prevention of demineralization adjacent to orthodontic brackets. Hence, an in vitro study was conducted to evaluate and compare demineralization adjacent to the orthodontic bracket and the bond strength using fluoride-releasing adhesive and conventional adhesive.
Materials and Methods: One hundred and twenty healthy extracted premolars were selected for the study and were divided into two groups, each group consisting of 60 teeth. Both groups were further divided into three subgroups consisting of 20 samples each. Samples of subgroups A and B were bonded with two prototypes of fluoride-releasing adhesives (i.e. Rely-a-bond and Tru-bond). Samples of subgroup C (ortho-one) were bonded with conventional non-fluoride-releasing adhesive. Group I samples were subjected to demineralization in an acidic medium (methyl cellulose buffered with acetic acid at a pH of 4.5) for 4 weeks, which were later observed under a stereomicroscope. Group II samples were tested for shear bond strength using the Instron Universal testing machine.
Results: Both fluoride-releasing adhesives showed statistically significant lower enamel demineralization around the bracket when compared with the conventional adhesive. There was no statistically significant difference on comparing the demineralization between the two prototypes of fluoride-releasing adhesive. Evaluation of shear bond strength revealed that there was no significant difference between the subgroups.
Conclusion: Fluoride-releasing adhesives might aid in the prevention of demineralization adjacent to the orthodontic bracket with acceptable bond strength.

Keywords: Demineralization, fluoride-releasing adhesive, shear bond strength

How to cite this article:
Lodaya SD, Keluskar K M, Naik V. Evaluation of demineralization adjacent to orthodontic bracket and bond strength using fluoride-releasing and conventional bonding agents. Indian J Dent Res 2011;22:44-9

How to cite this URL:
Lodaya SD, Keluskar K M, Naik V. Evaluation of demineralization adjacent to orthodontic bracket and bond strength using fluoride-releasing and conventional bonding agents. Indian J Dent Res [serial online] 2011 [cited 2014 Oct 26];22:44-9. Available from: http://www.ijdr.in/text.asp?2011/22/1/44/79974
Dental caries is an infectious microbiological disease of the teeth that results in localized dissolution and destruction of the calcified tissue. Decalcification/demineralization (white spots) are carious lesions of varying extent. Higher incidence and severity of white spots after full-term orthodontic treatment have been found in individual teeth, whether bonded or banded, than in an untreated tooth. [1],[2] This suggests the need for a preventive program to reduce the amount of demineralization. One such preventive method is using fluoride associated with fixed appliance during orthodontic treatment. The role of fluoride in reducing the incidence of dental caries has been known for years. Today, most orthodontists directly or indirectly bond attachment to the teeth. Although bonding offers the advantage of better access for cleaning than banding, it does not necessarily guarantee better oral hygiene and improved gingival condition, especially if excess adhesive extends beyond the bracket base, and also the protection against interproximal caries provided by well-contoured cemented bands is absent. [3]

The maintenance of oral hygiene is more difficult with different orthodontic elements (elastics, springs, plastic sleeves) and thus accumulation of plaque is much easier. Prevention of enamel demineralization during fixed mechanotherapy remains a challenge to the orthodontist. Extensive overviews of different methods of orthodontic fluoride administration have been presented by various authors. [4],[5] Fluoride-releasing bonding adhesives were introduced to aid in the prevention of demineralization around bonded appliances. There are no sufficient studies regarding determination of the efficacy of fluoride-releasing bonding agents on demineralization. The present study is therefore planned to evaluate and compare the efficiency of fluoride-releasing bonding agent on the demineralization adjacent to orthodontic brackets with conventional bonding agent. An attempt is also made to compare the bond strength of the fluoride-releasing bonding agent with the conventional bonding agent.


   Materials and Methods Top


A sample size of 120 sound/healthy premolars with the following inclusion and exclusion criteria were subjected for the study:

Inclusion criteria

Healthy tooth indicated for extraction for orthodontic treatment

Exclusion criteria

  • Carious lesion
  • Restoration
  • Fracture
  • Developmental deformity
  • Stains
  • Fluorosis.
Various materials used in the study were

Adhesives

Control: "Ortho one," a self-cured adhesive manufactured by Bisco Inc. (USA).

Experimental

  1. "Tru-bond," a fluoride-releasing, self-cured composite resin manufactured by C. Dent Products Co. Ind. (USA).
  2. "Rely-a-bond," a fluoride-releasing, self-cured composite resin manufactured by Reliance Orthodontic Products Inc. (USA).
Etchant

Thirty-seven percent ortho phosphoric acid is used, which was provided by the respective manufacturer.

Primer

The primer provided by the manufacturer was used to bond the particular subgroup of the samples.

Brackets

Stainless steel Begg's curved brackets manufactured by GAC (Europe) with 3 mm×4 mm bracket base were used.

Acidic medium

Methyl cellulose buffered with acetic acid at a pH of 4.5 was used.

Cold cure material

DPI, RR cold cure acrylic was used.

Apparatus

The apparatus used were stereomicroscopy and Universal Instron-testing machine.

Pre-study procedure

One hundred and twenty extracted healthy premolars selected as per the inclusion and exclusion criteria were cleared of blood and soft tissue. Following debridement, the samples were stored in saline (0.9% NaCl) solution. One hundred and twenty samples of extracted teeth were divided into two groups, each consisting of 60 teeth.

Group I: Samples were used to study demineralization and were further subdivided in subgroups A, B and C (containing 20 samples each).

Group II: Samples were used to study shear bond strength and were further subdivided in subgroups A, B and C (containing 20 samples each).

Experimental subgroup: Subgroup sample A: were bonded with Rely-a-bond fluoride-releasing adhesive material.

Subgroup sample B: were bonded with Tru-bond fluoride-releasing adhesive material.

Control subgroup: Subgroup sample C: were bonded with Ortho-one conventional adhesive material.

Study procedure

(I) Sample preparation

Each sample was mounted on acrylic blocks (with the buccal surface available for bonding) with roots embedded in the fast-set polymethyl methacrylate resin [Figure 1].
Figure 1: View of specimen under the stereomicroscope

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(II) Bonding procedure

All the samples were cleaned and polished and further subjected for enamel conditioning. Bonding procedure for each subgroup was carried out by strictly adhering to the manufacturers' instructions. The acid-etchant (solution/gel) provided by the manufacturer was applied on to the enamel surface of the samples for 30 s and later thoroughly rinsed with water and dried for 10 s with an oil-free air source to obtain a dull, frosty appearance.

After the samples were completely dry and frosty white, a thin layer of primer provided by the manufacturer was painted on the base of the bracket. Composite was applied to the bracket base and bonded to the teeth with enough pressure to firmly seat the bracket on the teeth. Excess composite was removed with a hand scaler before the adhesive set.

The procedure remained the same for all the samples, but the material used was differed, i.e.

Subgroup A→bonded with Rely-a-bond

Subgroup B→bonded with Tru-bond

Subgroup C→bonded with Ortho-one

Group I samples

Twenty-fourh after bonding, the samples were placed in the acidic medium. After 4 weeks, the teeth were rinsed and dehydrated in an increasing concentration of alcohol (50%, 70%, 80%, 90%). The teeth were sectioned axially along the long axis with the help of a diamond disk. Sections were carefully washed and placed in pre-labeled  Petri dish More Detailses. The sections were oriented longitudinally on glass cover slides. These sections were observed under a stereomicroscope with maximum illumination. The distance between the edge of the adhesive on the enamel surface and the border of the demineralization zone was measured for all specimens in units. This unit was then converted in micrometer using the following formula:



Group II samples

After bonding, all the specimens were stored in saline water (0.9% NaCl) for 24 h and were later tested for shear bond strength using the Instron Universal-testing machine. The Instron Universal-testing machine having a load cell of 50 KN and crosshead speed of 1 mm/min was used [Figure 2]. The force value for each sample at which the bond failure occurred was recorded from the display panel of the computer in Newtons and was subsequently calculated in Mega Pascal using the formula below:



Figure 2: Bond strength testing of specimen shear mode

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Statistical analysis

The readings were tabulated for each of the groups and statistical analysis was performed using ANOVA for evaluation and comparison of demineralization and shear bond strength between the subgroups.


   Results Top


Evaluation of demineralization

The highest mean distance between the bracket base and the demineralization was noted in subgroup A (Rely-a-bond), 79.5 μm, followed by subgroup B (Tru-bond), 27.3 μm, and the least mean distance was noted in subgroup C (Ortho-one), 54.5 μm. A comparison of subgroup A and subgroup B showed statistically no significant difference using ANOVA. A comparison of the study and control groups revealed a statistical significant difference, with P<.001, HS [Table 1] and [Table 2].
Table 1: Comparison of demineralization adjacent to the orthodontic brackets, i.e. group I, between subgroups using ANOVA

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Table 2: Multiple comparisons with Tukey HSD

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Evaluation of shear bond strength

The highest mean shear bond strength was found in subgroup C (Ortho-one), 20.9 Mpa, followed by subgroup A (Rely-a-bond), 20.4 Mpa. Subgroup B (Tru bond) was found to have the least shear bond strength in this study, with a mean of 19.9 Mpa. There was statistically no significant difference between the subgroups using ANOVA [Table 3].
Table 3: Evaluation of shear bond strength in MPa between subgroups of group II

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   Discussion Top


Introduction of simplified bonding procedures has improved clinical practice in orthodontics. Demineralization of enamel surrounding orthodontic appliances still remains a significant clinical problem. This iatrogenically caused white spot leads to poor esthetics and, in severe cases, needs restorative treatment. Decalcification is particularly associated with the areas where plaque accumulation occur in the orthodontic patient. [6] As per an in vitro study, no difference in the prevalence of white spot (demineralized) lesions in banded or bonded teeth was found. [1] The presence of adhesive flash around a bonded orthodontic attachment can predispose to plaque; therefore, any excess adhesive should be cleared away before it cures. [7]

There are various methods of reducing decalcification during fixed orthodontic treatment, which are as follows:

  • Education: Educating the patient about the importance of diet and tooth cleaning throughout treatment, ideally, can help in reducing this problem, but this will not eliminate it. [8]
  • Mechanical plaque removal: Tooth brushing twice daily with a conventional or orthodontic brush should be supplemented by an interdental cleaning device. [9]
  • Chemical plaque removal:

    Chlorhexidine is the most effective chemical plaque removal agent, but has the disadvantage of staining the tooth surface. [10]

    Polymer adhesive Protecto (a protective agent applied around the attachment used to reduce decalcification under the bands). [11]

    New Seal (a fissure-sealing material) is found to be more effective than Protecto. [12]
  • Professionally applied fluoride: Painting sealant resin around orthodontic bands has also been suggested, but inhibition of polymerization limits the protection that is afforded. [6]
Post-eruptive fluoride application can reduce caries by the following mechanism: [13]

  • Acting as a type of catalyst, favoring the formation of high-quality hydroxyl-apatite crystals.
  • By aiding remineralization during pH fluctuation.
  • By inhibiting glycolysis of plaque bacteria.
This can be done with either of the following two mechanisms:

  • Daily mouth rinsing with 0.5% sodium fluoride solution has been shown to be effective in reducing the prevalence of decalcification. [14]
  • Professional fluoride gel application during orthodontic treatment is of proven efficacy. [15]
Evaluation of demineralization

In the present study, a significant difference in demineralization inhibition was observed between the fluoride releasing (Rely-a bond and/or Tru bond) and control (Ortho-one) groups. Ortho-one (non-fluoride releasing subgroup C) had the greatest demineralization zone, followed by Tru-bond (fluoride releasing subgroup B) and Rely-a bond (fluoride releasing subgroup A). The difference among the demineralization between the experimental and control subgroups was found to be statistically highly significant, with P<.001. There was statistically no significant difference between the two experimental subgroups, i.e. subgroup A and subgroup B.

In the current study, distance between edge of adhesive on enamel surface and border of demineralized zone was significantly longer for both fluoride-releasing groups as compared with the control (non-fluoride releasing group). Similar decalcification prevention has been reported in a study where the author examined two fluoride-releasing orthodontic agents with respect to fluoride release, enamel demineralization inhibition, as well as alterations observed on the enamel surface after their use. [16]

The results of the studies performed to evaluate the clinical durability and caries inhibition potential of fluoride-releasing composite resin were similar to the present study, [17],[18] although a subsequent study performed using light-activated material reported that its tensile bond strength was significantly less than that of a conventional resin. [19] This decrease in bond strength may be due to inadequate polymerization, rather than addition of sodium fluoride. [20] Because in vitro testing can never simulate oral conditions precisely, as in the present study, the results obtained cannot be extrapolated to assess the success of the material tested. Thus, variables present are numerous and the results need to be interpreted with care. Further research should focus on identifying the clinical relevance of fluoride released from the adhesives because different materials release different levels of fluoride at different intervals of time. [16]

Evaluation of shear bond strength

An ideal bonding system is one that affords optimal bond strength with minimal damage to the enamel surface. Clinically acceptable bond strength has been variably reported in the range of 5-7 Mpa as adequate [21],[22] and 6-9 Mpa as clinically acceptable. [23] These ranges of bond strength are considered to be able to withstand masticatory and orthodontic forces. In the present study, the mean bond strength values observed were in the range of 19.9-20.9 Mpa, which were above the minimal requirement level and were thus adequate to be clinically acceptable.

The current study reveals that subgroup C, i.e. the control group, had the highest shear bond strength of 20.9 Mpa. Statistically, no significant difference was found between subgroup A and subgroup C. Although a statistically significant difference was found between subgroup B and subgroup C, there was not much difference in the mean between subgroup B and subgroup C. Comparison of shear bond strength between experimental subgroups A and B revealed, statistically, no significant difference. An in vitro study indicated that GIC protected the enamel from decalcification. [24] However, GIC has been shown to have a weaker bond strength than composite resin. [25],[26]


   Conclusion Top


On evaluation and comparison of demineralization adjacent to orthodontic bracket, the fluoride-releasing bonding agents showed a lesser degree of demineralization as compared with the conventional bonding agents, and thus can aid in the prevention of demineralization adjacent to orthodontic brackets. There was no significant difference in the degree of demineralization between the two prototypes of the fluoride-releasing bonding system. Evaluation of shear bond strength revealed that both the fluoride-releasing and the non-fluoride releasing adhesive showed clinically acceptable bond strength. The Rely-a bond (i.e., fluoride-releasing adhesive) adhesive exhibits similar bond strength when compared with Ortho-one adhesive (i.e., non-fluoride releasing). Tru-bond adhesive (i.e., fluoride-releasing adhesive) had a lower bond strength as compared with Ortho-one adhesive (i.e., non-fluoride releasing). In the present study, the fluoride-releasing adhesive exhibited a lesser degree of demineralization adjacent to orthodontic bracket when compared with the conventional bonding agent, with clinically acceptable bond strength.

Considering the fact that this is an in vitro study, the above results should be viewed at a theoretical level, which may or may not occur in vitro, but may be accepted as an aid for the prevention of demineralization (white spot) with clinically accepted bond strength. Hence, the present in vitro study is an attempt to compare the bond strength and demineralization inhibition of fluoride-releasing and conventional non-fluoride releasing adhesive. Further in vitro studies and extensive exploration into this field are required to elucidate the truth.

 
   References Top

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3.Zachrisson BU, Zachrisson S. Caries incidence and oral hygiene during orthodontic treatment. Scand J Dent Res 1971;79:394-401.  Back to cited text no. 3
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9.Casey GR. Maintenance of oral hygiene and dental health during orthodontic therapy. Clin Prev Dent 1988;10:11-3.  Back to cited text no. 9
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13.Levin RS. Fluoride and caries inhibition effect. Dent Update 1991;18:76-9.  Back to cited text no. 13
    
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15.O'Reilly MM, Featherstone JD. Demineralization and remineralization around orthodontic appliances: an in vivo study. Am J Orthod Dentofacial Orthop 1987;92:33-40.  Back to cited text no. 15
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16.Basdra EK, Huber H, Komposch G. Fluoride release from orthodontic bonding agents alter the enamel surface and inhibits enamel demineralization in-vitro. Am J Orthod Dentofacial Orthop 1996;109:466-72.  Back to cited text no. 16
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18.Underwood ML, Rawls HR, Zimmerman BF. Clinical evaluation of a fluoride exchanging resin as an orthodontic adhesive. Am J Orthod Dentofacial Orthop 1989;96:93-9.  Back to cited text no. 18
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21.Miura F, Nakagawa K, Masuhara E. New direct bonding system for plastic brackets. Am J Orthod Dentofacial Orthop 1971;59:350-5.  Back to cited text no. 21
    
22.Voss A. In-vivo bonding of orthodontic brackets with glass ionomer cement. Angle Orthod 1993;63:149-53.  Back to cited text no. 22
    
23.Reynolds IR. A review of direct orthodontic bonding. Br J Orthod 1975;2:171-8.  Back to cited text no. 23
    
24.Valk JW, Davidson CL. The relevance of controlled fluoride release with bonded orthodontic appliance. J Dent 1987;15:257-60.  Back to cited text no. 24
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25.Cook PA, Youngson CL. An in-vitro study of the bond strength of a glass ionomer cement used for bonding of orthodontic bracket's. Br J Orthod 1988;15:247-53.  Back to cited text no. 25
    
26.Sfondrini MF, Cacciafesta V, Pistorio A, Sfondrini G. Effect of conventional and high intensity light curing on enamel shear bond strength of composite resin and resin modified glass-ionomer. Am J Orthod Dentofacial Orthop 2001;119:30-5.  Back to cited text no. 26
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Correspondence Address:
Siddharth D Lodaya
Department of Orthodontics and Dentofacial Orthopedics, KLES's Institute of Dental Sciences, Belgaum
India
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DOI: 10.4103/0970-9290.79974

PMID: 21525676

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    Figures

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  [Table 1], [Table 2], [Table 3]

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