|Year : 2015 | Volume
| Issue : 4 | Page : 390-395
|Comparison of shear bond strength of self-etching fluoride releasing adhesives with and without pumice prophylaxis
VR Shobbana Devi1, M Kumaraswamy Anand1, S Venkateswaran2, Kavitha S Iyer1, NR Krishnaswamy1
1 Department of Orthodontics and Dentofacial Orthopedics, Ragas Dental College and Hospital, Uthandi, Tamil Nadu, India
2 Department of Orthodontics and Dentofacial Orthopedics, Chettinad Dental College and Hospital, Kelambakkam, Chennai, Tamil Nadu, India
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|Date of Submission||26-Oct-2013|
|Date of Decision||17-Mar-2015|
|Date of Acceptance||16-Jul-2015|
|Date of Web Publication||20-Oct-2015|
| Abstract|| |
Context: Despite the advances in orthodontic material and treatment mechanics, the placement of fixed appliances increases the risk of enamel demineralization. The development of fluoride release adhesives has attracted considerable interests because the combined use of antimicrobials and fluoride enhances the cariostatic effect.
Aim: To compare the shear bond strength (SBS) of fluoride release adhesives with established orthodontic adhesives and assess failure mode using adhesive remnant index (ARI).
Settings and Design: The present study included 80 maxillary premolars which were randomly divided into four groups (n = 20) and were further subdivided into two subgroups A - Pumice prophylaxis (PP) and subgroup B - No PP (n = 10).
Materials and Methods: Stainless steel brackets were bonded with Transbond XT, Transbond plus (TP) color change adhesive, Light Bond, and Clearfil protect bond. After debonding, the ARI was used to assess the mode of bracket failure.
Statistical Analysis: The data were analyzed using two-way analysis of variance, Post-hoc Tukey Honest significant differences test, and Chi-square test.
Results: The mean SBS of Group 4 was comparably higher regardless of PP. Brackets bonded with TP showed a comparable SBS to conventional Transbond XT. The ARI scores were predominately 2.
Conclusions: Fluoride releasing adhesives combined with antibacterial monomer can play a vital role in reducing white spot lesions by enhancing the cariostatic effect especially in noncompliant\medically compromised patients.
Keywords: Antibacterial monomer, fluoride, pumice prophylaxis, self-etching primer, shear bond strength
|How to cite this article:|
Shobbana Devi V R, Anand M K, Venkateswaran S, Iyer KS, Krishnaswamy N R. Comparison of shear bond strength of self-etching fluoride releasing adhesives with and without pumice prophylaxis. Indian J Dent Res 2015;26:390-5
|How to cite this URL:|
Shobbana Devi V R, Anand M K, Venkateswaran S, Iyer KS, Krishnaswamy N R. Comparison of shear bond strength of self-etching fluoride releasing adhesives with and without pumice prophylaxis. Indian J Dent Res [serial online] 2015 [cited 2019 Jul 18];26:390-5. Available from: http://www.ijdr.in/text.asp?2015/26/4/390/167639
The development of an ideal bonding system to attach the orthodontic brackets to the teeth is an area of constant interest for researchers. Phosphoric acid has remained the primary etchant since its introduction by Buonocore. Conventional adhesive use three agents: An enamel conditioner, a primer solution, and an adhesive., To reduce the chair time, self-etching primers (SEP) were developed.
The proposed advantages of SEP during orthodontic bonding is that it allows the primer and etchant to be simultaneously used on the enamel and dentin, which helps to reduce technical errors, eliminates cross-contamination, reduces chair time, and minimizes enamel loss during debonding.,,,
The placement of fixed appliance facilitates the retention of plaque and increases the risk of enamel demineralization. Øgaard et al., reported that this is a consequence of the cariogenic plaque around fixed appliances. Fluoride delivery system may be of benefit, especially in orthodontic patients. Various method of fluoride administration, such as toothpastes, gels, mouth rinses, and varnishes have been advocated, but none is effective in preventing enamel demineralization. One of the key issues in orthodontics is preventing enamel demineralization during treatment. Therefore, an ideal adhesive system should have sufficient bond strength and at the same time prevent enamel demineralization.
The objectives of this in vitro study were to compare the shear bond strength (SBS) of fluoride release adhesives with established orthodontic adhesives, with and without pumice prophylaxis (PP) using SEP and to report bracket failure mode using adhesive remnant index (ARI).
The null hypothesis was as follows:
- There is no difference in the SBS of conventional and fluoride release adhesives.
| Materials and Methods|| |
Eighty human maxillary premolars extracted for the orthodontic purpose were cleared of any debris and stored in distilled water for 24 h. The criteria for their selection were intact buccal enamel; no pretreatment with peroxide, acid, or alcohol; no caries; no restoration; and no visible cracks due to pressure from extraction forceps. The teeth were randomly divided into four groups of 20 teeth each. Each tooth was mounted in auto polymerized resin upto the cemento-enamel junction and was color coded for identification. The four groups were further divided into two subgroups A and B of 10 teeth each as shown in [Figure 1].
|Figure 1: The various groups and subgroups in this study. TPSEP = Transbond plus self etching primer, TP = Transbond plus fluoride release adhesive|
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Prior to bonding, the labial surfaces of all teeth in subgroup A were cleaned with pumice using prophy cup, rinsed with water and air-dried. PP was omitted in subgroup B.
Group I (control): The teeth were etched with Transbond plus SEP (TPSEP) for 5 s. A gentle air burst was delivered using oil and moisture-free air source to dry primer into a thin layer. The brackets were coated with Transbond XT (conventional) adhesive and light cured for 40 s.
Group II: TPSEP and Transbond plus (TP 3M Unitek) color change adhesive was used as mentioned above. The fluoride release adhesive contains a fluorosilicate glass as the source of fluoride. The hydrophilic nature of the fluoride allows fluoride diffusion through the cured cross-linked matrix in an aqueous medium. In addition, the pink color provides a visual aid for removal of excess adhesive.
Group III: TPSEP and Light Bond (reliance orthodontic products), a fluoride release adhesive was used as mentioned above.
Group IV: The teeth were etched with Clearfil protect bond (Kuraray), this two-step SEP contains sodium fluoride to resist demineralization. Additionally, it contains 12-methacryloxyloxydecyl-pyridinium bromide (MDPB); the antibacterial agent is a functional monomer that destroys the cell membrane of bacteria. After a gentle application for 15 s, the primer was air dried to evaporate the solvent. Then, the bonding agent was applied, and gently air flowed and cured for 10 s. The brackets were coated with TP and used as mentioned above.
All teeth were light-cured with a halogen light (3M Unitek) for 40 s. The test specimens were stored in distilled water for 24 h at 37°C ± 2°C simulating oral environment. Literature evidence has shown that even vigorous thermocycling does not represent the normal oral environment. The brackets used in this study were premolar metal brackets (Lancer, Roth 0.022 slot) with an average bracket base area of 9 mm 2.
Following mounting, the teeth were debonded using Lylod Universal testing machine. The test specimens were stressed in an occluso-gingival direction at a crosshead speed of 1 mm/min. The results of each test were recorded electronically on a computer connected to the Llyod universal testing machine.
Adhesive remnant index
Once the brackets were debonded, the enamel surface of each tooth was examined at ×10 magnification in a stereomicroscope to determine the amount of residual adhesive remaining on each tooth.
An ARI  was used to quantify the amount of adhesive left on the enamel surface, using the following scale.
0 = No adhesive on tooth surface
1 = Less than half
2 = More than half
3 = All adhesive on tooth surface
Descriptive statistics (mean and standard deviation) at 95% confidence intervals were calculated for SBS. Two-way analysis of variance (ANOVA) were used to test the main effects of pumice and nonpumice group and self-etching fluoride release adhesive on the SBS and to identify where the differences occurred. One-way ANOVA followed by Tukey Honest significant differences test (P < 0.05) were used appropriately to compare the mean values of the four groups used. The Chi-square test (χ2) was used to determine significant differences in the ARI scores between the different groups.
| Results|| |
Descriptive statistics in megapascals (MPa) for all four groups are presented in [Table 1]. The mean SBS presented in [Figure 2], was highest for Group 4 with PP, and between the subgroups A and B, subgroup A showed higher bond strength considerably in all groups. The mean SBS was least in Groups IIIA and IIIB (Light Bond).
|Figure 2: Mean shear bond strength and standard deviation in MPa for all groups with and without pumice prophylaxis|
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[Table 2] shows the distribution of the ARI scores for all groups. Failure site was mainly at the adhesive/bracket interface. In Groups IIIA and IIIB Scores 1 and 2 were dominant, whereas Scores 2 and 3 were prevalent in Groups IVA and IVB.
| Discussion|| |
SEP in orthodontics gained popularity because they save chair time by eliminating the need for separate etching and priming. The SEP contains methacrylated phosphoric acid esters, which will both etch and prime the enamel simultaneously. The calcium forms a complex with phosphate group which gets incorporated when the primer polymerizes [Figure 3],[Figure 4],[Figure 5]. SEP also reduce postoperative sensitivity since it dissolves the smear layer without exposing dentinal tubules.
|Figure 3: During the etching process, the acid group is neutralized by reaction with calcium|
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|Figure 4: Primer molecules penetrate the enamel rods concurrent with etching|
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|Figure 5: Following curing, primer molecules are polymerized to form a network|
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During conventional etching, between 10 and 30 µm of the enamel surface layer is lost. SEP are less aggressive in their etching capability, which results in less enamel loss, and there is a less need to remove residual adhesive after debonding. The pH of the SEP is not the only determining factor others include acid dissociation constant, matrix structure, application time, and solubility of salts.In vitro studies by Bishara et al. found that the mean SBS of brackets bonded with SEP was lower than those bonded with a conventional etchant.
Reynolds  proposed that clinically acceptable bond strength should be in the 6-8 MPa range. The maximum bond strength should be less than the hardness of enamel which is about 14 MPa. Since the depth of enamel dissolution during etching is also important, the potential use of SEP has been studied to improve the bonding procedure by minimizing enamel loss and still maintain sufficient bond strength.
A concern with SEPs other than the increased cost is the adequacy of their bond strength, which remains controversial. In an in vivo study by Ireland et al. TPSEP versus conventional etch were evaluated but disregarded the PP for all groups. They found a significantly greater number of bond failures in the SEP group. This demonstrates the need to pretreat enamel when using SEP. Rubber cup prophylaxis was employed in the present study since the enamel loss with rubber cup prophylaxis is 6.9 µm as against bristle brush which is 14.38 µm. Therefore, one of the aims of the present study was to determine the clinical importance of PP when using SEP.
As orthodontic patients have an increased risk of developing white spot lesions predominately in sites adjacent to brackets, appropriate levels of fluoride ions are needed to provide an anti-carious benefit by promoting enamel remineralization. Some of the preventive efforts in this high-risk group include the use of fluoride release adhesive and antibacterial monomer to maintain a constant presence of fluoride in the oral cavity. Fluoride release adhesives contain a fluorosilicate glass as the source of fluoride. The hydrophilic nature of the fluoride allows fluoride diffusion through the cured cross-linked matrix in an aqueous medium.
Imazato et al., reported the use of an antibacterial adhesive system by incorporation of the monomer 12-MDPB that has a strong bactericidal activity against oral bacteria. Furthermore, cured primer incorporating MDPB exhibits inhibition of bacterial growth on its surface by mobilizing antibacterial components. When fluoride ions are incorporated into the surface of the enamel, a fluroapatite crystal structure is formed that has a lower solubility in the oral environment compared with hydroxyapatite.
The present study evaluated the SBS of three fluoride releasing self-etching adhesives with and without PP. The findings indicate that Group 2A (TP) provide a mean SBS of 12.10 MPa similar to that of the Group IA (Transbond XT) which was 12.36 MPa. However, Group 3A (Light Bond) showed a significantly low mean SBS of 10.5 MPa than other groups. Group 4A (MDPB antibacterial monomer) showed the highest mean SBS of 14.26 MPa. There was statistically no difference between Group 1A (Transbond XT with PP) and Group 2A (TP with PP), but significant difference existed between Group 3A (Light Bond) and Group 4A (MDPB with PP), and between Groups 1A and 4A, between Groups 1A and 3A, between Groups 2A and 3A, and between Groups 2A and 4A significance at 5% level.
There was statistically no difference between Group 1B (Transbond XT without PP) and Group 2B (TP without PP), but significant difference existed between Group 3B (Light Bond without PP) and Group 4B (MDPB without PP), and between Groups 1B and 4B, between Groups 1B and 3B, between Groups 2B and 4B, and between Groups 2B and 3B significance at 5% level. The null hypothesis is accepted when fluoride and nonfluoride adhesives of the same company (3M Unitek) is used.
According to Proffit  the forces produced by mastication are highly variable with ranges approximately 5 MPa and 20 MPa for anteriors and posteriors, respectively. The force required for moving a tooth orthodontically range between 15 and 150 g. In the oral cavity, the bonded brackets are subjected to shear, tensile, and torsional forces.
The lower the amount of force required to remove the bonded bracket, the lower the risk of enamel fracture on debonding. Clinically, the bond strength of the adhesive should be sufficient to withstand the masticatory forces, the stress exerted by the arch wires, and patient abuse. At the same time, the bond strength should be at a level to allow bracket debonding without causing damage to enamel surfaces.
In this study, the dominant ARI score was 2 (n = 21 pumice, n = 20 nonpumice), indicating that failure was at the adhesive-bracket interface, offering better protection to the enamel during debonding.
Limitations of the study
The test specimens were stored in distilled water, unlike the saliva in the oral cavity which is in a dynamic state.
Current results are based on laboratory investigations, but in clinical setting bonding systems are exposed to a number of different intraoral factors, but nevertheless, in vitro testing serve as a gateway for clinical trials.
| Conclusion|| |
In our study, we were able to assess whether TP, Light Bond, and Clearfil protect bond, has got an adequate advantage for using as bonding agents in orthodontics.
According to the results of the present study, the following conclusions were drawn:
- All three self-etching fluoride release adhesive combinations with or without PP used in this study demonstrated clinically acceptable bond strength equal to Transbond XT
- The mean SBS of antibacterial and fluoride-release adhesive were higher compared to all other groups
- The mean SBS of Group 3 was the least compared to other groups, although it is sufficient to withstand masticatory forces
- By omitting the PP in sub Group B, the SBS reduced considerably in all four groups but not below the optimal level
- The predominant ARI score was 2 indicating that the bracket failure mode was at the adhesive bracket interface.
Future research directions
This study was undertaken to create awareness among clinicians that the use of fluoride release adhesives in addition to fluoride mouth rinse might reduce the occurrence of white spot lesions. With the addition of MDPB, adhesive resins not only work as a bonding agent but also as antimicrobials that can be used for bonding buccal tubes in patients with bacterial endocarditis.
However, further clinical studies focusing on clinical efficiency in reducing carious lesions in patients with fixed orthodontic appliance would be worthwhile.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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V R Shobbana Devi
Department of Orthodontics and Dentofacial Orthopedics, Ragas Dental College and Hospital, Uthandi, Tamil Nadu
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]
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