|Year : 2021 | Volume
| Issue : 1 | Page : 52-58
Shear bond strength of orthodontic brackets using orthodontic and restorative self-etching primer. An in vitro study
Vasumurthy Sesham1, BR Anoob1, Praveen Kumar Neela1, Pavan Kumar Mamillapalli1, Lalitha Chiguripati2
1 Department of Orthodontics and Dentofacial Orthopaedics, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, Nalgonda District, Telangana, India
2 Department of Orthodontics and Dentofacial Orthopaedics, CKS Teja Institute of Dental Sciences, Narketpally, India
|Date of Submission||21-Feb-2020|
|Date of Decision||15-Dec-2020|
|Date of Acceptance||08-Mar-2021|
|Date of Web Publication||19-May-2021|
Dr. Vasumurthy Sesham
Department of Orthodontics and Dentofacial Orthopaedics, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, Nalgonda District, Telangana
Source of Support: None, Conflict of Interest: None
Background and Aim: Self-etching primers (SEPs) are used to reduce the chair side time. However, there are different SEPs that are used in orthodontics. This study is aimed to test the shear bond strength of brackets bonded using SEPs used in restorative dentistry in comparison to orthodontic SEPs.
Settings and Design: Department of Orthodontics, Post-graduate dental college, Council of Scientific and Industrial Research (CSIR) laboratory, in vitro study.
Methods and Material: Seventy-five freshly extracted human maxillary first premolar teeth were used in this study. Orthodontic maxillary first premolar McLaughlin Bennett Trevisi (MBT) metal brackets (3M Unitek) were used to bond the teeth. The study consisted of two groups. Group A: 25 teeth were etched with Orthodontic SEP Transbond Plus (3M Unitek). Group B: Experimental group which is divided into two subgroups, Experimental subgroup a and Experimental subgroup b. Subgroup a: 25 teeth were etched with Restorative purpose SEP Adper SE Plus (3M ESPE). Sub group-b: 25 teeth were etched with Restorative purpose SEP Adper Easy One (3M ESPE). In all the groups, the same adhesive material, Transbond XT (3M Unitek) was used for fixing the brackets. All the 75 teeth were subjected to shear force to test shear bond strength by using Instron machine.
Statistical Analysis: ANOVA & Scheffe multiple comparison test were used.
Results and Conclusion: Shear bond strength of brackets using orthodontic purpose SEP, Transbond Plus, is more than the SEPs used for restorative purpose, i.e., Adper SE Plus and Adper Easy One. Restorative purpose SEPs are not suitable for orthodontic bonding of brackets.
Orthodontic bonding, self-etching primer (SEP), shear bond strength (SBS)
Keywords: Orthodontic bonding, self-etching primer (SEP), shear bond strength (SBS)
|How to cite this article:|
Sesham V, Anoob B R, Neela PK, Mamillapalli PK, Chiguripati L. Shear bond strength of orthodontic brackets using orthodontic and restorative self-etching primer. An in vitro study. J NTR Univ Health Sci 2021;10:52-8
|How to cite this URL:|
Sesham V, Anoob B R, Neela PK, Mamillapalli PK, Chiguripati L. Shear bond strength of orthodontic brackets using orthodontic and restorative self-etching primer. An in vitro study. J NTR Univ Health Sci [serial online] 2021 [cited 2021 Dec 6];10:52-8. Available from: https://www.jdrntruhs.org/text.asp?2021/10/1/52/316326
| Introduction|| |
Orthodontics is constantly being improved with the use of new techniques and materials that benefit both the patients and the clinicians. Over the last 50 years, the bonding of various adhesives to enamel and dentin has developed a niche in nearly all areas of dentistry including orthodontics.
Adhesive bonding is important in orthodontics especially in terms of fixation of brackets to teeth. Since the advent of the acid etch technique in 1954 by Buonocore, and the bonding of orthodontic brackets by Newman in 1965, bonding research has strived to improve the delivery of orthodontic treatment. Orthodontic bonding gave rise to significant improvements in treatment such as greater patient comfort, elimination of the need for pretreatment tooth separation, improved oral hygiene, esthetics, reduced chair side time and decreased technique sensitivity without compromising the outcome.
The traditional three-step (etch, prime, adhesive) procedure has been used for years to successfully bond orthodontic brackets to teeth. Conventional bonding systems used three steps to prepare enamel surfaces, an enamel conditioner, a primer solution and an adhesive resin.
Simplification of technique and a reduction in the number of steps was desired. It was obvious that the more steps that were required to bond a bracket, the greater the potential for inconsistency in the timing of application, rinsing, drying, priming and maintaining a controlled operative field during treatment. This inconsistency has an impact on the success of the bond strength.
Manufacturers responded by placing research efforts in the development of self-etching primers (SEPs) mainly used for restorative dentistry.
Later SEPs were adopted into orthodontics for orthodontic bonding of brackets. The introduction of SEPs simplified the bonding process.
SEPs are considered as bicomponent hydrophilic adhesives containing hydrofluoric complexes, deionized water and stabilizer in one compartment and orthophosphoric acid ester methacrylate, activators and stabilizers in a separate compartment.
When the mixed solution is applied to the enamel, the acidic monomer becomes neutralized. The pH is raised by recruiting calcium ions from hydroxyapatite crystals. This halts demineralization and the ions become encapsulated in the primer to provide infiltration by the adhesive for suitable micro mechanical adhesion of the resin. The etch pattern produced by methacrylated phosphoric acid ester creates a pattern in the enamel and dentin similar to conventional acid etching. The bond strength of SEP can vary widely ranging from 2.8 to 11.5 megapascal (MPa).,,,
There are only a few self-etching adhesive products specifically marketed for orthodontic bonding. But there are many SEPs used in restorative dentistry. There were limited studies on SEPs intended for use in operative dentistry but used sometimes for orthodontic bonding of brackets.
So, the present study is aimed to test the shear bond strength (SBS) of brackets bonded using SEPs used in restorative dentistry in comparison to orthodontic SEPs.
| Materials and Methods|| |
Selection of teeth
Institutional Ethical committee waiver and permission from Institutional Review Board was taken before starting the study. Seventy-five human maxillary first premolars extracted for orthodontic purpose were collected from the department of oral and maxillofacial surgery and stored immediately in distilled water at room temperature. Teeth having hypoplastic enamel, cracks or fractures caused while extracting, caries and teeth subjected to any pretreatment chemical agents like hydrogen peroxide were not selected.
The selected teeth were mounted using cold cure acrylic resin in uniform-sized aluminum blocks of 3/4 inch x 3/4-inch dimensions. The teeth were mounted in such a way that the buccal surfaces of these teeth were parallel to the direction of the force application during the process of testing the shear bond force, or perpendicular to the central axis of the aluminum block and the palatal or the lingual cusp. The root surface was covered with acrylic to enhance the retention of the teeth.
The specimens were divided into three groups.
Control group: Group A: 25 teeth
Brackets to be bonded with orthodontic SEP Transbond Plus + Transbond XT Adhesive.
Experimental group – Group B (Restorative SEPs are used)
Group B is again divided into two subgroups a and b.
Subgroup – a: 25 teeth. Brackets to be bonded using restorative SEP Adper SE Plus + Transbond XT Adhesive
Subgroup – b: 25 teeth. Brackets to be bonded with SEP Adper Easy One + Transbond XT Adhesive
Coding for group and teeth
All the groups were color coded. Coloring for all the specimens was done on the upper half of the outer surface of the aluminum block. Yellow color was used for control group, violet color for experimental subgroup-a and red color for experimental subgroup-b. The teeth in each of these groups, which are color coded, are numbered from 1 to 25 for easy identification and data recording [Figure 1].
|Figure 1: Teeth mounted in aluminum blocks along with the colour coding and numbering A1-A25: Control group; a1-a25: Experimental group- a B1-b25: Experimental group-b|
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In preparation for bonding, each tooth was cleaned and polished with non-fluoridated flour of pumice in a rubber prophylactic cup on a slow speed hand piece for 10 seconds, rinsed with a stream of water and dried with an oil and moisture-free air stream.
Specimens were prepared for bracket bonding according to the following procedure.
Orthodontic maxillary first premolar MBT metal brackets (3M Unitek) were used in all the three groups [Figure 2]. The average bracket base surface area was determined to be 10.03 mm. The SEPs used in this study are Transbond Plus, Adper SE Plus and Adper Easy One. The adhesive used in all the three groups is Transbond XT (3M Unitek) shown in [Figure 3].
| Group A|| |
Twenty-five maxillary first premolars, separated as the Control group (Group A), were bonded with SEP Transbond Plus + Transbond XT Adhesive.
Buccal surface of the premolar teeth are etched with SEP Transbond Plus (3M Unitek), which contains both acid and the primer, for 15 seconds and gently evaporated with air, according to the manufacturer's instructions. For activation, the two components are squeezed together and the resulting mix is applied directly on the tooth surface. It contained a black (largest) reservoir, which was squeezed into the white (middle) reservoir, and then into the purple (smallest) reservoir of the blister package, using controlled pressure. Brackets were bonded onto the center of the buccal surface of the teeth with Transbond XT (3M Unitek), a light cured composite adhesive. Before curing the excess resin, material was removed with a sharp scaler, without disturbing the bracket position; the adhesive was light cured for a total of 20 seconds, following the manufacturer's instructions.
| Experimental Group B|| |
Sub Group - a
The buccal surface of 25 premolar teeth were etched with SEP Adper SE Plus, for 15 seconds; and gently evaporated with air, according to the manufacturer's instructions. Brackets were bonded using Transbond XT Adhesive (3M Unitek) and light cured for 20 seconds in the same manner as in the Control group.
Sub Group – b
The buccal surface of 25 premolar teeth were etched with SEP Adper Easy One, for 15 seconds; and gently evaporated with air, according to the manufacturer's instructions. Brackets were bonded using transport XT Adhesive (3M Unitek) and light cured for 20 seconds in the same manner as in Control group.
The teeth after bonding of the brackets in all the three groups are shown in [Figure 4].
Measurement of SBS
The SBS of the brackets was tested 24 hours after the bonding procedure. This was carried out at the prestigious National Institute of Interdisciplinary Science & Technology which is a constituent laboratory of the CSIR. An Instron universal testing machine was used for determining the bond strength in all the three groups. For shear testing, the prepared aluminum rim was fixed to the metal framework which in turn was secured in the lower jig of the Instron machine, with the long axis of tooth and bracket base parallel to the direction of shear force applied. A 15 mm loop was made using 0.012-inch stainless steel ligature wire and placed under the wings of the twin bracket. The free ends of the ligature wire were gripped in the upper jaw metal framework of the Instron machine Model No. 4467 [Figure 5]. The specimens were stressed in an occluso-gingival direction with a uniform crosshead speed of 5 mm/minute. The maximum force necessary to debond or initiate bracket fracture was noted in Newton, and then, converted into MPa as a ratio of Newton to the surface area of the bracket.
|Figure 5: Shear bond strength testing of the bonded brackets using INSTRON|
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| Results|| |
ANOVA test is used to determine whether there is any statistical difference in SBS between the three groups. Scheffe multiple comparison test was used to determine which group is significantly different from the other groups. Scheffe multiple comparison (Post hoc test) is used to compare the mean values of SBS of brackets bonded with different materials taken two at a time (pairwise) to assess where a significant mean difference exists.
Shear bond strength
Descriptive statistics including means, standard deviation, median, minimum and maximum values of all the three groups are given in [Table 1]. The mean SBS values were 9.2 ± 2.8 for the brackets bonded using Transbond Plus SEP, 2.5 ± 0.3 for Adper SE plus and 3.0 ± 1.6 for Adper Easy One.
|Table 1: Descriptive Statistics for Load at Maximum Tensile Stress in Different Groups|
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The results of ANOVA (F = 88.62) indicated statistically significant differences (P = 0.000) among the groups [Table 2].
Scheffe multiple comparison test indicated that Transbond Plus had a significantly higher SBS than Adper SE Plus and Adper Easy One [Table 3].
|Table 3: Scheffe Multiple Comparison of Load at Maximum Tensile Stress Based on Group|
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The F value (71.7, P < 0.01) for SBS between those brackets bonded with Transbond Plus and Adper SE plus is statistically significant at 0.01 level. It means that the SBS of brackets bonded with Transbond Plus is significantly high as compared to the brackets that bonded with Adper SE Plus.
The F value (60.80, P < 0.01) for SBS between those brackets bonded with Transbond Plus and Adper Easy One is statistically significant at 0.01 level. It means that the SBS of the brackets bonded with Transbond Plus is significantly high when compared to the brackets bonded with Adper Easy One.
But the comparison of SBS of the brackets bonded with Adper SE Plus and Adper Easy One (F = 0.4, P > 0.05) is not significant at 0.05 level. Thus, it can be concluded that SBS of Transbond Plus is significantly high as compared to Adper SE Plus and Adper Easy One, and SBS of Adper SE Plus and Adper Easy One does not differ statistically.
| Discussion|| |
Direct bonding of the brackets using acid etch bonding technique is now a routine orthodontic procedure. It is a clinically acceptable method provided all the steps of enamel conditioning (acid etching, rinsing, drying and application of bonding agent) are properly executed. However, in the conventional method, the acid etching and primer application are two different bonding steps which obviously take more operator time.
The introduction of newer simplified adhesive systems called self-etch primer, which combines acid etching and priming in a single step, has overcome the drawbacks of the conventional technique. One obvious advantage of using a SEP is to expedite the bonding procedure by combining etching and priming into a single step. In addition to saving time, fewer steps in the bonding process might translate into fewer procedural errors.
Because of the obvious advantages of SEPs, orthodontists started using SEPs. It is seen from the literature review that many studies have been carried out on these SEPs and the results of a majority of those studies showed that they give clinically acceptable bond strength.
The exact composition of SEPs manufactured by different companies, whether for the use in restorative dentistry or orthodontics, is not given by many of the brands and, if given, also is not identical. There are many SEPs used in the restorative dentistry. However, there are only a few self-etching adhesive products specifically marketed for orthodontic bonding. The studies on SEP's intended for restorative dentistry but sometimes used for orthodontic bonding of brackets are limited. It was decided to test the SBS using restorative purpose SEPs that were never previously used for orthodontic purpose. Hence Adper SE Plus and Adper Easy One were selected for the experimental group.
From the literature review, there were few studies like Adam et al. claiming that the use of self-etch primer with high pH showed higher SBS value. Some other studies like the study by Gregoire et al. showed that there is no influence of pH of self-etch primer on the SBS.
The literature review points to contradictory studies whether the self-etch primers used in restorative dentistry provide satisfactory SBS when used to bond orthodontic brackets. Study conducted by Zafer C Cehreli et al. showed that the use of self-etch primers like Prompt L Pop, Clearfil SE Bond, FL Bond, One-up BondF, NRC and Prime and Bond for bonding orthodontic brackets gave less SBS values. Another study conducted by Adam et al. showed that the use of self-etch primers like Adper Prompt L Pop, Clearfil S3 Bond, generally used in restorative dentistry, gave acceptable SBS values which are significantly not different from the SBS values obtained when Transbond Plus, an orthodontic SEP is used.
So, the present study was undertaken to test the efficacy of SEPs, intended for use in the operative dentistry, namely Adper SE Plus and Adper Easy One for orthodontic bonding of brackets in comparison to Transbond Plus, a SEP exclusively used for orthodontic bonding of brackets, in terms of SBS. In order to prevent the effect of adhesive resin on the SBS, Transbond XT is used in all the three groups to bond orthodontic brackets.
In a study conducted by Zafer C Cehreli et al. on Prompt L Pop, Clearfil SE bond, FL bond and One-up bond F, which are used in restorative dentistry, the SBS values obtained were under 2 MPa. In a study conducted by Adam et al., the SBS values obtained when using Adper Prompt L Pop was 5.9 ± 3.4 and when using Clearfil S3 Bond was 6.5 ± 1.9. The results of Adam et al. study showed that the SEP exhibited more SBS, whereas in our study, the mean SBS values were 9.2 ± 2.8 MPa for the brackets bonded using Transbond Plus SEP, 2.5 ± 3 MPa for Adper SE Plus and 3.0 ± 1.6 MPa for Adper Easy One. The findings of our present study are similar to the findings of Zafer C Cehreli et al. as far as Adper Easy Plus and Adper Easy One are concerned.
In a study conducted by Jacqueline AR Chávez et al., who compared SBS of brackets between two adhesive systems (SEP and MIP Transbond) at 60 minutes and 24 hours, the authors concluded that there was no statistically significant difference between Transbond MIP at 60 minutes (mean = 6.01, SD = 5.2) and SEP Transbond Plus at 60 minutes (mean = 7.35, SD = 5.1) (t = −.71 P = 0.48). Amit et al. compared the SBS of orthodontic bracket bonding with self-etch primers (Xeno V+, G-Bond) and conventional acid etching system where SEPs have significantly lower SBS, although, the values might still be clinically acceptable. In a study done by Sachdeva et al. on SBS of conventional acid etching, SEP and single bottle self-adhesive, the highest SBS was observed in Transbond XT, followed by G-Bond and lowest in Transbond Plus, though clinically acceptable SBS was seen in G-Bond. The results of the present study show that Transbond Plus has got the highest SBS among the SEP's tested. When compared with the previous studies, the results are similar for Transbond Plus, but it is not the same for Adper SE Plus and Adper Easy One. The finding of our study on SBS value when Transbond Plus (9.2 ± 2.8 MPa) is used in orthodontic bracket bonding is similar to the previous studies conducted by Samir E Bishara et al.
The possible reasons for the lack of adequate SBS values of these restorative self-etch primers, if used in orthodontic bonding of brackets, may be due to weaker etching pattern with little dissolution of enamel crystallites and rods leaving only shallow fossae and grooves. It may also be due to differences in the chemical composition, mainly the concentration of the etchant in the self-etch primers used in restorative dentistry and the one used in orthodontics.
| Conclusions|| |
This was an in vitro study designed to test the SBS of orthodontic brackets bonded with SEP intended for use in restorative dentistry, Adper SE plus, Adper Easy One in comparison with SEPs used for orthodontic purpose, Transbond Plus.
- Transbond Plus, an SEP used exclusively for orthodontic bonding of brackets has got the highest SBS.
- The other two SEPs, i.e., Adper SE Plus and Adper Easy One, which are otherwise used in the operative dentistry, gave lower SBS values that are clinically not acceptable. These products are not suitable for orthodontic bracket bonding in terms of the SBS achieved.
- Hence, SEPs used in restorative dentistry are not suitable for orthodontic bonding.
We are thankful to the National Institute of Interdisciplinary Science & Technology which is a constituent laboratory of the CSIR for its cooperation in conducting the testing and also the qualified statistician who did the statistical work.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]