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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 13  |  Issue : 6  |  Page : 1168-1173  

Comparative evaluation of shear bond strength of brackets bonded with self etch primer/adhesive and conventional etch/primer and adhesive system


1 Department of Orthodontics and Dentofacial Orthopaedics, Awadh Dental College and Hospital, Jamshedpur, Jharkhand, India
2 Department of Orthodontics and Dentofacial Orthopaedics, Patna Dental College and Hospital, Patna, Bihar, India

Date of Submission21-May-2021
Date of Decision05-Jun-2021
Date of Acceptance10-Jun-2021
Date of Web Publication10-Nov-2021

Correspondence Address:
Komal Neha
Department of orthodontics and dentofacial orthopaedics, Awadh dental college and hospital, Jamshedpur, Jharkhand
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jpbs.jpbs_412_21

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   Abstract 


Introduction: The shear bond strength obtained with an acid primer might not be clinically reliable. The present study evaluated the use of a new self-etch primer as compared with the conventional bonding procedure. The findings indicated that the use of a self-etch primer to bond orthodontic brackets to the namel surface provided lower, but clinically accept-able, shear bond forces (mean, 7.1 ± 4.4 MPa). Hence, this study has been designed to evaluate the shear bond strength of orthodontic brackets bonded with a self-etching primer system, and compare it with the conventional acid etching priming system. Materials and Methods: This study was designed to compare the shear bond strength of orthodontic brackets bonded with conventional acid etching- priming and a self-etching primer. For this purpose, one hundred and twenty noncarious, not subjected to any pretreatment chemical agents (e.g. hydrogen peroxide), no cracks caused by the presence of the extraction forceps, no caries and unrestored human maxillary 1st and 2nd premolars, freshly extracted for orthodontic treatment were collected and stored in distilled water before bonding. Separate molds of cold-cure acrylic were prepared and the extracted premolar teeth were embedded in the cold cure acrylic up to the cement enamel junction. Results: For the control group, the mean shear bond strength was 9.38 ± 6.02 MPa and for the experimental group, it is 6.91 ± 3.58 MPa. Group comparison using Chi-square test for the self-etching primer group adhesive remnant index (ARI) scores shows that more than half of the adhesive left over the tooth surface (score 3 and 4). For the conventional group, ARI scores show that there was no or slight amount of adhesive left over the tooth surface (score 5). The proportion of ARI score is significantly (P < 0.001) more in conventional (68.33%) as compared to self-etch primer (SEP) (28.33%). The proportion of ARI scores 4 and less is significantly more in SEP (71.67%) as compared to Conventional (6.67%) with P = 0.004 as per the Chi-square test. Conclusion: The bond strength of SEP is comparatively lesser than the conventional acid etching technique, but is definitely more or less to the required bond strength to resist masticatory forces. Majority of the studies conducted on self-etching primer are in vitro studies. Results of these cannot be extrapolated to the intraoral environment. Hence, further long-term clinical studies need to be carried out before actually recommending the use of self-etching primer in routine orthodontic bonding.

Keywords: Adhesive system, adhesive, convprimer, self etch primer


How to cite this article:
Bhattacharjee D, Sharma K, Sahu R, Neha K, Kumari A, Rai A. Comparative evaluation of shear bond strength of brackets bonded with self etch primer/adhesive and conventional etch/primer and adhesive system. J Pharm Bioall Sci 2021;13, Suppl S2:1168-73

How to cite this URL:
Bhattacharjee D, Sharma K, Sahu R, Neha K, Kumari A, Rai A. Comparative evaluation of shear bond strength of brackets bonded with self etch primer/adhesive and conventional etch/primer and adhesive system. J Pharm Bioall Sci [serial online] 2021 [cited 2022 Jun 26];13, Suppl S2:1168-73. Available from: https://www.jpbsonline.org/text.asp?2021/13/6/1168/330137




   Introduction Top


After the introduction of the acid etches technique in 1955 by Buonocore un-esthetic procedure with the multiband appliance has been virtually discarded. Newman's attempt in 1965 to bond orthodontic attachment to teeth using an epoxy resin opened a new horizon in orthodontics and era of bandless treatment was born.[1],[2]

Conventional bonding of orthodontics brackets with filled diacrylate adhesives involves 4 distinct stages. First, the enamel surface is polished with slurry of pumice in water with a slow speed hand piece. It is then conditioned with 37% of phosphoric acid for 30 s, followed by washing with water and air-drying until the enamel is frosty white. Finally, a primer is painted on the etch enamel, the bracket is placed on the teeth, and the adhesive is cured. Recent studies have questioned the need for some of these stages. Pumicing has been shown to be unnecessary because it has no effect on in vivo bond failure rates before conventional etching. Laboratory studies on measured bond strength. have found that a primer has no effect with either chemically cured or light-cured diacrylate. Sealants have also been suggested as a means of reducing enamel decalcification during treatment. Although clinical studies have found that commonly used low-viscosity sealants have no effect.[3],[4]

The self-etching primer system consists of etchant and primer dispersed in a single unit. The acid component of the system demineralizes the enamel surface and the etched enamel gets simultaneously primed. Hence, the etching and priming are merged as a single step leading to a fewer stage in the bonding procedure, resulting in time-saving for the clinician, which has cost implications. It also results in smaller extent of enamel decalcification.[5]

Bishara and Gordon[6] concluded that the shear bond strength obtained with an acid primer might not be clinically reliable. The present study evaluated the use of a new self-etch primer as compared with the conventional bonding procedure. The findings indicated that the use of a self-etch primer to bond orthodontic brackets to the namel surface provided lower, but clinically accept-able, shear bond forces (mean, 7.1 ± 4.4 MPa).[10]

Hence, this study has been designed to evaluate shear bond strength of orthodontic brackets bonded with a self-etching primer system, and compare it with the conventional acid etching priming system.


   Materials and Methods Top


This study was designed to compare the shear bond strength of orthodontic brackets bonded with conventional acid etching- priming and a self-etching primer. For this purpose, one hundred and twenty noncarious, not subjected to any pre-treatment chemical agents (e.g. hydrogen peroxide), no cracks caused by the presence of the extraction forceps, no caries and unrestored human maxillary First and second premolars, freshly extracted for orthodontic treatment were collected and stored in distilled water before bonding. Separate molds of cold-cure acrylic were prepared and the extracted premolar teeth were embedded in the cold cure acrylic up to the cement enamel junction.

In preparation for bonding, each tooth was cleaned and polished with, pumice paste applied with a rubber cup on a slow speed handpiece for 10 s, rinsed with water and dried with an oil and moisture free airstream.

Koden MIM orthodontic brackets were used in the study. The average bracket base surface area was determined to be 10.037 mm2. The SEP used in this study is Transbond Plus (3M Unitek). Samples were divided into two different groups each containing 60 maxillary left and right first and second premolar teeth.

Group – 1: Control Group – bonding with conventional acid etching – priming.

Group – 2: Experimental Group – bonding with self-etching primer (Transbond Plus).

Bonding procedure

Group I – Control Group: 60 teeth were etched with 37% phosphoric acid. Teeth were etched for 40 seconds, rinsed and air-dried. A thin layer of Transbond XT primer (3M Unitek) was applied to the enamel surface and light-cured for 10 s. Brackets were bonded onto the center of the buccal surface of teeth with Transbond XT (3M Unitek), a light-cured composite adhesive. Before curing, the excess resin material is removed with a sharp probe without disturbing the bracket position; the adhesive was light-cured for a total of 40 seconds, following the manufacturer's instruction.

Group – II – Experimental Group: 60 teeth were etched and primed by using self-etching primer that is Transbond Plus (3M Unitek), which contains both the acid and the primer and it is applied on the enamel surface of 60 teeth for 3 s 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 contains a black (largest) reservoir were squeezed into white (middle) reservoir and then into purple (smallest) reservoir of the blister package using control pressure. The brackets were bonded using Transbond XT adhesive (3M Unitek) and light-cured for 40 s, in the same manner as in Group I.

Statistical software

The Statistical software namely SPSS 11.0 (IBM, Armonk, New york) and Systat 8.0 (IBM) were used for the analysis of the data and Microsoft Word and Excel have been used to generate graphs, tables, etc. If P < 0.05 Statistical Significance at 5% and P < 0.01 Statistical significance at 1%.


   Results Top


Shear bond strength mean shear bond strength for the conventional group and self-etching primer group are shown in [Table 1] and [Table 3], respectively. For the control group, the mean shear bond strength was 9.38 ± 6.02 MPa and for the experimental group, it is 6.91 ± 3.58 MPa. This shows that the shear bond strength of the control group was significantly increased compared to the experimental group.
Table 1: Distribution of bond strength between SEP and convention

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Table 3: Comparison of bond strength between two group

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It is observed that the bond strength of conventional data more accurately fits the Weibull distribution as compared to SEP as is observed circles are more closely toward the diagonal. Comparison of groups was done using the Chi-square test. For the self-etching primer group, adhesive remnant index (ARI) scores show that more than half of the adhesive left over the tooth surface (score 3 and 4). For the conventional group, ARI scores show that there was no or slight amount of adhesive left over the tooth surface (score 5). Most of the failures in the control group were between the tooth surface and adhesive, where as in the case of self-etching primer it occurred within the resin leaving more than half of the adhesive on the teeth.

Study design

A comparative study consisting of 120 maxillary first and second premolar teeth were randomized into two groups 60 for SEP and 60 for conventional is undertaken to investigate the pattern and magnitude of Bond strength failure between SEP and Conventional bonding procedure.

Inference-the conventional group is 4.55 times more likely to have more bond strength (above normal bond strength 6–8 MPa) compared to SEP with χ2 = 12.437, P < 0.001.

Inference Comparison of the shear bond strength in Mpa was done between the SEP and the conventional group with mean and standard deviation of 6.91 ± 3.58 and 9.38 ± 6.02 with a range of 1.40–15.45 and 2.70–22.20 and 95% confidence interval of 5.98–7.72 and 8.41–10.44. Findings were the bond strength of significantly higher values of conventional group with [Table 1], [Table 2], [Table 3], [Table 4].
Table 2: Percentile distribution of bond strength

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Table 4: ARI score

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   Discussion Top


Several studies have been carried which proved that the shear bond strength of self-etching primer and resin system was significantly quite similar or more than the conventional system. Ireland et al.[7] evaluated a higher bond failure rate (10.99%) with the self-etching primer as Buyukyilmaz et al.[8] compared to the control conventional etch and priming group (4.95%) even Bishara et al.[6] evaluated the mean shear bond strength of the two-step acid-etch primer/adhesive was 5.9 ± 2.7 MPa and the mean for the one-step system was 3.1 ± 1.7 Mpa in his research with P = 0.001 which was more significant and which correlates the finding in my research showing the bond strength of the conventional technique is higher than the single-step bonding procedure as shown in [Table 3]. Even in some conditions, the bond strength of self-etch bonding system is higher than the multi-step bonding procedure as in the conditions of contaminations by saliva and blood.[9] However, the bond strength of self-etch primer reduces significantly if contamination by saliva occurs both before and after primer application as shown by Mao and Qi[10] in his studies. Bergeron et al.[11] and Bishara et al.[12] reported a significantly higher shear bond strength of self-etched primer than that found in the control acid-etched group. Fritz et al.[13] reported that self-etching primers CLB and SE is as effective as the conventional group. Hitmi et al.[14] reported a value of (29 ± 6 MPa) SEP almost similar to the value obtained (31.1 ± 5 MPa) from the control group. Asgari et al. reported a low bond failure rate of SEP (0.57%) compared to the conventional group (4.60%). reported with bond strength of SEP (16 ± 4.5 MPa) which is significantly higher than the control acid-etched group. Cacciafesta et al.,[15] Vicento et al.[16] and Dorminey et al.[17] stated with the same bond strength between SEP and control acid-etched group. Bishara et al.[6] used a heavily filled adhesive with Transbond Plus self-etching primer to bond brackets and reported bond strength of 10.4 ± 4.4 MPa. However, he found much lower bond strength of 5.9 ± 5.6 MPa with a lightly filled adhesive. In a subsequent study, he reported very low bond strength of 2.8 ± 1.9 MPa which was not clinically acceptable.[12]

In a more recent study, however, he reported shear bond strength of 7.1 ± 4.4 MPa with transbond plus which is clinically admissible.

Hence, this study was performed to assess the shear bond strength of orthodontic brackets bonded with a self-etching primer system and with conventional acid etching-priming system. In the control group, mean shear bond strength was 9.38 ± 6.02 MPa. In the self-etching primer group, mean shear bond strength was 6.91 ± 3.58MPa [Table 3]. There was a significant rise in the bond strength of the control group compared to the experimental group. Majority of studies showed that the shear bond strength of brackets bonded with the self-etching primer was significantly less than those of the conventional two-stage bond system.

Possible explanation for this could be the difference in chemical composition and concentration of the etchant between the two systems. The self-etching primer uses phosphoric acid esters whose concentration is not given in the marketed product literature whereas the conventional two-stage bonding system is based on 37% ortho-phosphoric acid.

According to Hannig et al.[18] the self-etching primer contains etchant and primer in one chemical compound. In addition, the mode of etching/priming between the two bonding systems is also different. (Simultaneous etching/primer vs. separate etching and priming stages for the conventional two-stage bonding system). It combines etchant and primer in one chemical compound. When the Self-etching primer is activated and the monomer is rubbed on to tooth, H + ions are released from the phosphate group of monomer and etch.

The tooth structure thereby creating a three-dimensional micro retentive surface pattern. Ca++ ions released from the hydroxyapatite crystals react with the monomer, which undergoes a polymerization reaction. This monomer subsequently reacts with the composite resin applied for bonding brackets and forms a complex.

Enamel etching and procedure of resin penetration occur hand in hand so, the depth of the bonding agent and extent of etched enamel is similar. As a result, light-curing of these interpenetrated monomers and copolymerization with the overlying resin bonding agent and composite resin creates a continuous bond with the enamel surface. Since the primer is not rinsed and only air-dried, the calcium and phosphate ions that were dissolved from hydroxyapatite crystals must be suspended in the watery solution of the primer. When the water is evaporated during air drying, the concentration of solubilised calcium and phosphate within the primer may exceed the solubility product constants for a number of calcium phosphate salts.

Probably minerals will then precipitate within the primer. These high concentrations of calcium and phosphate will start to limit further dissolution of the apatite due to the common ion effects of calcium and phosphate and thereby limiting the depth of enamel surface demineralization. On the other hand, it is very likely that the binding of calcium ions to the phosphate residues in primer molecules contribute to the inactivation of the molecule's acidity. In addition, evaporation of water during air drying, as well as light curing of the primer and subsequently applied bonding agents, will restrict and inhibit the self- etching effect of the primer molecules. During the rinsing step in conventional bonding with phosphoric acid, a lot of unsupported enamel may be drained away resulting in fewer retentive areas and also a considerable loss of enamel. While during the self-etch priming, etched enamel is left intact and undisturbed, followed by immediate bonding. This leaves a greater amount of enamel available for bonding and reduces the extent of enamel loss. This explains the equivalent bond strength obtained with Transbond Plus.

Many researchers and investigators have concluded from their researches that there is no correlation found between the bond strength obtained and the tag length. • Method of bond strength testing

Bond failure sites were characterized using the ARI. When the tooth surfaces were analysed there was a significant difference between the bond failure patterns between the two groups. There was the maximum frequency of 5 in conventional groups and the self-etched primer showed the frequency of 3–4, i.e., majority of the samples in SEP failed at the bracket adhesive interface were as in conventional group failed at the enamel adhesive interface. Previous studies and researches showed the amount of residual adhesive on the teeth with the use of self-etching primer was inconsistent. Some studies found more residual adhesive on the enamel with self-etching primer than with conventional phosphoric acid etching, whereas other reported significantly less.[12],[13],[14]

However, clinicians should remember that this was an in vitro study and the results may not necessarily be the same as those that would be obtained in the oral environment. It has been suggested that bond strength of between 5.8 MPa and 7.8 MPa is more than sufficient for successful bonding for orthodontic purposes. In the clinical situation, it is more important to obtain adequate bond strength during orthodontic treatment for safe debonding rather than to attain the greatest possible bond strength.


   Summary and Conclusion Top


The research work done here showed that the bond strength of SEPs and conventional bonding process are comparable with mean and standard deviations of 9.38 and 6.02 MPa for conventional bonding process and 6.91 ± 3.58MPa for self-etch bonding process. The bond strength of SEP is comparatively lesser than the conventional acid etching techniquebut is definitely more or less to the required bond strength to resist masticatory forces. Since the bond strength of SEP is less as compared to the conventional phosphoric acid etch technique the use of SEP in bonding brackets cannot be ignored, the use of self-etching primer can be recommended as an alternative method for bonding orthodontic brackets. Majority of the studies conducted on self-etching primer are in vitro studies. Results of these cannot be extrapolated to the intraoral environment. Hence, further long-term clinical studies need to be carried out before actually recommending the use of Self-Etching primer in routine orthodontic bonding.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Buonocore MG. A Simple method of increasing the adhesion of acrylic filling materials to enamel surface. J Dent Res 1955;34:849-53.  Back to cited text no. 1
    
2.
Newman GV. Epoxy adhesives for orthodontic attachments: Progress report. Am J Orthod 1965;51:901-12.  Back to cited text no. 2
    
3.
Saito K, Sirirungrojying S, Meguro D, Hayakawa T, Kasai K. Bonding durability of using self-etching primer with 4-META/MMA-TBB resin cement to bond orthodontic brackets. Angle Orthod 2005;75:260-5.  Back to cited text no. 3
    
4.
Daniel M, David W. Enamel loss due to orthodontic bonding with filled and unfilled resin using various clean up techniques. Am J Orthod 1980;77:307-19.  Back to cited text no. 4
    
5.
Lehman R, Davidson CL. Loss of surface enamel after acid etching procedures and its relation to fluoride content. Am J Orthod 1981;80:73-82.  Back to cited text no. 5
    
6.
Bishara SE, Gordan VV, VonWald L, Jakobsen JR. Shear bond strength of composite, glass ionomer, and acidic primer adhesive systems. Am J Orthod Dentofacial Orthop 1999;115:24-8.  Back to cited text no. 6
    
7.
Ireland AJ, Knight H, Sherriff M. An in vivo investigation into bond failure rates with a new self-etching primer system. Am J Orthod Dentofacial Orthop 2003;124:323-6.  Back to cited text no. 7
    
8.
Buyukyilmaz T, Usumez S, Karaman AI. Effect of self-etching primers on bond strength – Are they reliable? Angle Orthod 2003;73:64-70.  Back to cited text no. 8
    
9.
Diedrich P. Enamel alteration from bracket bonding and debonding: An SEM study. Am J Orthod 1981;79:501-22.  Back to cited text no. 9
    
10.
Mao J, Qi J. Effect of saliva contamination on shear bond strength of orthodontic brackets when using a self-etch primer. J Huazhong Univ Sci Technolog Med Sci 2005;25:111-2.  Back to cited text no. 10
    
11.
Bergeron C, Vargas MA, Gelinas P, Van M. Bond Strength of self etching adhesives to enamel. JDR 2000;79:2386.  Back to cited text no. 11
    
12.
Bishara SE, Vonvald L, Laffoon JF, Warren JJ. Effect of self-etching primer/adhesive on the shear bond strength of orthodontic brackets. Am J Orthod 2001;119:621-4.  Back to cited text no. 12
    
13.
Fritz UB, Diedrich P, Finger WJ. Self-etching primer an alternative to the conventional acid etch technique. J Orofac Orthop 2001;62:238-45.  Back to cited text no. 13
    
14.
Hitmi L, Attal JP, Degrange M. Evaluation of acidic adhesive for orthodontic bonding J D Res 2000;79:507.  Back to cited text no. 14
    
15.
Cacciafesta V, Sfondrini MF, Baluga L, Scribante A, Klersy C. Use of a self-etching Primer in combination wit a resin modified glass ionomer: Effect of water and saliva contamination on shear bond strength. Am J Orthod Dentofacial Orthop 2003;124:420.  Back to cited text no. 15
    
16.
Dorminey JC, Dunn WJ, Taloumis LJ. Shear bond strength of orthodontic brackets bonded with a modified 1-step etchant-and-primer technique. Am J Orthod Dentofacial Orthop 2003;124:410-3.  Back to cited text no. 16
    
17.
Dorminey JC, Dunn WJ, Taloumis LJ. Shear bond strength of orthodontic brackets bonded with a modified 1-step etchant-and-primer technique. Am J Orthod Dentofacial Orthop 2003;124:410-3.  Back to cited text no. 17
    
18.
Hannig M, Reinhardt KJ, Bott B. Self-etching primer vs phosphoric acid: An alternative concept for composite-to-enamel bonding. Oper Dent 1999;24:172-80  Back to cited text no. 18
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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