Comparison of Bond Strength of Metal and Ceramic Brackets with or without Primer.

Background: Bonding is an integral part of orthodontic treatment. Orthodontic bonding could be accomplished without the use of primer, it might be possible to reduce the risk of occupational exposure to primer and will save time. So it is very important to know whether primer is required or not. Aim: The aim of this study is to evaluate and compare the shear bond strength (SBS) of metallic and ceramic brackets bonded with and without primer application and to check for residual adhesive post debonding. Material and Method: A total of 100 extracted human premolar teeth were divided into 2 main groups A and B which were further subdivided into: Group A1 - metallic brackets bonded with primer; Group A2 - ceramic brackets bonded with primer; Group B1 - metallic brackets bonded without primer; group B2 - ceramic brackets bonded without primer. The SBS of these brackets was measured. Result: The SBS of group A2 was significantly higher than the other groups, group A1 was the second highest, group B3 was the third highest and group B4 was the least significant. The adhesive remnant index was lowest on failure of ceramic brackets bonded with primer.
Conclusion: SBS of ceramic brackets bonded without primer is superior to SBS of metallic bracket bonded without primer and metallic brackets bonded with primer was superior than metallic bonded without primer. Copyright:

INTRODUCTION

Bonding is an integral part of orthodontic treatment. It involves etching as primary procedure. Acid etching technique was first introduced by Bounocore for an improved bonding to the tooth structure in 1955.[1] Since then, there has been magnificent progress in direct bonding of orthodontic brackets. Orthodontic bonding has evolved significantly since it was first introduced by Buonocore in the 1950s.[2] Primer may be used as part of the bonding process and with light-cured composite; it is usually unfilled resin. Its primary purpose is enamel surface penetration to improve the effectiveness of the final bond.[3] Nonetheless, there is controversy in the literature regarding the use of primers because differences in the adhesion of orthodontic brackets to enamel with or without previous priming of the enamel surface have not been substantiated.[2]

If orthodontic bonding could be accomplished without the use of primer, it might be possible to reduce the risk of occupational exposure to primer and its unpolymerized components.[2] Another advantage of not applying primer is that it saves a step and therefore saves time. This could be crucial when bonding brackets, because the longer it takes to place the brackets, the greater the possibility of moisture contamination that could result in bond failure.[2] Research has previously been carried out on bonding orthodontic brackets with no primer, with three in-vitro studies demonstrating sufficient bond strengths for bonding orthodontic brackets without primer, when bonding with chemically cured/light-cured composite.[456] In this study, we analyzed the shear bond strength (SBS) of metallic and ceramic brackets bonded with and without primer application.

MATERIALS AND METHOD

Hundred maxillary premolars extracted for orthodontic purpose or due to periodontal involvement with sound buccal surfaces were collected, cleaned thoroughly, and stored in artificial saliva at room temperature. The specimen will be divided into two main groups A, and B which were further subdivided into subgroup A1, A2, B1, and B2 consisting of 25 teeth in each group.

Oral Prophylaxis: All teeth will be polished with pumice and rubber prophylactic cups for 10 s, washed thoroughly with water and dried with oil and moisture-free air spray.

Group A: With primer.

It included 50 teeth which is further subdivided into two subgroups: A1, A2.

Subgroup A1: After etching with 37% phosphoric acid, enamel surface was washed and dried. Apply a single layer of Transbond XT primer, were cured with UV light followed by metal racket bonding using Transbond XT adhesive.

Subgroup A2: Ceramic bracket bonding using Transbond XT adhesive was used.

Oral Prophylaxis: All teeth were polished with pumice and rubber prophylactic cups for 10 sec, washed thoroughly with water, and dried with oil- and moisture-free air spray.

Group B: Without primer.

It included 50 teeth which is further subdivided into two subgroups B1, B2.

Subgroup B1: After etching with 37% phosphoric acid, enamel surface was washed and dried followed by bonding metal brackets using Transbond XT adhesive.

Subgroup B2: Ceramic brackets using Transbond XT adhesive was used.

All teeth were polished with pumice and rubber prophylactic cups for 10 sec, washed thoroughly with water and dried with oil- and moisture-free air spray. In subgroup A1 the metal brackets were bonded using Transbond XT adhesives. Subgroup A2 ceramic bracket bonding using Transbond XT adhesive. In Subgroup A3 metal bracket were bonded without primer. In Subgroup A4 ceramic bracket were bonded without primer. A customized square aluminum block of 50 mm in length and 30 mm in width was selected to which acrylic resin was filled, the tooth is embedded in it. An Instron Universal Testing Machine (3M model number – 33R – 4467, UK) was used to assess the SBS of the brackets.

The bracket base area for metal brackets (Gemini Series, 3M Unitek) is 9.61 mm2 as per information provided by the manufacturer. Pascal's using the formula:

The data were analyzed using the Statistical Package for the Social Sciences Version (SPSS) 17.0 for Windows. The level of statistical significance was set at 95% (P = 0.05) [Table 1].

Table 1

Descriptive statistics

Variable	Groups	Mean	SD	Min	Max	P
Shear bond strength, (Mpa)	Premolar ceramic bracket with primer	20.21	1.95	15.98	24.52	0.00
	Premolar metal bracket with primer	17.11	1.68	14.32	20.22
	Premolar ceramic bracket without primer	13.69	1.04	11.98	15.62
	Premolar metal bracket without primer	10.00	1.12	7.85	12.24

Table 1 shows mean, standard deviation, minimum, and maximum values in both the groups. There was a significant difference in mean value of SBS in both the groups (P<0.05)

ANOVA [Table 2] was used to study the overall variance between groups.

Table 2

Mean difference in SBS in both groups

Dependent Variable	(I) Group	(J) Group	Mean Difference (I–J)	P
Shear bond strength, Mpa	Premolar ceramic bracket with primer	Premolar metal bracket with primer	3.135	0.000
		Premolar ceramic bracket without primer	6.553	0.000
		Premolar metal bracket without primer	10.248	0.000
	Premolar metal bracket with primer	Premolar ceramic bracket without primer	3.418	0.000
		Premolar metal bracket without primer	7.113	0.000
	Premolar ceramic bracket without primer	Premolar metal bracket Without primer	3.694	0.000

Table 3 shows that the mean SBS values were 17.11, 20.21, 13.69, and 10.0 MPa, respectively.

Table 3

Shear bond strength values

Subgroup A1	Subgroup A2	Subgroup B1	Subgroup B2
17.11 MPa	20.21 MPa	13.69 MPa	10.00 MPa

DISCUSSION

Esthetic considerations are of key importance for the patients who undergo orthodontic treatment.[7] One of the major changes of the twentieth century in the field of orthodontics was the successful bonding of the brackets to the teeth replacing the old system of banding. This was made possible by the introduction of the acid-etching technique by Buonocore.[8] G.V. Newman was the first to bond orthodontic brackets to the teeth by means of the acid-etching technique. Since then, efforts are on to find newer and better bonding materials for the future, which could make the bonding procedure convenient for both the operator and the patient.[9]

A good orthodontic bonding agent should have the following criteria – excellent bond strength, adequate working time, should not cause decalcification, and should permit its usage in wet conditions.[9]

Etching and priming are two of the most critical steps where the tooth surface should be kept isolated from all contaminants. Primer may be used as a part of the bonding process and with light cured composite: it is usually an unfilled resin. Its primary purpose is enamel surface penetration to improve the effectiveness of the final bond. According to the previous reports in the literature[101112] its purpose in orthodontic bonding is enhancing the bond strength. During bonding brackets, this would represent a financial saving and a potential time saving by missing a step in the bonding process. Esthetic considerations are of key importance for the patients who undergo orthodontic treatment. Esthetic orthodontic brackets have been developed to meet this demand of the patients. However, at the same time, other material properties such as the bond strength, the structural integrity, the bonding mechanism, etc., have to be considered, to meet the clinical requirements.[7]

The SBS of ceramic brackets bonded with primer was the maximum and the adhesive remnant index was the least of ceramic brackets. Ceramic brackets have high bond strength, they are more difficult to deform and have a higher tensile strength. The high bond strength results from silanization of the bracket base, and mechanical retention of both.

Farhan Bazargania[2] compared lingual retainer bonded with and without primer. The result concluded a higher failure rate when bonding lingual retainers without primer group (27%) compared with the primer group (4%). This would represent a financial saving and a potential time saving by missing a step in the bonding process.

This study states that bonding metallic brackets with primer was statistically shown to be inferior to bonding ceramic brackets with primer, SBS of ceramic brackets bonded without primer is superior to the SBS of metallic bracket bonded without primer, bonding ceramic brackets with primer was superior to bonding ceramic brackets without primer and bonding with metallic brackets bonded with primer was superior than metallic brackets bonded without primer.

The superior esthetics of ceramic brackets compared to conventional stainless steel brackets is not only well accepted by the patients, particularly adults, but are also positively sought for ceramic brackets became popular as esthetic appliances and have been available for clinical use for almost 2 decades. Ceramic brackets are durable, allow adequate force control over long treatment periods, and their risk for discoloration is minimal. To conclude ceramic brackets bonded with primer are better than metallic brackets bonded with primer and Ceramic brackets bonded without primer are better than metallic brackets bonded without primer.

CONCLUSION

This study concludes that SBS of ceramic brackets bonded without primer is superior to SBS of metallic bracket bonded without primer. This study also concludes that bonding with metallic brackets bonded with primer was superior than metallic bonded without primer. The adhesive remnant index was the lowest on failure of ceramic brackets bonded with primer followed by metallic brackets bonded with primer followed by ceramic brackets bonded without primer followed by metallic brackets bonded without primer.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.