ABSTRACT
Background:
The strength of the connection between orthodontic brackets and the enamel is a major factor in the outcome of orthodontic therapy. Bonding methods have changed a lot, and self-etching primers are becoming more and more common because of their easy process.
Materials and Methods:
Two sets of 40 removed human premolars (n = 20) were randomly assigned. Group B used a self-etching adhesive system, while Group A used a traditional adhesive method that included acid etching using 37% phosphoric acid. A consistent bonding approach was used to attach brackets to every sample, and thermocycling (500 cycles between 5°C and 55°C) was then performed. A universal testing machine was used to test the shear bond strength (SBS) at a crosshead speed of 1 mm/min. Using a stereomicroscope, the adhesive remnant index (ARI) was assessed.
Results:
Group B (self-etching adhesive) had a mean SBS of 12.7 ± 1.8 MPa, while Group A (traditional adhesive) had a mean SBS of 15.2 ± 2.1 MPa. There was a statistically significant change (P < 0.05). Group A exhibited more enamel retention than Group B, according to ARI ratings. Both adhesives, however, offered sufficient SBS for clinical use.
Conclusion:
Self-etching adhesives provided sufficient bond strength for orthodontic applications with the benefit of a streamlined bonding process, while traditional adhesives demonstrated better SBS. Clinical effectiveness and patient requirements should be taken into account while choosing between these systems.
KEYWORDS: Adhesive remnant index, conventional adhesive, enamel bonding, orthodontic brackets, self-etching adhesive, Shear bond strength
INTRODUCTION
An essential component of orthodontic therapy is the bonding of orthodontic brackets to the enamel, which guarantees the brackets’ stability over the course of treatment. Good adhesion decreases the chairside time for rebonding operations, improves treatment efficiency, and minimizes bracket failure.[1,2] The gold standard for preparing the enamel prior to applying an adhesive has historically been the acid-etching method utilizing phosphoric acid. By producing microporosities in the enamel, this traditional technique gives the adhesive a robust mechanical interlock.[3] However, the process’s multistep structure may be technique-sensitive and time-consuming.[4]
Self-etching adhesives have grown in favor recently as a more straightforward substitute for traditional bonding techniques. By removing the need for distinct etching and washing procedures, self-etching primers cut down on chairside time and the possibility of mistakes brought on by excessive etching or insufficient rinsing.[5] These adhesives provide a more user-friendly method by combining priming and etching into a single process.[6] Notwithstanding these benefits, questions still surround their capacity to provide a bond strength that is on par with traditional adhesives, especially when orthodontic pressures are applied.[7]
Self-etching adhesive bond strength has been assessed in a number of tests, with varying degrees of success. While some studies indicate that self-etching systems provide sufficient bond strength for orthodontic applications, other studies show much lower values when compared to traditional systems.[8,9]
MATERIALS AND METHODS
Forty excised human premolars, devoid of fractures and cavities, were gathered and preserved in distilled water at ambient temperature until used. The teeth were meticulously cleaned with a scaler to eliminate dirt and polished with nonfluoridated pumice for 10 seconds. The crowns were then encased in acrylic resin blocks, with the crowns remaining exposed for bonding processes.
Division of groups
The teeth were arbitrarily allocated into two groups (n = 20):
Group A: Traditional adhesive method
Group B: Self-etching adhesive system.
In Group A, the enamel was subjected to etching with 37% phosphoric acid for 15 seconds, followed by a thorough rinsing with water for 10 seconds and then air drying until a frosty aspect was evident. A primer was used, followed by the adhesive, and brackets were affixed using light-cured composite resin.
In Group B, a self-etching primer was immediately put to the enamel for 20 seconds, without any preparatory etching or washing. The adhesive was then applied, and brackets were affixed using the same light-cured composite resin as Group A.
Standardized stainless-steel orthodontic brackets were used in both groups, and a consistent load of 300 g was given to guarantee correct seating throughout the bonding procedure. The surplus glue around the brackets was eliminated prior to hardening. All specimens were polymerized for 20 seconds with an LED curing lamp.
Subsequent to bonding, all specimens were subjected to thermocycling for 500 cycles between 5°C and 55°C, with a dwell period of 30 seconds in each temperature bath, to replicate oral conditions.
The shear bond strength (SBS) of the adhered brackets was evaluated utilizing a universal testing apparatus. A chisel-shaped blade was used at the bracket–enamel interface at a crosshead speed of 1 mm/min until the bracket debonded. The SBS values were documented in megapascals (MPa).
The adhesive residues on the enamel surface were assessed using a stereomicroscope at 10x magnification upon debonding. The ARI ratings were determined according to the proportion of adhesive retained on the tooth surface.
The SBS values were evaluated by an independent t-test to compare the binding strength between the two groups. The ARI scores were evaluated by the Chi-square test. A P value less than 0.05 was deemed statistically significant.
RESULTS
Shear bond strength
The mean SBS values for the two groups are presented in Table 1. Group A (conventional adhesive system) demonstrated a higher mean SBS of 15.2 ± 2.1 MPa compared to Group B (self-etching adhesive system), which exhibited a mean SBS of 12.7 ± 1.8 MPa. The difference was statistically significant (P < 0.05), indicating superior bond strength for the conventional adhesive system.
Table 1.
SBS of bonded brackets
| Group | Mean SBS (MPa) | Standard Deviation | P |
|---|---|---|---|
| Group A (Conventional) | 15.2 | ±2.1 | <0.05 |
| Group B (Self-etching) | 12.7 | ±1.8 |
Adhesive remnant index
The distribution of ARI scores is shown in Table 2. Group A had a higher proportion of teeth with ARI scores indicating more adhesive retention on the enamel surface (score 3). In contrast, Group B showed a greater frequency of lower ARI scores, indicating less adhesive retention. The differences in ARI score distribution between the two groups were statistically significant (P < 0.05).
Table 2.
ARI scores
| ARI Score | Description | Group A (n=20) | Group B (n=20) |
|---|---|---|---|
| 0 | No adhesive left on enamel | 2 | 6 |
| 1 | <50% adhesive left on enamel | 4 | 7 |
| 2 | >50% adhesive left on enamel | 5 | 4 |
| 3 | All adhesive left on enamel | 9 | 3 |
In-text citations
The results clearly demonstrate that the conventional adhesive system achieved significantly higher SBS values compared to the self-etching system [Table 1]. Additionally, the ARI score distribution highlights that Group A exhibited greater adhesive retention on the enamel, while Group B displayed more adhesive failure at the bracket interface [Table 2].
DISCUSSION
The SBS of orthodontic brackets bonded using self-etching adhesives and traditional adhesives was examined in the present investigation. The results showed that brackets attached using the self-etching adhesive system had a much lower SBS than brackets bonded using the traditional adhesive technique. These findings are consistent with earlier research showing that a more robust enamel–adhesive contact is produced by the multistep etching process in traditional systems, leading to a better bond strength.[1,2]
According to Reynolds,[3] the clinically acceptable threshold of 6–8 MPa was surpassed by the mean SBS for the traditional adhesive group, which was 15.2 ± 2.1 MPa. This illustrates how dependable it is for orthodontic uses. The self-etching adhesive group nonetheless fulfilled the minimal criteria for clinical usage, while exhibiting a somewhat reduced binding strength (12.7 ± 1.8 MPa). These results are in line with other studies that show that self-etching primers may not reach bond strength comparable to traditional etching methods, even if they are convenient.[4,5,6]
The decreased SBS seen with self-etching adhesives may be due in part to their diminished capacity to sufficiently etch the enamel. Micromechanical retention is limited by the more shallow etch pattern produced by self-etching primers as opposed to phosphoric acid.[7,8] Furthermore, self-etching adhesives’ hydrophilic ingredients may hasten adhesive deterioration, particularly in damp conditions.[9]
CONCLUSION
In order to increase the etching capability and bond endurance of self-etching adhesives, future research should concentrate on improving their composition. Long-term clinical studies are also required to assess how well these systems function in real-world scenarios, such as when exposed to environmental influences and oral pressures.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
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