ABSTRACT
Introduction:
Numerous manufacturers have improved bracket retention systems as a result of the frequent bond failure that occurs during orthodontic treatment. One of the elements affecting the adhesive’s bond strength is the bracket retention mechanism.
Objectives:
This study’s objective was to assess how various bracket base retention characters affected shear bond strength.
Materials and Methods:
Four distinct base features for brackets were evaluated. The basic design was examined using a scanning electron microscope. On the Universal testing equipment, brackets were glued to human teeth and then released.
Results:
The findings indicate that the polymer-coated base’s overall mean SBS, which had a mean value of 21.64 ± 4.14 MPa, was considerably greater than that of the other brackets (P 0.05). The foil meshpad, photochemically etched base, and laser-structured base had mean SBS values of 15.12 ± 5.75 MPa, 16.86 ± 3.76 MPa, and 19.32 ± 4.23MPa, respectively.
Conclusions:
Following laser-structured base and photochemically etched base brackets in terms of shear bond strength were polymer-coated base brackets. The shear bond strength was the lowest in the plain foil mesh pads.
KEYWORDS: Bonding, bracket base design, polymer-coated base, shear bond strength
INTRODUCTION
Numerous manufacturers have improved bracket retention systems as a result of the frequent bond failure that occurs during orthodontic treatment. One of the elements affecting the adhesive’s bond strength is the bracket retention mechanism. Through a variety of mechanical, chemical, or combined techniques, we can improve the bracket base retention.[1] The ideal bond strength for orthodontic brackets is between 5.9 and 7.8 mega-Pascals (MPa), in order to be considered clinically successful.[2]
Shear and tensile bond strengths are the two basic tests that can be used to gauge and assess the strength of orthodontic adhesives. In a shear bond strength test, the force is delivered parallel to the long axis of the tooth and as close as practical to the bracket–tooth interface.[3]
This study was conducted to ascertain which base type has the highest success rate and to assess the impact of various bracket base types on shear bond strength.
MATERIALS AND METHOD
One hundred removed human premolar teeth that were healthy and had undamaged buccal tooth surfaces were used in this research. To avoid dehydration and bacterial growth, the extracted teeth were cleaned, rinsed, debrided, and kept in a solution containing 0.1% (wt/vol) thymol.
Twenty orthodontic brackets with various bracket retention systems were picked for analysis. Self-curing acrylic resin was used to create the acrylic blocks required to install teeth. These acrylic blocks were made with a stainless steel mould. The roots of each tooth were inserted into the mould, which was filled with self-curing acrylic, up to 2–3 mm apical to the cemento-enamel junction. Crowns were left visible to make gluing brackets to the buccal surface easier. The entire sample was separated into four groups {Group I [laser-structured Nu Edge (TP Orthodontics) base], II [the Mini Diagonali (Leone) base], III [Minimaster (American Orthodontics) base], and IV [the polymer-coated Nu Edge (TP Orthodontics) base)]}, each of which contained 20 samples, depending on the type of bracket base.
Green was used to indicate the group I acrylic blocks. The yellow color was used to identify the acrylic blocks in group II. The acrylic blocks with red are a part of group III. Those acrylic blocks with brown are a part of group IV.
The bonding process was carried out in conformity with the manufacturer’s protocol. An Instron Universal Testing Machine was used for the test to determine the binding strength. The Instron Universal Testing Machine’s long axis of the tooth was parallel to the direction of the load placement as the prepared acrylic blocks were placed inside. Additionally, the load was applied using a custom-made knife-edged rod in a gingivo-occlusal direction. The cross head speed of the Instron Universal Testing Machine was set to 1 mm per minute, and the load side density was set to 0–50 kg.
The obtained data were evaluated using analysis of variance (ANOVA) and Tukey’s test with SPSS software version 21.0.
RESULT
ANOVA of the groups’ effects on SBS showed a significant impact of groups (F = 4.376, P 0.001*) [Table 1]. Shear bond strength was used to compare groups across, and the results are displayed in association of the mean SBS between groups revealed significant results [Table 2].
Table 1.
Various groups’ MPA shear bond strengths
| Group | Mean±Sd | F value | p |
|---|---|---|---|
| I | 21.64±4.14 | ||
| II | 15.12±5.75 | 4.376 | 0.001* |
| III | 16.86±3.76 | ||
| IV | 19.32±4.23 |
Table 2.
Comparisons between groups based on the strength of shear bonds in different groupings
| Comparison | Mean variation | p |
|---|---|---|
| I vs II | 6.52 | 0.001** |
| I vs III | 4.78 | 0.034** |
| I vs IV | 2.32 | 0.785* |
| II vs III | -1.74 | 0.012** |
| II vs IV | -4.2 | 0.001** |
| III vs IV | -2.46 | 0.012** |
**significant, *non-significant
DISCUSSION
All the groups in the current study had SBS mean values that were optimum. The brackets with polymer-coated bases had the maximum average shear bond strengths, intimately subsequently those with laser-structured bases. In contrast, the mean shear bond strengths of brackets with photochemically etched bases and foil mesh pads were noticeably lower.
According to the study by MacColl et al.,[4] the SBS of a base that had been photochemically etched was higher than that of foil-meshed brackets. Chaudhary GH et al.[5] 12 also presented comparable findings. Fleishmann et al.[6] showed that the metallic bracket with laser retentions had the maximum average adhesion force, despite the fact that there were no considerable variations among the brackets that were checked. Goyal et al.’s[7] analysis observed that the mean shear bond strength was the lowest for mini Diagonali brackets.
CONCLUSION
All four types of brackets examined in this study had shear bond strengths that were significantly higher than the typical clinically acceptable values, allowing for their safe application in clinical settings. The shear bond strength was the lowest in the plain foil mesh pads.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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