|Year : 2016 | Volume
| Issue : 4 | Page : 133-136
Effect of Bracket Base Sandblasting on Bonding of Orthodontic Brackets on Enamel Surface
Mohammad Farahani1, Sattar Kabiri2, Saeed Reza Motamedian1, Mona Hajighadimi1
1 Department of Orthodontic, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran
2 Dental Research Center, Research Institute of Dental Sciences, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran
|Date of Web Publication||21-Dec-2016|
Dental School, Shahid Beheshti University of Medical Sciences, Tehran
Source of Support: None, Conflict of Interest: None
Introduction: In evaluating bond failure, considerable attention has been paid to the various factors that affect bond strength. The bracket–resin interface is the site of usual bond failure. Therefore, many efforts have been accomplished on this interface. The aim of this study was to compare the effects of sandblasting on shear bond strength of three different metal brackets. Materials and Methods: For this experimental study, 180 human maxillary first and second premolars teeth were cleaned and stored in 0.1% thymol solution. The teeth were randomly assigned to either the control (n = 90) or experimental group (n = 90). Each group was subdivided into three equal groups (n = 30). In the control group, three different non-sandblasted metal brackets (American Orthodontics, Dentarum, and 3M Unitek) were bonded with 3M (Unitek) no-mix resin. In the next stage of the experiment, similar brackets were sandblasted and bonded. All samples were pumiced and etched with 37% phosphoric acid for 15 s. The teeth were embedded in blocks of autopolymerization polymethyl methacrylate, utilizing a special device to make their slots parallel to the horizontal. Samples were stored in distilled water for 24 h before testing. Shear bond testing was carried out with UTM Instron machine. Results: Mean shear bond strength of untreated groups was 15.51, 16.60, and 18.58 MPa for American Orthodontics, Dentarum, and 3M Unitek brackets, respectively. Mean shear bond strength of sandblasted brackets was 15.8, 19.36, and 18.66 for American Orthodontics, Dentarum, and 3M Unitek brackets, respectively. Conclusion: This study showed that there was a significant difference in the mean shear bond strength between untreated and sandblasted specimens only in the Dentarum bracket groups.
Keywords: Air-abrasion, sandblasting, shear bond strength
|How to cite this article:|
Farahani M, Kabiri S, Motamedian SR, Hajighadimi M. Effect of Bracket Base Sandblasting on Bonding of Orthodontic Brackets on Enamel Surface. Dent Hypotheses 2016;7:133-6
|How to cite this URL:|
Farahani M, Kabiri S, Motamedian SR, Hajighadimi M. Effect of Bracket Base Sandblasting on Bonding of Orthodontic Brackets on Enamel Surface. Dent Hypotheses [serial online] 2016 [cited 2017 Feb 21];7:133-6. Available from: http://www.dentalhypotheses.com/text.asp?2016/7/4/133/195970
| Introduction|| |
Fixed orthodontic treatments include brackets bonding to the teeth surface for a long period of time. Any failure in bracket bonding during the period of treatment may lead to delay in treatment, patient discomfort, and excessive cost.
Many authors have studied the factors affecting the bracket bond strength and concluded that these factors are enamel surface preparation techniques, adhesive systems, and bracket-related factors such as bracket base properties., Some studies have evaluated the bracket-base related factors on bond strength.,,,
Because most bracket bases are mechanically bond to the teeth surface, efforts have been made to improve the mechanical retention of bracket bases.,, Various designs have been introduced and several techniques have been applied to improve the retention of bracket bases such as sandblasting.,, In theory, sandblasting removes contaminants and improves surface roughness. With these actions, surface energy and available area for bonding has been increased. In some studies, authors utilized sandblasting to enhance retention of bands. Millet et al. showed that sandblasting of bracket base improved bond strength of glass inomer samples to clinically acceptable level. Another study demonstrated that sandblasting lowers lingual retainer wires before bonding increased bond strength. Many studies have reported that sandblasted bracket bases have significantly reduced bond failure ratio in comparison with the non-sandblasted specimens.,,
The aim of this study was to compare the effects of sandblasting of bracket base on shear bond strength (SBS) in three different brackets.
| Materials and Methods|| |
The specimens for this in vitro experimental study comprised 180 human maxillary first and second premolar teeth that were extracted for orthodontic purposes. The teeth had sound buccal surface without any cracks, caries, and restorations. After extraction, residue tissue on the root surfaces was removed and washed away with water. Thereafter, they were stored in 0.1% thymol solution at room temperature to prevent bacterial growth and dehydration.
Considering a Type I error of 0.05 and Type II error of 0.2 (power of 80%), the sample size was calculated to be 30 specimens in each group (a total of 180).
The teeth were randomly assigned to the control (n = 90) or experimental group (n = 90). Each group was subdivided into three equal groups (n = 30). The three types of premolar brackets utilized in this study were as follows:
- Master series metal bracket (American Orthodontics, Sheboygan, WI, USA)
- Gemini seriesTM metal bracket (3M Unitek Corporation, Monrovia, CA, USA)
- Discovery metal bracket brackets (Dentaurum, Ispringen, Germany)
Before the bonding procedure, the enamel surface was polished with oil and fluoride-free fine pumice, using a rubber cap and a slow-speed hand piece, and was rinsed again with tap water and dried with an air syringe. The specimens were color coded for easy identification. Thereafter, the method specified for each experimental group was followed. Method of bracket bonding in both the groups was the same except, in experimental groups, bracket bases were sandblasted before bonding. For sandblasting procedure, a Danville portable sandblasting unit (Danville Microether llA, San Ranon, USA) was utilized and the bracket bases were blasted for 5 s with 50 μm aluminum oxide abrasive powder with 50 mm aluminum oxide abrasive powder for 5 s. The line pressure was maintained at 90 psi, and the head of the sandblasting hand piece was positioned 10 mm from the bracket base.
The enamel surfaces were etched with 37% phosphoric acid gel for 20 s, rinsed with air-water spray for 15 s, and dried to a chalky-white appearance. Next, the bonding agent was applied and air was sprayed from a 5 cm distance for 10 s to evaporate the solvent. Self-cure composite resin (3M Unitek, USA) was applied to the posterior surface of the bracket in 1 mm thickness, based on the manufacturer’s instructions, and the bracket was placed on the porcelain surface using 150 N load measured by an orthodontic gauge (Dentaurum, Ispringen, Germany). Prior to composite polymerization, the excess composite resin was removed utilizing the sharp tip of an explorer.
To mount, the specimens were embedded in blocks of autopolymerization polymethyl methacrylate (Meliodent, Germany) up to the cementoenamel junction leaving the crown exposed. In this study, we utilized a special device to make bracket slots parallel to the horizontal plane.
All specimens were subjected to thermocycle for 5000 cycles at 5–55°C with 20 s of dwelling time in each water bath and 20 s of transfer time. Thereafter, the specimens were stored in an incubator (Pars Azma, Tehran, Iran) at 37°C and 100% humidity for 24 h.
The SBS of the samples was measured utilizing UTM Instron machine (Zwick Roell Z020, Germany). The load was applied at a crosshead speed of 1 mm/min to the bracket–enamel interface. To apply the load, each specimen was secured to the lower grip of the machine. Load was applied until fracture, which was recorded in Newton (N). To convert the SBS values to Megapascals (MPa), the load in N was divided by the cross-sectional area of the bracket base (m2) provided by the manufacturers (12.4 mm2 for Master series, 11.9 mm2 for Gemini seriesTM, 12.9 mm2 for Discovery).
| Results|| |
In non-sandblasted groups, analysis of variance (ANOVA) and least squares difference (LSD) multiple comparison test were used for statistical analysis to show the differences between each of the two groups. In sandblasted specimens, due to the non-homogeneity of variances, non-parametric tests including Kruskal–Wallis and Mann–Whitney were utilized for statistical analysis. To evaluate each pair of bracket (untreated and sandblasted), Levene and t-test were utilized. Mean SBS of untreated groups was 15.51, 16.60, and 18.58 MPa for American Orthodontics, Dentarum, and 3M Unitek companies, respectively. Mean SBS of sandblasted brackets was 15.8, 19.36, and 18.66 MPa for American Orthodontics, Dentarum, and 3M Unitek companies, respectively [Table 1].
Statistical analysis showed that, in non-sandblasted groups, there were significant differences in terms of mean SBS between each of the two groups (P < 0.05) except the difference between American Orthodontics and Dentarum (P > 0.05). In the sandblasting groups, there were significant differences in mean of SBS between each of the two groups (P < 0.05) except the difference between 3M and Dentarum (P > 0.05).
For comparison of each pair of bracket (untreated and sandblasted), t-test revealed that, in Dentarum groups only, there was significant difference in the mean SBS between untreated and sandblasted specimens.
| Discussion|| |
In the current study, only one type of adhesive was utilized to ensure that any variations in SBS were related to the variations in the bracket base design and the effect of sandblasting. Using an orthodontic gauge during bracket placement ensured that future adhesives for all specimens had the same thickness. Furthermore, to maintain the bonding interface parallel to the blade of UTM Instron machine and to make the bracket slot parallel to the horizontal plane, a special device during mounting of specimens was utilized.
The aim of this study was to evaluate the effect of bracket bases sandblasting on SBS. The results revealed that there was significant difference between the sandblasted and non-sandblasted specimens in Dentarum brackets only, and also revealed that sandblasting in this type of bracket resulted in improvement of SBS.
The minimum SBS needed for successful clinical performance depends on the forces of occlusion. Many authors have demonstrated that optimal SBS for bracket bond to enamel is 6–8 MPa., In this study, all the specimens in both the experimental and controls groups produced SBSs that significantly exceeded these values.
This study revealed that 3M Unitek had the highest mean SBS and American Orthodontics had the lowest mean SBS. Moreover, data revealed that in the non-sandblasted groups, there were significant differences in SBS between each of the two groups, except the difference between American Orthodontics and Dentarum.
In 2003, Sharma-Sayal et al. investigated the effect of metal bracket base design on the SBS to enamel in-vitro and demonstrated the significant effect of different bracket base designs on the SBS values. Bracket base designs in American Orthodontics and Dentarum are almost similar; nevertheless, thicker wires are utilized in Dentarum bracket bases, which leads to higher SBS in Dentarum when compared with American Orthodontics; however, this difference is not significant. In 3M bracket bases, machine cutting tools were utilized, thereby leading to the production of more mechanical undercuts and rough surfaces. Hence, in 3M design, SBS was the highest.
Many studies have reported that sandblasted bracket bases significantly reduce bond failure ratio in comparison with the non-sandblasted specimens, however, in this study, there was significant difference in the mean SBS between untreated and sandblasted specimens in Dentarum groups only.
Newman et al. investigated the sandblasting effect on SBS and showed that this procedure can enhance the SBS. There were some differences between their study and the current study. In their study, sandblasting modality details were not clear, which can result in differences between the results of the studies. Moreover, they used 90 μm aluminum oxide powder, however, in the current study, the powder size was 50 μm.
MacCall et al. tested the effects of sandblasting bracket bases on the SBS and concluded that sandblasting for all base sizes can increase the bond strength. There were some differences between the results of their study and that of this study. Adhesive resin used in their study was different from the one used in the current study. Because particle sizes of adhesives are different, this variability could lead to different amount of adhesive penetration in bracket base porosities, thereby producing different SBSs.
| Conclusion|| |
Within the limitations of this study, the results revealed that bracket base design significantly affects the SBS of brackets to enamel. Results revealed that, from the comparison of each pair of bracket (untreated and sandblasted), there was significant difference in mean SBS between untreated and sandblasted specimens in Dentarum groups only. In untreated groups, 3M brackets, and in sandblasted groups, Dentarum brackets had highest SBS.
Financial support and sponsorship
This Study was financially supported by Shahid Beheshti University of Medical Sciences, Tehran, Iran (P/25/17/MT1786).
Conflicts of interest
There are no conflicts of interest.
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