Do conventional and new-generation multiple ultrasonic applications change the shear bond strength of metal brackets?

Sirin Hatipoglu; Tugçe Paksoy

doi:10.4103/jdrr.jdrr_175_21

ORIGINAL ARTICLE

Year : 2022 | Volume : 9 | Issue : 1 | Page : 29-34

Do conventional and new-generation multiple ultrasonic applications change the shear bond strength of metal brackets?

Sirin Hatipoglu¹, Tugçe Paksoy²
¹ Department of Orthodontics, School of Dentistry, University of Biruni, İstanbul, Turkey
² Department of Periodontology, School of Dentistry, University of Atlas, İstanbul, Turkey

Date of Submission	11-Nov-2021
Date of Acceptance	12-Jul-2021
Date of Web Publication	06-Apr-2022

Correspondence Address:
Sirin Hatipoglu
Department of Orthodontics, School of Dentistry, University of Biruni, Protokol Yolu No: 45, 10. Yil Cd, Zeytinburnu, Istanbul 34010
Turkey

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jdrr.jdrr_175_21

Abstract

Background: The purpose of this study was to compare orthodontic braces' shear bond strength (SBS) before and after conventional and new-generation multiple ultrasonic instrumentations (UIs). Materials and Methods: One hundred and seventy-five extracted human premolars were bracketed and embedded in acrylic molds. Teeth were separated into 7 groups; each group consisted of 25 teeth. All samples were thermocycled 500 times and control group was randomly selected. To the rest of the teeth, UI and vector ultrasonic instrumentation (VUI) were performed, UI1 and VUI1 were separated. Following the second thermocycling, UI and VUI; UI2 and VUI2, and after the third thermocycling, UI and VUI the UI3 and VUI3 were separated. Results: The decreases in the mean SBS of the UI3 and VUI3 were found to be statistically significant compared to the control group's means. There were no statistically significant differences between neither the means of the control group and UI1, UI2, VUI1, VUI2; nor the means of the VUI1-UI1; VUI2-UI2; VUI3-UI3. There was no statistically significant difference among the means of the UI1-UI2-UI3. On the other hand, the VUI3 was found to have the least statistically significant SBS among VUI groups. Conclusions: Our results revealed that multiple UI and VUI applications both reduce the SBS of brackets. Although the reduction with VUI was found to be more than UI, there was no statistically significant difference between the two instrumentations. Both procedures can be used with caution as a multiple cleaning aid for patients undergoing fixed orthodontic treatment.

Keywords: Brackets, instrumentation, tooth, ultrasonic, vector

How to cite this article:
Hatipoglu S, Paksoy T. Do conventional and new-generation multiple ultrasonic applications change the shear bond strength of metal brackets?. J Dent Res Rev 2022;9:29-34

How to cite this URL:
Hatipoglu S, Paksoy T. Do conventional and new-generation multiple ultrasonic applications change the shear bond strength of metal brackets?. J Dent Res Rev [serial online] 2022 [cited 2023 Mar 29];9:29-34. Available from: https://www.jdrr.org/text.asp?2022/9/1/29/342706

Introduction

The presence of the brackets in the mouth creates a retaining surface; food residues can easily accumulate around the brackets, and it is difficult for orthodontic patients to provide mechanical plaque cleaning.^{[1],[2],[3],[4]} Enamel demineralization is caused by plaque buildup over time. With the growth in the depth of the probing pocket and the number of bacteria in the plaque, fixed orthodontic treatment alters the healthy microbial composition of the subgingival plaque to the periodontal pathogenic.^[3] Patients find it challenging to maintain oral hygiene throughout orthodontic treatment with simply a toothbrush, interdental brush, and dental floss. Oral hygiene protocols applicable for patients under orthodontic treatment can be listed as verbal training, home care, professional prophylactic programs (professional cleaning).^[4] Since the patient's self-made oral care is insufficient, orthodontic patients are required to have a professional ultrasonic cleaning every 6 months. During an orthodontic treatment that lasts for an average of 2 years, the patient is ultrasonically cleaned on average three times. During ultrasonic cleaning, the vibrating handpiece has circulated the brackets at regular intervals and for a certain period to clean the accumulated calculus, residues, or plaque. However, it is thought that the vibrations that occur during ultrasonic cleaning, affect the adhesive that binds the brackets to the tooth surface and its shear bond strength (SBS) and may cause unwanted stress on the bracket base area.^[5] Application of unwanted forces on the brackets may cause accidental brackets' breakage. This bracket breakages by increasing the duration of orthodontic treatment, the total payment amount, and the chairside time may create unwanted situations for both the patient and the orthodontist. To prevent the disadvantages of ultrasonic instrumentation (UI) procedures, Dürr (Duerr Dental, Bietigheim-Bissingen, Germany) developed a new generation ultrasonic instrument called Vector in 1999. Traditional ultrasonic systems use tips that oscillate in a linear pattern parallel to the root surface, but vector ultrasonic systems use a different operating principle. In vector systems, an ultrasonic device at a 90° angle to the operating end vibrates a ring-shaped resonant body. In comparison to standard ultrasonic scalers, the working tip movement amplitude (30–35 m) is significantly lower (10–100 m). This structure eliminates the ellipsoid vibration of the tooltip, allowing it to move in a plane parallel to the tooth surface, as opposed to the customary laterally transmitted vibrations of traditional ultrasonic scalers.^[6] With the use of the vector system, it was aimed to remove the minimum amount of root material, but the maximum amount of subgingival calculus, maximum patient comfort, and to achieve ideal treatment results compared to other nonsurgical treatment methods clinically, microbiologically, and histologically. Previous studies have shown already that a single conventional UI affects and reduces the SBS of the brackets.^[5],[7] As a result, the goal of this study was to investigate and compare the impacts of several cleaning processes, including conventional ultrasonic and vector systems, on the SBS of metal brackets, which had never been investigated before. Multiple cleaning treatments diminish the SBS of orthodontic brackets, according to the null hypothesis of this study.

Materials and Methods

Sample size estimation was performed before the study using the G × Power 3.1.9.2 software with a 95% confidence interval (CI). Because of analysis, α of 0.05 and standardized effect size were detected according to previously obtained data (control group = 9.92 ± 2.63; 0° group = 7.16 ± 3.71) in this field, and it was determined that to have an effect size of 0.50 (high degree) and a power of 80%, there should be minimum 18 teeth in each group.^[5] According to sample size estimation, 175 human premolar teeth were used, and 25 teeth were included in each group. Teeth having no cavities, no fillings or restorations, and no cracks or abnormalities of the enamel surface met the inclusion criteria. Before the experiment, the enamel surfaces of the teeth were evaluated, and those that did not satisfy the criteria were excluded from the study. The teeth were washed to remove organic debris and kept in distilled water at 16°C in the refrigerator to prevent degradation of the enamel structure and bacterial colonization.^[8],[9] Research Ethics Committee of Marmara University (protocol no. 2019-264, February 21, 2019) approved the study.

Preparation of acrylic molds

The teeth were removed from the distilled water and embedded into silicon square molds (20 mm × 15 mm × 20 mm) filled with acrylic vertically to the ground-the long axis of the teeth up, exposing 1 mm apical of the cement–enamel junction [Figure 1]. The buccal surfaces of the teeth were polished for 10 s with a micromotor and fluoride-free pumice, then rinsed and dried. The teeth were etched with 37% phosphoric acid, (orthophosphoric acid gel, 3M ESPE, St. Paul, MN, USA) for 15s, bonding (Transbond^TM XT Adhesive, 3M Unitek, Monrovia, CA, USA) was applied, and then all the brackets (Victory Series^TM Low Profile MBT, 3M Unitek, Monrovia, CA, USA) were bonded to the teeth with the same adhesive (Transbond^TM XT Adhesive, 3M Unitek, Monrovia, CA, USA). Light curing of the adhesive was performed for a total of 20s (each side 5s) using the same light curing device (Radii Plus, SDI Dental Limited, Dublin, Ireland). After bonding of the brackets, samples were randomly allocated into 7 groups (Control, UI1, UI2, UI3, vector ultrasonic instrumentation [VUI] 1, VUI2, and VUI3). All samples were maintained in distilled water at room temperature and all teeth were exposed to thermocycling with a thermal cycler (Dentarge ACS 8.2, Analitik Medical and Engineering Co., Gaziantep, Turkey). The samples were immersed in water baths at temperatures between 5°C and 55°C for 500 times. The samples were set to have a waiting time of 30 s and a transfer time of 7 s in each bath. The control group was separated. UI (Woodpecker UDS-A, Guilin Woodpecker Medical Instrument Co., Ltd., Guangxi, China) (8w power, each side of bracket 15s, total 60s)^[8] and VUI (Duerr Dental, Bietigheim-Bissingen, Germany) (8w power, each side of bracket 15s, total 60s) were performed once to the rest of teeth and UI1 and VUI1 groups were separated. Following the second thermocycling, UI and VUI; UI2 and VUI2 groups, and after the third thermocycling, UI and VUI the UI3 and VUI3 were separated. A single experienced and qualified operator (T. P) conducted all UI and VUI processes.

Figure 1: Shear bond strength testing apparatus

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Shear bond strength test

SBS test was performed by a universal test machine (Shimadzu Autograph AGS-X, Japan) at a crosshead speed of 1 mm/min loading on the bracket-tooth interface by using a 0.5 mm thickness blade (60° cut end face, Shimadzu toothed pushrod B, Japan) [Figure 1]. The specimens were placed as their long axis was vertical to the ground and fixed in the mesiodistal and buccolingual direction by using 8 screws (each side 2 screws) to avoid their rotational movement. The force at debonding of the brackets was recorded in Newton (N); thereafter, the results were converted to megapascals by dividing the force value (N) into the bracket base area (mm²).^[5],[7],[10] The bracket surface area was 9.0322 mm² concerning the manufacturer's instructions.

Adhesive remnant index

Adhesive remnant index (ARI) scores of the groups were evaluated and the buccal surfaces of the teeth were analyzed with a camera of a stereomicroscope (SZX10; Olympus) at ×20 magnification. The residual adhesive on the teeth surface was classified using the ARI.^[5],[7],[8] The ARI scores were as follows: 0: no adhesive residue on the tooth, (1): <50% of adhesive remains on the tooth, (2): >50% of adhesive remains on the tooth, and (3): all the adhesive remains on the tooth.

Statistical analysis

Our data were analyzed using IBM Statistical Package for the Social Sciences program version 25.0 (SPSS Inc., Chicago, IL, USA). Descriptive data are presented as n, mean, and standard deviation. As the first step of data analysis, the normal distribution assumption was checked with the Shapiro–Wilk test. Independent Sample t-test was employed for comparison of the means of two independent groups with normal distribution. One-way analysis of variance test was applied to compare the means of three or more independent groups with normal distribution. Bonferroni post hoc test was performed to identify the group or groups that made the difference. Fisher's exact test was utilized to examine the relationship between categorical data.

Results

Shear bond strength test results

A statistically significant difference was noted between the means of the control group and that of the UI3 and VUI3 groups (P < 0.05). The mean SBS of the control group was higher than the means of the UI3 (P = 0.034) and VUI3 groups (P < 0.001). There was no statistically significant difference between the mean of the control group and the means of groups UI1, UI2, VUI1, and VUI2 (P > 0.05) [Table 1].

Table 1: Comparison of control group with ultrasonic instrumentation 1, ultrasonic instrumentation 2, ultrasonic instrumentation 3, vector ultrasonic instrumentation 1, vector ultrasonic instrumentation 2, and vector ultrasonic instrumentation 3 groups

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There was no statistically significant difference between the means of the VUI1 and UI1; VUI2 and UI2; VUI3 and UI3 groups (P > 0.05) [Table 2].

Table 2: Comparison of vector ultrasonic instrumentation 1 and ultrasonic instrumentation 1; vector ultrasonic instrumentation 2 and ultrasonic instrumentation 2; vector ultrasonic instrumentation 3 and ultrasonic instrumentation 3 groups

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A statistically significant difference was found between the means of the UI1, UI2, and UI3 groups (P < 0.05) [Table 3]. Although, there was no statistical significance found among VUI1, VUI2, and VUI3; the VUI3 mean was lower than the VUI1 and VUI2 means.

Table 3: Intragroup comparison of vector ultrasonic instrumentation 1, vector ultrasonic instrumentation 2 and vector ultrasonic instrumentation 3 and ultrasonic instrumentation 1, ultrasonic instrumentation 2 and ultrasonic instrumentation 3 groups

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Adhesive remnant index scores

There was no statistically significant relationship between the groups and ARI scores (P > 0.05) [Table 4] and [Figure 2].

Table 4: Analysis and cross table demonstrating the relationship between adhesive remnant index scores and groups

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Figure 2: Clustered bar count of groups by adhesive remnant index

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Discussion

To overcome the risks of periodontal disease and enamel demineralization, good oral hygiene maintenance is very important, especially for patients undergoing fixed orthodontic treatment.^[1],[11] While it has been shown that ultrasonic cleaning does not cause any change in the SBS values of the resin cement used in composite restorations,^[12] it was reported that single conventional ultrasonic cleaning processes applied around the bracket bases affect and reduce the SBS of conventional metal braces.^[5],[7] This should be taken into consideration, especially in orthodontic patients, when performing professional oral cleaning procedures. We aimed to investigate and compare the effects of multiple cleaning procedures, performed by conventional ultrasonic and vector systems, on the SBS of metal brackets, which have not been investigated before.

We prefer to use extracted human premolars over bovine teeth because the SBS values recorded on bovine teeth may differ somewhat from those reported on human enamel.^[5] Although there was no statistical difference found in the adhesive strength to human and bovine teeth, compared using various cement and composite resins, the main values of bovine teeth were found to be slightly lower than human teeth.^[13]

According to Alessandri Bonetti et al.^[5]'s experiences, during acrylic molding, we paid special attention not to embed the roots of teeth in acrylic resin up to the cementoenamel junction. Thus, allows scaling all four sides: mesial, distal, occlusal, and gingival parts of the bracket bases as Scribante et al.^[7] did in their study.

Alessandri Bonetti et al.^[5] reported a remarkable difference in the mean SBS values among groups. They concluded that a single UI decreases the SBS of brackets. On the other hand, Scribante et al.^[7] found that UI significantly reduced SBS of some lingual brackets (TTR, Idea, and two-dimensional [2D]) when compared with control groups. When compared to their control groups, the vestibular control bracket (victory) and a lingual bracket (STB) exhibited no significant variations in SBS values. They found that appliances with a lower bracket base area (TTR, Idea, and 2D lingual brackets) had significantly lower SBS values after UI, whereas appliances with a higher base surface (victory vestibular brackets and STB lingual braces) were not affected by UI.

Our results were different from Alessandri Bonetti et al.^[5] and similar with Scribante et al.^[7] We found that a single application of UI and VUI does not statistically change the SBS; while multiple UI and VUI applications reduce the SBS of brackets.

Dental materials are subjected to thermal, mechanical, and chemical stresses in the mouth. It is critical to include this criterion in the study design because orthodontic adhesives are frequently exposed to thermal changes in the oral cavity; these temperature differences produce stresses in the adhesive, which can decrease its SBS. The application of thermal cycling was previously reported to make a decrease in SBS values.^{[14],[15],[16]} The thermal cycling was usually conducted between 5°C and 55°C in different numbers of the cycle, such as 500, 1000, 2000, 10,000, and 20,000. Bishara et al.^[17] discovered that 24 h after first bonding, Smartbond cyanoacrylate glue has enough bond strength, but after thermocycling 500 cycles in water between 5°C and 55°C, its strength drops by 80%. The thermal cycle machine, which simulates the alterations of temperature in the oral environment, was not used in the studies of Alessandri Bonetti et al.^[5] and Scribante et al.^[7] In the light of these previously conducted studies which are showing that the thermal changes are decreasing the SBS of braces, we included those thermal changes in our study and did not create a group without thermal cycling.

Our results revealed that multiple UI and VUI applications both reduce the SBS of brackets. Although the reduction with VUI was found to be more than UI, there was no statistically significant difference between the two instrumentations. Although, there was no statistical significance found among U1, UI2, and UI3; the VU3 mean was lower than the VU1 and VU2 means.

When comparing the VUI to the UI, one must consider the VUI's various operating mechanisms, like; vertical oscillations parallel to the root surface, with the working tip's nonelliptical vibration pattern and small vibration amplitude having a minor mechanical effect.^{[18],[19],[20]} Since the VUI unit is designed for nonsurgical periodontal therapy, it should remove the highest amount of subgingival calculus while removing the least amount of root substance.^[18]

Kishida et al. examined the effects of the vector scaler, a traditional ultrasonic scaler, and a manual scaler in vitro.^[21] They demonstrated that the vector scaler permitted scaling and root planing with minimum root surface damage and tight fibroblast attachment.^[21]

However, there are no studies that reveal the effects of VUI on supragingival scaling in the literature. Vector^TM instrumentation is especially recommended for periodontal maintenance therapy because it is more acceptable for the patient and results in less cementum removal.^[22],[23]

In studies, the VUI has been shown to provide clinical and microbiological periodontal healing results that are comparable to scaling and root planning and UI in moderately deep pockets, and it can be used as a gentle root debridement device for supportive periodontal therapy as an alternative to other UI.^[18],[23]

Our findings also revealed that VUI and UI have similar effects on supragingival scaling in patients having fixed orthodontic treatment.

Finally, estimated ARI scores in this investigation revealed no significant effect of multiple UI and VUI on ARI scores, as a prior study by Alessandri Bonetti et al.^[5] and Scribante et al.^[7]

Limitations of the study were the lack of reproduction of the mechanical and chemical stresses in the mouth that could subsequently affect the SBS of braces and the questionability of the standardization of force application during cleaning even though a single operator performed the cleaning.

Conclusions

Our hypothesis that Multiple UI and VUI applications were found to reduce SBS of brackets, was excepted
Both procedures can be used with caution as a multiple cleaning aid for patients undergoing fixed orthodontic treatment
VUI applications reduce the SBS more than UI applications do
The number of applications and the type of instrumentation do not affect the ARI score.

Ethical clearance

Research was ethically approved by Ethics Committee of Marmara University (protocol no. 2019- 264, 21/02/2019).

Acknowledgments

We thank Ünaldı Medical (Dürr Dental Turkey Supplier) for supplying the Vector Ultrasonic Device and to Alpay Dental Market for supplying the Woodpecker Ultrasonic Device. The Scientific Project Unit of the University of Beykent financially supported this research (Project No: 2018-19-BAP-09).

Financial support and sponsorship

The Scientific Project Unit of the University of Beykent financially supported this research (Project No: 2018-19-BAP-09).

Conflicts of interest

There are no conflicts of interest.

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