Effect of orthodontic adhesive thickness on force required by debonding pliers

Evaluation of orthodontists' attitudes and practices regarding residual resin removal methods

INTRODUCTION

The removal of residual resins is a routine procedure in orthodontic clinics and of great importance to the final result of the treatment.

OBJECTIVE

To evaluate the main methods of residual resin removal used by orthodontists, and the main reasons for choosing these methods.

METHODS

A questionnaire consisting of 21 questions: 6 relating to demographic data and the other 15 relating to two methods used to remove residual resins (drills or pliers) was sent by e-mail to orthodontists registered with the Regional Councils of Dentistry of São Paulo and Rio de Janeiro (Brazil) within April and June, 2023. Questionnaires were sent back by 153 professionals.

RESULTS

Residual resin removal is always carried out with high speed drill for 44.7% of the sample, and with low speed drill for 28.7%; 61.3% use irrigation. The multi-laminate carbide bur is used by 82.5% of orthodontists. Pliers are always used by 12.4%. Resin-removing pliers with Widia are used in 39% of cases. The use of high speed was justified by the shorter working time, and the choice of pliers was justified by the smaller damage to the tooth enamel.

CONCLUSION

The most used residual resin removal method was the multi-laminate carbide bur at high speed with irrigation, justified the by shorter working time.

The Influence of Various Adhesive Systems and Polishing Methods on Enamel Surface Roughness after Debonding of Orthodontic Brackets: A Three-Dimensional In Vitro Evaluation

A slight alteration of the enamel surface is inevitable upon debonding of orthodontic brackets, adhesive removal, and finishing/polishing. The aim of this in vitro study was to compare two adhesives and three polishing methods by measuring enamel surface roughness using confocal laser scanning microscopy (CLSM). Brackets were bonded on 42 extracted human premolars using Transbond XT (Transbond group) or Fuji Ortho (Fuji group). After debracketing, adhesives were removed with a tungsten carbide bur, and surfaces were polished using Sof-Lex discs, a rotary brush with a prophylactic paste (Depural), or a prophylactic cup with two polishing pastes (n = 7 in each subgroup). Surface roughness (S_a, S_ku, S_q, and S_z) was measured using CLSM and compared before treatment (T₁), after debracketing and adhesive removal (T₂), and after polishing (T₃). The data were statistically analyzed using the Mann-Whitney U and Kruskal-Wallis tests with Bonferroni correction. The time required for adhesive removal was measured and compared using a two-sample t-test. Surface roughness at T₂ increased compared to T₁, but the difference was significant only for the Fuji group (p < 0.01). The time required to remove Transbond XT (94.1 ± 6.8 s) was significantly higher compared to Fuji (72.1 ± 5.9 s, p < 0.0001). Polishing with Sof-Lex discs resulted in lower surface roughness compared to T₁ (p = 0.018). Using Depural and polishing pastes showed no significant difference in surface roughness compared to T₁, except for a significant decrease in S_a and S_q for Transbond (p = 0.043) and in S_ku for Fuji (p = 0.018) after polishing with Depural. In conclusion, the removal of Transbond took significantly longer, but there were fewer residues of composite resin on the enamel surface. Sof-Lex discs decreased enamel roughness, whereas enamel morphology and roughness were similar to the pre-treatment state after polishing with polishing pastes.

Antibacterial and Physicochemical Properties of Orthodontic Resin Cement Containing ZnO-Loaded Halloysite Nanotubes

Demineralized white lesions are a common problem when using orthodontic resin cement, which can be prevented with the addition of antibacterial substances. However, the addition of antibacterial substances such as zinc oxide alone may result in the deterioration of the resin cement's functions. Halloysite nanotubes (HNTs) are known to be biocompatible without adversely affecting the mechanical properties of the material while having the ability to load different substances. The purpose of this study was to prepare orthodontic resin cement containing HNT fillers loaded with ZnO (ZnO/HNTs) and to investigate its mechanical, physical, chemical, and antibacterial properties. A group without filler was used as a control. Three groups containing 5 wt.% of HNTs, ZnO, and ZnO/HNTs were prepared. TEM and EDS measurements were carried out to confirm the morphological structure of the HNTs and the successful loading of ZnO onto the HNTs. The mechanical, physical, chemical, and antibacterial properties of the prepared orthodontic resin cement were considered. The ZnO group had high flexural strength and water absorption but a low depth of cure (p < 0.05). The ZnO/HNTs group showed the highest shear bond strength and film thickness (p < 0.05). In the antibacterial test, the ZnO/HNTs group resulted in a significant decrease in the biofilm's metabolic activity compared to the other groups (p < 0.05). ZnO/HNTs did not affect cell viability. In addition, ZnO was cytotoxic at a concentration of 100% in the extract. The nanocomposite developed in this study exhibited antimicrobial activity against S. mutans while maintaining the mechanical, physical, and chemical properties of orthodontic resin cement. Therefore, it has the potential to be used as an orthodontic resin cement that can prevent DWLs.

Effects of adhesive flash-free brackets on debonding pain and time: A randomized split-mouth clinical trial

OBJECTIVES

To evaluate the effects of adhesive precoated (APC) flash-free brackets on the level of pain, amount of remnant adhesive, and removal time during the debonding procedure.

MATERIALS AND METHODS

Thirty patients (20 female, 10 male) aged 12 to 18 years undergoing nonextraction fixed orthodontic treatment were included in this study. APC flash-free and conventional ceramic brackets were bonded with a split-mouth study design. Bracket types were randomly allocated to quadrants. During the removal of the brackets, the visual analogue scale (VAS) was used to assess the level of pain for each tooth. The adhesive remnant index (ARI) was used to determine the amount of adhesive remaining on the tooth surface. Adhesive removal times were calculated per quadrant. The data were analyzed using the Wilcoxon test for comparisons between groups.

RESULTS

Pain scores were generally higher for the conventional group than for the flash-free group. There were no differences in VAS scores across most tooth types during debonding. Overall, ARI results showed more adhesive remnants in the conventional bracket group (P < .001). Except for the right maxillary quadrant, the times required to remove the adhesive were significantly longer for the flash-free brackets than the conventional brackets (P ≤ .005).

CONCLUSIONS

Although removal time was slightly longer for the flash-free adhesive than for the conventional adhesive, lower pain scores were generally observed for the flash-free adhesive brackets during the debonding procedure. Both time and pain differences could be considered clinically insignificant.

Does Pigment Incorporation into Regular Composite Resins for Posterior Buildups Alter Their Bond Strength?

Posterior build-ups are auxiliary devices to orthodontic treatment which are made with resin-based or glass ionomer composites. Their removal requires care to protect the tooth surface, therefore, pigmented materials are preferred for a better visualization. This study proposed a pigmentation experimental technique of a regular composite resin, evaluating the microshear bond strength test (µ-SBT) of this experimental pigmented resin and comparing with a blue-colored polyacid-modified composite resin, used for posterior buildups. Forty-eight buccal and lingual surfaces of human teeth were used and randomly divided into 4 groups (n=12). The groups were divided into: C (control), regular composite resin; P, regular composite resin pigmented; UBL, Ultra Band Lok™; OB, Ortho Bite™. The composites were bonded using a matrix to obtain microcylinders and prepared for each experimental groups. The samples were then stored in distilled water for 24h at 37°C followed by a µ-SBT. The types of bond failures were evaluated using a stereoscopic magnifying glass (10×). The data were analyzed by ANOVA with Fisher post hoc and Dunnett´s test. Means of µ-SBT± standard deviation (MPa) were: C (39.98a±13.0), P (40.09a± 14.3); UBL (33.26ab±8.6); OB (28.70b±5.5). The most prevalent type of failure was adhesive (80.4%). Further, was not observed a statistically significant correlation between the bond strength values and failure patterns. The pigmentation of a commercially available resin did not alter the µ-SBT and exhibited similar adhesiveness as a polyacid-modified composite resin.

Effects of contact compressive force on bracket bond strength and adhesive thickness : Study using orthodontic resins with different viscosities

PURPOSE

To assess the effect of the contact compressive force to seat orthodontic brackets on shear bond strength (SBS) and adhesive thickness using adhesive resins with different viscosities.

METHODS

A total of 184 premolars were divided equally into eight groups of 23. Transbond XT and Beauty Ortho Bond paste viscous self-etching adhesive systems were used with contact compressive forces of 0.5, 1, 2, and 3 N (groups 1-4 and groups 5-8, respectively) via a push-pull tension gauge. SBS and adhesive thickness were measured in each adhesive system for each contact compressive force.

RESULTS

Significant differences existed in the SBSs between the adhesive systems for each contact compressive force and the SBSs were significantly higher in groups 1 (17 MPa) and 2 (16 MPa) than in groups 3 (14 MPa) and 4 (13 MPa). Significant differences existed for the adhesive thickness between the adhesive systems for the three contact compressive forces less than 3 N. The adhesive in group 1 (0.184 mm) was significantly thicker than that in groups 2-4 (from 0.098 to 0.129 mm). In groups 2 (0.129 mm) and 3 (0.121 mm) it was thicker than in group 4 (0.098 mm), and in group 5 (0.119 mm) it was thicker than in groups 6-8 (from 0.087 to 0.088 mm).

CONCLUSIONS

The high-viscosity adhesive Transbond XT exhibited higher SBSs than the low-viscosity Beauty Ortho Bond paste. For the adhesive Transbond XT, lower contact compressive forces produced greater adhesive thicknesses and higher SBSs. For the Beauty Ortho Bond paste, no significant changes in the adhesive thickness or SBS values were observed for contact compressive forces greater than 0.5 N.

[Comparison of adhesive seal morphology between APC™ PLUS and APC™ Flash-Free Adhesive Coated brackets]

INTRODUCTION

Does the new adhesive-coated APC™ Flash-Free bracket from the 3M Unitek^® group simplify the bonding protocol without compromising precision?

OBJECTIVES

The aim of this study was to compare the morphology of the adhesive joint between the classic APC™ PLUS adhesive-coated brackets and APC™ Flash-Free brackets.

MATERIALS AND METHODS

In vitro bonding of esthetic brackets in the CLARITY™ ADVANCED range was performed to compare the morphology of the excess flash between APC™ PLUS and APC™ Flash-Free brackets.

RESULTS

No statistically significant difference was found concerning the morphology of the excess flash between APC™ PLUS and APC™ Flash-Free brackets. A statistically significant difference was found regarding the thickness of the adhesive between the two types of bracket. The adhesive used for the APC™ Flash-Free brackets was significantly thicker than for the APC™ PLUS brackets (P=0.0001). Adhesive thickness was also more homogeneous on the APC™ Flash-Free brackets (P=0.001 for the relative difference).

CONCLUSION

The adhesive is thicker but adhesive homogeneity is greater with APC™ Flash-Free brackets than with APC™ PLUS brackets.

Shear bond strength and debonding characteristics of a new premixed self-etching with a reference total-etch adhesive

Background

To determine the shear bond strength and adhesive remnant index of a new premixed self-etching primer and adhesive (Tectosan, BonaDent, Germany) for orthodontic appliances in comparison to a reference total-etch system Transbond XT.

Methods

Bovine incisors were embedded in resin and randomly divided into two groups of 16 samples each. Brackets (Discovery, Dentaurum, Germany) were bonded in group 1 (total-etch-system, Transbond XT) and in group 2 (self-etch-system, Tectosan) with curing light for 40 s. Shear bonding strengths were measured after 24 h of storage in distilled water at 37 °C with a Zwicki 1120 testing machine (Zwick Roell, Germany). A force was applied on the bracket base at the wings in occluso-gingival direction. Then the adhesive remnant index (ARI) was determined.

Results

No statistical differences on SBS were found for both bonding agents (p = 0.63). ARI scores however differed statistically significantly (p = 0.035): in the total-etch group more adhesive remained on the teeth, whereas in the self-etch group more adhesive remained on the brackets. There were no visible enamel damages in both groups.

Conclusions

No differences in the shear bond strength were found between both bonding agents. In our study the self-etch-system shifted the adhesive remnant index from more adhesive on the teeth to more adhesive on the bracket - as other already published self-etch systems did - with the new benefit of not increased enamel damages. Tectosan might therefore be a promising alternative to adhesive systems.