Effects of enamel sealing on shear bond strength and the adhesive remnant index : Study of three fluoride-releasing adhesives in combination with metal and ceramic brackets

Scanning electron microscopy analysis of metallic and aesthetic bracket meshes before and after debonding

Objective

To study the influence of bracket base meshes on shear bond strength and observe them using a scanning electron microscopy (SEM) before and after debonding.

Methods

Ninety brackets were divided into nine groups of 10 samples each: G1-Alexander, G2-Mini Sprint® Brackets, G3-In-Ovation R CCO, G4-Gemini SL Self-Ligating Bracket, G5-Classic mini 2G Stylus®, G6-Gemini Metal Brackets, G7-ClarityTM Advanced, G8-Crystall-Ize®, and G9-Ceramic Series Flexx 2G®. Groups G1 to G6 and G7 to G9 consisted of metallic and aesthetic brackets, respectively. Initial photographs of all brackets were taken through SEM at 25X magnification. The brackets were then bonded to premolars using TransbondTM XT, and a shear bond strength test was conducted after 24 hours using an Instron machine at 1 mm/min. After debonding, the bracket meshes were observed using SEM.

Results

Before bonding, 72.22% of brackets didn't present mesh defects, while 27.77% did. SEM analysis revealed that G4 and G5 presented defects in 100%, G7 in 40%, and G8 in 10%. The average shear bond strength of 9.67 ± 2.84 MPa and 11.21 ± 4.99 MPa were obtained for both metallic and aesthetic brackets, respectively. A Pairwise-Wilcoxon test with Benjamini-Hochberg correction was conducted to determine specific statistical differences between the groups, revealing significant differences based on bracket type and shear bond strength (P < 0.009).

Conclusions

This study suggested that the shape of bracket meshes influenced shear bond strength.

Effect of torque customization with composite resin bases on the shear bond strength and adhesive remnant patterns of lingual brackets : An in vitro evaluation

PURPOSE

This study evaluated the effect of torque customization of lingual brackets with resin-modified bases on their shear bond strength (SBS), adhesive remnant index (ARI), and bond failure patterns (BFP).

METHODS

The sample comprised 200 lingual lower incisor brackets (DTC® ORG, DTC Medical Apparatus, Hangzhou, China); 40 brackets were tested as-received and 4 groups with 40 brackets each were customized for -10, -20, +10 and +20° torque respectively with light-cured composite resin (Transbond XT™, 3M Unitek, Monrovia, CA, USA) bases. All brackets were bonded to bovine mandibular incisors. Their SBS were estimated in a universal testing machine (INSTRON®, Norwood, MA, USA) with a gingivally directed force applied at the incisal bracket-adhesive interface with 1 mm/min crosshead speed. Their ARI and BFP were evaluated under 20× magnification.

RESULTS

The SBS was 19.9 ± 7.6 MPa for noncustomized brackets, 20.1 ± 9.0 and 18.7 ± 8.2 MPa for brackets with 10 and 20° of negative torque, and 16.6 ± 5.68 and 19.45 ± 5.84 MPa for brackets with 10 and 20° of positive torque, respectively. The differences were not statistically significant (p = 0.097). Teeth with the -20° brackets exhibited higher median ARI scores than noncustomized brackets (1.5 vs 2, p = 0.018). Adhesive-cohesive bond failure with nearly axial split was more frequent in noncustomized brackets than customized ones, the reverse being true for adhesive-cohesive failure with nearly vertical split (p < 0.05). Truly cohesive bond failures were seen only in brackets with positive torque.

CONCLUSIONS

Torque customization with a resin base is an acceptable strategy for metal orthodontic brackets as it does not affect their SBS. However, their BFP differed from noncustomized brackets, depending on the type of torque introduced.

An In-Vitro Analysis of the Surface Treatment of Orthodontic Bracket Bases With Er,Cr:YSGG Laser and Its Effect on Shear Bond Strength

Introduction Shear bond strength is indispensable to prevent the debonding of orthodontic brackets. Lasers have been proven to alter the bond strength of orthodontic brackets, but their efficiency has not been validated in many trials. The study aimed to evaluate the impact of the Er,Cr:YSGG laser on the bases of orthodontic brackets and determine their bond strength with the enamel surface. Materials and methods The Waterlase iPlus (made in the USA in 2012), comprising an Er,Cr:YSGG laser, was used. Based on the surface treatment of brackets, two groups were assigned (n=10), comprising laser-treated and untreated bracket bases. The brackets were treated with the minimum laser intensity (50 Hz, 4.5 W). Then, the brackets of both groups were attached to the labial surfaces of previously extracted premolars, respectively. The shear bond strength of brackets (SBS) was assessed using the universal testing device, and the Adhesive Remnant Index (ARI) was also measured. An independent sample t-test was used to compare the bond strength between the laser-treated and untreated brackets. Results The mean bond strength of laser-treated and control group brackets was 5 MPa and 8.63 MPa, respectively. The laser-treated brackets showed lower bond strength than the control brackets, but the results were statistically insignificant (p=0.23). The ARI analysis stated that bond failures occurred mostly in the region of the bracket and adhesive interface. Conclusion Laser-etched bracket bases showed lesser shear bond strength than the untreated ones, though the difference was statistically insignificant.

Influence of Individual Bracket Base Design on the Shear Bond Strength of In-Office 3D Printed Brackets-An In Vitro Study

(1) Background: Novel high-performance polymers for medical 3D printing enable in-office manufacturing of fully customized brackets. Previous studies have investigated clinically relevant parameters such as manufacturing precision, torque transmission, and fracture stability. The aim of this study is to evaluate different design options of the bracket base concerning the adhesive bond between the bracket and tooth, measured as the shear bond strength (SBS) and maximum force (F_max) according to DIN 13990. (2) Methods: Three different designs for printed bracket bases were compared with a conventional metal bracket (C). The following configurations were chosen for the base design: Matching of the base to the anatomy of the tooth surface, size of the cross-sectional area corresponding to the control group (C), and a micro- (A) and macro- (B) retentive design of the base surface. In addition, a group with a micro-retentive base (D) matched to the tooth surface and an increased size was studied. The groups were analyzed for SBS, F_max, and adhesive remnant index (ARI). The Kruskal-Wallis test with a post hoc test (Dunn-Bonferroni) and Mann-Whitney U test were used for statistical analysis (significance level: p < 0.05). (3) Results: The values for SBS and F_max were highest in C (SBS: 12.0 ± 3.8 MPa; F_max: 115.7 ± 36.6 N). For the printed brackets, there were significant differences between A and B (A: SBS 8.8 ± 2.3 MPa, F_max 84.7 ± 21.8 N; B: SBS 12.0 ± 2.1 MPa, F_max 106.5 ± 20.7 N). F_max was significantly different for A and D (D: F_max 118.5 ± 22.8 N). The ARI score was highest for A and lowest for C. (4) Conclusions: This study shows that conventional brackets form a more stable bond with the tooth than the 3D-printed brackets. However, for successful clinical use, the shear bond strength of the printed brackets can be increased with a macro-retentive design and/or enlargement of the base.

Formulation and characterization of experimental orthodontic adhesive containing antibacterial dimethacrylate DABCO monomers: An in vitro study

OBJECTIVE

The purpose of the study was to investigate the antibacterial efficacy and mechanical properties of experimental orthodontic adhesives containing newly synthesized antibacterial dimethacrylate monomers with doubly charged 1,4-diazabicyclo[2.2.2]octane (DABCO) group (dication).

METHODS

Experimental orthodontic adhesives were formulated using varying compositions of synthesized antibacterial dimethacrylate monomers containing DABCO dication, C16DC2DMA and BisC11DCDMA, replacing part of the control group, Transbond™XT. The concentrations of monomers tested were 5% C16DC2DMA, 10% C16DC2DMA, 5% BisC11DCDMA, and 10% BisC11DCDMA. The biofilm-inhibition effects of the experimental adhesives against Streptococcus mutans were tested. Brackets were then bonded to extracted human teeth utilizing the experimental adhesives in the bonding protocol. The shear bond strength and modulus of elasticity of the control and experimental groups were tested. The adhesive remnant index scores were recorded.

RESULTS

The experimental adhesives containing 5% or 10% BisC11DCDMA and 10% C16DC2DMA showed significantly lower S. mutans colony forming units (CFU) than the control. Both BisC11DCDMA experimental groups displayed similar mechanical properties as compared to the control, although 10% C16DC2DMA showed a reduction in shear bond strength as compared to the control. For all experimental adhesives, the adhesive remnant index scores were not significantly different compared to the control.

CONCLUSION

BisC11DCDMA is a novel antibacterial dimethacrylate monomer that exhibits the significant ability to inhibit bacterial growth while maintaining acceptable mechanical properties. When incorporated into orthodontic adhesives, this monomer may reduce the occurrence of white spot lesions around brackets in orthodontic patients.

Shear bond strength after using sealant before bonding: a systematic review and meta-analysis of in vitro studies

OBJECTIVES

Decalcification during orthodontic treatment is significantly increased. To prevent this negative impact, new treatments with sealants before bonding brackets are commonly been used. This systematic review discusses current knowledge on shear bond strength when using sealant before bonding.

MATERIALS AND METHODS

A systematic review and meta-analysis were performed to identify studies that address shear bond strength after using a sealant before bonding brackets. The search was carried out using common electronic databases in addition to individual searches. Both screening and study eligibility analysis were performed according to PRISMA and Cochrane Guidelines for systematic reviews. Several terms describing shear bond strength after using a sealant before bonding brackets were searched. Particular attention was paid to bond failure and bracket loss. For the statistical outcome, all results were shown in a forest plot based on standardized mean differences (SMD) with a random-effects model to respect heterogeneity of these studies. To assess the heterogeneity of the different trials, I2-value and the Q-Test were performed.

RESULTS

The initial search identified 416 studies. After a thorough selection process, a total of 15 articles met the inclusion criteria. All 15 articles reported results of in vitro studies. Papers were divided into four subgroups according to their used product: ProSeal, Transbond bonding, the combination of Transbond bonding and ProSeal and Clearfil Protect Bond. The results of this review demonstrate a high heterogeneity of the studies. The SMD of the examined 15 articles show nearly no difference between the control and the intervention groups in shear bond strength (p < 0.0001; OR - 0.12; Cl - 0.47-0.23). Forest plots for comparison of the subgroups depict no difference in shear bond strength as well.

CONCLUSIONS

This meta-analysis concludes that there is no additive benefit for shear bond strength when using sealant before bonding. However, additional randomized controlled studies should be performed to analyze impact of sealants on bonding strength and bracket loss in more detail.

CLINICAL RELEVANCE

Using sealants before orthodontic bonding does not reduce shear bond strength.

Comparison of shear bond strength and ARI of four different adhesive systems used to bond molar tubes: An in vitro study

OBJECTIVE

The purpose of this in vitro study was to determine and compare the shear bond strength and ARI score of one traditional etch-and-rinse adhesive system serving as control, with those of two other all-in-one adhesives but with enamel acid etching preceding their application, and of one new 8th generation all-in-one bonding agent combined with a traditional adhesive used to bond stainless steel buccal tubes to molar teeth.

MATERIAL AND METHODS

Four groups of teeth were formulated according to the adhesive system used to bond the tubes on the molars. Shear bond strength was measured using a universal testing machine (Hounsfield, UK). After debonding, each enamel surface was imaged using Inspex HD l080p Vesa camera (Ash Technologies Ltd., Ireland) to determine the ARI score.

RESULTS

The mean SBSs in MPa for the four groups were respectively: A: 9.640 (±3.69), B: 10.261 (±3.03), C: 9.689 (±2.48), D: 8.412 (±3.02). No statistically significant differences were neither found through one-way ANOVA to exist between the group means (P: 0.715), nor for the ARI score frequence through Chi2 (P: 0.534). Maxcem Elite showed four and G-Premio Bond zero instances of enamel fracture.

CONCLUSIONS

1. SBSs of all adhesives and ARI score distributions did not present any significant differences when used to bond stainless steel molar tubes. 2. All adhesives presented with acceptable shear bond strengths for clinical use. 3. Maxcem Elite under the tested conditions presented the greatest and G-Premio the least number of enamel fractures.

Effect of Fluoride Releasing Bonding Materials on Shear Bond Strength of Orthodontic Brackets

Objective

The aim of the present study was to compare the shear bond strength (SBS) of three different fluoride-releasing bonding agents with a conventional adhesive system.

Methods

Eighty-four extracted human premolar teeth were separated into four groups and embedded in acrylic molds consisting of 21 teeth in each group. Brackets were bonded with Transbond XT in group 1, Clearfil SE Protect Bond in group 2, LED Proseal in group 3, and Opalseal in group 4. After bracket bonding, the teeth were thermocycled 1000 times. SBS test was performed, and Adhesive Remnant Index (ARI) scores of the groups were assessed.

Results

One-way analysis of variance test was used to compare the significant differences between the groups. Chi-square and Fisher's exact tests were used to evaluate ARI scores. The Opalseal group showed the highest bond strength, but there was no statistically significant difference between the groups in SBS values (p=0.067). The results of ARI scores were statistically significant.

Conclusions

All bonding materials used in the study showed clinically sufficient bond strengths.

Effect of Yd:YAG laser irradiation on the shear bond strength of orthodontic metal brackets

Objective:

The purpose of this study was to evaluate the effect of the Yd:YAG laser irradiation on orthodontic bracket base surface. Shear bond strength (SBS) values and sites of the bonding failure interfaces were quantified.

Methods:

Brackets were divided into two groups: OP (One Piece - integral sandblast base) and OPL (One Piece - laser irradiation). The brackets were randomly bonded on an intact enamel surface of 40 bovine incisors. The SBS tests were carry out using a universal test machine. A stereomicroscopy was used to evaluate the adhesive remnant index (ARI), and surface characterization was performed by scanning electron microscopy (SEM). Student’s t-test was used to compare the SBS between the two groups (p< 0.05). Frequencies and chi-square analysis were applied to evaluate the ARI scores.

Results:

OPL group showed higher value (p< 0.001) of SBS than OP group (43.95 MPa and 34.81 MPa, respectively). ARI showed significant difference (p< 0.001) between OPL group (ARI 0 = 100%) and OP group (ARI 0 = 15%). SEM showed a higher affinity between the adhesive and the irradiated laser base surface.

Conclusions:

Yd:YAG laser irradiation on bracket base increased SBS values, showing that bonding failure occurs at the enamel/adhesive interface. Laser-etched bracket base may be used instead of conventional bases in cases where higher adhesion is required, reducing bracket-bonding failure.

In vitro evaluation of a ceramic bracket with a laser-structured base

BACKGROUND

The purpose of this study was the assessment of shear bond strength (SBS), adhesive remnant characteristics, integrity of the enamel, integrity of Discovery Pearl as well as the integrity of Fascination 2 ceramic brackets following SBS testing.

METHODS

Sixty maxillary first premolars were randomly assigned into two groups. These groups were bonded with their respective brackets. The samples underwent thermocycling (1000 cycles), SBS testing and assessment of the residual adhesive. The statistical analyses used were the independent samples t-test, the Weibull analysis and the chi-square test.

RESULTS

The independent samples t-test for the comparison of the mean SBS resulted in significant differences between Fascination 2 (10.50 ± 2.61 MPa) and Pearl (13.01 ± 2.50 MPa) brackets (p = 0.0003). The results of the chi-square test for ARI demonstrated a significant difference (p = 0.000) between the groups. A higher frequency of ARI scores of 2 and 3 for Pearl brackets existed. Enamel damage and bracket fracturing was not observed.

CONCLUSIONS

The mean bond strength value, the adhesive remnant characteristics, the integrity of the enamel and the ceramic brackets as well as the Weibull analyses outcomes were highly encouraging during this in vitro screening. The way is paved for an in vivo investigation with the Pearl ceramic bracket.

A Comparative Study of Shear Bond Strength of Direct Bonding System with and without a Liquid Primer: An In Vitro Study

Background

A primer in dental bonding agents enhances the bond between the adhesive and the tooth by way of deriding the tooth surface of moisture and creating a hydrophobic surface for the adhesive to bond and by facilitating the flow of the adhesive into the etched tooth surface. In the orthodontic context, however, there have been debatable results in the published literature as to how significantly the use of primer affects the bond strength between the bracket and the tooth surface.

Aims

This study aimed to evaluate and compare the shear bond strength of two commercially available direct bonding systems with and without using liquid primer and to record their adhesive remnant index scores.

Settings and Design

A total of 100 natural human teeth, extracted for orthodontic therapies, had been selected as specimens for the study. They were equally divided into four categories. Two commercially available products were used to bond metallic orthodontic brackets to the teeth, both with the use of and without the use of a primer to test the shear bond strengths of the four types of adhesive-tooth complexes created. Shear bond strength was measured using universal testing machine, and Student's t-test was applied for the comparison of the results.

Materials and Methods

A total of 100 extracted human premolar teeth were divided into two groups: Group I and Group II, each of which contained two subgroups (with one subgroup pretreated with a primer and the other, not pretreated with the primer). All the teeth were divided equally among the subgroups and were mounted on color-coded acrylic blocks to aid in identification. Group I was bonded with Transbond XT Light Cure Adhesive (3M Unitek Orthodontic Products, Monrovia, California) and Group II was bonded using Phase II two-paste system (Reliance Orthodontic Products, Itasca, Illinois). The shear bond strength of Transbond XT Light Cure Adhesive used with Transbond XT primer and Phase II orthodontic two-paste system used with liquid primer was compared with that of those used without a liquid primer, respectively. The shear bond strength was evaluated using universal testing machine and the adhesive remnant scores were evaluated subsequently. The Student's t-test was applied for comparison of the two groups.

Statistical Analysis

Descriptive statistics, such as mean, standard deviation, and a standard error, were calculated for Transbond XT used with and without primer and for Phase II two-paste system used with and without a liquid resin. The Student's t-test was applied for comparison of the two groups.

Results

In Group I, the mean bond strength of Transbond XT without primer (12.5272MPa, 95% CI: 11.76-13.68) was compared to that of Transbond XT with XT primer (13.2028MPa, 95% CI: 12.39-14.06). In Group II, the mean shear bond strength of Phase II two-paste system without primer (10.66MPa, 95% CI: 10.13-11.18) was compared to that of Phase II two-paste system with primer (10.66MPa, 95% CI: 10.13-11.18), and the values were statistically insignificant.

Conclusion

The shear bond strength of the brackets bonded with Transbond XT and Phase II without using the liquid primer was sufficient enough to withstand the masticatory forces, which implies the elimination of liquid primer during bonding.

Clinical Significance

The development of the acid-etch technique and Bisphenol A-glycidyl methacrylate-based liquid resin has changed the practice of orthodontics over the years more than any other single principle formulated. Despite its wide popularity, the cytotoxicity, which stems from the use of liquid primer, needs attention.

The influence of enamel sandblasting on the shear bond strength and fractography of the bracket-adhesive-enamel complex tested in vitro by the DIN 13990:2017-04 standard

OBJECTIVES

This study was conducted in order to investigate whether enamel sandblasting as an adjunct or substitute to the acid-etch technique has an effect on the shear bond strength (SBS) and fractography of the bracket-adhesive-enamel complex using the DIN 13990:2017-04 standard.

MATERIALS AND METHODS

Upper central incisor brackets (discovery®, Dentaurum, Germany) were bonded using Transbond XT™ (3M Unitek, Germany) on bovine incisors prepared by four different methods (15 samples each): sandblasting with 27 μm Al₂O₃ at 1.2 bar (s), acid etching with 37.4% phosphoric acid (a), sandblasting with 27 μm Al₂O₃ at 1.2 bar followed by acid etching (s1a), and sandblasting with 50 μm Al₂O₃ at 5.7 bar followed by acid etching (s2a). The SBS and adhesive remnant index (ARI) were measured, followed by one-way analysis of variance and Fisher's exact tests at 5%.

RESULTS

The SBS in groups s (5.6 ± 2.2 MPa), a (17.1 ± 4.3 MPa), s1a (18.3 ± 4.3 MPa), and s2a (18.5 ± 4.6 MPa) indicated that the s group was significantly inferior to all the other groups (p < 0.001). Likewise, the ARI analysis indicated a different performance of the s group (mostly ARI of 0) compared to the other groups (p < 0.001) and a tendency for different ARI between the a and s1a/s2a groups.

CONCLUSIONS

In vitro enamel sandblasting could not substitute acid etching and did not offer improved SBS when used before acid etching, regardless of air pressure and powder granulation. Sandblasting without acid etching produced less residual resin on the tooth after debonding.

CLINICAL RELEVANCE

The clinical use of adjunct enamel sandblasting prior to etching to enhance SBS has to be questioned.