Comparison of bond strength of three adhesives: composite resin, hybrid GIC, and glass-filled GIC

Structural and Color Alterations of Teeth following Orthodontic Debonding: A Systematic Review

AIM

The objective of this study was to explore the effects of fixed orthodontic appliances on enamel structure by assessing microfractures, surface roughness, and alterations in color.

METHODS

This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A systematic search of online databases was conducted using the keywords 'enamel' AND 'orthodontic debonding'. Eligibility criteria included both in vivo and ex vivo clinical trials conducted on human teeth.

RESULTS AND DISCUSSION

A total of 14 relevant papers were analyzed. Various instruments and techniques were utilized across different studies to assess surface roughness, color change, and surface fractures.

CONCLUSIONS

The findings of this study suggest that ceramic brackets may lead to an increase in enamel fractures, particularly during bracket removal. The surface roughness of enamel exhibits variability depending on the adhesive substance and polishing methods used post-removal. Fixed orthodontic appliances could induce changes in enamel color, which may be alleviated by the use of nano-hydroxyapatite or specific polishing techniques. Further research is necessary to identify effective strategies for managing these color changes and improving the overall outcomes of fixed orthodontic treatment.

Visible light-activated curcumin-doped zinc oxide nanoparticles integrated into orthodontic adhesive on Micro-tensile bond strength, degree of conversion, and antibacterial effectiveness against Staphylococcus Aureus. An investigation using scanning electron microscopy and energy-dispersive X-ray spectroscopy

AIM

To acquire a thorough comprehension of the photoactivated Cur-doped ZnONPs at different concentrations 0%, 2.5%, and 5% on the physical qualities, antibacterial efficacy, degree of conversion, and μshear bond strength between orthodontic brackets and the enamel surface.

MATERIAL AND METHODS

An extensive investigation was carried out utilizing a range of analytical methods, scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy, micro tensile bond strength (μTBS) testing, and evaluation of antibacterial effectiveness. Cur-doped ZnONPs at concentrations of 2.5% and 5% were blended with Transbond XT, a light-curable orthodontic adhesive. A control group without the addition of Cur-doped ZnONPs was also prepared. The tooth samples were categorized into three groups based on the weight percentage of NPs: Group 1 (control) with 0% Cur-doped ZnONPs, Group 2 with 2.5 wt% Cur-doped ZnONPs, and Group 3 with 5 wt% Cur-doped ZnONPs. The SEM technique was employed to analyze the morphological characteristics of Cur-doped ZnONPs and ZnONPs. The composition and elemental distribution of the modified Cur-doped ZnONPs were assessed using energy-dispersive X-ray spectroscopy. The effectiveness of NPs at various concentrations against S.Mutans was gauged through the pour plate method. DC of Cur-doped ZnONPs at a region of 1608 cm-1 to 1636 cm-1 for the cured area, whereas the uncured area spanned the same range of 1608 cm-1 to 1636 cm-1 was assessed. The Adhesive Remnant Index (ARI) approach was utilized to investigate the bond failure of orthodontic brackets, while a Universal Testing Machine (UTM) was utilized to test μTBS. The Kruskal-Wallis test was employed to investigate variations in S.mutans survival rates. To determine the μTBS values, analysis of variance (ANOVA) and the post hoc Tukey multiple comparisons test were used.

RESULTS

The maximum μTBS was given and documented in group 3: 5 wt% Cur-doped ZnONPs (21.21 ± 1.53 MPa). The lowest μTBS was given in group 2: 2.5 wt% Cur-doped ZnONPs (19.58 ± 1.27 MPa). The highest efficacy against S.mutans was documented in group 3 in which 5 wt% Cur-doped ZnONPs (0.39 ± 0.15). The lowest efficacy was seen in group 1 in which no Cur-doped ZnONPs were used (6.47 ± 1.23). The ARI analysis indicated that the predominant failure was between scores 0 and 1 among all experimental groups. Control group 1 which was not modified showed the highest DC (73.11 ± 4.19).

CONCLUSION

Orthodontic adhesive, containing 5% Cur-doped ZnONPs photoactivated with visible light exhibited a favorable impact on μTBS and indicated enhanced antibacterial efficacy against S.mutans. Nevertheless, it was observed that the addition of Cur-doped ZnONPs at different concentrations (2.5%,5%) resulted in a decrease in the monomer-to-polymer ratio compromising DC.

Teeth Microcracks Research: Towards Multi-Modal Imaging

This perspective is an overview of the recent advances in teeth microcrack (MC) research, where there is a clear tendency towards a shift from two-dimensional (2D) to three-dimensional (3D) examination techniques, enhanced with artificial intelligence models for data processing and image acquisition. X-ray micro-computed tomography combined with machine learning allows 3D characterization of all spatially resolved cracks, despite the locations within the tooth in which they begin and extend, and the arrangement of MCs and their structural properties. With photoluminescence and micro-/nano-Raman spectroscopy, optical properties and chemical and elemental composition of the material can be evaluated, thus helping to assess the structural integrity of the tooth at the MC site. Approaching tooth samples having cracks from different perspectives and using complementary laboratory techniques, there is a natural progression from 3D to multi-modal imaging, where the volumetric (passive: dimensions) information of the tooth sample can be supplemented by dynamic (active: composition, interaction) image data. Revelation of tooth cracks clearly shows the need to re-assess the role of these MCs and their effect on the structural integrity and longevity of the tooth. This provides insight into the nature of cracks in natural hard materials and contributes to a better understanding of how bio-inspired structures could be designed to foresee crack propagation in biosolids.

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.

Effect of fluoride varnish in combination with simulated oral environment on enamel-bracket shear bond strength

To determine the effect of fluoride varnish application combined with a simulated oral environment prior to bracket bonding on the shear bond strength (SBS) between brackets and tooth enamel. Sixty de-identified, extracted teeth were grouped to either receive or not receive fluoride varnish and then stored for 7 days at 37 °C in phosphate-buffered saline (PBS) solution or PBS combined with three 15-min cycles/day in a demineralizing solution to simulate pH variation following meals. Subsequently, brackets were bonded and after 24-h dark cure at 37 °C, debonded using shear forces in a simulated oral environment. The maximum shear force was used to calculate SBS, and the adhesive remnant index (ARI) was determined by image analysis of photos of the bracket mesh pad after debonding. A statistically higher SBS (10.16 MPa) was observed when fluoride varnish was applied prior to storage in PBS + demineralizing solution compared to SBS (6.38 MPa) following storage in the same solution without varnish application. Based on 37% effect size, this difference is also clinically relevant. In contrast, no significant differences in SBS were observed with varnish application combined with PBS with no demineralizing solution or between storage solution alone. Moreover, there was no significant difference in ARI due to varnish combined with either storage method or storage solution only. Results suggest varnish application prior to bracket bonding in combination with simulated oral environment that included acid exposure is beneficial in maintaining higher SBS between bracket and enamel. Despite higher SBS, adhesive remaining on enamel did not increase.

High-Intensity Light-Emitting Diode and Reduced Curing Times—An In Vitro Study

Objective:

To evaluate and compare the effect of high-intensity light-emitting diode (LED) light-curing unit at different curing times on the shear bond strength (SBS), surface enamel loss, and degree of polymerization of a light-cure and dual-cure adhesive system.

Materials and Methods:

One hundred and twenty extracted human premolar teeth were divided into 2 groups— group 1 (light cure) and group 2 (dual cure), depending on the adhesive system used. These groups were further subdivided into 3 subgroups with 20 teeth each, depending on the duration of curing. A high-intensity LED curing unit was used to bond metal brackets onto the teeth. The samples were tested on a universal testing machine to measure the SBS. The samples were then observed under a simple microscope and modified adhesive remnant index scores were assigned. The bracket bases were mapped with energy-dispersive X-ray spectrometry to evaluate the amount of enamel present. Cured adhesive was scraped and was subjected to Fourier-Transform Infrared Spectroscopy to assess the degree of cure (%DC).

Results:

An increase in curing durations increased mean SBS values, %DC, and calcium-phosphorous ratios (Ca:P). Similarly, these parameters were higher for dual-cure subgroups when compared to light-cure subgroups.

Conclusion:

High-intensity LEDs can be used successfully for bonding orthodontic brackets with reduced curing duration. These LEDs help to reduce chairside time and can minimize damage to enamel without compromising bond strength.

Safe Debonding of Fixed Appliances: A Comparison of Traditional Techniques and LODI Devices on Different Bracket Types in Terms of Enamel Cracks, Site of Bond Failure, and Bracket Reusability

The objective of this study was to compare the effects of the debonding of three different bracket types by means of three popular debonding methods. A total of 180 human third molars was divided into six groups, consisting of 20 teeth each. Three bracket types were bonded to the enamel (metal brackets with an integral base and a foil mesh base, and ceramic brackets) and three methods of bracket debonding were employed (bracket removal pliers, Weingart pliers, and Lift-Off Debonding Instrument). The samples were examined with scanning electron microscopy to assess the number of enamel cracks, measure the area of adhesive remaining on the enamel, and calculate the adhesive remnant index (ARI). There were no statistically significant differences between the groups in terms of the number of enamel cracks after bracket debonding. The amount of adhesive remaining on the teeth after the brackets were removed was significantly different between the groups. LODI and Weingart pliers are considered to be the safest methods of debonding brackets with an integral base, while LODI is the best tool for brackets with foil mesh. Bracket removal pliers are considered to be the preferred method for ceramic bracket debonding.

Surface Characteristics, Fluoride Release and Bond Strength Evaluation of Four Orthodontic Adhesives

Orthodontic adhesives have similar properties in terms of fluoride release, roughness, shear bond strength or cement debris for specific clinical conditions. Three commercial consecrated orthodontic adhesives (Opal Seal^®, Blugloo^®, Light Bond^®) were compared with an experimental orthodontic material (C1). Brackets were bonded to enamel using a self-etch technique followed by adhesive application and then de-bonded 60 days later. Share bond strength evaluation, scanning electron microscopy, atomic force microscopy and fluoride release analysis were performed. The highest amount of daily and cumulative fluoride release was obtained for the experimental material, while the lowest value was observed for Opal Seal^®. The materials evaluated in the current study presented adequate shear bond strength, with the experimental material having a mean value higher than Opal Seal and Blugloo. The atomic force microscopy measurements indicated that the smoothest initial sample is Opal Seal^® followed by Light Bond^®. Scanning electron microscopy evaluation indicated different aspects of cement debris on the enamel and/or bracket surface, according to the type of adhesive. The experimental material C1 presented adequate properties in terms of shear bond strength, fluoride release, roughness and enamel characteristics after de-bonding, compared to the commercial materials. Under these circumstances, it can be considered for clinical testing.

In vivo examination of enamel microcracks after orthodontic debonding: Is there a need for detailed analysis?

INTRODUCTION

Our aim was to assess changes in the number of enamel microcracks (EMCs) after removing metal brackets in teeth with and without visible EMCs before the bonding procedure.

METHODS

Before bonding, 13 patients having teeth with visible EMCs and 13 subjects whose teeth were free of EMCs were included in the study. All patients were asked to complete a questionnaire with a detailed medical history at the beginning of treatment and after removing metal brackets. The number of teeth with visible EMCs and the number of premolars without EMCs were recorded for each subject twice, that is, before bonding and after debonding, together with the tooth sensitivity assessments elicited by compressed air and cold testing.

RESULTS

The number of visible EMCs in premolars increased after removing metal brackets. EMCs were recorded in at least 25.0% of all evaluated teeth for the patients having teeth with and without visible EMCs at the beginning of treatment. However, the changes in the number of visible EMCs were not significantly different (P = 0.619) between the groups. For the subjects with visible EMCs, tooth sensitivity caused by cold was registered nearly 3 times more often after removing brackets compared with the patients without EMCs prior bonding.

CONCLUSIONS

Formation of EMCs was noticed after debonding. Changes in the number appeared to be similar for the subjects with and without visible EMCs before bonding. Higher incidence of EMCs was associated with more frequent tooth sensitivity perceptions after removing brackets.

A Novel Method Using Confocal Laser Scanning Microscopy for Three-Dimensional Analysis of Human Dental Enamel Subjected to Ceramic Bracket Debonding

The aim of this in vitro study was to present a method using confocal laser scanning microscopy for three-dimensional analysis of human dental enamel subjected to ceramic bracket debonding. The labial enamel surfaces of three upper central incisors were prepared and mounted in the form of standardized specimens. A sample repositioning protocol was established to enable surface measurement and analysis before and after bracket debonding. Observations were made of representative areas measuring 1,280 × 1,280 μm2, in the center of the enamel samples, as well as of the total topography (2,500 × 3,500 μm) of the bonding areas provided by the equipment software. Noncontact three-dimensional high-resolution image analyses revealed the capabilities of the employed technique and methodology to permit the examination of specific characteristics and alterations on the surfaces, before and after the debonding and finishing procedures. The new protocol was effective to provide qualitative and quantitative assessments of changes on the same dental surfaces at different trial times. The methodology constitutes a feasible tool for revealing the effects of debonding of ceramic brackets on sound and previously injured dental enamel surfaces.

Laser-Milled Microslits Improve the Bonding Strength of Acrylic Resin to Zirconia Ceramics

Heightened aesthetic considerations in modern dentistry have generated increased interest in metal-free “zirconia-supported dentures.” The lifespan of the denture is largely determined by the strength of adhesion between zirconia and the acrylic resin. Thus, the effect on shear bond strength (SBS) was investigated by using an acrylic resin on two types of zirconia ceramics with differently sized microslits. Micromechanical reticular retention was created on the zirconia surface as the novel treatment (microslits (MS)), and air-abrasion was used as the control (CON). All samples were primed prior to acrylic resin polymerization. After the resin was cured, the SBS was tested. The obtained data were analyzed by using multivariate analysis of variance(α = 0.05). After the SBS test, the interface failure modes were observed by scanning electron microscopy. The MS exhibited significantly higher bond strength after thermal cycles (p < 0.05) than the CON. Nevertheless, statistically comparisons resulted in no significant effect of the differently sized microslits on SBS (p > 0.05). Additionally, MS (before thermal cycles: 34.8 ± 3.6 to 35.7 ± 4.0 MPa; after thermal cycles: 26.9 ± 3.1 to 32.6 ± 3.3 MPa) demonstrated greater SBS and bonding durability than that of CON (before thermal cycles: 17.3 ± 4.7 to 17.9 ± 5.8 MPa; after thermal cycles: 1.0 ± 0.3 to 1.7 ± 1.1 MPa), confirming that the micromechanical retention with laser-milled microslits was effective at enhancing the bonding strength and durability of the acrylic resin and zirconia. Polycrystalline zirconia-based ceramics are a newly accessible material for improving removable prosthodontic treatment, as the bond strength with acrylic resin can be greatly enhanced by laser milling.

Enamel microcracks in the form of tooth damage during orthodontic debonding: a systematic review and meta-analysis of in vitro studies

Objectives

To evaluate and compare the enamel microcracks (EMCs) characteristics (qualitative and quantitative) in the form of tooth damage before and after debonding from human teeth of in vitro studies.

Eligibility criteria

Laboratorial studies evaluating EMCs characteristics before and after debonding metal and ceramic brackets from human teeth with intact buccal enamel.

Information sources

An electronic search of four databases (all databases of the Cochrane Library, CA Web of Science, MEDLINE via PubMed, and Google Scholar) and additional manual searches were carried out, without language restrictions. Studies published between 2000 and 2017 years were selected. Reference lists of the included articles were screened, and authors were contacted when necessary.

Risk of bias

The following six parameters were analyzed: blinding of examiner and outcome assessment, incomplete outcome data before bonding and after debonding, selective outcome reporting, and incomplete reporting of EMCs assessment.

Included studies

Out of 430 potentially eligible studies, 259 were screened by title and abstract, 180 were selected for full-text analysis, 14 were included in the systematic review. Seven studies were selected for the meta-analysis.

Synthesis of results

The results for EMCs characteristics were expressed as mean differences (MDs) with their 95 per cent confidence intervals (CIs), and calculated from random-effects meta-analyses. Debonding was associated with the increase in number (three studies, MD = 3.50, 95% CI, 2.13 to 4.87, P < 0.00001), length (seven studies, MD = 3.09 mm, 95% CI, 0.75-5.43, P < 0.00001), and width (three studies, MD = 0.39 µm, 95% CI, -0.01 to 0.79, P = 0.06) of EMCs. Considerable statistical heterogeneity was found for two forest plots evaluating the changes of number and length characteristics during debonding.

Conclusions

There is weak evidence indicating length and width of EMCs increase following bracket removal and the scientific evidence concerning quantitative evaluation of the number parameter before and after debonding is insufficient. However, there is a strong evidence that after debonding the number of EMCs is likely to increase.

Registration

No registration was performed.

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.

Shear bond strength of new and rebonded orthodontic brackets to the enamel surfaces

OBJECTIVES

The objective of this study was to compare the shear bond strength (SBS) of new and rebounded orthodontic brackets bonded to the buccal sound and cleaned enamel surfaces using two orthodontic adhesives: resin-modified glass-ionomer (RMGI) and resin-composite.

MATERIALS AND METHODS

Forty premolars were randomly allocated into four groups, 10 teeth/group. New and rebonded brackets were bonded to sound and cleaned enamel surface, and then were subjected to thermocycling. The bond strength was determined using a universal testing machine at a crosshead speed of 1 mm/min. Remaining adhesives on enamel after bracket debonding was scored independently by two investigators who were not aware of the four different groups, using adhesive remnant index (ARI).

RESULTS

There was a statistical significant difference in SBS of the four groups (P = 0.005). SBS values were significantly higher with cleaned enamel surfaces after adhesive removal compared to sound enamel. SBS was significantly higher for rebonded brackets, when compared with the new brackets. No significant difference was found between the two adhesives types. The level of agreement between the two raters was higher toward the classification of higher categories of ARI (scores 5 and 6) with agreement percentage 91.7% and 100%, respectively. There was more adhesive remained among resin-composite groups.

CONCLUSIONS

The bond strength of debonded sandblasted stainless-steel brackets was higher than new brackets. Resin-composite and RMGI orthodontic adhesives used in this study exhibited sufficient SBS values for bonding brackets to sound and cleaned enamel and comparable to each other.

In vitro Evaluation of Shear Bond Strength of Orthodontic Brackets Bonded with Different Adhesives

Background:

There is necessary of dry operating field for bonding of orthodontic brackets. The presence of moisture can alter the bond strength. Hence, the aim of the present study was to evaluate the shear bond strength of orthodontic brackets with different adhesives.

Materials and Methods:

In this in vitro study, a total of 100 orthodontically extracted premolars with sound crown structure were divided into 4 equal groups of different primers. Bonding on the buccal surface of all teeth was done after acid etching with upper premolar brackets using different primers followed by light curing. Shear bond strength was evaluated with or without salivary contamination with both adhesives. A shear force for deboning the bracket was done with universal testing machine. The debonded specimens were examined at ×10 magnification to check site of bond failure and remaining adhesive on tooth using adhesive remnant index (ARI). The obtained data were statistically evaluated using SPSS 20 for Windows (SPSS Inc., Chicago, IL, USA) using ANOVA, Kolmogorov–Smirnov, and Levene's test at the statistical significance of P < 0.05.

Results:

Transbond Plus showed higher shear bond strength of 8.92 MPa under dry and 5.65 MPa with saliva contamination over Transbond XT of 7.24 MPa under dry and 2.43 MPa with saliva contamination, respectively. Higher ARI score was found without contamination in both adhesives.

Conclusion:

Transbond Plus hydrophilic resin had good shear bond strength under both dry and contamination condition compared to hydrophobic Transbond XT resin material.

Comparison of Shear Bond Strength of Four Types of Orthodontic Brackets with Different Base Technologies

Objectives

The aim of this study was to compare the shear bond strength (SBS) of brackets systems with four different base technologies.

Materials and Methods

Maxillary first premolars were randomly divided into four groups of thirty specimens each: (1) Master Series™ conventional twin, (2) T3™ self-ligating, (3) Victory series™ conventional twin, and (4) H4™ self-ligating brackets. Maxillary first premolars were bracketed using an acid-etch composite system, and the SBS measured using an Instron Universal Testing Machine at a crosshead speed of 2 mm/min. The ANOVA and Tukey’s multiple comparison tests were performed with significance predetermined at P ≤ 0.05.

Results

The overall mean bond strengths were 8.49 ± 2.93, 10.85 ± 3.34, 9.42 ± 2.97, and 9.73 ± 2.62 for the Groups 1, 2, 3, and 4 brackets, respectively. One-way ANOVA test gave an F = 3.182 with a P = 0.026. The Group 1 and Group 2 were observed to have statistically significant difference with a P = 0.014.

Conclusions

The T3 self-ligating one-piece design with microetched Quadra Grip™ base brackets had the highest bond strength. The SBS difference between Group 2, Group 3, and Group 4 was not significant, but the difference between Group 2 and Group 1 was statistically significant.

Easy Debonding of Ceramic Brackets Bonded with a Light-Cured Orthodontic Adhesive Containing Microcapsules with a CO2 Laser

OBJECTIVE

An easy debonding method for ceramic brackets using a light-cured Bis-GMA resin containing heat-expandable microcapsules and CO₂ laser was investigated.

BACKGROUND

Ceramic brackets are used frequently in orthodontic treatment because of their desirable esthetic properties. However, the application of heavy force to ceramic brackets in debonding can fracture the tooth enamel and ceramic brackets, causing tooth pain.

MATERIALS AND METHODS

In total, 60 freshly extracted bovine permanent mandibular incisors were divided randomly into 10 groups of 6 specimens each, corresponding to the number of variables tested. Ceramic brackets were bonded to bovine permanent mandibular incisors using an orthodontic bonding agent containing heat-expandable microcapsules at different levels (0-30 wt%) and resin composite paste, and cured by a curing device. The bond strengths were measured before and after CO₂ laser irradiation, and the temperature increase in the pulp chamber in fresh human first premolars was also evaluated.

RESULTS

With CO₂ laser irradiation for 5 sec to the bracket, the bond strength in the 25% microcapsule group decreased significantly, to ∼0.17-fold, compared with that of the no-laser group (p < 0.05). The maximum temperature increase in the pulp chamber was 5.3°C with laser irradiation, which was less than the level that induces pulp damage.

CONCLUSIONS

From these results, it seems likely that the combined use of a light-cured orthodontic bonding agent containing microcapsules and a CO₂ laser is a simple debonding system for ceramic brackets, with less debonding time and enamel damage.

Effect of sandblasting and enamel deproteinization on shear bond strength of resin-modified glass ionomer

INTRODUCTION

The purpose of this study was to compare, in vitro, the shear bond strength of resin-modified glass ionomer (RMGI) bonded to an enamel surface prepared by either sandblasting with 50μm of aluminium oxide particles, deproteinization with 5.25% NaOCl, or by combining both techniques.

MATERIAL AND METHODS

One hundred and fifty human premolars were cleaned and randomly divided into five groups. In group 1, the teeth were etched using 37% phosphoric acid and bonded with Transbond XT. In group 2, the teeth were etched using 37% phosphoric acid and bonded with Fuji Ortho LC. In group 3, the teeth were deproteinized with 5.25% NaOCl for one minute then etched with 37% phosphoric acid and bonded with Fuji Ortho LC. In group 4, the enamel was sandblasted with 50μm of aluminium oxide particles for 5seconds prior to etching and bonding with Fuji Ortho LC. In group 5, the teeth were both sandblasted with 50μm of aluminium oxide particles for 5seconds and deproteinized with 5.25% NaOCl for one minute prior to etching using 37% phosphoric acid and bonding with Fuji Ortho LC. The shear bond strength was tested using a universal testing machine with a crosshead speed of 1.0mm/min. The adhesive remnant index (ARI) index was also determined for each group.

RESULTS

The mean shear bond strengths were as follows: group 1: 11.33±2.60MPa, group 2: 8.14±2.09, group 3: 9.57±3.25MPa, group 4: 9.49±1.99MPa and group 5: 9.76±2.29MPa (P=0.0001).

CONCLUSION

The results show that pre-treating the enamel with either sandblasting, NaOCl, or both, could give a significantly higher shear bond strength than using RMGI with acid etch alone.

Comparison of bracket bond strength to etched and unetched enamel under dry and wet conditions using Fuji Ortho LC glass-ionomer

Background. Acid etching prior to orthodontic bracket bonding may result in enamel wear or cracks following bracket removal. The manufacturer of Fuji Ortho LC glass-ionomer (GI) claims that it can bond brackets to wet unetched enamel. This study aimed to compare the bracket bond strength to etched and unetched enamel under dry and wet conditions. Methods. In this in vitro study, 60 intact premolar teeth were randomly assigned to 6 groups (etched and dried, etched and moistened with distilled water, etched and moistened with saliva, unetched and dried, unetched and moistened with water, unetched and moistened with saliva). In all the groups, Leon 4 brackets were bonded to the enamel using Fuji Ortho LC GI. The teeth were immersed in distilled water at 37°C for 24 hours and subjected to shear loads at a crosshead speed of 5 mm/min in a Zwick machine for bond strength testing. Data were analyzed with ANOVA, Tukey test and independent t-test. Results . The mean bond strength values in groups 1 (etched, dry), 2 (etched, moistened with water), 3 (etched, moistened with saliva), 4 (unetched, dry), 5 (unetched, moistened with water) and 6 (unetched, moistened with saliva) were 21.86, 16.46, 10.49, 8.12, 9.15 and 9.52 MPa, respectively. Significant differences in bond strength were detected between groups 1 and 2 and all the other groups (P < 0.05), with no significant difference between groups 1 and 2 (P > 0.05). Conclusion. Fuji Ortho LC GI provided adequate bond strength between brackets and enamel. To acquire higher bond strength, brackets must be bonded to etched and dried enamel.

Shear bond strength of ceramic and metallic orthodontic brackets bonded with self-etching primer and conventional bonding adhesives

Introduction

Adult patients typically require high-quality orthodontic treatment for ceramic brackets, but some clinicians remain concerned about the bond strength of these brackets. Therefore, the aim of this study was to determine the shear bond strength and de-bonding characteristics of metallic and ceramic brackets bonded with two types of bonding agents.

Methods

In an experimental study done in 2013 in Babol, Iran, 120 extracted human maxillary premolar teeth were randomly divided into four groups as follows: HM group: metallic bracket/conventional bonding agent; SM group: metallic bracket/Transbond self-etching primer; HC group: ceramic bracket/conventional bonding agent; SC group: ceramic bracket/Transbond self-etching primer. Twenty-four hours after thermocycling (1000 cycle, 5 °C–55 °C), the shear bond strength values were measured. The amount of resin remaining on the tooth surface (adhesive remnant index: ARI) was determined under a stereomicroscope. Enamel detachment index was evaluated under a scanning electron microscope. To perform statistical analysis, ANOVA, Kruskal–Wallis, and Tukey post-hoc tests were applied. The level of significance was set at p <0.05.

Results

The mean shear bond strength values (MPa ± SD) were group HM=12.59, group SM=11.15, group HC=7.7, and group SC=7.41. Bond strength differences between groups HM and SM (p=0.063) and between HC and SC (p=0.091) were not statistically significant. There were significant differences between HM and HC and between SM and SC groups (p < 0.05). Insignificant differences were found in ARI among all groups.

Conclusion

Our findings indicated that the metallic brackets had higher bond strengths in comparison with ceramic brackets. In addition, self-etching primer was able to produce fewer bonds compared with the conventional technique. Many samples showed the bracket-adhesive interface failure or failure inside the adhesive.

The influence of adding modified zirconium oxide-titanium dioxide nano-particles on mechanical properties of orthodontic adhesive: an in vitro study

BACKGROUND

The purpose of this in-vitro study was to examine the effect of incorporating different concentrations of Zirconium oxide-Titanium dioxide (ZrO2-TiO2) nanoparticles, which can have antibacterial properties, on the mechanical properties of an orthodontic adhesive.

METHODS

ZrO2-TiO2 (Zirconium oxide, HWNANO, Hongwu International Group Ltd, China) -Titanium dioxide, Nanoshell, USA) nanopowder were incorporated into orthodontic adhesive (Transbond XT, 3 M Unitek, Monrovia, USA) with different concentrations (0.5% weight nonofiller and 1% weight nanofiller). The size of nanoparticle was 70-80 nm for ZrO2 and less than 50 nm for TiO2. For measuring the shear bond strength of the three groups of orthodontic adhesives [Transbond (control), Transbond mixed with 0.5% weight ZrO2-TiO2, and Transbond mixed with 1% weight ZrO2-TiO2], 30 freshly extracted human first premolars were used and bonded with stainless steel metal brackets (Dentaurum®, Discovery®, Deutschland), using the 3 orthodontic adhesives and 3 M Unitek; Transbond TM Plus Self-Etching Primer (10 samples in each group). The recorded values of compressive strength and tensile strength (measured separately on 10 samples of orthodontic adhesives (add the 3 D size of sample, light cured for 40 s on both sides) of each orthodontic adhesives), as well as the shear bond strength in Mega Pascal unit (MPa) were collected and exposed to one-way analysis of variance (ANOVA) and Tukey's post-hoc tests.

RESULTS

orthodontic adhesive with 1% weight ZrO2-TiO2 showed the highest mean compressive (73.42 ± 1.55 MPa, p: 0.003, F: 12.74), tensile strength (8.65 ± 0.74 MPa, p: 0.001, F: 68.20), and shear bond strength (20.05 ± 0.2 MPa, p: 0.001, F: 0.17).

CONCLUSIONS

Adding ZrO2-TiO2 nanoparticle to orthodontic adhesive increased compressive strength, tensile strength, and shear bond strength in vitro, but in vivo studies and randomized clinical trials are needed to validate the present findings.

Effect of orthodontic debonding and residual adhesive removal on 3D enamel microroughness

Background

Termination of fixed orthodontic treatment is associated with bracket debonding and residual adhesive removal. These procedures increase enamel roughness to a degree that should depend on the tool used. Enamel roughening may be associated with bacterial retention and staining. However, a very limited data exists on the alteration of 3D enamel roughness resulting from the use of different tools for orthodontic clean-up.

Aims

1. To perform a precise assessment of 3D enamel surface roughness resulting from residual adhesive removal following orthodontic debonding molar tubes.

2. To compare enamel surfaces resulting from the use of tungsten carbide bur, a one-step polisher and finisher and Adhesive Residue Remover.

Material and Methods

Buccal surfaces of forty-five extracted human third molars were analysed using a confocal laser microscope at the magnification of 1080× and 3D roughness parameters were calculated. After 20 s etching, molar tubes were bonded, the teeth were stored in 0.9% saline solution for 24 hours and debonded. Residual adhesive was removed using in fifteen specimen each: a twelve-fluted tungsten carbide bur, a one-step finisher and polisher and Adhesive Residue Remover. Then, surface roughness analysis was repeated. Data normality was assessed using Shapiro–Wilk test. Analysis of variance (ANOVA) was used to compare between variables of normal distribution and for the latter—Kruskal-Wallis test.

Results

Sa (arithmetical mean height) was significantly different between the groups (p = 0, 01326); the smoothest and most repeatable surfaces were achieved using Adhesive Residue Remover. Similarly, Sq (root mean square height of the scale-limited surface) had the lowest and most homogenous values for Adhesive Residue Remover (p = 0, 01108). Sz (maximum height of the scale-limited surface) was statistically different between the groups (p = 0, 0327), however no statistically significant differences were found concerning Ssk (skewness of the scale-limited surface).

Discussion

Confocal laser microscopy allowed 3D surface analysis of enamel surface, avoiding the limitations of contact profilometry. Tungsten carbide burs are the most popular adhesive removing tools, however, the results of the present study indicate, that a one step polisher and finisher as well as Adhesive Residue Remover are less detrimental to the enamel. This is in agreement with a recent study based on direct 3D scanning enamel surface. It proved, that a one-step finisher and polisher as well as Adhesive Residue Remover are characterized by a similar effectiveness in removing residual remnants as tungsten carbide bur, but they remove significantly less enamel.

Conclusion

Orthodontic debonding and removal of adhesive remnants increases enamel roughness. The smoothest surfaces were achieved using Adhesive Residue Remover, and the roughest using tungsten carbide bur.

Influence of Adhesives and Methods of Enamel Pretreatment on the Shear Bond Strength of Orthodontic Brackets

AIM

The objective of present study was to examine influence of adhesives and methods of enamel pretreatment on the shear bond strength (SBS) of orthodontic brackets. The adhesives used were resin-reinforced glass ionomer cements-GIC (Fuji Ortho LC) and composite resin (Transbond XT).

MATERIAL AND METHODS

The experimental sample consisted of 80 extracted human first premolars. The sample was divided into four equal groups, and the metal brackets were bonded with different enamel pretreatments by using two adhesives: group A-10% polyacrylic acid; Fuji Ortho LC, group B-37% phosphoric acid; Fuji Ortho LC, group C-self etching primer; Transbond XT, group D-37% phosphoric acid, primer; Transbond XT. SBS of brackets was measured. After debonding of brackets, the adhesive remnant index (ARI) was evaluated.

RESULTS

After the statistical analysis of the collected data was performed (ANOVA; Sheffe post-hoc test), the results showed that significantly lower SBS of the group B was found in relation to the groups C (p=0.031) and D (p=0.026). The results of ARI were similar in all testing groups and it was not possible to determine any statistically significant difference of the ARI (Chi- square test) between all four experimental groups.

CONCLUSION

The conclusion is that the use of composite resins material with appropriate enamel pretreatment according to manufacturer's recommendation is the "gold standard" for brackets bonding for fixed orthodontic appliances.

Covering of fiber-reinforced composite bars by adhesive materials, is it necessary to improve the bond strength of lingual retainers?

Objectives:

The objectives were to evaluate the shear bond strength (SBS) of fiber-reinforced composite (FRC) retainers when bonding them to teeth with and without covering the FRC bars using two different adhesive systems.

Materials and Methods:

Hundred and twenty extracted human maxillary premolars were randomly divided into eight groups (n = 15). FRC bars (4 mm length, Everstick Ortho^®, Stick Tech, Oy, Turku, Finland) were bonded to the proximal (distal) surfaces of the teeth using two different adhesives (Tetric Flow [TF, Ivoclar Vivadent, Switzerland] and resin-modified glass ionomer cement [RMGIC, ODP, Vista, CA, USA]) with and without covering with the same adhesive. Specimens were exposed to thermocycling (625 cycles per day [5–55°C, intervals: 30 s] for 8 days). The SBS test was then performed using the universal testing machine (Zwick, GMBH, Ulm, Germany). After debonding, the remaining adhesive on the teeth was recorded by the adhesive remnant index (0–3).

Results:

The lowest mean SBS (standard deviation) was found in the TF group without covering with adhesive (12.6 [2.11] MPa), and the highest bond strength was in the TF group with covering with adhesive (16.01 [1.09] MPa). Overall, the uncovered RMGIC (15.65 [3.57] MPa) provided a higher SBS compared to the uncovered TF. Covering of FRC with TF led to a significant increase in SBS (P = 0.001), but this was not true for RMGIC (P = 0.807). Thermal cycling did not significantly change the SBS values (P = 0.537). Overall, eight groups were statistically different (ANOVA test, F = 3.32, P = 0.034), but no significant differences in bond failure locations were found between the groups (Fisher's exact tests, P = 0.92).

Conclusions:

The present findings showed no significant differences between SBS of FRC bars with and without covering by RMGIC. However, when using TF, there was a significant difference in SBS measurements between covering and noncovering groups. Therefore, the use of RMGIC without covering FRC bars can be suggested, which can be validated with in vivo studies.

Moisture insensitive primer: A myth or truth

OBJECTIVES

To compare the mean shear bond strength (SBS) of moisture insensitive primer (MIP) used for orthodontic bonding in the presence and absence of saliva.

MATERIALS AND METHODS

A total of 60 human noncarious maxillary premolars with sound buccal surfaces, recently extracted were collected in two groups of each 30. Maxillary premolar brackets were bonded to the teeth using light cure (Transbond XT, 3M Unitek, Monrovia, CA, USA) and MIP (Transbond MIP 3M Unitek, Monrovia, CA, USA,) in the presence and absence of saliva. Operators' saliva was used during the bonding under moist condition. After debonding, all the specimens were examined under a stereomicroscope (×40 magnification) for adhesive remnant using adhesive remnant index (ARI). The SBS tests were done using Instron universal testing machine at cross-head speed of 1 mm/min, force passing parallel to the buccal surface using custom rod and registered in Newtons later converted into Megapascals.

RESULTS

Light cure and MIP (Transbond MIP and Transbond XT, 3M Unitek, Monrovia, CA, USA) in the absence of saliva showed higher mean SBS than the presence of saliva. Group I (light cure and MIP) in the absence of saliva showed mean SBS of 9.65 ± 0.90 Mpa. Group II (light cure and MIP) with the presence of saliva showed mean SBS of 9.03 ± 1.14 Mpa. The difference between both the groups was statistically significant, as confirmed by paired t-test (P < 0.05). In-Group I, ARI scores showed that more than half of the adhesive was left over the tooth surface, and Group II showed that there was no or insignificant amount of adhesive left over the tooth surface. Chi-square test revealed significant difference in debonding characteristics among the test groups of ARI (P < 0.05). Failure occurred mainly in resin- bracket base and resin - adhesive interfaces (χ² = 10.04, df = 3, P = 0.031).

CONCLUSION

Moisture insensitive primer is effective in the presence/absence of moisture and has shown SBS value of more than 7.8 Mpa as stated by Reynolds, hence material is suitable for clinical use.

Shear bond strength of orthodontic attachments bonded to impacted teeth under in vivo and in vitro conditions

OBJECTIVES

To evaluate and compare the shear bond strength (SBS) of stainless steel and gold-plated attachments to impacted lower third molars in vivo and in vitro with a light-cured orthodontic resin.

SETTING AND SAMPLE POPULATION

Sixteen patients with bilaterally full soft tissue impaction of lower third molars were recruited on a voluntary basis from an oral and maxillofacial surgery department.

MATERIALS AND METHODS

A split-arch technique was used. Following surgical exposure of the crown, the tooth was luxated but not extracted. Then, two attachments (one stainless steel button and one gold-plated eyelet) were bonded to the labial enamel surface of the loosened tooth. Five minutes later, the luxated tooth was removed from its socket. In each patient, the impacted tooth on the other side was extracted, and attachments were bonded in vitro. The SBSs of the attachments were evaluated. For comparison, analysis of variance and multiple range tests were used (α = 0.05).

RESULTS

Statistically significant differences were evident in attachment adhesion to the impacted tooth surfaces among the four groups (p < 0.001). Superior SBS values were obtained for stainless steel button groups bonded in vitro. The mean bond strengths of the groups bonded in vitro were better than those of the same groups bonded in vivo.

CONCLUSIONS

Although the in vitro-bonded groups showed higher SBS values, adequate bond strength is possible with stainless steel buttons bonded in vivo.

CO2 laser debonding of a ceramic bracket bonded with orthodontic adhesive containing thermal expansion microcapsules

We have been studying an easy bracket debonding method using heating of an orthodontic adhesive containing thermal expansion microcapsules. However, heating with a high-temperature heater brings obvious risks of burns around the oral cavity. Thus, we examined safer and more effective bracket debonding methods. The purpose of this in vitro study was to examine the reduction in debonding strength and the time taken using a bracket bonded with an orthodontic adhesive containing thermal expansion microcapsules and a CO2 laser as the heating method while maintaining safety. Ceramic brackets were bonded to bovine permanent mandibular incisors using bonding materials containing various microcapsule contents (0, 30, and 40 wt%), and the bond strengths were measured after laser irradiation for 4, 5, and 6 s and compared with nonlaser-treated groups. Subsequently, the temperature in the pulp chamber during laser irradiation was measured. After laser irradiation for 5 or 6 s, the bond strengths of the adhesive containing 40 wt% microcapsules were significantly decreased to ∼0.40 - 0.48-fold (4.6-5.5 MPa) compared with the nonlaser groups. The mean temperature rise of the pulp chamber was 4.3 °C with laser irradiation for 6 s, which was less than that required to induce pulp damage. Based on these results, we conclude that the combined use of a CO2 laser and an orthodontic adhesive containing thermal expansion microcapsules can be effective and safe for debonding ceramic brackets with less enamel damage or tooth pain.

A comparative evaluation of the retention of metallic brackets bonded with resin-modified glass ionomer cement under different enamel preparations: A pilot study

Introduction:

For orthodontists, the ideal bonding material should be less moisture-sensitive and should release fluoride, thereby reducing unfavorable iatrogenic decalcification. Resin-Modified Glass Ionomer Cements (RMGICs), due to their ability to bond in the presence of saliva and blood can be a very good bonding agent for orthodontic attachments especially in the areas of mouth, which are difficult to access. Moreover, their fluoride releasing property makes them an ideal bonding agent for patients with poor oral hygiene. However, their immediate bond strength is said to be too low to immediately ligate the initial wire, which could increase the total number of appointments. The effect of sandblasting and the use of sodium hypochlorite (NaOCL) on the immediate bond failure of RMGIC clinically have not been reported in the literature until the date. This investigation intended to assess the effect of sandblasting (of the bracket base and enamel) and NaOCL on the rate of bond failure (with immediate ligation at 30 min) of Fuji Ortho LC and its comparison with that of conventional light cured composite resin over a period of 1 year.

Materials and Methods:

400 sample teeth were further divided into 4 groups of 100 each and bonded as follows: (1) Group 1: Normal metallic brackets bonded with Fuji Ortho LC. (2) Group 2: Sandblasted bracket base and enamel surface, brackets bonded with Fuji Ortho LC. (3) Group 3: Deproteinized enamel surface using sodium hypochlorite and brackets bonded with Fuji Ortho LC. (4) Group 4: Normal metallic bracket bonded with Transbond XT after etching enamel with 37% phosphoric acid. This group served as control group.

Results and Conclusion:

Results showed that sandblasting the bracket base and enamel, can significantly reduce the bond failure rate of RMGIC.

Comparison of shear bond strength of hydrophilic bonding materials: an in vitro study

AIM

The aim of this study was to evaluate and compare the shear bond strength of hydrophilic materials like Transbond MIP with Assure-fluoride releasing light cure sealant paste system (Reliance orthodontic product), Enhance Lc-adhesion booster (Reliance Orthodontics) Prime and Bond NT-one step adhesive with nanotechnology (Dentsply Product India) with Transbond XT as the control group.

MATERIALS AND METHODS

The study was conducted on 180 extracted human premolar teeth which were divided into five main groups. Each group contained 36 teeth, which were further subdivided into three subgroups containing 12 teeth. The teeth were bonded in three different surface environments namely dry, contaminated with artificial saliva and reprimed after contamination with artificial salvia. The brackets were bonded and cured. The shear bond strength was tested using Instron universal testing machine (4501).

RESULTS

The results were subjected to statistical analysis like 3 factorial ANOVA and compared to post-hoc using the Student Newman levels test. The residual resin on the tooth surface after debonding was evaluated with adhesive remnant index.

CLINICAL SIGNIFICANCE

The results revealed that in situations in which moisture contamination is critical there is distinct advantage in using hydrophilic primers.

The influence of adhesives and the base structure of metal brackets on shear bond strength

OBJECTIVE

The objective of this study was to investigate the shear bond strength of compound made of tooth enamel, adhesive, and brackets for certain material combinations according to the DIN 13990-2 standard.

MATERIALS AND METHODS

We examined a combination of the following materials on permanent bovine incisors: (1) adhesives: Light Bond™ and Phase II® (both produced by Reliance Orthodontic Products, Itasca, IL, USA), Transbond XT™ (3M Unitek, Monrovia, CA, USA), (2) brackets: Carriere®, Euro Midi Classic, Midi Low Friction (all from Ortho Organizers, Carlsbad, CA, USA). The discovery® bracket (Dentaurum, Ispringen, Germany) served as the reference. According to the DIN standard, the teeth were embedded, adhesive was applied and they were then put into storage. This was followed by shear tests in a material testing machine with the shear force acting directly on the bracket base in the occlusal-gingival direction. Finally, the Adhesive Remnant Index was determined.

RESULTS

We observed the greatest shear bond strength (mean value) from the combination of Carriere® and Transbond XT™ (17.4 N/mm(2)), and the lowest from the combination of Euro Midi Classic and Phase II® (12.8 N/mm(2)). There were significant differences in the various material combinations. The values obtained from the measurements of discovery® together with Transbond XT™ agreed very well with the results of previous investigations.

CONCLUSION

The combinations of brackets and adhesives investigated in this study according to DIN standard 13990-2 provided a satisfactory result for clinical use.

Finite element sub-modeling analyses of damage to enamel at the incisor enamel/adhesive interface upon de-bonding for different orthodontic bracket bases

This study investigates the micro-mechanical behavior associated with enamel damage at an enamel/adhesive interface for different bracket bases subjected to various detachment forces using 3-D finite element (FE) sub-modeling analysis. Two FE macro-models using triangular and square bracket bases subjected to shear, tensile and torsional de-bonding forces were established using μCT images. Six enamel/adhesive interface sub-models with micro- resin tag morphology and enamel rod arrangement were constructed at the corresponding stress concentrations in macro-model results. The boundary conditions for the sub-models were determined from the macro-model results and applied in sub-modeling analysis. The enamel and resin cement stress concentrations for triangular and square bases were observed at the adhesive bottom towards the occlusal surface under shear force and at the mesial and distal side planes under tensile force. The corresponding areas under torsional force were at the three corners of the adhesive for the triangular base and at the adhesive bottom toward/off the occlusal surface for the square base. In the sub-model analysis, the concentration regions were at the resin tag base and in the region around the etched holes in the enamel. These were perfectly consistent with morphological observations in a parallel in vitro bracket detachment experiment. The critical de-bonding forces damaging the enamel for the square base were lower than those of the triangular base for all detached forces. This study establishes that FE sub-modeling can be used to simulate the stress pattern at the micro-scale enamel/adhesive interface, suggesting that a square base bracket might be better than a triangular bracket. A de-bonding shear force can detach a bracket more easily than any other force with a lower risk of enamel loss.

Effect of Saliva Contamination and Decontamination on Bovine Enamel Bond Strength of Four Self-etching Adhesives

Salivary contamination before and after priming could significantly reduce the enamel bond strength of self-etching adhesives. Proper isolation should be performed before and during application of the adhesives and placement of the resin composite. Thorough water-spraying could significantly improve the μTBS of saliva-contaminated enamel.

Shear bond strength of orthodontic brackets bonded with different self-etching adhesives

INTRODUCTION

The purpose of this study was to compare the shear bond strength (SBS) of orthodontic brackets bonded with 4 self-etching adhesives.

METHODS

A total of 175 extracted premolars were randomly divided into 5 groups (n = 35). Group I was the control, in which the enamel was etched with 37% phosphoric acid, and stainless steel brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif). In the remaining 4 groups, the enamel was conditioned with the following self-etching primers and adhesives: group II, Transbond Plus and Transbond XT (3M Unitek); group III, Clearfil Mega Bond FA and Kurasper F (Kuraray Medical, Tokyo, Japan); group IV, Primers A and B, and BeautyOrtho Bond (Shofu, Kyoto, Japan); and group V, AdheSE and Heliosit Orthodontic (Ivoclar Vivadent AG, Liechtenstein). The teeth were stored in distilled water at 37 degrees C for 24 hours and debonded with a universal testing machine. The adhesive remnant index (ARI) including enamel fracture score was also evaluated. Additionally, the conditioned enamel surfaces were observed under a scanning electron microscope.

RESULTS

The SBS values of groups I (19.0 +/- 6.7 MPa) and II (16.6 +/- 7.3 MPa) were significantly higher than those of groups III (11.0 +/- 3.9 MPa), IV (10.1 +/- 3.7 MPa), and V (11.8 +/- 3.5 MPa). Fluoride-releasing adhesives (Kurasper F and BeautyOrtho Bond) showed clinically acceptable SBS values. Significant differences were found in the ARI and enamel fracture scores between groups I and II.

CONCLUSIONS

The 4 self-etching adhesives yielded SBS values higher than the bond strength (5.9 to 7.8 MPa) suggested for routine clinical treatment, indicating that orthodontic brackets can be successfully bonded with any of these self-etching adhesives.

Examination of six orthodontic adhesives with electron microscopy, hardness tester and energy dispersive X-ray microanalyzer

OBJECTIVE

To examine the ultrastructure of six light-cure orthodontic adhesives with scanning electron microscope (SEM) and transmission electron microscope (TEM), microhardness tester, and energy dispersive X-ray microanalyzer (EDX).

MATERIALS AND METHODS

The orthodontic adhesives evaluated were Transbond XT, Light Bond, BeautyOrtho Bond, Kurasper F, Heliosit Orthodontic, and Salivatect. Specimens of each adhesive were carefully prepared for observation under SEM and TEM. Furthermore, the Vickers hardness was tested, and the adhesives were evaluated with EDX.

RESULTS

SEM and TEM images illustrated great diversity of the adhesives ultrastructure. The Vickers hardness test showed significant differences among all the adhesives (except Transbond XT and Salivatect). Although some similar elements were detected with EDX, the concentration was different in each adhesive.

CONCLUSION

Orthodontic brackets can be bonded to the enamel surface with the adhesives available on the market. However, orthodontists might achieve better results identifying their properties and compositions.

Artificial saliva contamination effects on bond strength of self-etching primers

OBJECTIVE

To test the hypothesis that there is no difference in the bond strength with or without contamination with artificial saliva when using two different self-etching primers (Transbond Plus and iBond) in comparison with a conventional acid-etching method (37% phosphoric acid and Transbond XT) for bonding of orthodontic brackets.

MATERIALS AND METHODS

One hundred fifty extracted human premolars were randomly allocated to six different groups, with 25 teeth in each group. Orthodontic metal brackets (APC II, Victory Twin 22 UNIV) were used. For contamination, a saliva replacement (Ptyalin) was applied. After contamination the surface was air-dried for 5 seconds and the bonding procedure continued. The bonded teeth were stored in deionized water at 37 degrees C for 30 days and then thermocycled for 24 hours before debonding with a universal testing machine. The load was recorded at bond failure. The location of adhesive failure was determined under magnification using the adhesive remnant index (ARI).

RESULTS

Clinically acceptable bond strengths were found for all primers used in this study. The contamination by saliva significantly decreased the bond strength when using the conventional acid-etching method (t = 0.0001). Self-etching primers were less influenced by saliva contamination. There was no significant difference in the ARI score among the groups (P > .05).

CONCLUSIONS

Saliva contamination significantly decreased the bond strength when the conventional acid-etching method was used. The self-etching primers were influenced the least. The bond strengths achieved for the self-etching primers and the conventional etching method after saliva contamination were not significantly different.