Shear Bond Strength of Ceramic Brackets with Different Base Designs: Comparative In-vitro Study

Shear bond strength of three different metal bracket base designs on human premolars: An in vitro comparative study

Background

Adequate bracket-enamel bonding is critical to prevent detachment during orthodontic treatment and minimize any potential delay in results. The aim was to compare the shear bond strength of three metal bracket base designs: laser-structured base, mesh base, and retention grooves base.

Material and Methods

In this experimental in vitro study, 54 human premolars were immersed for one week in 0.1% thymol solution, then placed in distilled water with weekly replacement until the start of the study. The premolars were cemented with brackets of varying base designs: A. Discovery® Smart (laser structured), B. Mini Master® Series (base with mesh), and C. Roth Max (base with retention grooves). All brackets were cemented using TransbondTM XT. A universal testing machine was used to evaluate the shear bond strength at a crosshead speed of 0.75 mm/min. Welch's one-factor ANOVA with robust variance and Tukey's post hoc test were used to compare means, with a significance level of p<0.05.

Results

The average shear bond strength values were for the bracket with laser-structured base (14.78 ± 5.79 MPa), the bracket with mesh base (9.64 MPa ± 2.54 MPa) and the bracket with retention groove base (15.38 MPa ± 2.67 MPa). It was found that brackets with mesh bases had significantly lower shear bond strength than brackets with laser-structured bases (p=0.001) and brackets with retention grooves bases (p<0.001). No significant differences were observed between the latter two types of brackets (p = 0.893).

Conclusions

The bracket base design influenced in vitro shear bond strength with significantly higher values observed for Roth Max and Discovery® Smart brackets compared to Mini Master® Series brackets. Key words:Shear strength, laser-structured bracket, bracket with mesh base, bracket with retention groove base.

Effect of Different Types of Adhesive Agents on Orthodontic Bracket Shear Bond Strength: A Cyclic Loading Study

Bracket failure is one of the most important problems encountered during fixed orthodontic treatment. For this reason, different types of adhesive agents have been developed over the years. Consequently, the aim of this study was to evaluate the shear bond strength of brackets bonded to teeth etched with a conventional acid etching method in a laboratory environment by using different types of adhesive agents and comparing the number of shear strokes. Sixty human maxillary premolars were divided into three groups and Gemini stainless steel metal brackets (3M Unitek, Monrovia, CA, USA) were bonded to all teeth. In Group 1, Transbond™ XT Primer (3M Unitek, Monrovia, CA, USA) and Transbond™ XT Light Cure Adhesive Paste composite (3M Unitek, Monrovia, CA, USA) were used. In Group 2, BracePaste® MTP Primer (American Orthodontics, Sheboygan, CA, USA) and BracePaste® Adhesive composite (American Orthodontics, Sheboygan, WI, USA) were used. In Group 3, Ortho Solo™ Primer (Ormco, Orange, CA, USA) and Grengloo™ Adhesive composite (Ormco, Brea, CA, USA) were used. The samples were subjected to a shear test with a closed-loop controlled, low-cycle fatigue machine with a capacity of 10 N and a crosshead speed of 300 mm/min. The number of shear strokes of the brackets was recorded. According to the Kruskal−Wallis and Mann−Whitney U tests performed on the data obtained, statistically significant differences were found between the groups in terms of the numbers of shear strokes (p < 0.05). Significantly higher numbers of shear strokes and higher shear bond strengths were observed in Group 3 compared with Group 1 and Group 2 (p < 0.05). There was no statistically significant difference between the numbers of shear strokes for Group 1 and Group 2 samples (p > 0.05). To conclude the study, it was observed that the type of adhesive used had an effect on the bond strength of the bracket and that the Grengloo™ adhesive agent showed higher shear bond strength. It was observed that BracePaste® Adhesive and Transbond™ XT Light Cure Adhesive Paste adhesive agents had similar shear bond strengths.

Shear Bond Strength and Bracket Base Morphology of New and Rebonded Orthodontic Ceramic Brackets

The objectives of this study were to (1) to evaluate the shear bond strength (SBS) of two ceramic brackets when new and when rebonded following various bracket base conditioning methods, and (2) to determine bond failure mode relative to bracket base morphology. 100 Symetri Clear^TM (SC) and 100 Radiance Plus^® (RP) ceramic brackets were bonded to bovine incisors and divided into five groups: one group served as controls and four had brackets rebonded following conditioning by: no surface treatment, sealant, sandblasting, and flame then steam. SBS, adhesive remnant index, and bracket base morphology were evaluated. SBS showed no statistical difference between new and rebonded with no surface treatment or sealant (SC brackets) and with sealant or flame and steam (RP brackets). When comparing SC to RP, SBS was higher with SC, no surface treatment, and sandblasted groups. All groups had varying amounts of adhesive left on the tooth, with the sandblasted group having the most. SEM analysis showed that sandblasting damaged the retention features of bracket bases. In conclusion, when rebonded, the SBS of SC brackets that had no surface treatment and both SC and RP brackets that had sealant showed no significant differences to new brackets. Sandblasting damaged the retention features of SC and RP bracket bases, resulting in low SBS.

Orthodontic Bracket Removal Using LASER-Technology-A Short Systematic Literature Review of the Past 30 Years

Background: Since fixed orthodontic treatment is widely spread and one of its inconveniences is bracket removal, as this affects enamel integrity as well as being a cause of discomfort to the patient, studies have searched for the most adequate bracket removal technique, many of them focusing on using laser-technology. Methods: Our review focused on articles published investigating methods of orthodontic bracket removal using laser technology in the last 30 years. Results: 19 relevant studies were taken into consideration after a thorough selection. Different types of laser devices, with specific settings and various testing conditions were tested and the investigators presented their pertinent conclusions. Conclusions: Most studies were performed using ceramic brackets and the best results in terms of prevention of enamel loss, temperature stability for the tooth as well as reduced chair time were obtained with Er:YAG lasers.

Challenges, standards and prospects in the therapy of orthodontic traction of impacted maxillary canine: A surgical phase

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Physical and chemical mechanisms involved in adhesion of orthodontic bonding composites: in vitro evaluations

Background

Bond strength of orthodontic composite is strongly influenced by molecular and structural mechanisms. Aim of this in vitro study was to compare bond strength of light-cure orthodontic composites by measuring debonding forces and evaluating locations of bond failure. Investigations on chemical compositions clarified adhesive behaviors and abilities, exploring effects of ageing processes in this junction materials.

Methods

Twelve enamel discs, from human premolars, were randomly coupled to one orthodontic adhesive system (Transbond XT™ 3 M UNITEK, USA, Light-Cure Orthodontic Paste, LEONE, Italy and Bisco Ortho Bracket Paste LC, BISCO, Illinois) and underwent to Shear Bond Strength test. Metallic brackets were bonded to twenty-seven human premolar, with one of the adhesive systems, to quantify, at FE-SEM magnifications, after debonding, the residual material on enamel and bracket base surfaces. Raman Spectroscopy analysis was performed on eight discs of each composites to investigate on chemical compositions, before and after accelerated aging procedures in human saliva and sugary drink.

Results

Orthodontic adhesive systems showed similar strength of adhesion to enamel. The breakage of adhesive-adherent bond occurs in TXT at enamel-adhesive interface while in Bisco and Leone at adhesive-bracket interface. Accelerated in vitro aging demonstrated good physical–chemical stability for all composites, Bisco only, was weakly contaminated with respect to the other materials.

Conclusion

A similar, clinically adequate and acceptable bond strength to enamel for debonding maneuvers was recorded in all orthodontic adhesive systems under examination. No significant chemical alterations are recorded, even in highly critical situations, not altering the initial mechanical properties of materials.

Effects of plastic bracket primer on the shear bond strengths of orthodontic brackets

Background/purpose

To assess the usefulness of plastic bracket primer (PBP) for improving the bond strength of plastic brackets (PBs) using three types of orthodontic brackets, including PBs, metal brackets (MBs), and ceramic brackets (CBs).

Materials and methods

A total of 162 premolars were gathered and divided equally into six groups of 27. Three groups were tested with the application of PBP (PB+, MB+, and CB+), and three groups were tested without primer (groups PB-, MB-, and CB-). All the groups were bonded using BeautiOrtho Bond II self-etching adhesive. The shear bond strength (SBS) was measured and the bond failure mode was evaluated using the adhesive remnant index after debonding.

Results

There were significant differences in the mean SBS between groups PB-, MB and CB-, between PB+ and CB+, and between MB+ and CB+. Group PB + had a significantly higher mean SBS than group PB-. The occurrence of bond failure at the enamel and adhesive interface was more frequent in groups PB+ and CB- than in group PB-; and in groups PB+ and CB + than in group MB+.

Conclusion

Plastic bracket primer can increase the bond strength of PBs to the level of metal brackets, but not to the level of ceramic brackets.

Evaluation of Enamel Topography after Debonding Orthodontic Ceramic Brackets by Different Er,Cr:YSGG and Er:YAG Lasers Settings

In the last decade, the success of lasers in simplifying many dental procedures has heightened the need for research in the orthodontic field, in order to evaluate the benefits of laser-assisted ceramic brackets debonding. Conventional ceramic brackets removal delivers a high shear bond strength (SBS), which might lead to enamel damage. Nowadays, debonding ceramic brackets by Er:YAG laser seems a viable alternative technique; however, there is no data on the use of Er,Cr:YSGG in the literature. We aimed to evaluate the difference in enamel topography derived from different erbium laser settings used during debonding. One hundred and eighty bovine incisors teeth were randomly divided into fifteen experimental groups, according to different erbium laser settings using scanning methods. SBS testing was performed after debonding; stereomicroscopic and SEM analyses were done after cleaning the remaining adhesive so as to assess the incidence of enamel microcracks formation and enamel loss. There were no statistically significant differences between the proportions of teeth with normal enamel topography within the control group when compared with any of the Er:YAG groups. However, the proportion of teeth with a normal enamel topography in Er,Cr:YSGG was 4 W/20 Hz (83.3%) and in Er:YAG was 5 W/20 Hz (91.7%), which was statistically significantly higher than the control group (41.7%). The selection of erbium lasers' optimal parameters during debonding influences the enamel topography. When considering the evaluation of both microscopic and statistical analyses, irradiation by Er:YAG (120 mJ/40 Hz) displayed a significant reduction in microcracks compared with conventional debonding, even though some microstructural changes in the enamel could be noted. Er,Cr:YSGG (4 W/20 Hz) respected the enamel topography the most out of the studied groups.

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.

Priming and bonding metal, ceramic and polycarbonate brackets

Objective: To investigate if primers can be used to modify bonding characteristics of orthodontic brackets.

Materials and methods: Stainless steel, zirconia-alumina ceramic and polycarbonate brackets were bonded to enamel with and without universal and bracket material specific primers on the bracket base. Orthodontic adhesive cement (Transbond™XT) was used for bonding. The primers in each group (n = 10) were silane based (RelyX™ Ceramic Primer) and universal primer (Monobond Plus) for ceramic and metal brackets, and adhesive resin (Adper™ Scotchbond™ Multi-Purpose Adhesive) and composite primer (GC Composite Primer) for polycarbonate brackets. Controls with no primer were used for all bracket types. Teeth with bonded brackets were stored in distilled water in 37 °C for 7 days and debonded with static shear loading. Debonding forces were recorded and analyzed with ANOVA. Adhesive remnant index (ARI) was determined and enamel damage examined.

Results: The bond strength without primers was 8.14 MPa (±1.49) for metal, 21.9 MPa (±3.55) for ceramic and 10.47 MPa (±2.11) for polycarbonate brackets (p < .05). Using silane as primer increased the bond strength of ceramic brackets significantly to 26.45 MPa (±5.00) (p < .05). ARI-scores were mostly 2–3 (>50% of the adhesive left on the enamel after debonding), except with silane and ceramic brackets, ARI-score was mostly 0–1 (>50% of the adhesive left on the bracket). Debonding caused fractured enamel in four specimens with ceramic brackets.

Conclusions: Bond strength was highest for ceramic brackets. Silane primer increased bond strength when used with ceramic brackets leading to enamel fractures, but otherwise primers had only minor effect on the bond strength values.

Shear bond strength of a flash-free orthodontic adhesive system after thermal aging procedure

Background

The aim of this study was to compare the shear bond strength (SBS) of a flash-free and precoated orthodontic adhesive with a compomer orthodontic adhesive before and after thermocycling. The adhesive remnant index (ARI) was also determined for both adhesives.

Material and Methods

The adhesive remnant index (ARI) was also determined for both adhesives. Material and Methods: A total of 120 human premolars were randomly divided into two groups (n=60) according to the orthodontic adhesive used: APC Flash-Free Adhesive Coated Appliance System (APC FF) or Transbond PLUS Color Change Adhesive (TP), as control. A SBS test was performed and ARI value for each specimen was also assessed. Results were analyzed by two-way ANOVA and Tukey's Chi-square test (p<0.05).

Results

SBS values were significantly influenced by thermocycling (p<0.01). Neither the orthodontic adhesive nor the interaction between adhesive and thermocycling statistically affected SBS results (p>0.05).

Conclusions

APC FF and TP showed similar bond strength results. Thermocycling induced a significant decrease in SBS values for the two adhesives tested, without differences between 10,000 and 20,000 thermal cycles. Moreover, APC FF left less adhesive remnants on the enamel compared to TP. Key words:APC Flash-Free, APC cement, aging, orthodontics, resin cements.

A comparative assessment of bracket survival and adhesive removal time using flash-free or conventional adhesive for orthodontic bracket bonding: A split-mouth randomized controlled clinical trial

OBJECTIVES

To compare bracket survival and adhesive removal time between a flash-free and a conventional adhesive for orthodontic bracket bonding.

MATERIALS AND METHODS

Forty-five consecutive patients had their maxillary incisors, canines, and premolars bonded with ceramic brackets using a flash-free adhesive (APC Flash-Free Adhesive, 3M Unitek, Monrovia, Calif) on one side and a conventional adhesive (APCII Adhesive, 3M Unitek) on the other side. The side allocation was randomized. Bracket failure was recorded at 4-week intervals. The adhesive remnant index (ARI) was scored on debond and adhesive removal timed to the nearest second. The primary outcome was adhesive removal time per quadrant. Secondary outcomes were bracket failure rate, time to first-time failure of a bracket, and ARI score on debond. Paired t-tests were used to compare adhesive removal times and ARI scores between the adhesives with P < .05 considered statistically significant.

RESULTS

Bracket failure rates were 4.3% for the flash-free adhesive and 1.9% for the conventional adhesive, with mean times to first-time failure of 31 weeks for the flash-free adhesive and 42 weeks for the conventional adhesive; neither failure rates nor times to first failure were significantly different. Although the flash-free adhesive left significantly more adhesive on the tooth surface after debonding, the adhesive removal times were 22.2% shorter than with the conventional adhesive.

CONCLUSIONS

Bracket survival with the flash-free adhesive was equivalent to the conventional adhesive when ceramic brackets were bonded. Adhesive removal was significantly faster when using the flash-free adhesive, which may result in time savings of more than 20% compared with the conventional adhesive.

A Comparative Evaluation of Canine Retraction Using Ceramic Bracket and Ceramic Bracket with Metal Slot with Conventional Preadjusted Edgewise Appliance Bracket Systems: A Clinical Study

Aims and Objectives

The introduction of ceramic brackets was a much-heralded development in the field of orthodontics. However, the increased frictional resistance with these brackets led to the development of ceramic brackets with metal slots, which claimed to combine the esthetics of ceramic brackets with the low frictional resistance of metal brackets. Hence, this study was undertaken to evaluate the rate of canine retraction and the amount of anchor loss while using ceramic brackets and ceramic brackets with metal slots and with conventional preadjusted edgewise appliance (PEA) metal brackets.

Materials and Methods

The patient sample consists of 12 patients. Six patients received ceramic brackets on one canine and conventional PEA metal brackets on the opposite canine within the same arch. The other six patients received ceramic brackets with metal slot on one canine and conventional PEA metal brackets on the opposite canine within the same arch. Unpaired t-test was used to analyze the data using SPSS version 20 (3M Unitek, Bangalore, Karnataka, India). The rate of retraction was calculated for individual canine retraction after initial leveling and aligning. Anchor loss was also calculated using the pterygoid vertical to the mesiobuccal cusp of the upper first molar on the lateral cephalograms.

Results

The result of this study showed that the difference in the rate of retraction between ceramic brackets with metal slot and conventional PEA metal brackets and ceramic bracket while clinically significant was not statistically significant. The difference in the amount of loss of anchorage of both the groups was not statistically significant.

Conclusions

Incorporation of the metal slot in ceramic brackets has reduced frictional resistance for more efficient and desired tooth movement. Ceramic brackets with metal slot generate lower frictional forces than ceramic brackets but higher than conventional PEA metal brackets.

Decellularized Hydrogels in Bone Tissue Engineering: A Topical Review

Nowadays, autograft and allograft techniques represent the main solution to improve bone repair. Unfortunately, autograft technique is expensive, invasive and subject to infections and hematoma, frequently affecting both donor sites and surgical sites. A recent advance in tissue engineering is the fabrication of cell-laden hydrogels with custom-made geometry, depending on the clinical case. The use of ECM (Extra-Cellular Matrix)-derived Hydrogels from bone tissue is the new opportunity to obtain good results in bone regeneration. Several micro-engineering techniques and approaches are available to fabricate different cell gradients and zonal structures in hydrogels design, in combination with the advancement in biomaterials selection. In this review, we analyse the stereolithografy, the Bio-patterning, the 3D bioprinting and 3D assembly, the Laser-Induced Forward Transfer Bioprinting (LIFT), the Micro-extrusion bioprinting, the promising Electrospinning technology, the Microfluidics and the Micromolding. Several mechanical properties are taken into account for bone regeneration scaffolds. However, each typology of scaffold presents some advantages and some concerns. The research on biomaterials is the most promising for bone tissue engineering: the new biomimetic materials will allow us to obtain optimal results in the next clinical application of basic research.

Effects of femtosecond laser and other surface treatments on the bond strength of metallic and ceramic orthodontic brackets to zirconia

Femtosecond laser has been proposed as a method for conditioning zirconia surfaces to boost bond strength. However, metallic or ceramic bracket bonding to femtosecond laser-treated zirconia surfaces has not been tested. This study compared the effects of four conditioning techniques, including femtosecond laser irradiation, on shear bond strength (SBS) of metallic and ceramic brackets to zirconia.Three hundred zirconia plates were divided into five groups: 1) control (C); 2) sandblasting (APA); 3) silica coating and silane (SC); 4) femtosecond laser (FS); 5) sandblasting followed by femtosecond laser (APA+SC). A thermal imaging camera measured temperature changes in the zirconia during irradiation. Each group was divided into 2 subgroups (metallic vs ceramic brackets). SBS was evaluated using a universal testing machine. The adhesive remnant index (ARI) was registered and surfaces were observed under SEM. Surface treatment and bracket type significantly affected the bracket-zirconia bond strength. SBS was significantly higher (p<0.001) for ceramic brackets in all groups (APA+FS > APA > FS > SC > control) than metallic brackets (APA+FS > FS > SC > APA > control). For metallic brackets, groups SC (5.99 ± 1.86 MPa), FS (6.72 ± 2.30 MPa) and APA+FS (7.22 ± 2.73 MPa) reported significantly higher bond strengths than other groups (p < 0.05). For ceramic brackets, the highest bond strength values were obtained in groups APA (25.01 ± 4.45 MPa), FS (23.18 ± 6.51 MPa) and APA+FS (29.22 ± 8.20 MPa).Femtosecond laser enhances bond strength of ceramic and metallic brackets to zirconia. Ceramic brackets provide significantly stronger adhesion than metallic brackets regardless of the surface treatment method.