Steel Brackets Research Articles

In vitro determination of genotoxicity and cytotoxicity induced by stainless steel brackets with and without surface coating in cultures of oral mucosal cells

BackgroundOrthodontics is a speciality of dentistry that uses a plethora of devices made from myriad materials to manage various malocclusions. Prolonged contact of orthodontic appliances with oral tissues can lead to cellular damage, highlighting the need for biocompatible materials to mitigate health risks.ObjectivesTo analyze the genotoxicity and cytotoxicity produced by metal brackets and coated metallic brackets with polymeric and nanoparticle coatings in oral mucosal cells.Materials & methodsThe current study compares the toxicity of 3 different types of orthodontic brackets with control groups of oral mucosal cells. Each of the three treatment groups consisted of 10 samples of orthodontic brackets: stainless steel brackets(Group 1), nanoparticle-coated brackets(Group 2), and polymeric-coated brackets(Group 3) exposed to corrosion eluates employing an oral biomimicry model. Two types of oral mucosal cells- Human Gingival Fibroblasts and Buccal Epithelial Cells were used to study the cytotoxic and/or genotoxic effects of the elutes. Intergroup comparisons were conducted using one-way analysis of variance, while scanning electron microscopy evaluated surface characteristic.ResultsThe interaction between metal ions and oral mucosal cells showed no statistically significant difference for toxicity assays between the three groups(p > 0.005). However, polymeric and nanoparticle-coated groups showed reduced cellular differentiation when compared with conventional stainless-steel brackets.ConclusionThis in-vitro study shows that polymeric or nanoparticle coating of conventional metal brackets aids in enhancing corrosion-resistant characteristics of orthodontic appliances and reduces the toxic oral environment created by metal release in the oral cavity.

Experimental study on mechanical properties of pin-trunnion connection nodes of temporary steel brackets for elevated bridges

Currently, the pin connection test exists mainly for unidirectional force loading, while the pin connection of a temporary steel bracket applied to elevated bridges is for bi-directional force. The damage mechanism of the pin connection with bi-directional force is not yet fully understood in research. The effect of the loading direction, single-hole plate end distance and unilateral width ratio a/b, ear plate thickness ratio t1/2 t2, and ear plate shape on the mechanical properties of the pin connection need to be considered. In this study, destructive static loading tests were conducted on eight groups of double-hole pin connections, and the damage mode, bearing capacity, deformation, and strain of the pin connections were determined. The results show that the thickness of the trunnion plate primarily controls the damage mode of the pinned connection and the ratio is smaller for single-trunnion plate damage, which can achieve larger bearing capacity and deformation. The ratio of the end distance of the monocore plate to the width of the single side primarily controls the damage location of the monocore plate, and the ratio varies from large to small, gradually causing tensile damage to the side section, end cleavage damage, and end shear damage. The loading direction has a minor effect on the mechanical properties of the pin connection; however, the tensile deformation is significantly larger than the compressive deformation. By chamfering, the M shape is properly adjusted to optimize the shape of the double trunnion plate, which does not reduce the load-carrying capacity and deformation of the pin connection and can reduce the amount of steel used by 10 %. A comparative analysis of the change in the ear-plate shape before and after the open ear-plate test, determination of the cross-sectional damage location and effective calculation distance b1, and improvement and derivation of a practical method for calculating the load-carrying capacity for engineering are performed, at the same time, it can be applied to projects of different spans, which can greatly improve construction efficiency and reduce labor costs.

Evaluation of Mechanical and Elemental Properties of Bioceramic-Coated Orthodontic Brackets and Enamel Surface.

The aim is to coat orthodontic brackets with two different bioactive materials and to compare the mechanical and morphological properties of coated brackets and tooth surfaces. A total of 120 stainless steel brackets were divided equally into three groups, that is, the uncoated brackets and nanohydroxyapatite (nHA)-coated, and nanobioactive glass (nBG)-coated brackets using a spin coater machine. The brackets were bonded on the enamel surface and underwent remineralization/demineralization cycles for days 1, 7, 14, and 30. At each time interval, the bond strength of the brackets was assessed using mechanical loading. An optical and scanning electron microscope (SEM) were used for surface evaluation, and the adhesive remanent index (ARI) values were obtained and quantified. One-way analysis of variance using Tukey's test was used to compare the differences among the groups. A uniform distribution of nanoparticles occurred on the surfaces of brackets. The shear bond strength (SBS) showed no significant differences in any tested groups on days 1, 7, and 14. However, control and nBG showed a significant difference from nHA at day 30. On days 7, 14, and 30, the nHA group showed the highest SBS values among the groups. For ARI, most samples showed an adhesive nature of failure at the enamel-brackets interface. The images confirmed the presence of coated particles on brackets and remnants of adhesives after SBS. This study confirmed that the nHA- and nBG-coated brackets have a high potential for application in orthodontics regarding structural and mechanical properties.

Efficiency of clear aligners with nickel titanium wires for treating mandibular incisor crowding.

Patients who are allergic to nickel, which is present in stainless steel brackets and wires, commonly utilise clear aligners. The objective of this research was to compare the management of mandibular incisor crowding with nickel titanium (NiTi) wires and clear aligners. A random division of forty participants into two groups of twenty samples each was made. Participants in group B received transparent aligners, whereas those in group A received NiTi arch wires. We assessed malocclusion using Little's irregularity index. A survey instrument was utilised to document the degree of discomfort. Patients were routinely recalled every one, two, and three months. The mean score for groups A and B was 2.86 mm and 2.88 mm at baseline, 1.71 mm and 1.52 mm at one month, 1.02 mm and 1.23 mm at two months, and 0.72 mm and 0.48 mm at three months, respectively. The difference wasn't that big (p > 0.05). In groups A and B, the mean change in Little's irregularity index score was 1.19 mm and 1.21 mm at one month, 0.55 mm and 0.51 mm at two months, and 0.26 mm and 0.45 mm at three months, respectively. The difference wasn't that big (p > 0.05). For groups A and B, the corresponding mean discomfort scores were 2.6 and 2.3 at baseline, 2.2 and 1.8 after one month, 1.6 and 1.5 at two months, and 1.1 and 0.9 at three months. Since p > 0.05, the difference was not significant. The results of this study showed that NiTi wires and clear aligners worked just as well to treat cases of mandibular anterior crowding.

A spectrophotometric analysis of copper and zinc released from stainless steel brackets coated with a combination of copper oxide and zinc oxide nanoparticles in artificial saliva

Nanocoating stainless steel orthodontic brackets with a combination of copper and zinc oxide nanoparticles might alter the quantity of ions released from them in saliva. The purpose of the study was to evaluate the quantity of copper and zinc ions released from stainless steel brackets coated with a combination of copper oxide and zinc oxide. Stainless steel orthodontic brackets (Ormco Mini -Diamond series 0.22” slot, MBT prescription) (ORMCO CORP Glendora, California, USA) (n= 15 in each group) were coated with nanoparticles of copper oxide (Group I) , zinc oxide (Group II) and a combination of copper oxide –zinc oxide (Group III) nanoparticles using a spray pyrolysis method . The quantity of copper and zinc ions released from these three groups of brackets, when stored in artificial saliva and intubated at 37 C was evaluated at 24hrs, 7th day, 14th day and 28th day using an atomic absorption spectrometer. The three groups of coated brackets released significantly more copper and zinc ions than the uncoated brackets. The copper oxide nanocoated and zinc oxide nano coated stainless steel orthodontic brackets released more copper and zinc ions when compared to the copper oxide - zinc oxide combination nanocoated orthodontic brackets and uncoated brackets. The highest surge of ion release was noted at the 7th day in all the three coated groups for both the ions evaluated. Brackets coated with a combination of copper oxide and zinc oxide nanoparticles demonstrated reduced levels of copper and zinc ion release in artificial saliva when compared to copper oxide nanocoated brackets and zinc oxide nanocoated brackets..

Torque expression of superelastic NiTi V-Slot and conventional stainless steel orthodontic bracket-archwire combinations - A finite element analysis

BackgroundTo investigate the torque expression of conventional stainless steel (SS) brackets in combination with rectangular SS archwires and nickel-titanium (NiTi) V-slot brackets in combination with V-shaped NiTi archwires using finite element analysis (FEA). MethodsCAD models were created for a conventional bracket and rectangular archwires with dimensions of 0.018″x0.025″ and 0.019″x0.025″, and for a V-slot bracket and V-shaped archwires with heights of 0.55 mm, 0.60 mm and 0.70 mm. FEA was performed using Ansys 2022R2 software to assess the forces and moments during simulated torsion of the archwires in the brackets between 0° and 25° with varying interbracket distances and free path lengths. ResultsThe V-slot bracket-archwire combination exhibited force transmission and moment generation within 1° of torsion. The transmissible force increased with the torsion angle, but showed an upper limit of about 13–14 Nmm. The SS bracket-archwire combination showed negligible forces and moments for simulated torsion between 0° and 15°. At torsions of 25°, moments of 12 Nmm and 14 Nmm occurred for the 0.018″x0.025″ and 0.019″x0.025″ archwire dimensions, respectively. ConclusionsThe V-slot bracket-archwire combination is effective in expressing torque and preventing both over- and under-activation. Conventional bracket-archwire combinations showed torsional losses due to play between 10 and 15°, depending on the dimensions of the respective archwire, and no upper torsional moment limit.

Experimental and FEM study on the feasibility of PBL connectors in the composite cable-pylon anchorage zone of cable-stayed bridge

This study investigates the joint between the steel wall plate and the concrete pylon wall in the cable-pylon anchorage zone of cable-stayed bridges, utilizing perfobond rib (PBL) connectors. Finite element analysis (FEM) was conducted on the steel wall plate-concrete joint under various conditions, including cable force, concrete shrinkage, overall warming, and overall cooling, with PBL connectors modeled as spring elements. The results indicate that vertical shear force in the PBL connectors peaks in the steel bracket web plates, with cable force and concrete shrinkage having the most significant impact on stress. Scaled-down local model tests and corresponding solid element FEM analysis were performed to evaluate the load performance of these joints. During tests, deformation between the steel plate and concrete wall remained minimal, and no cracks appeared under loads up to 1.7 times the design load. The ultimate load capacity was 2.9 times the design load, with failure occurring through pullout damage. FEM analysis showed good agreement with test results, and overall stress levels remained low, meeting design requirements. Material yielding only occurred in joint areas under large loads, confirming the feasibility of PBL connectors in composite cable-pylon anchorage zones.

Experimental and numerical study on mechanical properties of a modified type of energy-dissipative hold-down for CLT structures

The connections ensure lateral and shear resistance in CLT buildings, facilitating crucial interactions between walls and floors. CLT connectors are widely used at present and take strength as the control index, but they have poor energy dissipation performance and are not suitable for middle- and high-rise buildings in earthquake-prone zones. This study proposes a modified version of an existing energy dissipative hold-down connection that rectifies its flaws by incorporating innovative design and material solutions. An experimental study is conducted with quasi-static monotonic and reversed cyclic loading tests to investigate modified hold-down connection failure mechanisms and mechanical properties. Notable failure modes included steel rib ruptures and debonding between rubber and steel plate, with steel rib rupture as a dominant failure mechanism. Despite such failures, the connection maintained functionality, attributed to the effective bonding between the rubber and the steel bracket. The load-displacement curves of the hold-down exhibit a bi-linear pattern with the yielding point caused by the yielding of steel ribs. Almost all the specimens were classified as highly ductile, with ductility values exceeding 9.0 and an equivalent viscous damping ratio between 10 % and 18 %, indicating significant ductility and energy-dissipative capabilities. Furthermore, a simplified FEM model of the modified hold-down is established using ABAQUS software and validated against the experimental results. In addition, a parametric study was conducted to investigate the influences of modified design parameters on the mechanical properties and failure modes. The results of the comparison between the test and FEM model show the robustness of the proposed model in estimating the initial stiffness, post-yield stiffness, and yield force. Ultimately, the modified energy dissipation hold-down effectively rectifies former design flaws over its previous version, resulting in significantly improved performance, high energy dissipation capacity, and ductility by mitigating the brittle failures. This study provides a technical solution for future research to enhance the seismic resilience of modern high-rise CLT buildings through the real-world implementation of this type of modified hold-down connections.

Release of nickel and chromium ions from stainless steel brackets as a result of long-term exposure to commonly used toothpaste

Background: Brackets in fixed orthodontic appliances are mostly made from metal or stainless steel. Maintaining oral hygiene by brushing the teeth with toothpaste during orthodontic treatment is important. One of the ingredients in toothpaste, sodium fluoride, can cause degradation of the stainless-steel surface, which has the potential to corrode or release metal elements. Purpose: the purpose of this study is to describe the Nickel and chromium ion release of stainless-steel brackets against toothpaste use in orthodontic treatment by means of narrative review. Review: The main corrosion products of stainless-steel brackets are nickel and chromium. Toothpaste detergents contain sodium lauryl sulfate, which can cause the release of nickel ions due to the presence of sodium ions, which can trigger redox reactions. In addition, the fluoride content will combine with hydrogen to produce hydrofluoric acid, which can damage the oxide layer on orthodontic wires, resulting in the release of metal ions such as nickel and chromium. The effects of the release of these ions can be carcinogenic, cause hypersensitivity reactions, and cause cytotoxicity. Corrosion causes the dissolution of filler metal, resulting in weakened bracket material and increased friction, leading to delayed tooth movement. Conclusion: Toothpaste can affect the release of nickel and chromium ions in stainless steel brackets in the presence of sodium and fluoride.

Quantitative and qualitative analysis of metallic ion release of orthodontic brackets in three different pH conditions - An invitro study

BackgroundFluoridated mouth rinses improve anti-cariogenic environment but decrease oral pH below critical value, affecting orthodontic bracket surface topography and causing corrosive changes over prolonged use. This invitro study aimed to quantitatively and qualitatively assess the surface topography and metallic ion release of the stainless steel (SS) brackets at varying acidic and alkaline pH. Materials and methodsForty unused SS brackets were divided into four groups (Group A, B, C, D) and immersed for 48- hours in solutions of artificial saliva and sodium fluoride (0.2 %) mouth rinse at varying pH of 5.5,6.7,7 and 8. The surface morphologic changes were analyzed under scanning electron microscope (SEM) at 50×, 150×, and 500× magnification. The changes in slot area were scored using the customized scale. The Energy Dispersive Xray Spectroscopy Analysis (EDAX) was used to estimate the probed elements' atomic and weight percentage. ResultsThe mean score of the scale was 3.4 for the brackets immersed in the acidic solution which was statistically significant (p = 0.00)and for alkaline and neutral solutions (p = 0.00). Chromium was found to be significantly higher in the alkaline solution (p = 0.016) followed by the neutral solution. Carbon was found excess in acidic solution than the neutral and alkaline solution. ConclusionQuantitative and qualitative analysis of the ion release in stainless steel brackets using SEM and EDAX revealed the corrosive effect of fluoride ion causing maximum surface changes in acidic medium and chromium release in alkaline pH.

Evaluation of the surface characteristics and antibacterial properties of Titanium dioxide nanotube and methacryloyloxyethylphosphorylcholine (MPC) coated orthodontic brackets-a comparative invitro study

ObjectivesWhite spot lesions are the most common iatrogenic effect observed during orthodontic treatment. This study aimed to compare the surface characteristics and antibacterial action of uncoated and coated orthodontic brackets.Materials and methodsSixty commercially available stainless steel brackets were coated with TiO2 nanotubes and methacryloyloxyethylphosphorylcholine. The sample was divided into Group 1: uncoated orthodontic brackets, Group 2: Stainless steel brackets with TiO2 nanotubes coating, Group 3: Stainless steel brackets with methacryloyloxyethylphosphorylcholine coating, and Group 4: Stainless steel brackets with TiO2 nanotubes combined with methacryloyloxyethylphosphorylcholine coating. Surface characterization was assessed using atomic force microscopy and scanning electron microscopy. Streptococcus mutans was selected to test the antibacterial ability of the orthodontic brackets, total bacterial adhesion and bacterial viability were assessed. The brackets were subjected to scanning electron microscopy to detect the presence of biofilm.ResultsThe surface roughness was the greatest in Group 1 and least in Group 2 followed by Group 4 and Group 3 coated brackets. The optical density values were highest in Group 1 and lowest in Group 4. Comparison of colony counts revealed high counts in Group 1 and low counts in Group 4. A positive correlation between surface roughness and colony counts was obtained, however, was not statistically significant.ConclusionsThe coated orthodontic brackets exhibited less surface roughness than the uncoated orthodontic brackets. Group 4 coated orthodontic brackets showed the best antibacterial properties.Clinical relevanceCoated orthodontic brackets prevent adhesion of streptococcus mutans and reduces plaque accumulation around the brackets thereby preventing formation of white spot lesions during orthodontic treatment.

Quantifying the environmental impact of structural timber across multiple future lifecycles

The pressing challenge of reducing human-induced environmental and climate impacts requires a massive transformation in the construction sector, a major contributor to energy consumption and CO2 emissions. The potential for implementing circular strategies in construction is increasingly supported by current standards and reports. Emerging technologies, like cross-laminated reclaimed timber, render cascading options potentially comparable to direct reuse. Simultaneously, wood possesses a high heating value, meaning that incineration remains a competitive alternative to recycling seen from a contemporary market perspective. This study seeks to identify the most environmentally beneficial end-of-life strategy for structural timber elements under diverse future scenarios, taking into account systemic changes occurring over time. It introduces novelty by combining elements that are relevant to this context: (1) the circular economy of timber; (2) structural calculations accounting for material quality and losses; (3) dynamic prospective life-cycle assessments (LCAs); and (4) matching different circular-economy strategies with compatible future scenarios suggested by the Shared Socioeconomic Pathways (SSPs) mentioned in the IPCC’s sixth assessment report. The results indicate that the reuse of timber is beneficial only when there is no need for additional steel brackets, underscoring the importance of a meticulous definition of the unit with all adjoining structures to ensure accurate and appropriate results. Furthermore, the cascading options are valuable primarily in preserving the high performance of the element during its subsequent use.

Evaluation of the effects of different mouthwashes, acidic soft drinks, and herbal teas on shear bond strength of orthodontic stainless steel brackets: A stereomicroscopic study

Background: Premature debonding of brackets often turns out into orthodontic treatment failures and actual treatment delays. The aim of the present study was to evaluate the effects of different mouthwashes, acidic soft drinks, and herbal teas on the shear bond strength of metal (stainless steel) brackets used in orthodontic practice. Materials and methods: For the present study, 100 therapeutically extracted healthy premolar teeth with sound enamel surface were collected from patients who were scheduled for orthodontic treatment. The select teeth were cleansed, whereas the dried enamel surface was etched with 38% phosphoric acid for 15 s following which orthodontic stainless steel brackets (MBT 0.022 SLOT) were bonded with the help of composite resin (3M Unitek Transbond XT Light Cure Adhesive). The prepared teeth were divided into four groups depending on exposure to different mouthwashes, acidic soft drinks, and herbal teas. The shear bond strength values of the specimen were measured using a universal testing machine, whereas debonded surfaces were observed under a stereomicroscope. Statistical analysis was done using the Statistical Package for the Social Sciences (SPSS) version 18.0 (SPSS Inc., Chicago, IL, USA). One-way analysis of variance and Tukey’s multiple post hoc procedures were used for statistical analysis. P <0.05 was considered statistically significant. Results: The results obtained in the present study suggested that the highest mean shear bond strength observed was in case of Group II specimen with a mean value of 11.83 ± 1.92 MPa, whereas the least shear bond strength was observed in case of Group III specimen with a mean value of 10.33 ± 1.31 MPa, with the results being statistically significant (P = 0.014). Conclusions: Within the limitations of the present study, it was concluded that comparatively lesser/weaker shear bond strength values were observed in case of specimen belonging to Group III, wherein among the 30 teeth belonging to Group III, 12 teeth showed shear bond strength value of 9 MPa which was the lowest in the study. The following core competencies are addressed in this article: Practice-based learning and improvement, Patient care and procedural skills, Systems-based practice, Medical knowledge.

Effect of Elastomeric Module Degradation and Ligation Methods on Kinetic Friction between NiTi or Stainless Steel Wires and Stainless Steel Brackets.

Objectives: The reduction of resistance to sliding between the archwire and bracket promotes more seamless tooth movement, leading to a faster and improved orthodontic treatment experience. This research aimed to examine how the degradation of elastomeric modules, different ligation methods, bracket-wire angle, and wire type (nickel titanium, NiTi or stainless-steel, SS) impact the kinetic friction resulting from the interaction between NiTi or SS archwires and SS brackets. Materials and Methods: The current in vitro study was conducted on nine groups, including NiTi and SS archwires with three types of ligations (O-ring, figure of 8, and SS wire ligature) and two bracket-wire angles (0˚ and 10˚). The kinetic friction in each group was measured using a Universal Testing Machine at four time intervals: baseline, day one, week one, and week four. Repeated measures ANOVA, Mauchly test of sphericity followed by the Greenhouse-Geisser test, and relevant post hoc tests were used for statistical analysis (P<0.05). Results: The authors found a decrease in kinetic friction in all types of ligations, which confirmed the effect of time on the degradation of ligation modules. The kinetic friction of figure of 8 ligations was higher than both O-ring and SS wire ligations. No difference was observed between O-ring and SS wire ligations. Furthermore, the bracket-wire angle did not affect friction. Conclusion: The authors suggest that the use of figure of 8 ligations in NiTi and SS wires should be limited due to their high friction and replaced with other types of ligations, if possible.

PROPOLIS EXTRACT AS ANTI-CORROSIVE AGENT INHIBITS METAL IONIC RELEASE FROM ORTHODONTIC BRACKETS

Background: A combination of nickel (Ni), chromium (Cr), and iron (Fe) can be found in the stainless steel orthodontic bracket. Ion release takes place as a result of the chemical interaction between metals and the oral environment, which leads to the potential of hypersensitivity during fixed orthodontic treatment. Propolis contains phytochemicals that have the ability to reduce corrosion, making it a potential treatment option. Purpose: to determine the release of Ni, Cr, and Fe in metal brackets in an 8.2% propolis solutionMethod: Four sets of six brackets were made from 24 brackets. Artificial saliva, sodium fluoride, sterilized distilled water (aquabidest), and 8.2% propolis were applied to these brackets. After incubating at 37°C for seven days, ICP EOS measured the metal ions Ni, Cr, and Fe. The analysis revealed significant differences (p&lt;0.05) in ionic release of Ni, Cr, and Fe among groups exposed to sterilized distilled water (aquabidest) and an 8.2% propolis solution. Additionally, the Mann-Whitney test showed substantial Ni ion release differences (p&lt;0.05) between 8.2% propolis solution and sterilized distilled water. The 8.2% propolis solution and sodium fluoride solution released Cr ions differently. Fe ion levels differed between propolis solution 8.2%, sodium fluoride solution, sterilized distilled water, and fake saliva. Conclusion: Propolis affects metal bracket ionic release of Ni, Cr, and Fe. Keywords : Cr and Fe, ions of Ni, propolis solution, Stainless steel bracket

Evaluation of the Curing of the Primer on Shear Bond Strength of Orthodontic Brackets: An Original Research

ABSTRACT Background: The aim of this study was to evaluate the effect of separately curing the unfilled resin for increased bond strength of the orthodontic brackets as the literature shows both studies that support and contradict this aspect. Methodology: The sample consisted of 120 specimens randomly grouped into four of 30. The tooth was cleaned of tissue and debris and stored in a distilled water solution until the procedures of bonding. The surface of the enamel was conditioned with pumice, and acrylic blocks were designed for the tooth to be mounted onto them. The buccal surfaces of all the teeth were prepared by etching the enamel with 37% phosphoric acid for a time period of 30 seconds and washed for 20 seconds under running water. Stainless steel brackets (Victory Series™ MBT, 0.022 Slot) were used for all the samples in the study, and the bonding procedure was conducted on the same day for all the groups. The artificial saliva was used for the storage of samples for 24 h after bonding, and shear bond strength testing was conducted using an Instron machine in shear or peel mode at a crosshead speed. Results: The highest mean bond strength calculated was for the conventional technique (17.45 mpa), while it was the lowest for no primer adhesive (11.21 mpa). Group IV had a greater distribution of ARI scores than groups I, II, and III. Conclusion: Group IV achieved the highest bond strength when compared to other groups, with an ARI score of 3. Group III had less bond strength, likely due to incomplete curing of the primer due to insufficient exposure to light. Transbond XT can be used without primer, making bonding, debonding, and cleaning procedures easy and less time-consuming.

A Quantitative Evaluation of the Effectiveness of the Metal Artifact Reduction Algorithm in Cone Beam Computed Tomographic Images with Stainless Steel Orthodontic Brackets and Arch Wires: An Ex Vivo Study.

The presence of high-density and high-atomic number materials results in the generation of artifacts in cone beam computed tomographic (CBCT) images. To minimize artifacts in CBCT images, the metal artifact reduction (MAR) tool was developed. This study aims to quantitatively evaluate the effectiveness of the MAR algorithm in CBCT images of teeth with stainless steel orthodontic brackets with or without arch wires in buccal and lingual positions obtained using the Galileos Sirona CBCT scanner. In this in vitro study, 20 stainless steel brackets were attached to the maxillary dentition from the right second premolar to the left second premolar teeth of a human skull. In the first group, 10 brackets were bonded to the buccal surface, and in the second group, 10 brackets were bonded to the palatal surface of these teeth. CBCT scans were obtained for each group with or without orthodontic stainless steel wires using a Galileos Sirona CBCT scanner with exposure parameters of 85 kVp and 21 mAs. CBCT images were obtained two times with and two times without MAR activation. The DICOM format of the CBCT images was imported to ImageJ software (version 1.54), and the contrast-to-noise ratio (CNR) was calculated and compared for each bracket in 15 and 20 mm distances and 20, 40, and 90 degrees on each side. Statistical analysis was performed using the t test (α = 0.05). CNR values of different distances and different teeth were not significantly different between the two MAR modes (p > 0.05). MAR activation had a significant impact in increasing CNR and reducing artifacts only when brackets were in palatal (p = 0.03). In the other bracket and wire positions, the effect of the MAR algorithm on CNR was not significant (p > 0.05). In conclusion, MAR activation significantly increased CNR, but only when the brackets were in a palatal position. In the other bracket and wire positions, the effect of the MAR algorithm is not significant.

Metal Artifact Reduction by Using MARS System of a CBCT Unit with Different Components of Fixed Orthodontic Appliances: An In vitro CBCT Analysis

Introduction During Cone beam computed tomography (CBCT) imaging in the head and neck region of patients who are undergoing fixed orthodontic treatment, the different components of fixed orthodontic appliances can produce various metal artifacts which may degrade the diagnostic image quality in the region of interest. Therefore, the metal artifact reduction software (MARS) system can be used in most CBCT units to reduce the amount of artifacts generated from various fixed orthodontic appliance components including skeletal anchorage devices. Aims and Objectives The main purpose of this study was to quantitatively evaluate the effectiveness of MARS system of a CBCT unit in reducing the amount of artifacts generated by various fixed orthodontic appliance components during CBCT imaging. Materials and Methods Four dental arch shaped phantoms that were fabricated along with different fixed orthodontic appliance components (metal bracket, molar band, transpalatal arch, mini-implant) underwent CBCT scanning without and with the MARS setting option. After using the MARS system of a CBCT unit, the reduction in the amount of artifacts that were generated by various fixed orthodontic appliance component was calculated by using Google Colab software that utilized Python code and OpenCV system to generate a binary mask image. The resulting mask image highlights the areas where artifacts are detected, allowing for further analysis or visual inspection. The contours found within the mask image represent the boundaries of the artifact regions. Results After calculating the percentage decrease in artifact area for each component of fixed orthodontic appliance, one-way analysis of variance (ANOVA) test was performed to compare the percentage decrease in artifact area for each component of fixed orthodontic appliances. *P-values are calculated using one-way analysis of variance ( p &lt; 0.05). The percentage decrease in artifact area for different components of fixed orthodontic appliance ranged from 39.67% to 48.58%. The stainless steel bracket showed the significant artifact area reduction with a mean percentage decrease of 48.58% as compared to other components. Conclusion The effect of MARS system in reducing the amount of metal artifacts generated varied according to the component type of fixed orthodontic appliance and, MARS system was more efficient for stainless steel brackets as compared to other components. CBCT imaging of head and neck region can be carried out without taking off the orthodontic appliances by applying MARS system which can significantly decrease the artifact area.

Mechanical properties and analytical model of a novel dissipative angle bracket for CLT structures

The connections are essential in providing the strength, stiffness, ductility, and energy-dissipating capacity for CLT structures. In this paper, a novel dissipative angle bracket for CLT structures was proposed, which combines the benefits of soft-steel brackets and high-damping rubber to offer great energy-dissipating capacity and high ductility. Both quasi-static monotonic and reversed cyclic loading tests were conducted to evaluate the failure mechanisms and mechanical properties of this connection. Failure modes, including the rupture of steel ribs, fracture of the CLT wall, and debonding of the CLT slab, were observed during the tests. The rupture of steel ribs is the controlled failure mode, but the connection can still work as a whole to resist applied load after the steel ribs’ failures thanks to the rubber that is effectively bonded to the steel bracket. The tested connections’ load-displacement curves exhibit a bi-linear form, with the yielding point resulting from the yielding of steel ribs. Almost all the tested specimens have a ductility larger than 9.0 and an equivalent viscous damping ratio of around 10%–22%, indicating high ductility and energy-dissipating capacity. Furthermore, a simplified analytical model of the novel dissipative angle bracket was established. Comparison with test results demonstrates that the proposed model can reasonably estimate the initial stiffness, post-yield stiffness, and yield force. The outcomes of this study are expected to provide valuable references for future research and potential applications of the novel dissipative angle bracket for CLT structures.

Experimental and numerical analysis of strength and deformation of large‐scale steel‐composite adhesive joints subjected to fatigue followed by static loading

AbstractThis work reports a study of the fatigue behaviour and quasi‐static strength of full‐scale adhesively bonded steel‐composite joints. Three joints with an approximately 10‐mm‐thick layer of methyl methacrylate adhesive were manufactured in dockyard conditions. One specimen was tensile tested till failure, while two specimens were subjected to ~3.5 million fatigue cycles, followed by a residual tensile test supported with digital image correlation. The shear, longitudinal and peel strain values within the adhesive bondlines are significantly higher at the gripped sides due to the asymmetrical design of the steel brackets. All specimens showed a significantly higher shear strength than the design values defined by the shipbuilder. Fibre Bragg sensors monitored strains at steel and composite constituents and allowed to detect damage onset and evolution in tensile tested specimens. A finite element model of the joint was developed with material and interface properties based on dedicated small‐scale experiments. The simulation results of strains during a static load test corresponded closely to the DIC measurements. All specimens failed near the composite‐adhesive interface due to delamination of the composite panel.