Tension Side Research Articles

Osteoblast differentiation of Gli1⁺ cells via Wnt and BMP signaling pathways during orthodontic tooth movement

ObjectivesFactors that induce bone formation during orthodontic tooth movement (OTM) remain unclear. Gli1 was recently identified as a stem cell marker in the periodontal ligament (PDL). Therefore, we evaluated the mechanism of differentiation of Cre/LoxP-mediated Gli1/Tomato+ cells into osteoblasts during OTM. MethodsAfter the final administration of tamoxifen to 8-week-old Gli1-CreERT2/ROSA26-loxP-stop-loxP-tdTomato mice for 2 days, nickel–titanium closed coil springs were attached between the upper anterior alveolar bone and the first molar. Immunohistochemical localizations of β-catenin, Smad4, and Runx2 were observed in the PDL on 2, 5, and 10 days after OTM initiation. ResultsIn the untreated tooth, few Gli1/Tomato+ cells were detected in the PDL. Two days after OTM initiation, the number of Gli1/Tomato+ cells increased in the PDL on the tension side. On this side, 49.3 ± 7.0% of β-catenin+ and 48.7 ± 5.7% of Smad4+ cells were found in the PDL, and Runx2 expression was detected in some Gli1/Tomato+ cells apart from the alveolar bone. The number of positive cells in the PDL reached a maximum on day 5. In contrast, on the compression side, β-catenin and Smad4 exhibited less immunoreactivity. On day 10, Gli1/Tomato+ cells were aligned on the alveolar bone on the tension side, with some expressing Runx2. ConclusionsGli1+ cells in the PDL differentiated into osteoblasts during OTM. Wnt and bone morphogenetic proteins signaling pathways may be involved in this differentiation.

Aucubin produces anti-osteoporotic effects under mechanical stretch stress and orthodontic tooth movement

Aucubin (AU), an iridoid glycoside extracted from Eucommia ulmoides, exerts anti-osteoporotic effects by promoting osteogenesis, as reported in previous studies. Here, we investigated the effects of AU under mechanical stretch stress. MC3T3-E1 cells were treated with dexamethasone (DEX) in vitro and subjected to mechanical stretch stress to establish an osteoporotic orthodontic force cell model. AU treatment increased the mRNA and protein expressions of BMP2, OPN, RUNX2, COL-1 and other osteogenic differentiation factors in MC3T3-E1 cells. Furthermore, we established an in vivo orthodontic tooth movement (OTM) model of osteoporosis. Serum parameter detection of ALP concentration, radiography of the femur, hematoxylin-eosin (HE) staining, and micro-CT of the maxilla confirmed that AU could partially reverse the damage induced by DEX. Immunohistochemical (IHC) analysis showed that AU increased the expression of COL-1, OCN, and OPN on the tension side of the periodontium. In conclusion, AU treatment promotes osteogenic differentiation under mechanical stretch stress and positively affects bone remodeling during OTM in DEX-induced osteoporosis.

Numerical Analysis of Rubberized Steel Fiber Reinforced Concrete Beams Subjected to Static and Blast Loadings

In recent years, the alarming number of terrorist attacks has highlighted the critical need for extensive research aimed at fortifying structures against explosion-induced loads. However, the insufficient energy absorption and brittleness of conventional concrete make it ineffective in withstanding blast loading, encouraging researchers to explore innovative strategies for augmenting the energy dissipation capabilities of construction materials. This study specifically delves into the incorporation of recycled rubber, a sustainable and environmentally friendly solution to the pressing issue of scrap tire disposal. The primary focus of this research revolves around the integration of rubber recycling and steel fibers into concrete, with the ultimate goal of enhancing the dynamic response of reinforced concrete (RC) beams. This novel approach not only contributes to the structural resilience required for resisting blast impacts, but also aligns with eco-friendly practices by reusing recycled rubber. A meticulous numerical investigation was undertaken to comprehensively assess the static and blast response of these augmented beams. The numerical study involved developing finite element (FE) models using ABAQUS version 6.14 for static implicit analysis and LS-DYNA R11 for blast explicit simulations. The ABAQUS model was validated against previous experimental testing for load–displacement and failure patterns. Similarly, the LS-DYNA model was validated for blast pressure in accordance with UFC-3-340 standards and for material response under blast loading, utilizing existing experimental data. The numerical models were designed to accommodate varying weight percentages of rubber, ranging from 5% to 20%, and a consistent 1.0% incorporation of steel fibers. This comprehensive analysis aims to provide valuable insights into the efficacy of these materials in improving the structural integrity and blast resistance of RC beams, thereby contributing to the development of more secure and sustainable construction practices. By reducing the reinforcement ratio in order to meet the minimum code requirements, it became evident that the failures of the rubberized RC beams tended to exhibit ductility on the tension side under static loading. In addition, the increase in the reinforcement ratio correlated with a higher failure load and decreased deflection. Furthermore, the findings indicated an optimal concrete mixture characterized by improved ductility, energy absorption, and blast load capacity, achieved by combining 5–10% rubber with steel fibers.

Orthodontic tension promotes cementoblast mineralization by regulating autophagy

Background/purposeExternal root resorption is a main side effect of orthodontic treatment and is more likely to occur on the pression side than the tension side. To explore the potential protective mechanisms on the tension side, this study investigated the influence of mechanical tension on cementoblast mineralization and elucidated the role of autophagy in mediating this process. Materials and methodsMechanical tension was applied to cementoblasts using iStrain. The expression of mineralization-related and autophagy-related markers was detected by qRT-PCR, Western blot analysis, and immunofluorescence staining. RNA sequencing identified key regulators. Immunohistochemical staining assessed related markers expression in in vivo experiments. ResultsApplying tension to cementoblasts increased mineralization-related gene expression in a force-dependent and time-dependent manner. The immunohistochemical staining result of in vivo experiments supported these findings, demonstrating elevated expression of mineralization markers under tension. Mechanical tension also enhanced autophagic activity in cementoblasts, which was demonstrated by the results of qRT-PCR, Western blot analysis, immunofluorescence staining, and in vivo experiments. Suppression of autophagy with chloroquine attenuated the mineralization of cementoblasts induced by tension stimulus. RNA-seq identified Postn as a key regulator, and the knockdown of Postn impaired the mechanical tension-promoted mineralization of cementoblasts. ConclusionThis study proposed the tension-induced promotion in mineralization of cementoblasts and emphasized the mediating role of autophagy in this process. Postn, a mediator connecting autophagy and mineralization, was identified as a key regulator. These discoveries helped elucidate orthodontic-related microprocesses on tooth roots and offer potential targets for therapeutic interventions to prevent and restore external root resorption clinically.

Flexural Strength and Morphological Study of Different Multilayer Zirconia Dental Materials.

Nowadays, yttria (Y3+)-stabilized ZrO2 (Y-TZP) is the most commonly used material in dental prosthetics. Y-TZP dental ceramics are mainly stabilized via the addition of 3 mol% yttrium oxide (Y2O3). These ceramics exhibit excellent mechanical properties, including high flexural strength, fracture toughness, elastic modulus, etc. Some manufacturers have recently introduced a new class of dental materials with multilayer composition with the aim of combining the advantages of adding more or less Y2O3 to the ceramic composition in one Y-TZP material. The flexural strength values of multilayer Y-TZP may vary depending on the dimensions of the specimen, layer distributions, and especially the layer exposed on the maximum tension side, i.e., loading configuration. Although previous studies have examined the flexural strength of separate Y-TZP layers, capturing the flexural strength of multilayer Y-TZP is still challenging. However, one should keep in mind that multilayer flexural strength is important for clinical indications. The objective of this study is to compare the flexural strength of three distinct multilayer translucent Y-TZP materials made up of layers with different Y3+ contents. Rectangular samples (2 mm × 2 mm × 16 mm) were prepared from CAD/CAM discs using the milling machine Programill PM7 (Ivoclar Vivadent AG). Milled bars were tested for flexural strength in a three-point bending test (ISO 6872:2015) using a universal testing machine (Inspekt Duo 5kN; Hegewald & Peschke, Nossen, Germany) at a crosshead speed of 0.5 mm/min. Representative samples of each type of material were selected for quantitative and qualitative analysis of the microstructure. Representative samples of each type of material were selected for structural, mechanical, and microstructural analyses.

Effect of hybrid ratio on the flexural properties of Arenga Pinnata fiber/E-glass fiber/polyester hybrid composites

Hybrid ratio effect on flexural properties of sugar palm/E-glass fiber hybrid-reinforced polyester composites has been investigated. Before being embedded, the sugar palm fiber was taken off from its original mesh, washed, alkali-treated, and chopped into ~10 mm long. The specimens were cut from composite plates having different hybrid ratios, fabricated using cold pressed technique. The total fiber volume fraction was kept at ~0.21, where four hybrid ratios, and two span-to-depth ratios were used. The E-glass was arranged unidirectionally and placed right on the surface of a bottom mold and wetted using the matrix, and the SPF was then evenly poured on the wet E-glass arrangement in randomly oriented pattern. Specimen preparation and testing were carried out according to the ASTM D790 standard, where the E-glass sides were placed in tension sides of the beams. It was found that flexural strength, and strain at maximum stress significantly increase with the increase of hybrid ratio.

Seismic behavior of BFRP bar reinforced shear walls strengthened with ultra-high-performance concrete boundary elements

Reducing the amount of steel reinforcement in construction is imperative, driven by the objectives of reducing carbon emissions and mitigating steel corrosion. Among the various alternatives to steel reinforcement, basalt fiber reinforced polymer bar (BFRP) is considered a promising solution. The aim of this study is to examine the seismic performance of shear walls entirely reinforced with BFRP bars, utilizing BFRP for both longitudinal and transverse reinforcement. To address the inherent limitations of BFRP bars, a novel composite shear wall, incorporating BFRP bars, ultra-high-performance concrete (UHPC) and normal strength concrete, is proposed. Specifically, UHPC boundary elements are employed to strengthen the potential compression zone of BFRP reinforced shear walls. Four shear wall specimens, fully reinforced with BFRP bars, were fabricated and tested for their seismic performance, with two specimens incorporating UHPC boundary elements. Comprehensive test results, including failure modes, load-bearing capacity, ductility, energy dissipation, stiffness degradation and rebar strain, are presented and discussed. A detailed discussion of the effects of axial load ratio (ALR) and UHPC boundary elements is included. The test results indicate that the specimens featuring UHPC boundary elements showed significant improvements in deformability, lateral strength and energy dissipation capacity. This reveals that the integration of UHPC boundary elements considerably enhances the seismic performance of BFRP bar reinforced shear walls. Moreover, although all test specimens experienced failure due to concrete crushing in the compression zone, those with UHPC boundary elements manifested higher tensile strain on the BFRP bars on the tension side, facilitating more effective utilization of the high tensile strength of the BFRP bars. Ultimately, a method to ascertain the flexural capacity of BFRP bar reinforced shear walls, both with and without UHPC boundary elements, is proposed and validated by the test results.

Assessment on Strength and Stiffness Properties of Aged Structural Timber

Despite the growing popularity of wood and wood-based products in the construction industry, there has been insufficient focus on assessing the condition, preservation, and potential reuse of existing timber. While numerous standards evaluate the quality of freshly sawn timber, there is currently no standardized system for assessing the strength properties of aged and reused timber. The lack of these guidelines is also one of the reasons the results obtained in numerous research are often fluctuating, and we cannot draw clear conclusions. The matter is further complicated by the lack of data on old in-situ wood and its exploitation, which would help to evaluate its condition. Consequently, there is a real practical need to assess the condition of old timber to avoid unnecessary demolition and the loss of valuable and structurally sound building material. What sets this study apart from others is that, in addition to destructive testing, the 4-point non-destructive (ND) bending tests were conducted on all four faces of test specimens. This provided an opportunity to assess the wood visually and then find connections to associate external characteristics with real properties. This methodology aimed to determine whether it is feasible to visually assess the most practical way to use wooden elements in construction. If this question arises, which face of the beam would be better suited for the tension side and which for the compression side? The old timber used in testing originated from an old library building located on Vaksali Street, Tartu, Estonia and is estimated to be about 120 years old. This paper investigates and compares the collected data with a Nordic standard for grading fresh-sawn timber and two established Italian standards for visually assessing aged timber. This comparison contributes to developing a standardized framework for future visual assessments. ND and destructive four-point bending tests were performed to validate and find appropriate visual characteristics to determine the strength and stiffness of the timber elements. The primary goals of this study were first to compare the results obtained from existing ND methods with actual results and secondly to provide guidelines for better visual grading of wood in the future, based on Nordic Standard INSTA 142 (2010) and Italian standards UNI 11119 (2004) and UNI 11035 (2010) Contrary to previous research conclusions, the visual assessment results yielded unexpected outcomes. The results show that the grading standards significantly underestimated the real strength of the wood, and even more, none of the visual assessments overestimated the real strength of the specimens. Therefore, based on prior research and the findings derived from this study, there is evident a substantial potential for extensive development and optimization within this field.

STUDY ON SEALING PERFORMANCE OF AIRTIGHT BUCKLE UNDER COMPLEX LOADS

The existing studies on sealing performance of airtight buckle of production strings in oil and gas extraction mainly focus on complex loads without bending moment. In this paper, a numerical model of an airtight buckle under the complicated load with bending moment is constructed. The precision of the model is verified by comparing with theoretical value for thick-walled cylinders. The impact of simple and complex loads on the contact stress of the sealing surfaces is discussed. It should be noted that the contact stress exhibits a combined effect of multiple factors, and the internal pressure plays a dominant role. However, the influence of bending moments on the contact stress of the sealing surface can “reverse” under specific load combinations. The reason for this phenomenon is that the sensitivity of the tension side and compression side to internal pressure is different under bending moment. The obtained results can guide the design and usage for airtight buckle of the production string.

Flexural behavior of high strength concrete shallow wide beams reinforced by hybrid longitudinal reinforcement

ABSTRACT One of the most common statistical systems used in structures especially for wide span slabs are ribbed slabs with shallow wide beams (SWB). This experimental study aimed to investigate and enhance the flexural behavior of high-strength concrete SWB using hybrid longitudinal reinforcement from steel and advanced composite materials as a tensile main reinforcement in SWB. Longitudinal advanced composite bars locally manufactured from ribbed glass fiber reinforced polymer (GFRP) and the second type was ribbed basalt fiber reinforced polymer (BFRP). A group of six half scale SWB were examined in structures laboratory of American University in Cairo with dimensions 2.1 × 0.6 × 0.25 m for length (L), width (B) and depth (d) respectively with constant size effect (d/B). The first three specimens were completely reinforced at tension side with Steel, GFRP or BFRP ribbed bars to be considered a control specimen. Use of GFRP and BFRP bars enhanced the flexural capacity of SWB with 41% and 43% respectively compared to specimen completely reinforced with steel. But on the other hand, the crack propagation of specimens completely reinforced with GFRP and BFRP developed more quickly and had larger crack width compared to specimen completely reinforced with steel. Hybrid reinforcement from Steel with GFRP, Steel with BFRP and Steel with GFRP and BFRP specimens are used to enhance the crack pattern and mode of failure without a significant loss in flexural capacity of SWB. The flexural capacity of these three specimens was enhanced with 26%, 30% and 41% with a significant enhancement in crack pattern and ductility.

Accurate rotation identification of flexural structures using long-gauge fiber optical sensors

The rotation of beam and column components is a key parameter in structural health monitoring (SHM), which providing analysis of bending deformation, evaluation of structural stability, and overall structural performance. Conventional sensors directly measuring rotation are typically designed assuming linear behavior. It becomes challenging to achieve precise and rapid measurements of small deformations while accurately measuring significant large deformations. This study obtained experimental and analytical studies to identify the rotation response of flexural structures using long-gauge fiber optical sensor array. Rotation is determined through two mechanisms: the plane section assumption, utilizing strain distributions on the compression and tension sides, and the sectional fiber model (SFM)-based neutral axis identification. In order to discuss the applicability of these two mechanisms from elastic to plastic state, four identification methods are proposed: Method 1 uses strain distribution on the concrete surface to identify rotation, Method 2 uses strain on steel bars, and Methods 3 and 4 use SFM-based neutral axis identification with strain measured on the compression side concrete surface and tension side steel reinforcements, respectively. Laboratory tests of beams and columns as well as field tests were shown. First, a comparison of the rotation identification accuracy among the four methods was conducted using a reinforced concrete (RC) beam test in the elastic state. Results showed good agreement between the rotations identified by all four methods and those directly measured by the tilt meter. And then, the accuracy of rotation identification in crack state and inelastic state was discussed by using a RC column test. The results indicate that, following the occurrence of cracks in concrete surface, neither Method 1 nor Method 2 can accurately identify the rotation. This is attributed to the fact that cracks disrupt the correspondence between the strain on the tension side and the compression side. Meanwhile, Methods 3 and 4 maintain a good rotational identification accuracy even after cracks happened. Moreover, when the steel reinforcement undergoes yielding and the concrete column enters the inelastic state, the rotation results identified by Methods 3 and 4 still match with the directly measured rotations. This underscores the effectiveness of the SFM-based rotational identification under large deformation conditions. Furthermore, experimental results indicate that with the increase in deformations, slip occurred in the sensing units near the column base in the sensor array on the tension side. This shows that the sensing units installed on the steel reinforcement (Method 4) are more suitable for calculating rotations during the large deformation state compared to the sensing units positioned on the concrete surface (Method 3). At last, two case studies involving the monitoring of an actual bridge grid and a bridge column were investigated to assess the effectiveness of dynamic rotation identifications. The performance evaluation results for various rotation angle measurement sensors demonstrate that long-gauge fiber optical sensors can be used for rotation identification, ensuring the stability of dynamic rotation identification.

Optimization of a Photobiomodulation Protocol to Improve the Cell Viability, Proliferation and Protein Expression in Osteoblasts and Periodontal Ligament Fibroblasts for Accelerated Orthodontic Treatment.

Numerous pieces of evidence have supported the therapeutic potential of photobiomodulation (PBM) to modulate bone remodeling on mechanically stimulated teeth, proving PBM's ability to be used as a coadjuvant treatment to accelerate orthodontic tooth movement (OTM). However, there are still uncertainty and discourse around the optimal PBM protocols, which hampers its optimal and consolidated clinical applicability. Given the differential expression and metabolic patterns exhibited in the tension and compression sides of orthodontically stressed teeth, it is plausible that different types of irradiation may be applied to each side of the teeth. In this sense, this study aimed to design and implement an optimization protocol to find the most appropriate PBM parameters to stimulate specific bone turnover processes. To this end, three levels of wavelength (655, 810 and 940 nm), two power densities (5 and 10 mW/cm2) and two regimens of single and multiple sessions within three consecutive days were tested. The biological response of osteoblasts and periodontal ligament (PDL) fibroblasts was addressed by monitoring the PBM's impact on the cellular metabolic activity, as well as on key bone remodeling mediators, including alkaline phosphatase (ALP), osteoprotegerin (OPG) and receptor activator of nuclear factor κ-B ligand (RANK-L), each day. The results suggest that daily irradiation of 655 nm delivered at 10 mW/cm2, as well as 810 and 940 nm light at 5 mW/cm2, lead to an increase in ALP and OPG, potentiating bone formation. In addition, irradiation of 810 nm at 5 mW/cm2 delivered for two consecutive days and suspended by the third day promotes a downregulation of OPG expression and a slight non-significant increase in RANK-L expression, being suitable to stimulate bone resorption. Future studies in animal models may clarify the impact of PBM on bone formation and resorption mediators for longer periods and address the possibility of testing different stimulation periodicities. The present in vitro study offers valuable insights into the effectiveness of specific PBM protocols to promote osteogenic and osteoclastogenesis responses and therefore its potential to stimulate bone formation on the tension side and bone resorption on the compression side of orthodontically stressed teeth.

Hyperbaric Oxygen Therapy to Minimize Orthodontic Relapse in Rabbits.

The purpose of the present study was to discover how hyperbaric oxygen therapy (HBOT) could reduce orthodontic relapse by altering the expressions of hypoxia-inducible factor (HIF)-1 messenger ribonucleic acid (mRNA), type I collagen (Col I), and matrix metalloproteinase-1 (MMP-1) in the gingival supracrestal fibers in rabbits. This study involved 44 male rabbits (Oryctolagus cuniculus) randomly divided into the normal group (K0), the orthodontic group without HBOT (K1), and the orthodontic group with HBOT (K2). Following orthodontic separation of the two upper central incisors, a retention phase and relapse assessment were performed. The HBOT was performed for a period of 2, 4, 6, 8, and 10 days after retention. HIF-1α transcription was assessed employing real-time polymerase chain reaction, whereas Col I and MMP-1 proteins were examined using immunohistochemistry. The orthodontic relapse was measured clinically using a digital caliper. We used the one-way analysis of variance followed by Tukey's post hoc for multiple comparisons to measure differences between pairs of means; a p-value of 0.05 was considered statistically significant. HBOT significantly increased the HIF-1α mRNA expression (p = 0.0140), increased Col I (p = 0.0043) and MMP-1 (p = 0.0068) on the tensioned and pressured side of the gingival supracrestal fibers, respectively, and clinically decreased the relapse (p = 3.75 × 10-40). HBOT minimizes orthodontic relapse by influencing HIF-1α expression, collagen synthesis (Col I), and degradation (MMP-1). This result suggests that HBOT has the potential to be used as an adjunctive method in the orthodontic retention phase.

Strengthening of Reinforced Concrete Beams via CFRP Orientation

The utilization of externally bonded carbon fiber-reinforced polymers (CFRPs) and glass fiber-reinforced polymers (GFRPs) for reinforcing and retrofitting components has garnered considerable interest recently, as such composites provide beneficial properties, including a high modulus of elasticity, high strength, and low weight. This work conducts a finite element analysis, verified through laboratory experiments on 14 reinforced concrete (RC) beams. The primary focus is the final load of these components, considering varying CFRP orientations relative to the loading direction. In this research, the performances of control beams and RC beams are compared to assess the effectiveness and efficiency of different strengthening methods. The results demonstrated that bonding CFRP sheets with V-shaped end anchorages on the tension side was highly effective in improving the flexural capacity of RC beams in the weaker concrete strength group. This strengthening method resulted in a substantial increase in strength (of around 29.8%) in the higher concrete strength group. In addition, utilizing V-shaped end anchorages to bond CFRP sheets on the tension side proved to be a highly efficient technique for improving flexural strength. Conversely, bonding inclined CFRP strips to the sides of RC beams was highly effective at enhancing the shear capacity of the beams. These outcomes convincingly demonstrate the effectiveness of FRP for the reinforcement of structural components. The specimens strengthened with inclined strips exhibited enhanced shear and deformation capacity compared to those strengthened with vertical strips.

Experimental and numerical investigation on axial behavior of circular and square slender reinforced columns

To investigate the axial performance of slender concrete-filled steel tube (CFST) columns reinforced by outer steel tube and sandwiched concrete jackets, an axial compression test was conducted on 20 circular and square slender reinforced columns. The study aimed to examine the influence of the cross-sectional shape, steel content of the outer tube, the strength of sandwiched concrete, and slenderness ratio on the failure mode, load-displacement curves, and ultimate load. A comparative test on six slender CFST columns was also conducted. The test results showed that the local buckling degree of the outer steel tube in square reinforced columns was greater than that in circular reinforced columns, while the overall bending deformation was smaller. The influence of the sandwiched concrete strength on the load-displacement curve was weaker compared to the influence of the outer tube thickness and slenderness ratio. As the slenderness ratio increased, both the longitudinal and lateral strains of the specimens tended to decrease. The difference in strain between the tension and compression sides was more pronounced in circular reinforced columns than in square reinforced columns. The average SI values of circular and square reinforced specimens were 1.05 and 1.00, respectively, but the gap in SI values between the two types of reinforced columns is reduced as the slenderness ratio increases. Then, a numerical model on the slender reinforced columns was established by the finite element software ABAQUS. A good agreement was obtained between test results and simulation results. The mechanical mechanism of typical slender reinforced columns was further analyzed, including longitudinal stress contour map of concrete, the development of longitudinal stress of steel tube, as well as distribution of transverse confinement stress. A formula was subsequently proposed based on a design code to predict the load-bearing capacity of the retrofitted columns, the prediction results agreed well with the experimental data.

Comparison of Orthodontic Tooth Movement of Regenerated Bone Induced by Carbonated Hydroxyapatite or Deproteinized Bovine Bone Mineral in Beagle Dogs.

Orthodontic treatments often involve tooth movement to improve dental alignment. In this study, we aimed to compare tooth movement in regenerated bone induced by two different bone fillers, carbonated hydroxyapatite (CAP) and deproteinized bovine bone mineral (DBBM). Four beagle dogs were used in this comparative study. The first, second, and fourth lower mandibular premolars (P1, P2, and P4) on both sides of the mouth were extracted, and CAP was implanted into the extraction site on the left side and DBBM into the right side. Following regenerative bone healing, orthodontic devices were attached to perform orthodontic tooth movement of the lower third mandibular premolar (P3) on both sides. X-ray examination, intraoral scan, and histological analysis were performed. The Mann-Whitney U test was used for statistical analysis, and p < 0.05 was considered significant. Bone regeneration and orthodontic tooth movement were observed in the CAP and DBBM groups. Histologically, normal periodontal tissue remodeling was observed on the compression and tension sides of CAP and DBBM. No statistical difference was observed in the number of osteoclasts around the periodontal ligament and the root resorption area. Orthodontic tooth movement of regenerated bone induced by CAP and DBBM was therefore achieved.

Influence of slab structure on the behavioral analysis of hybrid outrigger system

SummaryOutriggers are internal structural systems used to enhance the stiffness and strength of high‐rise structures. This research investigates the efficacy of a hybrid outrigger system (HOS) which consists of one conventional and one virtual outrigger at two distinct floor levels in high‐rise RCC buildings. A non‐dimensional quantity, ϒ, defined as the relative stiffness ratio between the core and the diaphragm is used to describe variations in the stiffness of the building's core, stiffness of floor diaphragm, breadth, and height of the structure, in the behavioral analysis of the HOS. To investigate the efficacy and optimum locations of the hybrid outriggers, static and dynamic analysis are carried out on models with four‐story heights of 140, 210, 280, and 350 m under static wind loading, uniform wind loading, equivalent static earthquake loading, and dynamic earthquake loading. Results are assessed based on the responses from roof displacement (Disptop), base bending moment, roof acceleration (Acctop), fundamental period, and absolute maximum inter‐story drift ratio (ISDabs.max). Based on the minimum responses of the aforementioned dependent parameters under wind and earthquake excitations, the corresponding optimum locations of hybrid outriggers are investigated. To investigate the impact of the slab on the functionality of the HOS, the behavior of shell stress variation in the tension and compression side of the slab at the outrigger floor level and the force transmission through the column at the outrigger level is analyzed. Also, the optimum location of the hybrid outriggers based on the ideal performance index (IdealPI) is investigated. IdealPI is defined as a parameter that considers the combined response of Disptop, Acctop, and ISDabs.max and the criteria required for the structure under wind and seismic loads. From the behavioral analysis results, it is found that an increase in the stiffness of the slab showed an improved performance of the HOS compared to an increase in the stiffness of the core, and HOS performance can be maximized by increasing both thickness of the slab and outrigger arm length. The findings of the optimum location analysis could serve as a guide for structural engineers when selecting suitable positions for hybrid outriggers in high‐rise structures.

USP12 regulates ER stress-associated osteogenesis in human periodontal ligament cells under tension stress

The bone formation (osteogenesis) of human periodontal ligament cells (hPDLCs) under tension stress is essential for alveolar bone remodeling during orthodontic tooth movement (OTM). Deubiquitinating enzymes (DUBs) remove ubiquitin from target proteins, affecting their function and mediating cell survival and differentiation. However, whether and how DUBs regulate hPDLC function under tension force is poorly understood. In this study, we first investigated the expression of DUBs in hPDLCs under cyclic tension stimulation (CTS). Up-regulation of USP12 was observed in hPDLCs and at the tension side of molar teeth in OTM C57BL6 mice models. Knockdown (KD) of USP12 led to enhanced osteogenesis of hPDLCs under CTS. RNA-seq analysis suggested that the unfolded protein response (UPR) was the prevailing biological process in hPDLCs with USP12 KD, indicating that USP12 depletion triggered endoplasmic reticulum (ER) stress. The three major UPR-related signaling branches, namely PERK/eIF2α/ATF4, IRE1α/XBP1s, and ATF6 axis, were activated in hPDLCs with USP12 KD. By utilizing specific inhibitors, we proved that the PERK/eIF2α/ATF4 axis predominantly mediated the enhanced osteogenesis in hPDLCs with USP12 KD under CTS. In summary, our study demonstrates that USP12 serves as a key regulator for CTS-induced osteogenesis in hPDLCs, suggesting that USP12 upregulation serves as an adaptive mechanism for hPDLCs to alleviate ER stress during OTM.

The unique flexibility feature of moso bamboo: Arising implications for biomimetic material design

Bamboo, renowned for its sustainability, renewable nature and extraordinary flexibility, has long been widely used as engineered materials. This coveted attribute can be attributed to the unique gradient microstructure of the bamboo culm, characterized by the volume fraction of reinforcing fibers diminishes exponentially from the epidermis to the endodermis. This inherent structural heterogeneity engenders disparate fracture behaviors and mechanical properties between the compression and tension sides during bending, i.e. the asymmetric bending behavior. Through a qualitative analysis with the shear-lag theory, this study has discerned that a critical range of fiber volume fraction, spanning from 25% to 30%, serves as the critical condition for whether fiber break occurs before or after pull-out. Moreover, it has been elucidated that the significant degree of radially discrepancy in fiber volume fraction manifests as a key determinant of the degree of asymmetry. By parameterizing the variation trend of the fiber volume fraction along the loading direction, it becomes feasible to predict the mechanical properties when subjected to loading from different sides. Such endeavors furnish a pivotal scientific foundation for characterizing the performance of gradient materials with similar densities, while concurrently offering novel insights for the structural design of high-performance biomimetic material.

Characterization of bamboo extrinsic toughening mechanism in bending by X-ray micro-computed tomography(micro-CT)

Bamboo as a natural biomaterial with excellent strength and toughness is widely used in construction, furniture, decoration, handicrafts and other fields. However, the internal cracks that lead to the bending-fracture behavior of bamboo during its application are not yet fully understood. Herein, we used micro-computed tomography (micro-CT) to investigate the external toughening mechanism of bamboo during bending aiming to broaden the application areas of bamboo. These studies demonstrated that bamboo's outstanding strength and toughness were attributed to the synergistic extrinsic toughening mechanism dominated by fibers. Moreover, the fiber delamination and interfacial debonding affected crack deflection in the surrounding parenchyma and vessels. Additionally, the fiber content was positively correlated with the energy release rate of fiber pullout. When the fiber content was close, the fibers closed to the tension side had a better inhibition effect on the crack propagation. Furthermore, the effects of different microstructure arrangements on crack deflection, crack deflection inside fibers, crack deflection in parenchyma, and the toughening mechanism of fiber pullout were also discussed. Therefore, this work further advances the mechanism strategy for enhancing the flexibility of bamboo, which indicates the great potential in bending applications.