Search Results (29)

Background/Objectives: The removal of a fiber post (FP) during endodontic retreatment can be the source of significant complications. This study evaluated two commonly used techniques in removing a fiber post from an endodontically treated tooth by investigating three metrics: volume of dentin removed, efficiency, and temperature increase. Methods: Thirty extracted, single-rooted teeth were decoronated at the CEJ, then underwent endodontic treatment and post-space preparation. Fiber posts were bonded within the canal space. Teeth were pair-matched and randomly assigned to undergo post removal via Munce bur (MB) or diamond-coated ultrasonic tip (US). Teeth were scanned with micro-CT prior to post placement and after post removal. Results: The volume of dentin removal was not statistically significant between groups (p > 0.05), but the Munce bur resulted in eccentric removal patterns. There was a statistically significant difference in the time required to remove the fiber post between MB and US (p < 0.05). Removal of a fiber post with a Munce bur took an average of 58 s. Removal of a fiber post with an ultrasonic tip took an average of 502 s. There was no statistically significant difference in maximum temperature generated during post removal between MB and US (p > 0.05). Conclusions: Removal of a FP with a Munce bur requires significantly less time when compared to using an ultrasonic tip, with reduced risk of generating excessive heat for either technique with adequate coolant. US can stay more centered in the canal during FP removal when compared to Munce burs, potentially reducing unfavorable outcomes. Full article

Objectives: The aim of the present study was to examine the growth dynamics of the first sacral vertebra and its ossification center in the human fetus, based on their linear, planar, and volumetric parameters. Methods: The examinations were carried out on 54 human fetuses of both sexes (26 males and 28 females) aged 18–30 weeks of gestation, which had been preserved in 10% neutral formalin solution. Using CT, digital image analysis software, 3D reconstruction, and statistical methods, the size of the first sacral vertebra and its ossification center was evaluated. Results: The first sacral vertebra and its ossification center grew proportionately according to fetal weeks. Conclusions: The numerical data obtained from computed tomography and the growth patterns of the body of the first sacral vertebra and its ossification center may serve as age-specific normative intervals relevant for gynecologists, obstetricians, pediatricians, and radiologists during fetal ultrasound screening. Our findings on the growth of the body of the first sacral vertebra and its ossification center may be useful in daily clinical practice, particularly in ultrasonic monitoring of normal fetal growth and in screening for congenital defects and skeletal dysplasias. Full article

In ultrasonic nondestructive testing (NDT), accurately estimating the time of flight (TOF) of ultrasonic waves is crucial. Traditionally, TOF estimation involves the signal processing of a single measured waveform. In recent years, deep learning has also been applied to estimate the TOF; however, these methods typically process only single waveforms. In contrast, this study acquired fan-beam ultrasonic waveform profile data from 64 paths using an ultrasonic-speed computed tomography (CT) simulation of a circular column and developed a TOF estimation model using two-dimensional convolutional neural networks (CNNs) based on these data. We compared the accuracy of the TOF estimation between the proposed method and two traditional signal processing methods. Additionally, we reconstructed ultrasonic-speed CT images using the estimated TOF and evaluated the generated CT images. The results showed that the proposed method could estimate the longitudinal TOF more accurately than traditional methods, and the evaluation scores for the reconstructed images were high. Full article

To estimate the possibility of using both low-melting TecaPEI and neat PEI films as energy directors (EDs) for ultrasonic welding (USW) of carbon fiber (CF) fabric–polyetherimide (PEI) laminates, some patterns of structure formation and mechanical properties of their lap joints were investigated by varying the process parameters. The experiment was planned by the Taguchi method with the L9 orthogonal matrix. Based on the obtained results, USW parameters were optimized accounting for maintaining the structural integrity of the joined components and improving their functional characteristics. The use of the low-melting ED_TecaPEI film enabled US-welding the laminates with minimal damage to the fusion zone, and the achieved lap shear strength (LSS) values of ~7.6 MPa were low. The use of ED_SolverPEI excluded thermal degradation of the components as well as damage to the fusion zone, and improved LSS values to 21 MPa. With the use of digital image correlation (DIC) and computed tomography (CT) techniques, the structural factors affecting the deformation behavior of the USW lap joints were justified. A scheme was proposed that established the relationship between structural factors and the deformation response of the USW lap joints under static tension. The TecaPEI film can be used in USW procedures when very high interlayer adhesion properties are not on demand. Full article

Marginal adaptation and internal porosity characteristics of root-end filling materials are important factors determining their clinical performance. The aim of this study was to quantitatively evaluate the marginal adaptation to radicular dentin (interfacial void volume) and internal porosity volume of a novel mineral trioxide aggregate brand using micro-CT analysis. Ten extracted upper central incisors were selected, instrumented, and obturated. Roots were resected at the apical 3 mm, and root-end cavities were prepared ultrasonically and filled with Harvard MTA. SkyScan 1272 micro-CT equipment was used to scan the specimens at a resolution of 6 μm, and three-dimensional images were reconstructed. All volumetric porosity parameters of the tested material were calculated in absolute (mm³) and relative values (%), as follows: open porosity volume (OPV), closed porosity volume (CPV), and total porosity volume (TPV). The mean OPV and OPV% found for Harvard MTA were 0.0268 mm³ and 0.91%, respectively. The mean CPV and CPV% were 0.0283 mm³ and 0.94%, respectively. The TPV and TPV% were 0.0569 mm³ and 1.85%. There was no significant difference between the OPV% and CPV% (p < 0.05). In conclusion, when applied as a retrofilling material, Harvard MTA exhibited excellent marginal adaptation to the dentin with minimal interfacial voids and internal microporosity. Therefore, this new calcium silicate brand may be considered an efficient alternative to conventional products. Full article

Rock fracture is a macroscopic fracturing process resulting from the initiation and propagation of microscopic cracks. Therefore, it is crucial to comprehend the damage and fracture mechanism of rock under ultrasonic vibration by investigating the evolutionary pattern of the meso-pore fracture structure in response to high-frequency vibrational loads, as explored in this study. Standard red sandstone samples with a diameter of 50 mm and height of 100 mm were subjected to ultrasonic high-frequency vibration tests. NMR and CT scans were conducted on the rock samples at different stages of ultrasonic vibration excitation to obtain the corresponding transverse relaxation time (T₂) spectra and CT scan images for each layer. The NMR test results revealed that smaller pores formed within the rock under high-frequency vibration loads, with a noticeable expansion observed in micropores. Three-dimensional reconstruction analysis based on two-dimensional CT images demonstrated an increase in pore count by 145.56%, 122.67%, and 98.87%, respectively, for the upper, middle, and lower parts of the rock after 120 s of ultrasonic vibration excitation; furthermore, the maximum pore volume increased by 239.42%, 109.16%, and 18.99%, respectively, for these regions during this period as well. These findings contribute towards a deeper understanding regarding the mechanisms underlying rock fragmentation when exposed to high-frequency vibrational loads. Full article

In this paper, we utilize micro-computed tomography (micro-CT) to obtain micro-CT images with a resolution of 60 μm and establish a micro-CT model based on the k-wave toolbox, which can visualize the microstructures in trabecular bone, including pores and bone layers. The transcranial ultrasound phased array focusing field characteristics in the micro-CT model are investigated. The ultrasonic waves are multiply scattered in skull and time delays calculations from the transducer to the focusing point are difficult. For this reason, we adopt the pulse compression method and the linear frequency modulation Barker code to compute the time delay and implement phased array focusing in the micro-CT model. It is shown by the simulation results that ultrasonic loss is mainly caused by scattering from the microstructures of the trabecular bone. The ratio of main and side lobes of the cross-correlation calculation is improved by 5.53 dB using the pulse compression method. The focusing quality and the calculation accuracy of time delay are improved. Meanwhile, the beamwidth at the focal point and the sound pressure amplitude decrease with the increase in the signal frequency. Focusing at different depths indicates that the beamwidth broadens with the increase in the focusing depth, and beam deflection focusing maintains good consistency in the focusing effect at a distance of 9 mm from the focal point. This indicates that the phased-array method has good focusing results and focus tunability in deep cranial brain. In addition, the sound pressure at the focal point can be increased by 8.2% through amplitude regulation, thereby enhancing focusing efficiency. The preliminary experiment verification is conducted with an ex vivo skull. It is shown by the experimental results that the phased array focusing method using pulse compression to calculate the time delay can significantly improve the sound field focusing effect and is a very effective transcranial ultrasound focusing method. Full article

Ultrasonic high-frequency vibrational fracture technology can compensate for the deficiencies of traditional fracture methods and has promising applications in underground rock drilling engineering. In this study, ultrasonic high-frequency vibrational tests were performed on brittle fine-grained red sandstone in combination with CT real-time scanning, which revealed mesoscopic fracture processes in the rock. Digital image processing technology is used to identify and extract the pores of CT images, and the pore evolution law of rock slices at different layers under ultrasonic vibration excitation is quantitatively studied. The results show that the increase in porosity decreases with increasing distance from the excitation surface, with the lowest layers of the rock showing an increase in porosity of only 0.22%. In addition, a mechanical model of rock breaking by ultrasonic vibrations was derived to explain the non-uniform damage mechanism of rock space under ultrasonic vibration excitation. Full article

The properties and appearance of ancient architectural red sandstone will be damaged after being eroded by the natural environment for a long time. In order to investigate the weathering and erosion characteristics of the red sandstone structure of an existing ancient building, ultrasonic testing techniques, combined with scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray computed tomography (X-CT), were used to analyze a building in Ganzhou. The variation in chemical substances contained in the red sandstone specimens according to phenology was analyzed by X-ray diffraction (XRD). The characteristic parameters of the CT grayscale images of the red sandstone were extracted and combined with the ultrasonic wave velocity values to comprehensively analyze the degradation characteristics of the red sandstone specimens, and a method to characterize the degradation degree of the red sandstone as a whole plane is proposed. We use the gray model (GM (1, 1)) to predict the surface degradation degree of red sandstone specimens, and gray relation analysis (GRA) to further analyze the correlation between the characteristic parameters of CT grayscale images of red sandstone and its degradation degree. The results show that in the natural erosion environment, dolomite and chlorite are generated on the exposed surface of the red sandstone, which can protect the internal sandstone to a certain extent. The degradation degree of the red sandstone specimens in the horizontal X and Y directions varies, and the proposed method of calculating the overall plane degradation degree of the red sandstone is feasible. The minimum average relative error of the surface degradation degree obtained from the gray prediction GM (1, 1) model is 1.4591%. There is a good correlation between the characteristic parameters of the red sandstone CT grayscale images and the degradation degree. Full article

The corrosion of concrete in sulfate environments is a difficult problem in the durability of civil engineering structures. To investigate the variability of deterioration damage to concrete structures by sulfate erosion under non-destructive testing and quantify the protective effect of silane coatings on concrete under the action of sulfate erosion, an accelerated erosion experiment was carried out using field sampling in a tunnel project under a sulfate erosion environment. By means of ultrasonic velocity measurement and CT scanning, the samples protected by a silane coating under the sulfate attack environment were compared with those not protected. The deterioration characteristics of concrete under the sulfate attack environment and the protective effect of silane coating on the concrete structure were analyzed. In addition, a method for evaluating the sulfate damage to concrete based on CT images and ultrasonic velocity analysis was proposed. The results show that the samples prepared in the field show a significant difference in ultrasonic velocity in the process of erosion and deterioration according to the material difference at the measuring point interface. Through the overall damage evaluation analysis of the sample, it is concluded that the damage degree of the protected group sample is light and the heterogeneity is weak, whereas the local damage to the exposed group is serious. Combined with the CT image analysis of concrete before and after loading, the distribution characteristics of the damaged area divided by the concrete sulfate damage evaluation method proposed in this paper are highly similar to the real situation. The results of the study can provide a reference for similar projects for the detection, analysis, protection and evaluation of sulfate-attacked concrete. Full article

In order to study the protection performance of silane coating on in-service concrete structures in a sulfate environment, we collect concrete samples in the field to simulate the concrete erosion process by accelerated erosion with wetting–drying cycles. We place the samples into protected, exposed and control groups corresponding to a corrosive environment with silane protection, corrosive environment without protection and general environment for three different service conditions. A combination of ultrasonic velocimetry, CT (Computed Tomography) scan imaging, NMR (Nuclear Magnetic Resonance) pore structure analysis, strength testing and other methods are used to analyze the strength, ultrasonic wave velocity, pore structure and other characteristics of the specimens during sulfate erosion. Based on the test results, the protective effect of silane coating on concrete structures under sulfate attack is quantitatively analyzed, and an index for judging the damage rate of specimens is proposed to quantitatively analyze the protective effect of silane coating. The research results show that the damage of the concrete structure under silane protection in a sulfate-attack environment can be reduced by more than 50%; its integrity damage index and strength damage index are easily affected by the location of local defects, which leads to a decrease in the protection efficiency of the surface silane coating. Full article

Coarse aggregate in concrete is basically free from sulfate corrosion. If the influence of the coarse aggregate in the concrete is not eliminated, the change amount of the concrete ultrasonic pulse velocity value is directly used to evaluate the damage degree of sulfate corrosion in the concrete, and the results are often inaccurate. This paper presents an evaluation method of corrosion damage for the sulfate-attacked concrete by CT, ultrasonic velocity testing and AHP methods. CT was used to extract the coarse aggregate information in the specimen, and the proportion of coarse aggregate on the ultrasonic test line was calculated based on CT image analysis. Then, the correction value of ultrasonic pulse velocity (UPV) of the concrete structure was calculated, and the sulfate corrosion degree of concrete structure was evaluated using the analytic hierarchy process (AHP). The results show that the evaluation method proposed in this paper could more accurately evaluate the corrosion damage in the sulfate-attacked concrete structures, and the evaluation results were more in line with reality. Full article

Additively manufactured (AM) materials and hot rolled materials are typically orthotropic, and exhibit anisotropic elastic properties. This paper elucidates the anisotropic elastic properties (Young’s modulus, shear modulus, and Poisson’s ratio) of Ti6Al4V alloy in four different conditions: three AM (by selective laser melting, SLM, electron beam melting, EBM, and directed energy deposition, DED, processes) and one wrought alloy (for comparison). A specially designed polygon sample allowed measurement of 12 sound wave velocities (SWVs), employing the dynamic pulse-echo ultrasonic technique. In conjunction with the measured density values, these SWVs enabled deriving of the tensor of elastic constants (C_ij) and the three-dimensional (3D) Young’s moduli maps. Electron backscatter diffraction (EBSD) and micro-computed tomography (μCT) were employed to characterize the grain size and orientation as well as porosity and other defects which could explain the difference in the measured elastic constants of the four materials. All three types of AM materials showed only minor anisotropy. The wrought (hot rolled) alloy exhibited the highest density, virtually pore-free μCT images, and the highest ultrasonic anisotropy and polarity behavior. EBSD analysis revealed that a thin β-phase layer that formed along the elongated grain boundaries caused the ultrasonic polarity behavior. The finding that the elastic properties depend on the manufacturing process and on the angle relative to either the rolling direction or the AM build direction should be taken into account in the design of products. The data reported herein is valuable for materials selection and finite element analyses in mechanical design. The pulse-echo measurement procedure employed in this study may be further adapted and used for quality control of AM materials and parts. Full article

This study aimed at analyzing and comparing the ease of removal of fractured nickel–titanium (NiTi) endodontic rotary files from the root canal system between the ultrasonic tips and the Endo Rescue appliance removal systems, as well as comparing the volume of dentin removed between ultrasonic tips and the Endo Rescue appliance using a micro-computed tomography (micro-CT) scan. Material and Methods: Forty NiTi endodontic rotary files were intentionally fractured in 40 root canal systems of 20 lower first molar teeth and distributed into the following study groups: A: Ultrasonic tips (n = 20) (US) and B: Endo Rescue device (n = 20) (ER). Preoperative and postoperative micro-CT scans were uploaded into image processing software to analyze the volumetric variations of dentin using an algorithm that enables progressive differentiation between neighboring pixels after defining and segmenting the fractured NiTi endodontic rotary files and the root canal systems in both micro-CT scans. A non-parametric Mann–Whitney–Wilcoxon test or t-test for independent samples was used to analyze the results. Results: The US and ES study groups saw 8 (1 mesiobuccal and 7 distal root canal system) and 3 (distal root canal system) fractured NiTi endodontic rotary files removed, respectively. No statistically significant differences were found in the amount of dentin removed between the US and ER study groups at the mesiobuccal (p = 0.9109) and distal root canal system (p = 0.8669). Conclusions: Ultrasonic tips enable greater ease of removal of NiTi endodontic rotary files from the root canal system, with similar amounts of dentin removal between the two methods. Full article

Dual-energy X-ray absorptiometry (DXA) machines based on bone mineral density (BMD) represent the gold standard for osteoporosis diagnosis and assessment of fracture risk, but bone strength and toughness are strongly correlated with bone collagen content (CC). Early detection of osteoporosis combined with BMD and CC will provide improved predictability for avoiding fracture risk. The backscattering resonance (BR) phenomenon is present in both ultrasound (US) and photoacoustic (PA) signal transmissions through bone, and the peak frequencies of BR can be changed with BM and CC. This phenomenon can be explained by the formation of standing waves within the pores. Simulations were then conducted for the same bone µCT images and the resulting resonance frequencies were found to match those predicted using the standing wave hypothesis. Experiments were performed on the same bone sample using an 808 nm wavelength laser as the PA source and 3.5 MHz ultrasonic transducer as the US source. The backscattering resonance effect was observed in the transmitted waves. These results verify our hypothesis that the backscattering resonance phenomenon is present in both US and PA signal transmissions and can be explained using the standing waves model, which will provide a suitable method for the early detection of osteoporosis. Full article