Three-dimensional Analysis Method Research Articles

New method to evaluate sequelae of static facial asymmetry in patients with facial palsy using three-dimensional scanning analysis

ObjectiveDuring the process of neural recovery after facial palsy, distressing sequelae of static and dynamic facial asymmetry develop in patients with facial palsy. A pronounced nasolabial fold is mainly responsible for static facial asymmetry, which leads to many psychological and social problems in patients. Objective and qualitative assessment of facial appearance is critical to determine the severity of sequelae of static facial asymmetry and whether an intervention is effective for treatment. In the present study, an attempt was made to develop three-dimensional analysis method to assess sequelae of static facial asymmetry after facial palsy. MethodsEight patients with sequelae of facial asymmetry after facial palsy and ten healthy volunteers were enrolled. We used three-dimensional scanning analysis with a portable non-contact optical scanner to obtain three-dimensional surface data from a patient's face and produced a three-dimensional digital model of the face. We then identified a reference plane fixed with the patient's face, and measured the depth of the nasolabial fold of the face. ResultsThe nasolabial fold of the face on the affected side was significantly deeper than that on the unaffected side in patients with sequelae of static facial asymmetry after facial palsy. However, the depth of the facial nasolabial fold on the right side was not different from that on the left side in healthy volunteers. Affected-unaffected side differences in the depth of the nasolabial fold in patients with sequelae of static facial asymmetry after facial palsy were significantly larger than left-right differences in the depth of the nasolabial fold in healthy volunteers. Two weeks after treatment with botulinum toxin injection to the affected zygomaticus muscles, affected-unaffected side differences in the depth of the nasolabial fold were significantly decreased in the patients. In the patients who received botulinum toxin, the absolute values of affected-unaffected side differences in the depth of the nasolabial fold measured using the three-dimensional scanning analysis showed a significant positive correlation with the visual analog scale scores of facial asymmetry marked by independent doctors. ConclusionThe present findings suggest that affected-unaffected side differences in the depth of the nasolabial fold of the measured using three-dimensional scanning analysis can be used as an index of sequelae of static facial asymmetry. It is also suggested that the index can evaluate whether interventions are effective for the treatment of sequelae.

Characterizing dissolved organic matter in Taihu Lake with PARAFAC and SOM method.

The three-dimensional fluorescence spectrum has a significantly greater amount of information than the single-stage scanning fluorescence spectrum. At the same time, the parallel factor (PARAFAC) analysis and neural network method can help explore the fluorescence characteristics further, thus could be used to analyse multiple sets of three-dimensional matrix data. In this study, the PARAFAC analysis and the self-organizing mapping (SOM) neural network method are firstly introduced comprehensively. They are then adopted to extract information of the three-dimensional fluorescence spectrum data set for fluorescence characteristics analysis of dissolved organic matter (DOM) in Taihu Lake water. Forty water samples with DOM species were taken from different seasons with the fluorescence information obtained through three-dimensional fluorescence spectrum analysis, PARAFAC analysis and SOM analysis. The PARAFAC analysis results indicated that the main fluorescence components of dissolved organic matter in Taihu Lake water were aromatic proteins, fulvic acids, and dissolved microorganisms. The SOM analysis results showed that the fluorescence characteristics of the dissolved organics in Taihu Lake varied seasonally. Therefore, the combined method of three-dimensional fluorescence spectrum analysis, PARAFAC and SOM analysis can provide important information for characterization of the fluorescence properties of dissolved organic matter in surface water bodies.

ANALYSIS OF STRESS DURING THE PLACEMENT OF REMOVABLE DENTURES OVER IMPLANTS

Implant-supported removable dentures are one of prosthetic dentistry modalities to replace missing teeth and have a long history of the development. Dentures placed over implants offer opportunities to restore dentition defects resulted from various causes. Different defects of the dentition require their own restorative techniques. In recent years, implant-supported prostheses have become more commonly preferred over full dentures. For patients with low distal bone levels and problems with placement and stabilization, 4-implantsupported dentures seem to be a good option. Four bar implants for supporting dentures are considered more reliable in terms of fixing the prosthetic structures over them. The aim of this work is to analyze the effect of implant-supported denture placement on the implants themselves and peripheral tissues, depending on the denture models, level of implant placement, the angle of placement, as well as the length of the console in the structure. Results. In 10 different mathematical models, the angles of implant placement in the bone were taken as equal to 90°, 17° and 30°, and the level of placement was equal to 1 mm and 3 mm (in accordance with the configuration of the jaw bone). The length of the cantilever bar system prepared on implants was 0 mm, 5 mm and 10 mm in different models. The load on the model was actually equal to the chewing pressure, 100 N (approximately 10.2 kg), when chewing a 1 cm solid food mass. The pressure was applied from 3 different points: from the anterior section, when the centre of the bolus was at the place of contact between the central incisors; in the right posterior region, when the centre of the bolus was at the contact between the 2nd premolar and the 1st molar; from the left posterior region, when the centre of the bolus was in the area of contact between the 2nd premolar with the 1st molar. After 3D analysis, the Von Mises stress findings in the implant area and the corresponding color scales were obtained, as well as the maximum and minimum stress values in accordance with the color scale. Conclusion. Based on the analysis and comparison of the obtained values, the study has determined that the stress distribution is optimal for some implant models, for others it can be too small or too large due to uneven stress values. The study of models based on the method of 3D three-dimensional stress analysis by the finite element method and the results of these studies are elucidated in the article.

A Novel Method for Quantitative Three-Dimensional Analysis of Zygomatico-Maxillary Complex Symmetry.

Objective:To develop a reliable and accurate method to quantify the symmetry of the zygomaticomaxillary complex (ZMC).Methods:Virtual three-dimensional models were created from 53 computed-tomography scans: 15 healthy cases without maxillofacial disorders and 38 patients with ZMC fractures requiring surgical treatment.Asymmetry of the ZMC was measured using a mirroring and surface-based matching technique that uses the anterior cranial fossa as reference to determine the symmetrical position of the ZMC. The measure for ZMC asymmetry was defined as mean surface distance (MSD) between the ZMC-surface and the symmetrical position.Reliability of the method was tested in the 15 healthy cases. Inter-and intra-observer correlation coefficients (Ce) and variabilities were assessed. Accuracy was assessed by comparing ZMC asymmetry between healthy and ZMC fracture cases, and by assessing correlation of ZMC fracture severity with ZMC asymmetry.Results:The average MSD of the 15 healthy cases was 1.40 ± 0.54 mm and the average MSD of the 38 ZMC fracture cases was 2.69 ± 0.95 mm (P < 0.01). Zygomaticomaxillary complex asymmetry correlated with fracture severity (P = 0.01). Intra-rater CC was 0.97 with an intra-rater variability of 0.09 ± 0.11 mm. Inter-rater Ce was 0.95 with an inter-rater variability of 0.12 ± 0.13 mm.Conclusions:Our method is reliable and accurate for quantitative three-dimensional analysis of ZMC-symmetry. It takes into account asymmetry caused by the shape of the ZMC as well as asymmetry caused by the position of the ZMC.Clinical relevance:This method is useful for the evaluation of ZMC asymmetry associated with congenital and acquired disorders of craniofacial skeleton, for surgical planning and for evaluation of postoperative results.

3D mesoscopic architecture of a heterogeneous cellular network in the cementum-periodontal ligament-alveolar bone complex.

Cell-to-cell communication orchestrates various cell and tissue functions. This communication enables cells to form cellular networks with each other through direct contact via intercellular junctions. Because these cellular networks are closely related to tissue and organ functions, elucidating the morphological characteristics of cellular networks could lead to the development of novel therapeutic approaches. The tooth, periodontal ligament (PDL) and alveolar bone form a complex via collagen fibres. Teeth depend on the co-ordinated activity of this complex to maintain their function, with cellular networks in each of its three components. Imaging methods for three-dimensional (3D) mesoscopic architectural analysis include focused ion beam/scanning electron microscopy (FIB/SEM), which is characterized by its ability to select observation points and acquire data from complex tissue after extensive block-face imaging, without the need to prepare numerous ultrathin sections. Previously, we employed FIB/SEM to analyse the 3D mesoscopic architecture of hard tissue including the PDL, which exists between the bone and tooth root. The imaging results showed that the cementum, PDL and alveolar bone networks are in contact and form a heterogeneous cellular network. This cellular network may orchestrate mechanical loading-induced remodelling of the cementum-PDL-alveolar bone complex as the remodelling of each complex component is coordinated, as exemplified by tooth movement due to orthodontic treatment and tooth dislocation due to occlusal loss. In this review, we summarize and discuss the 3D mesoscopic architecture of cellular networks in the cementum, PDL and alveolar bone as observed in our recent mesoscopic and morphological studies.

Toppling failure analysis of rock slopes based on a three-dimensional discontinuous deformation analysis method

The present study focused on the study of the toppling failure of rock slopes using a three-dimensional discontinuous deformation analysis (3D DDA) method. The failure conditions and their related impact factors of toppling rock slopes were derived by building the corresponding mathematical models based on the limit equilibrium method (LEM), and the deficiency of the existed LEM for analysing the toppling system was pointed out. Several numerical examples, such as a single rock block of different dimensions, classical toppling rock slope model, and multiple rock blocks of different distributions, were adopted to investigate the toppling failure mechanisms under different conditions. The results showed that the 3D DDA is a very powerful numerical tool to study the failure mechanisms of toppling rock slopes and simulate the failure process of various toppling rock slopes with different distributions of structural planes inside rock mass. The controversial safety factor of the slope stability was avoided in the 3D DDA numerical simulation. Through the 3D DDA results, some more real phenomena of slope failure could also be observed and explained. For example, the slope block toppling tended to be toppling-sliding rather than pure toppling. In addition, the general laws of toppling slope failure were presented.

Three-Dimensional Surface Texture Analysis of Fluoride's Effect on Enamel Erosion.

Enamel erosion has become a common clinical finding that often impairs dental esthetics and function. In the current study, we aimed to implement the three-dimensional surface texture analysis (3DST) method to explore the protective effect of fluoride on surface texture prior to erosive conditions. For each of the 50 teeth used in this study, the polished buccal enamel surface was divided into three separate areas: the first area was untouched polished enamel, the two other surfaces were immersed in 0.3% citric acid for 30 s. One was treated with high-concentration (19,000 ppm) sodium fluoride (NaF) solution prior to acid attack, and the other had no treatment prior to acid exposure. Enamel surface texture and step height measurements were obtained using a high-resolution disk scanning confocal microscope, and SEM images were also acquired. Surfaces treated with fluoride showed fewer variations in 3-D surface texture parameters than the eroded surface compared to the control group (p = 0.001). This was in accordance with the SEM descriptive images. The findings indicate that pre-fluoridated enamel areas were less affected by the acid and showed similar features to the untouched enamel. Moreover, a protective effect of the fluoride treatment against irreversible enamel damage was noted as the surface loss (step-height) was significantly reduced (p = 0.03). The study showed that 3DST analysis is a valuable methodology for detecting and quantifying subtle differences between the surfaces. When exploring the combination of all surface texture parameters, it was revealed that the pre-fluoridated eroded enamel surfaces showed considerable similarity to the untouched enamel.

In-House, Open-Source 3D-Software-Based, CAD/CAM-Planned Mandibular Reconstructions in 20 Consecutive Free Fibula Flap Cases: An Explorative Cross-Sectional Study With Three-Dimensional Performance Analysis

BackgroundMandibular reconstruction is conventionally performed freehand, CAD/CAM-assisted, or by using partially adjustable resection aids. CAD/CAM-assisted reconstructions are usually done in cooperation with osteosynthesis manufacturers, which entails additional costs and longer lead time. The purpose of this study is to analyze an in-house, open-source software-based solution for virtual planning.Methods and MaterialsAll consecutive cases between January 2019 and April 2021 that underwent in-house, software-based (Blender) mandibular reconstruction with a free fibula flap (FFF) were included in this cross-sectional study. The pre- and postoperative Digital Imaging and Com munications in Medicine (DICOM) data were converted to standard tessellation language (STL) files. In addition to documenting general information (sex, age, indication for surgery, extent of resection, number of segments, duration of surgery, and ischemia time), conventional measurements and three-dimensional analysis methods (root mean square error [RMSE], mean surface distance [MSD], and Hausdorff distance [HD]) were used.ResultsTwenty consecutive cases were enrolled. Three-dimensional analysis of preoperative and virtually planned neomandibula models was associated with a median RMSE of 1.4 (0.4–7.2), MSD of 0.3 (-0.1–2.9), and HD of 0.7 (0.1–3.1). Three-dimensional comparison of preoperative and postoperative models showed a median RMSE of 2.2 (1.5–11.1), MSD of 0.5 (-0.6–6.1), and HD of 1.5 (1.1–6.5) and the differences were significantly different for RMSE (p < 0.001) and HD (p < 0.001). The difference was not significantly different for MSD (p = 0.554). Three-dimensional analysis of virtual and postoperative models had a median RMSE of 2.3 (1.3–10.7), MSD of -0.1 (-1.0–5.6), and HD of 1.7 (0.1–5.9).ConclusionsOpen-source software-based in-house planning is a feasible, inexpensive, and fast method that enables accurate reconstructions. Additionally, it is excellent for teaching purposes.

Remnant photosynthetic pigments in tea dregs: identification, composition, and potential use as antibacterial photosensitizer

The production of tea dregs is continually increasing along with the growth of people's interest in ready-to-drink beverages. However, the recent development of research on the use of tea dregs is still very limited. The present study was aimed to identify the remnant photosynthetic pigments in tea dregs, determine their composition, and evaluate their potential use as natural antibacterial agents based on light-induced reaction (photosensitization). The tea dregs from six commercial teas, consisting of green and black teas, were analyzed using high-performance liquid chromatography (HPLC) with a photodiode array detector, and the spectroscopic data were analyzed from 350 to 700 nm. Pigment identification was performed based on spectral characteristics, and pigment composition in the extracts from the dregs was determined by a three-dimensional multi-chromatogram analysis method. The dominant pigment fractions in both tea types were pheophytin a and its isomers, as well as pheophytin b. Although the dregs of black teas generally contain fewer remnant pigments, they possess residual chlorophyll b, which is not found in the dregs of green teas. In thirty-minutes illumination under 50 W red light-emitting diode, the presence of pigments from tea dregs caused up to 0.87 and 0.35 log reduction of Staphylococcus aureus and Escherichia coli, respectively. The disparity of pigments composition among tea types does not strongly influence their photosensitization activity against both bacteria. Hence, upon further application, the amount of total remnant pigments in the dregs could be taken as substantial consideration instead of tea types.

Mathematical Simulation and Experimental Verification of Carburizing Quenching Process Based on Multi-Field Coupling

Based on the multi-field coupling effect of temperature, diffusion, and phase change, the finite element model of carburizing and quenching was established. The 20CrMnTiH steel helical gear as the research object, prediction accuracy of carburizing, and quenching model of complex helical gear was studied. The material properties database of experimental steel was established by JMatPro, and the material thermophysical parameters needed in the calculation process were obtained. The carburizing and quenching process of transmission helical gear was numerically simulated by thermodynamic three-dimensional coupling analysis method combined with actual heat treatment process. The microstructure morphology, macro hardness, and deformation were characterized. The experimental results show that the microstructure of the hardened surface layer was acicular martensite and a small amount of residual austenite. The highest hardness appears at the surface layer of 778.8 HV, the effective hardened layer depth was 0.9 mm, and the maximum deformation of the gear was 0.055 mm. By comparing the experimental measurement results with the simulation results, they were in good agreement, which verifies the accuracy of the finite element model. This indicates that the model has good prediction ability in carburizing and quenching process.

Scanning Optical Probe Nanotomography for Investigation of the Structure of Biomaterials and Cells.

Creation of new effective bio-artificial structures for tissue engineering and regenerative medicine requires development and implementation of new technological approaches for analysis of micro- and nanostructural features of constructs based on biomaterials and their interaction with cells. A new method of three-dimensional multiparametric analysis of nanostructure, scanning optical probe nanotomography, is presented in this paper, applied to the analysis of cells and biomaterials. Correlative reconstruction of fluorescent marker distributions and nanostructure features allows quantitative evaluation of a number of parameters of three-dimensional nanomorphology of fibroblasts and human hepatocarcinoma cells Hep-G2, adhered to biodegradable scaffolds based on silk fibroin. The developed technology with use of scanning optical probe nanotomography is applicable to investigation of three-dimensional micro- and nanostructure features of biomaterials and cells of different types.

Matrix Composition Modulates Vitamin D3's Effects on 3D Collagen Fiber Organization by MCF10A Cells.

Vitamin D3 (vitD3) has been implicated in various cellular functions affecting multiple tissue types. Epidemiological and laboratory studies suggest that vitD3 may be effective as a preventive or therapeutic option for breast cancer. However, randomized clinical trials have yet to confirm these suggestions. Breast neoplasias can arise from developmental alterations; based on this evidence, we seek to understand vitD3's role in normal breast development, particularly its role in epithelial morphogenetic processes such as ductal elongation, branching, and alveolar formation. These processes require extensive changes in the extracellular microenvironment, such as collagen fiber organization, and are largely influenced by hormones. Here, we build upon our past work to shed light on calcitriol's effects on collagen fiber organization by breast epithelial cells, and how such effects are modulated by extracellular matrix composition. We embedded MCF10A normal human breast epithelial cells in two different matrices-collagen type I and collagen type I + 10% Matrigel; treatment with calcitriol resulted in flatter epithelial structures. Next, using two-photon microscopy, we examined changes in collagen fiber organization and corresponding changes in epithelial structures. Applying a novel three-dimensional (3D) image analysis method, we show that increasing doses of calcitriol result in denser collagen fiber bundles in the localized area surrounding the epithelial structures, and that these bundles are aligned in a more parallel direction to epithelial structures when exposed to the highest vitD3 dose. Changed patterns in fiber organization may explain the flattening of epithelial structures; in turn, changes in biophysical forces in the matrix abutting these structures may be responsible for changes in the referred patterns. Addition of 10% Matrigel dampened the effects of calcitriol on both epithelial morphogenesis and fiber organization. Overall, we report novel functions of calcitriol in the breast epithelium and add to the growing body of evidence documenting how hormones affect biophysical processes. Impact statement In this study, we report novel functions of calcitriol in the breast epithelium and use a novel quantitative metric to parse the effects of calcitriol on collagen fiber organization that cannot be detected through conventional histological procedures. Despite the large body of literature on vitamin D3 (vitD3) and calcitriol's effects on cellular functions across tissue types, little is known about how they affect collagen fiber organization, an early critical step for breast epithelial development. This work provides further evidence that hormones affect morphogenesis by means of biophysical forces, with implications for a comprehensive view on vitD3's effects in breast development and neoplasia.

A novel meshfree method for three-dimensional natural frequency analysis of thick laminated conical, cylindrical shells and annular plates

In this paper, a novel meshfree approach for three-dimensional free vibration analysis of thick laminated composite conical, cylindrical shells and annular plates is presented. The theoretical model for free vibration analysis of thick shells and plates is formulated by applying the three-dimensional theory of elasticity, and all displacement components are approximated by a novel meshfree Tchebychev-point interpolation method (TPIM) shape function using Tchebychev polynomials as a basis. After deriving the governing equations and boundary conditions for individual layers of the laminated shell, the governing equations and boundary conditions of the entire system are derived by combining them according to the order of layers. The boundary and combination conditions are generalized by introducing the artificial spring technique, and the type of conditions is selected by the spring stiffness values. The accuracy and reliability of the proposed method are verified by comparison with the results of literatures and finite element software ABAQUS. The free vibration characteristics such as the natural frequency and mode shape of laminated conical, cylindrical shells and annular plates under different boundary conditions are presented through some numerical examples.

A study of human motion in computer vision systems based on a skeletal model

Methods of studying human motion in computer vision systems can be divided into two types. These are analysis in two-dimensional and three-dimensional space. The former uses a single camera image and/ or multiple body sensors. Such an approach leads to a rapid accumulation of error and, consequently, low accuracy of the figure representation. Multiple cameras are usually used in the case of three-dimensional space analysis, while the objects are represented as sets of volumetric elements. Despite the high accuracy of this method, it is associated with high computational complexity and internal network load. The purpose of the paper is to develop a model using a single camera, while approaching three-dimensional space analysis methods in terms of accuracy. In this paper a human figure is represented as a skeleton. The skeleton is described by an acyclic connected graph. The general structure of a human figure is analyzed. Fifteen basic points are selected. Physical and logical connections between them were studied and mathematically described. The velocity and spatial characteristics of the points and connections outline the general dynamics of motion. The study describes a model of human motion and gives the option for model construction on the example of a particular image. The developed algorithm for collection and analysis of information estimates relative locations and velocity characteristics of the graph elements. The model can be used for acquisition of information about the reference dynamics of human movements. In case of detecting major differences between the reference and the reality, the behavior is defined as deviant. Thus, the obtained algorithm can be applied in computer vision systems for detection and analysis of human movements.

THREE DIMENSIONAL GAIT ANALYSIS OF EXERCISE REHABILITATION AND MUSCLE TENSION

ABSTRACT Introduction: Timely assessment and correction of post-stroke hemiplegia gait, to improve walking ability, has become an urgent problem for patients with hemiplegia. Objective: In order to improve the effect of exercise rehabilitation and tensile strength testing, a three-dimensional gait analysis method was proposed. Methods: The kinematics, dynamics, ground reaction force and surface EMG of lower limbs were measured by VICON (Nexus 1.8.5), a three-dimensional gait analysis system, and Noraxon, a wireless surface EMG, while 13 healthy subjects walked. The intra-group correlation coefficient (ICC) and standard error of measurement (SEM) were used to compare the relative and absolute reliability of the two test results. Results: the re-testability ICC was 78~0.96, the standard error SEM% of kinematics parameters was 4.18~15.6, and the SEM% of dynamic parameters was 3.31~21.82. The SEM% of ground reaction force was 1.70~16.67, and the SEM% of surface EMG signal was 8.00~11.11. Conclusions: 3D gait analysis can improve the effect of exercise rehabilitation and tensile strength testing, and has good retesting reliability. Level of evidence II; Therapeutic studies - investigation of treatment results.

A Three-Dimensional Buffer Analysis Method Based on the 3D Discrete Global Grid System

Three-dimensional (3D) buffer analysis is among the basic functions of 3D spatial analysis, and it plays an important role in 3D geographic information systems. The rapid development of the 3D Discrete Global Grid System (DGGS) provides a new method for the 3D spatial analysis of geographic information. According to the spatial topology characteristics of the 3D DGGS and the concept of dimensionality reduction, a 3D buffer analysis method based on the spatial grid of the Earth system is proposed to solve the problem of the buffer algorithm of a space object being unsatisfactory at present. In this paper, we present a method to calculate the distance between cells based on the side length of the spherical grids according to the geometric characteristics of the grids. For the grids of a geographic object, we describe the Euclidean distance expansion algorithm and the radial elevation expansion algorithm that helped us to obtain its 3D buffer. Finally, in terms of algorithm complexity and visualization effect, compared with the traditional raster buffer algorithm, the method presented in this paper has lower complexity, an improved visualization effect, and stronger generality.

Research on an Optimized Hob to Increase the Bending Strength of Involute Gears by Changing the Root Fillet Profile

An optimized hob to increase the bending strength of involute gears by changing the root fillet profile is presented in this paper. The maximum bending stress which determines the service life of a gear in many applications depends on stress concentration caused by the gear root fillet. Better control of the root fillet can result in gears with higher bending strength. The optimised hob tool is a modification based on the standard hob tool, with constant normal base pitch, but a different pressure angle and module, which will generate a different gear root fillet area. The comparison analysis demonstrates that the gear generated by the optimised hob has higher bending strength than that generated by the common standard hob. For analysis and validation of results, three methods of predicting bending stress - ISO standard, three-dimensional tooth contact analysis (3D-TCA) method, and finite element analysis (FEA) are applied and discussed.

A quasi-Monte Carlo statistical three-dimensional tolerance analysis method of products based on edge sampling

PurposeThe conventional statistical method of three-dimensional tolerance analysis requires numerous pseudo-random numbers and consumes enormous computations to increase the calculation accuracy, such as the Monte Carlo simulation. The purpose of this paper is to propose a novel method to overcome the problems.Design/methodology/approachWith the combination of the quasi-Monte Carlo method and the unified Jacobian-torsor model, this paper proposes a three-dimensional tolerance analysis method based on edge sampling. By setting reasonable evaluation criteria, the sequence numbers representing relatively smaller deviations are excluded and the remaining numbers are selected and kept which represent deviations approximate to and still comply with the tolerance requirements.FindingsThe case study illustrates the effectiveness and superiority of the proposed method in that it can reduce the sample size, diminish the computations, predict wider tolerance ranges and improve the accuracy of three-dimensional tolerance of precision assembly simultaneously.Research limitations/implicationsThe proposed method may be applied only when the dimensional and geometric tolerances are interpreted in the three-dimensional tolerance representation model.Practical implicationsThe proposed tolerance analysis method can evaluate the impact of manufacturing errors on the product structure quantitatively and provide a theoretical basis for structural design, process planning and manufacture inspection.Originality/valueThe paper is original in proposing edge sampling as a sampling strategy to generating deviation numbers in tolerance analysis.

Biomechanical evaluation of stress distributions at the implant-abutment complex and peri-implant bone around mandibular dental implants with different neck geometries and inclinations.

This study aimed to investigate the effects of the different dental implant neck designs, diameters, and inclinations, on the stress distributions at the mandibular crestal bone and implant-abutment complex, using three-dimensional (3D) finite element stress analysis (FEA) method. Finite element models of three-unit fixed partial dentures supported with two same length implants (10 mm), placed on the second premolar and second molar regions, were designed. Eight different models were designed according to the implants' neck designs (platform switching/traditional), diameters (4.1 mm/4.8 mm) and the tilting angles of the posterior implants (0°/15°). The anterior implants' widths were 4.1 mm and the neck design of the anterior implants matched the posterior implants. Two types of 100-N loads in vertical and 30° oblique directions were applied separately onto each central fossae and functional cusps of the fixed partial dentures crowns. Algor Fempro Software was used for the simulation and evaluation of the stress levels at the implant-abutment complex and the crestal bone. Stress levels measured at the crestal bone were found to be lower for the platform switching models. However, the platform switching design generated higher stress magnitudes within the implant-abutment complex. Inclined placement of posterior implants increased the amount of stress at the crestal bone around both implants. Biomechanically, selection of the largest diameter possible when using tilted platform switched implants may be recommended at the posterior mandible.

Influences of Pore-Water Pressure on Slope Stability considering Strength Nonlinearity

The pore-water pressure is a vital factor in determining the slope stability. To deal with the stability of slopes undergoing pore-water pressures, this paper used the pore-water pressure coefficient to develop the three-dimensional limit analysis method for slope stability evaluation with a nonlinear strength envelope. For numerical slope examples, the critical heights and corresponding critical slip surfaces associated with linear and nonlinear envelopes were derived by using a numerical optimization procedure. The influences of pore-water pressures on the slope stability were addressed by comparing the upper-bound solutions derived by linear and nonlinear strength envelopes (the linear and nonlinear results for short). The obtained two critical inclinations between the linear and nonlinear results both decrease and gradually approach with increasing pore-water pressure coefficient. For most slopes subjected to pore-water pressures, using the linear Mohr–Coulomb envelope will obviously overestimate the slope critical height. The overestimation resulted from the linear criterion will become more distinct for slopes with smaller widths. Besides, the presented results showed that the equivalent internal friction angle tends to have a weaker increasing trend for steeper slopes as pore-water pressure coefficient increases. Hence, when pore-water pressure coefficient increases, the critical slip surfaces of gentle slopes with nonlinear strength criteria become shallower, but the critical slip surfaces of steep slopes seem to have no consistent change law. These results and analyses can illustrate the significance of the application of nonlinear strength envelopes in slope stability evaluation considering pore-water pressures and provide certain reference advice in slope engineering design and landslide prevention.