Cost function criteria using muscle synergies: Exploring the potential of muscle synergy hypothesis.

Background And Objective: Solving the redundant optimization problem for human muscles depends on the cost function. Choosing the appropriate cost function helps to address a specific problem. Muscle synergies are currently limited to those obtained by electromyography.

An Analysis of Trabecular Bone Structure Based on Principal Stress Trajectory.

To understand the mechanism of Wolff's law, a finite element analysis was performed for a human proximal femur, and the principal stress trajectories of the femur were extracted using the principal stress visualization method. The mechanism of Wolff's law was evaluated theoretically based on the distribution of the principal stress trajectories. Due to the dynamics of the loads, there was no one-to-one correspondence between the stress trajectories of the fixed load and the trabeculae in the cancellous architecture of the real bone.

Orthodontic craniofacial pattern diagnosis: cephalometric geometry and machine learning.

Efficient and reliable diagnosis of craniofacial patterns is critical to orthodontic treatment. Although machine learning (ML) is time-saving and high-precision, prior knowledge should validate its reliability. This study proposed a craniofacial ML diagnostic workflow base on a cephalometric geometric model through clinical verification.

Effect of remaining pericervical dentin on biomechanical behavior of endocrown-restored molars with different materials: Three-dimensional finite element and Weibull analyses.

To evaluate the effect of remaining pericervical dentin (PCD) on the biomechanical behavior of endocrown-restored molars with different materials, six three-dimensional finite element (FE) models were reconstructed with different thicknesses and heights of pulp-chamber lateral dentinal wall (PCLDW). IPS Empress 2, In-Ceram Zirconia, and Lava Ultimate were selected as the materials. Compared with the Lava Ultimate FE models, the maximum tensile stress in the FE models using ceramics was higher in the endocrown and lower in the PCD surrounding it, and the overall failure probabilities with different PCLDW thicknesses and heights were similar, ranging from 9.

Leveraging Multivariable Linear Regression Analysis to Identify Patients with Anterior Cruciate Ligament Deficiency Using a Composite Index of the Knee Flexion and Muscle Force.

Patients with anterior cruciate ligament (ACL) deficiency (ACLD) tend to have altered lower extremity kinematics and dynamics. Clinical diagnosis of ACLD requires more objective and convenient evaluation criteria. Twenty-five patients with ACLD before ACL reconstruction and nine healthy volunteers were recruited.

Finite element analysis of stress in oral mucosa and titanium mesh interface.

Background: The stiffness of titanium mesh is a double-blade sword to repair larger alveolar ridges defect with excellent space maintenance ability, while invade the surrounding soft tissue and lead to higher mesh exposure rates. Understanding the mechanical of oral mucosa/titanium mesh/bone interface is clinically meaningful. In this study, the above relationship was analyzed by finite elements and verified by setting different keratinized tissue width in oral mucosa.

Finite element analysis on pushing the molar backwards using invisible aligner with different migration displacement.

Purpose: This paper examines the biomechanical mechanism behind the effect of the invisible aligner technique on tooth movement processes.

Methods: To compare the effects of different target positions on tooth movement and the periodontal ligament (PDL), two kinds of aligners were designed to provide displacements of 0.2 mm (Model A) and 0.

Identification of Kinetic Abnormalities in Male Patients after Anterior Cruciate Ligament Deficiency Combined with Meniscal Injury: A Musculoskeletal Model Study of Lower Limbs during Jogging.

There is little known about kinetic changes in anterior cruciate ligament deficiency (ACLD) combined with meniscal tears during jogging. Therefore, 29 male patients with injured ACLs and 15 healthy male volunteers were recruited for this study to investigate kinetic abnormalities in male patients after ACL deficiency combined with a meniscal injury during jogging. Based on experimental data measured by an optical tracking system, a subject-specific musculoskeletal model was employed to estimate the tibiofemoral joint kinetics during jogging.

Relationship between high intra-abdominal pressure and compliance of the pelvic floor support system in women without pelvic organ prolapse: A finite element analysis.

Previous studies mainly focused on the relationship between the size of the prolapse and injury to the supporting tissues, but the strain and stress distributions of the supporting tissues as well as high-risk areas of injury are still unknown. To further investigate the effect of supporting tissues on organs and the interactions between organs, this study focused on the relationship between high intra-abdominal pressure and the compliance of the pelvic floor support system in a normal woman without pelvic organ prolapse (POP), using a finite element model of the whole pelvic support system. A healthy female volunteer (55 years old) was scanned using magnetic resonance imaging (MRI) during rest and Valsalva maneuver.

Three-dimensional radiological anatomy of condyle trabecular bone based on a Volume-of-Interest analysis.

Objectives: Three-dimensional radiological anatomic characteristics of condyle trabeculae was obtained quantitatively based on a volume-of-interest (VOI) analysis.

Methods: Nine human mandibular condyle specimens were scanned by micro-computed tomography (micro-CT). A total of 34 VOIs were selected from each condyle specimen, which were divided into six layers and four parts to analyze the morphological characteristics of trabeculae based on cylindrical VOIs with a diameter and height of 2 mm.

Influence of different diameter reductions in the labial neck region on the stress distribution around custom-made root-analogue implants.

This study was designed to investigate the influence of diameter reductions on the stress distribution around root-analogue implants via 3D finite element analysis. Four root-analogue implant models with different diameter reductions (0, 1, 2, or 3 mm), a traditional threaded implant and congruent bone models were created through reverse engineering. A 100-N force was applied parallel with and in a 45° angle to the implant axis, respectively.

The Biomechanical Response of the Cornea in Orthokeratology.

Orthokeratology has been widely used to control myopia, but the mechanism is still unknown. To further investigate the underlying mechanism of corneal reshaping using orthokeratology lenses the finite element method, numerical models with different corneal curvatures, corneal thicknesses, and myopia reduction degrees had been developed and validated to simulate the corneal response and quantify the changes in maximum stress in the central and peripheral corneal areas during orthokeratology. The influence of the factors on corneal response had been analyzed by using median quantile regression.

A Finite Element Analysis Model is Suitable for Biomechanical Analysis of Orbital Development.

The authors investigated orbital bone development in congenital microphthalmia (CM) using a three-dimensional finite element analysis model, after the orbital dimension deficiency was improved with a self-inflating hydrogel expander implant.Data of a 2-year-old male CM patient were examined. The orbital structure, eyeball, eye muscles, and self-inflating hydrogel expander were constructed according to computed tomography examination data.

Finite Element Analysis of Two- and Three-Dimensional Fixation in Treating Mandibular Symphyseal Fracture Combined With Bilateral Condylar Intracapsular Fractures.

The aim of this study was to compare through finite element analysis two- and three-dimensional (2D and 3D) fixation in the treatment of mandibular symphyseal fracture combined with bilateral condylar intracapsular fractures. The authors created 2 fixation models for the above fracture, and analyzed the stress and displacement in the mandible and fixation materials under 3 loading conditions. The von Mises stress of the mandible and plates peaked during lateral occlusion, and was lowest during central occlusion.

Use of the normalcy index for the assessment of abnormal gait in the anterior cruciate ligament deficiency combined with meniscus injury.

The normalcy index (NI) has been implemented by several studies as a simple index for quantitatively analyzing diffident gait abnormalities, such as children with cerebral palsy and idiopathic toe-walkers. However, whether the NI can be used in anterior cruciate ligament (ACL) deficiency with different types of meniscus injuries or not, has not been reported yet. In this study, 25 patients who combined different types of ACL and meniscus injuries were evaluated by the NI analysis.

Effect of central retainer shape and abduction angle during preparation of teeth on dentin and cement layer stress distributions in endocrown-restored mandibular molars.

To study the effect of central retainer shape and abduction angle during tooth preparation on stress distribution in endocrown-restored molars via finite element (FE) analysis, we constructed five FE models with different central retainer shapes and abduction angles. Under an oblique load, the distributions of maximum tensile stress in cervical dentin around the endocrown and on the cement layer, as well as maximum shear stress on the cement layer, were more balanced in the FE model in which the central retainer shape was generated based on the anatomical form of the pulp chamber. Moreover, there were no differences in stress distributions among FE models with different abduction angles.

Biomechanical comparison between the custom-made mandibular condyle prosthesis and total temporomandibular joint prosthesis in finite element analysis.

Purpose: The purpose of this study was to compare the biomechanical behavior of the custom-made mandibular condyle prosthesis and total TMJ prosthesis.

Methods: Three models of one beagle dog, the condyle prosthesis (Model 1, replacing the right condyle only), the TMJ prosthesis (model 2, replacing the whole right TMJ) and the intact TMJ (model 3) were established, and the mechanical responses under muscle forces loading were analyzed using finite element method.

Results: Models 1 and 3 had the similar stress distribution on the right disc, which suggested that the condyle prosthesis did not change the disc stress so much when the muscle forces were applied.

Anterior cruciate ligament deficiency combined with lateral and/or medial meniscal injury results in abnormal kinematics and kinetics during level walking.

Anterior cruciate ligament injuries are commonly combined with meniscal tears. This study was performed to analyze the kinematics and kinetics of knees with anterior cruciate ligament deficiency with or without a combined medial or/and lateral meniscal injury during level walking. In all, 29 patients with unilateral anterior cruciate ligament deficiency and 15 healthy male volunteers were recruited.

Effect of biomimetic material on stress distribution in mandibular molars restored with inlays: a three-dimensional finite element analysis.

Background: Although biomimetic material has become increasingly popular in dental cosmetology nowadays, it remains unclear how it would affect the restored teeth during chewing. It is necessary to study the influence of biomimetic material on stress distribution in the restored teeth.

Methods: Eight three-dimensional finite element (FE) models were constructed and divided into two groups.

Muscular Force Patterns during Level Walking in ACL-Deficient Patients with a Concomitant Medial Meniscus Tear.

Background: The abnormal knee joint motion patterns caused by anterior cruciate ligament (ACL) deficiency are thought to be associated with articular cartilage degeneration. High rates of meniscus tear combined with ACL rupture are observed, and these knees suffer a higher risk of early cartilage degeneration.

Research Question: This study investigated lower limb muscular force patterns of ACL-deficient knees with a concomitant medial meniscus tear.

Electron beam melting in the fabrication of three-dimensional mesh titanium mandibular prosthesis scaffold.

The study was designed to fulfill effective work-flow to fabricate three-dimensional mesh titanium scaffold for mandibular reconstruction. The 3D titanium mesh scaffold was designed based on a volunteer with whole mandible defect. (1) acquisition of the CT data; (2) design with computer aided design (CAD) and finite element analysis (FEA).