experimental test for mechanical properties of a vascular stent is a main method to evaluate its effectiveness and safety, which is of great significance to the clinical applications. In this study, a comparative study of planar, V-groove and radial compression methods for the radial support property test were performed, and the effects of compression rate and circumferential position on the test results were conducted. Based on the three-point bending method, the influences of compression rate and circumferential position on flexibility were also explored. And then a best test proposal was selected to evaluate the radial support property and flexibility of the three self-designed stents and the comparative biodegradable vascular stent (BVS) (BVS1.1, Abbott Vascular, USA) with different outside diameters of 1.4 mm, 1.7 mm and 2.4 mm. The results show that the developing trends of the compression load with the compression displacement measured by the three radial support property test methods are the same, but normalized radial force values are quite different. The planar compression method is more suitable for comparing the radial support properties of stents with different diameters and structures. Compression rate has no obvious effect on the testing results of both the radial support property and flexibility. Compression circumferential position has a great impact on testing radial support property with the planar or V-groove compression methods and testing flexibility with three-point bending method. The radial support properties of all the three self-designed stents are improved at a certain degree compared to that of the BVS stent. The study has better guide significance and reference value for testing mechanical properties of vascular stents.
Absorbable Implants ; Mechanical Phenomena ; Polymers ; Prosthesis Design ; Stents ; Stress, Mechanical

Stress, Mechanical ; Biomechanical Phenomena ; Head ; Brain

A novel testing system is designed to simulate the mechanical performance and evaluate the biomechanical properties of the bone and the corresponding bone fixator. It is mainly composed of movement platform and servo motor system, sensors and hardware circuit system and software system. In order to prove the feasibility of the design, on the basis of the calibration for the force sensor, the fatigue experiment is carried out using the tibia of the sheep. It is concluded from the result that under the condition of 1 Hz in frequency, 50 kg in loading force and 18 000 cycles, the bone fixator can be still in good condition, which proves the feasibility of the design.
Animals ; Biomechanical Phenomena ; Bone Screws ; Mechanical Phenomena ; Sheep ; Stress, Mechanical ; Tibia ; physiology

The biomechanical properties of eight human corneas from four normal Chinese fresh corpses were investigated by use of one dimension tensile test, tensile stress relaxation and creep test. The destructive load, stretchy ratio, spreading stress, spreading strain and elastic modulus were determined. Also obtained were the stress relaxation and creep data and curves. After reduction of data, the reduced stress relaxation and creep data and curves were worked out. The regression method was used to get the regression coefficient. The least square method was employed to fit the data of stress and strain; then the stress-strain formula was expressed and the curves of human cornea were plotted. The constitutive equation is K (lambda,t) = G(t) T(e) (lambda) and some conclusions are drawn.
Biomechanical Phenomena ; Cornea ; physiology ; Elastic Modulus ; Humans ; Stress, Mechanical

By creating two kinds of stress environment in the same animal model, we performed a three-point bending test and a compressing test on the rat femurs growing under different stress conditions to characterize the effect of stress on bone mechanical properties. The right hindlimbs were subjected to sciatic nerve resection to become cripple and were used as unloading group; the left hindlimbs bore excess load and made up the overloading group; the normal rats were used as control group. The animals were encouraged to exercise for half an hour everyday in the morning, noon and evening. The experiment observation finished in four weeks. The biomechanical parameters of femur diaphyses were measured. The experiment results showed that stress environment may change several mechanical parameters of rat femurs. This study indicated that bone tissues can adapt to its stress environment by changing its mechanical properties. The experimental model in this article is practical and reliable.
Animals ; Biomechanical Phenomena ; Diaphyses ; physiology ; Femur ; physiology ; Rats ; Stress, Mechanical

OBJECTIVETo investigate the influence of post-core structure on the strength of endodontically treated and crowned teeth with or without a 2.0 mm dentine ferrule.

METHODSA total of 60 recently extracted human maxillary central incisors were endodontically treated and randomly divided into five groups of 12. They were given following treatments: Group A, endodontically treated; Group B, endodontically treated and crowned (PFM); Group C, cast metal post-core with 2.0 mm dentine ferrule and crowned (PFM); Group D, cast metal post-core with no dentine ferrule and crowned (PFM); Group E, prefabricated post and composite core with 2.0 mm dentine ferrule and crowned (PFM). All specimens were stored at 100% humidity at room temperature for 30 days before testing. Each specimen was in a special jig on the MTS 810 universal material testing machine and subjected to a load at a 135-degree angle to the long axis until failure, with crosshead speed of 0.02 cm/minute. Analysis of variance followed by the Newman-Keuls pairwise multiple comparison tests was used to compare the results.

RESULTSThere was a statistically significant difference between different restorative methods. The cast metal post-core with 2.0 mm dentine ferrule and crowned teeth had the highest fracture strength (1793.59 +/- 387.93N), followed by endodontically treated intact teeth (1466.68 +/- 240.11N). No significant difference in the fracture strength was found among the other three groups (958.49 +/- 286.02N; 992.98 +/- 291.00N; 994.94 +/- 285.04 N). There was a statistically significant difference in the fracture resistance between crowned teeth with and without 2.0 mm dentine ferrule (P < 0.01).

CONCLUSIONSNot all post-core structure could improve the strength of endodontically treated teeth. The dentine ferrule can effectively improve the fracture resistance of endodontically treated and crowned teeth.

The radial force of the degradable esophageal stent before and after degradation is one of the important indicators for effective treatment of esophageal stricture. Based on a combination of in vitro experiments and finite element analysis, this paper studies and verifies the biomechanical properties of a new type of degradable esophageal stent under different esophageal stricture conditions. Under radial extrusion conditions, the maximum stress at the port of the stent is 65.25 MPa, and the maximum strain is 1.98%; The peak values of stress and strain under local extrusion and plane extrusion conditions both appear in the extrusion area and the compression expansion area at both ends, which are respectively 48.68 MPa, 46.40 MPa, 0.49%, 1.13%. The maximum radial force of the undegraded stent was 11.22 N, and 97% and 51% of the maximum radial force were maintained after 3 months and 6 months of degradation, respectively. The research results verify the safety and effectiveness of the radial force of the new degradable esophageal stent, and provide a theoretical basis for the clinical treatment of esophageal stricture.
Esophageal Stenosis/surgery* ; Finite Element Analysis ; Humans ; Mechanical Phenomena ; Stents

Atherosclerotic plaque rupture is the main cause of many cardiovascular diseases, and biomechanical factors play an important role in the process of plaque rupture. In the study of plaque biomechanics, there are relatively few studies based on fatigue fracture failure theory, and most of them mainly focus on the whole fatigue propagation process from crack initiation to plaque rupture, while there are few studies on the influence of crack on plaque rupture at a certain time in the process of fatigue propagation. In this paper, a two-dimensional plaque model with crack was established. Based on the theory of fracture mechanics and combined with the finite element numerical simulation method, the stress intensity factor (SIF) and related influencing factors at the crack tip in the plaque were studied. The SIF was used to measure the influence of crack on plaque rupture. The results show that the existence of crack can lead to local stress concentration, which increases the risk of plaque rupture. The SIF at the crack tip in the plaque was positively correlated with blood pressure, but negatively correlated with fibrous cap thickness and lipid pool stiffness. The effect of the thickness and angle of lipid pool on the SIF at the crack tip in the plaque was less than 4%, which could be ignored. This study provides a theoretical basis for the risk assessment of plaque rupture with cracks.
Biomechanical Phenomena ; Computer Simulation ; Humans ; Plaque, Atherosclerotic ; Stress, Mechanical

Micromotion and fretting damages at the dental implant/bone interface are neglected for the limitation of check methods, but it is particularly important for the initial success of osseointegration and the life time of dental implant. This review article describes the scientific documentation of micromotion and fretting damages on the dental implant/bone interface. The fretting amplitude is less than 30 µm in vitro and the damage in the interface is acceptable. While in vivo, the micromotion's effect is the combination of damage in tissue level and the real biological reaction.
Biomechanical Phenomena ; Bone and Bones ; anatomy & histology ; physiology ; Dental Implants ; Humans ; Mechanical Phenomena ; Movement ; Osseointegration ; physiology ; Stress, Mechanical ; Surface Properties

Biomechanical Phenomena ; Humans ; Skin Physiological Phenomena ; Skin, Artificial ; Stress, Mechanical ; Tensile Strength