Biomedical subjects

Mengshi Chen

Publications and source records attributed to Mengshi Chen.

10 recordsLinked to original sources

PubMed2006

[Development of a functional mandibular model].

This study was conducted to establish a functional mandibular biomechanical model for use in the follow-up biomechanical study of the integrated and fractured mandible. The integrated and dry human mandible was used, and the corresponding maxilla and cranial base was duplicated by resin and plaster. 2-mm silicon rubber was used for simulation of the temporomandibular joint (TMJ) disc. A simulated TMJ and physiological mandibular model was developed by four pairs of muscular loadings (Masseter= 180 N, Temporalis = 190 N, Medial Pterygoideus = 120 N, Lateral Pterygoideus = 40 N) in each muscular center, and the functional loading corresponding with physiological condition was reflected and simulated more realistically when compared with that of the previously reported mandibular models which were developed by occlusion loading or by only one pair of muscles loading. In summary, we have established a functional mandibular model which can be used to analyze the biomechanical behavior in various functional conditions.

Biomechanical Phenomena↗

PubMed2006

[Testing of anisotropic modulus and fluid characteristic of Chinese femur and tibia].

The tension moduls and compression modulus of Chinese tibia and femur of male in three different directions, namely axial, circumferential and radial directions, were tested in our experiments. The measured compression moduli are 5.8 +/- 0.34, 3.4 +/- 0.17, 2.1 +/- 0.18 GPa respectively for femur, and 6.1 +/- 0.36, 3.5 +/- 0.17, 2.1 +/- 0.18 GPa respectively for tibia; the measured tension moduli are 15.6 +/- 1.21, 9.8 +/- 0.73, 5.4 +/- 0.52 GPa respectively for femur, and 16.7 +/- 1.09, 10.3 +/- 0.70, 5.6 +/- 0.49 GPa respectively for tibia. The tension and compression ultimate strengths of femur and tibia were tested, too. The measured compression ultimate strengths are 150 +/- 9.3, 111 +/- 6.5, 110 +/- 7.1 MPa respectively for femur, and 191 +/- 12.3, 140 +/- 6.3, 123 +/- 8.3 MPa respectively for tibia; the measured tension ultimate strengths are 115 +/- 9.6, 82 +/- 6.8, 78 +/- 7.3 MPa respectively for femur, and 143 +/- 8.7, 110 +/- 8.3, 97 +/- 6.4 MPa respectively for tibia. Furthermore, the stress-relaxation experiments were conducted. The relation between loading and time during the experiments were obtained by the method of curve fitting. They meet the logarithm function: F = A * B(log t); A is the initial load, and B is the fitting material parameter. For femur, B is equal to 0.985; for tibia, B is equal to 0.987.

Anisotropy↗

PubMed2006

[The effect of mechanical strain on proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells from rats].

In order to investigate the effects of cyclic biaxial mechanical strain on proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (MSCs)from rats. The MSCs were isolated from bone marrow in the 9-month-old female Sprague-Dawley rats by a density gradient method. After the third passage,1 x 10(5) cells were seeded on the flexible silicone membrane in the cyclic biaxial mechanical strain unit. The amplitude of mechanical strain applied to the cells were 4000 microstrain, at a frequency of one hertz (1 Hz), for periods of 3 repetitions of 2 hours' mechanical strain and a break of 2 hours. The osteoblastic marker such as osteopontin (OPN),alkaline phosphatease (ALP), osteocalcin (OCN), type I collagen (Col I) were detected by RT-PCR. The proliferation of all cells were studied with Flow Cytometry (FCM). ALP and OPN levels significantly increased in the mechanical strained groups and reached the top at 3th day after mechanical strain. COL I level was increase only at 3th day after mechanical strain, and the change of OCN was not obvious in every group. The proliferation index of the medchanical strained groups was increased, compared with the control. These results showed that mechanical strain can improve MSCs proliferation and make MSCs differentiate to osteoblast.

Alkaline Phosphatase↗

PubMed2004

[The effect of mechanical stimulation on the proliferation and synthetic function of osteoblasts from osteoporotic rat].

The purpose of this paper is to investigate that the effect of cyclic biaxial mechanical strain on proliferation and synthetic function in the osteoblasts isolated from 3 month-old normal female Sprague-Dawley (SD) rats and osteoporotic rats. The osteoblasts were cultured in F-12 medium contained with 10% fetal bovine serum (FBC) and grown to subconfluency in Flexercell apparatus in a humidified incubator with 5% CO2 and 95% air at 37 degrees C. Mechanical strain was applied to the cells for periods of 30 min, 2, 4 and 8 hours every day,lasting 2 days. The amplitude of mechanical strain applied to the cells were 400, 1000 and 4000 microm strain respectively, at a frequency of one hertz (1 H). Unstrained cells were used as control. The results showed that proliferation activity of osteoblast in osteoporotic rats are higher than that in normal rats without mechanical strain the mechanical strain can elevate the proliferation activity and the synthetic function of osteoblast from normal rats at 400, 1000 microm strain. However, the mechanical strain increased significantly the proliferation in the osteoblasts and suppressed obviously the synthetic function in the osteoblasts at 4000 microm strain. The mechanical strain don't affect the proliferation activity and the synthetic function of osteoblast from osteoporotic rats at 400 microm strain. The mechanical strain decrease the proliferation activity of osteoblast from osteoporotic rats at 1000 microm strain. The mechanical strain can elevate the proliferation activity and the synthetic function of osteoblast from osteoporotic rats at 4000 microm strain. In our study, the reaction of the osteoblasts from normal rats and osteoporotic rats to the mechanical stimulation suggested that there are more highly sensitive to the mechanical stimulation in the osteoblasts from normal rats than that from osteoporotic rats.

Animals↗

PubMed2004

[Biomechanical study of medical hard tissue adhesive bonding butterfly fracture fragment in middle part of fresh human tibia].

A medical hard tissue adhesive, octyl-a-cyanoacrylate, was tested in 6 fresh human tibiae. A 90 degrees butter-fly fracture fragment was made in the middle part of tibia by bandsaw. The compressive stress, torsional stress and angular deflection were assessed before and after osteoectomy respectively. After adhesive bonding, the compressive stress, torsional stress and angular deflection were tested again. The butterfly fracture fagment decreased the bending strength, torsion strength, yielding strength of tibia bone. In torsion test, the torque of tibia before osteoectomy is greater than bonded tibia, the bonded tibia is greater than that of the unbonded tibia. In compression test, before adhesive bonding broken, the compressive curve slope of tibia before osteoectomy is greater than that of bonded tibia, the bonded tibia is greater than that of the unbonded tibia. In angular deflection test before adhesive bonding of broken,the curve slope of tibia before osteoectomy is not different from that of bonded tibia (P>0.05), the slope the bonded tibia is greater than the slope of unbonded tibia(P<0.05). The elastic modulus, rigidity coefficient and moment of area inertia show no statistical difference between the bonded tibia and intact tibia. The used of medical hard tissue adhesive to bond the fracture fragment could improve the bending strength, torsion strength, yielding strength of tibia bone. In operation, it can reduce the soft tissue injury when the fracture fragment is being fixed, and this will benefit bone healing.

Biomechanical Phenomena↗

PubMed2003

[The effect of mechanical stimulation on the expression of alpha 2, beta 1, beta 3 integrins and the proliferation, synthetic function in rat osteoblasts].

The purpose of this paper is to investigate the probable molecular mechanism in mechano-transduction of the regulation of integrins and the effects of cyclic biaxial mechanical strain on proliferation and synthetic function in the osteoblasts isolated from 3-month-old female Sprague-Dawley (SD) rats. The osteoblasts were cultured in F-12 medium contained with 10% fetal bovine serum(FBS) and grown to subconfluency in Flexercell type I dishes in a humidified incubator with 5% CO2 and 95% air at 37 degrees C. Mechanical strains were applied to the cells for periods of 30 min, 2, 4 and 8 hours every day, lasting 2 days. The amplitude of mechanical strain applied to the cells were 400, 1,000 and 4,000 mu strain respectively, at a frequency of one hertz(1 Hz). Unstrained cells were used as control. The expression of integrins alpha 2, beta 1, beta 3 on the membrane of osteoblasts and proliferation activity of osteoblasts were studied with Flow Cytometry(FCM). The content of osteocalcin, carboxyterminal propeptide of type-I procollage(PICP), total protein secreted by osteoblastes were detected with the isotope labelling method. The results showed that there are actual expressions of integrins alpha 2, beta 1, beta 3 on the membrane of osteoblasts without mechanical strain and that the expression of integrins beta 1 is highest. The mechanical strain increased the expression of integrins alpha 2, beta 1, beta 3 on the membrane of osteoblasts, but the strain-related up-regulation of expression of integrins alpha 2, beta 1, beta 3 are different in various amplitude and different duration of mechanical stains. The up-regulation of expression of integrins beta 3 is most sensitive to mechanical strain. The up-regulation of expression of integrins alpha 2, beta 1, beta 3 is higher at 4,000 mu strain than at 400, 1,000 mu strain. The mechanical strain can elevate the proliferation activity and the synthetic function of osteoblast at 400, 1,000 mu strain. However, the mechanical strain increased significant the proliferation in the osteoblasts and suppressed obviously the synthetic function in the osteoblasts. In the present study, the reaction of the osteoblasts in 3 month-old rat to the mechanical stimulation suggested that 1) expressions of integrins alpha 2, beta 1, beta 3 were increased in a amplitude of strain-dependent manner; 2) the changes of expression of integrins alpha 2, beta 1, beta 3 relate close to the changes of the proliferation and synthetic function of the osteoblasts. Low amplitude of strain can increase the proliferation and the synthetic function of the osteoblasts along with up-regulation of expression of integrins alpha 2, beta 1, beta 3; while higher amplitude of strain elevated significantly the proliferation of osteoblasts and suppressed obviously the synthetic function of the osteoblasts along with up-regulation of expression of integrins alpha 2, beta 1, beta 3. The amplitude of 4,000 mu strain is an optimal amplitude as stimulus for up-regulation of expression of integrins alpha 2, beta 1, beta 3 on the membrane of osteoblasts and increase the proliferation activity, but decrease the synthetic function of osteoblasts in the present study. Accordingly it indicates that integrins have a important role in regulation of signal transduction pathway in osteoblasts as a result of mechanical strain.

Animals↗

PubMed2003

[The effect of cryotreat on the wear resistance of the medium melting-point castable alloy].

OBJECTIVE: The purpose of this study was to introduce cryotreat technique into prosthetic dentistry by investigating the wear resistance changes of SDA-II medium melting-point castable alloy before and after cryotreat. METHODS: 15 samples were divided into three groups, i.e. control group, cryotreat group, cryotreated plus post-cryogenic treat group. Weight loss measurement was used to examine the wear resistance. RESULTS: For SDA-II medium melting-point castable alloy, cryotreat effectively improved its wearing resistance; so far as the wear resistance was concerned, the post-cryogenic treatment was unnecessary. CONCLUSION: The results obtained above suggest that cryotreat was an effective method in enhancing the wear resistance of SDA-II medium melting-point castable alloy.

Cold Temperature↗

PubMed2003

[Contraction peculiarity of the muscles that control the moving of the jaw of rat in different growing time].

OBJECTIVE: This study was aimed to evaluate the effect of functional change in oral cavity on the contraction peculiarity of the muscles that control the moving of the jaw in different time of growth. METHODS: Fifteen male Wistar rats 4, 6 and 8 weeks old were used in this experiment. After deep anesthesia, the masseter muscles(MM), digastric muscles(DM) and lateral pterygoid muscles(LPM) were stimulated in the apartment made by the present authors. The curves that express the relations of force with electric stimulation were recorded, and the relationships between the speed and force of twitch were analyzed. RESULTS: The maximal forces of twitch of the 8-week-old rats' MM, DM, LPM were 61.7 +/- 14.4 g, 86.4 +/- 25.1 g and 175.3 +/- 39.4 g respectively. When a single electric stimulus stimulated the muscles, the speed of twitch increased with the growth of the rats. As for MM and LPM, the speed markedly increased with the growing of rats from 4 weeks old to 6 weeks old; as for DM, it increased in rats growing from 6 weeks old to 8 weeks old. CONCLUSION: The quickest time of growth of the muscles that control the moving of the jaw of rat is a period from 6 weeks to 8 weeks old and the forces of contraction and twitch increase markedly.

Animals↗

PubMed2003

[A system applying cyclic biaxial mechanical strain to cultured cells].

To study the response of cultured cells to the cyclical biaxial biomechanical strain, a system was made according to the principle of Winston. The system was made of culture dish, pressure cavity and step motor. The culture dishes were made of polymethyl methacrylate and the bottom of the culture dishes were made of silicone rubber membrane. When the diameter of the silicone rubber tube and the distance between rollers and curvilinear plate changed, the pressure in the pressure cavity changed and the strain of the membrane changed from 0 to 4%. When the roll of the step motor changed, the frequency of the strain changed from 0.1 to 5 Hz.

Animals↗

PubMed2002

[Respondence to electricity in the muscles of rat's jaw].

15 male Wistar rats of 8 weeks old were used in this experment. After deeply anesthesia, the masseter muscles, digastric muscles, lateral pterygoid muscles were stimulated in the apartment that was made by us. The curves that express the relations of force-electronic stimulates were recorded and the constitutive equations of these muscles were given. When a single electronic signal stimulates the muscle, the respondence of the muscles can be expressed as F = A(e-alpha t - e-beta t) and the constant A, alpha, beta were determined. When the frequency of the electronic stimulation was higher than 3 Hz, the respondence was expressed as F = Ce-gamma/t + Dsin omega t and the constants C, D and gamma were determined. When the frequency of the electronic stimulation was thirty or higher, the tetanic convulsion occurred.

Animals↗