ABSTRACT
Objective To design a novel device with dynamic occlusal loads so as to investigate the influence of occlusal force on Ni release from Ni-Cr PFM alloys. Methods Based on the average force(45 N) and rate(80 cycles/min) of human mastication, a novel device with dynamic occlusal loads was designed to study the Ni release from three commonly used Ni-Cr PFM alloys (Shangchi, Stellite, BEGO) in the artificial saliva with pH 2.3 and pH 7.4, respectively. Results This novel device with dynamic occlusal loads worked well to simulate the average force and chewing cyclye. In the artificial saliva with pH 2.3, the amount of Ni release in Shangchi, Stellite and BEGO was 6.9(2.07) μg/cm2, 3.7(0.662) μg/cm2 and 5.88(1.57) μg/cm2, respectively; while in the artificial saliva with pH 7.0, the amount of Ni release in Shangchi, Stellite and BEGO was 0.272(0.059) μg/cm2, 0.144(0.014) μg/cm2 and 0.435(0.053) μg/cm2, respectively. For the same Ni-Cr PMF alloys, the amount of Ni release in the artificial saliva with pH 2.3 was much higher than that with pH 7.0 (P<0.01), showing statistical differences. Conclusions The device with dynamic occlusal loads could be used effectively to evaluate the influence of occlusal force on Ni release from Ni-Cr PFM alloys in vitro. The acid environment could obviously accelerate the Ni release from Ni-Cr PFM alloys. This study showed the amount of Ni release in Stellite was relatively lower than that in the other two alloys.
ABSTRACT
Objective To design and build a new dynamic load and circulating perfusion bioreactor system and test its performance. Methods The design principle of the bioreactor system was specified and the dynamic strain loading system and 3D perfusion culture system were designed and built accordingly. A special culture chamber for 3D perfusion and compressive loading was also developed. The sterility of the culture chamber and the accuracy and stability of the strain loading were measured, and the result from the culture of tissue engineering bone was preliminarily observed. Results This bioreactor system could provide compressive strains with different magnitudes and frequencies, as well as perfusions under different flow conditions. It could be controlled accurately and operated easily with a steady performance. No germs were grown in the culture medium after 5 days’ running. The preliminary results showed that after the tissue engineering bones were cultured in the bioreactor for 10 days, cell proliferation and ALP activity in this perfusion culture and loading group were significantly higher than those in the static culture group and the simple perfusion culture group. Conclusions The bioreactor could be an ideal dynamic culture and loading device for biomechanical study of tissue engineering bone.
ABSTRACT
Objective To carry out quantitative investigation on application of emulational trunk dummy (ETD) in evaluating the opening shock of life saving parachute and provide a more reliable test method for further development. Method ETD equipped with parachute was tested in the impact experiment, where a 63.4 kg impact block was dropped from the height of 0.20 m，0.40 m，0.60 m，0.80 m respectively to simulate different opening shocks. The opening shocks were deducted by measured forces on harness and acceleration loads at the center of dummy's thorax. For comparison, 5 rigid trunk dummies (RTD) were tested under the equivalent impacts. As the contrast test, 24 male healthy subjects were also exposed under such impacts with standing and sitting posture respectively. Results Under the same impact, the peak impact value on harness exhibited maximum on RTD, minimum on subjects with sitting posture, and medium on ETD. There were significant differences between each experimental group (P<0.01). With different impact loads, the peak impact value on ETD was 2 795，3 873，4 816 and 5 736 N respectively, which was correspondingly close to that of subjects with standing posture(2 541，3 042，3 720 and 4250 N). Conclusions The result of opening shock gathered from ETD is closer to that from RTD due to ETD’s viscoelasticity, which shall certainly influence the measured opening shock. Therefore, ETD is suggested to be used in the development of live saving parachute.