ABSTRACT
Objective:To investigate the stress distribution in peri-implant bone with All-on-4 implant with various parameters by three-dimensional finite element method.Methods:An edentulous mandibular specimen was scanned by CT Mimcs.Geomagic,Uni-graphics,HyperMesh modeling software were used to establish All-on-4 implant finite element models with different inclination angles and corresponding cantilever lengths.1 50 N vertical static load was applied at the right end of the cantilever,peri-implant bone stress was analysed using Abaqus software.Results:When the distal implant inclined 0°with cantilever length of 1 9.5 mm,the peak stress in peri-implant cortical bone at the mesial and distal side was 25.526 MPa and 83.026 MPa respectively.When the distal implant in-clined 1 5°,30°and 45°with the cantilever length of 1 7.2 mm,1 3.3 mm and 9.8 mm,the stress in perio-implant cortical bone at distal side of the implant reduced by 1 2.4%,35.6% and 53.1 %,that at mesial side of the implant reduced by 1 3.6%,36.3% and 40.2%,respectively.Conclusion:From the perspective of the stress analysis,the design of All-on-4 distal implant with large incli-nation angle and short cantilever is superior to that with small inclination angle and long cantilever.
ABSTRACT
Objective To investigate the effects of internal plating with high and low moduli of elasticity on the stress and its distribution on the femoral shaft fracture. Methods A femur from a normal Chinese adult male was scanned by 64-detector row helical CT at 0. 5 mm interval. The CT images were used to establish a finite element model of the femur by software. The mid-femoral fracture was simulated in the model and fixated by eight-hole plates of Ti-6Al-4V (high modulus group, E = 110 GPa) and of Ti2448 (low modulus group, E = 30 GPa). When the femur was in axial compression, flexion and torsion loads, the stress and its distribution on the bone fracture site were analyzed to compare the biomechanics of the plates with high and low moduli. Results Under axial compression load, the contact stress between fracture ends in the low modulus group was larger than that in the high modulus group, while the max stress at the hole (11.47MPa) was smaller than that in the high modulus group (13.89 MPa) . Under four-point bending load, the contact stress in the low modulus group was still larger, while the bending movement was smaller. Under the torsion load, stress on the femur was well-distributed in both groups, but the max stress at the hole in the low modulus group (11.47 MPa) was smaller than that in the high modulus group (31.24 MPa). Conclusions Under internal fixation by plates of low modulus, the stress stimulus at the fracture site may be increased,while the stress concentrated at the hole may be decreased. The stress shielding of the low modulus plate may also be modified.
ABSTRACT
Based on the body height and weight of the Chinese young men, 975 from the north and 921 from the south of China, actually measured, a calculating formula for the ideal body weight of young men both of north and south listed blow was established. The Northener's ideal body weight (kg) = [height (cm) - 150] ? 0.6 +50; the Southener's ideal body weight(kg) = [height (cm.) - 150] ? 0.6 +48. The formula later checked by another data of body height and weight of 783 young men from north and 883 from south has been proved to be reliable. It also showed that the ideal body weight of 1464 young men from north and 2264 from south calculated according to the formula seemed to be more reasonable than the another's formula used previously.
ABSTRACT
35 rats were divided into 5 groups. Group 1-3 were fed rations containing 20, 12 and 6% caseien respectively, group 4 containing 12% mixed protein of soybean and gluten. The food of group 5 was the same as that of group 1 but the amount was only half of that of group 1. Every animal was given 8?g vitamin A by stomach tube daily for 3 weeks and then 25?g for 2 weeks. Afterward serum vitamin A values were determined in all animals, then 132?g vitamin A was administrated by stomach tube. After 3.5 hours, the vitamin A values in serum and liver were determind. The results showed that in group 3 and 5 serum vitamin A contents decreased and the liver values rose. It was suggested that the release of vitamin A from liver had been interfered by semistarvation or low protein intake. There is no difference between group 2 and 4.
ABSTRACT
An improved microfluorimetric method for determination of serum vitamin A was presented. In this method, the excitation wavelength 345nm and emission maximum 480nm were selected, and cyclohexane as solvent for extraction of saponified vitamin A in the serum samples to be tested was used. The sensitivity was sufficient for measurement of vitamin A content in 20*l serum taken from normal fasting blood without elimination of interference. The recovery averaged 99.0% (93.0-105.5).When this method was applied to laboratory study or field work, practically, the results showed that the values of vitamin A obtained seemed to correlate with its nutritional status of experimental animals or subjects investigated. The procedure was simple, reproducible and easily acceptable, espicially in the field work.
ABSTRACT
Ninety rats were divided into 8 groups. Group 1-5 were fed vitamin A free ration and each group was divided into 2 subgroups at the beginning and 12, 23, 36, 43, days after the experiment respectively. Group 6-8 were fed the ration containing 66, 132, and 198?g vitamin A per 100g diet respectively fer 30 days, and each group was also divided into 2 subgroups. The results showed that RBPR% was better than the serum vitamin A content in evaluating vitamin A nutritional status. It was suggested that the vitamin A nutritional status could be graded as follows: deficient(abore 70%)) mar-ginal(60-70%),normal (20-60%), and sufficient (under 20%)by RBPR%.
ABSTRACT
The ascorbic acid in plasma was determined on the basis of reduction of ferric to ferrous ion and its formation of a colored complex with batho-phenanthroline. This method was highly correlated to Roe's dinitrophe-nylhydrazine method in the determination of plasma ascorbic acid of 16 normal adults and the correlation coefficient was 0.90. By animal experiment the new method may be used to discriminate different levels of plasma ascorbic acid. It is rather simple and water bath is not required. Only 0.25ml of plasma is needed for each determination. So this method is useful in assessing the ascorbic acid nutriture in tield survey.
