Relationship between the Height of Alveolar Bone Resorption and Sex and Age in Adolescents.

OBJECTIVES: To explore the relationship between the height of alveolar bone resorption and sex and age in the adolescent dentition. METHODS: Multi-slice computed tomography (MSCT) was used to measure the height of alveolar bone resorption at labial, lingual, mesial and distal sites of teeth in 149 adolescents aged from 10 to 20 years. SPSS 25.0 software was used to analyze the relationship between the height of alveolar bone resorption and sex and age. RESULTS: There was no significant difference in the height of alveolar bone resorption between sex (P>0.05). The height of alveolar bone resorption was positively correlated with age in all types of teeth. The model constructed by combining the alveolar bone resorption height data of four sites (y=2.569x1+3.106x2+4.108x3+1.451x4-0.082, R2max=0.756)had a better ability to infer age than that of combining two sites (y=5.942x1+4.489x2+0.612, R2max=0.706) and a single site (R2max=0.638). CONCLUSIONS: The height of alveolar bone resorption is positively correlated with the age of adolescents. The combination of four sites has a stronger ability to infer the relationship between the height of alveolar bone resorption and age in adolescents and has higher accuracy in practical application.

Torsional Fatigue Life Prediction of 30CrMnSiNi2A Based on Meso-Inhomogeneous Deformation.

In this paper, torsional fatigue failure of 30CrMnSiNi2A steel which exhibited non-Masing behavior was studied under different constant shear strain amplitudes, using thin-walled tubular specimens. The relationship between shear fatigue and the evolution of meso-deformation inhomogeneity and the prediction method of the torsional fatigue life curve were investigated. Shear fatigue of the material under constant amplitude was researched by numerical simulation with reference to tests, by using crystal plasticity of polycrystalline representative volume element (RVE) as the material model. Considering the non-Masing behavior of material, when determining the parameter values of the crystal plasticity model the correlation between these parameters and strain amplitude was taken into account. The meso-deformation inhomogeneity with increments in the number of cycles was characterized by using the statistical shear strain standard deviation of RVE as the basic parameter. Considering the effect of strain amplitude on fatigue damage, ratio cycle peak stress/yield stress was taken as the weight to measure the torsional fatigue damage and an improved fatigue indicator parameter (FIP) to measure the inhomogeneous deformation of the material was proposed. The torsional fatigue life curve of 30CrMnSiNi2A steel was predicted by the critical value of the FIP and then the result was confirmed.

Protective effects of gallium, germanium, and strontium against ovariectomized osteoporosis in rats.

The effects of trace elements of gallium (Ga), germanium (Ge), and strontium (Sr) on ovariectomized (OVX) osteopenic rats were studied in this paper. The urine calcium content, serum calcium, and phosphorus contents, bone mineral content, mineral dissolution, and mechanical strength of the osteopenic rats were analyzed respectively. After the rats were fed with Ga, Ge, and Sr diet for 8 weeks, respectively, the urine calcium content decreased (P < 0.01). Plasma calcium and phosphate concentrations decreased in the order of OVX group > Ge group > Sr group > Ga group > Sham group. Mineral content increased in the order of OVX group < Ge group < Sr group < Ga group < Sham group. A dramatic decrease in calcium solubility was found both in the gallium and strontium treated animals (P < 0.05). However, the same result did not occur in germanium treated groups. The data provide an important proof of concept that gallium and strontium might be a new potential therapy for the management of postmenopausal osteoporosis in humans.