Bone Density ; physiology ; Bone Development ; physiology ; Bone and Bones ; diagnostic imaging ; Child ; Humans ; Nutrition Assessment ; Ultrasonography

Androgen is an anabolic steroid composed of 19 carbon atoms. As a sex hormone, it has far-ranging effects on many sites within the body, including bone metabolism. Androgen has important effects on bone development and homeostasis. It has been proved that the androgen receptor (AR) expresses in bone cells, which indicates that androgen has direct effects on bone cells. Furthermore there is convincing evidence that aromatization to estrogen is an important way of mediating the action of testosterone. Androgen not only plays an important role in gaining the peak bone mass and maintaining the bone mass, but also has a close correlation with aging-related bone loss.
Androgens ; physiology ; Animals ; Bone Density ; physiology ; Bone and Bones ; physiology ; Female ; Humans ; Male ; Osteoblasts ; physiology ; Osteoclasts ; physiology ; Osteoporosis ; physiopathology ; Rats ; Receptors, Androgen ; physiology

OBJECTIVETo explore the effect of electroporation mediated gene therapy on bone mineral density and strength of new-formed bone in mandibular distraction gap, so as to enhance the osteogenesis and shorten the distraction term.

METHODSNew-Zealand rabbits were employed. The distraction began after 3 days of latency period at the rate of 0. 8 mm per day for 7 days. After distraction, the rabbits were randomly divided into 5 groups to receive injection in the distraction gap with recombinant plasmid 2 microg (0.1 microg/microl) pIRES-hVEGF165-hBMP2 in group A, with recombinant plasmid pIRES-hBMP2 in group B, with recombinant plasmid pIRES-hVEGF165 in group C, with pIRES in group D, and with normal saline (NS) in group E. After injection, electroporation was performed in all the groups. After 1 week, 2 weeks, 4 weeks and 8 weeks of consolidation, all the animals underwent X-ray and quantitative computed tomography (QCT). The new-formed bone in distraction gap was selected as regions of interest (ROI) to measure the bone mineral density(BMD). Then the rabbits were sacrificed and the new-formed bone samples were harvested to detect 3-point crushing strength.

RESULTSBMD of newly formed bone in group A, B and C was markedly higher than that in group D and E (P < 0.01). After 2 weeks of consolidation, BMD in group A was much higher than that in the other groups, but there was no difference between group B and C. After 4 weeks of consolidation, BMD in group A and B was markedly higher than that in group C, D and E (P < 0.01). After 8 weeks of consolidation, BMD in group A was markedly higher than that in the other groups. While the BMD was not significantly different between group B and C, but the BMD in group B and C was higher than that in group D and E (P < 0.01). After 4 weeks of consolidation, the 3-point crushing strength of newly formed bone in group A was markedly higher than that in group B,C, D and E (P < 0.01), which was still the same after 8 weeks of consolidation. And the crushing strength in group B was higher than that in group C, D and E (P < 0. 05).

CONCLUSIONSElectroporation-mediated transfection of recombinant plasmid pIRES-hVEGF165-hBMP2 could greatly enhance osteogenesis and calcification. A combination of VEGF and BMP may promote osteogenesis and angiogenesis simultaneously, so as to magnify the effect of each growth factor, resulting a synergetic effect.

Animals ; Bone Density ; Bone Regeneration ; Electroporation ; Genetic Therapy ; Mandible ; physiology ; surgery ; Osteogenesis, Distraction ; Rabbits

OBJECTIVETo comparatively investigate the inorganic composition and crystallographic properties of cortical and cancellous bone via thermal treatment under 700 °C.

METHODSThermogravimetric measurement, infrared spectrometer, X-ray diffraction, chemical analysis and X-ray photo-electron spectrometer were used to test the physical and chemical properties of cortical and cancellous bone at room temperature 250 °C, 450 °C, and 650 °C, respectively.

RESULTSThe process of heat treatment induced an extension in the a-lattice parameter and changes of the c-lattice parameter, and an increase in the crystallinity reflecting lattice rearrangement after release of lattice carbonate and possible lattice water. The mineral content in cortical and cancellous bone was 73.2wt% and 71.5wt%, respectively. For cortical bone, the weight loss was 6.7% at the temperature from 60 °C to 250 °C, 17.4% from 250 °C to 450 °C, and 2.7% from 450 °C to 700 °C. While the weight loss for the cancellous bone was 5.8%, 19.9%, and 2.8 % at each temperature range, the Ca/P ratio of cortical bone was 1.69 which is higher than the 1.67 of stoichiometric HA due to the B-type CO₃²⁻ substitution in apatite lattice. The Ca/P ratio of cancellous bone was lower than 1.67, suggesting the presence of more calcium deficient apatite.

CONCLUSIONThe collagen fibers of cortical bone were arrayed more orderly than those of cancellous bone, while their mineralized fibers ollkded similar. The minerals in both cortical and cancellous bone are composed of poorly crystallized nano-size apatite crystals with lattice carbonate and possible lattice water. The process of heat treatment induces a change of the lattice parameter, resulting in lattice rearrangement after the release of lattice carbonate and lattice water and causing an increase in crystal size and crystallinity. This finding is helpful for future biomaterial design, preparation and application.

Animals ; Bone Density ; physiology ; Bone and Bones ; chemistry ; ultrastructure ; Crystallography ; Spectrophotometry, Infrared ; Swine

OBJECTIVETo study the effects on rats' bone mineral density and bone biomechanics by suspensory simulated weightlessness and removing suspension.

METHODSTwenty Wistar rats were divided into two groups randomly as control group and model group. Suspend the model group rats for 14 days, then remove suspension and continue to feed for another 14 days. Feed control group rats for 28 days. Detect the bone mineral density (BMD) in vivo of cranial bone, second thoracic vertebra, fourth lumbar vertebra, pelvis, right radioulna and right femoral bone of each group at the 14th day. At the 28th day,execute all the rats and take out of right femoral bone and fourth lumbar vertebra for detecting BMD and the intensity of biomechanics.

RESULTSAt the 14th day in experiment, being compared with control group,the BMD of femoral bone, pelvis and lumbar vertebra in model group decreased significantly (P < 0.001, P < 0.001, P < 0.01) and the change of BMD of cranial bone, thoracic vertebra and radioulna in model group was not remarkable (P > 0.05). At the 28th day in experiment, the BMD of femoral bone and lumbar vertebra, the maximal load of femoral bone decreased significantly in model group as compared with control group (P < 0.01, P < 0.001, P < 0.01).

CONCLUSIONBMD in vive body showed that suspensory simulated weightlessness for 14 days could cause disorder of bone metabolism and remarkable mineral loss of weight bearing bone, even BMD and biomechanical intensity of weight bearing bone decrease obviously when removing suspension for 14 days. The results suggest that the disorder of bone metabolism could not be recovered in short time.

Animals ; Biomechanical Phenomena ; Bone Density ; Bone and Bones ; physiology ; Hindlimb Suspension ; Male ; Rats ; Rats, Wistar ; Weightlessness Simulation

A new method for the simulation of the mass distribution of cancellous bone is presented on the basis of finite element analysis (FEA). In this method,the process of bone remodelling is considered as a process of the topology optimization of a corresponding continuum structure. Fabric tensor is used to express the microstructure and the constitutive properties of cancellous bone. The effective volume fraction or the relative density of a point in the design domain is expressed by the invariables of the fabric tensor. A reference strain interval, which is corresponding to the strain dead zone of a bone in biomechanics, is applied to detect the the final topology of the structure. By the present approach, several numerical results are given, i. e., the simulation on the shape of the coronal plane of vertebrae, the predictions of the mass distributions of the two-dimensional and the three-dimensional proximal femurs. The validity and feasibility of this new method are verified by the comparison between the results of the present work and those in the published literatures.
Adaptation, Physiological ; Algorithms ; Biomechanical Phenomena ; Bone Density ; physiology ; Bone Remodeling ; physiology ; Bone and Bones ; physiology ; Computer Simulation ; Femur Head ; physiology ; Finite Element Analysis ; Humans ; Models, Biological ; Stress, Mechanical

OBJECTIVETo study the remodeling of the anterior alveolar bone with parodontium under physiology loading using finite element method (FEM) and theory of bone remodeling.

METHODSA FEM model of the maxillary central incisor with parodontium was established, and the change of bone density during the remodeling of alveolar bone was investigated under physiology loading (60 - 150 N) based on the theory of bone remodeling about strain energy density (SED). The finite element analysis software Abaqus user material subroutine (UMAT) were used.

RESULTSWith the increase of physiology loading, the pressure stress on the buccal cervical margin increased gradually while the density was decreased gradually. The cortical bone was lower than its initial density 1.74 g/cm(3), which was 1.74 - 1.63 g/cm(3). The density of cancellous bone was 0.90 - 0.77 g/cm(3), which was lower than its intial density 0.90 g/cm(3). The lingual cervical margin was under tensile stress which also increased with loading, the density had no significant change. When the achieve to 120 N, the density of cortical bone was 1.74 - 1.73 g/cm(3). No significant change was found in the cancellous bone.

CONCLUSIONSThe simulation of the perodontium remodeling is achieved and proved to be effective by the relevant research based on the method of the study. And the result will be helpful to form the basis of analysis bone remodeling process and predict the results in the clinical work.

Alveolar Process ; physiology ; Bone Density ; Bone Remodeling ; physiology ; Computer Simulation ; Dental Stress Analysis ; methods ; Finite Element Analysis ; Humans ; Incisor ; physiology ; Maxilla ; physiology ; Periodontium ; physiology ; Stress, Mechanical

Maximizing peak bone mass is advocated as a way to prevent osteoporosis. To evaluate the peak bone mass and the affecting factors in Korean women, we analyzed bone stiffness in 116 middle school students, 118 high school students and 115 female college students by using the Achilles densitometer (Lunar Corporation). Peak bone stiffness of Korean women was relatively lower than that of white women (94% of white women) and a rapid rise of bone stiffness was observed in those subjects 3-4 years after menarche. In adolescent females without menstruation, the bone stiffness was lower than that of adolescent girls with menstruation. The factors affecting the peak bone mass was similar to the risk factors of post menopausal osteoporosis: menstruation status, calcium intake and physical activity. The amount of calcium intake in Korean girls at the critical age (3-4 years after menarche) was lower than the RDA (requirement of daily allowance) at this age. To improve any program aimed at maximizing peak bone mass, further intensive study will be required to evaluate some other common factors affecting peak bone mass in Korean.
Adolescent ; Adult ; Aging/physiology ; *Bone Density ; Bone and Bones/drug effects/physiology ; Calcium, Dietary/pharmacology ; Child ; Elasticity ; Female ; Human ; Korea ; Menarche

OBJECTIVETo evaluate the quality of the alveolar ridge augmented by Ti-Ni shape memory alloy (Ti-Ni SMA) distractor.

METHODSAll of the mandibular premolars and the first molars were extracted from 12 adult mongrel canines. One month later, box-shaped osteotomy was carried out in the left mandibles and Ti-Ni SMA distractors were imbedded. The right sides served as blank control. The canines were killed 3 or 6 months later and specimens were taken from corresponding area of the experiment sides and the control. Bone mineral density and biomechanical function were measured.

RESULTSBone mineral density, ultimate compressive strength and Young's Modules of the augmented ridge were lower than the blank control three months after distraction. But the indexes increased and showed no significant difference with the control six months after distraction.

CONCLUSIONSThe canines mandibular posterior alveolar ridge could be augmented by distraction osteogenesis using Ti-Ni SMA distractor, and the new bone is strong enough for implant placement.

Alveolar Ridge Augmentation ; methods ; Animals ; Bone Density ; Bone Regeneration ; physiology ; Compressive Strength ; Dogs ; Male ; Mandible ; physiology ; Nickel ; Osteogenesis, Distraction ; Titanium

PURPOSE: The purpose of this study was to retrospectively describe the childhood sports activity level of Korean adult men and women and to determine whether a higher level of childhood sports activity was positively associated with adult bone mineral density. METHODS: A cross-sectional study of 100 Korean men (n=40) and women (n=60) was completed. Participants completed a detailed lifetime sports activity questionnaire and had their bone mineral density of the femur and lumbar spine measured using dual energy x-ray densitometry (DEXA). All sports activities were classified into four categories of peak strain score on the basis of ground reaction forces (GRF). RESULTS: During the age of high school, women and men who participated in a high intensity sports activity demonstrated higher bone density in the femur site after adjustment for the effects of body weight, fat body mass, lean body mass, the level of calcium intake, and breast feeding period than those who did not participate in sports activity at all. CONCLUSION: These results highlight the need to participate in high intensity sports activity during high school age as a means of increasing peak bone mass in the femur site.
Sports/*physiology ; Male ; Korea ; Humans ; Female ; Densitometry, X-Ray ; *Bone Density ; Body Constitution ; Body Composition ; Adult