Flow properties of thermoplasticized Gutta Percha obturation materials / 대한치과재료학회지

The purpose of this study is to evaluate the flow ability of the thermoplasticized Gutta Percha in different temperatures. Four Gutta Percha products were classified by its hardness (soft, medium, and hard) and were experimented by the Rheometer (Melt flow indexer MFI-10, DAVENPORT, England) measuring apparatus, in (23 ± 2) ℃, and in a relative humidity of (50 ± 5) %, following the guidelines of ISO 1133-1:2011. The heating temperature ranged from 108℃, 160℃ to 200℃, and the load at 2.16 kg and 3.8 kg. The Gutta Percha was cut in 5 mm to be suitable for the rheometer pressurization process. After the experiment was conducted with a preheating time of 5 minutes, a cutting time of 5–240 seconds, and a sample of 10 grams, the Gutta Percha did not show any changes in fluidity for 108℃, 160℃, but showed a change in its flow ability in 200℃. Also, the Gutta Percha did not show any changes in its fluidity when it was pressurized by 2.16 and 3.8 kilograms. Therefore, this experiment shows that the heating temperature and the cut-off time showed a significance while measuring the melt flow rate.

Comparison of the Chemical Composition of Subchondral Trabecular Bone of Medial Femoral Condyle between with Advanced Osteoarthritis and without Osteoarthritis

BACKGROUND: The purpose of this study is to investigate differences of chemical composition between subchondral bone in advanced osteoarthritic (OA) and non-OA distal femur. METHODS: Twenty femurs were harvested, respectively. The subchondral trabeculae were obtained from the middle of medial articular surface of distal femurs. A 10 mm diameter cylindrical saw was used to harvest. Raman spectroscopy, a non-destructive technique, was employed to determine the chemical information of the trabecular bones in the human distal femurs. RESULTS: The maximum intensity of the phosphate peak was 2,376.51+/-954.6 for the non-OA group and 1,936.3+/-831.75 for the OA group. The maximum intensity of the phosphate peak observed between the two groups was significantly different (P=0.017). The maximum intensity of the amide I peak were 474.17+/-253.42 for the nonOA group and 261.91+/-205.61 for the OA group. The maximum intensity of the amide I peak were significantly different between the two groups (P=0.042). Also, among other chemical and matrix components (Hydroxyproline,Carbonate, Amide IIIdisordered;ordered, and CH2), the spectrums showed similar significant differences in the intensity (P=0.027, P=0.014, P=0.012; P=0.038, P=0.029). Area integration were performed to determine disorder in collagen's secondary structure via amide III (alpha helix/random coil). The value of the alpha helix to random coil band area are significantly different (P=0.021) and result showing that there was a trend toward higher collagen maturity for the nonosteoarthritic bone specimens. CONCLUSIONS: The result suggested that OA may affect the chemical compositions of trabecular bone, and such distinctive chemical information may be.

Changes in the Microstructural and Mechanical Properties in the Medial Condyle of Human Distal Femur in Advanced Osteoarthritis / 대한골다공증학회지

OBJECTIVES: The purpose of this study is to analyze and compare the micro-structural and mechanical properties of subchondral trabecular bone of non-osteoarthritic and osteoarthritic distal femur using micro-images based on finite element analysis. MATERIALS AND METHODS: Twenty distal femurs were harvested from 10 cadavers. The subchondral trabeculae were obtained from the middle of the articular surface of the medial femoral condyle of distal femurs. A total of 20 specimens were scanned using the micro-CT system. Micro-CT images were converted to micro-finite element model using the mesh technique, and micro-finite element analysis was then performed for assessment of the mechanical properties. RESULTS: According to the results, trabecular bone of osteoarthritic distal femur showed a decrease in trabecular thickness, bone volume fraction, structure model index, and yield stress and an increase in trabecular separation and structure model index. CONCLUSIONS: Results of bone morphometry index and strength showed greater deterioration of microstructure and decreased mechanical strength in subchondral trabeculae of the osteoarthritic group.

Analysis of Trabecular Bone Strength using Finite Element Analysis / 대한골다공증학회지

OBJECTIVES: The purpose of this study is to develop a method of evaluation based on finite element analysis (FEA) using micro-CT images for the measurement of trabecular bone strength. METHODS: The primary compressive trabeculae were obtained from the human femoral head of three cadavers (21 year old male (M/21), 51 year old male (M/51), 51 year old female (F/51). All bone specimens were scanned using micro-CT at 24.9microm of spatial resolution under 70 kV's voltage and current of 141microA. The percent bone volume was calculated from the CTAn (SKYSCAN, Belgium) software, it's represented the bone mineral density (BMD). After scanning, the finite element model was reconstructed based on micro-CT images. All models were applied to be linear elastic, isotropic, and uniform with a tissue modulus of 5.17 GPa and a tissue Poisson's ratio of 0.3. RESULTS: The percent bone volume(%) were 31.819 (+/-0.648), 21.513 (+/-2.489), 20.280 (+/-1.891) and Bone strength (MPa) were 187.741 (+/-13.006), 61.585 (+/-11.094), 61.266 (+/-16.744) in M/20, M/51 and F/51. The trabecular bone strength of the primary compressive trabeculae in M/20 was 3 times more than the trabecular bone strength in M/51 and F/51. The percent bone volume in M/20 was 148% and 157% higher than the percent bone volume in M/51 and F/51. CONCLUSIONS: The finite element analysis is more sensitive than the percent bone volume in reflecting the morphometry index of primary compressive trabeculae. The high resolution FEA reconstructed from high resolution MRI or high resolution CT may improve the evaluation of trabecular bone strength in the medical field.

Bone Strength of the Primary Compression Trabeculae in Human Calcaneus / 대한골다공증학회지

OBJECTIVES: The accuracy of bone strength can be improved for medically treating osteoporosis by diagnosing and predicting fracture risk. In this study, we calculated the material properties of calcaneus bone and evaluated the statistical correlation of the bone mineral density (BMD) with morphometry indices and bone strength. MATERIALS & METHODS: Twelve cored bone samples were obtained from the primary compressive trabeculae of human calcaneus. All samples were scanned with a Lunar PIXImus(R), and two-dimensional serial section images were obtained on a micro-computed tomography system. A mechanical test was performed with an Instron universal testing machine and finite element analysis (FEA) to determine material properties and bone strength. RESULTS: The material property of the samples was 2.97 GPA. BMD was significantly correlated with bone strength and morphometric indices except for Tb.Sp, DA, and Tb.N. The statistical relationship between bone strength and the morphometric indices was significant except for DA. CONCLUSIONS: FEA based on in vivo high resolution serial section images can be used to directly evaluate bone strength and will be a useful tool in clinical practice for diagnosing osteoporosis and predicting fracture risk.

Effects of the Amount of Proximal Tibia Resection on the Bone Strength of Prepared Bone Surface: A FEM Study / 대한정형외과학회잡지

PURPOSE: We wanted to evaluate the mechanical strength of proximal tibia as resection distance increased from the joint surface. MATERIALS AND METHODS: We obtained the CT images of twenty knee osteoarthritis patients undergoing total knee arthroplasty. The finite element models were created based on the computed tomography images. The 8-node hexahedron element was made from BIONIX(TM) (CANTIBio. Co, Suwon, Korea), which is automatic mesh generation software program. The finite element model of the proximal tibia was resected at 6 mm, 8 mm, 10 mm, 12 mm, 15 mm and 18 mm from the lateral joint surface. A 1% strain rate was applied to a model by using HyperMesh(TM) software (Altair Engineering. Inc, Seattle, USA). The ultimate stress was calculated from the finite element analysis with using ANSYS 9.0 (ANSYS. Inc, Orlando, USA). RESULTS: The mean ultimate stress was 906.84 MPa, 877.22 MPa, 895.93 Mpa, 852.70 MPa, 742.90 Mpa and 585.51 Mpa at the 6 mm, 8 mm, 10 mm, 12 mm, 15 mm and 18 mm resection levels. As compare to the 6 mm resection level, the bone strengths at 15 mm and 18 mm were decreased with statistical significance (15 mm: p=0.005, 18 mm: p=0.000). CONCLUSION: The ultimate stress was decreased as the resection distance increased from the joint surface. But within a 12 mm resection distance from the lateral condyle articular surface of the tibia, the ultimate stress was not significantly decreased (p>0.05).

Effect of Sequential Therapy with Incadronate after Withdrawal of Recombinant Human Parathyroid Hormone(1-84) on Bone Quantity and Quality in Ovariectomized Rats / 대한내분비학회지

BACKGROUND: Human parathyroid hormone(hPTH) is a promising anabolic agent. However, since hPTH (1-34) is available only via injection, and has a critical side effect of causing bone tumors during life-long administration in the rat, it would be practical to use PTH for the shortest possible duration to obtain the maximal effect. In addition, acquired bone mass due to hPTH tend to decrease after drug cessation. To determine the effectiveness of the osteoporosis-reversing concept of lose, restore, and maintain(LRM), recombinant human PTH(1-84)[rhPTH(1-84)] and the respective anti-resorptive agents were sequentially studied. METHODS: Thirty six, 20-week-old, Sprague-Dawley rats were used in this study. Treatment was started on the 25th week after an ovariectomy, which had been performed at 20weeks of age, with 5weeks of rhPTH (1-84) 100(microgram/kg/d), 5days/wk, followed by the respective sequential therapies for 5 weeks as follows: 1) Ovariectomized rats(OVX, n=6), 2) Sham operated rats(SHAM, n=6), 3) OVX rats with PTH maintenance(PTH-M, n=6), 4) OVX rats treated with PTH then withdrawn(PTH-W, n=6), 5) PTH-treated OVX rats then treated with 17beta-estradiol(PTH-E, 10microgram/d, SQ, 5days/wk, n=6), 6) PTH-treated OVX rats then treated with incadronate(PTH-I, 3mg/kg, per os 5 days/wk, n=6). The bone mineral density(BMD) of the right femurs was measured using dual X-ray absorptiometry(DXA). Microcomputed tomography(microCT) was used to measure the structural parameters of the 2nd lumbar vertebrae. A three-point bending test of the femur and compressive tests of vertebrae were also performed. RESULTS: Bone quantity data showed that the femoral BMD was significantly higher in the PTH-M and PTH-I groups than in the OVX and PTH-W groups(P<0.05). Measurement of the cortical thickness revealed that only the PTH-M group had a significant increase(P=0.001). The ultimate force(Fu) at the midshaft of the femur was stronger in the PTH-M group than in the OVX group(P<0.001). However, no significant difference was found among the treated groups. CONCLUSION: PTH withdrawal resulted in the loss of the acquired BMD, but sequential therapy with the anti-resorptive, incadronate, prevented further bone loss. The use of incadronate after rhPTH(1-84), as a sequential regimen, was significantly effective on the maintenance in the bone mass, but further clarification in the improvement in the bone quality is needed.

Micro-Structural Profiles of Trabecular Bone at the Ankle Joint / 대한족부족관절학회지

PURPOSE: This study aimed to investigate and compare the micro-structural profiles of trabecular bone from different facets at the ankle joint. MATERIALS AND METHODS: In a fresh cadaver ankle, four cored 10 mm of diameter cylindrical specimens of trabecular bone were harvested from the distal tibia, the talar dome, the medial malleolus, and the lateral malleolus. Using a micro-computed tomography, two-dimensional and three-dimensional micro-structural indices of the trabecular bone were analyzed. RESULTS: Each specimen from the tibia, talus, medial malleolus, and the lateral malleolus showed unique micro-structural pattern. Tibia versus talus, the talus was seen a higher bone volume fraction and a wider supporting zone subchondrally whereas the tibia was seen a relatively lower bone volume fraction and a much narrower supporting zone subchondrally. Lateral malleolus versus medial malleolus, the lateral malleolus was seen the thicker but sparse trabeculae pattern whereas the medial malleolus was seen the thinner but more compact trabecular pattern. CONCLUSION: Each four locations from the different facet at the ankle joint have distinct own micro-structural patterns of the trabecular bone, suggesting different mechanical properties.