Time-course changes of intraosseous environment and shear resistance mechanical properties of jawbone in SD rats with fluorosis / 环境与职业医学

Background At present, a large number of reports focus on the bones of limbs and trunk, while there are few studies on the effect of fluorosis on jawbone which is the inevitable structural basis for the development and treatment of oral diseases. Objective To preliminarily investigate the effect of fluoride exposure on the mechanical properties of jawbone by observing the changes in the intraosseous environment and the maximum load against shearing force (LSFmax) of the jawbone in rats with chronic fluoride treatment. Methods Screening experiment: 48 SD male rats were randomly divided into a control group and three fluoride exposure groups (50, 150, and 250 mg·L−1 fluoride concentration), 12 rats in each group. The fluoride exposure groups were molded by feeding different concentrations of sodium fluoride solution, and the control group drank tap water from Guizhou area. Each group was further divided into 4 subgroups with 3 animals each according to observation time points after 0, 2, 4, and 6 months. The LSFmax of the jawbone was measured with an electronic universal ergometer, the expression of type I collagen (Col1) was shown by Sirius red staining, and the expression of runt-related transcription factor 2 (Runx2) was determined semi-quantitatively by immunohistochemistry at selected time points. Formal experiment: 12 male SD rats were randomly divided into a fluoride exposure group and a control group. The fluoride exposure group were fed with 150 mg·L−1 sodium fluoride solution, and the control group drank tap water from Guizhou. After feeding with fluoride for 5 months, the ergometer was used to measure the LSFmax of the jawbone. Osteoclasts were counted after tartrate resistant acid phosphatase (TRAP) staining. Col1, Runx2, bone morphogenetic protein 2 (BMP-2), alkaline phosphatase (ALP), and cathepsin K (Cath K) were detected semi-quantitatively by immunohistochemistry expression and Sirius red staining. Micro computed tomography (Micro CT) was used to observe the trabecular bone microstructure. Results Screening experiment: The LSFmax of the control group and the 50 mg·L−1 fluoride exposure group reached the peak value at the 2nd month, and the LSFmax of the 50 mg·L−1 fluoride exposure group reached the valley value at the 4th month. The LSFmax of the 150 mg·L−1 fluoride exposure group at the 4th month was higher than that at the 6th month (P<0.05). There was no significant difference in the LSFmax at each time point in the 250 mg·L−1 fluoride exposure group. At the same time point, there was no statistically significant difference in LSFmax among the groups. The Col1 levels of the 50 mg·L−1, 150 mg·L−1, and 250 mg·L−1 fluoride exposure groups were higher than the time point 0 from the 2nd month (P＜0.05). The Runx2 showed no statistically significant difference by concentration or time. Formal experiment: After feeding with 150 mg·L−1 fluoride for 5 months, the LSFmax of the fluoride exposure group was greater than that of the control group (P<0.05). The expressions of Col1, Runx2, BMP2, ALP, and Cath K in the fluorosis exposure group were higher than those in the control group (P<0.05). There were no statistically significant differences in osteoclast count or indicators of bone trabecular microstructure. Conclusion Chronic fluoride exposure may increase the shear strength of jaw bone.

The preliminary study on biomechanical properties of four synthetic implants for reconstructive surgery of pelvic floor dysfunction / 生物医学工程学杂志

This study aimed to investigate biomechanical properties of synthetic implants for reconstructive surgery of pelvic floor dysfunction. In this dissertation, we chose four synthetic implants, i.e. total pelvic floor repair system (PROLIFT), gynecone TVT obtutator system (TVT-O), intra-vaginal sling placement device (IVS) and acellular dermal matrix (Renov), for tensile test respectively. The biomechanical properties of four synthetic implants were measured and analyzed using a material testing machine (Instron 4302 versatile material testing machine). The biomechanical parameters included ultimate stress strength, modulus of elasticity, maximum load and maximum elongation. The results showed that the maximum load of the four symthetic implants was TVT-O > IVS > PROLIFT > Renov, and the maximum load of TVT-O was significantly higher than PROLIFT and Renov ( < 0.05). The ultimate stress strength was TVT-O > IVS > PROLIFT > Renov, with no significant differences among them ( > 0.05). The maximum elongation of the four implants was TVT-O > PROLIFT > IVS > Renov, and the maximum elongation of TVT-O and PROLIFT were both significantly higher than Renov ( < 0.05). The modulus of elasticity was IVS > Renov > TVT-O > PROLIFT, with no significant differences among them ( > 0.05). Taken together, the present study demonstrates that the modulus of elasticity of IVS was the highest in the four synthetic implants; TVT-O had the highest mechanical strength; The maximum load, ultimate stress strength and maximum elongation of Renov were all the lowest; The mechanical properties of PROLIFT was the most stable, and its modulus of elasticity was the lowest in the four synthetic implants, which had good extensibility and elasticity. Therefore, it is necessary to pay attention to the biomechanical properties of new pelvic reconstructive materials for the clinical pelvic reconstructive surgery.

The effects of ovariectomy and naproxen treatment on the strength of femoral midshaft and molar alveolar region in rats / Efectos de la ovariectomía y tratamiento con naproxeno sobre la resistencia de la parte media de la diáfisis femoral y la región alveolar molar en ratas

The goal of the present study was to investigate the effects of ovariectomy and naproxen treatment on both femoral and mandibular bone mass and biomechanical competence. Sprague-Dawley rats were used and divided into five groups: baseline, sham ovariectomized, ovariectomized, sham ovariectomized + naproxen treatment, ovariectomized + naproxen treatment. Mandibles and femurs of the rats were extracted and bone mineral density of the extracted specimens were determined. The volumes and ash weights of the femurs and mandibles were estimated. Maximum loads of the femurs and mandibles were determined by using a three point bending test. Ovariectomy decreased bone mineral density of the femoral midshaft, however naproxen prevented this decrease. Neither ovariectomy nor naproxen treatment affected the BMD in the molar alveolar region. Maximum load was found significantly decreased in the femoral midshaft, however, naproxen treatment prevented this decrease. Maximum load of the molar alveolar region did not significantly change. Naproxen prevents the strength characteristics of femoral midshaft afforded by ovariectomy. However, neither ovariectomy nor naproxen has an effect on the molar alveolar region of the mandible.

El objetivo del presente estudio fue investigar los efectos de la ovariectomía y el tratamiento con naproxeno sobre la masa y la competencia biomecánica del fémur y hueso mandibular. Fueron utilizadas ratas Sprague-Dawley, la que se dividieron en cinco grupos: referencia, ovariectomizadas simuladas, ovariectomizadas, ovariectomizadas simuladas + tratamiento naproxeno, ovariectomizadas + tratamiento naproxeno. Las mandíbulas y los fémures de las ratas fueron extraídos y se determinó la densidad mineral ósea (DMO) de las muestras extraídas. Los volúmenes y pesos de la ceniza fueron estimados. Las cargas máximas de las mandíbulas y fémures se determinaron utilizando un ensayo de flexión de tres puntos. La ovariectomía disminuyó la densidad mineral ósea de la diáfisis media del fémur; sin embargo, el naproxeno impidió esta disminución. Ninguna ovariectomía sin tratamiento de naproxeno afectó a la DMO en la región alveolar molar. La carga máxima se encontró significativamente disminuida en las diáfisis femoral media, pero por el tratamiento de naproxeno no se produjo esta disminución. La carga máxima de la región alveolar molar no cambió en ninguna condición. El naproxeno previene los cambios de resistencia causados por la ovariectomía de la diáfisis media del fémur. Sin embargo, ni la ovariectomía ni el naproxeno tienen un efecto en la región alveolar molar de la mandíbula.

Bond strength of fiber reinforced composite after repair / 대한치과교정학회지

Fiber reinforced composite (FRC) is usually used as a connector joining a few teeth into one unit in orthodontics. However, fracture often occurs during the two to three years of the orthodontic treatment period due to repeated occlusal loading or water sorption in the oral environment. We simulated the repair by overlapping and attaching portions of two FRC strips in the middle and performed a three-point bending test to investigate the changes of the repair strength among the different FRC groups. The specimens were grouped according to the overlapping lengths of the two FRC strips, which were 1, 2, 3 and 4 mm (group E1, E2, E3 and E4, respectively) and the control group consisted of unrepaired, intact FRC strips. Each group consisted of 6 specimens and were cured with a light emitting diode curing unit. Group E4 showed the highest maximum loads of 2.67 N, then the control group (2.39 N), group E3 (2.35 N), E2 (2.10 N), and E1 (1.75 N) in decreasing order. Group E4 also showed the highest stiffness, which was 2.32 N/mm, however, the stiffness of group E3 (2.06 N/mm) was higher than that of the control group (1.88 N/mm). According to the visual examination, the specimens tended to be bent rather than being fractured into two pieces with an increased length of overlapping portions. The above results suggest that a minimum overlapping length of 3 mm was necessary to obtain an adequate repair of a 10 mm length of FRC connector. In addition, the critical section adjacent to the joint area, where the thickness decreased abruptly, should be reinforced with flowable resin to minimize the bending tendency.

The Effect of Isoflavone on Bone Mineral Density and Maximum Load in Stroke Rat

OBJECTIVE: Because bone metabolic changes progress from initial stage of stoke, early prevention and treatment have been important. Isoflavone has been proved to be effective in post-menopausal osteoporosis. Therefore the authors used a stroke rat model and evaluated the effects of isoflavone on bone metabolism from initial stage of stroke. METHOD: Female Sprague-Dawley rats were randomly divided into 2 separate groups; a stroke without isoflavone supplement group and stroke with isoflavone supplement group. The bone mineral density (BMD) in 4th and 5th lumbar vertebrae were measured at the day before stroke, 11th and 18th days after the stroke. The BMD in excised distal femur and proximal tibia and the maximum load of emur neck and tibia shaft were measured at 18th days after the stroke. RESULTS: On the 18th day after stroke, BMD of stroke with isoflavone group was significantly higher than that of stroke without isoflavone group in 4th and 5th lumbar vertebrae and distal femur. The maximum load of stroke with isoflavone group was significantly higher than that of stroke without isoflavone group in femur neck. CONCLUSION: The results suggested that isoflavone supplement in stroke rat had beneficial effect on bone metabolism from the initial stage of stroke.