Expression of osteoprotegerin and receptor activator of nuclear factor kappa-B ligand in mandibular ramus osteotomy healing with administration of different doses of parathyroid hormone / 中华口腔医学杂志

Objective@#To investigate the effect of parathyroid hormone (PTH) on the bone healing of mandibular ramus osteotomy.@*Methods@#The mandibular ramus osteotomy model was established in sixty rabbits and these rabbits were randomly divided into experimental group A, experimental group B and control group. In the experimental group A and experimental group B, the rabbits were given PTH (20 and 40 μg/kg respectively) every other day after operation. In the control group, 1 ml saline was given. The animals were sacrificed at 1 week, 2 weeks, 3 weeks and 4 weeks postoperatively. The new bone formation was observed by histology and cone bone CT. The expression of osteoprotegerin and receptor activator of nuclear factor kappa-B (RANKL) in the new bone was detected by real-time quantitative PCR.@*Results@#The experimental groups has better osteogenesis and the bone mineral density than the control group in osteotomy area. The experimental group B showed the best osteogenesis.Osteoprotegerin mRNA expression in experimental group A (1.127±0.035, 1.742±0.049, 1.049±0.062, 1.063±0.036) was significantly higher than that in the control group in each period (0.965±0.082, 1.254±0.071, 0.793±0.061, 0.684±0.055) (P=0.010, P=0.000, P=0.001, P=0.020), while group B (1.416±0.205, 2.648±0.168, 1.652±0.091, 1.712±0.070) was significantly higher than group A (P=0.000, P=0.010, P=0.023, P=0.003). RANKL mRNA expression in control group (1.666±0.086, 1.058±0.105, 0.885±0.124, 0.972±0.136) was significantly higher than that of the group A (0.788±0.036, 0.585±0.017, 0.692±0.017, 0.527±0.051) (P=0.001, P=0.006, P=0.003, P=0.028) in each period, while group A was significantly higher than group B(0.247±0.022, 0.240±0.034, 0.134±0.011, 0.103±0.050) (P=0.000, P=0.001, P=0.002, P=0.012).@*Conclusions@#PTH can upregulate the expression of osteoprotegerin and reduce expression of RANKL, thus promoting new bone formation. Intermittent administration of high dose of parathyroid hormone can further promote the healing process after mandibular ramus osteotomy.

Osteoprotegerin/receptor activator of nuclear factor-κB ligand expression in mandibular distraction osteogenesis regulated by parathyroid hormone / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This research aimed to investigate the expression of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) in mandibular distraction osteogenesis (DO) regulated by parathyroid hormone (PTH) and to explore the mechanism by which PTH promotes DO.</p><p><b>METHODS</b>A rabbit mandibular DO model was established. The rabbits were randomly divided into experimental group and control group. The former were subcutaneously injected with different doses of PTH on alternate days, the latter was injected with normal saline every other day. Serum OPG levels were detected through enzyme-linked immunosorbent assay. The OPG and RANKL expression levels in the DO-induced formation of a new bone tissue were examined through immunohistochemistry staining.</p><p><b>RESULTS</b>The serum OPG levels gradually increased during distraction. At the end of the stretch, the OPG expression in the experimental group was significantly stronger than that in the control group. As the fixed period was extended, the OPG expression in the new bone gradually decreased, but the RANKL expression increased.</p><p><b>CONCLUSION</b>Intermittent subcutaneous PTH injection can upregulate the OPG expression and accelerate bone metabolism. Thus, this procedure promotes the early generation of a new bone in the mandible through DO.</p>

Changes in the inferior alveolar vessels and angiogenesis following mandibular lengthening with different rates of distraction / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of this study was to study the changes in the inferior alveolar vessels and angiogenesis following mandibular lengthening with different rates of distraction.</p><p><b>METHODS</b>Bilateral mandibular corticotomies were performed in 6 goats. The mandibles in 6 goats were lengthened 10.0 mm using a custom-made distractor with different rates of distraction (1.0 mm/d[n = 3] and 2.0 mm/d [n = 3]); the other 2 nondistracted mandibles served as control. The goats with distracted mandibles were killed at 2 weeks after completion of distraction. The inferior alveolar vessels with distracted calluses were harvested and processed for histologic and morphometric evaluation.</p><p><b>RESULTS</b>No pathological changes in the inferior alveolar vessels were found following mandibular osteodistraction. However, the number of microvessels within distraction gap in the animals distracted at a rate of 1.0 mm/day was greater than that in the goats distracted using a rate of 2.0 mm/day, and more mature newly formed bone trabeculae was observed.</p><p><b>CONCLUSION</b>There were no significant changes in the inferior alveolar vessels after mandibular lengthening with distraction osteogenesis, but rapid distraction may have adverse effects on the aniogenesis in the distraction gap.</p>

Biomechanical properties of regenerated bone by mandibular distraction osteogenesis / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To study the biomechanical properties of the new bone generated by mandibular distraction osteogenesis (DO).</p><p><b>METHODS</b>A total of 11 healthy adult goats were randomly divided into 2 groups, the experimental group (n=9) and the control group (n=2). For the goats in the experimental group, the bilateral mandibles were gradually lengthened for 10 mm with distraction appliances. Three goats were sacrificed respectively at 2, 4 and 8 weeks after completion of distraction. Compressive, three-point bending and shearing tests were conducted on the standard regenerated bone samples and the whole unilateral mandibular specimens. For the goats in the cont rol group, no operation was made and the whole unilateral mandible was taken as the test specimen.</p><p><b>RESULTS</b>The compressive strength and bending stiffness of the new bone reached the normal level at 4 and 8 weeks after completion of distraction, respectively. But the shearing strength remained significantly weaker than that of the controls at 8 weeks after distraction.</p><p><b>CONCLUSIONS</b>The distraction appliance can be removed and the lengthened mandible should be exposed to adaptive functional exercise at 8 weeks after completion of distraction.</p>