[Peculiarities of reparation regeneration of bone under the influence of anabolic steroids. (Experimental study)].
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Regeneration of bone marrow following radiation only was investigated using 111Indium as a bone scanning agent. Factors which influence local marrow regeneration are dose, age of the patient, and the total amount of the marrow which was irradiated. Time effects are not demonstrated in this study, except to the extent that most regeneration did occur within the first 12 months following irradiation. The most striking finding is the effect of the irradiation volume. Apparent inconsistencies in earlier reports concerning the dose effect could be explained by this effect alone.
A new technique in bone grafting for the correction of a bony cleft and other associated bony defects is discussed. The technique involves the use of composite bone grafts.
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OBJECTIVE: To confirm membrane-guided tissue regeneration in the healing course of segmental bone defects and study the mechanism. METHODS: Segmental, 1 cm osteoperiosteal defects were produced in both radii of 12 rabbits. One side was covered with hydroxyapatite/polylactic acid(HA/PLA) membrane encapsulated as a tube. The contralateral side served as an untreated control. Healing courses were detected by radiographic and histologic examinations. RESULTS: All control sides showed nonunion, whereas there were consistent healing pattern in test sides. CONCLUSION: Membrane technique can promote bone regeneration.
This study compared, in a human model, the ability of (1) expanded polytetrafluorethylene (e-PTFE) membranes plus bone-chip autografts, (2) e-PTFE membranes plus demineralized freeze-dried bone, (3) e-PTFE membranes plus a new form of demineralized allograft bone tissue, and (4) e-PTFE membranes alone to enhance bone regeneration around dental implants placed into recent extraction sockets. The histologic results demonstrated that, in humans, guided tissue regeneration techniques are capable of producing new bone osseointegrated with titanium dental implants. Among the graft materials, autogenous bone provided the densest and the greatest amount of bone formation, but use of demineralized freeze-dried bone and a new form of de-mineralized allogenic bone matrix also improved bone regeneration compared to membranes alone after 6 months of healing.
Experiments were conducted on rabbits. Changes in ATP in the regenerating bone tissue after incomplete osteotomy and removal of a bone section, and also in cases of reparative osteogenesis stimulation in the region of the bone defect by means of pulse electric current were studied. ATP content in the bone callus after incomplete osteotomy and electrostimulation proved to exceed such in the regenerating bone tissue following removal of the bone fragment when no stimulation was applied. On the basis of the data obtained it is suggested that improvement of energy provision of the fracture consolidation process was one of the important links in the mechanism of stimulating influence of the electric current on the reparative regeneration of the bone tissue.
This report describes observations of healing following guided tissue regeneration (GTR) including surgical implantation of the prostaglandin E1 analog misoprostol with calcium-layered methacrylate particles. Critical size, supra-alveolar periodontal defects were surgically created around the 3rd and 4th mandibular premolar teeth in 4 beagle dogs. Wound management included soaking with a 24 microg/ml misoprostol solution and implantation of the misoprostol/methacrylate composite. One jaw quadrant per animal was prepared for GTR using expanded polytetrafluoroethylene membranes. The gingival flaps were coronally advanced and sutured to submerge the teeth. The tissues covering the surgical sites daily received topical misoprostol in an oral adhesive over the 4-week healing interval. Upon euthanasia, tissue blocks were prepared for histometric analysis of regeneration of alveolar bone and cementum, root resorption and ankylosis. The defect area underneath the membrane and the density of methacrylate particles were recorded for the GTR defects. The methacrylate particles appeared encapsulated in a dense connective tissue without signs of an inflammatory reaction, some in contact to newly formed bone. Alveolar bone regeneration height averaged (+/-SD) 1.2+/-1.0 and 1.0+/-0.6 mm for GTR and non-GTR defects, respectively. Corresponding values for bone regeneration area were 1.3+/-1.0 and 0.7+/-0.5 mm2. Cementum regeneration was confined to the apical aspect of the defects. Small areas of root resorption and ankylosis were observed for all teeth. Bone regeneration area correlated positively to the defect area and negatively to the density of methacrylate particles in the GTR defects. The histologic observations suggest that the methacrylate composite has marginal potential to promote bone and cementum regeneration under provisions for GTR.
The postablation bone marrow regeneration model is an in vivo paradigm of synchronous bone formation and resorption restricted to a defined reference anatomical location. The blood clot that fills the medullary cavity immediately after marrow removal is organized by replacement with primary cancellous bone. At the peak of the osteogenic phase almost the entire medullary cavity is filled with the trabecular mesh. The primary bone trabeculae are then subjected to osteoclastic resorption and replacement by intact marrow. Since in animals of defined strain, sex and age the timing and extent of formation and resorption are highly reproducible, the postablation model in combination with simple vital methods and/or bone histomorphometry as well as molecular and biochemical approaches applied at specified time periods provides an efficient in vivo tool to assess the efficacy of antiresorptive agents as well as their possible adverse effects on bone formation. When applied to transgenic animals this model may become useful to determine the role of individual genes in matrix formation, mineralization and resorption.
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Despite the general clinical acceptance of distraction osteogenesis and much attention to bone formation in this method, little is recognized about activated bone resorption in the regenerated bone. The purpose of this study was to demonstrate the simultaneously activated bone resorption with activated bone formation and to investigate the role and efficacy of bisphosphonate in distraction osteogenesis. Left tibiae of 54 immature rabbits were lengthened for 3 weeks at a rate of 0.7 mm/day after a 1-week lag. Regenerated bone was quantitatively investigated by radiographic bone density, bone histomorphometry, and three-point bending testing. Animals received either vehicle or nitrogen-containing bisphosphonate (N-BP), YM529/ONO5920 at doses of 0.4 mg/kg/w or 0.004 mg/kg/w for 6 weeks. Regenerated bone of the vehicle group showed a radiologically characteristic zone structure containing the osteopenic zones adjacent to the sclerotic zones. The regenerated bone of the 0.4-mg/kg/w group showed no osteopenic zones during the course and eventually became homogeneously radiodense. The bone volume corresponding to the osteopenic zone of this group was 5.6-fold greater compared with that of the vehicle group. The lengthened bone strength of this group was 3.3-fold greater in ultimate force than that of the vehicle group and equivalent to the contralateral tibia. The 0.004-mg/kg/w group had no substantial differences compared with the vehicle group, despite radiological enhancement of the mineralized front as well as somewhat delayed bone resorption. These results demonstrate that not only bone formation but also bone resorption is highly activated in the regenerated bone, implying high bone turnover. Sufficient N-BP caused a notable modulation in morphological properties of the regenerated bone through inhibition of highly activated bone resorption and eventually increased mechanical properties.
Some experiments in rabbits have presented the potential feasibility of using shape memory alloy spring for continuous distraction osteogenesis. To confirm the effectiveness of such method, we established canine models for the exploratory experiments of transport distraction osteogenesis using nitinol springs. Simple devices, including an internal 60-mm long sinusoid-shaped nitinol springs were used in the study. All dogs needed only one operation. In the operation, osteotomy was performed to create a 40-mm unilateral segmental mandibular body defect and a tooth-bearing transport bone disc. After reconstructive fixation of the remnant mandible, the spring was constricted and anchored across the distraction gap to activate transport distraction immediately. At the second experimental stage, an ePTFE sheet was further fixed to protect the defect and distraction gap before closing the incision. Control dogs underwent the same operation except for anchoring of the spring to examine the spontaneous bone regeneration. Automatic bone transportation, as a gradual slowdown process, was observed under the effect of the spring. The transport disc could get to the opposite side of the defect, or stopped halfway when ePTFE sheet intervened. Mandibular reconstruction was achieved in all these dogs and better in dogs with sheet protection. No integrated bone mass was found in the defect of control dogs. The study further proves that continuous distraction osteogenesis using nitinol springs is a practical technique, although the devices need more improvement for better control of the process of distraction and the quality of regenerated bone.
The placement of endosseous dental implants is often hampered by unfavorable anatomy of the alveolar bone. Guided bone regeneration and bone grafts have been used to reconstruct deficient alveolar ridges in preparation for dental implants. A case report is presented to illustrate two approaches to successful management of different alveolar defects.
In mouse, the administration of chemical protectors before an irradiation induces a more rapid bone marrow regeneration and an increased lymphoid rebound. In the thymus, the late atrophy is reduced. Separately administrated, the protectors decrease greatly the thymocytes number but have no effect on the marrow population.
The purpose of this pilot study was to experimentally evaluate tooth movement through regenerate bone at an early time point during the consolidation phase after bilateral mandibular osteodistraction. Two beagle dogs underwent 10 mm of bilateral mandibular lengthening via intraoral distraction osteogenesis between the fourth premolars and first molars. After 1 week of consolidation, retraction of the fourth premolars was initiated. Immediately after completing premolar retraction, the dogs were sacrificed and the mandibles were analyzed radiographically, histologically, and by dental cast measurements. Initially, all 4 fourth premolars moved distally, with 2 of the 4 touching the first molars at the time of sacrifice. Based on the current data, it is possible to move teeth through regenerate bone, and it appears that tooth movement can begin within weeks of starting the consolidation period.