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PubMed1975

Medullary rays. Visualization during excretory urography.

The medullary rays are well-defined anatomic structures consisting of bundles of renal tubules which form in the renal cortex and continue through the renal medulla as the medullary striations. These structures are occasionally visualized during excretory urography in abnormal physiologic states characterized by tubular stasis and hyperconcentration of contrast material. Under these conditions, fine striations are visualized which correspond in position and orientation to these structures. The work of others has shown that in tubular stasis, contrast material is hyperconcentrated in the tubules. On microradiography in normal and obstructed kidneys, the highest concentrations of contrast material are seen in the lumen of collecting ducts. Lastly, retrograde injection of contrast material into the medullary rays produces a roentgen image similar to our illustrated cases.

Humans↗

PubMed1989

[Process of regeneration of cementum observed by various fluorescent-labeling methods].

The purpose of this study was to evaluate the effect of various fluorescent-labeling methods on longitudinal information associated with the process of regeneration of cementum after periodontal therapy. Mandibular bilateral premolars and molars in three monkeys were used. Prior to the labeling, experimental periodontitis was surgically produced at the mesial site of each tooth. In four weeks, scaling and root planing were carried out, and time marking was performed by injection of 3 kinds of fluorescent-labeling materials, tetracycline hydrochloride (30 mg/kg), calcein (8 mg/kg), and alizarin complexon (20 mg/kg), intramuscularly. The animals were sacrificed 4 days after the last injection and serial sections without decalcification were prepared. They were examined under a fluorescence microscope and further observed by contact microradiography (CMR) and staining with toluidine blue. According to the observations made by fluorescence microscopy, marked regeneration of the cementum was revealed by each of the 3 labeling agents. Also, the presence of regenerated cementum was supported by the observations by CMR and after toluidine blue staining. In addition, the regeneration of new cementum was shown to start in about 2 weeks after scaling and root planing. Judging from the results of this experiment, the various fluorescent-labeling methods seem to be effective for observing the process of regeneration of cementum.

Animals↗

PubMed1989

[Self-setting apatite cement. 6. Possibility as bone substitute].

Self-setting apatite cement was investigated to evaluate its use as a possible bone substitute in the rat femur. The implant sites were recovered at intervals up 12 weeks postoperatively and investigated by the use of x-ray diffraction, contact microradiography, light and electron microscopy. By x-ray diffraction analysis, the cement placed for at least one day in the medullary canal of rats was found to be completely converted to a set phase of hydroxyapatite resembling the main inorganic phase of bone. In any specimens prepared at 1, 4, 12 weeks after implantation, no appreciable foreign body response was observed in the tissue around the set cement. At four weeks after implantation the set cement was in tight contact with the newly formed bone which appeared to involve osteocytes in lacunae and osteoblastic cells on its surface. At twelve weeks after implantation, the newly formed bone tended to grow into the interior of the set cement. With scanning electron microscopy, the newly formed bone was found to be directly deposited on the set cement. The newly formed bone consisted of fine needle-like crystals. These results strongly suggest that this cement is well tolerated by bone tissue and osteogenesis when used as a bone substitute. The advantage of the present material as a promising bone substitute is that it can be filled in surgical or traumatic bone defect as a slurry or paste.

Animals↗

PubMedDate not supplied

[Bone mineralization and mineral status].

After initial calcification in matrix vesicles or collagen fibrils, bones are continually modified by modelling then remodelling. In bone tissue, the degree of mineralisation of bone structural units is heterogeneous, reflects the rate of bone remodelling, and can be measured using microradiography. Our model is based on the fact that bone remodelling activity and thus the duration of the secondary mineralisation of bone tissue would influence its mineral status (mainly its degree of mineralisation or bone density at tissue level). When the bone remodelling rate increases (menopause, parathyroid hormone), the degree of mineralisation of bone tissue decreases. Conversely, after a diminution of the remodelling rate induced by antiresorptive treatments, the degree of mineralisation of bone tissue increases. Strontium ranelate (PROTELOS) has been tested to date as a potential therapeutic agent in patients suffering from postmenopausal osteoporosis. Recent phase III studies (the Spinal Osteoporosis Therapeutic Intervention [SOTI] study and the TReatment Of Peripheral Osteoporosis Study [TROPOS]) show a decrease in the vertebral and extravertebral fracture risk and an increase in bone mineral density measured at lumbar spine and femoral levels. Strontium ranelate has a unique mechanism of action, since it decreases bone resorption and increases bone formation ('decoupling' agent). Our preliminary observations in animal and man reveal that, because of this dual mechanism of action, the degree of mineralisation of bone tissue and the crystal characteristics of bone mineral are maintained at normal levels. More generally, these data indicate that the mineral status of bone tissue should be systematically taken into account during histomorphometric studies of bone.

Alendronate↗

PubMed1978

Penetration of ions from silicate cement restorations into Copalite--covered cavity walls.

This study aimed to asses the effect of silicate cement on Copalite -covered cavity walls in extracted human teeth. Class V cavities were prepared in 24 premolars and filled with silicate cement (Bio-Trey). Four cavities were unlined, the rest of the cavities were lined with 1 or 2 layers of Copalite before insertion of the restorations. After 6 months, 70-100 microns thick longitudinal sections of the teeth were studied by polarized light microscopy, microradiography and electron probe microanalysis. When imbibed in water or quinoline, a subsurface zone of altered birefringence was noticed in nearly all cavity walls. Nearly half of the cavity walls in the experimental groups showed a surface zone of increased radiopacity. In a few instances a subsurface radiolucent zone was present. By electron probe microanalysis F (0,4-3% by weight), Zn (1-4%) and Al (0,2-6%) were measured in the outer 10-60 microns of the cavity walls. The study shows that even with a double layer of Copalite, known to prevent microleakage, a desirable uptake of F and Al from silicate restorations into cavity walls can take place. Copalite does not prevent a phosphoric acid effect on the cavity walls.

Aluminum↗

PubMed1979

Distribution of corrosion products in teeth restored with metal crowns retained by stainless steel posts.

The nature and distribution of corrosion products in teeth restored with metal crowns retained by stainless steel posts were examined by means of energy-dispersive X-ray microanalysis, microradiography, and electron microscopy. The corrosion products consisted of calcium, phosphorous, iron, chromium, nickel, zinc, stannum and other elements. A possible root fracturing mechanism is discussed.

Corrosion↗

PubMedDate not supplied

Quantum type bone remodeling in the otic capsule of the pig.

Normal quantum type bone remodeling was studied in temporal bones of young domestic pigs by means of combined microradiography, osteofluorochrome labelling and osteoid staining. Evolving secondary osteons were morphologically normal although much less in the otic capsule than in the surrounding compacta of the temporal bones or in long bones. Moreover, remodeling was totally absent in bone tissue immediately adjacent to perilymphatic spaces suggesting the presence of a local mechanism controlling resorption and perhaps formation in the bony otic capsule.

Animals↗

PubMedDate not supplied

Provoked repetitive healing of mature bone tissue following irradiation. A quantitative investigation.

A titanium implant, the bone harvest chamber (BHC), was used to investigate the regenerative capacity of mature bone after irradiation. One BHC was inserted in each proximal tibial metaphysis of a rabbit. One of these implant sites was irradiated (60Co single dose) to either 15 or 25 Gy while the other served as control. Newly formed bone grew through a canal that penetrated the implant. This newly formed bone was harvested from the implant every three weeks following irradiation and then quantified by microradiography and computer-assisted densitometry. In this way a ratio between bone formed on the irradiated side in comparison with the control could be established. An immediate depression in bone formation compared with the non-irradiated controls, was seen at both dose levels. A recovery in bone regenerative capacity was seen at 15 weeks after 15 Gy while the decrease in bone formation remained constant after 25 Gy during the 30 week follow-up period.

Animals↗

PubMedDate not supplied

Bone healing following irradiation during tourniquet ischaemia.

The bone harvest chamber (BHC) methodology, a titanium implant for quantitative evaluations of bone healing, was used in order to investigate the radioprotective function of anoxia, in healing bone tissue. After incorporation of one BHC in each proximal tibial metaphysis of a rabbit it was possible to collect newly formed bone specimens in 3-week-periods without animal sacrifice. The amount of bone was determined by microradiography and densitometry. Ten animals divided into 2 groups were used. One group receiving a single dose of 25 Gy during tourniquet ischaemia was compared with another receiving the same dose during normal blood perfusion. A significantly improved bone healing response was seen in the ischaemic group, with a tendency to further improvement with increasing time after irradiation.

Animals↗

PubMed1985

Effects of direct currents on bone growth into delrin implants.

The delrin Bone Growth Chamber (BGC) which is a dividable implant, was inserted in its assembled form in the tibial metaphysis of the rabbit. The BGC allows a numerical estimation of the bone growth into the implant, based on microradiography and microdensitometry that permits evaluation of direct current (DC) effects on bone regeneration. A test chamber was inserted in one tibia and was stimulated with either 5, 20 or 50 microA for three weeks, while on the contralateral side of the same animal, a control implant was inserted under identical conditions as the test, but was not stimulated. The results showed a significant increase of bone growth with 20 and 50 microA and a tendency towards more bone formation with 5 microA.

Animals↗

PubMed1985

Alterations in bone regenerative capacity after low level gamma irradiation. A quantitative study.

In the present study the influence of single 2.5 and 5 Gy doses of irradiation on the regenerative capacity of mature bone tissue has been investigated. To the knowledge of the present authors, no quantitative analysis of bone repair after low doses of irradiation has been presented previously. The experimental model used was the Bone Growth Chamber (BGC), which is a porous implant made of titanium. Each one of twenty animals was irradiated with 2.5 or 5 Gy to one tibial metaphysis. Directly after irradiation each animal had BGC:s inserted bilaterally into the tibial metaphyses. Thus, each animal served as its own control. Four weeks after irradiation the BGC:s were removed and the newly formed bone was collected from the implant pores and was analyzed by microradiography and quantified by microdensitometry and histology. It was found that 2.5 Gy irradiation led to no statistically significant alteration in bone formation as compared to non-irradiated controls. At the 5 Gy dose level, however, there was a significant reduction of bone formation as compared to non-irradiated controls.

Animals↗

PubMed1987

Experimental mandibular fracture: studies on bone repair and remodellation.

An experimental mandibular fracture model was developed in Sprague-Dawley rats. Healing and remodellation were studied using routine histology, microradiography and incorporation of tetracycline and lead acetate. Bone healing after fracture started by outgrowth of bone trabeculae from the periosteum and from marrow spaces in the mandibular corpus and coronoid process. Stabile fracture healing was seen after 14-16 days, which correlated to the time when bone trabeculae were seen to cross the fracture diastasis morphologically. Formation of reparative bone was produced by direct formation of bone trabeculae but also via formation of a chondroid tissue which was later resorbed and replaced by bone.

Animals↗

PubMed1975

The influence of acrylic cement on the femur of the dog. A histological study.

Using dogs as experimental animals, polymerizing methylmethacrylate was inserted into the marrow cavity of the femur. The influence on bone over a period of 21 months was studied by means of histological techniques and microradiography. To distinguish the effect of the methacrylate proper from the circulatory disturbance resulting from the operation, control experiments were performed in which the marrow cavity was emptied, but no acrylic cement was inserted. Polymerization of the methacrylate in vivo resulted in a local rise in temperature to about 58 degrees C. In the femurs containing the acrylic cement a consistent picture developed, consisting of: a) necrosis and removal of the central part of the cortex and b) apposition of a thick layer of bone on the outer surface of the cortex, c) deposition of a cylindrical bone sleeve in contact with the methacrylate. In the control experiments only a minimal resorption at the inside surface of the cortex and the deposition of a thin layer of bone at the outside of the cortex were observed. It is concluded inter al. that circulatory distrubance contributes only slightly to the total reaction of bone to the insertion of methacrylate.

Animals↗

PubMed1976

Porous ceramics as a bone substitute in the medial condyle of the tibia. An experimental study in sheep.

A new porous ceramic material was tested for possible use as a bone substitute in regions exposed mainly to compressive forces. The porous ceramics were implanted into the medial condyle of the tibia of four sheep and left in position for 3 months. The operated tibia was then removed and sections were made of the implants. The sections were studied by transmitted light microscopy, microradiography and scanning electron microscopy. There was no apparent loss of function of the operated leg and the implants were found to be bound to the adjacent bone by ingrowth of bony tissue, in some regions to a depth of 2-3 mm. It is concluded that the properties of the porous ceramic implants justify a clinical trial, provided that the results of long-term animal experiments are equally satisfactory.

Animals↗

PubMed1977

Porous ceramics as a bone substitute in the medial condyle of the tibia. An experimental study in sheep. Long-term observations.

A recent 3-month implantation study indicated that a new porous ceramic material might be suitable as a bone substitute in regions exposed mainly to compressive forces. The porous ceramics were implanted into the medial condyle of the tibia of sheep. In the present study the implants were left for 10 months in three animals, and 12 months in two. In the two animals with 12 months' observation, the plate which had been used to stabilize the implant was removed at 10 months. The implants and the adjacent bone tissue were studied macroscopically, radiographically and by microradiography and transmitted light microscopy. All the implants were bound to the adjacent bone by ingrowth of bony tissue. The depth of the bony invasion was slightly greater than that observed at 3 months, being maximally 3-4 mm. Some signs of ossification were still seen within the pores. The bony bridges between the implants and the surrounding bone were particularly well developed in regions of maximal stress. This was interpreted as a sign of active adaption of the bone formation to the actual stress to which the shearing surfaces were exposed. It is concluded that the properties of the porous ceramic implants justify a clinical trial in man.

Animals↗

PubMed1982

Fibrin adhesive system (FAS) influence on bone healing rate: a microradiographical evaluation using the bone growth chamber.

A dividable titanium implant containing two canals was inserted into both tibial metaphyses of 5 adult rabbits to test whether the Fibrin Adhesive System (FAS) can accelerate bone regeneration. On one side the implants were pretreated with FAS whereas the implants on the contralateral side were bathed in autologous blood and marrow. After a healing time of 4-5 weeks the assembled implants were removed and then taken apart. The amount of bone which had grown into the canals was quantified by microradiography and microdensitometry. The FAS-treated implants showed a tendency to contain less bone than the medullary cell-treated ones. It is concluded that more evidence should be gathered before recommending FAS treatment to accelerate bone regeneration. It is submitted in addition that the dividable titanium implant, the Bone Growth Chamber, may be useful for quantification of early bone formation under various experimental conditions.

Absorptiometry, Photon↗

PubMed1983

Morphological changes in bone following intramedullary implantation of methyl methacrylate. Effects of medullary occlusion: a morphometrical study.

Using a computerized, semi-automatic morphometrical system, the morphological effects on diaphyseal rat femur following intramedullary implantation of methyl methacrylate were studied. Furthermore a comparison with the effects of periosteal elevation and removal of the bone marrow by suction was made. The changes in bone morphology were studied with the aid of microangiography, microradiography, fluorescence microscopy and histology. The results showed that there were evident differences between the postoperative course of the three procedures regarding vascular changes in the femoral cortex, bone remodelling and extent and duration of cortical necrosis. Implantation of methyl methacrylate caused greater vascular disturbance than elevation of the periosteum and removal of the bone marrow.

Angiography↗

PubMed1993

The effect of fracture on femoral head blood flow. Osteonecrosis and revascularization studied in miniature swine.

Miniature swine were used to study the effect of cervical fracture on femoral head blood flow. Laser Doppler flowmetry was used to evaluate femoral head blood flow before and after the fracture, after internal fixation with or without compression, and 8 weeks post-fracture. Fluorescent bone-labeling was performed at 2, 4 and 6 weeks post-fracture. Femoral head blood flow decreased to 40 percent of baseline following fracture, partly from the disruption of venous drainage. Histologically, all femoral heads showed some degree of trabecular thinning, microfracture, and neovascularization when compared with controls. Analyses of the laser Doppler flowmetry data, fluorescent label histology, microradiography and bone densitometry indicated that late (4-6 weeks) revascularization produces severe trabecular mechanical weakening and resultant femoral head collapse. Femoral head ischemia following fracture probably falls along a continuum, with only the more severe cases proceeding to mechanical collapse. Femoral neck fractures in the minipig produce femoral head necrosis of a severity and incidence which closely parallels that of the human population; thus, the minipig is a useful model for further study of complications following femoral neck fracture in humans.

Animals↗