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At least 991 records · Page 55Linked to original sources

PubMed1998

Incorporation of cortical bone allografts and autografts in rats: expression patterns of mRNAs for the TGF-betas.

Healing of bone grafts is dependent on the rate of new bone formation. To understand better the regulation of new bone formation in the graft we have studied local production of TGF-beta1, 2 and 3, and of the small proteoglycans by determining their mRNA levels in a rat bone graft model. These mRNA levels were compared to the healing rates of autografts and allografts, as determined by histology, UV-microscopic evaluation of tetracycline-labeled new bone formation, microradiography and mechanical testing at 1, 2, 4 and 8 weeks of healing. Analyses showed that, analogous to slower bone formation in allografts, the induction of TGF-beta1 gene expression was slower than in allografts, when compared with autografts. A similar delay was seen in decorin gene expression. The results agree with the suggested role of TGF-beta1 in induction of type I collagen and osteonectin production. Our findings thus support the view that locally produced TGF-beta1 plays a role in normal graft incorporation, while local production of TGF-beta3, and particularly TGF-beta2, may be less important in this respect.

Animals↗

PubMed2003

The effect of delayed autogenous bone grafting on the healing of diaphyseal defects in a canine model.

Bone grafting of osseous defects is often delayed to minimize the risk of infection, however, the effect of this delay on defect healing is not clear. Unilateral oblong unicortical diaphyseal femoral defects (30 x 4.5 mm) were created in 3 groups of 18 adult canines that were grafted with autogenous bone immediately, at 2 weeks, and at 6 weeks. After an 8-week healing period, paired femurs, h consisted of defect versus intact specimens, were assessed by biomechanical testing and microradiography. No differences were demonstrated biomechanically or radiographically between the healing defects with immediate versus delayed bone grafting. This study suggests that within the first 6 weeks postoperatively osseous defects can be grafted with autologous bone without adversely affecting bone graft incorporation.

Analysis of Variance↗

PubMed1989

[Effects of Er:YAG laser irradiation on human extracted teeth].

The ablation effects of the Erbium:YAG laser (wave length: 2.94 microns) on the human extracted teeth were examined histopathologically. The enamel surface of the human extracted tooth was irradiated by the laser at 500 mJ, 1 pps or 3 pps: 3, 15, 30, 50 and 100 shots. After observation under a dissecting microscope, the teeth were placed in a demineralizing solution of 0.1 M lactate buffer with 6% hydroxyethyl cellulose (pH 4.5) in order to evaluate the acid resistance of the enamel adjacent to the ablated area. After 4 days, the degree of demineralization of the surrounding enamel was assessed by contact microradiography. The result showed that every irradiated tooth had a clear-cut defect, and almost all the teeth had acquired acid resistance at the enamel surrounding the ablated portion. The other experiment was carried out to estimate the effects of the Er:YAG laser through a contact probe. The enamel, dentin and cementum of the extracted teeth were irradiated at 39 mJ or 74 mJ, 10 pps; 10 shots. The teeth were observed under a dissecting microscope. The result clearly indicated that the Er:YAG laser guided by the contact probe could also produce a defect in the dental hard tissue. The above-mentioned findings suggested that the Er:YAG laser could pave the way for the cavity preparation with acid-resistant cavity margin.

Dose-Response Relationship, Radiation↗

PubMed1976

[Industrial fluorosis].

43 potroom workers (aluminium industry) with fluorosis have been compared with 18 foundry workers of the same age, but who had never been exposed to fluorides. Clinical examination revealed a higher incidence of articular pain and limitation of motion in the exposed group. The diagnosis of fluorosis is not only clinical but calls for other investigations such as urinary fluoride determination, bone radiology and, above all, bone biopsy for fluoride determination, histology and microradiography.

Aged↗

PubMed1998

Morphology of peri-implant regenerated bone, in sheep's tibia, by means of guided tissue regeneration.

BACKGROUND: No data on the resistance to functional loads of bone regenerated by means of guided tissue regeneration, can be found. In this paper the new-formed bone is analyzed, in cases that see the surgical creation of defects in testing animals. The morphological aspects of perimplant bone, regenerated by means of bone substitutes or not, were evaluated. METHODS: A coronal defect was created by means of a counter-sink bur. The following step provided for osseointegrated fixtures, with a machined or blasted (TiOblast) surface, to be installed. Some bone defects were filled with Bio-Oss, and covered with resorbable membrane (Vycril), others were left unfilled. The animals were sacrificed after different periods of time (24 and 45 days). Some thick sections (200 microns) underwent then microradiography and were examined with a microscope, under transmitted and polarized light. Other sections, thin (5 microns), were coloured with toluidine blue, Gomori's Stain and Solochrome Cyanine/Congo red. RESULTS: Data confirm the excellent behaviour of bovine bone and of TiO blasted fixtures. The experimental results bring into evidence that, in cases of Guided Bone Regeneration (GBR) by means of membrane, the use of fixtures with a blasted surface (TiOblast), and of Bio-Oss as bone substitute, made osseointegration easier. CONCLUSIONS: Results, moreover, suggest that in case of implant surgery with GBR, in order to allow the maturation of regenerated bone, it's healing time must be prolonged.

Animals↗

PubMed1978

[Spontaneous formation of angiogenic woven bone within cancellous bones. Some observations on microfractures of isolated trabecula (author's transl)].

Femoral heads removed for subcapital fracture of the femur were embedded in methacrylate. Contact roentgen films of slabs of 1--2 mm thickness were screened for aggregates of woven bone. A variety of form exceeding that seen by other methods was found, not only in association with isolated trabecula. The distribution was found to confirm earlier findings by Todd et al. (1972), Freeman et al. (1974) and Watson (1975). The aggregates were seen more frequently in porotic areas than in the trajectorial groups of trabecula in the femoral heads. Aggregates of typical shapes were also found in one hemipelvis and in a humeral head. In embedded specimens discontinuities were seen in some trabecula with aggregates and not in other elements. There was no evidence of cracks where aggregates were attached to the edges of bone plates. Some trabecula with aggregates were ground down to 100 micrometer for microradiography. Cracks of the underlying trabecula could be shown, but neither signs of resorption nor of formation or osteocyte activation could be found. Aggregates of woven bone within cancellous bone have been found in subchondral bone of experimental animals being impact loaded and in connection with discontinuities. They are found near areas bypassed by the transmission of loads, too, in osteoporosis beside the groups of pricipal trabecula, and without association with discontinuities. It is concluded, that aggregates of woven bone are the product of mesenchymal activation or some defect in the regulation of mesenchymal activity and associated with causes of bone atrophy rather than with specific mechanical conditions.

Fatigue↗

PubMed1999

Prenatal development of the human pelvis and acetabulum.

The prenatal development of the human pelvic bone and acetabulum has been studied by means of classical histology and microradiography. The embryonic phase leads to a fully developed hip within 8 weeks of gestation. The fetal period is a growth phase, including the following main features: endochondral ossification of the ilium from the ninth week, asymmetrical development of the iliac shaft from the fifteenth week, "chondroid-like" tissue formation above the acetabulum from the twenty-sixth week and haversian bone remodelling from the twenty-eighth week. The fetal development of the pelvis and acetabulum seems to be highly related to mechanical stimuli, the most important being the gluteal muscular activity and the simultaneous pressure of the femoral head.

Acetabulum↗

PubMed1975

[Report of case of opalescent dentin. A polariation optic and microradiographic study on a pulpless tooth].

Ground sections prepared from a molar (-7) with opalescent dentine were investigated by the means of polarizing microscopy and microradiography. Histological and clinical findings are discussed. Unfortunately, heredity could not be surely determined. But in all experience we are shure, that a hereditary mutation, recently or earlier in a generation occured, was the cause also in this case.

Adult↗

PubMed1999

Remineralization by fluoride enhanced with calcium and phosphate ingredients.

The effectiveness of fluoride ions provided by toothpastes and mouthrinses in promoting remineralization can be limited by the low concentrations of calcium and phosphate ions in saliva. The purpose of this study was to determine whether improved remineralization can be obtained from toothpastes or mouthrinses that simultaneously deliver fluoride, calcium, and phosphate ions from dual-dispensing systems. Enamel specimens with artificial lesions between 60 and 90 microns deep were cycled 15 times through demineralization for 30 minutes, treated for 5 minutes with an experimental or control fluoride toothpaste or mouthrinse, and remineralized for 60 minutes. In the toothpaste study, surface hardness increased by 11.5 +/- 9.2 and 2.7 +/- 3.6 Vickers hardness units, and enamel fluoride content was 5984 +/- 521 ppm and 3971 +/- 531 ppm for the experimental and control fluoride toothpastes, respectively. Remineralization was confirmed by x-ray microradiography. In the mouthrinse study, surface hardness increased by 8.8 +/- 7.7 and 2.2 +/- 3.7 Vickers hardness units, and enamel fluoride content was 6111 +/- 1078 ppm and 3160 +/- 364 ppm for the experimental and control fluoride mouthrinses, respectively. Use of a non-fluoride control mouthrinse led to a decrease in surface hardness of 3.7 +/- 5.2 Vickers hardness units despite a fluoride content of 402 ppm. The results demonstrate that calcium and phosphate supplementation in a toothpaste or mouthrinse can improve remineralization and increase fluoride uptake.

Calcium Phosphates↗

PubMedDate not supplied

[Controlled gradual lengthening of the mandible after osteotomy].

The procedures used to correct large discrepancies in the length of the mandibular body are described and experimental results are reported. The technique is realized using an orthodontic applicance that permits the progressive lengthening, after osteotomy of the mandibular body and also retains the approximation of the resected mandibular segments. Two dogs were used for the experimentation, achieving mandibular body lengthening of 5 and 15 millimeters. The bone neoformation was studied hystologically by means of microradiography and tetracyclines induced fluorescence. The surgical technique was carried out without damage to the mandibular nerve. The hystological examination shows no conspicous alteration of the nerve fibres.

Animals↗

PubMed2000

Development and repair of cataract induced by ultraviolet radiation.

BACKGROUND: Several epidemiological investigations show a correlation between cataract development and the dose of ultraviolet radiation (UVR) received. It is experimentally well established that exposure of animal eyes to UVR induces cataract. Most cataracts develop as a gradual increase in lens opacity. Despite this, current estimations of toxicity for cataract are based on the concept that cataract is a binary event. Moreover, current exposure limits for UVR are based on subjective inspections with slit lamp microscopy. PURPOSE: The first purpose of the present study was to determine a statistically defined maximum acceptable dose for ultraviolet radiation-induced cataract based on quantitative data of forward light scattering in lenses. The second purpose was to find possible explanations for light scattering by investigating the morphology and the refractive index distribution in the lens. The third purpose was to describe the development of cataract after UVR on the cellular level. METHODS: Six-week-old, female Sprague-Dawley rats received UVR unilaterally in vivo. The radiation from a high pressure mercury lamp was collimated, passed through a water filter and an interference filter or a monochromator (lambdaMAX = 300 nm), and projected onto the cornea. The exposure time was 15 min. The exposure dose ranged between 0.1 and 20 kJ/m2 and the animals were kept between 6 hours and 32 weeks after exposure. The extracted lenses were photographed and forward light scattering was measured. Other methods included light microscopy, fluorescence microscopy, transmission and scanning electron microscopy, freeze-fracture and microradiography. RESULTS AND CONCLUSIONS: From a long-term experiment, it was concluded that UVR-exposed lenses scatter light more than their contralaterals and that a higher dose induces more light scattering. After exposure to 5 kJ/m2, the mean forward light scattering remains unchanged between 1 and 32 weeks. Earlier observations, taken together with the current findings, indicate that the optimal time to detect low dose UVR-induced cataract is one week after exposure in rats. The intensity of forward light scattering increases exponentially with increased UVR dose between 0.1 and 14 kJ/m2. Based on this continuous dose-response, a method to determine a maximum acceptable dose to avoid UVR-induced cataract was developed. The statistically defined lower limit of pathologic light scattering is projected on the dose-response function. The dose corresponding to that point can be estimated and was suggested to be called the Maximum Acceptable Dose (MAD). Two low dose UVR exposures with 0 or 6 h intervals between the exposures produce the same degree of lens opacification. When the second exposure follows 24 or 48 h after the termination of the first, lenticular damage increases. Repair processes between 24 and 48 h after exposure appear to be sensitive to UVR, and an additional exposure during this time may aggravate cataract development. Lenses exposed to UVR grow more slowly than their non-exposed contralaterals. This decrease in lens growth was more pronounced with increasing dose. Low doses led to decreased water content in the lens whereas high doses led to swelling. At 6 months after low dose UVR exposure, no global change of the refractive index was found. However, local variations of the refractive index induce a subtle cortical light scattering. In vivo low dose UVR induces programmed cell death which peaks 24 h post-exposure and involves the entire lens epithelium. Dead cells are removed from the epithelium by phagocytosis. This leads to disintegration of the lens epithelium, associated with flake-like opacities at the lens surface. After one week, the epithelium and the equatorial parts of superficial lens fibers contain extracellular spaces. The extracellular spaces together with locally disarranged fibers produce a corrugated opaque lens surface and equatorial opacities. Within several weeks after ex

Animals↗

PubMedDate not supplied

[A gun silencer of a special kind].

The authors report about a small bore pistol with silencer. In addition, the silencer can be sealed up by a rubber plate. This leads to a false estimation of the shooting distance. Also at close range shots the shot with the silencer and the rubber seal leaves hardly gunshot residues. The bullet wipe persists but microradiography shows his changed morphological composition. The use of the rubber seal leads predominantly to atypical bullet holes.

Autopsy↗

PubMed1999

Protective effects of resin impregnation on demineralization of enamel.

PURPOSE: To determine if resin penetrated into the enamel etch pattern, in the absence of a polymerized outer surface film, could reduce the degree of demineralization of enamel subjected to a simulated caries challenge, and to evaluate whether the addition of fluoride to the resin would enhance reductions in demineralization. MATERIALS AND METHODS: Enamel surfaces of extracted human incisors were acid-etched. One-half of the etched area was treated with an unfilled bonding resin, while the other one-half was left untreated as a control. In another group, this same procedure was followed except the unfilled bonding resin contained fluoride. The applied resin was aggressively air thinned to ensure oxygen inhibition throughout the external surface film thickness. The thinned film was visible light-cured and the area was wiped with an ethanol swab to remove the inhibited layer. The specimens were exposed to a buffer solution of pH = 4.7 for 4 days, and were sectioned and examined by polarized light microscopy and microradiography. RESULTS: In each of the two test groups, the demineralization of the resin-treated side was significantly lower than the control side (P < 0.015). Under the conditions of this study, the experimental fluoride resin did not produce statistically significant reductions in demineralization compared with the non-fluoride resin.

Acid Etching, Dental↗

PubMed2000

Analysis of the hierarchical structure of biological tissues by scanning X-ray scattering using a micro-beam.

The outstanding mechanical properties of biological tissues such as wood or bone are mainly due to their hierarchical structure and to their optimization at all levels of hierarchy. It is therefore essential to characterize the structure at all levels to understand the complex behavior of such tissues. Structures down to the micrometer level are accessible to light or scanning electron microscopic observation. In the case of bone this includes, for example, morphometry of the trabecular architecture or the bone mineral density distribution in cortical and trabecular bone. To characterize the sub-micrometer structure of, e.g., the collagen-mineral composite in the case of bone or the cellulose microfibrils in the case of wood, other methods, such as transmission electron microscopy or X-ray scattering are necessary. The recent availability of extremely brilliant synchrotron X-ray sources has led to the development of the new techniques of scanning small-angle X-ray scattering and scanning X-ray microdiffraction, which are capable of providing structural information on the micrometer and the nanometer level, simultaneously. As a basic principle of the method the specimen is scanned across an X-ray beam which has a diameter of few micrometers. Measuring the X-ray absorption at each position provides an image of the specimen (microradiography) with resolution similar to light microscopy, in the micrometer range. Moreover, the X-ray scattering pattern is analyzed at each specimen position to provide parameters characterizing the structure in the nanometer range. The present paper reviews the principles of the techniques and demonstrates their application to biological materials, such as wood or bone.

Biomechanical Phenomena↗

PubMed1975

Repair of experimental autologous grafts of cortical bone.

Fresh autologous segmental grafts of fibula, four centimeters long, were obtained from thirteen adult dogs. Holes were drilled in each before replantation. The amount of repair was determined after intervals of from four to twenty-four weeks. Torsional stress testing showed that the six drill holes 500 micrometers in diameter confined within an expanse of two centimeters did not mechanically weaken the transplants at the time of surgery. The drill holes were rapidly filled with cancellous bone which matured to cortical bone within twelve weeks. Microradiography and tetracycline labeling of drilled and non-drilled grafts demonstrated similar biological reparative patterns.

Animals↗

PubMed1975

Osteogenesis imperfecta tarda. The morphology of rib biopsies.

Undecalcified bone biopsy specimens from 10 normal individuals and 8 osteogenesis imperfecta patients, 2 to 30 years of age, were analyzed using microradiography as well as ultraviolet, tungsten and polarized light microscope techniques. Biopsies of ribs most reliably reflected the disease process of osteogenesis imperfecta when compared to those biopsies of long bones in the lower extremities deformed enough to require corrective surgery. The rib biopsies consistently revealed that there is a rapid surface turnover of histologically well-organized but osteopenic bone. The high rate of bone turnover is similar to that seen in very young normals but in osteogenesis imperfecta turnover rate does not appear to decline with age. The percentage of surface involved in active new bone formation and in osteoclastic resorption is notably elevated. Excessive osteocyte osteolysis is also characteristic.

Adolescent↗

PubMed1975

The effects of magnesium deficiency on the host response to intramuscular bone matric implanted in the rat.

HCl-demineralized mid-diaphyseal allogeneic segments of tibia were implanted in the lumbar muscles of rats fed either a magnesium-deficient or a magnesium-supplemented diet for one week prior to implantation and for three weeks thereafter. Histological studies, histochemical mucopolysaccharide determinations, tests for protease content of undemineralized bone tissue, and microradiography showed that in the normal hosts mostly trabecular bone grew into the heterotopic site, whereas in the deficient rats a large fibrous covering formed about the implant and in many instances cartilage was present in multiple locations under the fibrous coat. In some instances cartilage wedges, not preceded by multinucleated giant cells (matrixclasts), invaded the implant. This fibrocartilaginous response to an exogenous inductor resembled the modified growth pattern of bone recently reported in magnesium-deficient rats.

Animals↗

PubMed2001

[Effect of experimentally induced trauma to the incisors in rats].

The purpose of this study was to produce developmental lesions of enamel in rats by a quick and simple method and to examine the enamel hypoplasia caused by trauma. 4-day-old and 3-week-old Wistar rats were used. Trauma was produced by needle pricking and hitting on the mandibula. After one week incisors were removed together with jaws and prepared for microradiography, X-ray diffraction, light microscope and transmission electron microscope examination. Microradiographic findings in the needle pricking group revealed hypocalcified and hypoplastic enamel. The incidence was 73.7%. In the hitting group of 4-day-old rats the incidence was lower, 70.0%. Microradiographic findings in this group were diffuse hypoplasia in the surface enamel. Hitting of 3-week-old rats produced no enamel hypoplasia. Crystallinity of hypoplastic enamel was reduced in both a-axis and c-axis direction. Histological findings in 4-day-old rats revealed disarranged and detached ameloblasts at location trauma. These results indicate that a needle pricking method involving secretory stage ameloblasts of 4-day-old rat incisors can induce a considerable amount of enamel hypoplasia.

Ameloblasts↗