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PubMed1995

Confocal laser scanning microscopic studies on alveolar bone remodeling with orthodontic tooth movement and retention.

Alveolar bone reconstruction in growing dog during the retention period following orthodontic tooth movement was studied. Three beagle dogs (8-10 kg body weight, about one-year-old) were used and two of the animals were subjected to histological observation. The upper 2nd and lower 3rd premolars on both sides were extracted prior to the orthodontic treatments. After a healing period of one month, the upper 3rd premolar and the lower 4th premolar on the right side were moved mesially with a conventional orthodontic force for 8 weeks, and then retained in their new position for 4 weeks. The contralateral corresponding premolars were used as control. The alveolar bone was double-labeled with tetracycline (TC) during the movement and calcein (Cal) during the retention period. Alveolar bone structure and labeling patterns were examined by contact microradiography, conventional fluorescence microscopy, and confocal laser scanning microscopy (CLSM). Optimizing the separation of TC and Cal labelings in the alveolar bone was attained by the simultaneous use of ultraviolet (364 nm) and argon (488 nm) laser sources for excitation of TC and Cal, respectively. Cal labeling, indicative of new bone deposition showed two distinct patterns: lamination at the periodontal surface and rings circumscribing the vascular canal. The cementum surface also exhibited active deposition during the experimental period. Bone formation was affected by slight changes in magnitude and direction of orthodontic or occlusal forces. CLSM is valuable in deciphering the process of alveolar bone remodeling.

Alveolar Process↗

PubMedDate not supplied

In vitro studies of the effect of a dental explorer on the formation of an artificial carious lesion.

This project deals with in vitro mechanical damage of early carious lesion (enamel lesion) in artificial U-shaped grooves caused by a sharp dental explorer. The lesions were formed in enamel grooves in 3 percent by weight cellulose solution in 0.1 M lactic acid containing 1.08 M KH2PO4 and 1.8 mM CaCl2 buffer to pH 4.28 after two weeks of demineralization. A relatively intact surface layer was observed in all the grooves. Three demineralized grooves were probed with different forces 100 g, 300 g and 500 g. The traumatic damage was assessed by using microradiography. There was no damaging effect in the sound enamel grooves probed with a sharp explorer up to a force of 500 g. Breakdown of the surface layer was assessed in all probed demineralized enamel grooves, converting the white spot lesion with apparently a sound surface layer into a cavity. Explorer penetration into the lesion was found to be strongly related to the force applied. The use of a sharp dental explorer should be reconsidered in examination and diagnosis of early carious lesions in pits and fissures and an alternative technique should be sought.

Dental Caries↗

PubMedDate not supplied

Histomorphometric evaluation and pathogenesis of prosthetic loosening.

On the basis of a vast experience deriving from the histological study of explants of hip joint prostheses, the authors emphasize the role of histomorphometric testing in allowing for a quantitative evaluation of periprosthetic cellular reaction, of the bone structure, and of the wear phenomena of the implant, in order to gain a better understanding of the pathogenetic mechanisms responsible for the phenomenon of loosening. In agreement with what has been reported by other authors, they describe what they were able to observe by image analysis, microradiography, x-ray diffraction, and microdurimetry in various types of explanted prostheses. In particular, they describe data on the features of the wear particles, the periprosthetic cellular component, the thickness of the interfacial membrane and of the joint neocapsule, the volume of bone-ingrowth, the contact surface, and the structure of the bone-implant interface. Based on the changes observed using histomorphometry, a pathogenetic hypothesis was formulated according to which physical phenomena closely related to the type of implant used, such as wear and metal ion release, and non-physiological stress exerted on the bone, cause a series of cellular chain reactions. Within this context, macrophages, lymphocytes, osteoblasts and osteoclasts are in a continuous state of activation and, both directly and by means of the production of cytokines and other substances, they are responsible for bone resorption and thus loss of continuity between the bone and the implant, resulting in prosthetic loosening.

Hip Prosthesis↗

PubMed1976

[Osteolathyrism. Quantitative-morphological studies on the experimental rat skeletal disease].

In young growing rats, fed the lathyrogenic agent aminoacetonitrile for 3 weeks, characteristic skeletal changes developed resembling the chronic state of osteolathyrism. In both lathyritic and untreated control rats, the femoral head, the distal end of the femur, the proximal tibial end, the thalocalcanean joint and the first lumbar vertebra were investigated using undecalcified thin sections and ground sections. The following methods were employed: quantitative morphometrical analysis of bone structure and bone remodelling of the lumbar vertebra, histochemical demonstration of the composition of polysaccharides, detection of the course of collagenous fibres in cartilage and bone by the polarizing microscope, tetracycline-labelling and fluorescence microscopical determination of epiphyseal longitudinal growth and bone formation activity, photometrical quantification of microradiographies and computer-aided determination of the mineral content of bone.

Aminoacetonitrile↗

PubMed1994

Evaluation of biocompatible osteoconductive polymer shelf arthroplasty for the surgical correction of hip dysplasia in normal dogs.

Biocompatible osteoconductive polymer (BOP) shelf arthroplasty was performed on ten nondysplastic dogs, divided into five groups. Each group was evaluated at 6, 13, 17, 26 or 39 weeks postsurgery. Evaluation consisted of clinical, radiological and histological studies. The dogs were injected with three fluorochrome markers, 28 days, 14 days and 6 hours before euthanasia. Transverse sections of undecalcified arthroplasty site were examined by microradiography and fluorescence microscopy; surface-stained sections were evaluated by light microscopy. The BOP shelf arthroplasty was not technically difficult. Minimal mineralization of the shelf was noted by radiography, 26 and 39 weeks postop. A moderate to large amount of fibrous mature connective tissue was observed around the BOP fibers throughout the study. Bone ingrowth occurred around the BOP fibers, but was minimal within them. This osseous proliferation of the arthroplasty was very slow to take place; it was first noted microscopically 17 weeks postsurgery and was still minimal 39 weeks after surgery. These findings suggest that there may be interference to the osteoconductive properties of BOP by fibrous tissue. Ossification of the shelf arthroplasty was too unsatisfactory to recommend its use for the treatment of canine hip dysplasia.

Animals↗

PubMed1994

[Bone healing after unreamed intramedullary nailing].

Good clinical results of unreamed nailing have been observed primarily in cases of open fracture. However, it is still unclear whether unreamed nailing is a suitable procedure for fractures that have previously been treated with reamed nailing. Since histological findings on bone healing after unreamed nailing were not available, an animal experiment on sheep was undertaken. The aim was to investigate whether there were differences in the nature of bone healing following reamed and unreamed nailing procedures. Fluorescence microscopy clearly showed that maximal callus formation occurred within 4 weeks after unreamed nailing and within 6 weeks after reamed nailing. Callus formation was also more prolific after unreamed than after reamed nailing. It was demonstrated by microradiography that bone regeneration progressed more rapidly, in terms of both periosteal and interfragmentary callus, after unreamed nailing. No disturbances of bone healing and no greater risk of pseudarthrosis were observed following unreamed nailing. Histological investigations showed that bone healing was faster after unreamed nailing and there was a reduced loss of vitality. This is of particular clinical relevance in the surgical treatment of fractures with severe soft tissue injury and of open and comminuted fractures. These results indicate that an extension of the indications for unreamed nailing should be considered.

Animals↗

PubMed1994

Temporal bone dynamics, the hard way. Formation, growth, modeling, repair and quantum type bone remodeling in the otic capsule.

This review presents studies in which temporal bone dynamics were monitored in undecalcified human and animal materials by combined microradiography and osteofluorochromic time labeling. The results are interpreted in accordance with modern concepts of spatial and temporal organization of bone behavior in an attempt to contribute to a new basis for understanding the structure and function of the bony otic capsule. In postcartilaginous development, perilabyrinthine bone formed a separate functional unit in which growth and modeling were absent. Consequently, all drift movements bypassed the bone present inside a narrow perilabyrinthine zone, which in effect maintained a so-called drift barrier enclosing the entire inner ear. In baseline bone remodeling and repair-associated remodeling transients, secondary osteons were distributed centrifugally with respect to inner ear spaces, and the average osteonal size decreased towards the inner ear, suggesting a progressive inhibition of bone resorption towards inner ear spaces. No histological capsular component proved resistant to bone resorption during modeling and remodeling. Instead the dynamic behaviour of any moiety of capsular bone appeared to depend on its spatial relation to the membranous labyrinth rather than on histological characteristics. This spatial organization of perilabyrinthine bone development and turnover is responsible for the unique histology of capsular bone and may explain the accumulation of fatigue micro-cracks which can be found in human perila byrinthine bone. These findings suggests the role of inner ear tissues as a functional matrix in control of capsular bone dynamics even beyond fetal life.

Animals↗

PubMed1993

Inhibition of enzymes by short-wave optical radiation and its effect on the retina.

UNLABELLED: INTRODUCTION AND HYPOTHESES: Exposure to short-wave optical radiation is a potential hazard for vision. In the present study, blue-light damage is studied in rat retina. It was hypothesized that the absorption of blue light by cytochrome oxidase in rat retina inhibits this enzyme, and may reduce the retinal oxidative metabolism. Irreversible inhibition of the oxidative metabolism may decrease the activity of the Na/K-ATPase, hence redistribute ions, increase intracellular osmotic pressure and cause cellular edema. Severe retinal edema may be the cause of retinal degeneration. METHODS: A quantitative histochemical method, a combination of histochemical staining and densitometrical measurement, was established to measure the activity of cytochrome oxidase. The distribution of chlorine and potassium in rat retina was estimated with a nuclear microprobe. Microradiography was adopted for measuring the protein and lipid density, which is an indirect estimation of retinal edema and retinal refractive index. The damage to the photoreceptor cells was estimated from the thickness of the outer nuclear layer. RESULTS AND CONCLUSIONS: Blue light inhibited cytochrome oxidase at a retinal dose of about 110 kJ/m2. This inhibition was reversible, and is probably related to the light regulation of retinal metabolism. At a retinal dose of about 380 kJ/m2, the inhibition of cytochrome oxidase was followed consecutively by a probable redistribution of chlorine and potassium in the inner and outer segments, damage to the mitochondria in the inner segments, edema in the inner and outer segments, and progressive degeneration of photoreceptor cells. Dark adaptation did not increase the blue-light retinal injury. These findings support the hypothesis that inhibition of cytochrome oxidase is one of the causes of blue-light retinal damage. The alteration of enzyme kinetics after in vitro exposure to short-wave optical radiation was estimated using lactate dehydrogenase as a model. The ultraviolet-radiation exposure inhibited lactate dehydrogenase with a significant decrease in maximal velocity, while Michaelis constant remained unchanged.

Animals↗

PubMed1977

The effect of fixation with intramedullary rods and plates on fracture-site blood flow and bone remodeling in dogs.

Of fifty-seven adult dogs in which standard bilateral mid-ulnar fractures were produced, thirty-four had one side fixed with either a tight-fitting intramedullary Steinmann pin or a four-hole plate while the other side was not fixed, and twenty-three had a plate on one side and an intramedullary rod on the other. The blood flow at the fracture site, as determined by 85Sr clearance, was significantly less on the rod-fixed side than on the plate-fixed side at fourteen and ninety days, while the total ulnar blood flow was significantly higher on the rod-fixed than on the platefixed side at one and fourteen days but was the same on both sides thereafter. When the plate-fixed and rod-fixed fracture sites in the same dog were compared with respect to periosteal and endosteal bone formation as determined by tetracycline labeling anc microradiography, bone formation, like the blood flow, was greater in the callus of the ulnae fixed by plates. However, at ninety days, when healing had advanced to a point when the extent of union could be judged clinically, union had occurred in both ulnae of six of the seven dogs with both types of fixation studied at this time and was delayed in both ulnae of the remaining dog.

Animals↗

PubMed1995

High-resolution electron microscopic study of salivary calculus.

The present study was performed to examine crystals in salivary calculus by high-resolution electron microscopy (HREM) and electron diffraction analyses. Microradiography (MR) showed that the calculus had three nuclei and showed complex shapes and mineralization. Hydroxyapatite (HA), in a variety of sizes and distributions, and the intermingling of HA and whitlockite (WH) at well-calcified areas, were observed.

Calcium Phosphates↗

PubMed1995

The structural patterns and mineralization values of prismless enamel, a case of mild enamel hypoplasia.

In examining the prismless enamel (PL) distribution from the inner to surface layers of a human incisor with hypoplastic perikymatas with enamel pits, we determined the structural patterns and mineralization values by microradiographic, optical, and scanning electron microscopic observations. The PL containing abnormal prisms ranged from 20 to 250 micrometers in thickness. The alternated layers of the PL and prismatic enamel, in parallel with the Retzius lines, showed a roughly zigzag pattern based on the main orientation of enamel crystals. Such a pattern suggests an alternation of the disappearance and reappearance of Tomes' processes, which may have strong restorative and reactive capacities. In the mineralization values determined by microradiography, the PL was higher in the well-marked lines of Retzius, while the PL under the hypoplastic enamel pit and an area within the thick PL showed hypomineralization. The backscattered electron images indicated that the fine laminate striations and abnormal prismatic rows within the PL were hypomineralized, and the PL in the inner enamel showed a lower mineralization than the adjacent prismatic layer. Thus, the disappearance of Tomes' processes, which form prismless structures, may be unrelated to changing the mineral amount in amelogenesis.

Ameloblasts↗

PubMed1995

Repair of bone defects with absorbable membranes. A study on rabbits.

Self-reinforced polyglycolic acid (SR-PGA) devices were developed in the mid-eighties, applied for fixation purposes and proved to be biocompatible. In this study SR-PGA membranes (10 x 10 mm) were used to augment defects on the medial aspect of distal femoral metaphysis in 31 New Zealand rabbits. Defects of 3.5 mm were either filled with autografts or left non-grafted. In a control group, no membranes were used. The rabbits were followed up for six, 12 and 24 weeks. Radiography, histology, oxytetracycline (OTC) fluorescence labelling and microradiography were used. Defects where membranes were used, healed by new bone formation. In some cases where polyglycolic acid (PGA) membranes were not used, defects were invaded by fibrous tissue. Membranes sometimes slipped away from their positions opposite to grafted defects. This study proved that the advantage of the use of PGA membranes could be taken in augmentation of cancellous bone defects in rabbits.

Absorption↗

PubMed1996

Experimental osteochondritis dissecans--the role of cartilage canals in chondral fractures of young rabbits.

Skeletal immature rabbits were used to study the pathogenesis of Osteochondritis Dissecans (OCD). Both histological studies and a radiographical examination were utilized after sagittal and coronal surgical chondral fractures were made in the femoral condyles cartilage. Serial microangiographies were performed in rabbits between 0 and 84 days after the chondral fractures were made. Analyses of the histology and microradiography findings suggest in either a coronal or sagittal direction, that avascular lesions like an experimental OCD occur as a sequence of chondral injury. A fracture in a wide pedicle of a stable cartilaginous flap with abundant cartilage canals heals in the usual way. However, a fracture in an unstable fragment with a small isthmus devoid of cartilage canals and of nutritious vessels, probably doesn't heal completely and a fragment closely resembling OCD is instead formed. An experimental OCD depends on the slender hinge of the flap and on the lack of stability in a rabbit's non-ossified epiphyseal cartilage. The damage to the cartilage canals and the rupture of vessels in the canals by a chondral fracture and the disturbance in the revascularization in the healing process by abnormal mechanical forces are thus most likely considered to be the main factor for OCD production.

Animals↗

PubMed1977

The effects of zinc deprivation on the host response to intramuscular bone matrix implants in the rat.

Sterile sequentially extracted insoluble bone matrix gelatin and freeze-dried allogeneic demineralized whole bone matrix was implanted into a lumbar muscle pouch of 12 Sprague-Dawley rats fed a diet containing 0.9 ppm zinc and into 6 rats fed a diet containing 50 ppm zinc. Histological sections and microradiography demonstrated that skeletal tissue induction occurred in all instances. In the zinc-supplemented hosts, four weeks postimplantation, trabecular bone and bone marrow grew on both sides of the matrix implant which had been almost completely resorbed by matrixclast activity. However, in the zinc-deficient hosts, the central cavity of the matrix was first filled with mesenchyme and then cartilage cells which grew in the form of thin wedges into the implanted matrix. Poor vascularization appears to be an important factor in cell proliferation and abnormal differentiation in zinc deficiency.

Animals↗

PubMed1996

[Vascularization of the wall of the superficial veins. Anatomic study of the vasa vasorum].

INTRODUCTION: The blood vessel wall is almost always nourished by two ways; from the blood stream itself and through the outer part of the wall by vasa vasorum. AIM OF THE STUDY: The aim of this study was to demonstrate that this kind of nutrition is also available for the venous wall and to define the distribution pattern in superficial venous walls. MATERIALS AND METHODS: 50 long saphenous veins and 20 short saphenous veins latex or barium injections, dissections with magnifying glasses and microradiographies. Topographical evaluation of the origin of vasa vasorum. RESULTS: The results showed that vasa vasorum originated from perforating arteries coming from several levels and getting a lot of anastomosis. We showed that the main sources for the long saphenous vein are the external pudendal artery and descending artery of the knee and for the short saphenous vein, the short saphenous vein artery. In thrombosis and varicose veins, the vasa were strongly altered. CONCLUSION: This study outlines the fact that superficial veins are supplied by arterial and venous vasa vasorum, and the role of vasa vasorum must be considered when questioning the pathogenesis of varicose and post thrombotic disease.

Arteriovenous Anastomosis↗

PubMed1997

Pregnancy-associated changes in material properties of the third metacarpal cortical bone in mares.

OBJECTIVE: To investigate the effect of late gestation, age, and parity on material properties of third metacarpal (MCIII) cortical bone in mares. ANIMALS: 8 healthy mares (treatment group) that died or were euthanatized within 24 hours after parturition because of foaling complications and 6 age-matched, healthy, nonpregnant mares (control group). PROCEDURES: After random assignment for mechanical testing and microradiography, the dorsal half of transverse mid-diaphyseal sections of each MCIII bone was divided into lateral, dorsal, and medial regions. Cylinders of bone from each of the 3 regions were tested in compression in a single cycle to failure. Contact microradiographic views were taken of 100-microns-thick sections prepared from methylmethacrylate-embedded transverse dorsal region specimens, which were further divided into periosteal, intracortical, and endosteal regions for assessment of bone mineral density and porosity. RESULTS: Postpartum mares had lower yield strain in the dorsal and medial regions and failure strain in the medial region. Increasing parity was associated with decreasing elastic modulus in the dorsal region and yield stress and failure stress in the lateral region. Age and parity were positively correlated (r = 0.865; P = 0.0001), but significant correlations were not found between treatment group and age or between treatment group and parity. Increasing age and parity were associated with increasing porosity in the periosteal region. CONCLUSIONS AND CLINICAL RELEVANCE: On the basis of the material properties evaluated for MCIII cortical bone in late pregnancy, any increased risk for fractures in mares in late gestation may be related to parity or age or both, and less likely to pregnancy pese.

Aging↗

PubMed1996

[A comparative morphometric and histologic study of five bone substitute materials].

OBJECTIVE: To investigate and compare the osteogenesis of bone substitute materials. METHODS: 52 Chbb: ch rabbits were divided into 5 groups. Five different porous biomaterials, including natural bovine hydroxyapatite (Bio-OSS, BK V/1), semi-synthetic coral hydroxyapatite interpore 500, synthetic tricalcium phosphate CEROS 82 and glass POROLITH, were implanted together with free periosteum into the muscle of rabbits for up to 3 and 6 weeks. Undecalcified sections were prepared for microradiography, light and UV microscopy, and morphometry. RESULTS: Bone ingrowth was present in all such implantats. Bone formation was limited to the periphery of the Ceros blocks, that are lack of pore interconnection, while the other 4 materials with an interconnected porous system were infiltrated by bone into the centrum. Planimetric analyses showed that the specimens were composed of 6.5%-19.0% new bone at the 3rd week and 14.2%-25% at the 6th week respectively. The difference of bone ingrowth was only significant between Bio-OSS and BK V/1 at the 3rd week. No statistically significant difference of bone volume was found within the 6 week groups. There was a positive correlation between the new bone volume and the porosity of the materials. CONCLUSION: For the bone ingrowth, the structure of the materials, specifically the pore and pore interconnections, is more impatant than the chemical composition.

Animals↗

PubMedDate not supplied

Scheuermann's kyphosis: a form of osteoporosis?

A high frequency of abnormalities were noted in radiographic measurements of bone density, microradiography of the iliac crest, serum alkaline phosphatase, urinary hydroxyproline and dietary calcium intake in 12 patients with Scheuermann's juvenile kyphosis. Scheuermann's kyphosis may be a manifestation of generalized skeletal disease which becomes symptomatic during the growth spurt of puberty.

Adolescent↗