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PubMed1989

[An experimental study on the osteoconductive properties of porous calcium phosphate glass ceramics].

Porous blocks of calcium phosphate glass ceramics (CaO 52 mol %, P2O5 47 mol %, Al2O3 1 mol %, mean pore size 200 microns, mean porosity 85%) were implanted in the distal femoral metaphysis of rats and were observed for up to one year. The materials were evaluated histologically and morphometrically using contact microradiography and Masson-Goldner staining. Comparative experiments were conducted employing similar methods as described above, with calcium phosphate glass ceramics, sintered hydroxyapatite and alumina ceramics, each having 70% porosity. The compressive strength of each implanted material was measured at a certain intervals up to 6 months after implantation. Bone formation was seen from the periphery to the center of the block. Mass of the regenerated bone and infiltrating depth of the new bone increased with the passage of time. New bone formation with the glass ceramics was observed to be almost equivalent to that obtained with hydroxyapatite, and was significantly higher than that with the alumina ceramics.

Animals↗

PubMed1989

Multiple bone islands in a skeleton dating from the Neolithic period.

Multiple bone islands were observed in a skeleton dating from the Neolithic period (two in a femoral head, two in the lower epiphysis of a femur, one in a humeral head). Macroscopic and radiographical examination was complemented by microradiography in the femoral head.

Bone Diseases↗

PubMed1989

[Ultrastructural changes in rat-incisor dentinogenic cells after administration of 5-fluorouracil].

Single intraperitoneal injections (180 mg/kg) of 5-fluorouracil (5-FU) were administered to male Wistar rats weighing 100 g each. After 1, 2, 3, 4, 5, 7, 10 and 21 days, the animals were fixed by perfusion with a mixture of 2.5% glutaraldehyde and 2.0% paraformaldehyde. The maxillary incisors were dissected out; and optical-microscopy, microradiography, and transmission electron-microscopy were made of changes occurring in the dental-papilla cells, odontoblasts, and dentin matrix. 1. One day after the 5-FU injection, considerable amount of damage had occurred in the basal portion of the incisor forming a large void in the dental-papilla (cell-free region) immediately below the inner enamel epithelium. But, 4 days after the injection, the cell-free region was filled again with numerous newly regenerated dental-papilla cells (reparative region). Thereafter these cells differentiated as regular odontoblasts. 2. In 1 day after the injection, dental-papilla cells that had begun differentiating into odontoblasts degenerated and atrophied (degeneration region). Round cells appeared on the pulp sides of degenerated and atrophied odontoblasts 3 days after the injection. These cells increased in both size and number and formed a hard tissue in which the degenerated odontoblasts had embedded. The matrix of the newly forming hard tissue was composed of closely arranged collagen fibrils. Matrix vesicles were observed in the initial stage of its mineralization. Dentin had deposited on the pulp side of this hard tissue 21 days after the injection. 3. Dentin formation in the reparative region began 7 days after the injection; and, by the twenty-first day, ordinary dentin thickness had been attained. In the degeneration region, however, a little dentin was formed. In contrast, on both sides of the degeneration region, dentin formed in a virtually normal fashion and grew thicker with the passing of time, creating a deep, bowl-shaped concavity in the degeneration region.

Animals↗

PubMed1989

[Ultrastructural changes in rat-incisor odontoblasts and dentin caused by administration of sodium fluoride].

Subcutaneous injections of 8.4 mg of sodium fluoride were administered to young male Wistar rats weighing 100 g each. After 1, 3, 6, 12, and 24 hours and then after 2 and 4 days, the rats were fixed by perfusion; and their upper incisors were subjected to optical microscopy, microradiography, and electron microscopy. In some instances, 0.1% ruthenium red (RR) was added to the fixing or demineralizing solution for the sake of observing acid-mucopolysaccharide distribution. 1. The following changes were observed in odontoblasts: swelling of the rough endoplasmic reticulum, vacuole formation, increased numbers of autophagic vacuoles and Golgi vacuoles, and abnormal accumulation of cytosome-4. All of these changes tended to have recovered by 24 hours after administration. 2. In the predentin, abnormal increases in amounts of amorphous substance occurred 1 hour after and continued until 12 hours after administration. Thereafter, increases gradually retarded; and the level observed in controls was restored by the fourth day after administration. RR staining showed this amorphous substance to contain large amounts of acid mucopolysaccharides. 3. Two types of abnormal collagen--segmental collagen aggregate (SCA) and fibrous long-spacing collagen (FLS)--were observed in the amorphous substance mentioned in the preceding paragraphy. In longitudinal sections, SCAs were 320 nm long and 200 nm wide; symmetrically arranged striations were visible within them. FLSs were observed as long, thick fibrils with periodic striations of about 160 nm. With the passing of time, these abnormal collagen aggregates and fibrils shifted from the distal end of the odontoblast toward the dentin, in which they became embedded. 4. Mineralization in the abnormal collagen commenced with deposition of needle-shaped or thin platelike crystals. As time passed, the collagen came to be completely covered with the crystals. Loosening of collagen molecular binding seems to occur following advances in mineralization and crystal growth. 5. Abnormality in dentin mineralization resulted in the formation of a hypermineralized layer and a hypomineralized layer beneath the hypermineralized layer. The hypermineralized layer contained densely distributed crystals. Its boundary with the hypomineralized was clearly observable. The boundary with teh regular dentin, however, was shifting and indistinct.

Animals↗

PubMed1989

[Experimental studies on augmentation of the mandibular region with proplast and lyophilized homogenous cartilage].

Proplast I, Proplast II and freeze-dried homogenous cartilage (1 x 2 x 5 mm) were implanted under and over the rabbit mandibular periosteum. Histological observations and contact microradiography (CMR) were performed to investigate the healing process in the surgical sites from 1 to 24 weeks after the operation. In addition, microangiography (MA) was carried out to investigate changes of vascularization in the groups in which Proplast implants were made. Results 1. Proplast implantation group 1) In the supraperiosteal placement group, CMR revealed no new bone formation around or inside the Proplast and no morphological changes of the host bone in contact with the Proplast. In the subperiosteal placement group, from the early postoperative stage, new bone formation occurred from the host bone beside the Proplast. New bone penetrated the Proplast from the new bone region and from the host bone in contact with the Proplast. In 6 months after the operation, Almost all Proplast pores were filled with new bone. From a comparatively early postoperative stage, resorption fossae appeared in the host bone surface. In addition, Haversian canals inside the host bone enlarged and the host bone cortex gradually grew thinner. No differences in new bone volume or host bone changes were noticed between the Proplast I and Proplast II groups. 2) In the supraperiosteal placement group, granulation tissue proliferation with slight round cell infiltration was observed around and inside the Proplast at an early stage. In 2 weeks after the operation, blood clots disappeared from the Proplast, in the center of which granulation tissue proliferated. Thereafter, granulation tissue was gradually transformed into fibrous tissue, although no new bone was observed in any region. Change almost never occurred in the host bone cortex, but slight swelling occurred in the periosteum in contact with the Proplast after 1 week. 3) In the subperiosteal placement group, swelling and slight round cell infiltration were observed in the periosteum covering the Proplast at an early postoperative stage. But, after 4 months, the periosteum had returned to normal condition. Beside and inside the Proplast, rapid granulation tissue proliferation and new bone formation were observed. New bone formation was observed beside the host bone, but not beside the periosteum. For a comparatively long time, resorbed fossae in the host bone surface and enlarged Haversian canals persisted. Host bone width gradually decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

Alveolar Ridge Augmentation↗

PubMed1979

[Variations of the etching patterns of enamel surfaces after treatment with various caustics].

Conditioning the enamel is extremely important for the prophylactic treatment of caries with sealers. The possibility of dentition depends on the depth and pattern of etching. Incisors and molars were etched with seven etching agents. The depth of etching was examined via microradiography; the etching pattern, with the scanning electron microscope. The best etching agent proved to be a 50% solution of H3PO4 + 2% solution of NaF; The depth of etching was greater in the molars than in the incisors. The etching pattern produced with this agent was also the most even. The etching pattern could not be predicted on the basis of the etching agent.

Dental Caries↗

PubMedDate not supplied

The vascular morphometry of some brain stem parts.

With the view of following the vascular system of the cerebral trunk, there have been simultaneously injected coloured tracers combined with radio-opaque substances and radio-isotopes (32P, 22Ca) by intravital perfusion to 130 animals (dogs, rabbits and rats). The macro- and microscopical vasculature of the human brain stem was studied on 30 specimens of adults and children. The angioarchitecture of the diverse parts and sectors of the brain stem was studied as a whole in tetraline transparentised preparations and on histological section in comparison with the microradiographies and to incorporation of radioisotopes. A particular attention has been given to the irrigation of hypoglossal nuclei, the bulbar oliva, and the pontopeduncular region, all being zones with multiple sources of vascularization. The vascular morphometry has been macro- and microscopically performed, the data being worked out mathematically-statistically by computing some hemodynamical indices in order to estimate the circulation in different zones of the brain stem.

Adult↗

PubMed1985

[Experimental research on the preparation of dentin-pulp tissue of teeth exposed to CO2 laser beams in dogs and macaques (Macaca mulatta and Macaca fascicularis].

Traumatic inflammation due to application of CO2 laser radiation (lambda = 10.6 microns) on the dentin and on pulp of 342 teeth of 8 dogs (Beagle) and of 6 monkeys (Macaca sp. mulatta et fascicularis) stimulate in dentino-pulpal tissue morphological phenomenon, studied after 5 days, 1 and 3 months by microscopy and microradiography. The dentin exposed to a density of energy of: 2 X 10(3) J/cm2 shows a burn, a rarefaction and a cellular degeneration, followed by a neoformation of calcified dentin, of about 300 microns thick in 3 months, due to the excitation of odontoblasts or produced by pulpal cells functioning before. A density of energy of 10(3) J/cm2 order applied to the pulp beads to its partial necrosis, to various inflammatory aspects (vascular, cellular, tissular) and to a quasi-constant regeneration of by a neo-dentin bridge of 200 micron at 1 month. This method seems able to allow the analysis of cell activity (start, activation, blocking).

Animals↗

PubMed1987

Fixation of experimental osteotomy of the distal femur with biodegradable thread in rabbits.

A distal femoral osteotomy on 24 rabbits was fixed with biodegradable polyglycolic acid (PGA) thread pulled through drill holes made on both sides of the osteotomy. Follow-up times were one, three, six, 12 and 24 weeks. The distal part of each femur was removed, fixed in alcohol, embedded in methylmethacrylate, sawed to 80 microns thick for oxytetracycline (OTC)-labeling studies and microradiography, and sectioned at 5 microns for histologic studies. As judged by histologic microradiographic, and OTC-labeling studies, 19 of 24 osteotomies were healing normally; after six weeks of follow-up examination, union of 11 of 14 osteotomies was observed on radiographs. On the basis of the present study, PGA threads may be promising for the fixation of osteotomies of the metaphyseal cancellous bone in rabbits.

Animals↗

PubMed1977

IgE myeloma with osteoblastic lesions.

A 69-yr-old man with persistent anemia had multiple myeloma with an IgE-type kappa M component and Bence Jones proteinuria. Bone x-rays revealed occasional lytic lesions associated with a diffuse sclerotic reaction throughout the skeleton. Special bone histologic studies utilizing tetracycline labeling, undercalcified sections, and microradiography confirmed active osteoblastic activity. This case was compared with the four previously reported cases of IgE myeloma, one of which also had osteosclerosis.

Aged↗

PubMed1977

Reaction of bone to the acute chemical trauma of bone cement.

The acute chemical trauma of bone cement was investigated in the rabbit tibia. With the experimental model used, the surgical trauma and the thermal effects of the cement could be minimized. Each animal received one implant of polymerized cement as a control and one implant of polymerizing dough as the test material. The animals were observed for up to seventy days and the specimens were then studied by various techniques of histology, microangiography, fluorochrome labeling, and microradiography. With this experimental method the monomer trauma did not add to the minimized surgical trauma. Moreover, no detectable influence on bone regeneration was noted. In view of this minor effect, we suggest that the surgical preparation of the implant bed and the very procedure of inserting bone cement are more important for the acute tissue trauma than is monomer leakage alone.

Animals↗

PubMed1988

[Caries preventive effectiveness of Fluor Protector and fluoride lacquer, Duraphat under very cariogenic conditions].

Fluoride varnishes Durpahat and Fluor Protector are commonly used and have proven to be effective as caries preventive agents. In the first part of this paper the features of fluoride varnishes in terms of fluoride uptake, caries prevention and toxicological safety are discussed. The effect of both varnishes under high cariogenic conditions is discussed in the second part. In the presented study, 8 patients carried 3 enamel specimens (Fluor Protector, Duraphat, Control) intra-orally during 4 months. They kept plaque accumulation intact on the specimen and avoided fluoride administration from other sources. After 4 months of substantial cariogenic challenge, the enamel was analysed by microradiography and the degree of caries protection obtained for each varnish type was calculated. The results show that under high-risk caries conditions enamel treated with Fluor Protector was significantly better protected (65%) than enamel treated with Duraphat (3%).

Dental Caries↗

PubMed1988

The granular layer of Tomes in experimental caries in rats.

In examination of ground sections of human third maxillary molar teeth, the granular layer of Tomes was shown to consist of expansion of dentinal tubules. The microradiographic density was decreased well inside the layer. It was postulated that the findings were expressions of dentin resorption. The theory was tested experimentally in rats fed a cariogenic diet with low calcium and phosphorus. The morphology of mandibular molar teeth was studied by electron probe microanalysis and by microradiography. It was concluded that the primary event in cariogenesis was an expansion of peripheral dentinal tubules with formation of confluent microcavities and, thus, an unmasking of the granular layer of Tomes, which normally is only potential. A subsequent loss of mineral density in the outer enamel eventually caused breakdown of the outer enamel with caries visible from the surface. The loss of density within the enamel was postulated to result from interruption of the normal flux of nutrients, metabolites and ions between the dentin and enamel. Whereas an increase in dietary calcium and phosphorus delayed and reduced significantly, but did not prevent cariogenesis, it supported the theory that experimental caries in rats is a metabolic disease with the peripheral dentin the primary target.

Adult↗

PubMed1988

Changes in quality of bone mineral on aging and in disease.

This paper reviews the changes in the quality of bone mineral with age and in disease. After a brief review of morphological changes with aging in mammalian bones, microradiography is compared to backscattered electron imaging and their use in bringing out subtle changes in bone mineralization outlined. Changes in the quality of bone with disease is described using osteoporosis as an example. Chemical changes in the skeleton are then discussed and related to morphological changes. Finally, some examples of localized and generalized changes in bone mineral are given. This paper emphasizes that understanding the nature of the mineral phase in bone as well as its heterogeneity and its changes with age and in disease is essential to the elucidation of skeletal physiology and pathology.

Adult↗

PubMed1988

Bonding behavior of three types of hydroxyapatite with different sintering temperatures implanted in bone.

The present study suggests that bonding does not vary in hydroxyapatite (HA) with different sintering temperatures implanted in bone tissue. The apparent unimportance of strict temperature regulation greatly simplifies HA processing. Three samples of HA (15 mm x 10 mm x 2 mm, abraded with 2000 alumina powder), of which sintering temperatures and microporosity were 800 degrees (45%), 1000 degrees (4.8%), and 1200 degrees (0.4%), respectively, were prepared. They were implanted into the metaphysis of tibia of mature male rabbits. Segments of the tibia containing the HA were excised and prepared for the detaching test. The failure load, when an implant detached from the bone or the bone broke, was then measured. Failure loads in HA (800 degrees), HA (1000 degrees), and HA (1200 degrees) ten weeks after implantation did not differ. Those in HA (800 degrees), HA (1000 degrees), and HA (1200 degrees) 25 weeks after implantation were 2.58 +/- 1.88 kg, 6.46 +/- 1.43 kg, and 6.50 +/- 2.71 kg, respectively. The failure load in HA (800 degrees) versus HA (1200 degrees) and that in HA (800 degrees) versus HA (1000 degrees) differed significantly (p less than 0.05). The lower failure load of HA (800 degrees) 25 weeks after implantation can be explained by its weakened mechanical strength due to high porosity. Bonding between bone tissue and three types of HA did not vary as observed by contact microradiography, Giemsa surface staining, and scanning electron microanalyzer-energy dispersive X-ray microanalyzer.

Animals↗

PubMed1987

Scanning microscopic observations on dental caries.

This paper presents findings made using special techniques of imaging and/or of specimen preparation to investigate the changes in tooth structure which occur in caries. We have studied both coronal and root caries in enamel, dentine and cementum using scanning electron and confocal scanning optical microscopy. In preparation for backscattered electron (BSE) imaging in the SEM, teeth were stored in 70% ethanol until further dehydration in ethanol and embedding in polymethylmethacrylate (PMMA). Longitudinally cut surfaces were diamond polished and coated with carbon or silver before BSE imaging. Important changes in the distribution of densities in both enamel and dentine occurred during caries, and could be correlated with prior published studies using polarised light and microradiography to study demineralization in these tissues. However, the resolution of the BSE imaging technique is much higher than that of these previous methods. A new method was used for demonstrating local variations in microhardness with special relevance to the changes occurring in dental caries. Sectioned surfaces were subjected to treatment with a jet of soft abrasive particles, resulting in the selective removal of carious enamel, and enhanced removal of carious dentine. The tandem scanning reflected light microscope (ISRLM) has also been shown to be useful in characterising the spread of caries in the dental tissues. Teeth only need to be cut once, because the image is formed on looking into a bulk specimen. Fluorescent dyes can be used to study the distribution of pore volume, making use of the high resolution in depth of this confocal microscope.

Dental Caries↗

PubMed1987

Artificially induced developmental defects in sheep enamel examined by scanning electron microscopy.

Upper incisor teeth from sheep infected with parasites or given 6 mg fluoride per kg bodyweight for 21 days during the period of tooth formation were examined with SEM and microradiography. It was found using both techniques that there had been a severe disturbance of the secretory ameloblasts leading to enamel hypoplasia. It is suggested that it is the severity rather than the cause of the insult to the ameloblasts which determines the degree of hypoplasia.

Ameloblasts↗

PubMed1987

Growth potential in onlay bone grafts: a comparison of vascularized and free calvarial bone and suture bone grafts.

Vascularized bone grafts are characterized by a viable cell population with osteogenic potential. These features suggest that continued growth can be anticipated following vascularized membranous bone transfer in a growing craniofacial skeleton. The present paper compares the potential for appositional bone growth in vascularized and free calvarial onlay bone grafts. In seven 8-week-old beagles, growth was assessed by direct caliper measurements of graft dimensions intraoperatively and 16 weeks postoperatively. Vascularized grafts demonstrated a 50 to 60 percent increase in size in all dimensions compared to 10 to 20 percent growth in free grafts (p less than 0.01). Microradiography revealed preservation of calvarial bony architecture and minimal resorption in vascularized grafts, while triple-fluorochrome labeling confirmed subperiosteal appositional bone formation. Free grafts were characterized by significant resorption and a delay in subperiosteal bone formation.

Animals↗