Phenomenon Of Calcification Research Articles

Studying the pathological and biochemical features in breast cancer progression by confocal Raman microspectral imaging of excised tissue samples.

Confocal Raman microspectral imaging (CRMI) has been used to detect the spectra-pathological features of ductal carcinoma in situ (DCIS) and lobular hyperplasia (LH) compared with the heathy (H) breast tissue. A total of 15-20 spectra were measured from healthy tissue, LH tissue, and DCIS tissue. One-way ANOVA and Tukey's honest significant difference (HSD) post hoc multiple tests were used to evaluate the peak intensity variations in all three tissue types. Besides that, linear discrimination analysis (LDA) algorithm was adopted in combination with principal component analysis (PCA) to classify the spectral features from tissues at different stages along the continuum to breast cancer. Moreover, by using the point-by-point scanning methodology, spectral datasets were obtained and reconstructed for further pathologic visualization by multivariate imaging methods, including K-mean clustering analysis (KCA) and PCA. Univariate imaging of individual Raman bands was also used to describe the differences in the distribution of specific molecular components in the scanning area. After a detailed spectral feature analysis from 800 to 1800cm-1 and 2800 to 3000cm-1 for all the three tissue types, the histopathological features were visualized based on the content and structural variations of lipids, proteins, phenylalanine, carotenoids and collagen, as well as the calcification phenomena. The results obtained not only allowed a detailed Raman spectroscopy-based understanding of the malignant transformation process of breast cancer, but also provided a solid spectral data support for developing Raman based breast cancer clinical diagnostic techniques.

Role of surrounding soils and pore water in calcium carbonate precipitation in railway tunnel drainage system

Abstract Calcium carbonate (CaCO3) precipitation in tunnel drainage system poses serious problems to railway tracks. In this study, the calcification phenomenon identified in Meyssiez tunnel was analyzed through laboratory testing and site water monitoring. In particular, the surrounding soils were investigated in the laboratory. Site water table was regularly monitored in the field and site water was taken for laboratory analyses in terms of pH and electrical conductivity (EC). Examination of the test results showed that the calcification phenomenon was mainly induced by the calcium carbonate dissolution in the fine fractions (d

Assessment of osteoblastic activity with 18F-sodium fluoride PET in aortic bioprosthesis structural valve dysfunction: First results of a monocentric observational pilot study

Structural valve degeneration (SVD) of bioprostheses is a common and serious complication in patients undergoing aortic valve replacement. SVD pathophysiology remains unclear.18F-sodium fluoride (NaF) and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) have respectively shown that an active metabolic phenomenon of calcification rather than an inflammatory process contribute to native aortic valve stenosis. We studied the respective value of NaF and FDG PET to explore the potential mechanisms involved in SVD. SVD patients underwent NaF PET to explore potential active calcification process, FDG PET to explore potential inflammatory process and thoracic CT. Tracer uptake was quantitatively measured by the bioprosthesis tissue-to-background ratio of standardized uptake values (TBR). Echocardiographic parameters, bioprosthesis calcium scoring on CT, and qualitative pattern of NaF and FDG activity on bioprostheses were analyzed. Twenty-one patients were included. Calcium score was higher in patients with significant NaF visual uptake versus patients without (1065 ± 505 vs. 462 ± 320, P = 0.015). The median NaF TBR (3.49, [2.33–5.04]) was significantly higher than FDG (1.34, [1.20–1.47]). Patients with NaF TBR greater than the median value had a higher calcium score (1059 ± 550 vs. 566 ± 363, P = 0.05), and showed a tendency to have more severe hemodynamic stenosis. Picture shows an example of patient with SVD (A); CT (B) established localizations of calcium deposits; NaF PET/CT (C) show intense uptake adjacent to calcifications; FDG PET/CT (D) show no uptake ( Fig. 1 ). These results suggest a link between SVD severity and active calcification activity and opens new perspectives on the assessment of SVD pathophysiology through NaF PET quantification of ongoing mineral burden.

Investigation of calcite precipitation in the drainage system of railway tunnels

Abstract Calcite precipitation causes clogging of barbicans and water gutters in drainage systems of railway tunnels, posing serious problems to railway tracks and subsequently to train circulation. In this paper, a number of tunnels, mostly in France, with calcite precipitation problems are identified. A first analysis of the problematic tunnels in France based on a geological map evidences the key role of the surroundings materials in the calcification phenomenon – it occurs in sedimentary rocks. For further analysis, an empirical index is defined allowing the tunnel calcification level (C-L) to be quantified and the main influencing factors to be analyzed. Results show that calcite precipitation depends not only on the hydraulic conductivity and CaCO3 content of surrounding rocks, but also on the nature of lining materials and the geometry of tunnels. As far as the potential mitigation solutions are concerned, removable geotextiles are proposed to be placed on the surface of gutters and replaced regularly. This new method is believed to be of high efficiency and low cost. It can be easily verified in the field conditions.

Association of matrix metalloproteinase 3 and endogenous inhibitors with inflammatory markers in mitral valve disease and calcification.

Calcific mitral valve stenosis (MVS) is a common disease characterized by extensive remodeling of the extracellular matrix via matrix metalloproteinases (MMPs). The mechanism of calcification due to extensive matrix remodeling remains unclear. In this study, we investigated the relationship between MMP-3, tissue inhibitors of metalloproteinases (TIMPs) as well as pro-inflammatory cytokines and the phenomenon of calcification in MVS. 212 patients having rheumatic mitral stenosis (RMS) and 155 healthy control subjects were recruited in the Cardiology Department of La Rabta Hospital University. Levels of MMP-3, TIMPs, IL-6 and TNF-α were measured by ELISA sandwich assay, hs-CRP was measured by immunoturbidimetry. Plasma levels of MMP-3, TIMP-1 and MMP-3/TIMP-2 ratio were lower only in RMS women in comparison to the control group. Calcification degree correlated positively with MMP-3 in women and men. In addition, calcification was correlated positively with MMP-3/TIMPs ratio in women patients. The inflammatory parameters were positively associated with extracellular matrix turnover biomarkers in men patients. In patients, the level of MMP-3 was increased in men and women with a calcification score ≥ 5. In addition, MMP-3 level predicted the occurrence of calcification. At ROC curves analysis, the cut-off MMP-3 level was in women was 9.21ng/ml (sensitivity 51.1%, specificity 89.3%) and in men was 12.84ng/ml (sensitivity 78.6%, specificity 77.8%). The high levels of MMP-3 and the biomarkers of inflammation contribute to valvular remodeling and calcification of the mitral valve.

Effet des médicaments de l’ostéoporose sur les maladies cardiovasculaires et effet des médicaments à visée cardiovasculaire sur l’ostéoporose

Osteoporosis and cardiovascular diseases are epidemiologically associated. Calcification phenomena of atherosclerotic plaque involve cytokines and growth factors also involved in bone remodeling. Drugs given for either of these two conditions could act on these mechanisms. Can osteoporosis drugs have an influence on the occurrence of cardiovascular events? Conversely, can the treatment of hypertension alter the course of osteoporosis? It is possible that administration of high doses of calcium (1g/day) in patients who already have important dietary intake can increase the risk of myocardial infarction. Epidemiological studies show links between low serum vitamin D levels and cardiovascular disease but interventional studies show that vitamin D administration in moderately deficient subjects vitamin D does not prevent the occurrence of cardiovascular events. Cohort studies show a beneficial effect of beta-blockers and thiazides administered to hypertensive patients: they reduce by 20% risk of fracture of the proximal femur. Should we focus on these anti-hypertensive treatments for our patients with osteoporosis?

Different mechanisms of bone formation of preosteoblast on metals in vitro

Different mechanisms of bone formation of preosteoblast on metals in vitro

CALCIFYING GASTRO-ESOPHAGEAL CARCINOMA: CASE REPORT AND REVIEW OF LITERATURE

A 70 year old female presented with dysphagia of 6 months duration. Upper GI endoscopy showed a proliferative growth in mid esophagus with occlusion of lumen. Biopsy showed adenocarcinoma of signet ring pattern. Contrast enhanced computer tomography of abdomen showed infiltrating tumor involving esophagus and entire stomach with calcification in lower esophagus and lesser curvature of stomach with ascites. Due to extensive nature of tumor and malignant ascites palliative chemotherapy with feeding jejunostomy was planned. Patient decline all treatment. This case report and review describes the rare phenomenon of calcification of stomach and esophagus.

A comparison of two types of preperitoneal mesh prostheses in stoma surgery: application to an animal model

The aim of this study is to compare the integration of two types of prostheses (high and low density, written as HD and LD, respectively) implanted around the stoma to reinforce the abdominal wall to prevent parastomal eventration. The surgical technique used for preperitoneal placement of the prostheses is also described. We performed terminal sigmoid colostomies on 16 porcine animals. In 8 of the animals, HD prostheses were placed around the stoma in preperitoneal position, while in the other 8, we implanted wide-pore LD prostheses using the same surgical technique. The following macroscopic variables were then measured: adhesion, extrusion, stenosis, and retraction. A morphological study was also carried out to evaluate the foreign body reaction and the formation of neovascularization and collagen. All animals were killed 3months after surgery. Differences were observed with regard to retraction (47±17.8% for HD vs. 55±19.4% for LD) and extrusion (50% for HD vs. 0% for LD). These differences did not reach statistical significance. There was a great amount of scarring for both types of prostheses, with stomal stenosis being observed in all cases. The number and consistency of intra-abdominal adhesions was low and similar for both types of prostheses. Neither eventration nor necrosis was observed for either type. With regard to the tissue response, we observed both fibrosis and calcification phenomena in the peristomal areas of the LD prostheses. In the HD group, there was both a lower scarring response and a higher foreign body response, with the areas of the prostheses remaining intact. Both types of prostheses are appropriate for preperitoneal placement in the experimental model used, leading to few intra-abdominal adhesions. Still, due to their integration characteristics, LD prostheses are more appropriate for implanting around the colon since they do not seem to lead to extrusions. When using prostheses, however, it is also essential to consider the important phenomenon of retraction, which is more common with LD mesh.

Calcium and the saga of the binders: accumulating controversy, or building consensus?

At the heart of the oral phosphate binder debate is whether, with the abandonment of aluminium as the main phosphate binder for dialysis patients and its substitution by calcium salts from the early 1980s, we have unleashed a ‘‘weapon of mass calcification’’ by engendering a positive ‘‘calcium balance’’ favouring extensive/progressive soft tissue calcification. More recently we have realized that the near endemic presence of calcium in the walls of blood vessels of chronic kidney disease patients cannot be viewed with either equanimity or passivity. The process of calcium deposition, in a crystalline structural form, is actively regulated. As such, of course, it has active promoters and inhibitors. Active players in the debate about this controversy include the manufacturers of non-calcium-containing phosphate binders, for whom making a convincing scientific and pharmaco-economic case for a potentially expensive change in prescribing practice has a high priority [1]. The most obvious, and worrying, manifestation of this soft-tissue calcification phenomenon is vascular calcification, with its potentially disastrous trio of cardiovascular complications: coronary artery disease, peripheral vascular disease, and arteriosclerosis [2]. The opening skirmishes in this conflict took place over a decade ago. Braun and his colleagues from Erlangen–Nurnberg [3] conducted what was a technology assessment––to see how the ultra-fast electron-beam CT scanner could interrogate the vascular calcium load in dialysis patients. Forty-nine prevalent dialysis patients were chosen for study, and contrasted with 102 age-matched subjects with suspected or angiographically-proven coronary artery disease. What was shown, in the words of the abstract of the paper, was that ‘‘the coronary artery calcium score was from 2.5-fold to 5-fold higher in the dialysis patients than in the non-dialysis patients’’. A stepwise, multiple regression analysis confirmed the importance of age and hypertension. No correlation between calcium, phosphate, or parathyroid hormone values and the coronary calcium score was identified; however, the calcium score was inversely correlated with bone mass in the dialysis patients (r = 0.47, P \ 0.05). The mitral valve was calcified in 59% of dialysis patients, while the aortic valve was calcified in 55%. A repeat examination of the dialysis patients D. J. A. Goldsmith (&) Renal Unit, Guy’s Hospital, London SE1 9RT, UK e-mail: david.goldsmith@gstt.nhs.uk

Mönckeberg's sclerosis – is the artery the only target of calcification?

BackgroundSince its first description, Mönckeberg's sclerosis has only been related to arterial media calcification, being listed among the primary diseases of the vessels.Case presentationWe report here a clinically and histologically confirmed case of Mönckeberg's sclerosis in which the patient presented with massive areas of soft tissue calcifications in the pharynx and larynx. Polysomnographic parameters showed severe obstructive apnea refractory to nasal continuous positive airway pressure. Clinical and laboratory findings excluded concomitant endocrine or rheumatological diseases.ConclusionOur data provide a new insight about Mönckeberg's sclerosis, i.e., the fact that the etiopathogenic process involved in the phenomenon of calcification may not be restricted only to the arteries, but may occur in the entire organism. Further studies of the etiopathogenesis of this disease are needed.

Calcium deposition and expression of bone modelling markers in the tympanic membrane following acute otitis media

In accordance with clinical findings, myringosclerosis develops after otitis media (OM) and paracentesis in an experimental setting. The pathogenesis of this phenomenon of calcification is poorly understood. As the calcification process and the sclerotic plaques of the drum mimics features of bone tissue, this study explores tympanic membrane calcium deposition in association with the expression of three bone modelling markers: osteopontin (OPN), osteoprotegerin (OPG) and osteonectin (ON). OPN is secreted by osteoblasts and is found at calcification sites, e.g. during pathological calcification in chronic OM. The cytokine OPG is an inhibitor of bone resorption and consequently bone remodelling. ON is a calcium binding glycoprotein necessary for the maintenance of bone mass and remodelling. It is found in bone matrix and synthesized by osteoblasts. A rat model of acute otitis media (AOM) caused by non-typeable Haemophilus influenzae was used. Four days following middle ear inoculation, a myringotomy was performed in six animals. Another group of ten animals was inoculated only. The drum was dissected in two animals from each group on day 4, 7, 14 and 28 post-inoculation, and the expression of OPN, OPG and ON was determined by immunohistochemistry. von Kossa staining determined the deposition of calcium and immune staining for CD68 identified macrophages. Calcium depositions were initially accumulated in the cytoplasm of macrophages and dispersed in the connective tissue layers of the pars flaccida and tensa. Late accumulation occurred in the lamina propria of pars tensa, more extensively in myringotomized ears. OPN expression was found early in inflammatory cells including especially macrophages and late in pars tensa fibrocytes. OPG expression was initially located to inflammatory cells and late to pars tensa fibrocytes and the inner basal membrane of pars flaccida. Some ears displayed a marked pars flaccida expression of ON in the connective tissue matrix on early days and at the inner basal membrane on later days. The latter cases were from myringotomized ears. Otherwise, no apparent differences of marker expression occurred between myringotomized and non-myringotomized animals. We conclude that osteopontin, osteoprotegerin and osteonectin are expressed by different cell types in the tympanic membrane during calcification in association with AOM, with or without myringotomy. These molecules may accordingly play a role in the pathogenesis of myringosclerosis, in which macrophages and fibrocytes appear as potential major players.

Lamination of swampy-rivulets Rivularia haematites stromatolites in a temperate climate

Abstract Swampy-rivulets Rivularia haematites (D.C.) Agardh stromatolites were collected from the same site on the Plateau de Langres (Chaugey, France) over a seven year period. Specimens were studied in thin sections, in culture media under varying conditions of temperature and illumination, and by scanning electron microscope (SEM) in order to investigate the processes of calcification and lamination. New SEM observations confirm the polycrystalline structure of the ‘lamellae’ reported by the authors and show that the crystals composing these lamellae are elongate and aligned in the same direction as the filaments linked by them. The lamellae were also isolated in transverse sections under SEM and found to correspond to what under the light microscope appear to be ‘honeycomb’ structures. The diameter of alveoli can be the same as that of a ‘false branching’; their walls, formed by the outer sheath, have a dense network of microfibrils. These observations confirm the formation of calcitic lamellae at the false branching points and in contact with the microfibrils of the outer sheath. Confirmation of earlier hypotheses was sought through observation in thin section of the stromatolites collected over seven years. Micritic dark laminae are thought to form in three stages: (i) formation of a dark lamina by formation of a false branching zone in the wet season, (ii) initial calcification in this zone as microsparitic and sparitic lamellae during even a short dry spell, and (iii) subsequent bacterial micritization of the lamellae during an extended warm, dry season. The sparitic light laminae form around the hair-bearing regions. Lamination was first considered with regard to the annual radial growth rate of R. haematites. The thin section may display either a single dark lamina for two years’ growth, or a dark lamina thicker than the annual growth rate. Examination of local meteorological data accounts for the first phenomenon by a wet spell of more than 13 months and the second by a warm, dry period of one month. It may therefore take several years for a couplet to form as growth of the cyanobacterial colony is influenced by climatic variations. The different calcification phenomena were also correlated with dry spells. These interpretations are consistent with results obtained by experiments.

A new hypothesis on the mechanism of calcification formed on a blood-contacted polymer surface

Calcification on a blood-contacting polymer surface in an artificial heart is one of the most serious problems. Recently, we maintained a goat with a total artificial heart (AH) for 532 days without systemic anticoagulation. Sactype blood pumps coated with segmented polyurethane and incorporating jellyfish valves, thin polymer membrane valves, were used in the experiment. The pump was exchanged for a new one on the 312th day on the left side and the 414th day on the right side. They were analyzed with a scanning electron microscope (SEM) and an X-ray microanalyzer. The valve membrane after 312 days of pumping revealed plastic deformation expanding toward upstream between the spokes by creep fatigue with blood pressure difference when the valve closed. Calcification on the membrane was concentrated in the limited portions that received a strong stretching force: the upstream side of the membrane between the spokes and downstream side of the membrane on the spokes. Slight or no calcification was observed on the opposite side of the membrane that received a compression force, and no calcification was found on nonmoving parts such as the center of the membrane and spokes. A new hypothesis on the mechanism of calcification at the portion that received repeated stretching force was raised. The repeated stretching force would extend the polymer membrane, causing some loosening between polymer molecules and generating microgaps. The blood protein and phospholipid would invade into these microgaps, which would then attract Ca ions followed by phosphate ions to make their complexation. The hypothesis could well explain the calcification phenomena on a blood-contacting polymer surface, and gave a good clue on how to protect from calcification.

Signal changes in the intervertebral discs on MRI of the thoracolumbar spine in ankylosing spondylitis

Contrary to standard teaching in magnetic resonance imaging (MRI), recent reports have documented calcification appearing as areas of increased signal intensity (SI) on T1-weighted images. Intervertebral disc calcification is a frequent finding on radiographs in chronic ankylosing spondylitis (AS). This study was performed to investigate the appearance of variable degrees of disc calcification in MRI. Thirty-six patients with AS of variable duration underwent an MRI scan of the thoraco-lumbar spine and the MR appearances, particularly of the discs, were compared with plain radiographs. Increased SI of the discs on T1-weighted images were found in 17 of 36 patients, occurring over a range of disc levels, and correlating with disc calcification on the radiographs in 78% of cases. This group tended to be older and have a longer duration of disease than those with normal appearing discs. Four different patterns of increased signal within the discs termed Type A (marginal), Type B (annular), Type C (central) and Type D (solid) were identified. In those with less than six discs involved Type A was the most common pattern. In those with more than six discs involved Type D was the most common pattern, suggesting a progression of disc involvement with more advanced disease. Although these findings will not affect the management of the disease, they do highlight the recently described phenomenon of calcification appearing as increased SI on T1-weighted images, likely to be related to the surface area of the calcium crystal. This should lead to the consideration of calcium in the differential diagnosis of increased SI on T1-weighted images. End-plate marrow changes were a relatively frequent finding in this study but did not correlate with the signal changes seen within the discs; in a number of cases they related to variable degrees of bony bridging.

Scanning electron microscopy, X-ray diffraction, and electron microprobe analysis of calcific deposits on intrauterine contraceptive devices

Deposits found intrauterine contraceptive devices (IUDs) were studied by scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray microanalysis. All seven devices, including five plastic and two copper IUDs, were coated with a crust containing cellular, acellular, and fibrillar material. The cellular material was composed of erythrocytes, leukocytes, cells of epithelial origin, sperm, and bacteria. Some of the bacteria were filamentous, with acute-angle branching. The fibrillar material appeared to be fibrin. Most of the acellular material was amorphous; calcite was identified by x-ray diffraction, and x-ray microanalysis showed only calcium. Some of the acellular material, particularly that on the IUD side of the crust, was organized in spherulitic crystals and was identified as calcium phosphate by x-ray microanalysis. The crust was joined to the IUD surface by a layer of fibrillar and amorphous material. It is suggested that the initial event in the formation of calcific deposits on IUD surfaces is the deposition of an amorphous and fibrillar layer. Various types of cells present in the endometrial environment adhere to this layer and then calcify. Thus, the deposition of calcific material on the IUDs is a calcification phenomenon, not unlike the formation of plaque on teeth. Hum Pathol 16:732-738, 1985.

Inhibition of hydroxyapatite formation in collagen gels by chondroitin sulphate.

Crystal growth in native collagen gels has been used to determine the role of extracellular matrix macromolecules in biological calcification phenomena. In this system, type I collagen gels containing sodium phosphate and buffered at pH 7.4 are overlayed with a solution containing CaCl2. Crystals form in the collagen gel adjacent to the gel-solution interface. Conditions were determined which permit the growth of crystals of hydroxyapatite [Ca10(PO4)6(OH)2]. At a Ca/P molar ratio of 2:1, the minimum concentrations of calcium and phosphate necessary for precipitation of hydroxyapatite are 10 mM and 5 mM, respectively. Under these conditions, precipitation is initiated at 18-24h, and is maximal between 24h and 6 days. Addition of high concentrations of chondroitin 4-sulphate inhibits the formation of hydroxyapatite in collagen gels; initiation of precipitation is delayed, and the final (equilibrium) amount of precipitation is decreased. Inhibition of hydroxyapatite formation requires concentrations of chondroitin sulphate higher than those required to inhibit calcium pyrophosphate crystal formation.

The possible differentiation of osteogenic elements in vitro from chick limb mesodermal cells : I. Morphological evidence

In the developing chick limb bud, myogenic, fibrogenic, chondrogenic, and osteogenic tissues are derived from embryonic mesenchyme. Previous reports show that when stage 24 limb mesenchymal cells are cultured in vitro, chondrocytes, fibrocytes, and myocytes can be identified on the basis of morphological and biochemical parameters. The studies reported here clearly demonstrate that, in similar cultures, crystalline calcium phosphate material is deposited in the chondrocytic and fibrocytic matrices. Such crystalline material is not observed before Day 10 of culture life. Subsequent to Day 10 of culture, first amorphous, then crystalline calcium phosphate is observed. On the basis of light and electron microscopic analysis, it appears that the in vitro calcification phenomenon closely resembles the morphological and temporal sequence of osteogenesis observed in vivo.

Amino-acids and amino-sugars in calcified tissues of portunid crabs.

Amino acids and amino sugars determined in Portunid crab calcified tissues, giving relationship to calcification phenomenon

Ultrastructure of the approximal dental plaque and the underlying normal and carious enamel

An electron microscopical study has shown that approximal normal enamel surfaces, devoid of any microbial aggregation, are covered by an acquired pellicle in erupted teeth. The first stages of plaque formation are described. A greater number of bacteria with intracytoplasmic polysaccharide vesicles was found in carious human dental plaques when compared with plaques located over normal enamel. In both types coccoidal, rod-shaped and filamentous bacteria and an interbacterial matrix assuming structural variations were noted. In incipient brown spots, all covered by dental plaques, an association of calcification phenomena leading to calculus-like deposits and apatite crystal destruction occurring in the calcified dental plaque as well as in the enamel proper have been observed. In the classically intact surface layer of the enamel caries, two types of lesions have been located. The first defect was superficial but the second type consisted of a very small and deep defect extending through the almost intact external layer and reaching the sub-surface enamel. After different sequences of apatite crystal dissolution an ultrastructural consolidated organic matrix was present in the micro-areas where the apatite crystals had been destroyed. Sous le microscope électronique, la surface proximale de l'émail normal, dépourvue d'amas microbien, apparaît recouverte par une cuticule acquise au niveau de dents, ayant effectué leur éruption. Les premiers stades de formation de la plaque sont décrits. Un nombre plus élevé de bactéries, présentant des vésicules intracytoplasmiques de polysaccharides, est observé au niveau de plaques dentaires carieuses lorsqu'on les compare à des plaques situées au-dessus d'un émail normal. Dans les deux types de plaques, on rencontre des formes en bâtonnets, des formes filamenteuses ou rappelant des cocci. Une matrice interbactérienne présente des variations structurales. Au niveau de taches brunes, toutes recouvertes de plaques dentaires, une association de phénomènes de calcification, aboutissant à la formation de tartre, et de destruction d'apatites, se développant aussi bien dans la plaque calcifiée que dans l'émail, a pu être mise en évidence. Deux types de lésions ont pu être localisés dans la couche superficielle de la carie de l'émail, que l'on considère classiquement comme étant intacte. L'une de ces lésions est superficielle, alors que l'autre, profonde et étroite, s'étend à travers toute la couche externe de l'émail pour atteindre l'émail sous-jacent. Après différentes étapes de dissolution des apatites, une matrice organique “consolidée” a pu être individualisée sous le microscope électronique dans des micro-régions, où les cristaux d'apatite ont été détiuits. Elektronenmikroskopische Untersuchungen zeigten, dass normale, approximale Schmelzoberflächen von durchgebrochenen Zähnen ohne irgendwelche Keimansammlungen mit einem erworbenen Häutchen bedeckt sind. Die ersten Stadien der Plaquebildung werden beschreiben. Im Vergleich zu den über normalem Schmelz lokalisierten Plaques wurden in kariogenen menschlichen Zahnplaques eine grössere Anzahl von Bakterien mit intrazytoplasmatischen Polysaccharidbläschen gefunden. In beiden Typen wurden kokkenähnliche, stäbchenförmige und fadenförmige Bakterien sowie eine interbakterielle Matrix beobachtet, die strukturelle Unterschiede erkennen liess. In beginnenden braunen Flecken, die von Zahnplaques bedeckt waren, wirde ein Zusammenhang von Verkalkingsvorgängen mit zahnsteinähnlichen Ablagerungen und Apatitkristalldestruktion in den verkalkten Zahnplaques wie im nahegelegenen Schmelz festgestellt. In der nach klassischen Ansichten intakten Schmelzoberfläche über der Schmelzkaries wurden zwei Arten von Läsionen beobachtet: Der eine Defekt lag oberflächlich, der zweite Typus bestand dagegen aus einem sehr schmalen und tiefen Defekt, der sich durch die fast intakte äussere Lage in die Tiefe erstreckte und die unter der Oberfläche liegende Schmelzschicht erreichte. Nach verschiedenen Stadien der Apatitkristallauflösung existierte in den Mikrobereichen, in denen die Apatitkristalle zerstört worden waren, eine ultrastrukturell konsolidierte organische Matrix.