The root surface in human teeth: a microradiographic study.
(1/97)
In an attempt to clarify the nature of the human cemento-dentinal junction, ground sections of incompletely formed and fully formed extracted teeth were prepared and their histology compared with their microradiographic appearances. The results showed that incompletely formed teeth possess distinctive surface layers outside the granular layer of Tomes. The evidence indicates that these layers are of dentinal origin; their presence during development supports previous explanations by the author of the hyaline layer of Hopewell-Smith and of so-called intermediate cementum. The results also indicate that the granular layer of Tomes does not represent the outer limit of root dentine. The relationship of these surface layers to the definitive cementum which is present in fully formed teeth was studied in both young and older patients. From the results it was concluded that cementum formation begins in the more apical region of the teeth at a time when root formation is well advanced, and that it spreads towards the crown rather than in the generally accepted reverse direction. (+info)
The development and structure of the chimpanzee mandible.
(2/97)
The sites of growth and remodeling, and the associated changes in cortical bone structure, have been studied in the chimpanzee mandible and compared with those previously reported in the human and macaque mandibles. The location of the principal sites of growth, and the distribution of the areas of deposition and resorption in the ramus, were found to be similar in all three species. In the chimpanzee, unlike Man, the bone being deposited at the condyle, posterior border of the ramus and coronoid process was plexiform in nature, indicating very rapid growth. The pattern of remodeling in the mandibular body, on the other hand, showed marked species differences at the chin and on the submandibular lingual surface, which account for the contrasts seen in the adult morphology of these regions. Although the pattern of distribution of cortical densities differed from that of surface remodeling, the information they give is complementary in analysing bone growth. The densest regions were found to coincide with sites of consistent lamellar deposition, while the least dense regions were those where plexiform bone was formed. Areas where remodeling led to the greatest reorientation of bone tissue within the cortex showed the greatest disparity between the two patterns. (+info)
Digitized cerebral synchrotron radiation angiography: quantitative evaluation of the canine circle of Willis and its large and small branches.
(3/97)
BACKGROUND AND PURPOSE: Conventional X-ray angiography lacks the sensitivity and spatial resolution needed to detect small amounts of iodinated contrast material and to quantitate diameters of the small vessels in the brain. The purpose of this study was to ascertain whether digitized synchrotron radiation microangiography, with the use of a high-definition TV camera system, can accurately show small cerebral vessels. METHODS: Six anesthetized dogs were exposed to monochromatic synchrotron radiation with an energy level of 33.3 keV optimized for iodine detection while iodinated contrast material was injected into the brachiocephalic and vertebral arteries. The images were detected with a high-definition TV camera system with a spatial resolution of 30 microm. In all, 26 cerebral angiograms of the circle of Willis with its branches were obtained, and the images were digitized at a workstation. RESULTS: The small branches of the circle of Willis were clearly visible on all images. Vasodilatation of the circle of Willis and its large and small branches induced by CO2 inhalation was quantitatively confirmed on the images: for example, the diameter of one small branch was increased from 0.24 +/- 0.04 mm to 0.38 +/- 0.12 mm. Temporal subtraction improved the image quality. CONCLUSION: The synchrotron radiation angiographic system is useful for visualizing large and small vessels deep in the brain as well as for quantitating their diameters. (+info)
Inhibition of carious lesions in vitro around gallium alloy restorations by fluoride releasing resin-ionomer cement.
(4/97)
A new fluoride releasing resin-ionomer cement was used for bonding of gallium alloy restorations in vitro. Etching, priming, and fluoride releasing resin-ionomer cement were used in the experimental group (ARG), prior to placement of the gallium alloy restorations. Three different controls were used: gallium alloy only (G), no etching, fluoride releasing resin-ionomer cement, gallium alloy (RG), etching, priming, non-fluoride cement and gallium alloy (ACG). The mean shear bond strengths of ARG group to enamel and dentin were higher than those of the three control groups. Artificial secondary caries lesions around the restorations in the experimental group and the control groups were produced, using a strep. mutans culture. The microradiographs were examined for presence of a caries inhibition zone near the restoration. Caries inhibition zones were clearly detected around RG and ARG, but not around G and ACG. The results indicate that the fluoride releasing resin-ionomer cement provided good adhesion and caries inhibition in enamel and dentin. (+info)
The pattern of intramural veins of the left ventricle of the human heart.
(5/97)
A detailed injection, microradiographic, and histological necropsy study of 18 hearts showed that the pattern of myocardial veins differed from the arterial pattern. In "normal" hearts, large drainage veins began in the subendocardial zone and coursed fairly directly towards the epicardium, maintaining a comparatively even calibre throughout. Smaller, but similar, drainage veins also begain in the middle of the myocardial wall. In the outer myocardium small groups of these vessels converged to form a single vein which then entered, almost at right angles, the pericardial veins. In general, small veins within the myocardium entered directly into the large drainage veins without any extensive intermediate sized venous network. In "abnormal" hearts with left ventricular hypertrophy the myocardial veins appeared basically normal but were more widely separated and consequently overall less dense on microradiography. Interruption of main drainage veins and loss of normal pattern were seen in areas of myocardial fibrosis associated with coronary artery disease. In a heart with severe generalized coronary artery atheroma the normal pattern in the inner half of the wall was replaced by a "plexus" of small veins in which the majority of vessels coursed circumferentially. The possible significance of both the normal and abnormal vein pattern is discussed. (+info)
Lens growth and protein density in the rat lens after in vivo exposure to ultraviolet radiation.
(6/97)
PURPOSE: To investigate lens growth after different doses of ultraviolet radiation (UVR) and to investigate the long-term effect of a near-threshold UVR dose on the refractive index distribution in the lens. METHODS: Sprague-Dawley rats received UVR (lambda(MAX) = 300 nm) unilaterally during a 15-minute period. The exposure dose ranged from 0.1 to 20 kJ/m(2), and the rats were kept for up to 32 weeks after exposure. Intact lenses were photographed and lens wet and dry masses were measured. The protein density was estimated by quantitative microradiography. Freeze-dried lens sections were used for contact x-ray photographs. From the transmission of the microradiographs, protein density and refractive index profiles were calculated along the lens radius with a resolution of 2.5 microm. RESULTS: Lens dry mass in exposed eyes was lower than in nonexposed eyes at one week after exposure. Lens water content was decreased after low UVR doses but increased after high doses. The difference between exposed and nonexposed lenses in dry mass and water content increased with time after exposure. No significant difference was found for the mean protein density in exposed and nonexposed lenses. The protein density increased linearly in the lens cortex, from a minimum in the superficial cortex of 0.26 g/cm(3) to a maximum in the deep cortex of 0.81 g/cm(3). This corresponded to a refractive index of 1.38 and 1.48, respectively. CONCLUSIONS: Lenses exposed to UVR grew more slowly than their nonexposed contralaterals. This growth inhibition was dose dependent. Near-threshold doses led to decreased water content in the lens whereas high doses led to swelling. Six months after near-threshold UVR exposure, no global change of the refractive index was found. However, local variations of the refractive index caused a subtle cortical light scattering. (+info)
On the relationship between tetracycline and the incremental lines in dentine.
(7/97)
Ground and decalcified sections of human, goat and pig teeth were examined using polarized and ultraviolet fluorescence microscopy, microradiography and electron microscopy. The experimental animals were given doses of tetracycline within the range 3-150 mg/kg. After the low doses there was no evidence of any disturbance of mineralization or of structural organization in either the goat or the pig. After the higher doses, however, the tetracycline lines usually corresponded with a disturbance of structural organization and often with a disturbance of mineralization as well. In the human cases, the tetracycline lines sometimes corresponded with a disturbance of mineralization or of structural organization. However, our evidence suggests that the disturbances in the structure or mineralization of the dentine in the human subjects were not caused by the tetracycline. It was concluded that, provided the dose is kept low (3-31 mg/kg) tetracycline can be used as a reliable non-toxic marker in growth studies and is also used in the study of mineral deposition. (+info)
A structural study of gallstones.
(8/97)
A number of gallstones have been studied using methods which have not previously been applied to gallstones. In particular, the use of scanning electron microscopy and micro-x-radiography have allowed detailed observations to be made on the structure of the stones and the distribution of the various components within the stones. Large differences in structure have been shown to exist between stones having similar overall chemical compositions. In cholesterol gallstones containing calcium carbonate the crystalline nature, distribution and method of deposition of the calcium carbonate was studied and was found to vary from stone to stone. Evidence was found for the presence of fibrous material in the centre of many stones and it is possible that this material acted as a nucleus for the deposition of the other stone components. (+info)