Search PubMed⌕ Search

Biomedical subjects

W L Jongebloed

Publications and source records attributed to W L Jongebloed.

At least 73 records · Page 4Linked to original sources
PubMed1984

Scanning electron microscopic study of eye tissues.

We present a survey of our current investigations on lens and corneal tissue. Using scanning electron microscope techniques, we have studied lens fiber organization, lens capsule and subcapsular epithelium, the effect of Nd:YAG laser treatment on the lens, the endothelial effects of a relatively traumatic introduction of an intraocular lens, with and without sodium hyaluronate (Healon) pretreatment, and the epithelial reaction to foldings in Descemet's membrane (Descemet's folds).

Animals↗
PubMed1984

Quantitative cement solubility experiments in vivo.

The dissolution and dissolution rate of dental luting cements was measured longitudinally. Cement samples in enamel were placed in a full prosthesis and worn in the mouth for up to 6 months. At given intervals, replicas of the cement surfaces were made and quantified by means of SEM stereographic photographs. With a stereometer the distance between cement surface and original enamel surface can be determined quantitatively. The results show in vivo solubility rates for zinc-phosphate and glass-ionomer cement of about 80 microns week-1 and 2 microns week-1 respectively.

Animals↗
PubMed1984

Crystallographic structure of enamel surfaces treated with topical fluoride agents: TEM and XRD considerations.

The crystallographic structure of surface coatings produced by three topical fluoride agents deposited by a single application on intact human enamel surfaces was investigated by light- and dark-field transmission electron microscopy, as well as by electron and x-ray diffraction. The agents studied were an acidic silane fluoride lacquer, a neutral NaF lacquer, and an APF gel. The smallest coherently diffracting particles were CaF2 microcrystallites 4-15 nm in diameter. Large apatite-like crystals, approximately 1 micron in length, were also observed in the outer surface coating produced by the silane fluoride lacquer.

Animals↗
PubMed1983

The mineral content of human enamel studied by polarizing microscopy, microradiography and scanning electron microscopy.

The total observed birefringence and mineral content of the outer 300 micron of longitudinal sections of sound buccal premolar enamel were measured and three-dimensional contour maps were made. Using similar contour maps of calcium, carbonate and magnesium content from the literature, it seemed possible to explain the differences between the contour maps of total observed birefringence and mineral content. Scanning electron micrographs provided information about the orientation of the prisms. The cervical part of the enamel had a high intrinsic birefringence which may explain the difference between mineral content and total observed birefringence. This high intrinsic birefringence may be caused by a high carbonate content in cervical enamel.

Bicuspid↗
PubMed1983

Morphology of enamel surfaces treated with topical fluoride agents: SEM considerations.

Three topical fluoride agents deposited surface coatings of different morphology and thickness on intact human enamel surfaces. The agents studied were an acidic silane fluoride lacquer, a neutral NaF lacquer, and an APF gel. Each agent reacted with the enamel surface differently, producing its own distinctive etching pattern. The smallest particles observed in the surface coatings were from 20 to 30 nm in diameter and appeared to have indistinct morphologies. They often agglomerated into spherical globules ranging from 1-3 micron in diameter.

Acidulated Phosphate Fluoride↗
PubMed1982

Fluoride deposited by topical applications with stannous fluoride in human enamel.

The aim of this study was to quantify the fluoridating effect of a 4% aqueous solution of SnF2 applied for 5 min. and 30 min. resp., and to measure the amounts of KOH soluble fluoride and acquired fluoride separately (APF gel data being included for comparison). Blocks of intact enamel were treated with the topical agents and subsequently exposed to 1 M KOH solutions for 24 h. No significant amount of fluoride was dissolved from control specimens by this treatment. Subsequently, the acquired F in the enamel was determined by the acid etch technique. The amount of fluoride in the KOH solutions after 5 and 30 min. SnF2 application are comparable : 6.2 and 7.4 micrograms . cm(-2) resp. A single topical treatment of SnF2 of 5 and 30 min. did not produce a significant enrichment of fluoride in the enamel. The considerable accumulation of fluoride reaction products on the outer enamel surface was only 1/3 of the amount deposited by APF gels.

Acidulated Phosphate Fluoride↗
PubMed1982

Birefringence and mineral content of the first stage of artificial carious lesion formation (a combined polarizing microscopic, microradiographic and scanning electron microscopic investigation).

Artificial carious lesions were made using acetic buffer solutions of pH 6.0 containing calcium and phosphate. The solutions were highly undersaturated with respect to hydroxyapatite. Out of 72 lesions 51 showed subsurface demineralization, whereas in 21 only a superficial demineralization occurred. These superficial lesions were examined using polarized light microscopy, microradiography and scanning electron microscopy. This superficial breakdown of enamel material, considered as the initial demineralization of the enamel, appeared to occur at the prism junctions. This was indicated by the polarizing microscope technique and was made clearly visible using scanning electron microscopy. Quantitative polarizing microscopy and microradiography revealed results which correlated very well. From this it is probable that the initial superficial demineralization of the enamel is--under the described conditions--a simple dissolution reaction.

Birefringence↗
PubMed1981

Microchannels in the surface zone of artificially produced caries-like enamel lesions.

In the surfaces zones of artificial carious lesions, tiny microchannels, about 0.5 - 1.5 micrometers in diameter and roughly 100 micrometers in length, have been observed. The mineral components seem to be concentrated at the lumen borders, whereas the organic components have disappeared or are disorganized. These observations suggest that the channels mentioned are involved in the lesion development and play an important role in diffusion (transport) processes taking place between the sub-surface lesion and the liquid phase outside the lesion. The microchannels originate in prisms in the perikymata of the surface enamel. They extend in the direction of the Hunter-Schreger bands, mainly in connection with diazones. No relationship could be found between the microchannels and the direction of the prism sheaths. This indicates that in initial artificial lesion formation the enamel structure plays an important role.

Dental Caries↗
PubMed1979

Ultrastructural studies of synthetic apatite crystals.

In this paper a survey is given of some ultrastructural properties of synthetic hydroxyapatite. The preparation method by which single crystals with a length in the range of 0.1-3.0mm and a defined purity and stoïchiometry can be produced is given. Two groups of materials are considered in detail: carbonate-rich (greater than 0.1% CO3) and low-carbonate hydroxyapatites. The experiments on carbonate-rich material, being the most interesting from a biological point of view, show that acids attack at an active site in the hexagonal basal-plane of the crystals. Later on the crystals dissolve in the center of the crystal parallel to the c-axis forming tube-like structures. The active site can be protected from dissolution if the crystals are pretreated by EHDP or MFP. A comparison with lattice defect theory shows that most likely dislocations of the "hollow-core" type are responsible for the preferential dissolution.

Acids↗