Adhesive Strength between Flexible Hydroxyapatite Sheet and Tooth Enamel

Tooth enamel cannot be reconstructed once it is destroyed immoderately. Hydroxyapatite (HAp) thin sheet can potentially be used for a novel dental biomaterial to repair the enamel. Using a pulsed laser deposition (PLD) method, we have successfully created a flexible HAp sheet of less than a few micrometers in thickness. Due to its flexibility, the HAp sheet is tightly adhered on curved surfaces at the target site. In the present study, we newly developed double-layered sheets composed of HAp film coated with tricalcium phosphate (TCP) thin layer. The HAp/TCP sheet was adhered to the extracted human teeth using a calcium phosphate solution for 3 days. The adhesive strength between the HAp/TCP sheet and tooth enamel was evaluated by quasi-static tensile tests. Moreover, the interface structure between them was observed by a scanning electron microscopy. As a result of the mechanical evaluation, the adhesive strength was greater than approximately 2.5 MPa. The electron microscopic observation revealed that the sheet was partially fused with the enamel. These findings suggest the possibility that enamel defects are repaired using the HAp/TCP sheet for a short duration.

Download Full-text

Investigations on arc brazing for galvanized heavy steel plates in steel and shipbuilding

Welding in the World ◽

10.1007/s40194-021-01087-2 ◽

2021 ◽

Author(s):

Philipp Andreazza ◽

Andreas Gericke ◽

Knuth-Michael Henkel

Keyword(s):

Low Cost ◽

Thin Sheet ◽

Steel Structures ◽

Tensile Tests ◽

Fatigue Tests ◽

Steel Plates ◽

Galvanized Steel ◽

Filler Materials ◽

Static Tensile ◽

Brazed Joints

AbstractArc brazing with low-melting copper-based filler materials, which has long been established and standardized in the thin sheet sector, offers numerous advantages in the processing of predominantly electrolytically galvanized steel structures. In steel and shipbuilding, on the other hand, equipment parts made of thick steel sheets are hot-dip galvanized at low cost and with good corrosion-inhibiting properties. Quality welding of such constructions is not possible without special precautions such as removing the zinc layer and subsequent recoating. With regard to greater plate thicknesses, arc brazing was analyzed in these investigations as an alternative joining method with regard to its suitability for practical use. Within the scope of the investigations, CuSi3Mn, CuMn12Ni2, and four different aluminum bronzes were examined on different sheet surface conditions with regard to the geometrical and production parameters. This was carried out by build-up and connection brazing, executed as butt and cross joints. Quasi-static tensile tests and fatigue tests were used to assess the strength behavior. In addition, metallographic analyses are carried out as well as hardness tests. The suitability for multi-layer brazing and the tendency to distortion were also investigated, as well as the behavior of arc brazed joints under corrosive conditions.

Download Full-text

Regeneration of Tooth Enamel by Flexible Hydroxyapatite Sheet

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.493-494.615 ◽

2011 ◽

Vol 493-494 ◽

pp. 615-619 ◽

Cited By ~ 4

Author(s):

Shigeki Hontsu ◽

Nobuhiro Kato ◽

Ei Yamamoto ◽

Hiroaki Nishikawa ◽

Masanobu Kusunoki ◽

...

Keyword(s):

Mechanical Characteristics ◽

Tooth Enamel ◽

Dental Enamel ◽

Laser Deposition ◽

Phosphate Solution ◽

X Ray Diffraction ◽

Human Teeth ◽

X Ray ◽

Scratch Tests ◽

Soluble Substrate

Before a tooth erupts, the ameloblasts are lost, which means that the tooth enamel does not regenerate itself after tooth eruption. In the present study, we attempt to regenerate the tooth enamel artificially using a flexible hydroxyapatite (HAp) sheet. First, a HAp film was deposited on a soluble substrate by pulsed laser deposition (PLD) using an ArF excimer laser. Next, the HAp film was collected as a freestanding sheet by dissolving the substrate using a solvent. The HAp sheet was adhered to the extracted human teeth using a calcium phosphate solution. The variation of the crystal structure of the HAp sheet with time was investigated by X-ray diffraction analysis. Furthermore, the variation in the mechanical characteristics with time between the HAp sheet and dental enamel were evaluated using tensile and scratch tests. The results suggest that the HAp sheet became fused to the tooth enamel within approximately one week.

Download Full-text

Electron Microscopic Observation of the Longitudinal Organization of Poly (p-Phenylene Terephthalamide) Fibers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055734 ◽

1982 ◽

Vol 40 ◽

pp. 680-681

Author(s):

Li Li-Sheng ◽

L.F. Allard ◽

W.C. Bigelow

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Scanning Electron Microscopy ◽

Microscopic Observation ◽

Electron Microscopic Observation ◽

Electron Microscopic ◽

Aromatic Polyamides ◽

Radial Arrangement ◽

Scanning Electron ◽

Better Than

The aromatic polyamides form a class of fibers having mechanical properties which are much better than those of aliphatic polyamides. Currently, the accepted morphology of these fibers as proposed by M.G. Dobb, et al. is a radial arrangement of pleated sheets, with the plane of the pleats parallel to the axis of the fiber. We have recently obtained evidence which supports a different morphology of this type of fiber, using ultramicrotomy and ion-thinning techniques to prepare specimens for transmission and scanning electron microscopy.

Download Full-text

Observation of Concanavalin-A receptors on hydrated planar erythrocyte membrane film by in situ electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076640 ◽

1983 ◽

Vol 41 ◽

pp. 608-609

Author(s):

Neng-Bo He ◽

S.W. Hui

Keyword(s):

Lipid Bilayers ◽

Erythrocyte Membrane ◽

Lipid Membranes ◽

Surface Film ◽

Biological Membranes ◽

Electron Microscopic Observation ◽

Electron Microscopic ◽

Black Lipid Membranes ◽

Fine Mesh ◽

Planar Films

Monolayers and planar "black" lipid membranes have been widely used as models for studying the structure and properties of biological membranes. Because of the lack of a suitable method to prepare these membranes for electron microscopic observation, their ultrastructure is so far not well understood. A method of forming molecular bilayers over the holes of fine mesh grids was developed by Hui et al. to study hydrated and unsupported lipid bilayers by electron diffraction, and to image phase separated domains by diffraction contrast. We now adapted the method of Pattus et al. of spreading biological membranes vesicles on the air-water interfaces to reconstitute biological membranes into unsupported planar films for electron microscopic study. hemoglobin-free human erythrocyte membrane stroma was prepared by hemolysis. The membranes were spreaded at 20°C on balanced salt solution in a Langmuir trough until a surface pressure of 20 dyne/cm was reached. The surface film was repeatedly washed by passing to adjacent troughs over shallow partitions (fig. 1).

Download Full-text

The Scanning Electron Microscopic Observation of the Vestibular Sensory Epithelia

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100062105 ◽

1969 ◽

Vol 27 ◽

pp. 40-41

Author(s):

D.J. Lim ◽

W.C. Lane

Keyword(s):

Semicircular Canals ◽

Electron Microscopic Observation ◽

Gravitational Acceleration ◽

Electron Microscopic ◽

Sensory Epithelia ◽

Scanning Electron Microscopic ◽

Vestibular Sensory Epithelia ◽

And Function ◽

Sand Piles ◽

Active Investigation

The morphology and function of the vestibular sensory organs has been extensively studied during the last decade with the advent of electron microscopy and electrophysiology. The opening of the space age also accelerated active investigation in this area, since this organ is responsible for the sensation of balance and of linear, angular and gravitational acceleration.The vestibular sense organs are formed by the saccule, utricle and three ampullae of the semicircular canals. The maculae (sacculi and utriculi) have otolithic membranes on the top of the sensory epithelia. The otolithic membrane is formed by a layer of thick gelatin and sand-piles of calcium carbonate crystals (Fig.l).

Download Full-text

Plastic deformation of θ ' in Al-4%Cu alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110027 ◽

1978 ◽

Vol 36 (1) ◽

pp. 576-577

Author(s):

Shrikant P. Bhat

Keyword(s):

Deformation Behavior ◽

Room Temperature ◽

Electron Microscopic Observation ◽

Bulk Alloy ◽

Electron Microscopic ◽

Cu Alloy ◽

Cu Alloys ◽

Orowan Mechanism ◽

The Subject ◽

Cyclic Straining

deformation behavior of Al-Cu alloys aged to contain θ ' has been the subject of many investigations (e.g., Ref. 1-5). Since θ ' is strong and hard, dislocations bypass θ ' plates (Orowan mechanism) at low strains. However, at high strains the partially coherent θ ' plates are probably sheared, although the mechanism is complex, depending on the form of deformation. Particularly, the cyclic straining of the bulk alloy is known to produce gross bends and twists of θ '. However, no detailed investigation of the deformation of θ ' has yet been reported; moreover, Calabrese and Laird interpreted the deformation of θ ' as largely being elastic.During an investigation of high temperature cyclic deformation, the detailed electron-microscopic observation revealed that, under reversed straining conditions, θ ' particles are severely distorted--bent and twisted depending on the local matrix constraint. A typical electronmicrograph, showing the twist is shown in Fig. 1. In order to establish whether the deformation is elastic or plastic, a sample from a specimen cycled at room temperature was heated inside the microscope and the results are presented in a series of micrographs (Fig. 2a-e).

Download Full-text

Electron Microscopic Observation of Biological Specimens in Their Native State by Employing Cryogenic Techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100095315 ◽

1972 ◽

Vol 30 ◽

pp. 410-411 ◽

Cited By ~ 1

Author(s):

Tokio Nei ◽

Haruo Yotsumoto ◽

Yoichi Hasegawa ◽

Yuji Nagasawa

Keyword(s):

Electron Microscopic Observation ◽

Surface Structures ◽

Specimen Preparation ◽

Native State ◽

Electron Microscopic ◽

Biological Specimen ◽

Specimen Holder ◽

Cold Stage ◽

Preparation Techniques ◽

Scanning Electron

In order to observe biological specimens in their native state, that is, still containing their water content, various methods of specimen preparation have been used, the principal two of which are the chamber method and the freeze method.Using its recently developed cold stage for installation in the pre-evacuation chamber of a scanning electron microscope, we have succeeded in directly observing a biological specimen in its frozen state without the need for such conventional specimen preparation techniques as drying and metallic vacuum evaporation. (Echlin, too, has reported on the observation of surface structures using the same freeze method.)In the experiment referred to herein, a small sliced specimen was place in the specimen holder. After it was rapidly frozen by freon cooled with liquid nitrogen, it was inserted into the cold stage of the specimen chamber.

Download Full-text

Hydrated form of some clay minerals observed using a film sealed environmental cell

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107502 ◽

1978 ◽

Vol 36 (1) ◽

pp. 72-73

Author(s):

N. Kohyama ◽

K. Fukushima ◽

A. Fukami

Keyword(s):

Clay Minerals ◽

Morphological Changes ◽

Carbon Film ◽

Electron Microscopic Observation ◽

Adsorbed Water ◽

Electron Microscopic ◽

Hydrated Form ◽

Thin Carbon ◽

Environmental Cell ◽

Thin Carbon Film

Since the interlayer or adsorbed water of some clay minerals are quite easily dehydrated in dried air, in vacuum, or at moderate temperatures even in the atmosphere, the hydrated forms have not been observed by a conventional electron microscope(TEM). Recently, specific specimen chambers, “environmental cells(E.C.),” have been developed and confirmed to be effective for electron microscopic observation of wet specimen without dehydration. we observed hydrated forms of some clay minerals and their morphological changes by dehydration using a TEM equipped with an E.C..The E.C., equipped with a single hole copper-microgrid sealed by thin carbon-film, attaches to a TEM(JEM 7A) with an accelerating voltage 100KV and both gas pressure (from 760 Torr to vacuum) and relative humidity can be controlled. The samples collected from various localities in Japan were; tubular halloysite (l0Å) from Gumma Prefecture, sperical halloysite (l0Å) from Tochigi Pref., and intermediate halloysite containing both tubular and spherical types from Fukushima Pref..

Download Full-text

Permeability Enhancing and Chemotactic Activities of Lower Molecular Weight Degradation Products of Human Fibrinogen

Thrombosis and Haemostasis ◽

10.1055/s-0038-1650136 ◽

1981 ◽

Vol 45 (01) ◽

pp. 090-094 ◽

Cited By ~ 52

Author(s):

Katsuo Sueishi ◽

Shigeru Nanno ◽

Kenzo Tanaka

Keyword(s):

Molecular Weight ◽

Degradation Products ◽

Electron Microscopic Observation ◽

Chemotactic Activity ◽

Lower Molecular Weight ◽

Electron Microscopic ◽

Human Fibrinogen ◽

Rabbit Skin ◽

Molecular Weights ◽

Active Fragments

SummaryFibrinogen degradation products were investigated for leukocyte chemotactic activity and for enhancement of vascular permeability. Both activities increased progressively with plasmin digestion of fibrinogen. Active fragments were partially purified from 24 hr-plasmin digests. Molecular weights of the permeability increasing and chemotactic activity fractions were 25,000-15,000 and 25,000 respectively. Both fractions had much higher activities than the fragment X, Y, D or E. Electron microscopic observation of the small blood vessels in rabbit skin correlated increased permeability with the formation of characteristic gaps between adjoining endothelial cells and their contraction.These findings suggest that lower molecular weight degradation products of fibrinogen may be influential in contributing to granulocytic infiltration and enhanced permeability in lesions characterized by deposits of fibrin and/or fibrinogen.

Download Full-text