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Dental laboratory Ferylabor | |
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-- Gold --
Foreword: GOLDhas always been a material of choice for the most prestigious. He has been able to find its place in dentistry as in many other areas. Now, with the advent of prosthetic implants, we can't afford to not use it. DefinitionPrecious Metal of a bright yellow ; element (Au) with atomic number 79, atomic weight 196.96. High density of 19.32 at 20 ° C, it is an excellent conductor of electricity and heat. It melts down at 1064.4 ° C and boils at 2807 ° C.Gold is the most malleable and ductile of all metals; 1Gr can be stretched into a wire 2Km long , or transformed into an ultra-thin sheet with a thickness of 10 -7 m. and a surface area of about 1.5 m 2. It is soft, lence the necessity to associate it with other metallic elements. These alloys have exceptional qualities, useful in many applications. At whatever température, gold does not oxidize in the air, nor in water. More over it is not attacked by the action of a strong acid, even concentrated and very hot. Stable, it dissolves only in mercury and aqua regia. It draws from veins of gold learning rocks or from the gold learning alluvial deposts in rivers or in quarries. Different kind of mineralurgiques processes are necessary to recover gold from the raw mixture (grinding, crushing, amalgamation, distillation, cyanidation, refining…) . Top HistoryThe story of gold is intimately linked to the mankind one. Revered and highly coveted, it triggered the most unsane passions.First, gold distinguished itself by its brilliance and his geniuse colour. Peculiarities which make it equal to the sun, which is the gold star Râ in egyptology. The discovery of its inalterability, its rarity and its amazing properties did amplified man’s imagination. The grand design of alchemy, for example, was to obtain the transmutation of "vile" metals (such as copper) to "noble" metals (such as gold). Undoubtedly, it would have open the way to wealth and power to those who would subdue the precious substance. The epic of gold really started with the first shipments of Columbus . The conquerors were motivated by the promise of wealth. However, we must await the arrival of the Conquistadors to get the desired results. They are the sad actors of killings and thefts to steal gold wich was easily accessible in ornaments, jewelry, gifts… The idea of gold in the human thought evolved with the increase of his production (from the role of gold) it became matter of trade, the sign of authority and power having nothing to do with the divine anymore. But still the use of gold as a currency gave bith to a formidable greed in the human heart. The rush for GoldCalifornia was sold less than fifteen million dollars for the United States by Mexico . This new state revealed itself as an exceptional gold deposit. March the fifteth, 1848, the "Californian" local newspaper announced the discovery of gold in the Sacramento River . The rush that followed was made easier by the modern means of communication. Fever spread throughout the world. More than four million pioneers came from Europe. At a cost of many lifes, more than 700 tons of gold were obtained only in the space of tuelve years. The discovery of other mines in nothern Canada and Alaska carried men over there. Less disoderly, Australia know also its gold rush.Top Some figuresSince its discovery, more than 125,000 tons of gold would have been extracted from our soil.World production fluctuates currently between 1,500 and 2,000 tonnes per year. 30% are provided by South Africa which is the largest producer, far above the United States, Australia and the Soviet Union. Major consuming countries: India, the United States, Japan, China, Saudi Arabia, Italy. Banks hoard most of the gold world (see market value), the rest is shared in different fields such as goldsmiths-jewellery, dentistry and industry. The market is divided as follows: 80% for jewellery / 10% for the currency (coins and gold bars) / 10% for industrial and other uses. The largest gold nugget ever found so far was discovered in 1872 in Australia. It was name the legendary "plate Holtermann" weighted 235 kg and was 1.42 metres high. gold market value:On June 20, 1980, the price of an ounce reached an absolute peak: $ 850 for a Troy ounce (31.1035 grams of pure gold). Since then, price trends downwards and this has been proved during the fall of 1997 when the price fell below $ 300.Now gold is not considered as so safe value anymore and the value of the dollar (and other currencies) is no longer linked to the yellow metal either. For twenty years, consumer prices have doubled, while the price of gold dropped on an ongoing basis. Several reasons can explain this phenomenon. The production of gold never stop increasing, it is indestructible and recyclable at will, banks start to get rid of it. For example, the stock of the National Bank of Belgium is 300 tonnes today so it elevated to 1185 tonnes in the year 1989. Until recently, despite the fact that gold was not used as a measure of the currency any longer, the central bank still retained a stock of gold and some foreign currencies which were used to cover deficits in the trade balance. But the introduction of Euro makes this precaution unnecessary. While the supply of gold on the market increases, the demand for it remains static. Top Gold ProtheseUntil the eighteenth century, the dentures were made of human teeth (those extracted from the patient or from cadavers and sculpted) linked by ties of gold threads. Earlier still , some were carved in a variety of organic materials such as bones or teeth of horses, cattles, hippopotamuses… or even in white wood. Fortunately we could go further off thanks to apothecaries who were able to pave the way toward new directions.Inlays gold sankThe application of cemented golden blocks in a cavity was born in 1884 thanks to the dentist Aguilhon of Sarran, who introduced his technique to the Society of Stomatology of Paris in 1903. After taking a waxen imprint and put this wax in a coating of plaster and talc, eliminated it with hot water, it melted the 22-carat gold with a blow torch and poured it into the mould thus obtained.It's O. Sölbrig who launched this technology a few years later. Always topical, gold inlay is still remaining the most effective sealing (for a long term). Crowns and bridge goldThe technique of the ring crown has greatly contributed to the advent of gold in dentistry. Many patients still retaining this kind of restoration even if it is carried out briefly but still efficiently.Currently with modern techniques of implementation, the use of alloys based on gold in dentistry doesn't show any weakness anymore. For aesthetic reasons, one masks on the visible metal parts are masked by using cosmetic materials such as ceramics whose appearance can imitate perfectly natural teeth. LongevityThe lifetime of based gold alloys in buccal environment is estimated around 20 years on average, wich is significantly longer than other dental materials. Thinking that during this time, certain materials should be replaced several times, we realize that the patient will get back quickly the invesment he was previously on this alloy. In terms of bio-compatibility, the choice of a precious alloy proves to be a wise investment for the patient's health and comfort.The economic crisis which is undergoing since the eighties made us forget all respect due to this noble material that has gone through the ages with dignity. Alloys considered as "economic" have invaded the market. Now, more than 1000 alloys of all kinds are available on the dental market. All don't offer the guarantees that we are entilled to expect. Top |
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