DENTAL CERAMICS Anyone who has ever initiated to chronicle the history of ceramic materials is certain to have discovered that the Chinese are credited with the development of porcelain as early as 1000AD.Many other people attempts to copy the crafts became unsuccessful to unravel the secrets of Chinese ceramic technology . Around 17th century after lot efforts ceramic technology became popular to the then world. Ceramics were tried in the dental field during 18th century. A French Apothecary by name Alexis Duchateau was edentulous (without teeth) and troubled by stained and odiferous ivory dentures, a condition probably quite common among the general population in those periods. Armed with his skill as an apothecary Duchateau attempted to make a pair of porcelain denture for himself. However, the initial effort was less successful. It was not until he teamed up with the Persian dentist Nicolas Dubois de Chemant that the two were able to construct complete dentures from a material they referred to as “mineral paste”. Satisfied with the fit of his new dentures, Duchateau returned to his apothecary shop. But de Chemant became intrigued by his experimentation and tried to reformulate the original “mineral paste”. De Chement eventually patented the formulation and in 1788 published a pamphlet on his work and very few of his cotemporaries regarded his action as a theft of Duchateau’s original invention. This was preceded by another invention by a French dentist Pierre Fauchard, the “father of modern Dentistry” who came out with baked enamel between 1728 and 1760. Individual porcelain teeth introduced to America around 1817. Later on, many inventors came out with ceramic teeth set which was popular in those days and became extinct by 1980s. The ceramic teeth were so hard and used with dentures found extreme loss of jawbone. In 1950s, literatures published revealing the successful pairing of porcelain-to-gold for fixed restorations. In 1962 M Weinstein, S Katz and AB Weinstein patented a method to fabricate the first ceramic crown. Introduction of automatic vacuum furnaces brought the ceramic technology to the doorstep of every dentist who wanted to fabricate the porcelain fused to metal (PFM) crowns and bridges in their own set up. Today the dentistry is so advanced that no one should die without teeth in his mouth, which should be the exact replica of gods own creation, the natural teeth. PFM is popular even today, but the esthetics sense of the people demanded for natural looking teeth without metal sub structures. This was yet another revolutionary step in the filed of ceramics. Today quite number of countries manufactures variety of ceramic systems and the technology is available to very part of the world. The incorporation of metals in the mouth become a hurdles to CT scan and MRI diagnostic aids. Today the Dentistry has taken over this challenge and the 21s century offer strong teeth without the trace of metal. Different types of ceramics: There are mainly two types of ceramics
Metal ceramics Precious metal and Non precious metal.
Advantage- cheaper and long span bridges can be constructed easily with this system. Disadvantages- Metal gives a black shade below the ceramics coated over. The precision of the metal may not be as good as other systems. Usually Nickel- chromium alloy is used. Beryllium is poisonous and many manufacturers bring out alloy containing this metal. Nickel is also banned in European countries.
Metal Free Ceramics.
a . Full ceramics b. Ceramic coated over tooth coloured sub structure c. Ceramic blocks a. Full ceramics: this is compressed form of ceramics. The aesthetics is very good but the strength is poor. Used for laminates ( a shell made up of ceramics to fix over the tooth correct the colour and shape of the tooth)and single crown( crown is the covering given after reducing the size of the original tooth). Since the strength is poor, the use is limited.
Ceramic fused over the sub structure like alumina and Zirconia Alumina(600 Mpa) and Zirconia(1100Mpa)are harder materials and Zirconia is the hardest one. Colour of the Alumina is more whitish or similar to natural colour. So this is being used in front teeth. Zirconia is stronger but colour is slightly dark. So this is often used in the posterior grinders. All the above said ceramics are hand crafted. The sub structure can be either hand crafted or machine crafted one. The new technology is to produce system, which are more accurate and time saving methods. Fillings and single crown can be made through computerized machines using very hard ceramic blocks. Since the machine is expensive, this has not come to India. One should know these different varieties of ceramics before you approach the doctor for discussion, all the materials quality should be assessed from the clinics before you start with the procedures. One of the interesting factor to know about the ceramics system is the cost factor. When a PFM crown is made in India at the lowest cost of Rs 2000/- the same procedure in Europe cost Rs 60,000/- !. Is there any difference in the quality of the procedures. Yes. In Europe the ceramic work is done by qualified ceramists and they visits the clinics and study the exact nature and colour of the teeth and under stand the demand of the patient. According to their assessment, the crown or bridge are fabricated and satisfy the demands of the doctors as far as the quality of the product is concerned. The doctors are also bound to give a quality work to the ceramist to his acceptance level. When both work together, a quality service is given. In our country, this teamwork is not there. We have limited labs and the technicians are not properly qualified and they never demand quality work from doctors and doctor also is blind enough to over look the quality of final products. New ceramic system can give a variety of shades which is more than one crore shades. combinations that is in a single yellow colour !. One Ceramic technician has to be a junior Michelangelo to craft a good tooth selecting the exact shade from the crores of probabilities. Our technicians do the entire show with selected shades of less than tem numbers. Even if somebody does a good job, this is difficult to recognize from the rest of work because the majority of our population has not seen the quality of the treatments executed in advanced countries.
Precious and non precious metals are used for PFM crowns. In earlier day’s natural feldspathic porcelain are used for non-precious PFM crowns. Because of its strong structural nature, wearing of the opposing tooth was more and now a day this is not preferred by western countries. Artificial glass materials are more common and its wearing nature is equivalent to the natural teeth and colour stability id more and shrinkage during heating is less. On precious metal always shows black shadow of the metal. Precious metal reduce the ‘metal effect’ of the crowns and precious metals are more compatible to the body if the cost factor is neglected. However, even today for long span bridges non precious metals are preferred.
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