Compositions: ceramic – Ceramic compositions
Patent
1998-12-07
2000-08-29
Koslow, C. Melissa
Compositions: ceramic
Ceramic compositions
106 35, 501123, 423308, 423309, 423311, 423314, 423315, C01B 2532
Patent
active
061108510
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of producing a ceramic material based on calcium phosphate compounds for use in dental medicine.
In dental medicine, plastics materials, such as amalgams, synthetic materials and inorganic cements are usually used for removing defects, particularly carious defects. Another method of repairing carious defects is to use metal, e.g. gold, inlays. There are drawbacks with these conventional materials, such as allergies which may occur with amalgams, insufficient mechanical strength, and the high cost in the case of precious metal inlays.
The production is also already known of plastically deformable ceramic tooth filling materials, dental cements and dental bonding agents, whereof the mechanical and physical-chemical properties resemble those of the natural tooth enamel. These are de-mineralised in acid medium like natural tooth enamel and re-mineralised by saliva, and they bond firmly with the natural tooth enamel.
EP-A-89 900 578.9 relates to a tooth filling material composed of calcium phosphate compounds which have a proportion of pores of 20 to 70% by volume. The essence of this publication consists in utilising the porous tooth filling material in order to enable the ions in the saliva to diffuse into the cavity filled with the porous hydroxylapatite body and to allow solid calcium phosphate to form there which will largely resemble the tooth enamel in terms of its chemical composition and crystalline structure.
DE-A-3 935 060 describes a ceramic material for tooth fillings and -crowns based on calcium phosphate compounds in which the atomic ratio of calcium to phosphorus of the calcium phosphate compounds is in total less than 1.65. These ceramic materials are produced either by grinding a mixture of a calcium phosphate compound of poor solubility with an easily soluble calcium phosphate compound, or by precipitating an aqueous solution of calcium- and phosphate compounds followed by sintering at 800 to 1400.degree. C. Similar materials and methods for use as tooth filling material, dental cement or dental bonding agents are also described in DE-A-4 302 072. However, these known manufacturing methods have considerable drawbacks since even slight deviations in the method parameters, such as reaction time or reaction temperature, can lead to very different reaction products, and the reaction conditions can be considerably impaired in respect of sintering capability and corrosion properties due to these slight deviations. As a result, with the known methods, wherein the pH-value shifts in the reaction solution so that at the end of the reaction it is 7, there cannot be any reproducible product quality, and the methods cannot therefore be carried out successfully on an industrial scale.
The problem which forms the basis of the invention is therefore to obtain a method of producing a ceramic material which can be used in dental medicine and which has properties similar to those of natural tooth enamel, which results in a product quality well able to be reproduced and which therefore can also be used for production on an industrial scale. This problem is solved by way of the method according to claim 1.
This method according to the invention for producing a ceramic material based on calcium phosphate compounds for use in dental medicine by adding a phosphate solution to a calcium salt solution, separating off the precipitate formed in the reaction solution from the mother liquor, drying, crushing and sintering is characterised in that at least one orthophosphate and at least one diphosphate, each in solution, are added to the calcium salt solution, wherein the molar ratio of diphosphate to orthophosphate is in the region of 0.001 to 0.03:1, and keeps the pH-value of the reaction solution in which the precipitation is formed in the region of 7.5 to 12.
With the known methods, when heating up takes place during the sintering operation, a certain amount of diphosphate first of all forms from which tricalcium phosphate occurs when further heated. However, the amount of diphosphat
REFERENCES:
patent: 3012852 (1961-12-01), Nelson
patent: 3473889 (1969-10-01), Shen
Dunn Michael L.
Koslow C. Melissa
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