Compositions: coating or plastic – Coating or plastic compositions – Dental
Patent
1995-08-24
2000-11-28
Koslow, C. Melissa
Compositions: coating or plastic
Coating or plastic compositions
Dental
501 1, 423312, 423314, 423315, 423305, 264 84, C04B 3564, A61K 6033
Patent
active
061530026
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention concerns a ceramic material for fillings and/or dental prostheses and a method for the manufacture of such a ceramic material.
Different materials are known for the elimination of especially carious defects in the dental enamel and for the manufacture of dental prostheses, such as inlays, crowns and bridges. Widespread are amalgams, plastics and precious metals (for example gold). Each of these materials has specific disadvantages. Allergies can occur (amalgam), the mechanical properties are insufficient (plastics), or the costs are unusually high (gold).
In order to eliminate the aforementioned disadvantages, one seeks a material that is a similar as possible to natural dental enamel. Therefore, calcium phosphate compounds, especially hydroxylapatites, were developed. As concerns color and mechanical properties they closely approximate natural dental enamel. However, they have the disadvantageous characteristic that their surfaces become rough with time. With increasing fracturing of the surface, hydroxylapatite is removed more quickly (demineralisation). Although so-called bio-active hydroxylapatities were developed, which have a remineralisation property that reverses demineralisation to the greatest extent, to avoid or delay such removal, such materials have never made it past the laboratory stage. This is associated with the face that they must possess specific parameters that do not permit mass production owning to insufficient reproducibility.
On this basis, it is the object of this invention to create a ceramic material for fillings and dental prostheses that shows a reliable remineralisation behavior. It is further the object of tis invention to create a method which facilitates the simple and reliable manufacture of the ceramic material that possesses the remineralisation properties.
The ceramic material to solve this task has features owning to the formation of the ceramic material from separate phases or crystals of different materials on the one hand and the formation of a phase or crystal from an freely soluble substance, a targeted demineralisation is achieved. In the main, uniformly patterned cavities are formed in the calcium phosphate compounds that form the actual filling or the actual dental prosthesis. The calcium phosphate compounds thus receive a specific porosity. The size of the pores and the proportion of pores of the total ceramic material can be controlled by the respectively more freely soluble substance or compound. Thus a lattice is created that can be specifically predetermined as concerns its structure and free spaces. This allows conditions to be created in the ceramic material that guarantee an optimum remineralisation.
It has proven especially advantageous to select an non-stoichiometric ratio between individual phases or crystals.
Preferably the more freely soluble substances or compounds are those that are soluble in acid. The dissolving out of the corresponding crystals can thus be controlled in a targeted way through the creation of acidic conditions in the mouth, especially in the saliva. This can be promoted in that the patient has an acidic pH value or sucks a lozenge that creates an acidic pH value in the mouth.
Preferably the freely soluble substance or compound is an alpha and/or beta tribasic calcium phosphate (whitlockite, i.e., tribasic calcium phosphate in either the alpha- or beta-crystal form) or a mixture of both. This is easily formed during the manufacture of the other phase, namely the calcium phosphate compound and accommodated in the form of sorted crystals distributed evenly in the ceramic material.
Preferably crystals comprising alpha and/or beta tribasic calcium phosphate are deposited in the crystals and/or free spaces between neighboring crystals of the calcium phosphate compound. The alpha and/or beta tribasic calcium phosphate thus forms "placeholders" in the ceramic material according to this invention which after the dissolving away of the alpha and/or beta tribasic calcium phosphate cause the desired porosity.
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REFERENCES:
patent: 4097935 (1978-07-01), Jarcho
patent: 5017518 (1991-05-01), Hirayama et al.
Gundlach Hans-Werner
Wiedemann Wolfgang
Koslow C. Melissa
Schindler Edwin D.
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