Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1995-05-30
2001-04-10
Isabella, David J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S023720, C623S023610
Reexamination Certificate
active
06214048
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a bone substitute product, such as a material, a sheet, and a method of manufacturing the same. In particular, the bone substitute product is useful in dental, orthopedic, and plastic surgery fields as a filling or cushioning material for root canal filling, bone filling, a tooth support in pyorrhea alveolaris, and so on.
A bone substitute material of the type described is known which comprises a hardenable composition containing chitosan. The chitosan is well-known in the art as a natural abundant macromolecule. Such a hardenable composition is disclosed in Japanese Patent Prepublication No. 22026/1977. In order to manufacture the hardenable composition, an acidic aqueous solution of chitosan should be mingled or mixed with a basic water-hardenable inorganic material because the chitosan itself has a low solubility under a basic state or a non-acid state. As the basic water-hardenable inorganic material, use has generally been made of lime, Portland cement, alumina cement, or the like. The resultant composition is not lower than 9 in the pH value.
However, the above-mentioned conventional hardenable composition is improper for use in a human body because of such a high pH value.
Another conventional hardenable composition is disclosed in Japanese Patent Prepublication No. 208347/1989. The hardenable composition is manufactured by a mixture of an acidic aqueous solution of chitosan, particulate hydroxyapatite, zinc oxide and/or magnesium oxide. Due to presence of such hydroxyapatite, the hardenable composition exhibits an excellent affinity to a tooth and a bone and is hardened within a neutral range.
However, a very long time is required to create a bone when this hardenable composition is used as a bone substitute material.
In a dental field, dental cements have been extensively used for cementation of a restorative material, a temporary filling material, a root canal filling material, and so on. For example, as the dental cements, known are zinc phosphate cement, zinc oxide eugenol cement, and carboxylate cement. Such dental cements are prepared by mingling powder components and liquid components immediately before application and then hardened after lapse of 4 to 10 minutes.
However, such a dental cement has a pH value between 2 and 4 when a mixture of the powder component and the liquid component is prepared in the form of paste. In other words, the dental cement is acidic. When the dental cement is used in a human body for cementation, as mentioned above, dental pulp may be injured (inflammation, stimulation, and so on).
Consideration may be made as regards using the particulate apatite as a bone filling material. However, the particulate apatite often causes inflammation to occur in a gingiva. Specifically, the particulate apatite often migrates from an initial implant site and enters between a bone and the gingiva. This brings about inflammation in the gingiva under an occlusal pressure.
In addition, the hardenable composition containing the particulate apatite is not effective in creation of a bone because the particulate apatite is often migrated to be lost from the implant site.
SUMMARY OF THE INVENTION
It is therfore an object of this invention to provide a bone substitute product which is harmless and not toxic for organisms and which is quickly hardened in a neutral range after completion of chemical reaction.
It is another object of this invention to provide a bone substitute product which can avoid incidence of inflammation in a gingiva under the occlusal pressure and which is excellent in an ability of creating a bone.
It is still another object of this invention to provide a bone substitute product which will expect a wide variety of uses in a dental treatment.
It is yet another object of this invention to provide a method of producing a bone substitute product of the type described.
According to an aspect of this invention, there is provided a bone substitute material formed by kneading a powdery mixture of animal bone powder and a divalent metal compound together with chitosan sol which is prepared by dissolving chitosan by acid.
According to another aspect of this invention, there is provided a method of manufacturing a bone substitute material, the method comprising the steps of firing animal bones to leave inorganic components alone, pulverizing the animal bones into animal bone powder, mixing the animal bone powder and a divalent metal compound at a predetermined mixing ratio to make a powdery mixture, and kneading the powdery mixture with chitosan sol prepared by dissolving chitosan with acid.
According to still another aspect of this invention, there is provided a method of manufacturing a bone substitute material, the method comprising the steps of firing animal bones to leave inorganic components alone, pulverizing the animal bones into animal bone powder, mixing the animal bone powder, chemically synthesized apatite, and a divalent metal compound at a predetermined mixing ratio to form a powdery mixture, and kneading the powdery mixture with chitosan sol prepared by dissolving chitosan with acid.
According to yet another aspect of this invention, there is provided a bone substitute sheet manufactured by neutralizing a pre-processed sheet which comprises a mixture of apatite and chitosan sol prepared by dissolving chitosan with acid.
According to a further aspect of this invention, there is provided a bone substitute sheet manufactured by neutralizing a pre-processed sheet which comprises a mixture of animal bone powder and chitosan sol prepared by dissolving chitosan in acid.
According to another aspect of this invention, there is provided a method of manufacturing a bone substitute sheet, the method comprising the steps of mixing apatite with chitosan sol prepared by dissolving chitosan in acid to form a mixture of the apatite and the chitosan sol, shaping the mixture into a pre-processed sheet, and neutralizing the pre-processed sheet into the bone substitute sheet in an aqueous solution of a compound which contains at least one element selected from monovalent and divalent metal elements.
According to still another aspect of this invention, there is provided a method of manufacturing a bone substitute sheet, the method comprising the steps of firing animal bones to leave inorganic components in the fired animal bones, pulverizing the inorganic components into animal bone powder, mixing the animal bone powder with chitosan sol prepared by dissolving chitosan in acid to form a mixture of the animal bone powder and the chitosan sol, shaping the mixture to form a pre-processed sheet, and neutralizing the pre-processed sheet into the bone substitute sheet in an aqueous solution of a compound which contains at least one element selected from monovalent and divalent metal elements.
According to yet another aspect of this invention, there is provided a method of manufacturing a bone substitute sheet, the method comprising the steps of firing animal bones to leave inorganic components alone, pulverizing the fired animal bones into animal bone powder, mixing apatite, the animal bone powder, and chitosan sol prepared by dissolving chitosan in acid, to form a mixture of the apatite, the animal bone powder, and the chitosan sol, shaping the mixture into a pre-processed sheet, and neutralizing the pre-processed sheet into the bone substitute sheet in an aqueous solution of a compound which contains at least one element selected from monovalent and divalent metal elements.
REFERENCES:
patent: 4772591 (1988-09-01), Meisner
patent: 5167961 (1992-12-01), Lussi et al.
patent: 5180426 (1993-01-01), Sumita
patent: 5223029 (1993-06-01), Oonishi et al.
patent: 5290558 (1994-03-01), O'Leary et al.
patent: 0329098 (1989-02-01), None
patent: 0 329 098 (1989-08-01), None
patent: 2 101 036 (1972-03-01), None
patent: 52-22026 (1977-02-01), None
patent: 1-208347 (1989-08-01), None
patent: 2 241 460 (1990-09-01), None
Stedman's Medical Dictionary, 23rdEdition, ©1976 pp. 96, 664.*
Hawley's Condensed Chemic
Ito Michio
Yagasaki Hiroshi
Foley & Lardner
Isabella David J.
Koh Choon P.
Matsumoto Dental College
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