Dentistry – Prosthodontics – Dental implant construction
Reexamination Certificate
2000-02-25
2002-06-11
Wilson, John J. (Department: 3732)
Dentistry
Prosthodontics
Dental implant construction
C433S173000, C623S023720
Reexamination Certificate
active
06402517
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an artificial tooth root selectively imparted with acid resistance and with anti-adherence of sordes and various germs in areas where a periodontal pocket is likely to occur, and to a production process therefor. More particularly, the invention relates to a novel surface treatment technique for selective surface treatment of a predetermined area of a dentistry material, which can give a properties of anti-adherence of sordes such as tobacco tar and various germs to a predetermined area of the surface of an artificial tooth root coated with calcium phosphate based ceramic having bioaffinity.
2. Description of the Related Art
Periodontal disease and similar disorders stem from infections in the space of tooth and gingival, i.e., periodontal pockets. In many cases, infection recurs due to infiltration of various germs from the area around a repaired tooth or dental crown. Kasuga et al. succeeded in imparting antibacterial properties to the surface of crystalline glass for artificial crowns by introducing silver ions by means of ion exchange (Material Integration (1999), Vol. 12, No. 5, p. 27). The resultant surface exhibits high antibacterial properties against
Escherichia coli
and
Staphylcoccus aureus.
Yoshino et al, with the aim of preventing adherence of sordes to surfaces of dentistry materials such as dental prostheses, employed a silane coupling agent with a fluorocarbon chain in order to modify the surface of a substrate (Kagaku to Kogyc(1993), Vol. 46, No. 12, p, 58). Depending on the nature of the substrate treated, the resultant surface exhibits water repellence as high as 100 to 115°, reducing adherence of sordes.
Through these methods, it has been possible to control adherence of various germs or contaminant of the dentistry materials. However, the former process, while imparting exceptional antibacterial properties, has no effect whatsoever in terms of inhibiting adherence of sordes. Surfaces treated by the latter process exhibit a water droplet contact angle of around 100 to 115°. However, with a contact angle on this order, there is 30% contact between the surface and a water droplet, so with extended use adherence of sordes occurs, and there is a deterioration of initial performance. Further, the process is decidedly not “environmentally friendly”, requiring a large number of processing steps, using copious amounts of water, using organic solvents, etc. Neither of the processes described above is readily adapted to selective surface treatment of a predetermined area.
Calcium phosphate based-ceramics have a number of advantages, such as earlier ossification than do titanium implants, and direct bonding with bone. Clinical application of these materials as dental implants is advancing. However, these ceramics have low strength and tend to be brittle, making use per se as implants difficult. Accordingly, calcium phosphate based ceramics are typically coated onto titanium or a titanium alloy by a plasma spraying process or the like for use. However, differences in the coefficient of thermal expansion between titanium or titanium alloys and the coating film give rise to residual stress, resulting in delamination from the substrate, loss of the film through dissolution of the coating film due to depressed pH in the adjacent area, and other problems; thus, over the long term, titanium implants offer greater reliability. It has been reported by Katayama et al. that depressed pH tends to occur within periodontal pockets, with pH dropping on average to around 6 (Hotei Shi (1986), Vol. 30, p. 665).
With the foregoing in view, thoroughgoing research conducted by the inventors has led to the discovery that introduction of fluorocarbon chains or long-chain alkyl groups to a predetermined area of the surface of a calcium phosphate based ceramic coating produced on a titanium or titanium alloy implant by means of plasma spraying etc., that is, to an area susceptible to formation of a periodontal pocket, appreciably improves water repellence, appreciably reduces adherence of sordes and various germs, and appreciably improves resistance to acid. The present invention was perfected on the basis of this discovery.
Specifically, the present invention provides an artificial tooth root particularly effective as a dentistry material imparted in a predetermined area of the implant with exceptional resistance to adherence of sordes and various germs, as well as with resistance to acid, and offering appreciably reduced dissolution of the calcium phosphate based ceramic in portions thereof exposed within a periodontal pocket. Further provided is a process for the production thereof.
SUMMARY OF THE INVENTION
The present invention provides an artificial tooth root having acid resistance and anti-adherence of sordes and various germs, as well as a process for the production thereof.
The invention relates to an artificial tooth root which is a dentistry material consisting of a substrate and a coating of calcium phosphate based ceramic having bioaffinity formed on the surface of this substrate, the substrate is composed of a polymer, ceramic, metal, or other material, wherein the surface of the ceramic coating on the substrate surface is endowed with a protrusion-and-recession configuration and is chemically modified, and to a production process for the artificial tooth root endowed with acid resistance and with anti-adherence of sordes and various germs, comprising the steps of forming a coating of calcium phosphate based ceramic having bioaffinity over a substrate while imparting protrusions and recessions thereto, masking an area of the ceramic coating surface of which bioaffinity is required by a material, and then fixing a silane coupling agent exclusively over a predetermined area of the ceramic coating surface, namely, an area where a periodontal pocket is likely to occur.
DESCRIPTION OF THE INVENTION
To solve the problems described above, the present invention is composed of the following technical means.
(1) An artificial tooth root with acid resistance and anti-adherence of sordes and various germs, which comprises of a substrate and a coating of calcium phosphate based ceramic having bioaffinity formed on the surface of the substrate,
the substrate is composed of a polymer, ceramic, metal, or other material,
the surface of the ceramic coating on the substrate surface is endowed with a protrusion-and-recession configuration, and is chemically modified.
(2) The artificial tooth root according to (1) above, wherein the protrusions and recessions provided to the ceramic coating surface have a ridge-to-trough distance of 50 nm or greater.
(3) The artificial tooth root according to (1) above, wherein the silane coupling agent is fixed over a predetermined area of the ceramic coating surface situated in proximity to the boundary of the gum and the dental crown, where is susceptible to bacterial infiltration and to gingivitis.
(4) The artificial tooth root according to (1) above, wherein the silane coupling agent contains a fluorocarbon chain, long-chain alkyl group, or other hydrophobic group.
(5) A method for producing the artificial tooth root with acid resistance and anti-adherence of sordes and various germs as defined in (1) above, comprising the steps of
forming a coating of calcium phosphate based ceramic having bioaffinity over a substrate while imparting protrusions and recessions thereto,
masking an area of the ceramic coating surface of which bioaffinity is required by a material,
and then fixing a silane coupling agent exclusively over a predetermined area of the ceramic coating surface, where a periodontal pocket is likely to occur.
The invention is now described in greater detail.
The most notable feature of the invention resides in the element of producing a coating of calcium phosphate based ceramic having bioaffinity layer over a titanium or titanium alloy substrate by means of a dipping process, electrophoresis, flame spraying process, plasma spraying process, or the like, and fixin
Hozumi Atsushi
Inagaki Masahiko
Kameyama Tetsuya
Nagata Fukue
Nishizawa Kaori
Agency of Industrial Science and Technology
Wilson John J.
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