Dentistry – Method or material for testing – treating – restoring – or... – Endodontic
Reexamination Certificate
2000-05-30
2001-08-21
Lewis, Ralph A. (Department: 3732)
Dentistry
Method or material for testing, treating, restoring, or...
Endodontic
C433S173000
Reexamination Certificate
active
06276939
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an artificial tooth and its production method.
BACKGROUND ART
A new tooth does not grow back after a permanent tooth has come out or been extracted.
Under the present circumstances, a substitute for a tooth root made of alumina ceramics, titanium and so forth is embedded in the mandibula or the maxilla, and an artificial crown molded into the shape of the crown of the target tooth is joined and fixed on top of said root substitute to be used in place of the tooth.
In the case of this method, however, since said root substitute is directly joined and fixed to the mandibula or the maxilla, there is the problem of said artificial tooth coming out as a result of being unable to withstand the repeated load applied to said artificial tooth (as a result of the patient repeatedly biting with said artificial tooth).
On the other hand, in the case of transplanting a permanent tooth, there are reports (from both animal experiments and clinical cases) of the permanent tooth taking in cases of transplanting one of the patient's own permanent teeth to another location in the patient's mouth, or so-called autotransplantation.
However, this method is limited to application to wisdom teeth only.
In addition, there have been no reports of successful cases of homoplastic or heteroplastic transplantation.
DISCLOSURE OF INVENTION
In order to improve on the current situation, the object of the present invention is to provide an artificial tooth and its production method that is not required to be joined directly to the mandibula or the maxilla, and an artificial tooth and its production method that allows both homoplastic and heteroplastic transplantation.
The inventors of the present invention determined that the reason why previous homoplastic and heteroplastic transplantations have not been successful is due to the inability to skillfully regenerate the periodontal ligament, dental pulp, nerves and blood vessels, and particularly the periodontal ligament, for transplanted artificial teeth, thereby leading to completion of the present invention.
Namely, the present invention is an artificial tooth that uses a homoplastic or heteroplastic artificial tooth from which cellular components of periodontal ligament, nerve and blood vessel have been removed, said artificial tooth having a layer in which extracted collagen is filled into the root canal(s), and a membrane of extracted collagen on the surface of the root having on top of it a periodontal ligament from which said cellular components have been removed.
Here, the phrase “from which cellular components of periodontal ligament, nerve and blood vessel have been removed” refers to the complete removal of cellular components originating in said permanent tooth that demonstrate antigenicity or are strongly antigenic from a homoplastic or heteroplastic permanent tooth that serves as the base for the artificial tooth. Since periodontal ligament removed of said cellular components, and namely periodontal ligament containing residual connective tissue present in the manner of digging vertically in the cementum of said permanent tooth, provides a foothold until regeneration of the periodontal ligament of the patient receiving transplant, along with a membrane of extracted collagen formed on top of it (which penetrates into the periodontal ligament from which said cellular components have been removed, in it's formation process), it is critically important to leave said periodontal ligament from which said cellular components have been removed to contribute to regeneration of the periodontal ligament. Furthermore, although there are many cases in which nerves and blood vessels are attached to said sampled permanent tooth, the cellular components contained therein are incidentally removed when performing removal of cellular components in said periodontal ligament. Different from periodontal ligament in which extracellular components have been intentionally allowed to remain, extracellular components of nerves and blood vessels may also be completely removed at this time.
In addition, the above-mentioned homoplastic or heteroplastic permanent tooth is an artificial tooth composed of a molded body, having a shape at least equivalent to the root and comprised of hydroxyapatite having a lumen equivalent to the root canal inside, and extracted collagen present in the gap between them, and may be an artificial tooth having a layer in which extracted collagen is filled into said lumen along with a membrane of extracted collagen on the surface of said portion equivalent to the root. This is because, although the degree of perfection of regeneration is relatively low with respect to the point of not having a periodontal ligament from which cellular components that contribute to regeneration of the periodontal ligament of the patient receiving transplant have been removed, with respect to other points, namely since necessary steps required for regeneration of the periodontal ligament of the patient receiving transplant as well as nerves and blood vessels have been taken, the object of providing an artificial tooth that is not required to be directly joined to the manndibura or the maxilla can be sufficiently achieved. Furthermore, hydroxyapatite is only selected because it is a material that is currently recognized to have the desired strength and have excellent biocompatibility. Thus, a material other than hydroxyapatite can naturally also be used provided it has strength and demonstrates biocompatibility that are greater than those of hydroxyapatite.
Furthermore, the extracted collagen layer, which is formed as a result of being filled into the root canal or lumen that is equivalent to said root canal, provides a foothold for regeneration of nerves and blood vessels of the patient receiving transplant for the transplanted artificial tooth. In addition, the extracted collagen layer formed on the surface of the root or portion equivalent to the root provides a foothold for regeneration of the periodontal ligament of the patient receiving transplant.
Thus, growth factors such as b-FGF and so forth may be additionally contained in said layer in which extracted collagen is filled and/or said membrane of extracted collagen. This is because the rate of their regeneration is accelerated.
Here, the term “extracted collagen” refers to type I collagen or a mixture of type I and type III collagen that is solubilized using acid, base or enzyme and so forth from a raw material such as skin, bone, cartilage, tendon or organs of various animals such as cows, pigs, rabbits, sheep, kangaroos or birds, while the term “their layer or membrane” refers to that having an amorphous structure in which collagen molecules are dispersed. Extracted collagen retains the inherent properties of collagen, namely excellent bioaffinity, tissue compatibility and promotion of tissue regeneration. Moreover, since antigenic groups in the form of telopeptides are removed in the solubilization procedure, it is a preferable material for the object of the present invention.
On the other hand, the above-mentioned artificial tooth can be produced in the manner described below.
In the case of using a permanent tooth sampled from a homoplastic or heteroplastic body as the base of an artificial tooth, said permanent tooth is washed with surface activator (preferably a non-ionic surface activator that is a polyoxyethylene derivative, typical examples of which include Triton X-100, Lubrol PX and members of the Tween series), and cellular components of the periodontal ligament, the nerves and blood vessels of said permanent tooth are removed (at least the extracellular components of the periodontal ligament remain). Next, extracted collagen is filled into the root canal of said permanent tooth and a membrane of extracted collagen is formed on the surface of the root having on top of it a periodontal ligament from which said cellular components are removed.
Here, washing of said tooth with surface activator is specifically performed by immersing for 1
Inoue Masatoshi
Shimizu Yasuhiko
Yamamoto Yasumichi
Corless Peter F.
Edwards & Angell LLP
Lewis Ralph A.
Yasuhiko Shimizu
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