Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis
Reexamination Certificate
2002-08-06
2004-05-11
Lechert, Jr., Stephen J. (Department: 1732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
C264S113000, C264S122000, C264S123000, C264S308000
Reexamination Certificate
active
06733528
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a three-dimensional implant.
Conventionally, when a body of bone, for example bones of skull, cheek bone, jaw bone or the like is partially lost, implants made of artificial material are filled in the defected part, and fixed thereat.
In conventional art, the implants are typically formed as follows.
Firstly, using a two-dimensional CT, an image of a remainder of a body of bone having a defected portion is captured. Then, based on the thus captured image, a model corresponding to the remainder is formed. Next, using paper-mache pulp or the like, a model of the defected portion is made. Then, using the model of the defected portion thus formed, a female mold made of resin is formed. Then, using the female mold, a male mold is created.
Then, the male mold and a block of hydroxyapatite (HAp) are set in a copying machine, an implant as desired is formed.
When implants are formed in accordance with the forming method described above, if an implant includes a void having a complicated shape, it is sometimes difficult or substantially impossible to form an implant having a desired shaped.
Further, according to the conventional method, a relatively long time period is required for forming an implant, and it may be difficult to supply an implant for an emergency surgery.
SUMMARY OF THE INVENTION
The present invention provides an advantage in that an improved method for manufacturing an implant having a complicated shape relatively easily with a high degree of accuracy.
According to the invention, there is provided a method for forming an implant having a desired shape, which includes (a) forming a layer of ingredient powder having a predetermined thickness composed of an ingredient powder, and (b) applying an reactant liquid to the layer in accordance with the desired shape of the implant, portions of the ingredient powder reacting with the reactant liquid being hardened. It should be noted that the steps of forming and the applying are repeated to stack a plurality of the layers having hardened portions, respectively, to form a three-dimensional implant formed by a stack of the hardened portions of the layers of the ingredient powder. The ingredient powder is a powder including at least one of a-tricalcium phosphate and tetracalcium phosphate, and a Ca/P ratio of the powder is within a range of 1.40 through 2.0.
In accordance with the above method, an implant having a complicated shape can be formed relatively easily within a very limited period in time with a high dimension of accuracy.
Optionally, the ingredient powder may be a powder containing a-tricalcium phosphate, tetracalcium phosphate and calcium hydrogen phosphate, and the Ca/P ratio of the ingredient powder is within a range of 1.40 through 1.80.
According to the embodiment, the step of hardening does not add a binder.
Optionally, the method includes a step of removing the unhardened ingredient powder after the steps of forming and the hardening have been finished.
Further optionally, the reactant liquid is at least mainly composed of water, or pure water.
Still optionally, the ingredient powder may produce apatite when reacts with the reaction liquid.
Further, the mean particle size of the ingredient powder may be within a range of 5 &mgr;m through 40 &mgr;m.
Optionally, the mean thickness of the layer of the ingredient powder may be within a range of 0.1 mm through 0.5 mm.
Furthermore, the reaction liquid may be blown to the layer of ingredient powder in a form of drops.
Preferably, the porosity of the implant, which is formed in accordance with the above method, is within a range of 10 through 90 vol %.
According to another aspect of the invention, there is provided a method for forming an implant having a desired shape, which includes (a) forming a layer of ingredient powder having a predetermined thickness composed of an ingredient powder, and (b) applying an reactant liquid to the layer in accordance with a cross-sectional shape of the implant corresponding to a currently processed layer, portions of the ingredient powder reacting with the reactant liquid being hardened. The steps of forming and the applying are repeated with shifting a level of the layer so as to stack a plurality of the layers having hardened portions are formed one by one to form an implant formed by a stack of the hardened portions of the layers of the ingredient powder. The ingredient powder is a powder including at least one of a-tricalcium phosphate and tetracalcium phosphate, and a Ca/P ratio of the powder is within a range of 1.40 through 2.0.
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English Language Abstract WO 00/71178.
“A Comparison of the Shapes of Hydroxyapatite Implants Before and After Implantation”, Abe et al., published on Apr. 3, 2002 in Wiley InterScience <www.interscience.wiley.com>.
Abe Keita
Nakasu Masanori
Ono Ichiro
Greenblum & Bernstein P.L.C.
Lechert Jr. Stephen J.
PENTAX Corporation
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