Simulation method for visualizing density of jawbone for...

Dentistry – Prosthodontics – Holding or positioning denture in mouth

Reexamination Certificate

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C433S068000, C433S215000

Reexamination Certificate

active

06224373

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a simulation method for visualizing in three dimensions the density of a jawbone at the contact area between the jawbone and the surface of an implant screw using a virtual implant screw and based on information about the density of the jawbone obtained through computed tomography (CT) and also relates to a computer readable medium therefor.
2. Description of the Related Art
For the case where damage to teeth is too serious to repair, surgery for substituting artificial teeth for damaged teeth has become common. For such surgery, an implant screw for supporting the artificial teeth must be inserted into the jawbone.
FIGS. 1A through 1G
illustrate each step of implantation. In detail, in the case where a tooth is damaged due to damage as shown in
FIG. 1A
, an artificial tooth is implanted into the damaged region as follows. The gum in the damaged region is cut as shown in
FIG. 1B
, a region into which an implant screw is to be inserted is drilled to form a hole as shown in
FIG. 1C
, and the implant screw is inserted into the hole as shown in FIG.
1
D. Then, the implanted region is left to allow the implant screw to firmly bind, or osseointegrate, with the jawbone as shown in FIG.
1
E. Usually, osseointegration takes about six months for the maxilla and about three months for the mandible. When the implant screw has firmly bound to the jawbone, the gum on the top of the implanted region is separated as shown in FIG.
1
F and then an artificial tooth is mounted on the implant screw.
However, if a dentist fails to insert the implant screw into an appropriate region in an accurate direction during the above surgery, the implant screw cannot satisfactorily support the artificial tooth or the inappropriately inserted implant screw may encroach on alveolar nerves, causing numbness. Thus, the most important step in implantation is to accurately assess the density of the jawbone in the vicinity of a desired implantation location. In particular, contact between the implant screw and a low-density area and particularly encroachment on the nerves in the jawbone should be avoided.
Success in implantation depends on how accurately a dental surgeon knows the jawbone quality of a patient. The current leading method in accurately ascertaining the jawbone quality is computed tomography (CT). CT is a process by which an object is scanned by X-ray in many directions and synthesized through computation, resulting in an image of intersection. At a dental surgery, during CT scanning, either the maxilla or the mandible is typically scanned in 1.0 -mm increments, resulting in about 45 image slices.
FIG. 2
shows a three-dimensional reconstruction image of a mandible obtained by CT.
As shown in
FIG. 2
, the images provided by CT are at intersections perpendicular to the long axis of the cervical spine, and these images are not suitable for inspecting the contact area between the implant screw and the jawbone. This is why a reformatting technique is applied after the images have been scanned by CT. In general, the most prevalent reformatting orientation is coronal, or perpendicular to the ramus of the mandible, or jawbone. However, because the jawbone is arch-shaped, the actual reformatted images may not be parallel to each other. Also, images perpendicular to the jawbone as well as images perpendicular to the cervical spine are very helpful in examining an implant site. Unfortunately, images perpendicular to the jawbone do not display the density distribution of the jawbone in a three-dimensional view, so that an implant surgeon cannot fully observe the density of jawbone at the contact area between the implant screw and the jawbone.
Due to the complicated three-dimensional structure of the jawbone, it is difficult to accurately observe an implant site in the jawbone from only the intersection image perpendicular to the cervical spine. This is the reason why CT software for dentist's provides a function capable of viewing the jawbone at different angles. For example, as the most common function of the CT software, a user can obtain a vertical sectional image by only drawing a parabola on a desired region of a given intersection, the vertical image corresponding to the desired region. However, using only the planar intersection (tomographic) images in identifying the density of a jawbone having a three-dimensional structure is not suitable for precise implantation.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide a simulation method for visualizing the density of a jawbone in three dimensions, at the contact area between an implant screw and the jawbone, for implantation of the implant screw for supporting an artificial tooth in the jawbone, and a computer readable medium for the simulation method.
According to an aspect of the present invention, there is provided a simulation method for visualizing the density of a jawbone at an implant area into which an implant screw for supporting an artificial tooth is inserted, comprising the steps of: (a) forming a three-dimensional image of the jawbone, the image including information about the jawbone density; (b) setting a color map corresponding to the density distribution of the jawbone; (c) modeling a virtual implant screw on a plurality of brick elements; (d) inserting the virtual implant screw into a surgical area of the jawbone image; (e) calculating values of the jawbone density at the points where each brick element of the virtual implant screw contacts the jawbone; and (f) searching for colors in the color map corresponding to the density values of each brick element, and coloring faces of the virtual implant screw.
The invention can also be embodied as computer readable code on a computer readable medium. The computer readable medium is any data storage device that can store data which can be thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, magnetic tape, floppy disks, optical data storage devices. The computer readable medium can also be distributed over a network computer system so that the computer readable code is stored and executed in a distributed fashion.
According to another aspect of the present invention, there is provided a computer readable medium containing program instructions for visualizing the density of a jawbone at an implant area into which an implant screw for supporting an artificial tooth is inserted, the computer readable medium comprising: computer readable code for forming a three-dimensional image of the jawbone, the image including information about the jawbone density; computer readable code for setting a color map corresponding to the density distribution of the jawbone; computer readable code for modeling a virtual implant screw on a plurality of brick elements; computer readable code for inserting the virtual implant screw into a surgical area of the jawbone image; computer readable code for calculating values of the jawbone density at the points where each brick element of the virtual implant screw contacts the jawbone; and computer readable code for searching for colors in the color map corresponding to the adjacent density values of each brick element, and coloring faces of the virtual implant screw.


REFERENCES:
patent: 4575805 (1986-03-01), Moermann et al.
patent: 5320529 (1994-06-01), Pompa
patent: 5342202 (1994-08-01), Deshayes
patent: 5725376 (1998-03-01), Poirier
patent: 6049743 (2000-04-01), Baba
patent: 0 180 482 A2 (1986-05-01), None
patent: 0 180 482 A3 (1988-07-01), None
Copy of European Search Report for Applicants' corresponding European Patent Application No. EP 99 30 7302 (three pages).
Seipel, et al., Oral implant treatment planning in a virtual reality environment,Computer Methods and Programs in Biomedicine, vol. 57, No. 1-2, 1998, pp. 95-103.
Rosenfeld and Mecall, Use of prosthesis generated computed tomographic information for diagnosis and surgic

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