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Fixture

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20120264084 patent thumbnailZoom

Fixture


The present invention relates to a fixture for insertion into a bore hole arranged in bone tissue, comprising a threaded leading portion and a threaded trailing portion located coronally of the leading portion.

Inventors: Stig HANSSON, Anders HALLDIN
USPTO Applicaton #: #20120264084 - Class: 433174 (USPTO) - 10/18/12 - Class 433 
Dentistry > Prosthodontics >Holding Or Positioning Denture In Mouth >By Fastening To Jawbone >By Screw

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The Patent Description & Claims data below is from USPTO Patent Application 20120264084, Fixture.

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TECHNICAL FIELD

The present invention relates to a fixture for insertion into a bore hole arranged in bone tissue, the fixture comprising a threaded outer surface for engagement with the bone tissue.

BACKGROUND OF THE INVENTION

A frequent way today to restore a damaged limb, such as lost tooth, is to install a fixture in the adjacent bone tissue and replace the damaged parts. In this respect, for a successful result, the fixture should become fully stable and correctly joined to the bone. The term osseointegration is used for this joining effect, the basic meaning of this term being the bone tissue growth into the fixture surface. The two major contributors to this joint are a mechanical joint and an organic joint. The former being generally influenced by the macro geometry of the bore into which the fixture is installed, and by the macro geometry of the fixture, and is a direct effect of how well these two work together. The latter one being a continuously evolving and developing effect, particularly during the time immediately after installation, and being generally influenced by how well the micro surface structure of the fixture interacts with the bone tissue.

Due to ingrowth there will be an interlocking effect between the bone and the fixture. Also, the mechanical joint is developed over time since the bone tissue, under ideal conditions, may grow into surface cavities of the fixture, and grow into voids left between the fixture and the bore after installation.

It is furthermore relevant to obtain both a good initial (primary) fixation and a good long-term fixation of the fixture in bone.

There is a continuous endeavour in the industry to further increase the stability of fixtures implanted in bone tissue and to improve the basic conditions during the healing phase after fixture installation. One example is the provision of the fixture surface with different types of structures, such as micro-roughened or blasted structures for increasing the contact surface between the fixture and the bone.

Nevertheless, there is still room for further development of fixtures as regards their stability in bone tissue.

SUMMARY

OF THE INVENTION

An object of the present invention is to provide a dental fixture which has a high stability during the healing phases of the fixture. This and other objects, which will become apparent in the following, are accomplished by means of a dental fixture as defined in the accompanying claims.

According to a first aspect of the present invention, a dental fixture for insertion into a bore hole arranged in bone tissue is provided. The dental fixture comprising a threaded leading portion and a threaded trailing portion located coronally of the leading portion,

wherein the threading of the leading portion has at least one first thread spiral,

wherein the threading of the trailing portion has at least one more thread spirals than the threading in the leading portion,

wherein the threading of the trailing portion and the threading of the leading portion have the same or substantially the same lead,

wherein the profile of at least one of the thread spirals in the trailing portion is, at least along a portion of its extension, substantially the same as the profile of the outermost part of said first thread spiral in the leading portion, and

wherein the at least one thread spiral in the trailing portion having substantially the same profile as the outermost part of said first thread spiral in the leading portion is arranged to follow the spiral path of said first thread spiral.

A dental fixture being provided in the manner described above will provide both a good primary fixation and a good long-term fixation of the fixture in the bone.

By profile of the thread is meant to understand the contour or outline of the thread. Hence, for two threads to have substantially the same profile, the characteristics defining the outer contour of the thread should be similar to each other.

With outermost parts of a thread spiral is meant to understand a part of the thread spiral from the top of the thread towards the thread bottom. The amount of the thread belonging to the outermost part may vary. It may in fact, in those cases where the minor diameter of the macrothreaded section and the microthreaded section is the same, be the entire thread. However, when the minor diameter of the microthreaded section is larger than the minor diameter of the macrothreaded section, the entire macrothread will not be considered to be the outermost part. Instead, the portion of the macrothread belonging to the outermost part is the portion being situated further away from the central axis of the implant, as compared to the distance between the central axis of the implant and the minor diameter of the microthreaded portion. Furthermore, there exist embodiments where there is a curved transition between the threads, i.e. the thread has a bottom radius. In those embodiments, the outermost part of the macrothread is considered to be the part of the macrothread being situated further away from the central axis of the implant than the bottom radius portion of the microthread.

When the fixture is inserted into a bore, said first thread of the leading portion will either create a path in the case of a self-tapping fixture or follow a path in the case of a pre-tapped hole through the cortical bone and into the cancellous bone. Since one of the thread spirals in the trailing portion is synchronized with said first thread spiral in the leading portion, the thread spiral in the trailing portion will follow the same spiral path through the bone.

By providing at least one of the thread spirals in the trailing portion, i.e. the thread spiral following the path of said first thread spiral in the leading portion, with a similar or substantially the same geometrical profile as said first thread spiral in the leading portion, at least along a portion of its length, the female threading in the bone will be filled with threads throughout the length of the fixture, or at least for the portions where the profiles are substantially the same. Hence, the fixture will be supported by thread spirals being in contact with the bone throughout at least a large portion of the length of the implant.

The thread spirals in the trailing section are primarily engaged with the hard cortical bone once the fixture has been inserted. By providing more thread spirals at the trailing section, the area of the threads being engaged with the bone increases, as compared to a section having fewer thread spirals. This may be beneficial in terms of improving the initial stability of the implant in the bone.

It may for certain embodiments be an advantage with not providing the entire thread spiral with a thread having substantially the same profile as the first thread spiral. The potential advantage is that it provides for the possibility to e.g. create blood chambers or condensation of the bone at selected positions along the implant. According to one exemplary embodiment, the thread profile is provided so that blood chambers become positioned substantially on the coronal side of the threading. By this, the threads will be in contact with bone on their apical side, hence providing support for the implant when it is impacted by forces from e.g. chewing.

According to one exemplary embodiment, the thread spiral following the path of said first thread spiral in the leading portion has substantially the same profile as said first thread spiral in the leading portion along its entire length. By this, the path of the female threading in the bone in which the thread at the leading portion travels will be filled with threading throughout the length of the fixture. Hence, the fixture will be supported by thread spirals being in contact with the bone throughout the length of the implant. This provides for a good initial stability and a good ability to carry loads and distribute these loads to the bone in a beneficial manner.

The thread spiral following the path of said first thread spiral in the leading portion may, but need not be, continuous with the first thread spiral in the leading portion. Furthermore, the leading and trailing portions of the implant may, but need not be, positioned adjacent each other. It is for example conceivable with another threaded portion between the leading and trailing portion. It is also conceivable with a non-threaded surface between the leading and trailing portion. The non-threaded surface may e.g. be smooth or roughened.

According to at least one exemplary embodiment, the thread spiral in the trailing portion that follows the path of said first thread spiral in the leading portion has the same radius of curvature at the top of the peaks as said first thread spiral. The radius of curvature at the top of the peaks is a geometrical characteristic that influences the profile of the thread.

According to at least one exemplary embodiment, the thread does not have a curvature at the top of the peak. Instead, the top may have a straight extension.

According to at least one exemplary embodiment, the thread spiral in the trailing portion that follows the path of said first thread spiral in the leading portion has the same flank angles, respectively, as said first thread spiral. The flank angles are a geometrical characteristic that influences the profile of the thread.



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Previous Patent Application:
Device and method intended for holding a prosthesis in dental implantology
Next Patent Application:
Fixture and a fixture set
Industry Class:
Dentistry
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stats Patent Info
Application #
US 20120264084 A1
Publish Date
10/18/2012
Document #
13444975
File Date
04/12/2012
USPTO Class
433174
Other USPTO Classes
International Class
61C8/00
Drawings
10



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