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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.

The flank angle at the apical side of the thread may be similar to the flank angle at the coronal side of the thread. It is however also conceivable with different flank angles at the apical and coronal sides of the thread. 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. Hence, in this embodiment the coronal flank angle of the two threads is the same, and the apical flank angles of the two threads are the same, even if there may be different angles at the coronal and apical flanks, respectively.

According to at least one exemplary embodiment, the flanks of the threads have a straight extension.

According to at least one exemplary embodiment, the flanks of the threads have a curved extension. It is for example conceivable with flanks having a concave curvature. It is also conceivable with flanks having a convex curvature.

The different characteristics defining the profile of the thread that have been mentioned above for different exemplary embodiments may of course be combined in any suitable manners.

According to at least one exemplary embodiment, all thread spirals in the trailing portion have substantially the same profile as the outermost part of said first thread spiral in the leading portion. In this embodiment, all threads in the trailing portion are similar to and has the same thread profile as the at least one thread in the leading portion.

According to another exemplary embodiment, the profile of the thread spirals in the trailing portion are different from each other, or from one of the other thread spirals in case of more than two thread spirals. Characteristics of the thread spiral defining its profile is e.g. thread height, curvature radius at the top of the thread (if any), flank angle, flank extension, flank curvature, thread width, transition between adjacent threads and major diameter of the implant. By this, it is possible to e.g. provide one thread spiral that creates a blood chamber between itself and the bone, or a thread spiral that creates condensation of the bone as it is being inserted.

According to at least one exemplary embodiment, the profile of one of the thread spirals in the trailing portion, that does not follow the path of said first thread spiral in the leading portion, alters along the thread.

A thread spiral of the trailing portion that does not follow the path of a thread spiral in the leading portion will cut into the bone between the female thread path of the thread spiral or spirals of the leading portion. The thread spirals may be either self-tapping or enter into a pre-tapped bore. It may for certain embodiments be beneficial if the profile alters along the tread spiral or spirals. Characteristics of the thread spiral defining its profile is e.g. thread height, curvature radius at the top of the thread (if any), flank angle, flank extension, flank curvature, thread width and major diameter of the implant. By alternating one or more of the characteristics along the length of the thread spiral it is possible to create e.g. blood chambers between the thread and the bone at certain positions, and to create a tight fit between the thread and the bone at other positions. It is also e.g. possible to create a tight fit between the thread and the bone at certain positions and to create a condensation of the bone at other positions, or to create a fixture which alters between providing blood chambers and condensation of the bone along its length.

According to one exemplary embodiment, more than one thread spiral in the trailing portion has a different or a varying profile along the length of the respective thread spiral. It is not necessary that the characteristics of the thread spirals that vary, varies in the same manner. Hence, one of the thread spirals may e.g. be designed to create blood chambers and one of the thread spirals may e.g. be designed to create condensation of the bone.

According to at least one exemplary embodiment, the smallest spacing between adjacent peaks of the threading in the trailing portion is smaller than the smallest spacing between adjacent peaks of the threading in the leading portion.

When measuring the axial spacing between adjacent peaks, the smallest spacing between adjacent peaks in the trailing portion is smaller than the smallest spacing between adjacent peaks in the leading portion. When measuring the axial spacing between adjacent peaks, the measurement is to be taken between the tops of the peaks and not in the valleys.

If the thread in the leading portion has one thread spiral and the thread in the trailing portion has two thread spirals that are evenly distributed, the axial spacing between adjacent peaks in the trailing portion will be substantially half the distance between adjacent peaks in the leading portion. If the thread in the leading portion has one thread spiral and the thread in the trailing portion has three thread spirals that are evenly distributed, the axial spacing between adjacent peaks in the trailing portion will be approximately a third of the distance between adjacent peaks in the leading portion.

However, there also exist fixtures in which the thread spirals are not evenly distributed. There also exist fixtures being provided with a major thread being provided with minor threads at its top. In these cases, the distance between the major threads should be measured separately, and the distance between minor threads should be measured separately. Hence, one should not mix between the two different thread types in one portion of the fixture when measuring the smallest axial distance.

According to at least one exemplary embodiment, the number of thread spirals in the threaded trailing portion is a multiple integer of the number of thread spirals in the leading portion.

In order to be able to provide a thread spiral in the trailing portion following the path of a thread spiral in the leading portion, it is beneficial if the number of thread spirals in the trailing portion is a multiple integer of the number of thread spirals in the leading portion. Hence, if there is provided one thread spiral in the leading portion, the number of thread spirals in the trailing portion may be two, three, four and so on. If there is provided two thread spirals in the leading portion, the number of thread spirals in the trailing portion may be four, six, and so on. If there is provided three thread spirals in the leading portion, the number of thread spirals in the trailing portion may be six, nine, and so on.

According to one exemplary embodiment, the number of thread spirals in the threaded trailing portion is not a multiple integer of the number of thread spirals in the leading portion. It is possible to provide an implant in which the number of thread spirals in the trailing portion is not a multiple integer of the number of thread spirals in the leading portion, and in which one of the thread spirals in the trailing portion follows the path of one of the thread spirals in the leading portion. This is for example conceivable if the thread spirals are not evenly distributed, i.e. the axial distance between adjacent thread spirals differ from one another, along the length of the implant.

According to at least one exemplary embodiment, the threading in the leading portion has at least a first and a second thread spiral, and wherein one of the thread spirals in the trailing portion follows the path of said first thread spiral in the leading portion.

In those embodiments where the leading portion is provided with two thread spirals, i.e. a double thread, a first thread spiral in the trailing portion may follow the path of the first thread spiral in the leading portion.

According to one exemplary embodiment, a second thread spiral in the trailing portion may follow the path of the second thread spiral in the leading portion. These two thread spirals in the trailing and leading portion, respectively, may also have the same profile so that the female threading in the bone is being filled, thereby providing support for the fixture along the length of the implant.

According to at least one exemplary embodiment, a second thread spiral in the trailing portion does not follow the path of the second thread spiral in the leading portion.

According to at least one exemplary embodiment, the fixture is self-tapping. There exist different manners in how to provide an implant with self-tapping capabilities, it is for example possible to provide the implant with cutting means extending from the apical end into the threaded leading portion. However, it is also possible for an implant to be self-tapping even if it does not comprise any cutting means.

According to at least one exemplary embodiment, the fixture is provided with separate cutting means adapted for cutting a female thread in the bone that corresponds to the profile of at least one of the thread spirals at the trailing portion.

Providing separate cutting means at the trailing portion provides for the opportunity to cut out a female thread for the threading of the trailing portion. By this, the trailing portion may be inserted into the bone with the amount of bone being crushed during insertion being reduced.

The cutting means at the trailing portion may preferably begin at the apical end of the trailing portion, and extend coronally into the trailing portion.

According to at least one exemplary embodiment, the cutting means provided for cutting a female thread in the bone corresponding to the profile of the thread spirals at the trailing portion extends over at least one turn of all thread spirals at the trailing portion. With extending over at least one turn of all thread spirals, it is meant to understand that it extends over an axial length corresponding to the axial extension of one full rotation of the thread spirals. Hence, if the thread at the trailing portion is a double-thread, the cutting means extend over at least both threads, if the thread is a triple-thread, the cutting means extend over at least all three threads, and so on. The cutting means, may, but does not need to, extend over several rotations of each one of the thread spirals. By this, a female thread corresponding to the thread of the trailing portion will be cut in the bone and the bone will thereby not have to be subject to the strong impact that could otherwise be a risk when a thread is pressed into bone that has not been properly prepared.

According to at least one exemplary embodiment, the cutting means provided for cutting a female thread in the bone corresponding to the profile of the thread spirals at the trailing portion is provided to cut a female thread corresponding to both the outer and inner diameter of the thread at the trailing portion. By this, a female thread corresponding to the thread of the trailing portion will be cut in the bone and the bone will thereby not have to be subject to the strong impact that could otherwise be a risk when a thread is pressed into bone that has not been properly prepared.

Furthermore, depending on the configuration of the cutting means in relation to the profile of the thread in the trailing portion, e.g. the shape and minor and major diameter of the cutting means, it is possible to design fixtures in which a desired rate of condensation of the bone occurs. Obviously, a desired rate of condensation may be zero condensation.

According to at least one exemplary embodiment, the depth of the threads in the leading portion is larger than the depth of the threads in the trailing portion. A configuration according to this embodiment has proven to be beneficial in terms of load distribution to the bone, thereby providing for good initial and long-term stability of the fixture.

According to at least one exemplary embodiment, the major diameter of the fixture is similar in both the leading portion and the trailing portion.

According to at least one exemplary embodiment, the major diameter of the fixture is greater in the trailing portion than in the leading portion. By providing the trailing portion with a larger major diameter than the leading portion, a condensation of the bone surrounding the trailing portion will occur when the implant is inserted into the bone, in the case of a straight cylindrical bore hole.

According to at least one exemplary embodiment, the major diameter of the fixture is increasing in the trailing portion, as seen in apical to coronal direction. By providing the trailing portion with an increasing major diameter a gradually increasing condensation of the bone surrounding the trailing portion will occur when the implant is inserted into the bone, in the case of a straight cylindrical bore hole.

According to at least one exemplary embodiment, the fixture is further provided with a transition portion, provided between the leading portion and the trailing portion, wherein the major diameter of the fixture is increasing in the transition portion.

According to at least one exemplary embodiment, the fixture is further provided with a transition portion, provided between the leading portion and the trailing portion, wherein the minor diameter of the fixture is increasing in the transition portion.

According to at least one exemplary embodiment, the major and/or minor diameter of the fixture is continuously increasing in the transition portion.

According to at least one exemplary embodiment, at least a portion of the transition portion is provided with a threading, wherein the threading of the transition portion continues into the trailing portion.

According to at least one exemplary embodiment, the thread of the transition portion is similar to the thread of the trailing portion.

According to one exemplary embodiment, the cutting means provided for cutting a female thread in the bone corresponding to the profile of the thread spirals at the trailing portion, is provided at the transition portion.

The cutting means at the transition portion may preferably begin at the apical end of the transition portion, and extend coronally into the transition portion.

According to at least one exemplary embodiment, the cutting means provided for cutting a female thread in the bone corresponding to the profile of the thread spirals at the trailing portion extends over at least one turn of all thread spirals at the transition portion. With extending over at least one turn of all thread spirals, it is meant to understand that it extends over an axial length corresponding to the axial extension of one full rotation of the thread spirals. Hence, if the thread at the transition portion and trailing portion is a double-thread, the cutting means extend over at least both threads, if the thread is a triple-thread, the cutting means extend over at least all three threads, and so on. The cutting means, may, but does not need to, extend over several rotations of each one of the thread spirals.

According to one exemplary embodiment, the major diameter of the cutting means at the transition portion or the cutting means at the trailing portion is similar to the major diameter of the threads at the leading portion. Hence, in this embodiment, there is no increase of the major diameter of the fixture between the coronal end of the leading portion and the cutting means at the apical end of the transition portion and/or the cutting means at the apical end of the trailing portion.

According to one exemplary embodiment, the major diameter of the fixture is constant throughout the length of the cutting means at the transition portion or trailing portion. According to one exemplary embodiment, the minor diameter of the fixture is constant throughout the length of the cutting means at the transition portion or trailing portion. Hence, according to these exemplary embodiments, there is no major and/or minor diameter increase at the cutting means provided for cutting a female thread in the bone corresponding to the thread of the trailing portion of the fixture.

According to one exemplary embodiment, the major diameter increases at the transition portion, coronally of the cutting means.

According to one exemplary embodiment, the minor diameter increases at the transition portion, coronally of the cutting means.

Hence, according to either one or a combination of these exemplary embodiments, a female thread corresponding to the thread of the transition portion and/or trailing portion may be cut into the bone by the cutting means. Thereafter, when the major and/or minor diameter increases coronally of the cutting means, a controlled condensation of the bone will be achieved.

According to one exemplary embodiment, the cutting means may preferably begin at the apical end of the transition portion, and extend coronally into the transition portion.

According to at least one exemplary embodiment, the length of the transition portion is such that the transition portion extends over at least one turn of the thread, preferably at least two turns of the thread, and most preferred over at least three turns of the thread. By one turn of the thread is meant to understand one full rotation of each one of the thread spirals, in case of a multi-start thread. By this, the diameter increase will be gradual and not sudden. This is beneficial since a sudden diameter increase may affect the surrounding bone negatively during insertion of the fixture into the bone.

A dental implant may comprise a dental fixture and a superstructure, such as an abutment.

A dental fixture is for use as the anchoring member of a dental prosthesis. To this end, the dental fixture is insertable into a pre-prepared bore hole in the bone tissue of a jawbone (maxilla or mandible) at a site where the dental prosthesis is required. The dental fixture is normally rotated into the bore hole.

For screw-type dental fixtures the bore hole may be provided with internal threads in advance or may be left un-tapped with the dental fixture provided with a self-tapping capacity, e.g. by the provision of one or more axially-extending cutting recesses, edges or notches, etc in the fixture thread. For instance, an apical end portion of the fixture may be provided with 2-4 cutting recesses, such as 3 cutting recesses. Other number of cutting recesses are readily conceivable.

A superstructure for connecting a prosthetic part to the fixture may comprise an abutment, spacer or other transmusosal component which engages to the dental fixture to bridge the gingiva overlying the maxilla or mandible. The prosthetic part, e.g. a crown, bridge or denture may be secured to the abutment. There are various other forms that the superstructure can take. For instance, the prosthetic part may be secured directly to the dental fixture. A dental implant may thus comprise an abutment connected to the dental fixture, or the dental fixture without an abutment.

The term “coronal” is here and throughout this application used to indicate a direction towards a head end or trailing end of the dental implant. For instance, in a situation where an abutment is connected to a dental fixture, the coronal direction of the abutment would be a direction towards the part of the abutment being directed away from the fixture. Conversely, the term “apical” indicates a direction towards an insertion or leading end of the component. Thus, apical and coronal are opposite directions. Furthermore, the terms “axial”, “axial direction” or “axially” are used throughout this application to indicate a direction taken from the coronal end to the apical end, or vice versa. The terms “radial”, “radial direction” or “radially” indicate a direction perpendicular to the axial direction.

A blind bore or socket may extend apically into the fixture body from the coronal end to an end surface in-between the apical and coronal ends of the fixture body for a superstructure to be secured to the fixture. The socket may comprise an internally-threaded section for screw connection of the superstructure to the fixture. A rotational lock for the superstructure may be provided in the socket, such as an internal polygonal side wall, e.g. hexagonal, or alternatively one or more protrusions from or indentation in the wall of the socket. A section of the socket, such as the coronal section, may be tapered towards the apical end. The tapered section is suitably arranged coronally of the internally-threaded section.

The fixture may be used in a one stage procedure or a two stage procedure. In a one stage procedure a healing or temporary abutment is connected to the fixture to form the gingival tissue, and after a healing period the healing or temporary abutment is replaced by a permanent abutment. For a two stage procedure the fixture is provided with a cover screw and the gingival tissue is sutured over the fixture and cover screw, and after a healing period the tissue is opened up and an abutment is connected to the fixture after removal of the cover screw.

A conceivable alternative to having an abutment connected to the fixture is to have a one-piece implant, wherein a portion of the implant is embedded in bone tissue, while another portion of the implant extends from the bone tissue across the gingiva.

The fixture may have a conically tapering end portion which tapers towards the coronal end. The axial extent of this coronal end portion is small compared to the total length of the fixture, as an example no more than 4% of the total length, such as in the range of 1.5%-3.7%. The coronal end portion may suitably be provided without a threaded surface, e.g. having a smooth or a roughened (such as blasted) surface.

The fixture may have a substantially flat coronal end surface which is perpendicular to the longitudinal axis of the fixture. Alternatively, the coronal end surface may have a sloped contour relative to the longitudinal axis of the fixture, e.g. such that when positioned within the jawbone the length of the fixture is larger on a lingual side and shorter on a buccal side of the fixture. Another alternative is a saddle-shaped or wave-like coronal end surface.

The length of the dental fixture may be in the range of 5-19 mm, depending on the clinical situation. The outer diameter of the dental fixture may suitably be in the range of 2-6 mm, such as 3-5 mm.

The fixture may be substantially cylindrical or slightly tapering from the coronal end towards the apical end. If the fixture has a slight tapering, the core of the fixture and the outer periphery defined by e.g. thread tops may have the same or different angle of taper. Furthermore, the core of the fixture may be cylindrical while the thread tops describe a conicity or, conversely, the core of the fixture may be tapered while the thread tops describe a generally cylindrical geometry. Alternatively, the fixture may comprise a combination of one or more cylindrical and/or one or more tapering portions. Thus, one or more portions of the fixture may have e.g. thread tops lying in a common imaginary cylindrical surface, which cylindrical surface is parallel with the longitudinal axis of the fixture. Alternatively or additionally, one or more portions of the fixture may have thread tops lying in an imaginary conical surface which in the apical direction is tapering towards the longitudinal axis.

The externally threaded fixture may comprise one or more thread spirals.

The term “pitch” is used to indicate the axial distance between adjacent tops of a threading. The term “lead” is used to indicate the distance advanced parallel to the longitudinal axis when the fixture is turned one revolution, i.e. it corresponds to the pitch multiplied with the number of thread spirals. For a single thread spiral having a constant pitch, the lead is equal to the pitch; for a double thread spiral, the lead is twice the pitch.

The term “microthread” is used to indicate a thread having a height which is no greater than 0.2 mm. According to at least one example embodiment, the fixture is provided with microthreads having a height in the range of 0.02-0.2 mm, such as 0.05-0.015 mm, for instance 0.1 mm. The term “macrothread” is used to indicate a thread having a height which is greater than 0.2 mm. According to at least one example embodiment, the fixture is provided with macrothreads having a height in the range of 0.25-0.35 mm, such as 0.3 mm.

Suitably, microthreads may be located coronally of macrothreads. For instance, microthreads may be arranged to engage dense cortical bone and macrothreads may be arranged to engage porous spongious/cancellous bone. The lead of a microthread suitably corresponds to the lead of a macrothread. The macrothread pitch may, as an example, be 2-4 times, such as 3 times, the pitch of the microthreads. The pitch (top-to-top spacing) at a fixture portion provided with microthreads may be around 0.10-0.30 mm, for instance 0.20-0.24 mm. The pitch (top-to-top spacing) at a fixture portion provided with macrothreads may be around 0.30-0.90 mm, for instance 0.60-0.72 mm.

Microthreads can be regarded as defined, oriented roughness. A non-oriented roughness having smaller dimensions, for instance obtained by blasting, etching, etc., may be superimposed on microthreads as well as on macrothreads.

A thread profile may comprise two flanks, a top interconnecting said two flanks, a bottom formed between two adjacent threads, said flanks forming an acute angle v with a plane which is perpendicular to the fixture axis and which angle v lies in a plane containing the extension of the fixture axis, said profile further having a height D. The top may be curved and may have a top radius. Suitably, for 10°≦v<35°, the top radius is greater than 0.4×D and, for 35°≦v<55°, the top radius is greater than 0.2×D.

In this application, when strain is discussed, or when different values of strain are discussed, unless explicitly specified, the discussion may relate to tensile strain and/or compressive strain. All strain-related numbers are presented in absolute values.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a-1b illustrate a portion of the threading of the leading and trailing portions, respectively, of a fixture, according to at least one example embodiment of the present invention.



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Device and method intended for holding a prosthesis in dental implantology
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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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Dentistry   Prosthodontics   Holding Or Positioning Denture In Mouth   By Fastening To Jawbone   By Screw