WO2008157138A2

WO2008157138A2 - Dental implant for asymmetrical abutment mounting

Info

Publication number: WO2008157138A2
Application number: PCT/US2008/066457
Authority: WO
Inventors: Graham Blackbeard
Original assignee: Southern Implants, Inc.
Priority date: 2007-06-14
Filing date: 2008-06-10
Publication date: 2008-12-24
Also published as: WO2008157138A3

Abstract

A dental implant system includes a longitudinally elongated implant body and an abutment which is adapted for coupling thereto in a laterally offset position. The implant body extends axially from a proximal-most seating surface to a lower apical end. The seating surface extends radially about the implant axis and defines an upper-most end of a smooth coronal portion. A distal-most bone engaging region of the implant includes a generally cylindrical portion adjacent to the coronal portion and a tapered portion which extends from the cylindrical portion to the apical end. Screw threads extend helically about the cylindrical and tapered portions for use in anchoring the body in position in bone. A blind bore extends inwardly from the seating surface along a bore axis inclined at an angle of between about 0° and 20° relative to the longitudinal axis of the implant body. The bore axis is laterally spaced from the implant axis by an offset lateral distance of between about 0.2 mm and 8 mm. The bore includes an internally threaded portion and an enlarged diameter portion provided with one or more slots or grooves which open to the seating surface. The engagement members have a shape selected for mated contact with at least part of a projection on the abutment to prevent its rotation relative to the implant body. The abutment is further provided with a bearing surface configured for juxtaposed placement against at least part of the seating surface when the projection is received in the bore. The bearing surface is provided with a radial diameter which is smaller than a radial diameter of the seating surface by an amount at least as large as the offset distance.

Description

DENTAL IMPLANT FOR ASYMMETRICAL ABUTMENT MOUNTING

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §1 19(e) to United States Patent Application Serial No. 60/943,927, filed 14 June 2007 and entitled "An Implant Having a Non-Evenly Distributed Horizontal Offset".

SCOPE OF THE INVENTION

The present invention relates to implant systems used in the connection of a prosthesis to bone, and more preferably a dental implant which is adapted for the asymmetrical mounting of an abutment and/or prosthesis, horizontally offset from the implant axis.

BACKGROUND OF THE INVENTION

Dental implant systems are well known and have received widespread acceptance in the marketplace. Conventionally, implant constructions are of a multi-part design and include an implantable body which is adapted to be recessed into a patient's jawbone, and a prosthesis in the form of a ceramic tooth which is adapted for affixation to a metal abutment which has been mechanically coupled to a coronal or upper end (in the direction of implantation) of the implant body.

Most typically, dental implants or implant bodies are formed from metals, such as stainless steel or titanium, and have a cylindrical or tapered shape so as to be elongated in an axial direction. The upper or coronal surface of the implant is provided with an axially extending internal or external connection used to mount the abutment in a co-axial aligned orientation with the implant axis to distribute occlusal forces evenly and axially through the implant and into the patient's jaw. The upper or coronal end of the dental implant is also known as the "abutment interface" and it commonly contains indexing or anti-rotational features which collectively make up a dental implant "connective system". Most implants are placed in the bone such that the abutment interface is either at or a few millimeters above or below bone level. In use, a recess or drill hole is drilled in the patient's jawbone at a desired site. The most common method of preparing the insertion site or osteotomy is to use a rotary drill or reamer to produce a drill hole which is either cylindrical in shape, tapered, or a combination of the two. The implant body is then press or screw-fit into the drill hole generally level with the surrounding jawbone tissues. Over time, the bone tissue grows and engages the sides of the implant body to anchor it in position, in place of the natural tooth. Following healing, the abutment is coupled to the proximal -most end of the implant body by way of a retention screw to serve as the support for the prosthesis.

Studies have shown that crestal bone remodelling is effected by bacteria which collects at the implant/abutment interface or microgap. Due to a number of factors, a small localized inflammatory region in the tissue develops at the implant/abutment interface. This inflammatory response usually causes bone recession of about 1 to 2 mm below the abutment interface. As a result, following initial implant placement, bone tissue will typically recover to a level of 1 to 2 mm below the microgap, with overlying gingival tissues typically extending 1 to 2 mm above the supporting bone.

Receding support tissues or crestal bone loss around dental implants leads to an aesthetic challenge, particularly when dealing with dental restorations in the frontal or anterior regions of the patient's mouth. Alveolar bone tends to gradually disappear along the portions of the implants where engagement of the bone tissues with the implant body does not occur. This in turn results in a corresponding recession of overlying gum tissues and the exposure of the stainless or titanium steel body of the implant and/or the abutment. This may result in the metal abutment or the implant body being visible either directly or through patient's gum tissues as a gray tinted band, greatly detracting from the natural look of the prosthesis.

Most typically, in conventional implant systems, the base of the abutment, abutment bearing surface and the top of the implant have the same diameter. It is also known to provide an abutment with a bearing surface having a smaller diameter than the coronal end of the implant, causing a mismatch or shelf at the top of the implant. In particular, the use of a shelf may increase the spacing of the microgap from the supporting bone tissues to minimize coronal bone recession. This concept, know as platform switching, thus involves the use of a component that is narrower than the top of the implant, whereby the microgap is displaced laterally towards the center of the implant. While the use of comparatively smaller diameter abutments has achieved success in replacement of molars and teeth in the posterior regions of the mouth, heretofore, platform switching has proven unsuitable for use in the replacement of incisor or anterior teeth. In particular, in the anterior regions of the patient's mouth, smaller diameter implants are typically used. It is not uncommon for such implant bodies used in the replacement of anterior teeth to have a maximum diameter of less 4 mm. As such, heretofore, to provide for the desired degree of platform switching, it has been necessary to use comparatively smaller sized abutments having diameters as low as 2 mm. This in turn results in a weakening of the abutment and the overall implant system, increasing the likelihood of either abutment and/or prosethtic failure.

SUMMARY OF THE INVENTION

The present implant system seeks to provide an implant body which provides for the asymmetrical offset mounting of an abutment to stimulate osteoblasts or bone forming cells to promote the maximum degree of bone ingrowth and engagement of the implant body. Most preferably, the implant body is a dental implant adapted for use in the replacement of incisor and other anterior teeth in a patient's mouth, and which maximizes the crestal surface of re- grown bone tissue along the labial and buccal surfaces so as to substantially mirror that of a healthy tooth. Furthermore, the present invention seeks to provide an improved dental implant body for use in the anterior regions of a patient's mouth, and which is suitable for use with conventionally sized abutments while minimizing loss of the patient's labial gingival and/or bone tissues.

It is an object of the present invention to provide a dental implant for use in the anterior regions of a patient's mouth, and which allows for the horizontal offset mounting of comparatively larger abutments.

Another object of the invention is provide an implant system which is adapted to provide the benefits of platform switching, and which is suitable for use in the replacement of anterior or incisor teeth while minimizing any visible shelf surfaces used to provide lateral microgap displacement. Another object of the invention is to provide an improved implant system for use in attaching a prosthesis to bone, and which includes an implant body provided with an axially oriented internal connection which is laterally offset relative to the implant axis.

A further object of the invention is to provide an improved dental implant system having a dental implant and a fixture mount or installation tool, and which enables both simplified implant positioning and mounting of an abutment unevenly offset towards one peripheral side of the implant.

Another object of the invention is to provide a dental implant body having an axially offset internal connection, a smooth upper or coronal region, and an externally threaded bone engaging lower region having one or more bone additional engaging structures, such as porous coatings, texturing, and/or bioreactive coating along part or its entire axial length to maximize bone remodelling and attachment thereto.

A further object is to provide a dental implant that is adapted to contain the inflammatory response associated with the junction between the abutment and the implant, to thereby lead to enhance bone level retention around the implant.

To at least partially achieve at least some of the aforementioned objections, an implant is provided which is adapted for mounting an abutment thereto in an orientation laterally offset to the implant axis, so as to be unevenly distributed or asymmetrical mounted relative to axial center of the implant.

In one possible construction, the implant is a dental implant with a body which is elongated along and extends radially about a central implant axis, from a coronal upper proximal-most end to a lower apical end. Although not essential, an upper-most coronal region (in the direction of implantation) of the implant is provided as a generally smooth collar portion having an axial length of between about 1 and 2 mm, and which extends from the proximal-most end. Although not essential, the proximal-most end is most preferably provided as a generally flat seating surface which is oriented in a position normal to the implant axis. A lower distal-most region of the implant region is provided for bone engagement. The distal-most region includes a generally cylindrical portion, an inwardly tapering portion or both. In one possible construction, a tapered portion is provided which extends downwardly from the cylindrical portion to an apical tip.

The distal-most region is preferably provided with external screw threads which extend helically about at least part of each of the cylindrical and tapered portions, for use in anchoring the implant body in position as bone engaging structures at the desired site of placement. Although not essential, to maximize bone regrowth and attachment, the exterior threads most preferably extend substantially along the length of the distal-most region end adjacent to the coronal region. It is to be appreciated that other bone engaging features and/or surfaces could also be provided in substitution or in addition to the exterior threads. Such features include, without restriction, textured surfaces, porous coated surfaces and/or biologically active coatings. Suitable porous coated surfaces could, for example, include titanium, metal or ceramic beads. Suitable biologically active coatings would typically comprise bioreactive coatings, such as those formed from hydroxyapatite or other compounds suitable for stimulating bone growth.

An internal or external connection is provided on the proximal-most end. Preferably, an internally threaded recess or bore extends from the proximal-most end into the interior of the implant body with the surrounding surface forming a seating surface against which the abutment is secured. The bore is adapted to receive a retaining screw in the coupling of the abutment to the implant body. The bore extends inwardly from the seating surface as a blind bore to an innermost end located within or proximate to the cylindrical portion of the bone engaging region. Preferably, the bore is generally centered about and extends along a bore axis which is inclined relative to the implant axis at an angle of between about 0° and 20°, and most preferably which is substantially parallel to and laterally spaced from axis of the implant body by a distance of at least 0.25 mm, preferably 0.5 to 3 mm, and most preferably about 1 mm from the implant axis.

At the abutment/implant interface, the abutment is provided with a smaller diameter than that of a diameter at its bearing surface which is formed smaller than a diameter of the seating surface by an amount generally equal to the lateral offset distance between the bone axis and the implant axis. The final positioning and angular orientation of the bore is selected relative to the abutment size and configuration. In a most preferred embodiment, when an abutment is coupled to the implant, the abutment emerges from the top for the general alignment with one peripheral side portion and with a shelf or offset along the other radially opposite side portion.

The internal bore may be provided with an engagement portion which includes one or more radially spaced sockets, grooves, projections, slots or other longitudinally oriented openings (hereinafter generally referred to as grooves) which are formed in or extend from the bore sidewall. The engagement members have a shape selected for mated contact with at least part of one or more associated locking members formed on a lower surface of the abutment. In a most simplified form, each engagement member comprises a female slot or groove-type connection having a geometric shape adapted for mated contact with corresponding locking members formed on the abutment. In this manner, contact between the engagement members and its associated locking member limits relative rotation of the abutment relative to the implant body following coupling thereto. Although not essential, in a simplified construction, the engagement members may be provided within an enlarged diameter, non-threaded portion of the internal bore, so as to be open to the seating surface.

Although not essential, a fixture mount may be used to initially position and install the implant at a desired osteotomy. Typically, the fixture mount includes an elongated shaft or body which extends from an upper end to a second lower end used to engage the implant body. The upper end has a shape selected so as to be engagable in rotational movement by a suitable drive tool. By way of non-iimiting example, the upper end may be provided with an octagonal or hexagonal projection which is received in a complimentary-shaped socket of the tool. Where the implant is provided with an internal connection, the second lower end of the fixture mount is provided with a drive projection on which are carried or formed one or more drive members (i.e. a male end of the projection or male member). The drive projection is sized for mated insertion within at least part of the internal bore, having a shape and size which most preferably corresponds to the enlarged diameter portion of the bore, and which has the drive members integrally formed thereon. Although not essential, the drive protection is mounted so as to extend axially offset relative to the fixture mount axis by substantially the same distance as the laterally offset of the bore axis relative to the implant axis. Preferably, on insertion of the drive projection into the bore, the fixture mount is provided in an orientation with the fixture mount axis substantiality aligned with the implant axis. Although not essential, advantageously at least one of the engagement members is provided in an orientation generally aligned with the implant axis as a keyway to limit any eccentric movement out of coaxially alignment with the implant body. The drive members have a shape selected for mated contact with at least part of one or more of the engagement members provided in the internal bore, such that the insertion of the drive projection partially into the bore results in engaging contact between the drive members and the engagement members to limit relative rotation of the fixture mount relative to the implant body.

The fixture mount may be preassembled to the implant body, with the drive members in engaging contact with associated ones of the engagement members. In such a construction, the fixture mount may be provided with a releasably attachment member, used to releasably couple the fixture mount in mated contact with the seating surface of the implant body generally coaxially aligned therewith. In one possible construction, the fixture mount may be provided with one or more clips hooks, prongs or other deformable or frangible members (hereinafter generally referred to as frangible members) adapted to engage the sides of the internal bore and/or complimentary shaped grooves, slots or notches formed in the implant body and/or in a removable coupling screw, to temporarily couple the fixture mount and implant during initial placement.

In use of the implant system, the desired site of implantation is initially prepared by exposing the alveolar bone at the locations of the osteotomy. Initially, a small diameter drill hole of preferably about 2 mm is formed in the jawbone in a direction generally parallel to the direction of jawbone elongation. Thereafter, the guide hole is widened initially using a 3 mm twist drill and reamed using a tapered reamer having a profile corresponding to the radial profile of the implant body. The bore hole is formed to a depth selected to provide optimal seating of the implant in the alveolar bone, and with the seating of the implant body adjacent to the crestal surface of the adjacent bone.

Following preparation of the osteotomy, the implant body, having the fixture mount affixed thereto, is inserted into the hole. The fixture mount is engaged by a driving tool, such as an electrically driven hand piece, to rotate the implant body about its axis in the helical direction, screw fitting the implant in a seated position. A guide member on the fixture mount and/or the implant body may be utilized to provide a visual indication of the rotational orientation of the coronal rim relative to the jawbone, to ensure the optimal offset-position of the mounted prosthesis. Where the implant is used in the replacement of incisor or anterior teeth, the implant body is positioned such that following the mount of the abutment, the maximum microgap offset is preferably oriented towards the buccal side of the osteotomy, and with a minimum offset and most preferably approximately a zero offset, in the lingual orientation.

Once the implant is successfully seated, the fixture mount is decoupled from the implant body. A healing abutment may then be secured to the threaded bore and the area covered for a period of time to allow bone growth and implant adhesion. After healing, the healing abutment is removed, and a conventional prosthesis abutment is secured to the implant body by connecting screw. It is to be appreciated that the final abutment size and design is selected to enable the optimum prosthesis positioning having regard to the site of tooth replacement.

Accordingly, in one aspect, the present invention resides a dental implant system comprising an implant body, and abutment for mounting a prosthesis thereon and a retaining screw, the implant body being elongated along a longitudinally extending implant axis from a proximal-most seating surface and apical end, the implant body including, a generally smooth upper coronal regional and a bone engaging distal region, the distal region including a cylindrical portion proximate to the coronal region, an internal bore extending inwardly from said seating surface along a bore axis to an inner end, the bore axis being inclined at an angle of between 0° and 20° relative to said implant axis and being spaced therefrom by a lateral offset distance selected at between about 0.25 and 3 mm, the internal bore delineated by a sidewall and including an internally threaded portion and an enlarged diameter portion open to said seating surface, at least one longitudinally extending groove extending radially into said sidewall and being open to the seating surface, the abutment including a projecting member sized for insertion within the enlarged diameter portion, the projecting member including, at least one locking member sized for mated engagement with an associated one of said grooves, a bearing surface extending generally radially about the projecting portion and provided for juxtaposed contact with part of said proximal-most seating surface, and a stepped through-bore extending axially through the projecting member and being sized to engagably receive part of the retaining screw therein with the retaining screw in threaded engagement with the internally threaded portion, to mechanically couple the abutment to the implant body with the bearing surface in juxtaposed contact with the seating surface.

In another aspect, the present invention resides in an implant system comprising an implant body and an abutment, the implant body being elongated along a longitudinally extending implant axis and extending from a proximal-most surface to an apical end, the implant body including, an internal blind bore extending inwardly from said proximal-most surface along a bore axis to an inner end, the bore axis being generally parallel to said implant axis and spaced therefrom by a lateral offset distance selected at between about 0.25 and 3 mm, the internal bore further including an internally threaded region, the abutment including a bearing surface provided for juxtaposed contact with part of said proximal-most surface, and through-bore extending therethrough, a retaining screw being insertable in the through-bore and into threaded engagement with the internally threaded region to mechanically couple the abutment to the implant body with the bearing surface in juxtaposed contact with at least part of the proximal-most surface.

In further aspect, the present invention resides in a dental implant system comprising an implant body, and abutment for mounting an anterior tooth prosthesis thereon and a retaining screw, the implant body being elongated along and extending radially about a longitudinally extending implant axis from a proximal-most seating surface and apical end, the implant body further including a generally smooth upper coronal regional and a bone engaging distal region, the distal region including a cylindrical portion proximate to the coronal region, an internal blind bore extending inwardly from said seating surface along a bore axis to an inner end, the bore axis being generally parallel to said implant axis and spaced laterally therefrom by a lateral offset distance selected at between about 0.5 and 2.5 mm, the internal bore delineated by a sidewall and including an internally threaded portion and an enlarged diameter portion open to said seating surface, at least one engagement member extending radially relative to said sidewall, the abutment including a projecting member, a through bore and a generally planar bearing surface extending radially about the projecting member surface, the projecting member, and a stepped through-bore extending axially through the projecting member and being sized to receive the retaining screw partially therein, with the retaining screw in engaging contact with both a portion of the through-bore and the internally threaded portion to mechanically couple the abutment to the implant body, the projecting member sized for insertion within the enlarged diameter portion, and including at least one locking member sized for mated engagement with an associated one of said engagement members, and wherein the bearing surface is provided for juxtaposed contact with at least part of the seating surface, the bearing surface having a diameter which is smaller than a diameter of seating surface by an amount substantially equal to the lateral offset distance.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be had to the following detailed description, taken together with the accompanying drawings in which:

Figure 1 shows a perspective top view of a dental implant body having a horizontally offset abutment mounted thereto, in accordance with a preferred embodiment of the invention;

Figure 2 illustrates a perspective side view of the implant body and abutment shown in Figure 1 ;

Figure 3 shows an enlarged exploded schematic view of the implant body and abutment shown in Figure 2;

Figure 4 shows cross-sectional view of the implant body shown in Figure 3 coupled to a fixture mount in implant placement;

Figure 5 shows an enlarged plan view of the seating surface of the implant body shown in Figure 1 ;

Figure 6 illustrates a cross-sectional view of the dental implant body and abutment positioned in place in an osteotomy in a patient's mandibular jawbone; Figure 7 illustrates schematically the use of the implant body in the mounting of a prosthesis in anterior tooth replacement;

Figure 8 shows an enlarged cross-sectional view of an implant body having a horizontally offset abutment mounted thereto in accordance with another embodiment of the invention; and

Figure 9 shows a perspective view of the implant body and abutment of Figure 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference may be had to Figures 1 and 2 which illustrate an implant body 12 and an abutment 14 which, as will be described, is coupled thereto by a retaining screw 16 as part of an implant system 10 in the mounting of a ceramic prosthesis 150 (Figure 7) in the replacement of a natural incisor tooth.

The implant body 12 is formed from titanium or stainless steel, and is provided for insertion in an osteotomy formed in a patient's mandibular jawbone 8 (Figure 6). The implant body 12 is elongated along an implant axis Ai-Ai (Figure 3) and extends from a proximal-most coronal or upper seating surface 22 to a distal most apical end tip 24. Depending upon the site of implantation, the implant body 12 typically has an overall length of between about 10 and 20 mm, and a maximum diameter D (Figure 5) across the seating surface 22 of between about 3 and 8 mm, and when used in the replacement of anterior teeth preferably about 3.5 mm.

The implant body 12 includes a generally smooth upper-most (relative to the direction of implantation) coronal region 20, and distal bone engaging region 21 which is adapted for engaging contact by bone tissues. The bone engaging region 21 is shown best as extending distally from the coronal region 20, and includes an upper generally cylindrical portion 26 which extends approximately midway along the length of the body 12. The cylindrical portion 26 merges along its lower end with an inwardly tapering portion 28, which extends to the apical tip 24. Preferably, the tapered portion 28 tapers inwardly towards the tip 24 at an angle of between about 3° and 20°, and more preferably about 10°, relative to the implant axis AI-AI. Exterior threads 30 extend helically substantially along the length of both the tapered portion 28 and cylindrical portion 26. Preferably the threads 30 are provided with a thread pitch of between about 0.5 and 0.7 mm. Optionally, the cylindrical and tapered portions 26,28 may further be provided with a reactive surface to stimulate bone regrowth and/or attachment to the body 12 following placement. Suitable reactive surfaces would include the appiication of bioreactive coatings, porous coatings, as well as texturing or roughening of the exterior implant surface by abradement or etching.

The coronal end region 20 of the implant body 12 is typically formed by milling, so as to be concentric about the implant axis Ai-A_t and extends axially 1 to 4 mm from the proximal-most seating surface 22. Optimally, the end region 20 is provided with an outwardly flared collar portion 32 which extends radially outwardly 0.2 to 1 mm beyond the adjacent cylindrical portion 26, and which merges with the seating surface 22. The seating surface 22 is most preferably provided as generally flat planar surface which is positioned in a perpendicular orientation relative to the implant body axis Ai-Ai.

Figures 3 and 5 show best an internal bore 40 formed in the implant body 12. The bore 40 extends inwardly from the seating surface 22 along a bore axis AB-AB which is substantially parallel to the implant axis Ai-Ai, and which is spaced laterally a distance L_D therefrom of between about 0.5 and 1.5 mm. The internal bore 40 is defined by a sidewall 44 and includes an outermost enlarged diameter portion 46 and inner threaded end portion 48. In a most performed configuration, the internal bore 40 does not substantially extend distally past the cylindrical portion 26. A series of radially projecting grooves 50a,50b,50c are formed in the sidewall 44 along the enlarged diameter portion 46. The grooves 50 are open to the seating surface 22, and most preferably extend radially about and parallel to the bore axis A_B-A_B, with groove 50a being positioned in substantially coaxial alignment with the implant axis A|-A|. As will be described the groove 50a acts as a keyway in the placement of the implant body 12 to assist in maintaining any rotation forces thereon concentric about the implant axis Ai-A].

Figures 2 and 3 illustrate best the abutment 14 as used with the present invention. In the embodiment shown, the abutment 14 has a generally frustoconical shape and includes a stepped bore 60 extending through its axially center A_A-A_A. The stepped bore 60 has a dimension selected to enable the retaining screw 16 to be received therein while in threaded engagement with the end portion 48 of the bore 40, in the mechanically coupling of the abutment 14 to the implant body 12. The lower end of the abutment is formed as a bearing surface 62 which extends radially about a projecting member 64. The projecting member 64 is sized for mated insertion within the enlarged diameter portion 46 of the bore 40. The projecting member 64 is aligned with the axis A_A-A_A and includes three locking members 66a₅66b,66c. Each of the locking members 66a,66b,66c are provided with a corresponding shape and orientation to an associated one of grooves 50a,50b,50c respectively. The locking members 66a,66b,66c and grooves 50a, 50b, 50c thus form a female/male type connection on insertion of the projecting member 64 into the bore.

The bearing surface 62 extends radially about the axis A_A-A_A and is formed as a generally flat surface, adapted for mating contact against with a portion of the seating surface 22. The bearing surface 62 has a diameter d (Figure 2) which is smaller than the diameter D of the support surface 22. Most preferably, the diameter d of the bearing surface 62 is selected smaller than the diameter D of the seating surface 22 by an amount equal to the distance of lateral of L_D between the bore axis AB-A_B and the implant axis Aj-A]. In this manner, when the projecting member 64 is inserted in mated engagement with the bore 40, one peripheral edge 62a of the bearing surface 62 is substantially aligned with one peripheral edge of the seating surface 22, and the other radially opposing peripheral edge 62b of the bearing surface 62 horizontally spaced inwardly from the adjacent peripheral edge of the seating surface 22 to define a shelf 72.

It is be appreciated that the formation of the bore 40 in a position laterally offset from the implant axis A_I-A_J allows a conventional abutment 14 to be mounted on the seating surface 22 with one side edge offset relative to the axial center of the implant body 12, without necessitating the use of specially formed asymmetrical abutments or transition members. This in turn allows the prosthesis 150 (Figure 7) to be connected with a 0.25 to 0.75 mm wide shelf 72 to the buccal side of (B) the implant body 12, while maintaining minimal spacing between the bone engaging region 21 of the implant 12 and the prosthesis 150 in the lingual (L) region of the patient's mouth.

The applicant has appreciated that the present invention allows for the use of comparably smaller diameter implants 12, with more robust conventionally sized abutments 14 which thus may be suitable for use in the replacement of incisors and other interior teeth. By way of example, where a small diameter implant body 12 and abutment 14 are used, and strength and stability are important, the horizontal offset can be achieved without a major decrease in abutment 14 diameter d. For example, with an implant body 12 diameter D of 3.5 mm may be used with an abutment with a bearing surface diameter d of 3 mm, to provide an offset of 0.5 mm placed towards the buccal (B). Hence, the amount of horizontal offset on the facial or buccal is 0.5 mm, while on the palatal or lingual side a zero offset occurs.

In initial placement, a fixture mount 80 shown in Figure 4 is most preferably attached to implant 12, enabling the placement of the implant 12 in a substantially conventional manner. The fixture mount 80 is formed from polycarbonate, plastic or metal and extends along a fixture axis Ap-Ap from a first upper end 82 to a lower end portion 84. The upper end 82 is provided with a polygonal cross-section profile which is selected to be engaged by a drive tool, such as hand piece or manual socket wrench (not shown), used to rotate the fixture mount 80 about its longitudinal axis A_M-A_M.

The seating surface 22 may be provided with a notch 34 or other suitable visual indicia which is positioned so as to substantially remain visible following implant placement. The notch 34 is positioned to provide a visual indication of the optimal rotary position of the implant body 12 and bore 40 relative to the patient's jawbone 8. In particular, where the implant body 12 is used in the replacement of incisors, the notch 34 is positioned to enable the orientation of the bore 40 such that the maximum offset or shelf 72 will rotate towards the buccal side (B) of the patient's mouth, as for example, is shown in Figure 7. The notch 34 is most preferably provided for alignment with a dimple 36 providing a central shaft portion 38 of two fixture mounts 80 to permit visual confirmation of the correct alignment of the fixture mount 80 and implant 12, in the event the reassembly of the implant body 12 and fixture mount 80 is required.

The lower end portion 84 of the fixture mount includes a downwardly projecting drive member 86 about which extends a radially projecting contact surface 88. The contact surface 88 is adapted for mated contact against the seating surface 22 of the implant body 12. In this regard, contact surface 88 extends as a generally planar surface which is perpendicular to the axis A_M-A_M

The drive member 86 is a polygonally shaped projection which is sized for mated insertion within the enlarged diameter portion 46 of the bore 40. The drive member 80 extends in a direction of parallel to and is laterally spaced from the fixture mount axis A_M-A_M by a distance substantially corresponding to the laterally offset distance Lp separating the bore axis AB-AB from the implant axis A|-A|. In this manner the drive member 86 is insertable within the enlarged diameter portion 46 of the bore 40 with the fixture mount axis AM-AM substantially aligned with the implant axis Ai-Ai; and with the contact surface 88 in bearing contact against the seating surface 22. The drive member 86 includes three radially spaced projections 90 which have a spacing and configuration adapted for nested placement within a corresponding associated groove 50. The engagement between the projections 90 within an associated groove 50a,50b,50c is selected to limit relative rotation between the fixture mount 80 and the implant body 12, as the fixture mount 80 is rotated about its axis AM-AM-

The dimple 36 may be provided for visual alignment with the notch 34, or other suitable visual indicator formed in the seating surface 22 or elsewhere on the implant body 12 to ensure the optimal relative rotational alignment of the fixture mount 14 relative to the body 12. Preferably, the dimple 36 provides an identification on the buccal side (B) of the patient's mouth following complete implant seating.

In one simplified construction, the drive member 86 is provided with a series of deformable clips 94a,94b. The deformable clips 94a, 94b extend in the axial direction from the end most portion of the drive member 86 to resiliently engage against the sides of the threaded end portion 48 of the bore 40. The engagement of the clips 94a,94b with the threaded end portion 48 operates to releasably secure the fixture mount 80 to the end of the implant body 12 in alignment therewith.

In placement of the implant body 12 the osteotomy is initiated by perforating the cortical plate at a desired location. A pilot drill hole is formed which extends in an orientation generally parallel to the alignment of bone tissue 8 and any adjacent teeth/implants. Subsequently, osteotomy is widened using an appropriate tapered drill (not shown) to the desired depth, and most preferably, to a depth which will allow substantially complete seating of the collar 32 with its lowermost edge flush with the surface of the bone 8.

With the fixture mount 80 preassembled to the implant 12, and the mount axis AM-A_M and implant axis A]-Ai aligned, the implant body 12 is inserted into the formed hole. A hand piece (not shown) is secured to the upper end 82 of the fixture mount 80. The hand piece is used to install the implant body 12 by rotating the fixture mount about the axis Ap-Ap to drive the apical end 24 downward into the jawbone 8 to a substantially seated position. Final positioning of the implant body 12 is performed manually by the use of the a ratchet wrench (not shown) to position the implant body 12 with the dimple 36 and bore 40 proximal-most to the buccal or facial side (B).

Following implant body 12 positioning, the fixture mount 80 is uncoupled from the implant body 12 by tilting to move the drive member 86 axially from the bore 40. Thereafter, a covering screw (not shown) is positioned over the bore 40, and the gingival tissues 102 are sutured to allow complete abutment healing. Following healing, the covering screw is removed and the abutment 14 is secured to the implant body 12 by insetting the projection 64 into the bore 40, to seat the bearing surface 62 in contact against the seating surface 22. Following insertion of the projecting member 64 into the enlarged diameter portion 46, the retention screw 16 is thereafter inserted into the stepped through-opening 60 and into threaded engagement with the end portion 48 to mechanically couple the abutment 14 in the offset orientation shown in Figure 1. The prosthesis 150 is thereafter adhered over the abutment 14 to complete tooth replacement.

As shown best in Figure 6, the horizontal offset of the bore 40 relative to the implant axis AI-AI results in the abutment 14 and prosthesis 150 to be mounted asymmetrically relative to the implant axis Aj- A|. In particular, the asymmetric mounting of the abutment 14 results in the formation of the shelf 72 along the buccal-most side B of the implant body 12. As indicated, the existence of the shelf 72 advantageously provides for platform switching and the maximization of the microgap-bone tissue spacing along the buccal sides of the implant body 12.

The asymmetric mounting of the prosthesis 150 provides a further ancillary advantage. The prosthesis axis, namely the direction of operation elongation of the prosthesis, is off- centered relative to the implant axis A_rA[. Studies have suggested that such offset positioning may advantageously result in an uneven force distribution across the implant body 12 towards the lingual side L. Such uneven force distribution may act to stimulate bone and connective tissue growth, further minimizing bone and gingival tissue loss. It is to be appreciated as used herein, reference to "upper and lower" positions refer to the relative positioning of the implant body 12 into a bore formed in the patient's jawbone 8.

Although the preferred embodiments describe and illustrate the implant body 12 as having a lowermost tapered portion 28, the invention is not so limited. It is to be appreciated that in alternate construction, the body 12 may be provided with a generally cylindrical shape, and/or alternately it may be tapered along substantially its entire axial length.

Although the preferred embodiment describes the implant system 10 used in the placement of the denta! implant in a mandibular jawbone 8, the invention is not so limited. It is to be appreciated that the implant construction may equally be used in the mounting of prosthesis either elsewhere in the mouth, or for that matter, elsewhere in a patient's body, without departing from the spirit and scope of the invention. By way of non-limiting examples, the implant could also be used as a bone implant for arm or leg appendage bones (e.g. phalanges, femur, humerus), to enable fixation of an osseointegrated implant to, for example, a prosthetic finger, thumb, toe, leg or arm.

Although the preferred embodiment describes the use of grooves 50 as engagement members, the invention is not so limited. The implant 12, the abutment 14 and the fixture mount 80 could be provided with various other structures which provide male/female type connections having complimentary shapes and sizes which, in engagement, prevent or limit relative rotational movement.

Although Figure 5 describes and illustrates the connection of the fixture mount 80 to the implant body 12 by way of projections 90a,90b the invention is not so limited. It is to be appreciated that various other types of frangible and/or deformable members could be used to mechanically couple the fixture mount 80 in the desired axial orientation. Suitable members would include without limitation, frangible fingers, prongs, clips, or the like which are adapted for complimentary engagement with grooves, notches or recesses formed in either a removable positioning screw and/or the implant body 12.

Although the detailed description describes the seating surface 22 as being a planar surface in an orientation perpendicular to the body axis A|-A|, the invention is not so limited. The seating surface 22 could be provided in a position angularly oriented to the implant axis, as for example at an angle of upto 20°. In addition, although a generally planar seating surface 22 permits simplified manufacture, it is to be appreciated that the seating surface 22 could be provided with a curved or conical shape, without departing from the spirit and scope of the invention.

Although the detailed description describes the implant body 12 as having an internal connection by way of internal bore 40, the implant body 12 could equally be provided with an external connection, such as a conventional external hex-mount.

While the Figures show the abutment 14 as having a generally frustoconical shape, other abutment shapes and sizes may also be used, and will now become readily apparent.

Although Figures 2 and 3 illustrate the implant body 14 as having an enlarged collar portion 32 which extends radially outwardly beyond the adjacent cylindrical portion 26, the invention is not so limited. The collar portion could be provided without the illustrated overhang. In an alternate embodiment, the collar portion 32 could be provided with an uppermost inwardly beveled edge, which extends angularly towards the implant axis.

While Figure 1 shows the implant body IO as having a seating surface 22 which extends normal to the direction of the implant axis Ai-Aj, the invention is not so limited. Reference may be had to Figure 8 which shows an alternate implant system 10, wherein like reference numerals are used to identify like components.

In Figure 8, the implant body 12 is provided with an upper seating surface 2 and internal base 40 which are included at angle of between about 5° and 12° relative to the axis A[-A|. The coronal region 2 is optimally provided with striations or helical grooves 130 which extend only partially about the radial surface of the region 20. Most preferably, the radial grooves 130 extend about an arc of less than about 160° and preferably about I2O°± 20°.

The grooves 1303 are provided so as to engage bone tissues only along the one side of the implant body 12 which is titled closest to the jawbone 8 as the body 12 is seated in an osteotomy. Although the detailed description describes that positioning of the implant 12 and abutment 14 with the shelf 72 oriented to the buccal side (B) of the patient's mouth, the invention is not so limited. It is to be appreciated that in alternate applications and depending upon the individual patient needs, the implant could be positioned with the shelf 72 oriented proximate-most to the lingual side, or for that matter, to an occlusal or distal side.

Although the detailed description describes and illustrates various preferred embodiments, the invention is not so limited. Many modifications and variations will now occur to persons skilled in the art. For a definition of the invention, reference may be had to the appended claims.

Claims

We claim:

1. A dental implant system comprising an implant body, and abutment for mounting a prosthesis thereon and a retaining screw, the implant body being elongated along a longitudinally extending implant axis from a proximal-most seating surface and apical end, the implant body including, a generally smooth upper coronal regional and a bone engaging distal region, the distal region including a cylindrical portion proximate to the coronal region, an internal bore extending inwardly from said seating surface along a bore axis to an inner end, the bore axis being inclined at an angle of between 0° and 20° relative to said implant axis and being spaced therefrom by a lateral offset distance selected at between about 0.25 and 3 mm, the internal bore delineated by a sidewall and including an internally threaded portion and an enlarged diameter portion open to said seating surface, at least one longitudinally extending groove extending radially into said sidewall and being open to the seating surface, the abutment including a projecting member sized for insertion within the enlarged diameter portion, the projecting member including, at least one locking member sized for mated engagement with an associated one of said grooves, a bearing surface extending generally radially about the projecting portion and provided for juxtaposed contact with part of said proximal-most seating surface, and a stepped through-bore extending axially through the projecting member and being sized to engagably receive part of the retaining screw therein with the retaining screw in threaded engagement with the internally threaded portion, to mechanically couple the abutment to the implant body with the bearing surface in juxtaposed contact with the seating surface.

2. The dental implant system as claimed in claim 1 wherein the bore axis is generally parallel to said implant axis.

3. The dental implant system as claimed in claim 2 wherein a first one of said longitudinally extending grooves is generally aligned with said implant axis.

4. The dental implant as claimed in claim 2 wherein the bone engaging distal region further includes a tapered portion which tapers inwardly from the cylindrical portion towards said apical end, external threads disposed along at least part of each of said cylindrical portion and tapered portion, and wherein the internally threaded portion is substantially disposed within the cylindrical portion.

5. The dental implant system of claim 2 further including, a fixture mount extending along a too! axis from a first end portion to a second end portion engagable by a rotational tool, the first end portion being configured for generally mated contact with the seating surface with the tool axis generally coaxially aligned with the implant axis, the first end portion including at least one drive member configured for engaging contact with selected one of said longitudinally extending grooves to limit rotational movement of the fixture mount relative to the implant body when in mated contact therewith, and a releasable attachment member releasably mechanically coupling the fixture mount in mated contact with the implant body, with the tool axis coaxially aligned with the implant axis, and whereby rotation of the second end about the tool axis by the rotational tool effects rotation of the implant body about the implant axis.

6. The dental implant system of claim 2 wherein said seating surface comprises a generally planar seating surface which extends radially about and normal to said implant axis, said bearing surface having a diameter which is selected small than a diameter of said seating surface by an amount greater than or equal to the lateral offset distance.

7. The dental implant system of claim 1 wherein the bore axis is spaced from the implant axis by a lateral offset distance selected at between about 0.5 mm and 2 mm.

8. The dental implant system of claim 7 wherein the bearing surface of the abutment extends generally radially about the abutment axis, the bearing surface having a diameter selected smaller than a diameter of the seating surface by an amount substantially equal to the lateral offset distance.

9. The dental implant system of claim 8 wherein the distal region includes external helical threads for securing said implant body into bone.

10. An implant system comprising an implant body and an abutment, the implant body being elongated along a longitudinally extending implant axis and extending from a proximal-most surface to an apical end, the implant body including, an internal blind bore extending inwardly from said proximal-most surface along a bore axis to an inner end, the bore axis being generally parallel to said implant axis and spaced therefrom by a lateral offset distance selected at between about 0.25 and 3 mm, the internal bore further including an internally threaded region, the abutment including a bearing surface provided for juxtaposed contact with part of said proximal-most surface, and through-bore extending therethrough, a retaining screw being insertable in the through-bore and into threaded engagement with the internally threaded region to mechanically couple the abutment to the implant body with the bearing surface in juxtaposed contact with at least part of the proximal-most surface.

1 1. The implant system of claim 10 wherein said proximal-most surface comprises a generally planar seating surface which extends radially about said implant axis, said bearing surface extending as a radial surface and having a diameter which is selected smaller than a diameter of said seating surface by an amount greater than or equal to the lateral offset distance.

12. The implant system of claim 1 1 wherein the lateral offset distance is selected at between about 0.5 mm and 2 mm.

13. The implant system of claim 12 wherein the bearing surface has a diameter selected smaller than a diameter of the seating surface by an amount substantially equal to the lateral offset distance.

14. The system of claim 13 wherein the implant includes a smooth upper coronal region extending distally from said seating surface, the implant body further including a distal-most bone engaging region, the bone engaging region having external helical threads adapted for engaging jawbone tissue and including a generally cylindrical portion spaced towards the coronal region and a tapered portion extending from the cylindrical portion towards to said apical end, the tapered portion tapering inwardly towards said implant axis at an angle selected at between about 5° and 30°.

15. The implant system of claim 13 whei^'ein the internal bore further includes an enlarged diameter portion open to said seating surface, at least one longitudinally extending groove extending radially into said sidewall and being open to the seating surface, and the abutment having a projecting member sized for insertion within the enlarged diameter portion, the projecting member including at least one locking member sized for mated engagement with an associated one of said grooves.

16. The implant system of claim 14 wherein said upper coronal region extends radially from said implant axis a distance of 0.5 to 3 mm further than a radial extent of said cylindrical portion.

17. The implant system of claim 14 further including, a fixture mount extending along a tool axis from a first end portion to a second end portion engagable by a rotational tool, the first end portion being configured for generally mated contact with the seating surface with the tool axis in generally coaxially alignment with the implant axis, the first end portion further including at least one drive member configured for engaging contact with a selected one of said longitudinally extending grooves to limit rotational movement of the fixture mount relative to the implant body when in mated contact therewith, and a releasable attachment member releasably mechanically coupling the fixture mount to the implant body, and whereby rotation of the second end about the tool axis by the rotational tool effect rotation of the implant body about the implant axis.

18. The implant system as claimed in claim 17 wherein the selected one of said longitudinally extending grooves is generally coaxially aligned with said implant axis.

19. A dental implant system comprising an implant body, and abutment for mounting an anterior tooth prosthesis thereon and a retaining screw, the implant body being elongated along and extending radially about a longitudinally extending implant axis from a proximal-most seating surface and apical end, the implant body further including a generally smooth upper coronal regional and a bone engaging distal region, the distal region including a cylindrical portion proximate to the coronal region, an internal blind bore extending inwardly from said seating surface along a bore axis to an inner end, the bore axis being generally parallel to said implant axis and spaced laterally therefrom by a lateral offset distance selected at between about 0.5 and 2.5 mm, the internal bore delineated by a sidewall and including an internally threaded portion and an enlarged diameter portion open to said seating surface, at least one engagement member extending radially relative to said sidewall, the abutment including a projecting member, a through bore and a generally planar bearing surface extending radially about the projecting member surface, the projecting member, and a stepped through-bore extending axially through the projecting member and being sized to receive the retaining screw partially therein, with the retaining screw in engaging contact with both a portion of the through-bore and the internally threaded portion to mechanically couple the abutment to the implant body, the projecting member sized for insertion within the enlarged diameter portion, and including at least one locking member sized for mated engagement with an associated one of said engagement members, and wherein the bearing surface is provided for juxtaposed contact with at least part of the seating surface, the bearing surface having a diameter which is smaller than a diameter of seating surface by an amount substantially equal to the lateral offset distance.

20. The implant system of claim 19 wherein said upper coronal region extends radially from said implant axis a distance of 0.5 to 3 mm further than a radial extent of said cylindrical portion.

21. The implant system of claim 19 wherein said seating surface is inclined at an angle of between about 3° and 15° relative to the implant axis, said upper coronal region further including helical grooves which extend partially about a radial surface of said coronal region along an arc of less than about 160°.