Background of the Invention Implants that can be screwed into bone are well known in the art. For example, one such screw implant is shown in U. S. Patent No. 6,325, 628. In that particular patent a combination implant and abutment member is shown particularly useful for mounting temporary prosthesis comprising a head portion integrally formed on an implant post having cortical bone threads formed along the length of the post.

An object of the present invention is the provision of a threaded implant having improved biocompatibility of the implant and attached prosthetics.

Summary of the Invention Briefly, an implant made in accordance with the invention comprises an elongated post member having an integrally formed head at one end and a threaded axial length portion disposed between unthreaded apical and coronal axial length portions. The coronal axial length portion preferably includes a neck formed with an epithelial stop and a taper that serves to seal the osteotomy into which the implant member is placed. Several head configurations are shown which include a smooth convexly curved basal portion on which an angled shelf is formed. One head configuration has a snap-on O-ring groove and hexagonal feature formed on a nose portion projecting from the shelf. Another head configuration has a coping receiving conical surface on a nose portion projecting from the shelf and a threaded bore formed through the outer free end surface of the nose for mounting a temporary prosthesis. Still another head configuration has a generally conically shaped nose projecting from the shelf and formed with first and second axial length portions. A stepped retention feature for a sleeve member or the like is provided by forming a larger circumference of the apical side of the outer axial length portion compared to the circumference of the coronal side of the inner axial length portion with both portions having a diameter that decreases in the direction along the axial lengths going away from the shelf.

Additional objects and features of the invention will be set forth in the description which follows and in part will be obvious from the description.

The objects and advantages of the invention may be realized and attained by means of the instrumentalities and methods particularly pointed out in the appended claims.

Brief Description of the Drawings The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. In the drawings: Fig. 1 is a front view of an implant member made in accordance with a first preferred embodiment of the invention and Fig. la is a top view thereof; Fig. 2 is a front view of an implant member made in accordance with a second preferred embodiment and Fig. 2a is a top view thereof ; and Fig. 3 is a front view of an implant member made in accordance with a third preferred embodiment and Fig. 3 a is a top view thereof.

Detailed Description of the Preferred Embodiments With reference to Figs. 1 and la, implant member 10 comprises an elongated post having a selected axial length 10a, two such examples being 0.315 inch and 0.472 inch, and having a selected diameter such 0.073 inch, formed with a cortical bone screw thread along a first significant or major axial length portion 10b intermediate to an unthreaded apical second significant or major length portion 10c and an unthreaded coronal third axial length portion 10d. Unthreaded apical axial length portion l Oc can be of any length, for example, a length generally corresponding to the axial length portion l Ob of the cortical bone thread, as shown in the drawings. Implant member 10 is also formed with an integral abutment portion love. Abutment portion lOe has a basal portion 1 Of formed with a smooth, convex, outer surface configuration, such as spherical, elliptical or the like, and a head portion lOg. Head portion lOg is formed with a nose portion projecting from a shelf 1 Om. The nose portion has a circumferentially extending O-ring groove lOh between a generally semispherical outer free end l Oj and a polygonal, such as hexagonal, configuration lOk adjacent to the shelf. Shelf l Om extends from the junction of head lOj with basal portion lOf. Shelf l Om preferably forms an angle with an imaginary plane perpendicular to the longitudinal axis 2 of the head portion in the range of approximately 0-30 degrees, and, more preferably, approximately 15 degrees, as disclosed and discussed in U. S.

Patent No. 6,290, 500, the subject matter of which is incorporated herein by this reference.

Head portion lOg is particularly useful for mounting prosthesis having bridge structures and the like formed with O-ring snap-on fixation attachment structures. Polygonal configuration portion 1 Ok can be used for driving the member into an osteotomy in a known manner.

Preferably, an epithelial stop lOn is provided comprising an annular surface circumscribing unthreaded coronal portion lOd of implant member 10.

Epithelial stop 1 On comprises an annular surface groove that forms a sharp angle with the outer peripheral surface, e. g. , a right of acute angle on the apical side of the groove. Annular groove surface portion lOn2 extends from the outer peripheral surface of coronal portion lOd on the coronal side of the inner part of the groove in a direction toward the apical end of the implant <BR> member and forms a relatively less sharp, i. e. , a relatively smooth, transition with the outer peripheral surface of coronal portion lOd. Annular surface portion lOnl forms a second surface portion which extends from the inner part of the groove generally toward the coronal end of the implant member to form a sharp transition with the outer peripheral surface of the coronal portion lOd.

Such epithelial stops are disclosed in U. S. Patent No. 6,227, 857, the subject matter of which is incorporated herein by this reference.

Coronal portion lOd is preferably formed with a taper with the diameter of that portion increasing as one proceeds in a direction toward the basal portion of the implant member which serves to seal the osteotomy into which the implant member is placed. The unthreaded coronal portion also allows for adapting to varying mucosal thicknesses.

The above described structure of the cortical bone threaded portion disposed between the unthreaded apical and coronal portions results in the following advantages: The unthreaded apical portion serves as a pilot portion and provides a structure which requires fewer turns to seat the implant member into a prepared pilot bore or hole in a bone.

The unthreaded apical portion serves to maintain the implant member in a path following the trajectory of the pilot bore.

The unthreaded apical portion provides lateral stability without applying pressure on the bone that could result in intial osteoclastic bone activity.

The unthreaded apical portion allows for immediate bone deposition or growth without undergoing osteoclastic bone activity.

As noted above, the unthreaded coronal portion allows for adapting to varying mucosal thicknesses.

As noted above, the tapered neck of the coronal portion of the post serves to seal the osteotomy into which the implant member is placed.

The implant member can be provided with various head structures, for example, as shown in Figs. 2,2a and 3, 3a, to be described below.

Figs. 2 and 2a show an implant member 20 made in accordance with a second preferred embodiment of the invention. Implant member 20 is formed with a head 20a having a cylindrical nose projecting from basal portion lOf and has four spaced apart flats 20b to facilitate driving the member into an osteotomy formed in the cortical bone. It will be understood that the number of flats provided is a matter of choice. A tapered or conical coping receiving surface 20c is formed at the coronal end portion and a bore 20d is formed through the coronal end surface extending along the longitudinal axis 2. The outer portion of bore 20d is threaded and the inner portion 20e may be formed with a non-circular, e. g. , hexagonal, portion to facilitate fastening in a bore by means of a latched dental hand piece screw driver. A coping (not shown), typically formed of suitable moldable plastic material to which a temporary prosthesis (not shown) will bond, can be placed on head 20a of several such implant members for supporting a temporary or permanent prosthesis, being attached by means of threaded pins received in bore 20d of the implant members. A system of this type is disclosed in U. S. Patent No. 6,325, 628, referenced above, the subject mater of which is incorporated herein by this reference. The basal portion lOf and axial length post portion lOa are the same as in the Fig. 1, la embodiment to which reference may be had for a description thereof.

If desired, head 20a can be formed with bores (not shown) through the head to accommodate the fastening of orthopedic wires. For example, two bores extending through the head generally perpendicular to the longitudinal axis 2 at a selected angle to each other, e. g. , 90 degrees, and preferably at different axial levels to thereby provide anchorage for orthopedic wires and devices.

Figs. 3 and 3a show an implant member 30 for mounting crowns and the like made in accordance with a third preferred embodiment of the invention. Implant member 30 is formed with a head 30a having a generally cylindrical, tapered nose 30b projecting from shelf 10m. Nose 30b is formed with one or more anti-rotation flats 30c and preferably with a stepped locking or retention portion 30d formed intermediate to first and second axial length portions al, a2 of nose 30b and preferably separated from each other by a circumferentially extending groove 30f. Stepped axial length portions can be formed to extend completely around the circumference, or, if desired, along a portion thereof, such as along the radiused portion of nose portion 30b, e. g., portions of the circumference between the one or more anti-rotation flats. The circumference of each axial length portion decreases as the distance from the basal portion l Of increases. Further, the circumference of nose portion 30b on the coronal side of the stepped portion, or the side further from the basal portion, immediately adjacent to groove 30f, is larger than the circumference of the nose on the apical side of the groove to form the retention feature. By way of example, an implant member made in accordance with the Figs. 3, 3 a embodiment has an apical diameter of axial length a2 of 0.076 inch and the coronal diameter 0.073 inch. Abutment heads of this type are disclosed in U. S.

Patent No. 6,592, 370, the subject matter of which is incorporated herein by this reference. The basal portion l Of and implant post portion 1 Oa are the same as in the Figs. 1 and la embodiment to which reference may be had for a description thereof.

Also shown in Fig. 3 is a typical crown 40 shown in dashed lines that can be attached to implant member 30, as by cementing thereto in a known manner.

It will be understood that still other head configurations can be used with implant post lOa within the purview of the invention.

Although the invention has been described with regard to specific preferred embodiments thereof, variations and modifications will become apparent to those of ordinary skill in the art. It is therefore, the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.