Dental implant member

Abstract

A dental implant member for supporting and stabilizing crowns, bridges, or the like, having a threaded portion to be received in the alveolar bone, a cylindrical section to be embraced by periodontal tissue, and a conical frustum section to be received in a suitable opening in the crown, terminal pontic of a bridge, or the like.

Description

This invention relates to the field of dental prosthetics, and more particularly, to an improvement in dental implant members.

BACKGROUND OF THE INVENTION

Implantology involves the embedment of one or more artificial support and stabilizing implant members in the alveolar bone portion of the jaw to act as an artificial root for a prosthetic tooth, e.g., a crown, or a series of connected prosthetic teeth, e.g., a bridge.

This technique is to be distinguished from the conventional crown procedure wherein the ground-down stub of a viable tooth is used as the support structure.

The implantology technique is to be distinguished, also, from the conventional technique for preparing a bridge wherein the prosthetic device is clamped to adjacent sound tooth structure for support and stabilization.

In general, an implant member will be employed to support a crown where the stub of a natural tooth is not available, and it will be used to support a bridge where it is not possible or is undesirable to anchor the prosthetic device to the natural tooth next adjacent to the gap to be bridged, and where such a natural tooth is absent.

The use of implant members enables the dentist to develop prosthetic devices which are self-contained, and self-supporting, and which do not require the presence of adjacent natural teeth. Further, prosthetic devices supported by implant members are generally lighter in weight than varieties which are supported by adjacent natural teeth, more comfortable to wear, and are aesthetically more pleasing since they are free of visible metal clamps and the like.

A variety of dental implant members have been proposed and experimented with. These include devices in the forms of blades, pins, screws and the like. For one reason or another, none of these devices has as yet met with substantial commercial success. For example, blade-shaped implant members require extensive surgery to install, and this is accompanied, necessarily, by substantial trauma. Pins, although easier to install, frequently provide inadequate long term support and stabilization because of their relatively small cross-section and poor anchoring ability.

In some respects, the screw-type implant members have the capability of providing a reasonable compromise between the blade and pin-type implant members. They provide better anchoring than do pin implant members, and can be installed with far less extensive surgery and attendant trauma associated with blade-type inserts.

However, the screw-type insert members developed to date have not lived up to their potential. One of the problems associated with prior art screw-type implant members is that they tend to promote irritation, inflammation and infection of the periodontal tissue. This is believed to be due at least in part to the manner in which the implant members are designed in the area in which they contact the periodontal tissue. A contributing factor may be tissue rejection of the material forming the implant member.

Another problem associated with prior art screw-type implant members is that consideration has not been given to designing their shank portions to accommodate crowns and bridges in a manner which allows for proper fit. Failure to do so can result in non-axial stresses being applied to the implant members, for example, through chewing. The resultant stresses can effect a loosening of the implant member and eventual failure of the crown or bridge it supports.

SUMMARY OF THE INVENTION

It is a principal object of the present invention to overcome the foregoing problems by providing an improved dental implant member of the screw-type which will not irritate periodontal tissue, and which, in general, will provide a stronger and sturdier support structure for dental prosthetics than screw-type implant members of the prior art. This can be accomplished with nominal clinical instrumentation used to perform a simplified surgical technique with minimal trauma resulting.

In accordance with the present invention, there is provided a dental implant member formed of a generally cylindrical body, comprising a threaded portion having upper and lower ends. The threaded portion is defined by a plurality of thread convolutions terminating radially of the body in thread crests, and separated axially along the body by thread flanks.

The implant member is further provided with a shank portion having an upper end, and a lower end coterminus with the upper end of the threaded portion.

The shank portion comprises a cylindrical section defining the lower end of the shank portion and extending upwardly a distance within the range of from about 0.5 to about 1.5 mm. or greater, but preferably about 1 mm. from the terminus of the upper thread flank of the uppermost thread convolution defining the threaded portion of the implant member. The periphery of the cylindrical section and the thread crests are designed to lie in a plane parallel to the axis of the generally cylindrical body of which the implant member is formed.

Finally, the shank portion further comprises a conical frustum section having its base coterminus with the upper end of the cylindrical section of the shank portion of the implant member. As described more fully hereinafter, the conical frustum section is provided with means for drivingly connecting the implant member with an inserting tool.

In accordance with a further aspect of the present invention, the dental implant member is formed of a ceramic composition comprising at least about 95 wt. % aluminum oxide. This material is preferred due to its inertness and its compatibility with living tissue.

An important feature of the invention is the provision of the shank portion of the implant member with a cylindrical section. When the implant member is screwed into the alveolar bone, the cylindrical section of the shank portion comes to rest in the plane of the periodontal tissue, which is then able to conform itself smoothly and uniformly to the constant radius of curvature of the said cylindrical section.

Another important feature of the invention is the provision that the thread crests and the periphery of the cylindrical section lie in a plane parallel to the axis of the generally cylindrical body from which the implant member is formed. This provides a smooth transitional section of implant member, essentially constant in radius of curvature, at the juncture of alveolar bone and periodontal tissue. This eliminates sharp points and corners which may act as sources of irritation and inflammation to the periodontal tissue.

Another important feature of the invention is the provision of a conical frustum section on the shank portion, which coacts with a generally cylindrical opening in a crown or terminal pontic of a bridge, to permit the prosthetic device to be canted or angled to provide the best fit and minimize non-axial stresses in the implant member which would ultimately weaken its anchorage in the alveolar bone.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings wherein like reference numerals indicate like parts of the various views:

FIG. 1 is a pictorial schematic view of a dental implant member of the present invention;

FIG. 2 is a schematic cross-sectional view of a fragment of a jaw into which has been set a six-pontic bridge in which the terminal pontics are supported by implant members of the present invention;

FIG. 3 is a schematic cross-sectional view of a crown installed with an implant member of the present invention;

FIG. 4 is a pictorial schematic fragmentary view of a jaw into which a hole is about to be drilled;

FIG. 5 is a pictorial schematic fragmentary view of a jaw having a drilled hole which is about to be tapped; and

FIG. 6 is a pictorial schematic fragmentary view of a jaw into which an implant member has been screwed, using an insert tool.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, FIG. 1 illustrates dental implant member A formed of a generally cylindrical body, and comprising threaded portion B and shank portion C.

Threaded portion B has upper and lower ends 10, 12 respectively, and is defined by a plurality of threaded convolutions terminating radially of the cylindrical body in thread crests 14, and separately axially along the body by thread flanks 16.

Shank portion C has an upper end 18 and a lower end coterminus with upper end 10 of threaded portion B.

Shank portion C further comprises cylindrical section 20 defining the lower end of the shank portion and extending upwardly a distance within the range of from about 0.5 to about 1.5 mm. or greater, but preferably about 1 mm., from terminus 22 of upper thread flank 16 of the uppermost thread convolution defining threaded portion B. Shank portion C further comprises conical frustum section 24 having its base coterminus with the upper end of cylindrical section 20.

Upper end 18 of shank portion C is provided with means for drivingly connecting the implant member with an insert tool (see FIG. 6), which, in the embodiment illustrated in FIG. 1, takes the form of opposed, generally flat, parallel faces 26.

Referring to FIG. 2, there is illustrated a portion of a jaw, designated generally as 30, comprising periodontal tissue 32 and alveolar bone 34.

Mounted in the jaw is bridge 28 comprising interconnected pontics 36, 38, 40, 42, 44, 46.

Terminal pontics 36, 46 are provided, respectively, with generally cylindrical bores 48, 50 into which conical frustum sections 24 of implant member A are set in suitable cement 52.

It will be noted that cylindrical section 20 of the shank portion of implant member A is generally coplanar with periodontal tissue 32. This provides the tissue with a smooth, uniform surface of constant radius of curvature to lie against, minimizing the chances of irritation developing. Essentially, the entire length of the threaded portion B of the implant member is embedded in alveolar bone 34.

It should be particularly noted that in order to provide a proper fit for bridge 28, conical frustum section 24 is generally centered within cylindrical bore 48 of terminal pontic 38, while conical frustum section 24, upon which terminal pontic 46 is mounted, is disposed eccentrically within cylindrical bore 50. If not for the ability to accommodate the alignment of the terminal pontics on their respective implant members, undue stresses would be set up in the implant members which would ultimately weaken their anchorage in alveolar bone 34.

FIG. 3 illustrates the mounting of crown 54, a single tooth prosthetic device, on implant member A. It will be seen from this illustrated embodiment that the implant member of the present invention can be used to support and stabilize a single tooth prosthetic device as well as a bridge as described above.

The implant members may be formed of any of a variety of different materials so long as they are sufficiently strong to meet the support and stabilizing demands placed upon the insert and are inert to the environment in which the inserts are to be placed. Among the useful materials are synthetic organic resins, with and without structural fillers and reinforcement; metals and alloys; and ceramic compositions. Vitallium, a commercially available cobalt-based alloy, is a suitable metallic material for use in practicing the invention. Useful ceramic materials will contain at least 95 wt. % aluminum oxide and preferably at least about 96 wt. % aluminum oxide. A useful commercially available ceramic material is sold under the trademark Degussit (believed to contain about 99.5 wt. % aluminum oxide) manufactured by Degussa, a German company.

The method of installing a dental implant member of the invention is pictorially illustrated in FIGS. 4-6.

Referring to FIG. 4, after periodontal tissue 32 is reflexed, drill bit 56, driven by suitable means not illustrated, is lowered into alveolar bone 34 to a depth corresponding approximately to the length of the threaded portion of the implant member to be installed. A suitable stop means, such as sleeve 57 illustrated in FIG. 4, may be attached to drill bit 56 to mark the desired depth. The diameter of drill bit 56 should be slightly less than the diameter of the cylindrical body from which the implant member is formed. For example, if the diameter of the cylindrical body is 0.134 inch, the diameter of the drill is conveniently 0.125 inch.

After the hole has been drilled and the drill bit removed, the hole is then tapped with tap 58 to which insert tool 60 is drivingly connected, as illustrated in FIG. 5. The diameter of the tap should be slightly larger than the diameter of the cylindrical body forming the implant member. Thus, where the cylindrical body is 0.132 inch in diameter, a suitable tap would have a diameter of 0.138 inch.

After the hole has been tapped and the tap removed, dental implant member A, as illustrated in FIG. 6, is then inserted in the hole and screwed into place with insert tool 60 which, for the sake of convenience, is the same tool used to drive tap 58. Tool 60 is provided with flats 62 which are suitably dimensioned to snugly fit against surfaces 26 formed in the conical frustum section of dental implant member A (The same flats 62 fit snugly against surfaces 26a formed in the shank portion of tap 58, as illustrated in FIG. 5). The reflexed periodontal tissue is then returned to its normal position and stitched as may be necessary to close the incisions.

After the one or more implant members have been installed and the incisions permitted to heal, the prosthetic device, be it a crown or bridge, is then installed using a suitable cement as illustrated in FIGS. 2 and 3.

Modifications of the implant member illustrated in the preferred embodiment will readily suggest themselves to those skilled in the art. For example, surfaces 26 may be replaced with a variety of other means for accepting suitably designed insert tools, e.g., a slotted head, or a transaxial bore through frustum conical section 24.

It will also be understood that in the practice of the present invention, it is contemplated that dental implant members of varying lengths and diameters will be required to satisfy a full range of implant conditions. For purposes of illustration only, and without intending to limit the scope of the invention, a typical implant member will have the following dimensions:

LENGTH Shank Portion .315 in. Cylindrical Section .040 in. Threaded Portion .394 in. DIAMETER (OVERALL) .134 in. THREADED PORTION Thread pitch 20 Major diameter .134 in. Minor diameter .102 in. Width of flat at crest .008 in. Leading flank angle 45.degree. Trailing flank angle 14.degree. 30'

While the invention has been described with reference to certain specific embodiments, neither the embodiments illustrated nor the terminology employed in describing them is intended to be limiting; rather it is intended that the scope of the invention be limited only by the terminology of the appended claims.

Claims

Having thus disclosed our invention, We claim:

1. A dental implant member formed of a generally cylindrical body consisting of

a. a threaded portion adapted to lie in bone having upper and lower ends, said threaded portion defined by a plurality of thread convolutions terminating radially of said body in thread crest and separated axially along said body by thread flanks, and

b. a shank portion having an upper end, and a lower end coterminus with the upper end of said threaded portion, said shank portion consisting of:

i. a cylindrical section adapted to lie in tissue defining the lower end of said shank portion and extending upwardly a distance of at least about .5 mm. from the terminus of the upper thread flank of the uppermost thread convolution defining said threaded portion, the periphery of said cylindrical section and said thread crest lying in a plane parallel to the axis of said generally cylindrical body thereby providing a smooth transition from threaded portion to cylindrical section, essentially constant in radius of curvature, at the location on the installed implant member, which is surrounded by the juncture between bone and tissue, and

ii. a conical frustum section having its base coterminus with the upper end of said cylindrical section.

2. The dental implant of claim 1 formed of a ceramic composition comprising at least about 95 wt. % aluminum oxide.

3. The dental implant member defined in claim 1 further comprising means formed in said conical frustum section for drivingly connecting said dental implant member with an insert tool.

4. The dental implant defined in claim 3 wherein said last mentioned means comprises a pair of opposed, generally flat, parallel faces.