An oral implant for supporting an artificial tooth structure

Abstract: A submergible screw-type oral implant includes a threaded angular shaft (24) connected at one end to an implant portion (10) in a bore in the patient's bone (11) in which the implant is installed, the other shaft end being at a preselected angle to the one end and adapted for threaded engagement with a support (31) for an artificial tooth structure. The implant further includes a beveled transition collar (21) located about the shaft (24) between the implant portion (10) and the support (31). The collar (21) has one end surface (23) at a right angle to its axis and the other end surface (25) at an angle with respect to the one end surface, the angle being substantially the same as the shaft angle. Threading of the support (31) onto the shaft (24) causes the support (31) and the implant portion (10) to frictionally engage the collar (21), thereby impeding disconnection of the shaft (24) and of the support (31) from the implant portion (10).

Description: This invention relates to dental implants and, more particularly, to submergible screw-type implants. Screw-type implants are well know in the art. U.S. Patent No. 3,499,222 of L. I. Linkow et al. discloses screw-type implants which may be buried in the alveolar ridge crest bone of a patient in an edentulous region. The implant has a threaded lower portion which may be screwed into an opening created in the bone after the tissue has been displaced. A coronal portion protrudes above the bone and is used to support an artificial dental appliance, e.g. an artificial tooth or bridge. In more recent years submergible implants have been created in which the threaded portions of the implants can be completely embedded in the bone. They may then be covered with tissue and allowed to remain in place while new bone grows around the implant and through vent holes in it. Once it is firmly anchored in new bone (3 to 6 months), the tissue is reopened and an upper post portion is screwed into the implant portion and is used to mount the artificial dental device (cf. e.g. GB-A-2 119 258, being the closest prior art document). In order to align the artificial tooth or other dental devices with the other teeth of the patient, it may be necessary to have the post portion at an angle to the implant portion. This may be accomplished by bending the post portion so that its head is at an angle to the threaded shaft. This bending may be accomplished before the post is threaded into the implant portion or afterward. If the post is bent before attachment to the implant, the proper alignment is difficult to achieve. If bent after attachment, there is a danger that too much stress will be put on the implant portion and it will loosen in the bone and fail. Also bending the post may fatigue the metal of the post and cause breakage. The primary object of the present invention is to provide a dental implant which, in its preferred form, is of the submergible screw type and which allows the post for supporting an artificial dental appliance to be positioned in proper alignment with other teeths in the patient's mouth without applying stress to the implant. Another object of the invention is to provide a dental implant with angular orientation of the prosthesis, which is simple in construction and easy in installation. In order to accomplish the foregoing objective, the present invention provides an oral implant for supporting an artificial tooth structure comprising an implant portion adapted to be fitted in an opening in a bone of a patient in the vicinity of the occlusal plane, which bone has been exposed by an incision in the covering of fibromucosal tissue, and a support for an artificial tooth structure extending at a preselected angle to the implant portion, a threaded shaft connected at one end to an outer end of said implant portion which is directed away from the opening in the bone when the implant portion is installed therein, the other end of the shaft being adapted for connection with said support, and a beveled transition collar located about the shaft and between the upper end of the implant portion and the support, the collar having one end surface at a right angle to the collar axis and the other end surface being at a pre-selected angle with respect to the one end surface which is substantially the same angle as the pre-selected angle at which said support extends from said implant portion, the support being in contact with the collar and being connected to the implant portion, the shaft being effective to cause the support and the implant portion to frictionally engage the collar, thereby impeding disconnection of the shaft, collar and support from the implant portion. In a preferred embodiment of the invention, the implant portion of the device includes a threaded region that contains a longitudinal channel through a portion of the outer parts of the threads. The channel is wider toward its bottom. One side of the channel is at a right angle to the implant circumference so as to create a cutting edge that assists in the formation of a self-tapping capability for the implant when it is installed in a bore or opening in the patient's bone. The other side of the channel is at an obligue angle to the circumference. The channel guides bone chips created during the threading of the implant toward the base of the bore in the bone. By terminating the channel below the uppermost threads, epithelial tissue is prevented from growing down into the bone along the channel. The post or abutment portion of the implant which supports an artificial dental appliance may be a separate piece from the implant portion and may be attached thereto at an angle by means of a connection portion of the abutment. According to the invention the connection portion is in the form of a rotatable beveled collar allowing the post to swivel about the axis of the implant portion. Once in place, means are provided for securing the abutment against further movement with respect to the implant portion. As a result the implant can assume a desired angle to assure proper alignment of the artificial dental structure with the other teeth of the patient along the occlusal plane. For installation of the inventive dental implant an incision is made in the tissue covering the alveolar ridge crest bone. This underlying bone is then exposed and a bore is drilled into the bone at a depth sufficient to hold the implant portion of the device. The bore is made slightly smaller in diameter than the implant device and is at an angle which will allow it to engage the major portion of the available bone. Then the implant portion is threaded into the remaining bone about the bone. It is typically buried at a depth such that it is submerged below the upper surface in the bone and is completely buried in the bone. Once secured in place a cover of minimal height may be attached to the exposed surface of the implant portion by a screw passing through the cover and threaded into an aperture in that surface. The tissue may then be sutured over the implant cover. New bone is allowed to grow and to anchor the cover and implant firmly in place. Several weeks or months later, the tissue is opened again and the cover is removed. A threaded abutment or post is then attached to the threaded aperture in the end of the implant portion. This abutment is used for supporting the artificial dental appliance. The angle at which the implant portion is located in the bone may not be the most conducive to the proper alignment or the artificial tooth or other dental devices with the remaining teeth of the patient. As a result, the abutment includes an angled, swivelable connection portion for attaching the abutment to the implant portion. According to the invention fixed angular devices which are rotatable about the longitudinal axis of the implant are utilized. After the abutment or support for the artificial tooth is properly orientated, it is locked such that it remains in that position. Finally, the tissue is closed about the abutment and the artificial tooth of bridge support is cemented or screwed to the abutment. The foregoing and other features of the present invention will be more readily apparent from the following detailed description and drawings of an illustrative embodiment of the invention, in which: Fig. 1 is a schematic cross section of the side of a patient's face showing the alveolar ridge crest with a screw type implant according to the present invention installed therein; Fig. 2 is an enlarged view of an illustrative embodiment of a completed screw-type implant according to the present invention with an angularly positioned threaded shaft attached thereto, and Fig. 3 illustrates a cross-sectional view through an implant portion of a dental implant according to a preferred embodiment of the invention, showing the cross-sectional shape of channels for shaving off pieces of bone during threading of the implant portion into the bone. The present invention contemplates at least a two part screw-type dental implant, i.e. an implant portion 10 which is buried in the bone of the patient and a post or abutment portion 20 which is attached thereto and which supports an artificial tooth structure 30. As shown in Fig. 1, an implant screw portion 10 is located in a bore in the aveolar crest 11 at an angle that causes it to be in the center of the thickest portion of good available bone. The abutment 20 is attached both to the implant portion 10 and the artificial tooth 30, and is set so that the tooth is at an angle to the implant which cause the tooth to be in proper alignment. In Fig. 2 the screw implant portion 10 of Fig. 1 is illustrated in more detail. This implant portion 10 contains threads 13 and the lower half of the implant portion 10 contains a cavity 14 (shown in dotted line). Also, spaced about the lower end of the implant are holes or vents 16, 16a and 16b, which penetrate from its exterior to the interior cavity 14 as illustrated in Fig. 3. The purpose of these vents is to allow new bone to grow through and into the center cavity in order to firmly anchor the implant in the patient's bone. As depicted in cross-section in Fig. 3 a channel 18 is cut through the threads 13 and possibly into the outer casing of the implant portion 10. The channel 18 is one of three channels 18, 18a, 18b in a typical implant portion. These channels are made to intersect the respective vents 16, 16a and 16b which are spaced at angles of 120° about the circumference of the implant portion 10. The channels do not extend completely toward the upper surface in order to prevent tissue from growing down along the channel, and to prevent the incursion of food and bacteria. It should be particularly noted in Fig. 3 that the channels 18 have one edge which is at about 90° to the circumference of the implant, i.e. surface 18′, and another more obliquely shaped edge, i.e. surface 18″. During installation of the implant, an incision is made in the gum tissue of the patient and the underlying bone is exposed. Then a drill or burr is used to make an opening or bore hole in the bone which is slightly larger in diameter than the implant portion 10, but which is not as wide as the threads 13. A wider counterbore may be provided to accommodate a protection collar. Next the implant is inserted up to the first thread in the opening in the bone. A tool, such as a wrench, is used to engage a hex portion 12′ and to rotate the implant. The threads 13 are made to be self-tapping so that the implant portion 10 will begin to screw dawn into the patient's bone. If necessary, a bone tap can be used to create grooves in the hard upper cortical bone prior to insertion of the implant portion 10. The right angle surface 18′ of the channel 18 also has self-tapping properties so as to ease the insertion of the implant, once it has reached the depth of the channels 18. Further turning of the implant causes the right angle surface 18′ to scrape off bone as the implant is being threaded and to push the resulting bone chips forward. This causes the bone chips to fall through the channels 18 and into the area of the vents 16, 16a and 16b where they may penetrate into the interior cavity 14. To facilitate this, the channels 18 are made wider towards the vents 16, 16a and 16b, resp.. As a result of this structure, bone chips created during the implant procedure tend to accumulate at the base of the implant in the patient's bone. Because of the autogenous nature of these bone chips they promote the growth of new bone in the area and speed the formation of new bone around and through the implant such that it is anchored in place more rapidly. In Figure 2 the upper part of the implant portion 10 is shown partly broken away to exhibit the interior cavity 14 and the threads 13. Towards the upper part of the implant portion is is shown in cross section. The implant portion 10 is provided with a hexagonal recess 12′ for rotation it into position in the bone. As shown in Figure 2 the screw type implant portion 10 is connected to an abutment portion 20 that includes a transitional collar 21, an angled threaded shaft 24, and a tooth support cylinder 31. The threaded shaft 24 has its lower end screwed into a threaded aperture 19′ in the implant portion 10. The upper end of the threaded shaft 24 which is set at an angle to the lower end, is received within a threaded aperture 35 in tooth support cylinder 31. This cylinder 31 contains a recessed portion 32 which may be utilized in fixing on to the cylinder via cement or some other convenient and well known method, a porcelain, plastic, or other dental tooth-colored veneering material in the form of an artificial tooth. The transitional collar 21 is located between the upper end of the implant portion 10 and the cylinder 31. This collar has an angled upper surface 25 and a perpendicular lower surface 23. The angle of the upper surface is made to equal the angle of the upper part of the angled shaft 24. While collar 21 surrounds threaded shaft 24, it does not engage its threads. During an installation procedure the implant portion 10 is located in the patient's bone as previously described. The gingival tissues can then be replaced over the implant portion 10 and several weeks or months allowed to pass while new bone grows around and through the implant portion 10. However, alternatively the artificial tooth can be connected to the implant immediately. Whichever manner is chosen, the attachment is accomplished by selecting an angled shaft 24 and transition collar 21 which have an angle which will cause the artificial tooth to be correctly aligned with the other teeth of the patient. Once the threaded shaft 24 is engaged with the implant portion 10, the collar 21 is slipped over the free end of the shaft 24. Then the shaft 24 is rotated so that it is firmly secured in the implant portion 10 and is extending in the proper direction. With the collar 21 in place over this shaft 24, the cylinder portion 31 is threaded over the open or free end of the shaft 24 until it makes tight contact with the upper surface 25 of the collar 21 and begins to squeeze the collar 21 between the cylinder and implant portions. Notches and recesses 22 and 27 are provided in the mating surfaces such that, once the parts are screwed together, these notches and recesses engage each other and prevent unintentional unscrewing of the portions of the implant. With this firm attachement completed, the artificial tooth can then be attached over the abutment cylinder 31. In Figure 2 the level of the patient's bone is shown as dotted line 70. Since the implant portion 10 is submerged in the bone, the line 70 intersects the lower portion of the transitional collar 21. The gum tissue line 72 is towards the upper portion of the transitional collar 21. As a result the collar 21 acts as a barrier to prevent the encroachment of bacteria and food into the interior portion of the collar 21 and the hex recess 12′ of the implant portion 10. With the embodiment of Figure 2 fixed angles are provided to the dentist and he must work with the standard angles and the angle which he creates for the bore in the patient's bone, in order to assure proper alignment of the teeth. Besides being used to mount a single tooth, the implants according to the present invention can be used as supports for a permanent bridge or a removable bridge. In the case of a removable bridge the abutment cylinder is in the form of small copings which can be spaced throughout the edentulous span of a patient. These copings support a bar onto which the bridge structure may be screwed or clipped.

Claims: An oral implant for supporting an artificial tooth structure (30) comprising an implant portion (10) adapted to be fitted in an opening in a bone (11) of a patient in the vicinity of the occlusal plane, which bone (11) has been exposed by an incision in the covering of fibromucosal tissue, a support (31) for an artificial tooth structure (30) extending at a preselected angle to the implant portion (10), a threaded shaft (24) connected at one end to an outer end of said implant portion (10) which is directed away from the opening in the bone (11) when the implant portion (10) is installed therein, the other end of the shaft (24) being adapted for connection with said support (31), characterised by a beveled transition collar (21) located about the shaft (24) and between the upper end of the implant portion (10) and the support (31), the collar (21) having one end surface (23) at a right angle to the collar axis and the other end surface (25) being at a pre-selected angle with respect to the one end surface (23) which is substantially the same angle as the pre-selected angle at which said support (31) extends from said implant portion (10), the support (31) being in contact with the collar (21) and being connected to the implant portion (10), the shaft (24) being effective to cause the support (31) and the implant portion (10) to frictionally engage the collar (21), thereby impeding disconnection of the shaft (24), collar (21) and support (31) from the implant portion (10). An oral implant as claimed in claim 1 wherein the surfaces of said collar (21), the upper end of the implant portion (10) and the support (21) have projections (22) and recesses (27) to increase the frictional engagement. An oral implant as claimed in claim 1 or claim 2 wherein the implant portion comprises an implant body (10) having threads (13) extending over at least part of its exterior surface and being adapted to be threaded into the opening in the bone (11) of the patient, and at least one channel (18) such that it at least extends through some of the threads (13) on the implant body (10) for directing bone chips toward a base portion of the opening in the bone (11), one edge (18′) of the threads (13) at one side of the channel (18) being substantially at a right angle to the circumferential direction of the threads (13) and the other edge (18″) of the threads (13) at the other side of the channel (18) being at an oblique angle to the circumferential direction of the threads (13), said one edge (18′) being adapted (i) to promote self-tapping of the threads (13) in the bone (11), (ii) to shave off pieces of bone (11) during threading of the implant portion (10) into the bone (11), and (iii) to direct the pieces of bone (11) into the channel (18) such that the channel (18) may direct the pieces toward the base portion of the opening.

Inventors: LINKOW LEONARD I, RINALDI ANTHONY W, LINKOW, LEONARD, I., RINALDI, ANTHONY W.
Applicants: VENT PLANT CORP, VENT-PLANT CORPORATION, INC.
Application year: 1991
Main classification: A61C8
IPC codes: A61C8