Dental implant anchor

Abstract: A dental implant anchor 32 includes a body portion 31 having a first external wall portion carrying one or more circumferential projections 33-39 separated by circumferential grooves 40-45 and, below, a second external wall portion carrying threads 46. In some forms, the anchor also includes one or more longitudinally-oriented grooves on its exterior wall. The grooves extend across, and through the circumferential projections. The implant can include a head portion 30 with a smooth external wall; a through-hole 47 and an apical hole 48 passing through the bottom of the anchor; and internal structure 50, 51 for engaging a tool for inserting the implant in a passage formed in bone tissue. This internal structure can be in a top portion, or in an internal passage in the body portion of the implant. A method for forming a passage in bone tissue to receive the implant includes forming a passage having a base with a diameter suited to self-tapping of the threaded part of the implant, and, above the base, a larger-diameter section to engage frictionally the circumferential projections. A drill 110 for forming such a passage in one step includes two such drilling portions 111, 112 that together form a two-diameter passage.

Description: This invention relates to dental implant anchors. GB-A-2 199 502 discloses a dental implant anchor comprising a substantially cylindrical body portion for fitting in a passage formed in bone tissue, the body portion having an external wall portion carrying a plurality of circumferential or partially circumferential projections, each projection having a cross-section sufficiently large to engage frictionally the sidewalls of a said passage to hold the anchor inside the passage immediately upon insertion into the passage, each of the circumferential projections having a groove on each side for facilitating growth of bone tissue into the grooves for anchoring of the dental implant anchor in a said passage, and, apically of the projections, an external wall portion carrying a thread at an oblique angle to the longitudinal axis of the anchor for screwing into the end of the passage. The present invention provides such an anchor characterised in that it further comprises at least two longitudinally extending grooves passing through and interrupting each projection, the longitudinal grooves being of sufficient depth and width to ensure bone growth into the grooves when the anchor is in the passage; Preferably, these grooves are about 0.25 mm to about 1.5 mm in depth and in width. This anchor preferably includes a top portion with the body portion carrying the plurality of anchoring means on its outer wall. In these preferred embodiments, the top portion has a smooth external wall that tapers upwardly and outwardly from the body portion to a diameter that is slightly larger than the diameter of the body portion. The top portion is sufficiently large in diameter to insure that the top portion fits snugly within, and tightly seals, by frictional forces, in the top of a passage formed in bone tissue to receive the dental implant anchor Alternatively, the top portion can be of substantially the same diameter as, or even of smaller diameter than the body portion of the implant. The dental implant anchor preferably includes, at its distal end, a through hole extending from one side of the body portion to the other to permit bone and associated tissue to grow through this opening. The distal end preferably also includes a passage at the bottom of the body portion that extends. upwardly inside the body portion a distance sufficient to permit blood and other tissue to pass upwardly, out the through-hole and up the longitudinally-oriented grooves, thus allowing the anchor to seat at the bottom of the passage formed in bone tissue to receive the implant. Preferably, this upwardly-extending passage is less than about one-third the length of the body portion. The anchor preferably has an internal passage extending downwardly from the top of the implant, and internal means for engaging and inserting the anchor into a passage formed in bone tissue to receive the implant. The internal anchor-engaging means permits insertion of the anchor in a passage formed in the bone tissue of a subject without countersinking the upper surface of the bone tissue, where the top portion of the anchor fits upon insertion of the anchor into such a passage. This internal means is, preferably, a wrench-engaging surface. In preferred embodiments, where the body portion is joinea to a top portion having an unthreaded, smooth exterior wall, the internal means for anchor insertion is inside this top portion. Alternatively, this internal means can be inside the body portion in an internal passage. Preferably, the top portion has a hex nut configuration on its inner wall surfaces for receiving a hex wrench, and has a cylindrically-shaped, smooth outer wall. Alternatively, the hex nut configuration can be within, and at or near the base of the passage inside the body portion, or formed within threads on the wall of this passage. In embodiments that include a top portion, the top porticn is open, and can be chamfered at its upper end, and is preferably axially aligned with an internal passage in the body portion. The passage can be threaded or unthreaded. This chamfered surface permits frictional locking with any adaptor or other insert fitted into the opening. The chamfered surface is preferably of sufficient size and depth to afford lateral stability to any adaptor or other insert fitted into the opening in the head portion, and forms a smooth, easily-cleaned margin with complementary adaptors placed in the top portion of the anchor. The anchor is preferably made of titanium or a titanium alloy containing 6% by weight of aluminum and 4% by weight of vanadium; preferably has an outside thread diameter in the range of about 3 to about 4.25 millimeters; an inside thread diameter in the range of about 2.25 to about 3.5 millimeters; and preferably has projections with an outside diameter that is substantially the same as, or about 0.25 millimeter larger than the thread diameter. The anchor preferably has a length in the range of about 5 to 20 millimeters. The implant anchors of this invention are adapted for insertion in specially-formed passages in bone tissue. Preferably, the method of forming such a passage includes forming a passage in the bone tissue having an upper portion with a length and a diameter suitable for engaging the circumferential or partially circumferential projections on the anchor by friction, and including, at the base of the passage, a smaller-diameter portion adapted to engage the self-tapping threads at the bottom of the anchor. The smaller-diameter portion at the base of the opening can be formed using a first drill having a cross-section appropriate to form a passage of this diameter and with length that is about the same as the length of the anchor to be inserted. Thereafter, the upper portion of the passage can be enlarged by a drill of appropriate diameter to accomodate the part of the body portion of the anchor with the circumferential or partially circumferential projections. Alternatively, the smaller diameter and larger diameter portions of the passage can be formed simultaneously using a drill having, at its end, a portion of a diameter appropriate for forming the smaller diameter portion of the passage, and an upper portion of larger diameter suitable for forming the upper portion of the passage. The implant anchor is tapped into the passage so formed until the bottom of the threaded portion reaches the top of the portion of smaller diameter at the base of the passage. Then, using an insertion tool to engage the wrench-engaging surface inside the anchor the anchor can be screwed into the smaller-diameter part of the passage until the threaded part of the anchor reaches the bottom of the passage. This invention can better be understood by reference to the drawings, in which: Fig. 1 is a perspective view of a first type of known dental implant anchor; Fig. 2 is a perspective view of a second type of known dental implant anchor; Fig. 3 is an elevational view, in cross-section, of a third type of known dental implant anchor; Fig. 4 shows the embodiment of the new dental implant anchor ; Fig. 4A is a top plan cross-sectional view, taken on line 4A-4A in Fig. 4, showing the width of the longitudinal grooves on the exterior wall of the fourth embodiment shown in Fig. 4; Fig. 4B is a longitudinal cross-sectional view, taken on line 4B-4B of Fig. 4, showing the depth of the longitudinal grooves shown in Fig. 4A; Fig. 1 shows a first type of known dental implant anchor generally designated 10. Anchor 10 includes body portion 11 joined to, and surmounted by top portion 12. Body portion 11 includes circumferential projection 16, called a flute, spaced from top portion 12 by circumferential groove 20 on body portion 11. Below flute 16 on body portion 11 are threads 15. At the bottom of body portion 11 is through-hole 14 which passes axially through body portion 11, and apical hole 13, formed at the bottom of anchor 10, and extending upwardly inside body portion 11 beyond through-hole 14. Top portion 12 is joined to, and surmounts body portion 11. Top portion 12 has a sidewall 17 that tapers upwardly and outwardly from the plane, near groove 20, where body portion 11 joins top portion 12. Atop top portion 2 is opening 19 with wrench-engaging surface 18 on the inner wall of top portion 12. This wrench-engaging surface 18 permits threading of anchoru 10 into a passage formed in bone tissue by means of a tool that fits inside anchor 10, obviating the need for any insertion tool-engaging means on the outside surface of anchor 10. Opening 19 can, in some embodiments, be in registration with a shaft formed inside body portion 11, and the wrench-engaging surface 18 can, in such embodiments, be at or near the base of the shaft internal to anchor 10. Fig. 2 shows a second type of known anchor , generally designated 32, that includes head portion 30 and body portion 31. Body portion 31 includes an external wall portion carrying a plurality of circumferential projections 33, 34, 35, 36, 37, 38 and 39. These projections are in planes parallel to one another and are separated from one another by grooves 40, 41, 42, 43, 44 and 45. Below circumferential flutes 33-39 is another wall portion carrying threads 46. The flutes facilitate seating the anchor frictionally in a passage formed in bone tissue by tapping the anchor into such a passage. Threads 46 at the bottom of body portion 31 permit the anchor to be screwed into the bottom of such a passage. Thus, the anchor can be held in place in such a passage by both the flutes and the threads, or by either one alone if the other fails. Anchor 32 also includes through hole 47 and apical opening 48 which correspond to, and perform the same functions as openings 13 and 14, respectively, in Fig. 1. Top portion 30 includes opening 50 and wrench-engaging surface 51, which are identical to, and function the same as opening 19 in wrench-engaging surface 18, respectively, in Fig. 1. As in Fig. 1, the opening 50 may be in registration with a shaft internal to body portion 31, and the wrench-engaging surface 51 can lie inside the shaft instead of inside head portion 30. Fig. 3 shows a third type of the known dental implant anchor. In most respects, this anchor is identical to the anchor shown in Fig. 1, except that the internal wrench-engaging surface 19' lies at the bottom of the internal passage inside the anchor instead of on the internal surfaces of the top portion of the anchor. While Fig. 3 shows the internal passage, below the top portion, to be partially threaded to receive and engage with threaded or unthreaded inserts such as dental prostheses, the threading is not mandatory, and the walls of the internal passage can, in alternative embodiments, be smooth instead of threaded, or partly threaded or partly smooth. Fig. 4 shows the embodiment of the new dental implant anchor. In most respects, the anchor, of Fig. 4 is identical to those shown in Figs. 2 and 3. However, the outer wall surfaces 100 (Fig. 4) of this anchor 102 have two longitudinally-extending grooves 105/106 (Fig. 4) that are diametrically disposed on opposite sides of the other wall and that extend from just below the base of the top portion entirely through the circumferential projections from top to bottom. These grooves interrupt, and extend across and through these circumferential projections on each side of the anchor. These grooves are of sufficient depth and width, here about 0.25 mm to about 1.5 mm in depth (see Fig. 4B) and in width (see Fig. 4A), to insure that bone tissue will grow into these grooves enhancing the anchoring of the anchors to the bone tissue. The rounded flutes provide a surface adapted to receive coatings of material such as hydroxyl apatite or other bone substitute materials. The flutes also provide irregular surfaces for better distribution of stresses on the anchor from dental prostheses attached thereto. The upwardly, outwardly tapered head portion insures that anchor when inserted in a passage formed in bone tissue of sufficient depth to receive the entire anchor, seats firmly and snugly at the mouth of the passage. The openings and the longitudinally-oriented grooves permit blood and other tissue at the bottom of a passage formed in bone tissue to receive these anchors to pass upwardly so that the anchors can seat fully at the bottom of such a passage.

Claims: A substantially cylindrical dental implant anchor (102) comprising a substantially cylindrical body portion for fitting in a passage formed in bone tissue, the body portion having an external wall (100) portion carrying a plurality of circumferential or partially circumferential projections, each projection having a cross-section sufficiently large to engage frictionally the sidewalls of a said passage to hold the anchor inside the passage immediately upon insertion into the passage, each of the circumferential projections having a groove on each side for facilitating growth of bone tissue into the grooves for anchoring of the dental implant anchor in a said passage, and, apically of the projections, an external wall portion carrying a thread at an oblique angle to the longitudinal axis of the anchor for screwing into the end of the passage, characterised in that the anchor further comprises at least two longitudinally extending grooves (105,106) passing through and interrupting each projection, the longitudinal grooves being of sufficient depth and width to ensure bone growth into the grooves when the anchor is in the passage. A dental implant anchor (102) according to claim 1 further comprising, above the body portion, a top portion having a smooth external wall, the top portion slanting outwardly and upwardly from the plane through the body portion where the body portion joins the top portion. A dental implant anchor (102) according to claim 1 or 2 further comprising means internal of the anchor for engaging means for inserting the anchor in a said passage. A dental implant anchor (102) according to any preceding claim further comprising a through-hole passing laterally through the body portion near the bottom of the body portion. A dental implant anchor (102) according to claim 4, further comprising an apical hole in the body portion of the implant extending upwardly inside the body portion beyond the through-hole. A dental implant anchor according to any preceding claim including two longitudinal grooves (105,106) on opposite sides of the external wall (100) portion, each intersecting the projections substantially at right angles. A dental implant anchor according to any preceding claim in which the circumferential axis of each projection is substantially normal to the longitudinal axis of the anchor.

Inventors: NIZNICK GERALD A, NIZNICK, GERALD A.
Applicants: CORE VENT CORP, CORE-VENT CORPORATION
Application year: 1990
Main classification: A61C8
IPC codes: A61C8