Abstract:
An anchor apparatus having a threaded post for threaded engagement with bone, and an upper circular receptacle. An angled support having a lower circular base and an upper female prosthesis receptacle is secured within to the implant anchor, the securing being through lower circular base being engaged with and adhered to the upper circular receptacle of the implant anchor. The circular base has a first longitudinal axis and the upper female prosthesis receptacle has a second longitudinal axis forming a mounting angle with respect to one another. A dental prosthesis having a male extension shaped for cooperative engagement with the upper female prosthesis receptacle of the implant anchor is secured to the implant anchor by such cooperative engagement. An alternate embodiment integrates the threaded post and the female prosthesis receptacle into a single member, for a zero degree angle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed toward a method and apparatus for an implant anchor for a dental prosthesis and, more particularly, a one-piece threaded implant anchor with an upper receptacle, for insertion into an oral cavity, into which an angled or straight prosthesis support is secured, for removable attachment of a dental prosthesis. 
     2. Related Art 
     Various methods and structures for anchoring appliances in the oral cavity are known in the art. For example, U.S. Pat. No. 4,540,367, issued to Sulc, (“the &#39;367 Sulc patent”) describes a multi-piece apparatus having a female member which attaches to a surface of a tooth adjacent to an apparatus anchoring site. Also shown in the &#39;367 Sulc patent is an oral appliance containing a male member which attaches to the female member. The apparatus and method described by the &#39;367 Sulc patent, although particularly useful for attaching to a dental surface adjacent to a desired anchoring site, is not optimal for all anchoring requirements. 
     Another anchoring method and apparatus is described by U.S. Pat. No. 5,749,732, issued to Sendax (“the Sendax patent” or “Sendax”). The apparatus described by the Sendax &#39;patent comprises a threaded anchor post having a square male upper extension. Using a wrench having a square socket, the threaded portion is rotated to attain threaded engagement with a bone. After the threaded portion has penetrated the bone to a suitable depth the square male upper extension remains above the gum. The threaded post portion has a lower threaded portion and an upper threaded portion separated by an unthreaded land. The Sendax patent describes the unthreaded land as functioning to assist bone growth engagement, thereby securing the anchor from unthreading. The square upper extension mates with, and is secured by adhesive to an oral appliance having a corresponding square receptacle. 
     There are commercially available anchors similar to the device described by Sendax but without the unthreaded land. 
     The apparatus and method described by the Sendax patent, and the similarly structured commercial products have shortcomings. One is that the upper extension and its cooperative fit with a dental appliance offers little, if any, adjustment after insertion. More particularly, the orientation of the upper extension is fixed by the rotational angle and insertion angle of the threaded portion. The orientation of the receptacle in the dental appliance, which is shaped to correspond to the upper extension, is also fixed relative to the appliance. However, after the threaded portion is screwed into the recipient&#39;s bone, changing its angle requires removal and re-insertion. After a period of time bone growth fixes the rotational position as well. Therefore, after insertion of the threaded anchor the angle and position of the dental appliance is substantially fixed. 
     Various methods and apparati for adjusting the angle of a dental appliance anchor are known. For example, U.S. Pat. No. 4,713,04, issued to Linkow et. al (“Linkow”) discloses an implant placed in the bone and rotated into a proper orientation. Linkow shows a wedge shaped collar having an angled upper surface, which is described as positioned to coincide with the angle of the shaft so that the free end of the shaft extends perpendicularly from the angled surface. Linkow further shows a prosthetic tooth anchor threaded onto the free end of the shaft, to secure the collar in a fixed orientation. The Linkow apparatus and method, although directed to an alignment issue, is relatively complex and may have insufficient structural rigidity for some applications. 
     While the above-identified and other references describe apparati and methods for aligning prosthetic teeth and other dental appliances, there are various shortcomings. One is complexity of the apparatus. Another includes the difficulty of installation. Other shortcomings include screw access holes on the chewing surfaces of the prosthetic teeth, and limited serviceability of wear components. 
     SUMMARY OF THE INVENTION 
     An anchor apparatus according to the present invention comprises an implant anchor having a threaded post and an upper circular receptacle, and further comprises a support having a lower circular base having a first longitudinal axis and an upper female prosthesis eyelet, or receptacle, having a second longitudinal axis, the second longitudinal axis and the first longitudinal axis forming a mounting angle with respect to one another, wherein the circular base of the angled support is secured within the upper circular receptacle of the implant anchor. 
     A further aspect of an anchor apparatus according to the present invention comprises the circular base of the angled support being secured within the upper circular receptacle of the implant anchor by an interference fit and an adhesive. 
     Another aspect of an anchor apparatus of this invention is in accordance with any of the above-summarized aspects, further comprising a dental prosthesis having a male extension shaped for cooperative engagement with the upper female prosthesis receptacle of the implant anchor, wherein the dental prosthesis is secured to the implant anchor by such cooperative engagement. 
     The present invention provides a method for anchoring an appliance into an oral cavity having a step of threading an implant anchor having a threaded post into a bone, the implant anchor having an upper circular receptacle, applying an adhesive to an angled support, the angled support having a lower circular base and an upper female prosthesis receptacle, the circular base having a first longitudinal axis and the upper female prosthesis receptacle having a second longitudinal axis, the second longitudinal axis and the first longitudinal axis forming a mounting angle with respect to one another, inserting the circular base of the angles support into the circular receptacle, rotating the circular base about the first longitudinal axis within the circular receptacle until the second longitudinal axis points in a desired direction, and allowing the adhesive to set. 
     A further aspect of the method of this invention is in accordance with the previously summarized method, further comprising the additional step providing a dental prosthesis having a male extension shaped for cooperative engagement with the upper female prosthesis receptacle of the implant anchor, and attaching the dental prosthesis by such cooperative engagement. 
     A still further aspect of the method of this invention is in accordance with any of the previously summarized methods, and further comprising the steps of providing a plurality of the angled supports, each of the plurality having a respective mounting angle; providing an alignment apparatus; inserting the alignment apparatus into the female prosthesis receptacle to determine which of the plurality of angled supports achieves a desired position for a dental prosthesis, and using the determined angled support for the steps of applying an adhesive and inserting the circular base of the angles support into the female prosthesis receptacle. 
     In view of the above-identified and other shortcomings in the prior art, an object of the present invention is a dental appliance anchor having a simple but strong structure that is easy to install. 
     Another object is a dental appliance anchor that provides ready adjustability in orientation and position. 
     Another object is a dental appliance anchor in which wear components can be readily replaced without a complete removal of the anchor. 
     These and other objects, features and advantages of the present invention will become more apparent to, and better understood by, those skilled in the relevant art from the following more detailed description of the preferred embodiments of the invention taken with reference to the accompanying drawings, in which like features are identified by like reference numerals. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side projection view of an assembled anchoring apparatus according to the present invention; 
     FIG. 2 is a top projection view of the assembled anchoring apparatus of FIG. 1, seen from view line “ 12 - 2 ”; 
     FIG. 3 is a side projection view of an implant anchoring member of the FIG. 1 apparatus, prior to assembly; 
     FIG. 4 is a cut-away enlargement view of the female circular receptacle and portion of the threaded shaft of the FIG. 3 implant anchoring member, seen from cut line “ 5 — 5 ”; 
     FIG. 5 is a side projection view of an example upper female eyelet of the FIG. 1 anchor apparatus; 
     FIG. 6 shows a perspective view of the example upper female eyelet shown by FIG. 5 detailing its slotted lower base; 
     FIG. 7 is an enlargement of the view area in FIG. 4 labeled “ 9 ”; 
     FIG. 8 is an enlargement of the view area in FIG. 4 labeled “ 10 ”; 
     FIG. 9 is cut-away projection of an embodiment of this invention having a zero degree female eyelet integral with the threaded implant; and 
     FIG. 10 is an enlargement of the view area in FIG. 9 labeled “ 12 ”. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     1. Overview 
     An example anchoring apparatus according to a first aspect of the present invention will be described in reference to FIGS. 1-7. FIG. 1 shows one variation of the example of FIGS. 1-7 after assembly in an oral cavity as described herein. FIGS. 2-7 show examples of, and are used for description of, the two major components of the FIG. 1 assembly, which are the anchor implant member, labeled as item  11  in FIG. 1, and the upper removable support member, labeled as item  13  in FIG.  1 . The relative position labels of “above” and below are in reference to the “A” direction line shown in FIG. 1, with an item “above” another item meaning the former to have a position further in the “A” direction. Example methods according to the present invention, by which an apparatus as shown in FIG. 1 is secured and assembled within an oral cavity, will be described. 
     FIG. 9 depicts an example implant anchoring apparatus according to a second aspect of the present invention. The aspect that FIG. 9 examples includes in a single anchor member the functions of anchor implant member  11  and the upper removable support member  13  of the FIG. 1 assembly embodiment. As will be understood, the aspect of FIG. 9 is limited to, but exploits, installations where the optimal angle between the FIG. 1 anchor implant member and the FIG. 1 upper removable support member is zero degrees. 
     2. Detailed Description 
     FIG. 1 shows a side view of an example of an anchoring apparatus after installation and assembly according to the method of the present invention. FIG. 2 shows a perspective of the FIG. 1 example, seen from view line “ 2 — 2 ”. 
     The FIG. 1 apparatus comprises an implant anchor member, labeled as item  11 , and an upper angled support member, labeled as item  13 . The implant anchor member  11  comprises a threaded shaft  14  and a receptacle base  16 . An example is described in greater detail in reference to FIGS. 3-4. The FIG. 1 apparatus is assembled as it is installed in an oral cavity, as will be described. After installation, the implant anchor member  11  is substantially below the gum line (not shown), with the threaded portion  14  threaded into an underlying bone 
     Referring to FIGS. 1 and 3, an example implant anchor member  11  is a unitary metal structure, preferably formed of a titanium-aluminum-vanadium alloy, having a threaded shaft  14  and an upper support  16 . The threaded shaft has an outer thread diameter of TD, and preferably has a tapered end  14 A, the tapered end having, for example, a taper angle of T degrees blending to a radius R1. Example values for these dimensions are TD=2.21 millimeters; R 1 =0.25 millimeters; and T=12 degrees. The taper T and radius R 1  are for improved self-threading and implant into bone. The threaded shaft  14  extends a distance D 1  from a lower surface  16 A of the upper support  16 . Preferably, for purposes of strength, a radius R 2  merges the base  14 B of the threaded shaft  14  to the surface  16 A. Example values are D 1 =10, 13 or 15 millimeters, and R 2 =0.75 millimeters. 
     As shown in FIG. 1, the upper support portion  16  of the implant anchor  11  has a first height H 1  in the “A” direction, and has a gripping surface  16 G formed on an outside upper portion for a second height H 2 . Example values are H 1 =1.22 millimeters; and H 2 =0.77 millimeters. As will be described, the gripping surface  16 G is for a wrench (not shown) to engage and apply rotation to the implant anchor member, for threading it into a bone. 
     FIG. 3 shows a side view of an example implant anchor  11  before insertion of the angled support  13 . As seen in FIG. 1, the gripping portion  16 G of the depicted example implant anchor  11  has a hexagonal shape. The hexagonal shape is for purposes of example only. Other shapes contemplated by the invention include, but are not limited to, square, two-sided, and pentagonal. 
     FIG. 4 shows a cut-away elevation view of the upper support  16  section of the implant anchor  11  of FIGS. 1 and 3 and a portion of the threaded shaft  14 , seen from the cut-line “ 5 — 5 ”. Formed within the upper support  16  is a female receptacle  18 . The female receptacle  18  is preferably a circular receptacle having a major depth H 7  and a ridge  18 R spaced by an under-cut  18 U from the bottom surface  18 L. 
     As will be understood from the description below, the undercut  18 U functions as a reservoir for adhesive that is used during the assembly operation. As will also be understood, the function of the female receptacle  18  is to accommodate, and secure from axial movement during positioning, a base  20  of the upper angled support member  13 , while allowing temporary rotation of the member about its axis AX. For these and other reasons, it will be understood that the specific form and dimension of the ridge  18 R and undercut  18 U is dictated, in part, by the form and dimension of the base  20 . 
     Referring to FIG.  4  and FIG. 8, where FIG. 8 shows a detailed view of the FIG. 4 labeled area  10 , the depicted example female receptacle  18  has an undercut  18 U extending from the lowermost surface of the receptacle  18 , labeled  18 L, to a point H 6  below the upper surface, labeled  18 H. The diameter of the undercut  18 U is labeled DM 1 . The ridge  18 R preferably has a radius R 4  and a cut-back CB. As will be understood from FIGS. 6 and 7 described below, the cut-back GB permits the sections  20 A through  20 D to expand and, thus, lock into engagement with the receptacle THETA angles at 0, 5, 11 and 17 degrees. 
     The radius R 4  of the depicted example begins at a height H 4  below the upper surface  18 H and ends at point H 5 , with the cut-back GB extending down to H 6 . The inner diameter DM 2  formed by the ridge  18 R is for an interference fit with the lower base  20  of the angled support member  13 , as described in greater detail below. The interference fit is preferably firm, yet should permit rotation of the angled support member  13  about the axis AX prior to the adhesive setting, as described below. Therefore, the inner diameter DM 2  is preferably held to a close tolerance, such as, for example, plus or minus 0.005 millimeters. Above the ridge  18 R is a larger circular opening, having a diameter DM 3 , with a radius R 5  at its opening to facilitate insertion of the base  20 . 
     Example values for the above-identified dimensions are DP 1 =1.49 millimeters; DM 1 =3.56 millimeters, with an example tolerance of plus or minus 0.025 millimeters; DM 2 =2.97 millimeters, with an example tolerance of plus or minus 0.005 millimeters; R 4 =0.307 to 1.05 millimeters; F=0.25 millimeters; R 5 =0.15 millimeters; H 3 =0.77 millimeters, with an example tolerance of plus or minus 0.005 millimeters; H 4 =1.07 millimeters; H 5 =1.36 millimeters; and H 6 =1.48 millimeters. 
     FIG. 7 shows an enlargement of the threads  14 T within the region of FIG. 7 labeled “ 9 ”. As seen from FIG. 7, the threads  14 T preferably have a substantially flat top land TL, with a lower land TR that is angled by TA degrees, with a typical TA value being 45 degrees. 
     It will be understood that the example receptacle  18  described above is for purposes of explaining the operation of, and providing general guidance in the practicing of this invention. Upon reading this disclosure, other structures for the receptacle  18  which provide for rotation of the angled support  13  prior to setting of its adhesive can be readily identified by persons skilled in the art. 
     FIGS. 5 and 6 show, in a side projection and perspective view, an example upper angled support  13 . The example angled support  13  includes a slotted lower base  20 , a wedge mid-base  22 , and an upper angled female eyelet  24 . Referring to FIG. 5, the upper angled female eyelet  24  includes a cavity  24 A with a ridge  24 B. The inner diameter at the ridge  24 B is labeled D 8 . The cavity  24 A and ridge  24 B, in accordance with the diameter D 8 , securely hold a dental prosthesis such that depicted by U.S. Pat. No. 5,195,181, issued to Sulc, (“Sulc &#39;181”), and U.S. Pat. No. 4,540,367, issued to Sulc (“Sulc &#39;367”), both of which are hereby incorporated by reference, by engagement with its male extension installed in a recess at the bottom of the prosthesis. 
     The slotted lower base  20  of the angled support  13  preferably has multiple sections, which can resiliently move radially when the base  20  is inserted into the circular receptacle  18  of the anchor implant  10 , as is described below. The depicted example has four sections, labeled  20 A,  20 B,  20 C and  20 D, separated by slots  26 . 
     The slotted lower base  20  and wedged mid-base  22  are substantially circular about an axis AX. The upper surface of the wedged mid-base  22 , as can be seen in FIG. 5, supports the female eyelet  24  at an angle THETA, which is measured between the axis AX and the axis AY of the female eyelet  24 . As described below, a method according to this invention contemplates selection of the desired THETA angle at the time the described apparatus is installed into an oral cavity. The present inventor has identified example sets of THETA angles which keeps the inventory manageable yet accommodates a wide and acceptable range of requirements. A preferable set of THETA angles is 0, 5, 11 and 17 degrees. This set, however, is not a limitation, as others may be identified and used by persons skilled in the art. 
     A preferred material for the angled support member  13  is a titanium alloy. 
     Sulc &#39;181 and Sulc &#39;367 show a dental prosthesis having a male extension which is placed over and engaged into the female eyelet  13 . 
     As described in Sulc &#39;181 and Sulc &#39;367, the male extension within the dental prosthesis is preferably formed of a plastic material having sufficient strength and durability to permit repeated connection and disconnection with the female eyelet  13 . In addition, the material of the male extension should develop a retaining friction between it and the material of the female eyelet  13  to maintain attachment of the male extension and, accordingly, the attachment of the dental prosthesis. Further, the material of the extension  30  should permit removal and reinsertion of the male cap when desired. This is preferred because the male extension typically absorbs wear due to time and chewing forces and, as a result, should be periodically replaced. An example material for the male extension is strong nylon. An example replacement technique by which one male cap is removed and replaced by another is described the Sulc &#39;367 patent. 
     An example method for installing an anchor, using the implant anchor  11  and angled upper support  13  of this invention, will be described. 
     First, the installation site is prepared using established methods within the dental and oral surgery arts. Next, the bone is pre-drilled, using a drill bit diameter and drilling depth selected by one skilled in the relevant arts. The tapered end  14 A of the threaded shaft  14  of the implant anchor  11  is then placed into the drilled area and, using a wrench corresponding to the grip  16 G, the implant anchor  11  is screwed into the bone until the surface  16 A is at the desired height. 
     Next, using the alignment handle described as item  50  in the Sulc &#39;181 patent, or by direct visual inspection, an appropriate THETA angle for the angled upper support  13  is chosen. As described above, typical THETA angles are 0, 5, 11, and 17 degrees. Therefore, in a typical method according to this invention, the dentist or oral surgeon would have an assortment of angled upper supports  13 , having THETA angles such as the examples identified above. 
     A dental prosthesis such as that shown in Sulc &#39;181 having a male extension is then placed over and engaged into the female eyelet  13  as described above. 
     As described in the Sulc &#39;181 patent, a temporary cap, such as the item labeled as item “ 40 ” therein, may be installed into the female eyelet  24  until a prosthesis becomes available. 
     FIG. 9 shows a further aspect of this invention, which exploits the occasions when the optimal THETA angle is found to be zero degrees. In this situation there is no need to have separate members  11  and  13  and, accordingly, this aspect of the invention integrates the functions of those members, with respect to anchoring in bone and supporting a dental prosthesis, into a single member  50 . FIG. 10 is a detailed view of the area in FIG. 9 labeled “ 12 ”. 
     Referring to FIG. 9, an example of this aspect of the invention includes a single prosthesis support member  50  having a threaded structural portion  14 ′ and an upper eyelet structural portion  24 ′. The portion  14 ′ corresponds to, and may be identical to, the threaded shaft  14  of FIG. 4, and the portion  24 ′ corresponds to the structure labeled as  24  in FIG.  5 . 
     While the present invention has been disclosed with reference to certain preferred embodiments, these should not be considered to limit the present invention. One skilled in the art will readily recognize that variations of these embodiments are possible, each falling within the scope of the invention, as set forth in the claims below.