FIELD OF THE INVENTION

[0001] The present invention generally relates to a method and a dental system employing a magnet for taking dental impressions.

BACKGROUND OF THE INVENTION

[0002] Various methods have been used for taking impressions of the oral cavity in order to fabricate prosthetics in dentistry such as for producing crowns for implants. Mechanical attachment methods have been among the main methods used in taking such impressions. Recently various magnetic attachment systems used in magnetic attachment methods utilizing small magnets have been developed for use in taking dental impressions. These systems may also be referred to as magnetic retention systems, magnetic systems, magnetic anchor attachment systems, rare earth attachment systems, and so forth.

[0003] Magnetic attachment systems have advantages over mechanical attachment systems in that excessive stress on the implants at the time of the removal of the dental impression may be eliminated, and the preparation/removal operation of the dental impression itself is very easy. Additionally, the degree of the attachment force supplied by the magnet used may be controlled by using magnets of different sizes. Moreover, the magnetic attachments act non-directionally when inserting and removing a dental impression and they transmit little lateral force to the implants.

[0004] However, current magnet systems, elements and methods used in taking dental impressions are problematic for several reasons. For example:

[0005] A. When two or more implants 901 are adjacent to each other within the gingiva 900, the implants may be inadvertently angled with respect to each other (Fig. 1). This may be the result of poor manual techniques on the part of the dentist or the physical limitations in the jaw of the patient. Angled implants interfere with obtaining satisfactory dental impressions for use in the fabrication of prosthetics for use with implants. When using prior art methods for taking impressions, even small angular deviations from parallel may be problematic.

[0006] B. Additionally, as seen in Fig. 2 to which reference is now made, when taking impressions, using first keeper 905, made of a magnetic field responsive material, and magnet 914 positioned in cap 908, gingiva 900 often extends 900A above first keeper 905. This makes it difficult to position cap 908 properly so that it will sit securely, without relative motion, on keeper 905. As discussed in greater detail below, such a situation can interfere with the quality of the dental impression obtained.

[0007] C. In some cases, as shown in Figs. 3A and 3B, the height of the gingiva 900 is below or at the same height as the height of the implant and second keeper 950 when an impression media 980 in an impression tray 990 is laid and cured during the taking of a dental impression. This results in cap 908 being embedded too far within impression material 980 as shown in Fig. 3A and 3B. When second keeper 950 and analog element 930 are inserted into cap 908 of Fig. 3B at a yet later stage of the impression taking process, a situation as shown in Fig. 3B results. The edges 981 of impression material 980 prevent the insertion of second keeper 950 into cap 908.

[0008] D. When pouring plaster for the impression, the impression analog, which in practice is often easily moved due to its length and the moments generated by the force(s) applied on it, is displaced somewhat decreasing the accuracy of the impression.

SUMMARY OF THE INVENTION

[0009] An object of the present invention is to provide a system for taking dental impressions based on the use of magnetic forces

[0010] Another object of the present invention is to provide a method for taking a dental impression using the system described herein.

[0011] Yet another object of the present invention is to make the taking of dental impressions simpler and more precise.

[0012] Yet another object of the present invention is to fabricate an accurate model of the oral cavity.

[0013] Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings. [0013] Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.

[0014] In one aspect of the present invention there is provided a second keeper assembly for use during a plaster pouring and curing stage of a dental implant impression taking process. The second keeper assembly includes: an analog element having a cavity therein and distal and proximal ends; a magnetic field providing element for providing a magnetic force and configured to include a cavity; a second keeper including: a body having first and second opposite surfaces, the surfaces substantially parallel to each other; a male member extending from the first surface for insertion into the cavity of the analog element; and an elongated projection formed of a magnetic field responsive material projecting from or through the second surface for insertion into the cavity of the magnetic field providing element and held therein, wherein the magnetic force provided by the magnetic field providing element acting on the elongated projection provides increased stability preventing displacement of the analog element when plaster is poured and cured during the impression taking process.

[0015] In an embodiment of the second keeper assembly the magnetic field providing element is formed at least partly of magnetic field providing material.

[0016] In another embodiment of the second keeper assembly, the elongated projection of the second keeper is formed separately from the body of the second keeper. The male member and the body of the second keeper and the analog element each contain a through-cavity, the through- cavities being in collinear registration with each other when the elongated projection is inserted from the distal end of the through-cavity of the analog element through the respective through-cavities of the male member and body of the second keeper. The elongated projection exits from the second surface of the body of the keeper and enters the cavity of the magnetic field providing element wherein the elongated projection is held. In this embodiment, sometimes the elongated projection is a screw.

[0017] In yet another embodiment of the second keeper assembly, the member of the second keeper is a truncated male member. The male member and the body of the second keeper have a continuous through-channel open at both ends. The second keeper assembly further includes a screw having threads and a head, the threads passing through the through-channel of the second keeper and the cavity of the analog element. The head is elongated and positioned to function as the elongated projection when inserted into the cavity of the magnetic field providing element.

[0018] In a further embodiment of the second keeper assembly, the magnetic field providing element is a substantially annular cylindrical element configured to receive therein the elongated projection from the second keeper, and formed at least partially of a magnetic field providing material.

[0019] In another embodiment of the second keeper embodiment the magnetic field providing element has a magnet attached thereto or encased therein.

[0020] In another aspect of the invention, there is provided a first keeper assembly for use during a polymeric impression material pouring and curing stage of a dental implant impression taking process. The implant has a cavity within it. The first keeper assembly includes: a first keeper including: a body formed of a magnetic field responsive material; and a male member extending therefrom for insertion into the cavity of the implant; a gum restraining element configured to encompass the implant and prevent gum tissue from interfering with the impression taking process; and a magnetic field providing element for providing a magnetic force to hold the body of the first keeper within the magnetic field providing element, thereby preventing displacement of the keeper when polymeric impression material is poured and cured during the impression taking process.

[0021] In another embodiment of the first keeper assembly of the present invention, the gum restraining element is pre-mounted on the first keeper.

[0022] In yet another embodiment of the first keeper assembly of the present invention, the gum restraining element is integrally formed with the first keeper.

[0023] In still another embodiment of the first keeper assembly of the present invention, the gum restraining element is a ring shaped or elliptical-shaped element.

[0024] In a further embodiment of the first keeper assembly of the present invention the male member of the first keeper is a truncated male member having a through-channel open at both ends. The first keeper assembly further includes a screw which is inserted into the through-channels of the body and then of the male member of the first keeper passing into the cavity of the implant, thereby functioning as part of the male member and extending its effective length.

[0025] In yet another aspect of the present invention there is provided a system for taking impressions of a dental implant, the implant having a cavity therein. The system includes: [0026] A. a first keeper system used for the stage of pouring and curing polymeric impression material the first keeper system including: a first keeper formed of a magnetic field responsive material comprising a body and a male member extending therefrom for insertion into the cavity of the dental implant; and a magnetic field providing element containing a cavity for providing a magnetic force to hold the body of the first keeper to the magnetic field providing element;

[0027] B. a second keeper system used for the stage of pouring and curing plaster performed after the prior stage and after removal of the first keeper from the cured polymeric impression material while leaving the magnetic field providing element embedded in the polymer impression material, the second keeper system comprising; an analog element with a cavity therein; and a second keeper formed of a magnetic field responsive material and comprising a body having first and second opposite surfaces, and having a male member extending from the first surface for insertion into the cavity of the analog element and also having an elongated projection projecting from the second surface for insertion into the cavity of the magnetic field providing element, the magnetic field providing element still embedded in the cured polymeric impression material obtained in the stage of pouring and curing polymeric impression material, the magnetic field providing element configured to receive therein the elongated projection of the second keeper, wherein the resulting magnetic force provided by the magnetic field providing element acting on the second keeper provides increased stability and prevents displacement of the analog element when plaster is poured and cured during the impression taking process. The first and the second keepers are attached to the implant/analog by integrated tread or separated screw.

[0028] In another embodiment of the system of the present invention the system includes a gum restraining ring for restraining gum tissue surrounding the dental implant preventing the gum tissue from interfering with the impression taking process.

[0029] In yet another embodiment of the system the gum restraining ring is pre-mounted on the first keeper.

[0030] In a further embodiment of the system the gum restraining ring is integrally formed with the first keeper.

[0031] In still another embodiment of the system, the elongated projection of the second keeper is formed separately from the body of the second keeper, and the male member and the body of the second keeper and the analog element each contain a through-cavity. The through-cavities are in collinear registration with each other when the elongated projection is inserted from the distal end of the through-cavity of the analog element and through the respective through-cavities of the male member and body of the second keeper. The elongated projection exits from the second surface of the body of the keeper entering the cavity of the magnetic field providing element wherein the elongated projection is held. In some cases in this embodiment the elongated projection is a screw.

[0032] In a further embodiment of the system of the present invention, the magnetic field providing element is a substantially annular cylindrical element formed, at least partially, of magnetic material and configured to receive the elongated projection from the second keeper. In some cases of this embodiment, the magnetic field providing element has a magnet attached thereto or encased therein.

[0033] In yet another embodiment of the system of the present invention, the first and second keepers are configured to include at least one notch or slot so that it receives at least one flange positioned on the magnetic field providing element.

[0034] In another embodiment of the system, the magnetic field providing element is formed at least partly of magnetic field providing material.

[0035] In a further embodiment of this system of the present invention, the magnetic field responsive material is stainless steel materials.

[0036] In still another embodiment of the system of the present invention, the first and second keepers are the same keeper and wherein when the keeper is used as the second keeper the elongated projection is an elongated element mechanically attached to the body of the second keeper and to the analog element and configured to be inserted into the cavity of the magnetic field providing element.

[0037] In yet another embodiment of the system of the present invention, the male member of the second keeper is a truncated male member. The male member and the body of the second keeper have a continuous through-channel open at both ends. The second keeper system further includes a screw having threads and a head. The threads pass through the through-channel of the second keeper and the cavity of the analog element. The head is elongated and positioned to function as the elongated projection when inserted into the cavity of the magnetic field providing element.

[0038] In a further embodiment of the system, the male member of the first keeper is a truncated male member having a through-channel open at both ends. The first keeper system further includes a screw which is inserted into the through-channels of the body and then the male member of the first keeper and then passing into the cavity of the implant, thereby functioning as part of the male member and extending its effective length.

[0039] In another aspect of the present invention there is provided a method for taking an impression of at least one dental implant in the mouth, each of the at least one dental implant having a cavity therein. The method includes the steps of: (a) inserting a male member of a first keeper element into the cavity of the implant, the first keeper being formed at least partially of a magnetic field responsive material; (b) positioning a magnetic field providing element on the first keeper element, the magnetic field providing element configured to have a cavity, and having a magnet positioned therein, thereby to supply a sufficient magnetic force so that there is an attraction between the magnetic field providing element and the first keeper element sufficient to hold them together with little, if any, relative displacement therebetween; (c) pressing an impression material onto the magnetic field providing element, allowing the impression material to cure, and then removing the cured impression material from the oral cavity with the magnetic field providing element still embedded in the impression material, and then further removing the first keeper from the magnetic field providing element.

[0040] The method further includes the steps of: (d) inserting a male member of a second keeper element into an analog element having a cavity, the second keeper element also having an elongated projection, the elongated projection being inserted through the magnet of the magnetic field providing element therein so that the second keeper element is secured to the magnetic field providing element by a magnetic force of sufficient magnitude so that there is little, if any, relative displacement between the magnetic field providing element and the second keeper element; (e) applying plaster material onto and around the analog element; (f) allowing the plaster material to cure, and after the plaster material is cured, taking the plaster material together with the analog element and the attached second keeper element and magnetic field providing element out of the impression material, and (g) removing the second keeper element from the analog element to obtain a reproduction of the interior of the cavity of the implant. [0041] In an embodiment of the method of the present invention, the method includes a further step of positioning a gum restraining element around the site in the gums where the dental implant is positioned and step (a) of inserting further includes first passing a male member of a first keeper element through the gum restraining element prior to inserting it into the cavity of the implant.

[0042] In yet another embodiment of the method of the present invention, a gum restraining element is pre-mounted on the first keeper prior to the effecting step (a) of inserting. In a further embodiment of the method of the present invention, a gum restraining element is integrally formed with the first keeper element.

[0043] In still another embodiment of the invention the elongated projection is a separate pin element and the analog element and the male member and body of the second keeper have through- cavities formed therein which are in collinear registration with each other when the analog element and the second keeper are in mechanical association with each other. Step (d) includes inserting the pin through the through-cavities from the distal end of the analog element towards and through the second keeper into the magnetic field providing element. The pin is inserted through the magnet therein so that the analog element is displaced only minimally when plaster material is poured and cured during the impression taking process. In some cases of this embodiment, the pin may be attached by mechanical means to the magnetic field providing element in addition to its being held by the magnetic field provided by the magnet of the magnetic field providing element.

[0044] In a further embodiment of the method, the first and second keepers are the same keeper. When the keeper is used as the second keeper the elongated projection is an elongated element mechanically attachable to the second keeper and sized and configured to be inserted into the magnetic field providing element. In some cases of this embodiment, the elongated projection is a screw formed of a magnetic field responsive material with a head sized and configured to be insertable and held in the magnetic field providing element by magnetic and mechanical forces.

[0045] In yet other embodiments of the method of the present invention, the method further includes a step of attaching the elongated element mechanically to the second keeper, thereby forming an elongated projection and then effecting step (d) attaching the male member of the keeper to the analog element. This is followed by inserting the elongated element into the magnetic field providing element, the elongated element being held therein by mechanical and magnetic forces. [0046] In another embodiment of the method the magnetic field providing element is formed at least partially of magnetic field providing material and the magnetic field providing element itself acts as the magnet.

[0047] In still another embodiment of the method, the magnetic field providing element is constructed as an annular cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will be more fully understood and its features and advantages will become apparent to those skilled in the art by reference to the ensuing description, taken in conjunction with the accompanying drawings, in which:

[0049] FIG. 1 is a schematic side view of implanted dental implants which would lead to difficulties during a subsequent dental impression taking process;

[0050] FIG. 2 is a cross-sectional view showing the effect on the impression taking process when the gingiva extend above the implant and keeper, thereby interfering with subsequent impression taking;

[0051] FIG. 3A is a cross-sectional view showing the effect on the impression taking process when the gingiva tissue reaches below or is at the same height as the implant head and keeper;

[0052] FIG. 3B is a cross-sectional view showing the effect on the impression taking process when the gingiva tissue reaches below the implant head and keeper, thereby interfering with subsequent impression taking;

[0053] FIG. 4 is a cross-sectional view of a gum restraining ring and a first keeper constructed according to an embodiment of the present invention;

[0054] FIG. 5 is a cross-sectional view of a gum restraining ring mounted on the first keeper of Fig. 4 and positioned above an implant into which it is to be inserted;

[0055] FIG. 6 is a cross-sectional view of a magnetic field providing element positioned above the first keeper prior to mounting thereto;

[0056] FIG. 7 is a cross-sectional view of the magnetic field providing element mounted on the first keeper, the magnetic field providing element being embedded in an impression material held by an impression tray; [0057] FIG. 8 is a cross-sectional view of the magnetic field providing element imbedded in an impression material in an impression tray which has been detached from the first keeper shown in Fig. 7;

[0058] FIG. 9 is a cross-sectional view of a second keeper on which an analog element is mounted which is positioned over the embedded magnetic field providing element of FIG. 8 and ready for insertion therein;

[0059] FIG. 10 is a cross-sectional view of a second keeper on which an analog element is mounted positioned in the embedded magnetic field providing element of FIG. 9 and on which a plaster impression is being taken;

[0060] FIG. 11 is a cross-sectional view of a second keeper on which an analog element is mounted and positioned in a dried plaster impression;

[0061] FIG. 12 is a cross-sectional view of an analog element positioned in a dried plaster impression after removal of the second keeper of FIG. 11;

[0062] FIGS. 13A and 13B show side and perspective views respectively of the first keeper shown in FIGS. 4-7 above;

[0063] FIGS. 14A and 14B show side and perspective views respectively of the magnetic field providing element shown in FIGS. 6-10 above;

[0064] FIGS. 15A and 15B show side and perspective views respectively of the second keeper shown in FIGS. 9-11 above;

[0065] FIGS. 16A-16E show perspective views of a second keeper with different shapes and/or constructions of its elongated projection;

[0066] FIGS. 17 and 18 show a cross-sectional exploded view and a perspective exploded view of another embodiment of the present invention;

[0067] FIG. 19 shows a perspective exploded view of a variant of the embodiment shown in FIGS. 17 and 18; and

[0068] FIGS. 20A and 20B shows a perspective exploded views of a variant of the embodiments shown in FIGS. 17-19.

Similar elements in the Figures are numbered with similar reference numerals. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] In the following, a principle and embodiments of the present invention will be described with reference to the accompanying drawings. Before explaining specific embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. In addition, any citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

[0070] The term "distal" as used herein refers to that portion of an element assembly or system furthest from the magnetic field providing element to which it is or can be attached. The term "proximal" refers to that portion of an element assembly or system closest from the magnetic field providing element.

[0071] The term "registration" as used herein means that the elements or channels or cavities and the like are aligned substantially collinearly.

[0072] The term "cavity" "channel" or "canal" as used herein have been used essentially interchangeably. In the case of the terms "cavity" "channel" or "canal" of the magnetic field providing element or the analog element or the keeper elements, The terms "through- cavity" "through- channel" or "through-canal" are used to indicate that these features extend through the length of the element. The "through" modified version of the terms "cavity" "channel" or "canal" is not necessarily intended to distinguish them from their unmodified variants.

[0073] In order to effect impression taking and to obtain a more accurate model of the oral cavity, the present invention provides a system of elements that includes a gum restraining ring 104 (FIG. 4), a magnetic field providing element 106 (FIGS. 14A and 14B) containing a magnet 106A, typically, but not limited to, a ring-shaped magnet, a first keeper element 102 (FIGS. 13A and 13B) having a male member 102B with the first keeper 102 formed of a magnetic field responsive material; and a second keeper element 130 (FIGS. 15A and 15B) being formed of a magnetic field responsive material having a male member 134 and an elongated projection 132. The male member 134 and projection 132 are each positioned on a different opposite surface 138 and 139 of the body 133 of second keeper element 130, the surfaces 138 and 139 being substantially parallel to each other. Each of these elements of the system will be discussed in greater detail in conjunction with a method for employing the system discussed below.

[0074] Reference is now made to FIGS. 4 and 5, where a side view of a gum restraining ring 104 is shown (FIG. 4). The ring is sized to slide onto a first keeper element 102 discussed below, essentially circumscribing keeper element 102 as shown in FIG. 5, effectively enlarging the keeper's outer diameter. In some embodiments the ring may be a split ring allowing for easier sliding of ring 104 over first keeper element 102. In other embodiments, ring 104 may be more elliptical than circular. In some embodiments, the gum restraining ring 104 is integrally formed with first keeper element 102 or with the magnetic field providing element 106.

[0075] In FIGS. 4 and 5, a first keeper element 102 is shown. A male member 102B extends from one surface of the keeper body 102F. Male member 102B is sized and configured to screw into or otherwise be inserted into a cavity 108B of an implant 108 (FIG. 5), the implant being firmly fixed to bone.

[0076] First keeper element 102 is made at least partially of a magnetic field responsive material such as stainless steel. A first surface 102E of keeper 102 and its opposite surface 102F, indicated by a dashed line, from which male member 102B protrudes are essentially flat. Body 102D of first keeper element 102 is typically at least partly cylindrical but it may have other shapes as well, such as an elliptical shape.

[0077] FIGS. 13A and 13B show side and perspective views, respectively, of first keeper element 102. The elements of these Figures are numbered as discussed above in conjunction with FIGS. 4 and 5. Notch 102G, shown in a cross-sectional view in FIGS. 5 and 13A, is best seen in the perspective view of FIG. 13B.

[0078] Returning again to FIG. 5, first keeper 102 encompassed by gum restraining ring 104 is shown positioned over implant 108, the latter embedded in gingiva 900. Implant cavity 108B receives first keeper 102 as in FIG. 6 to which reference is now made. Typically, but without limiting the invention, implant cavity 108B is threaded (not shown) to mate with threads 102C on first keeper 102, but in the Figures herein these threads are not always shown. [0079] In an alternate embodiment, gum restraining ring 104 is not slipped over first keeper 102 to circumscribe it as discussed above and ring 104 and first keeper 102 are not joined as discussed above. Gum restraining ring 104 is first inserted into the oral cavity around the area where an impression is to be taken to keep the gum borders separated. This prevents obstruction of the area and allows for easy subsequent insertion of male member 102B of first keeper element 102 into implant cavity 108B.

[0080] In FIG. 6, first keeper 102 encompassed by gum restraining element 104 is positioned in cavity 108B of implant 108.

[0081] FIG. 6 also shows hollow magnetic field providing element 106 containing a ring-shaped magnet 106A. The ring-shaped magnet 106A is positioned adjacent to the magnetic field providing element's hollow through-cavity 106B and attached thereto in any of many ways known to persons skilled in the art. Magnet 106A exerts a force sufficient to hold first keeper element 102 to magnetic field providing element 106 with little relative motion between them. Flange 106C of hollow magnetic field providing element 106 mates with notch 102G (best seen in FIG. 13B) of first keeper 102. Often, the magnetic field providing element 106 has the shape of an annular cylinder, all or part of which is a magnet, and there is no need for a separate magnet such as magnet 106A.

[0082] FIGS. 14A and 14B are cross-sectional and perspective views, respectively, of magnetic field providing element 106 shaped as an annular cylinder having a magnet 106A positioned therein. The elements in these Figures are numbered as in FIG. 6. Flange 106C shown in a cross-sectional view in FIG. 14A is best seen in the perspective view of FIG. 14B. Magnetic field providing element 106 may be formed of resins such as epoxy resins; metals such as dental casting ferromagnetic alloys; composite materials; and elastic materials such as rubber. The use of suitable polymeric or composite materials to at least partially form magnetic field providing element 106 achieves better fixation of the magnetic field providing element within the impression material during the impression taking process. Whenever non-magnetic material is used to form magnetic field providing element 106, a magnet such as magnet 106A is positioned in the non-magnetic material. If magnetic field producing material is used to form magnetic field providing element 106, the entire ring or annular cylinder or other shape such as an elliptical cylinder serves as the magnet. [0083] In FIG. 7, to which reference is now made, magnetic field providing element 106 is positioned on first keeper 102, the latter encompassed by gum restraining element 104. Male member 102B of first keeper 102 is positioned in cavity 108B of implant 108 which is covered by gingiva 900. Impression tray 110 is filled with a polymeric impression material 120 and then pressed against magnetic field providing element 106 so that it becomes embedded in polymeric impression material 120. Gum restraining ring 104 is constructed so that it prevents the self-hardening resin of impression material 120 from flowing between magnetic field providing element 106 and first keeper 102. After embedding magnetic field providing element 106 in impression material 120, pressure is maintained on the magnetic field providing element 106 until the material cures and hardens. In order to stabilize first keeper 102 vis-a-vis implant 108 when impression material 120 is poured, a matable flange/slot combination is used (not shown) with a flange on first keeper 102 and a slot on implant 108 or vice versa.

[0084] The outer surface of magnetic field providing element 106 may be undercut so that it would be firmly fixed to impression material 120, such as a silicone impression material, and to the plaster impression material discussed below.

[0085] As seen in FIG. 8, to which reference is now made, the impression tray with the cured impression material 120 together with embedded magnetic field providing element 106 is then disengaged from first keeper element 102 and withdrawn from the mouth.

[0086] Referring now to FIG. 9, a second keeper element 130 is positioned over magnetic field providing element 106 embedded in the cured impression material 120 of impression tray 110. An analog element 140 having an analog cavity 142 is positioned on male member 134 of second keeper 130. Typically, the inner surface of analog cavity is threaded (not shown), the threads mating with threads 135 on male member 134. It should readily be understood that other methods known by persons skilled in the art for joining male member 134 of second keeper 130 to analog element 140 may also be used.

[0087] FIG. 10 shows the elongated projection 132 of second keeper element 130 positioned in through-cavity, i.e. through-channel, 106B of magnetic field providing element 106. The Figure also shows the plaster impression material 137 poured over analog element 140 and portions of second keeper element 130. The second keeper 130 is formed of a magnetic field responsive material such as stainless steel, so that second keeper elongated projection 132 is held securely to magnet 106A of magnetic field providing element 106 by magnetic and by mechanical forces. The second keeper 130 and magnetic field providing element 106 are held together so that there is little, if any, relative motion between them when the plaster material is poured. It should be noted that when the plaster is poured, large forces and moments are effectively applied on the analog element 140 which negatively impacts the stability of the remainder of the system.

[0088] In some embodiments, only parts of second keeper 130 may be formed of a magnetic field responsive material, e.g. stainless steel.

[0089] FIGS. 15A and 15B show side and perspective views, respectively, of second keeper element 130. The elements of these Figures are numbered as in FIGS. 9 and 10 previously discussed. Notch 136 shown in a cross-sectional view in FIGS. 9 and 10 is best seen in the perspective view of FIG. 15B.

[0090] FIGS. 16A-16E show other embodiments 132A - 132E of projection 132 of second keeper 130. Projection 132 and male member 134 are typically integrally formed with the body 133 of second keeper 130. Various shapes are shown for projection 132 including a partially threaded projection 132A. It is readily understood that the shape of a magnetic ring element hole or the through-hole of an annular cylinder cavity 106B may need to be modified accordingly if projections such as 132A- 132E are used.

[0091] FIG. 11, to which reference is now made, shows analog element 140 and portions of second keeper element 130 covered in plaster 137, now dried and set. Once the plaster has dried and set, magnetic field providing element 106, impression material 120 and impression tray 110 shown in FIG. 10 are removed. Second keeper 130 is then removed from analog element 140.

[0092] Reference is now made to FIG. 12 where analog element 140 in plaster 137 is shown. Second keeper element 130 has been removed. Analog element 140 in plaster 137 enables fabrication of a dental prosthesis to be fitted on implant 108 shown for example in Figs. 5 and 6. The first and the second keepers can be attached to the implant/analog by integrated tread or separated screw.

[0093] Impressions produced using the above described system and method provides a more precise copy of implant 108 positioned in its location in the oral cavity than prior art methods and systems. By using this reproduction of the implant, a dental prosthesis may be fabricated in a technician's laboratory with high precision. [0094] FIGFS. 17 and 18, to which reference is now made, represent another embodiment of a second keeper and another method for attaching the analog to the second keeper prior to pouring plaster. FIG. 17 is a cross-sectional exploded view of the embodiment, while FIG. 18 is a perspective exploded view.

[0095] In this embodiment, the method proceeds as from FIG. 4 through FIG. 8 described previously. At that stage (FIG. 8), magnetic field providing element 306, having a through-cavity 306B, i.e. through-channel, is embedded in cured polymeric impression material 120 in impression tray 110. A second keeper 330, herein also sometimes denoted as a truncated second keeper, having a small male member 334, is then attached to magnetic field providing element 306. Second keeper 330 has a cavity 335 throughout its entire length that is through its body 333 and through its male member 334, which is open at both its ends. The attachment of magnetic field providing element 306 to second keeper 330 is such that through-cavities 306B and 335 of both elements are in registration with each other. Magnetic field providing element 306 and second keeper 330 are placed so that flange 307 of magnetic field providing element 306 mates with notch 336 of keeper 330. Additionally, because keeper 330 is formed of a magnetic field responsive material, such as stainless steel, and magnetic field providing element 306 contains a magnet (or is itself a magnet), magnetic forces, (and mechanical forces as discussed in the paragraph immediately below) hold second keeper 330 and magnetic field providing element 306 together. According to this embodiment, the first and the second keepers also can be attached to the implant/analog by integrated tread or separated screw.

[0096] Male member 334 of second keeper 330 is inserted into the through-cavity 342 of analog element 340. The through-cavity 342 of analog 340 is positioned to be in registration with the cavity 335 of second keeper 330. Finally, screw 313 with threads 315 is placed into the through-cavity 342 of analog 340 and brought into and through the thro ugh -cavity 335 of second keeper 330 into the through-cavity 306B of annular magnetic field providing element 306. The threads 315 of screw 313 in FIGS. 17 and 18 mate with threads 309 positioned on the inner surface of through-cavity of magnetic field providing element 306 and the surface of through-cavity 335. This holds all four elements together with little relative movement between them and plaster can then be poured over analog 340 while leaving a small access hole for the removal of screw 313. [0097] Screw 313 is functionally equivalent to elongated projection 132 of second keeper 130 in FIG. 10. It should be noted that analog 340 has a flat lateral face that appears clearly in FIG. 18. This flat face prevents undesirable rotation when screw 313 is inserted.

[0098] Additionally, second keeper 330 and analog element 340 are stabilized by a matable flange/slot combination with the flange on the second keeper 330 and the slot in the analog 340 or vice versa. This flange/slot combination is not shown.

[0099] After the plaster cures, the screw is removed and then the impression tray 110 and polymeric impression material 120 are removed together with magnetic field providing element 306 and second keeper 330. Only analog element 340 remains in the plaster to form the reproduction required by a technician to fabricate the prosthesis to be used with the implant.

[0100] FIG. 19 is a variant of the embodiment in FIGS. 17-18 where magnetic field providing element 306 is attached to screw 313 by mechanical forces. These forces are a result of the top smooth portion of screw 313 being positioned in the through-channel of magnetic field providing element 306. Since screw 313 is formed of a magnetic field responsive material such as stainless steel, it is also held by magnetic forces to magnetic field providing element 306. Threads 318 of screw 313 are matable with threads 341 in analog 340 (best seen in FIG. 17) and threads (not shown) in second keeper 330. As in the previous embodiment (FIGS. 17-18), screw 313 is functionally equivalent to projection 132 of second keeper 130 in FIG. 10.

[0101] FIGS. 20A and 20B, to which reference is now made, represent a variant of the embodiments discussed in conjunction with FIGS. 17-19. In this variant, the first and second keepers 430 are identical. They are constructed very much like the truncated second keeper 330 in the embodiment shown in FIGS. 17-19 and includes male member 434. Keeper 430 (and keeper 330) is formed as a unitary element of a magnetic field responsive material and has a cavity through its length that is a through-channel, the cavity being opened at both ends. FIG. 20A is a perspective exploded view of keeper 430 being used as a first keeper in this embodiment, while FIG. 20B is a perspective exploded view of keeper 430 being used as a second keeper in this embodiment.

[0102] In the embodiment of Figs. 20A and 20B, the gum restraining ring 104 discussed with the first embodiment may be slid onto keeper element 430 as in FIG. 4 and screw 413 in FIG. 20A and screw 414 in FIG. 20B attaches keeper element 430 to implant 408 in FIG. 20A and analog 440 in FIG. 20B. Threads 417 of screws 413 and 414 mate with threads in keeper 430 and implant 408 and analog 440 respectively (the threads of these latter three elements are not shown).

[0103] In FIG. 20A, magnetic field providing element 406 is attachable to keeper 430 as in prior embodiments by a magnetic force and by flange 407 of magnetic field providing element406 mating with notch 436 on keeper 430. When keeper 430 is joined to implant 408, head 418 of screw 413 lies essentially flush with the second (upper U) surface of keeper430. After joining keeper430 to implant 408, and attaching magnetic field providing element 406 to keeper 430, as in FIG. 7, polymeric impression material 120 is pressed onto magnetic field providing element 406.

[0104] Implant 408 as discussed above in the first embodiment has a cavity and is positioned in a patient's jaw. As in the first embodiment, when the polymeric impression material is cured, it is removed from the mouth of the patient with magnetic field providing element 406 still embedded in it (FIG. 8).

[0105] When screw 413 extends through keeper 430 and into implant 408 and when head 418 of screw 413 lies flush on the second surface (U) of keeper 430, an essentially unified connected structure from keeper 430 through implant 408 is formed, similar to the one formed in the embodiment of FIGS. 17-19. As noted above, magnetic field providing element 406 is also attached to keeper 430 by the magnetic force provided by the ring-shaped (or other shaped) magnet (not shown) in magnetic field providing element 406 (or by magnetic field providing element 406 itself if the element itself is a magnet) and the mating of flange 407 on magnetic field providing element406 with notch 436 on keeper 430.

[0106] Later, as shown in FIG. 20B, keeper element 430 is attached to analog element 440 with screw 414, the latter being longer than screw 413 and having a larger head 419 than the head 418 of screw 413. Head 419 of screw 414 effectively functions as elongated projection 132, shown for example in FIG. 9 of the first embodiment of the invention. At least head 419, if not entire screw 414, is formed of a magnetic field responsive material. Head 419 is sized and configured to be inserted into the through-cavity (through-channel) of magnetic field providing element 406, where it is held by the magnetic force provided by the magnet. The remaining stages (FIGS. 10-12) of the method are the same as in the original embodiment. When keeper430 acts as a second keeper, threads 417 of screw 414 mate with threads in keeper 430 and analog element 440, the threads of these latter elements not shown. [0107] It should be noted that when keeper430 functions in this last embodiment as the first keeper, that is as element 102 in for example FIG. 4 of the first embodiment, element 434 and screw 413 function as the male member.

[0108] As noted above, screw 413 of FIG. 20A is shorter than screw 414 of FIG. 20B, the latter used when keeper 430 functions essentially as second keeper 130 of the first embodiment functions. Screw 414 when inserted into keeper 430 functioning as the second keeper 130, has a larger head 419 than screw 413 and extends into magnetic field providing element 406 and its ring-shaped magnet (not shown) thereby increasing the stability and decreasing relative motion of analog 440 and second keeper 430 when plaster is poured and cured during the impression taking process.

[0109] It should readily be understood that both at the stage where keeper 430 is used as a first keeper (FIG. 20A), the through-cavity in keeper 430 and the cavity in implant 408, are aligned to be in registration with each other so that screw 413 passes through the through-cavity of keeper 430 into the cavity of implant 408. Similarly, when keeper 430 is used as a second keeper (FIG. 20B), the through-cavities of keeper 430 and analog element 440 are in registration with each other. When screw 414 extends through keeper 430 and analog element 440 and when head 419 of screw 414 extends into and through the ring-shaped magnetic element (not shown) of magnetic field providing element 406, an essentially unified connected structure from magnetic field providing element 406 to analog 440 is formed, similar to the one formed in the embodiment of FIGS. 17-19. Screws 413 and 414 in FIGS. 20A and 20B respectively together with element 434 function as the male member and elongated projection of the first and second keepers respectively. In FIG. 20B, where keeper430 functions as the second keeper, screw head 419 of screw 414 functions as the elongated projection of the second keeper.

[0110] In other embodiments of the system, the magnetic field providing element 406 may include an attachment means for attaching to the elongated projection of the second keeper. The attachment means may include, but is not necessarily limited to, screw threads, clips or any other mechanical attachment means facilitating good fixation of the second keeper to the magnetic field providing element thereby providing better stability of the system. [0111] Although the above embodiments of the method are described using first and second keeper elements 102 and 130 (or 330 or 430), respectively, which form the male members of the attachment system and a magnetic field providing element 106 (or 306 or 406) which forms the female member of the system, it should readily be understood that the above system may be constructed so that the keepers are configured to form the female members of the system while the magnetic field providing element may be configured and constructed to form the male member of the system.

[0112] Further, there are various possible combinations of the female member of the system, magnetic field providing element 106, and the male member of the system, the first and second keepers 102 and 130 (or 330 or 430), respectively, such as magnetic field responsive material- magnet; magnet-magnetic field responsive material; and magnet-magnet. All of these combinations may be applied in the system and method for taking impressions for fabricating prosthetics and crowns for implants, definition of central occlusion, use for mounting a surgical stent, the use of intraoral and extra-oral scanner.

[0113] As explained above, according to the method for taking an impression of the present invention, the process is simplified compared with existing conventional methods for taking an impression. Movement between the magnetic field providing element and keepers has been much reduced because of the positioning of the magnetic field providing element and insertion of a keeper projection therein. Interference by the gingiva during impression taking has also been very much reduced because of the gum restraining ring. Accordingly, better, more precise, prosthetics for implants result.

[0114] It should be noted that the first keeper, its body and its male member, a magnetic field providing element and a gum restraining element are herein at times denoted as a first keeper assembly. Similarly, the second keeper, its body male member and elongated projection, an analog element and a magnetic field providing element are herein denoted at times as a second keeper assembly. The magnetic field providing element is the same in both assemblies.

[0115] While element 104 and the like have generally been described as a gum restraining ring it should readily be understood that the element may have other shape such as elliptical or oval. Accordingly, the use of "gum restraining ring" is to be considered the equivalent and encompassing the more general term "gum restraining element". [0116] Also, it is obvious that the present invention is not limited to the above-mentioned embodiments, and variations and modifications may be made without departing from the scope of the present invention. It will be appreciated by persons skilled in the art that the present invention is not limited by the drawings and description hereinabove presented. Rather, the invention is defined solely by the claims that follow.