A SOCKET FOR CARRYING A DENTAL PROSTHESIS

Abstract: A socket for carrying a dental prosthesis is described, which socket (1, 11) comprises a supporting part (2, 12) which at one end thereof is provided with a supporting surface (3, 13) for bearing against a supporting surface (21) on a spacing element (17) attached to the jaw-bone (19) of a patient, and which further has means (4, 14) for securing of the socket against the spacing element. The socket is characterized in that the opposite end of the supporting part (2, 12) beyond the means for securing the socket is provided with a tubular thinwalled extension (6, 15), which may form a channel through an impression material and/or a prosthetic material. The socket may serve as an aid in the prosthesis preparation work and as a part of the finished prosthesis.

Description: Technical field The present invention is related to a socket for carrying a dental prosthesis, in particular a dental prosthesis which is fixed to one or more implants attached into the jaw-bone of a patient. The object of the invention is to achieve a socket which may make part of a finished prosthesis and which additionally can be used as an aid during one or more steps in the work of preparing such a prosthesis. A further object is to reduce the number of parts making up a dental implant system. State of the art From WO 85/02337 is known an implant for fixing of dental prostheses which has a conical socket-shaped part (7) against which the dental prosthesis may be mixed. Said socket-shaped part may however not, in the embodiment shown, be used as an aid in the work of preparing a prosthesis. From Adell et al., Int. J. Oral Surg. 10 (1981), page 388 is known a dental implant system wherein the device for fixing of a prosthesis is a gold cylinder (k). Neither this cylinder may be used in the work of preparing a prosthesis. Instead there is used thereby separate impression copings (g and h) , which in a first step are attached to spacing elements (c and d) attached to an implant, whereupon they are cast into a negative impression model , whereupon casting dummies for the spacing means are attached to said impression copings and cast into plaster. After removal of the impression copings the gold cylinders may be attached to the casting dummies, and a prosthesis is built thereon. This implant system has as a substantial disadvantage the fact that different details are required in the work of preparing the prosthesis and in the finished prosthesis, which in addition to the increased cost implies a practical drawback. A further component in the form of an extended screw may also be required in taking the negative impression model. Further, the impression copings have a fixed length and cannot be adjusted upon need of a varying length, e.g. conditioned by the space in the oral cavity. Swedish patent No 8504274.5, Fig 1, discloses a connecting device for a prosthesis which includes a "patrix" 11 which is held on an anchorage fixture by means of a spacer 1 and which is urged into contact with an O-ring 9 by a nut 7. The nut is scremed on to attain a light compression of the O-ring. Grooves are provided in the upper patrix edge so that the tension may be exactly determined. The nut is screwed on to a matrix 6 held by an attachment screw 4. It is evident from Fig 1 of the citation that the top of the patrix 11 is only slightly above the matrix 6 and the attachment 4. It is apparent that the intent in the citation is that the slot in the nut 7 should be comparatively close to the top of the patrix, adjacent to the alignment groove, in order to be able to "exactly" set the desired tension on the O-ring (cf also the enclosed copy of the concurrent US Patent 4,746,293 by the same inventors, cited during the examination of the US application corresponding to the present EP application). The location of these grooves on the edge of the patrix makes it impossible to grind down the edge in the way suggested in the present invention since this prior art device is dependent thereon. The basic problem to be solved by the devices disclosed in SE-B-8504274.5 and US-A-4,756,698 is to provide a tooth implant having elastic properties similar to the elastic properties of natural teeth. This problem has nothing whatsoever in common with the problem underlying the present invention and it would therefore not be any reason for the man skilled in the art to study these documents when trying to solve the kind of problems underlying the present application. The Jemt article, from the February 1986 issue of the Journal of Prosthetic Dentistry, describes a procedure for a single tooth replacement using a smooth titanium cylinder. Unlike the present invention, these cylinders are not used in an implant system using a spacer element, which is normally intended to support a bridge element, but rather is a protocol for a short span restoration in which the cylinder is mounted directly on the implant, and where the lower part of the acrylic resin material (forming the artificial tooth) lies below the gum line. As shown in Fig 1, cylinders are provided having different size collars,and an extension portion above the collar. The annular collar on the cylinder forms the lower base for the acrylic material. A cylinder containing an appropriate size collar is selected for each individual application such that, when the cylinder is mounted on the implant, the top of the collar is positioned 1 mm below the soft tissue margin. An impression is formed using an impression tray and a guide pin, and thereafter a master is cast. Then, as set forth on page 246, "the retentive part of the abutment is shortened in relation to the available vertical space". Thereafter, a resin crown is processed onto the titanium abutment. As discussed above, Jemt suggests providing cylinders with varying shoulder heigths. While this results in cylinders of differing lengths, this is for the purpose of varying the available heigth below the shoulder, to accommodate different thicknesses of soft tissue below the gum line. The height of the portion above the shoulder appears to be the same in the various cylinders. In view of the difference of protocols for which the Jemt cylinder is intended, namely in the context of curing acrylic directly to the abutment and using a guide pin in the impression taking, it is submitted that Jemt does not suggest a modification of the cylinders of the type to which the present application applies. The teachings of this article thus would not lead the man skilled in the art to the present invention, either singly or in combination with the other cited state of the art. Description of the invention According to the present invention the disadvantages with previously known constructions are avoided. Thus, it is provided a socket for carrying a dental prosthesis, which socket comprises a supporting part which at one end thereof is provided with a first supporting surface for bearing against a complementary supporting surface on a spacing element or pillar attached to the jaw-bone of a patient, and which further has means for securing of the socket against the spacing element. The socket is characterized in that the opposite end of the supporting part, beyond the means for securing the socket,is provided with a tubular thinwalled extension, which may form a channel through an impression material and/or a prosthetic material. Preferably the bearing surfaces of the socket and the spacing element are complementary conical surfaces around which may be arranged planar control surfaces, however, also planar or differently shaped bearing surfaces may be used. The means for securing the socket against the spacing element may consist of a joint known per se , e.g. a screw joint. According to an embodiment of the invention this means comprises an inner conical supporting surface shaped for bearing against the conical head of a screw by which the socket is attached to the pillar Alternatively, the supporting surface and the screw head may be planar The spacing element may preferably consist of a single element, which in a manner known per se is attached to the jaw-bone via an osseointegrated root element anchored therein. The tubular extension of the socket is thinwalled according to the invention. Thereby is achieved the possibility of grinding the socket down into level with the upper edge of the prosthesis or prosthetic part after building of a prosthesis or a part thereof, such as a dental bridge. In a corresponding manner the socket may be adjusted as to length on taking impressions or in process preparative work. According to a preferred embodiment of the invention the supporting part of the socket has in the outer surface thereof one or more annular grooves for facilitating the casting or glueing of the socket into the prosthetic part. The socket according to the invention is made of metal such as stainless steel, preferably made of titanium or a titanium alloy. It has been found to be possible to cast a titanium socket according to the invention into a dental bridge of gold alloy. The invention is described further with reference to the appended drawings, where Fig. 1 shows a length section through a socket according to one embodiment of the invention, Fig. 2 shows the socket in fig. 1 in a view at an angle from above, Fig. 3 shows a length section through a socket according to another embodiment of the invention, Fig. 4 shows an implant combination comprising a socket according to the invention on building of an impression model , and Fig. 5 shows an implant combination comprising a socket according to the invention in a finished prosthesis. In figs. 1 , 2, 4 and 5 is denoted with 1 a socket according to the invention. The socket has a carrying part 2 which at its lower end has an inner conical supporting surface 3 broadening towards the end, for bearing against a complementary supporting surface on a spacing element. The supporting part of the socket further has an inner conical bearing surface 4 widening towards the upper end of the socket, for bearing against the conical head of a screw. The cavities defined by the bearing surfaces are in connection with each other via a short cylindrical bore 5. A tubular thinwalled extension 6 of the socket, made in one piece with the socket, is arranged at the upper end of the supporting part 2. The extension 6 has a length exceeding the length of the supporting part. As apparent from the drawing the wall thickness of the thinwalled extension 6 is substantially less than the wall thickness of the supporting part 2 Two annular grooves 7 and 8 are arranged around the supporting part. Between these grooves notches 9 are arranged for securing the socket against rotation in the impression and/or prosthetic material. The lower end of the socket has a planar control surface 10 adjacent to the conical supporting surface 3. In fig 3 the socket is denoted 11 , the bearing part 12, the lower conical supporting surface of the bearing part, which supporting surface has a larger cone angle than the supporting surface 3 in fig. 1, is denoted 13 and is shaped for bearing against a spacing element with the corresponding conicity. The upper conical bearing surface of the supporting part, which surface is to bear against a screw, is denoted 14, and a tubular extension is denoted 15. The supporting part has an annular groove 16. In figs. 4 and 5 17 denotes a pillar, which is a spacing element, which via an osseointegrated roote screw is attached to the jaw-bone 19 of a patient. The tissue covering the jaw-bone is denoted 20. The pillar has an outer conical supporting surface 21 Between the lower end surface of the socket and a shoulder on the pillar there is a narrow gap 22. A screw for assembling the socket and the pillar is denoted 23 and has a conical head 24 which bears against the bearing surface 4. An impression or casting material used during the prosthesis preparing work is denoted 25, while a gold alloy dental bridge making part of a prosthesis, in which bridge the titanium socket is cast, is denoted 26. After casting of the socket into the bridge the extension 6 of the socket is ground down at 27 in level with the upper surface of the dental bridge 26. The dental bridge is baked into a prosthetic material 28 of acrylic resin, in which false teeth 29 are attached. A manner of operation on using the socket according to the invention is in essence as follows. Bores for root screws 18 are drilled into the jaw-bone 19 The root screws are screwed in and are allowed to osseointegrate in a known manner. After uncovering of the upper ends of the root screws, pillars 17 are screwed in, which pillars usually are allowed to heal in under cover of a healing cap attached over the conical supporting surface 21 thereof. The healing cap is removed and sockets 1 are placed on the pillars and attached with screws 23. If desired, a plastic impression material may be placed over the socket for a bite recording to be used by the dental technician in the final prosthesis preparation. When needed the sockets are taken out and adjusted as to length in a first step by grinding down, whereupon they are remounted. The ends of the sockets are sealed with a plastic compound, whereupon an impression tray filled with plaster is depressed over the sockets, whereby the plaster is depressed as far as shown in fig. 4 or preferably all the way down to the tissue 20, and the plaster is allowed to solidify. The seal over the ends of the sockets is removed, the screws 23 are released and the plaster impression is removed. Pillar dummies with conical supporting surfaces identical to the supporting surfaces 21 of the pillars are attached in the sockets by the screws 23 and are cast into plaster. The first plaster impression is removed and broken down to uncovering of the sockets 1, alternatively new similar sockets 1 are taken, and the sockets are mounted on the pillar dummies A bridge construction is modelled of wax or plastic material and is released by releasing the screws 23, whereupon the notches 9 of the socket prevent the rotation thereof in the plastic or wax frame-work. A mould is prepared by depressing the bridge structure into a mould compound and burning out of the wax or plastic material . A dental bridge 26 is cast of a metal alloy onto the sockets whereupon projecting parts of the sockets are ground down to the extent required and prosthesis building is done in a manner known per se .

Claims: A socket for carrying a dental prosthesis including a dental bridge, which socket comprises a supporting part (2, 12) which at one end thereof is provided with a first supporting surface (3, 13) for bearing against a complementary supporting surface (21) on a spacing element (17) attached to the jaw-bone (19) of a patient, and which further has means (4, 14) for securing of the socket against the spacing element, characterized in that the opposite part of the supporting (2, 12), beyond the means for securing the socket, is provided with a tubular thinwalled extension (6, 15) which will form a channel through an impression material and/or said dental bridge, any parts of the extension (6, 15) projecting from said dental bridge being ground down to the extent required. A socket according to claim 1, characterized in that the supporting part on the outer surface thereof has one or more annular grooves (7, 8, 16) for faciliting the casting or glueing of the socket into the prosthetic part.

Inventors: SOEDERBERG, PER OLOF, Söderberg, Per Olof
Applicants: ASTRA MEDITEC AB
Application year: 1988
Main classification: A61C8
IPC codes: A61C8