DENTAL BRIDGE

Abstract: The invention relates to a method and a means for preparation of a dental bridge for a dental prosthesis. The dental bridge is modelled by casting in a mould prepared from a casting model. The casting model is built up in the mouth of the patient by modules (3,6) which are joined together into a unit. A module consists of a metal socket (3) on which a cap (6) with a through hole is mounted. The modules are connected to each other preferably by gluing.

Description: Field of the invention: The present invention is related to a method and a means to prepare a dental bridge by casting in a mould, which is prepared from a casting model. Background of the invention: Implant is used as anchoring means for fixing dental prosthesis when other fixing possibilities are lacking. To build up a dental prosthesis with this type of anchorage is thus initiated by an insertion by an operation of bone-fixtures in the jaw by making an incision in the gums and drilling bores in the jaw-bone, into which bores bone-fixtures in the form of roote screws with a threaded, internal hole are screwed. A cover screw is placed in the internal hole of the roote screw whereupon the gums are replaced. After a period of four to six months the implant has been osseointegrated with the jaw-bone and the cover screw is again uncovered and replaced by a spacing element, a pillar. The pillar is healed in under protection of a healing cap. After completed healing the healing cap is removed and sockets are placed on the pillars and attached to said pillars with internal screws. After sealing of the open ends of the sockets, an impression of the jaw is made by depressing an impression tray filled with impression material on the jaw and the material is allowed to solidify. The upper ends of the sockets are uncovered from impression material and the internal screw is released. The solidified impression including the cast in sockets can now be removed and forwarded to a dental technician. The dental technician builds up a positive working model of the jaw by, as a first step attach pillar dummies into the sockets which are cast in to the model and as a second step make an impression. The screws are released and the positive working model of the jaw in which pillar dummies are cast in can now be used to build up a dental bridge structure. On the pillar dummies, sockets are attached by screws and a continuous bridge structure, a wax model, is modelled of wax or plastic material. The wax model or the casting model must now be forwarded back to the dentist and tested on the patient to check that the matching to the anchoring elements is exact. When the casting model is back with the dental technician, said model is used for preparation of a mould. This is prepared by pressing the model into a mould compound and burning the wax or plastic material out in a burning oven. A metal framework is cast in the completed mould to form a dental bridge into which the sockets are cast. The method described above is complicated and suffers from certain disadvantages. Solely to build up the mould, two separate appointments with the dentist and in between work by the dental technician are needed. It has also been experienced that the completed casting model, when tested on the patient, often match inexact, which causes further treatments and subsequent adjustments. One disadvantage in this method is also the impression inside the mouth which is extremely unpleasant for the patient. Summary of the invention: The object of the present invention is to simplify the preparation of a dental bridge as described by way of introduction and the method according to the invention is characterized in that the casting model is built up in the mouth of the patient by modules which are joined together. The means for carrying out the above method is characterized by a module which comprises a prefabricated cap with a through hole. Further advantageous features of the invention will become apparent from the following description of one embodiment of the invention and from the dependent claims. According to the invention the advantage of a simplified preparation method of the casting model is obtained, which model is modelled during one single appointment with the dentist and without contribution of a dental technician. The risk for a defective fit in the workmanship is completely eliminated by this method. A further advantage is lack of impressions in the mouth which are unpleasant for the patient. Brief description of the drawings: The invention is described in detail with reference to the accompanying drawings, where Figure 1 shows a longitudinal section through a section of the jaw during modelling of the casting model, and Figure 2 shows from above a section of the jaw with joined modules according to Figure 1. Detailed description of a preferred embodiment of the invention: In Figure 1 a number of roote elements 1 are shown, which are screwed and osseointegrated in the jaw-bone. In each of the internal holes of the roote screws 1 a pillar 2 is screwed in, said roote screw 1 and said pillar 2 together form anchoring elements for the bridge structure. On the conical upper end of the pillar 2, a metal socket 3 is fitted and attached to the pillar with an internal screw 4. A prefabricated cap 6 is arranged and affixed on the socket 3, said cap having a through hole 5 with a shape and a size corresponding to the metal socket 3. The cap 6 is preferably made of burnable plastic material. The external shape of the cap 6 is somewhat rounded (see Figure 2) with two diametrically opposed and flat wallsections. The flat wallsections of the adjacent caps are arranged parallel with each other to form a gap 7 of suitably uniform thickness between the flat wallsections. The gap 7 is filled up with burnable glue. The modules are thus joined together by these glue joints 7 to form a continuous unit. The method for preparation of a dental bridge according to the invention is as follows: When the anchoring elements, each comprising a roote screw 1 and a pillar 2, have been osseointegrated with the jaw-bone and healed in, the healing cap is removed as described above. The prefabricated cap 6, preferably made of plastic material which can be burnt out, is mounted around the socket 3 and the two units 6, 3 are affixed to each other with burnable glue. The socket 3 with the cap 6 is placed and fitted on the conical surface of the pillar 2 in the mouth of the patient and is attached to the pillar 2 with the internal screw 4. In the same way another cap 6 is mounted around the following socket 3 and the unit is placed on the adjacent pillar 2. Before the socket 3 is fastened with a screw in its position, the cap 6 is trimmed for the purpose of achieving a suitable space between the adjacent caps to form a gap 7 for the glue. The trimming comprises either grinding of the flat surface or building up the surface by application of burnable plastic material, depending on the distance between the anchoring elements in the jaw-bone. After the trimming the socket 3 is thus fastened with a screw and the following socket with cap is subjected to the same procedure. When all the pillars have been provided with a socket 3 and a cap 6 in the described way, the whole system is jointed together by application of burnable glue in each gap 7. The modelling of the casting model has so far been made by the dentist (dental prosthetist) in the mouth of the patient during one single appointment. As the model is built up on the actual anchoring elements in the mouth of the patient instead of on pillar dummies which are cast in a positive model of the jaw, the risk of defective fitting and subsequent adjustments is eliminated. The internal screws of the sockets can now be released and the casting model can be lifted out and forwarded to the dental technician. The dental technician provides the model with retention means and forms the mould in a customary way by pressing the casting model into a mould compound and burning the plastic material out whereby the dental bridge is cast. Possible modifications of the invention: The invention is in no way limited to the embodiment described above and several possible modifications of the invention are possible within the scope of the claims. The internal and external shape of the caps can vary, as far as the internal through hole has got a shape which corresponds to the external shape of the socket, which shape can differ from the cylindrical shape which is shown in the figures. To facilitate and minimize the trimming, the plastic cap can be manufactured and obtainable in several different sizes. In this way the dentist can choose a size of the cap which will fit the distance between the anchoring elements in the jaw-bone. Instead of trimming adjustments, different gauge blocks made of burnable plastic material can be affixed between the caps.

Claims: Method for preparation of a dental bridge by casting in a mould prepared of a casting model, characterized in that the casting model is built up in the mouth of the patient by modules (3,6) which are joined together. Method according to claim 1, characterized in that a module (3,6) is formed by a cap (6) with a through hole which is mounted on a metal socket (3), which is intended to be cast into said dental bridge. Method according to claim 2, characterized in that said sockets (3) are attached to anchoring elements (1,2) in the jaw of the patient. Method according to claim 3, characterized in that the caps (6) are jointed together into a continuous unit by gluing, preferably by burnable glue. Method according to claim 2, characterized in that the opposing surfaces of the adjacent caps (6) are trimmed to form a suitable gap (7) for glue between the surfaces when the sockets (3) are mounted on the anchoring elements (1,2) in the jaw of the patient. Method according to claim 5, characterized in that the caps (6) are trimmed by grinding off or by application of material, depending on the distance between the caps (6) when mounted. Means for carrying out the method according to claim 1, characterized in that the means consists of a module, which comprises a cap (6) with a through hole (5). Means according to claim 7, characterized in that the cap (6) is made of burnable plastic material. Means according to claim 8, characterized in that the module comprises a metal socket (3) which is enclosed by the cap (6) and is formed to be attached to anchoring elements (1,2) in the jaw of the patient. Means according to claim 9, characterized in that the caps (6) have different external dimensions in the longitudinal direction of the jaw-bone to provide a possibility of a choise between different caps depending on the distance between the anchoring elements (1,2).

Inventors: SOEDERBERG, PER OLOF, Söderberg, Per Olof
Applicants: ASTRA MEDITEC AB
Application year: 1988
Main classification: A61C8
IPC codes: A61C13, A61C8