WO2009068560A1

WO2009068560A1 - A method and a device for arranging a dental bridge to dental implants

Info

Publication number: WO2009068560A1
Application number: PCT/EP2008/066229
Authority: WO
Inventors: Lennart Olsson; Anders Lindberg; Olof Bange
Original assignee: Lindberg Implants Ab
Priority date: 2007-11-26
Filing date: 2008-11-26
Publication date: 2009-06-04
Also published as: SE0702660L

Abstract

A method for arrangement of a dental bridge (10) with at least one bridge support (11) being adapted to be fastened to at least one dental implant arranged into a jaw comprises the steps of fastening an impression element to each of said implant, providing an impression of the jaw with said impression element(s) into a rubber like material in an impression tray for forming a jaw model (50), and fastening a replica (30) to each impression element. Furthermore, the method uses each replica as an electrode for adjusting a contact surface of the at least one bridge support (11) to the shape and position of the at least one replica representing the corresponding implant. A device for machining at least one bridge support (11) of a dental bridge for adjustment to at least one dental implant has at least one electrode which is a replica (30) of said implant.

Description

A METHOD AND A DEVICE FOR ARRANGING A DENTAL BRIDGE TO DENTAL IMPLANTS

TECHNICAL FIELD

The present invention relates to a method for arranging a dental bridge having at least one bridge support being adapted for connection to at least one dental implant anchored in the jaw of the oral cavity of a human being. In addition, the invention relates to a device for machining at least one bridge support of a dental bridge for adjustment to fit to at least one dental implant arranged in the jaw of the oral cavity of a human being.

BACKGROUND ART

Implants for anchoring single or several artificial teeth forming dental bridges or implant bridges exist since a couple of decades. Currently, there are more than two thousands different implants available on the market. Before temporarily or permanently anchoring artificial teeth or dental bridges on implants, these must be arranged into the jaw of the oral cavity and be accepted by the bone tissue. After the arrangement of the implants into the bone tissue, either the edges of the mucous membrane are stitched together or healing abutments are temporarily arranged to each implant, in such way that a portion of the healing abutment protrudes above the gingiva. The healing abutments prevent soft tissue and bone tissue to grow into the implants, forming the gingiva while the implants are healed up into the bone tissue. The implants are preferably left unloaded for a couple of months to ensure that they are fully healed up into the bone tissue, which is a prerequisite for the future arrangement of the dental bridge. In the case wherein the edges of the mucous membrane are stitched together a second surgery is required to uncover the implants, healing abutments are then temporarily arranged to the implants to cover those until the gingiva is healed up. A model of the jaw with the implants arranged therein has to be produced to be used at the manufacturing of the bridge construction. When the bone tissue and the gingiva are healed up, the healing abutments are temporarily removed. Impression cylinders are fastened to each implant by screws, and an impression of the cylinders is made into a rubber like material contained in an impression tray. The screws are then unscrewed from the implants, while the impression cylinders are embedded into the rubber like material in the impression tray. Immediately thereafter, the healing abutments once again are arranged to the implants for keeping the gingiva in form and for preventing it to grow into the implants. Replicas of the implants are then arranged to each impression cylinder, and a cast of e.g. stone plaster is poured into the impression tray for embedding the replicas. A model of the jaw is now produced, wherein each replica represents an implant. One way of manufacturing a bridge construction of a dental bridge is to cast it. In this case, the technician starts with waxing up the model of the dental bridge, investing it into embedding material, burning out the wax and casting melted metal into the space that earlier was filled with wax. The bridge construction has bridge supports, which are integrally cast with the bridge construction and which are used for fastening the bridge construction to the implants. A drawback with bridge constructions manufactured by casting is that the precision between each bridge support and corresponding implant is low, i.e. the bridge construction fits badly to the implants, and one reason for this is due to shrinkage and/or creeping after cooling. To enhance the precision between each bridge support and corresponding implant, the bridge supports are removed by cutting and are then replaced by turned bridge supports, which then are arranged to the bridge construction by laser welding and are positioned correctly by guidance of the replicas of the model. Another way of manufacturing a dental bridge is to mill it. In this case, the technician uses the model for making an original, e.g. of a plastic material, which is scanned and transformed to a CAM (Computer Aided

Manufactuhng)-file. The bridge construction is then milled according to the instructions from the CAM-file, and with the bridge supports integrally made. In either case, the dental bridge is made of a metal material, such as cobalt chrome, titanium, gold or zirconium, or alloys thereof. In some cases, the shape of the bite surface of the teeth can be prepared and formed as the anatomy of the row of artificial teeth minus a couple of mm, e.g. about 1 -2 mm, which will be added as layers of porcelain material. In other cases, the bite surface is formed by the layers of porcelain material applied on the metal material, shaped similarly to real teeth, for forming a part of or a full row of artificial teeth. In SE-C2- 503 073, a bridge construction is manufactured by using electrodes for forming cut-in portions corresponding to bridge supports, which are to be received in the cut-in portions and then fitted to replicas, i.e. the dental implants.

The bridge construction has usually at least two bridge supports protruding from the side opposite to the bite surface and being equal in numbers with the implants. The dental bridge will be anchored to the implants by screws arranged through the bridge supports, or are cemented to the implants. However, firstly each bridge support has to be adjusted to the corresponding implant, since the implants are not arranged in an even plane due to the anatomy of the jaw; they may protrude at slightly different distances from the gingiva of the jaw having different inclinations in relation to each other. For the adjustment the replicas of the model are used, which are reproductions of the implants. The positions of the replicas are read by means of a scanner, and the coordinates for each replica are stored in a profile cutter. After cutting off the bridge supports, these and the rests of the bridge construction are milled by the profile cutter according to stored data and are then reconnected to each other by laser welding. The under cuts are manually machined. The adjustment procedure is time-consumption. A problem is that it is difficult to reach a sufficient degree of precision between the implant and the bridge construction, i.e. the abutment between the contact surfaces of the bridge supports and the corresponding implants and the fitting between those contact surfaces and the shape of the implants are bad, which will result in that the implants become loose. SUMMARY OF THE INVENTION

An object of the present invention is to eliminate at least one of the drawbacks mentioned above. A further object of the invention is to provide a device for machining at least one bridge support of a dental bridge for adjustment to at least one replica corresponding to at least one dental implant arranged in the jaw of the oral cavity of a human being. According to one aspect of the invention a method is provided for machining at least one bridge support of a dental bridge for adjustment to at least one replica that represents at least one corresponding dental implant. This is done by using each replica as an electrode for adjusting a contact surface of the at least one bridge support to the shape and position of the replica representing the corresponding implant. According to another aspect of the invention, there is provided a method for the arrangement of a dental bridge having at least one bridge support being adapted to be fastened to at least one dental implant arranged into the jaw of the oral cavity of a human being. The method has the steps of fastening an impression element to each of said implant, providing an impression of the jaw with said impression element(s) into a rubber like material in an impression tray, fastening a replica to each impression element, and using each replica as an electrode for adjusting a contact surface of the at least one bridge support to the shape and position in relation to a reference level of the at least one implant. In the method the replica is used to remove material from said bridge support, wherein spark machining is used for the removal of material. The replica is at least partly made of a material suitable for spark machining, such as a copper alloy, graphite or carbon. According to a second embodiment of the method, the replica is used to deposit material on said bridge support, wherein electrochemical deposition is used for the addition of material. In both embodiments of the method, voltage is individually supplied to each replica to provide individual control of the machining of each bridge support. The voltage may be sequentially or simultaneously supplied to each replica, and each replica is galvanic insulated. The method may also be used to form a channel of the at least one bridge support of the bridge construction. A further electrode is then provided, which is moved in a vertical or circular motion depending on if a straight or a curved channel is required.

According to yet another aspect of the invention a device is provided for machining at least one bridge support of a dental bridge for adjustment to at least one replica that represents at least one corresponding dental implant. Each replica is arranged to be used as an electrode being adapted to adjust a contact surface of the at least one bridge support to the shape and position of the replica representing the corresponding implant. The device may have a further electrode for forming a channel of the at least one bridge support. The advantage of the present invention is that the manufacture of the bridge construction can be made in one step by adjusting each bridge support individually to the corresponding replica. This means that the manufacture is reduced from several steps as in the prior art to only one step. Another advantage is that the present invention also can adjust each bridge support simultaneously, i.e. each bridge support is adjusted at the same time as all the other bridge supports.

Further objects, features and advantages of the present invention will appear from the following detailed description, from the attached drawings as well as from the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to explain the invention, a number of embodiments of the invention will be described below with reference to the drawings, in which: Fig.1 shows a perspective view of a schematic bridge construction, Fig. 2 shows a perspective view of a schematic bridge construction from below,

Fig. 3 shows a schematic side view of a replica and a bridge support, Fig. 4 shows examples of different shapes of electrodes, Fig. 5 shows an illustration of the process of machining in vertical direction, Fig. 6 shows an enlarged view of the encircled area in Fig. 5, and Fig. 7 shows an illustration of the process of machining in a circular direction. Same reference numerals have been used to indicate the same parts in the figures to increase the readability of the description and for the sake of clarity. The figures are not made to scale, and the relative dimensions of the illustrated objects may be disproportional.

DETAILED DESCRIPTION

A prerequisite for anchoring dental bridges to implants is that each of the bridge supports of the bridge construction are exactly adapted to replicas representing the corresponding implants to avoid that undesired tensions appear. It is then necessary to exactly adjust the contact surface of each bridge support to the corresponding replica, i.e. implant, which involves the abutment of the contact surfaces of the bridge support to the shape of the replica and the implant and the position of each bridge support in relation to the corresponding replica and implant, defining the precision of the dental bridge to the replicas and ultimately the implants. According to the invention these adaptations and adjustments of the bridge supports of the dental bridge to the replicas, i.e. the implants, are done by either removal of material from the bridge supports or addition of material to the bridge supports, which are performed by means of spark machining or electrochemical deposition, respectively. In both processes the replicas of the implants are used as electrodes and as shape- and positioning indicators.

A model of the jaw, with the implants arranged therein at fixedly determined positions, is firstly made to get the positions of the implants. The position may be determined in three directions in relation to a reference level, which will be explained in further detail below. When the bone tissue and the gingiva are healed up after the surgery, the healing abutments are temporarily removed from the implants and impression elements, such as impression cylinders, are screwed onto each implant. An impression is made into a rubber like material and replicas are arranged to each impression element. Then a cast of e.g. stone plaster is poured into the impression tray for embedding the replicas. A model is now produced, in which each replica represents the corresponding implant. According to the invention, the model is used for manufacturing a bridge construction having bridge supports in one step, such that no additional subsequent machining is necessary for adjusting the fit of the bridge supports to the replicas and ultimately the implants. Fig. 1 shows an example of a bridge construction 10 having bridge supports 11. The bridge supports 11 have a first end 12 protruding from and opening at a first external side and have a second end opening at a second external side of the bridge construction 10. The bridge supports 11 are showed with curved channels 14, but could be provided with one or several straight channels 14. Fig. 2 illustrates the bridge construction 11 from below, showing a contact surface 20 that have to be adjusted to the shape and position of a corresponding replica and ultimately a implant for an accurate abutment. Fig. 3 shows an example of a replica 30 having active surfaces 31 and a bridge support 11 with a contact surface 20, which should be adapted and adjusted to the active surfaces 31 of the replica 30. The active surfaces 31 of each replica 30 are defined as the surfaces that are active during the precision process for adjusting the contact surface 20 of the bridge supports 11 to the shape and position of the implants. Fig. 4 shows examples of different shapes of the replicas 30, which also illustrates some examples of different types of implants, since a replica is an reproduction of a corresponding implant. As seen in the figure, the active surfaces 31 of the replicas 30 can have totally different shapes to correspond to a specific implant. Each replica 30 has two functions; it is acting as an electrode and as a positioning indicator, which will be described below in connection with the machining process. The replicas 30 can be pehscopic, i.e. extendable along a longitudinal axle, which is an advantage at machining when the mutual positions of the implants differ. Fig. 5 illustrates the process of machining in vertical direction, wherein the manufactured bridge construction 10, having a bridge support 11 , is fixedly arranged in a device at a reference level in a plane that is parallel with the horizontal plane 51 , and the model 50 with the replicas 30 is arranged movable and controllable in relation to the bridge construction 10. As seen, the replica 30 shown in the figure is arranged inclined in relation to the horizontal level 51 , illustrating that the corresponding implant is not vertically arranged into the jaw. The direction of movement is illustrated by the arrows A, B, perpendicular to the horizontal plane 51. Fig. 6 shows in enlarged scale the active surfaces 31 of the replica 30 is moved into a close position to the contact surface 20 of the bridge support 11 forming a small distance or gap 60 there between, for example about 0.10 mm. This gap 60 is necessary for the spark machining or the electrochemical deposition, since otherwise short circuit will appear. A power source is provided to supply voltage to each replica individually in one embodiment, and in another embodiment this is done simultaneously for all replicas. A programmable computer, having a memory, is connected to the device to control the relative movement between the model and the bridge construction, and to control the power supply to the replicas. The bridge construction is scanned, and the position of each bridge support in three directions and in relation to the reference level and in relation to the other bridge support(s) is stored in the computer. The voltage may be simultaneously supplied to each replica, but while individually controlling the power level, which requires that the replicas are isolated from each other. Alternatively, the voltage may be sequently supplied to each replica. By variation of the ampere of the current the surface quality can be controlled regarding smoother or rougher surfaces; a higher ampere level gives a smoother surface than a lower one. In the first embodiment, wherein material is removed from the bridge support, the electrodes, or replicas, are fully or partly made of a material suitable for spark machining, such as carbon, graphite or the like. The active surface of each replica has the same shape as the corresponding implant. At machining according to both embodiments, the dental bridge and the model are sunk down in a liquid suitable for the purpose, such as a dielectric, or a dielectric is sprayed over the surfaces that are active in the machining process. In the first case, material is removed by spark machining during voltage appliance to the replica, the outer surface of the bridge support being eroded in controlled way to fit exactly to the implant. In the second case, material is added by electrochemical deposition during voltage appliance to the replica, the outer surface of the bridge support being coated with a thin layer of material in controlled way resulting in that the shape of the final surface will fit exactly to the implant.

The process of spark machining may also be used to form the channels of the bridge supports of the dental bridge, either when straight channels are required or curved ones. By scanning the bridge construction, the position of each bridge support in three directions and in relation to the reference level and in relation to the other bridge support(s) is stored in the computer, and those positions are transformed by the computer to present the position and shape of the channel of each bridge support. When a straight channel is required, a further electrode 70 is moving vertically, and when a curved channel is required the further electrode 70 is moving in a circular motion having the centre in same plane as the reference level of the dental bridge. Fig 7 illustrates a circular movement of the further electrode 70 in the directions according to the arrows C, D, wherein the further electrode 70 is moving an angle "α" in relation to a plane 71 that is perpendicular to the reference level 72 of the bridge construction and the centre of the movement is congruent with the reference level 72. The active surface 73 of the electrode 70 forms the shape of the surface 74, against which the screw head of a screw abuts when the screw is mounted into the channel to be fasten to the corresponding implant anchored into the jaw. Thus, the method offers to provide the surface 74 with an accurate position and inclination in relation to the corresponding implant, which increases the precision between the dental bridge and the implants. Alternatively, pre- machined channels 14 may be provided before arrangement of the bridge construction 10 into the device for adjustment using spark machining or electrochemical deposition.

It should be noted that all movements, or relative movements, of the electrodes for forming channels and replicas forming the shapes of bridge supports are performed in relation to the bridge construction, which defines the reference level. Also, every bridge support is individually adapted to the corresponding replica and thereby to the corresponding implant. An advantage is that no mechanical contact is present at electrochemical deposition or spark machining, which otherwise may cause forces or vibrations that will negatively affect the precision between the implant and the dental bridge. Another advantage is that no under cuts are generated. The replicas are active components during the manufacture of the dental bridge, as being both reproductions of the corresponding implants and as being involved during the method for arranging the dental bridge to the implants with a high precision, which includes the adjusting and adaptation of the contact surface of each bridge support to each corresponding implant. The most important advantage is that the bridge construction is manufactured in one step by adjusting all the bridge supports individually at once. In the claims, the term "comprises/comprising" does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented. Additionally, although individual features may be included in different embodiments, these may possibly be combined in other ways, and the inclusion in different embodiments does not imply that a combination of features is not feasible. In addition, singular references do not exclude a plurality. The terms "a", "an" does not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

Claims

1. A method for machining at least one bridge support (11 ) of a dental bridge for adjustment to at least one replica (30) that represents at least one corresponding dental implant, characterized by using each replica (30) as an electrode for adjusting a contact surface (20) of the at least one bridge support (11 ) to the shape and position of the replica representing the corresponding implant.

2. The method according to claim 1 , wherein the replica (30) is used to remove material from said bridge support (11 ).

3. The method according to claim 2, wherein the replica (30) is used for spark machining for the removal of material from said bridge support (11 ).

4. The method according to claim 3, wherein the replica (30) at least partly is made of a material suitable for spark machining, such as graphite.

5. The method according to claim 3, wherein the replica (30) at least partly is made of a material suitable for spark machining, such as carbon.

6. The method according to claim 3, wherein the replica (30) at least partly is made of a material suitable for spark machining, such as a metal or a metal alloy.

7. The method according to claim 1 , wherein the replica (30) is used to deposit material on said bridge support (11 ).

8. The method according to claim 7, wherein the replica (30) is used for electrochemical deposition for the addition of material on said bridge support (11 ).

9. The method according to claim 1 , wherein a channel (14) of the at least one bridge support (11 ) is formed by using a further electrode (70), which is moved in relation to the position of the at least one replica (30) and to a reference level.

10. The method according to claim 9, wherein the further electrode (70) is moved in a linear movement forming a straight channel (14).

11. The method according to claim 9, wherein the further electrode (70) is moved in a circular movement forming a curved channel (14).

12. The method according to any of the previous claims, wherein voltage is individually supplied to each replica (30) to provide individual control of the machining of each bridge support (11 ).

13. The method according to claim 12, wherein the voltage is sequentially supplied to each replica (30).

14. The method according to claim 12, wherein the voltage is simultaneously supplied to each replica (30) and wherein each replica (30) is galvanic insulated.

15. Device for machining at least one bridge support (11 ) of a dental bridge for adjustment to at least one replica (30) that represents at least one corresponding dental implant, characterized in that each replica (30) is arranged to be used as an electrode being adapted to adjust a contact surface (20) of the at least one bridge support (11 ) to the shape and position of the replica (30) representing the corresponding implant.

16. Device according to claim 15, characterized in that it has a further electrode (70) for forming a channel (14) of the at least one bridge support (11 ).

17. Device according to claim 16, characterized in that it has means for moving the further electrode (70).

18. Device according to claim 17, characterized in that the electrode means is adapted to perform a linear movement forming a straight channel (14).

19. Device according to claim 17, characterized in that the electrode means is adapted to perform a circular movement forming a curved channel (14).