SE541698C2 - Dental superstructure and method for producing a dental superstructure - Google Patents

Abstract

The present disclosure relates to a method for producing a dental superstructure (1) comprising an extending part (11), configured to resemble a tooth or a set of teeth, and at least one interface part (9), configured to connect the superstructure (1) to an implant (3). The interface part (9) has a projecting connector piece (13), and the extending part (11) has a connector recess (15) therein formed with additive manufacturing, such that the outer shape of the connector piece (13) of the interface part (9) corresponds to the inner shape of the connector recess (15), while having slightly greater dimensions than the latter. The interface part (9) is attached to the extending part (11) with a press fit. This allows a greater freedom of choice of location when placing implants in a jaw bone.

Description

DENTAL SUPERSTRUCTURE AND METHOD FOR PRODUCING A DENTAL SUPERSTRUCTURE Field of the invention The present disclosure relates to a method for producing a dental superstructure comprising an extending part, configured to resemble a tooth or a set of teeth, and at least one interface part, configured to connect the superstructure to an implant, wherein the extending part is obtained with an additive manufacturing process and the interface part is produced as a separate piece.

The present disclosure further relates to a corresponding dental superstructure.

Technical background Such a method is disclosed in WO-2015/090518-A1. That document shows the building up of a dental superstructure, using additive manufacturing, on top of an interface part that may be a standard component. The interface part, which is not made up by means of an additive manufacturing process, may have sufficiently small tolerances to connect properly to an implant without costly post-processing of the surfaces intended to connect with the implant, which provides for a less expensive superstructure.

One problem with superstructures of the initially mentioned kind is that they primarily allow use under rather simple circumstances, mostly to replace a single tooth and where the underlying bone tissue provides easy access to the implant.

Summary of the invention One object of the present disclosure is therefore to provide a method for producing a dental superstructure that is more versatile.

This object is achieved by means of a method as specified in claim 1. More specifically, in a method of the initially mentioned kind, the interface part is provided with a projecting connector piece. When the extending part is produced by means of additive manufacturing, a connector recess is formed in the interior thereof. The outer shape of the projecting connector piece of the interface part corresponds to the inner shape of the connector recess, while having slightly greater dimensions than the latter. The interface part is attached to the extending part with a press fit between the projecting connector piece and the connector recess. This provides a superstructure where the extending part can have additive manufacturing layers that extend in an arbitrary direction with respect to the orientation of the interface part, which gives a greater flexibility, allowing the interface part and hence an implant to which it is connected to extend in different possible directions with regard to the layers of the extending part. At the same time, the interface part can be produced as a standard component, and the extending part can be finished using additive manufacturing. A reliable connection may be provided between the two parts.

The extending part may be heated before attaching the interface part thereto. This is an efficient and reliable way of achieving a tight press fit. Typically, the extending part may be heated to a temperature e.g. 200 °C, substantially higher than the temperature of the interface part before being fitted thereon.

The projecting connector piece may have an outer cylindrical or conical surface and the connector recess a corresponding inner cylindrical or conical surface.

Additionally, the projecting connector piece and the connector recess may form a bayonet mount to make the connection therebetween even stronger. The bayonet mount may be formed by projecting lugs on the inner cylindrical or conical surface of the connector recess and corresponding grooves in the outer cylindrical or conical surface of the projecting connector piece, for example.

The interface part may be produced by milling and/or turning, for example.

The outer end of the interface between the projecting connector piece and the connector recess may be sealed after fitting the extending part to the interface part. This prevents microbes etc. from entering in between the parts.

A single interface part may be provided, the extending part forming a dental crown, or alternatively a plurality of interface parts, the extending part forming a dental bridge intended to replace several teeth.

The extending part may be produced by use of electron beam melting, EBM, selective laser melting, SLM, blown powder technologies or ink-jet printing, for example.

The present disclosure also considers a dental superstructure comprising an extending part, configured to resemble a tooth or a set of teeth, and at least one interface part, configured to connect the superstructure to an implant. The extending part comprises a material obtained with an additive manufacturing process and the interface part comprises a separately produced piece. The interface part has a projecting connector piece, and the extending part has a connector recess in the interior thereof. The outer shape of the projecting connector piece of the interface part corresponds to the inner shape of the connector recess, while having slightly greater dimensions than corresponding dimensions of the extending part, such that the interface part may be attached to the extending part with a press fit between the projecting connector piece and the connector recess.

The projecting connector piece and the connector recess may form a bayonet mount.

The dental superstructure may further be embodied as defined by the above discussed method.

Brief description of the drawings Fig 1 shows in cross section a dental superstructure, according to prior art, about to be connected to an implant.

Fig 2A shows schematically a perspective view of an extending part of a superstructure according to the present disclosure.

Fig 2B shows an enlarged portion thereof.

Fig 3 shows a perspective view of a corresponding interface part.

Fig 4 is a flow-chart illustrating steps of a method according to the present disclosure.

Fig 5 shows in cross section a superstructure with a substantially angled interface part.

Fig 6 shows a dental bridge with multiple interface parts.

Fig 7 is a cross section through a connector recess of an extending part.

Fig 8 is a front view of an interface part for the extending part of fig 7 but with a greater scale.

Fig 9 illustrates an interface part according to a second example of the present disclosure.

Fig 10 illustrates an extending part according to the second example.

Detailed description The present disclosure relates to methods and devices for dental restoration. To replace lost teeth in a patient’s mouth, there exist techniques for attaching biocompatible implants in the jaw bone of the patient and, once the implant has been connected to the healed bone tissue, attaching superstructures to the implant. The superstructures comprise extending anatomical parts that may be carefully designed to resemble the missing tooth or teeth.

Fig 1 shows schematically in partial cross section a dental superstructure 1 according to prior art, about to be connected to an implant 3. When, as illustrated, a single tooth is replaced, an implant 3, made in a biocompatible material such as titanium, is surgically attached in the jaw bone 5 of a patient. The implant 3 is allowed to rest for a number of days or weeks, such that the jaw bone 5 heals, and the implant 3 becomes firmly connected to the bone 5 (osseointegration).

Then, a superstructure 1 comprising an extending or anatomical part 11 or piece is attached to the implant by means of an attachment screw 7, which is screwed into the implant 3. The extending part 11 is produced such that its geometry resembles a real tooth, preferably the tooth it replaces, if available. This provides an aesthetically appealing tooth replacement and facilitates chewing.

Traditionally, such superstructures have been made by milling a solid piece of metal into a desired shape using CAD/CAM techniques. Such a process is however very expensive, especially if a bridge replacing a number of teeth is formed.

More recently, techniques have been introduced where additive manufacturing processes are used to produce the superstructure. Such techniques however usually require post-processing of the superstructure to provide the required tolerances where the superstructure is connected to an implant, e.g. by milling, which is an expensive procedure.

Additive manufacturing processes in this context means technologies where a piece of material is built up, layer by layer, similar to plastic 3D printing techniques. To build a metal based piece for instance, a thin layer of metal powder may be applied to a previously produced layer. The powder is then melted or sintered to integrate with the previous layer by applying energy, for instance by means of an electron beam or a high-energy laser beam. As an alternative to powder, thin wires can be applied. The process is based on a 3D model describing the desired shape of the piece.

Such techniques are well known per se. Electron beam melting, EBM, selective laser melting, SLM, blown powder technologies and various ink-jet printing technologies may be considered.

To avoid post-processing of a superstructure prepared with additive manufacturing, it has been suggested, as described in the aforementioned document and in fig 1 , to produce a superstructure’s extending part 11 on top of a pre-manufactured interface part 9. This allows the interface part 9 to be a standard component produced in a comparatively efficient process, even though the finished superstructure is unique, based on the recipient’s replaced tooth, for instance. The interface part 9 may thus be series produced with high precision and at relatively low cost.

As illustrated in fig 1 , the normal of the interface part 9 must be aligned with the normal of the layers building up the extending part 11 by additive manufacturing. This means in turn that the center axis of the attachment screw 7 must be aligned with this normal as well, which limits the flexibility of use of the dental implant.

An improved superstructure is shown with reference to figs 2A, 2B, 3 and 4. An interface part 9, as shown in fig 3 is prepared 101 (of. fig 4) as a separate piece. This may be done by turning and/or milling, and for instance Titanium, Chromium-Cobaltor stainless steel, or other biocompatible materials may be considered as a suitable material for the interface part 9. The interface part 9 is provided with a projecting connector piece 13 which may present a conical or cylindrical outer surface 14.

An extending or anatomical part 11 is produced 103 with an additive manufacturing process as mentioned earlier. While this is done, a connector recess 15 is formed in the interior of extending part 11. The outer shape of the projecting connector piece 13 of the interface part 9 corresponds to the inner shape of the connector recess 15, but its dimensions are slightly greater than the ones of the connector recess 15, as will be discussed further.

The extending part 11 may be produced upside-down on a base plate (not shown). This means that the layers forming the top of the extending part 11 are formed first and the lower end of the extending part including the connector recess 15 are formed last. The base plate is subsequently removed. Typically, the extending part may be connected to the base plate with a layer forming a few dots, such that the base plate can easily be snapped off.

The interface part 9 is attached 107 to the extending part 11 with a press fit between the projecting connector piece 13 and the connector recess 15. This may be done by heating 105 the extending part 11 , although it may as well be possible to instead cool the interface part 9. It would also be possible to provide a press fit without obtaining a temperature difference and simply applying a significant force to obtain the press fit.

The heated extending part 11 is fitted on the interface part 9 optionally using a bayonet mount or the like. Once the parts’ temperatures have become somewhat equalized a strong press fit is established.

With this method a sufficiently strong connection between the interface part 9 and the extending part 11 may be obtained. By using a press fit, the manufacturing tolerances may still be low enough, as the press fit compensates for any mismatch between the parts. The press fit compensates for the relatively rough surfaces provided in the recess as a result of the additive manufacturing process. The rough surfaces also deform the outer surface of the projecting part to some extent to provide a very strong fit.

At the same time, as the connector recess 15 may be fully formed by additive manufacturing, a much greater freedom of choice of orientation of the connector recess 15 may be obtained. This means that, as for instance is schematically indicated in the cross section of fig 5, that the interface piece axis 17 may deviate significantly from the orientation of the additive layers’ normal direction in the extending part 11. Thanks to this feature, the superstructure may in many cases be attached to the jaw bone 5 in a reliable way, even if the jaw bone in the space 19 directly below the superstructure is absent or of low quality. Jaw bone tissue located slightly in front of that space may be used instead, for instance.

The surgeon therefore has a greater freedom when locating the implants, and can for instance locate the implant at a jaw bone location with best possible jaw bone quality.

As illustrated in fig 5, the extending part 11 may include a channel 21 through which the attachment screw 7 can be accessed in order to attach the superstructure to the implant 3. This channel 21 may subsequently be filled with a composite glue in order to avoid cavities that may be difficult to clean.

Once the interface part 9 is attached to the extending part 11 , the outer interface 23 between the projecting connector piece and the connector recess may be sealed for instance with a glue or by welding. This prevents e.g. microbes from entering in between the extending part 11 and the interface part 9. It also may make the connection between the two parts even stronger.

The advantage of the present disclosure is even more pronounced in dental bridges, resembling multiple teeth and having more than one attachment point. Fig 6 shows schematically a dental bridge 25 with multiple interface parts 9. As shown, such interface parts may extend along connector axes 17 that are not mutually parallel. Therefore, a specific relationship between each of those axes and the planes in which the layers of the extending parts are located is not possible. Those layers will extend in mutually parallel planes throughout the extending part 11.

Precision of fit is important in case a superstructure is supported by more than one implant. Osseointegrated implants have little resilience in the bone. Lack of passive fit between supporting implants and a superstructure increases the risk of biomechanical stress development when the superstructure is screw-tightened to the implants by means of attachment screws. Such stresses may cause micro-fractures of the bone surrounding the implant, and other adverse effects that may negatively influence implant longevity. The superstructure of the present disclosure may be tailored to a set of implants with high precision.

Fig 7 shows a cross section through a connector recess 15 of an extending part. This recess may be generally circular symmetric about a center recess axis 29, and may as illustrated comprise cylindrical and/or conical surface sub portions with dimensions that decrease with an increasing distance from the mouth of the recess 15.

If possible with regard to the size of the extending part 11 as a whole, it may be advantageous to include a bayonet mount in the connector recess 15. Then, in one example, lugs 27 which extend from the interior wall of the connector recess 15 may be provided. This deviates from the general circular symmetric shape mentioned above.

Fig 8 shows a front view of an interface part 9. The interface part may be generally circular symmetric about a center axis 39 as well, and may comprise a projecting connector piece 13 with corresponding outer cylindrical and/or conical surface sub portions as the inner sub portions of the connector recess 15.

The projecting connector piece 13 of the interface part 9 may however have slightly greater dimensions (Fig 7 and 8 do not have the same scale). Thus, for instance the inner diameter Di of a portion of the connector recess 15 of the extending part 11 may be 2.99 mm, while the corresponding outer diameter Do of the projecting connector piece 13 of the interface part 9 may be 3,00 mm. In general, a very small dimension difference depending on the used material is suitable to obtain a sufficient press fit.

With the above-mentioned dimensions Di and Do for instance, it is sufficient to heat the extending part 11 to 200 °C while the interface part remains a room temperature 20 °C. With this temperature difference the interface part 9 can readily be fitted with the extending part 11. Once the extending part has cooled to room temperature, a strong press fit is achieved. The extending part 11 can be heated e.g. with a hot-air gun or in an oven. In principle, it would be possible as well to cool the interface part 9, or to both cool the interface part 9 and heat the extending part 11. In some cases, especially if no bayonet mount is used, it would also be possible to simply press the extending part 11 to fit on the interface part 9 with a high mechanical force.

As also shown in fig 8, the bottom piece of the interface part 9 presents an implant contact surface 33 with a shape that may correspond to the top of the implant. If the superstructure is connected to one single implant, it may be advantageous to provide the contact surface 33 with a feature that deviates from the circular symmetric form, i.e. a locking feature. If this feature cooperates with a corresponding feature in the implant, it may be prevented that the superstructure turns once attached to the implant. For instance, an outer hexagonal shape may be provided on the contact surface 33, and a corresponding inner hexagonal shape in the implant, the end of the interface part resembling and Allen key and a corresponding hexagonal socket being provided in the implant.

The interface part 9 is also provided an inner ledge 31 on which the head of the attachment screw 7 can rest to attach the interface part 9 to the implant. The attachment screw 7 then reaches through an opening 35 at the implant contact surface 33.

The interface part 9 also comprises a main opening 37 through which the attachment screw 7 can reach the lower part of the interface part 9.

To interact with the lugs 27 of the extending part 11 , the interface part 9 may comprise e.g. L-shaped slots 41 or grooves through which the lugs 27 may pass when the extending part 11 is fitted to the interface part 9. The bayonet mount thus comprises the lugs 27 and the L-shaped slots 41. One such slot is shown in the front of fig 8, and another is partly hidden at the rear side of the interface part 9. With this L-shape, the connecting piece 13 of the interface part 9 is first moved along its center axis 39 into the connecting recess 15 of the extending part 11 , and is subsequently turned some degrees until the lugs 27 reach the end of the slot 41. This bayonet lock in combination with a press fit achieved e.g. by heating the extending part 11 provides a very strong and reliable connection between the interface part 9 and the extending part 11.

As illustrated in fig 9 and fig 10, showing an alternative example, the bayonet mount may be reversed such that the lugs 27 are located on the face of the interface part’s 9 projecting connector piece 13. Correspondingly, inner grooves 43 are formed on the inside of the connection recess in the extending part. Needless to say, other means for providing interacting locking features in the recess 15 and on the projecting connector piece 13 are known to the skilled person.

The present disclosure is not restricted to the above-described examples and may be varied and altered in different ways within the scope of the appended claims.

Claims (13)

1. A method for producing a dental superstructure (1) comprising an extending part (11), configured to resemble a tooth or a set of teeth, and at least one interface part (9), configured to connect the superstructure (1) to an implant (3), wherein the extending part (11) is obtained with an additive manufacturing process and the interface part (9) is prepared as a separate piece, characterized by: -providing the interface part (9) with a projecting connector piece (13); -forming a connector recess (15) in the interior of extending part (11) while producing the extending part (11) by means of additive manufacturing, such that the outer shape of the projecting connector piece (13) of the interface part (9) corresponds to the inner shape of the connector recess (15), while having slightly greater dimensions than the latter; wherein the projecting connector piece (13) is provided with an outer cylindrical or conical surface and the connector recess (15) is provided with a corresponding inner cylindrical or conical surface, and the projecting connector piece (13) and the connector recess (15) form a bayonet mount; and attaching the interface part (9) to the extending part (11) with a press fit between the projecting connector piece (13) and the connector recess (15).

2. Method according to claim 1, wherein the extending part (11) is heated before attaching the interface part (9) thereto.

3. Method according to claim 2, wherein the extending part is heated to a temperature that is at least 200 degrees Celsius.

4. Method according to claim 1 , wherein the bayonet mount is formed by projecting lugs (27) on the inner cylindrical or conical surface of the connector recess (15) and grooves (41) in the outer cylindrical or conical surface of the projecting connector piece (13).

5. Method according to any of the preceding claims, wherein the interface part (9) is provided by means of milling and/or turning.

6. Method according to any of the preceding claims, wherein the outer end (23) of the interface between the projecting connector piece (13) and the connector recess (15) is sealed after fitting the extending part (11) to the interface part (9).

7. Method according to any of the preceding claims, wherein a single interface part (9) is provided, the extending part forming a dental crown.

8. Method according to any of the claims 1-6, wherein a plurality of interface parts (9) are provided, the extending part forming a dental bridge (31).

9. Method according to any of the preceding claims, wherein the extending part is produced by electron beam melting, EBM, selective laser melting, SLM, or blown powder technologies.

10. A dental superstructure (1) comprising an extending part (11), configured to resemble a tooth or a set of teeth, and at least one interface part (9), configured to connect the superstructure (1) to an implant (3), wherein the extending part (11) comprises a material obtained with an additive manufacturing process and the interface part (9) comprises a separately produced piece, characterized by the interface part (9) having a projecting connector piece (13), the extending part (11) having a connector recess (15) in the interior thereof, such that the outer shape of the projecting connector piece (13) of the interface part (9) corresponds to the inner shape of the connector recess (15), while having slightly greater dimensions than the extending part (11), such that the interface part (9) may be attached to the extending part (11) with a press fit between the projecting connector piece (13) and the connector recess (15), and, wherein the projecting connector piece (13) and the connector recess (15) form a bayonet mount (27, 41).

11. Dental superstructure according to claim 10, wherein the bayonet mount is formed by projecting lugs (27) on the inner cylindrical or conical surface of the connector recess (15) and grooves (41) in the outer cylindrical or conical surface of the projecting connector piece (13).

12. Dental superstructure according to any of claims 10-11, wherein a single interface part (9) is provided, the extending part forming a dental crown.

13. Dental superstructure according to any of claims 10-11, wherein a plurality of interface parts (9) are provided, the extending part forming a dental bridge (31).