WO2018154252A1

WO2018154252A1 - Process for manufacturing a dental article using 3d printing

Info

Publication number: WO2018154252A1
Application number: PCT/FR2018/050437
Authority: WO
Inventors: Alexandre FOREST
Original assignee: Mojito
Priority date: 2017-02-24
Filing date: 2018-02-23
Publication date: 2018-08-30
Also published as: FR3063221A1; FR3063221B1

Abstract

The application relates to a process for manufacturing a dental article, said process involving a step of 3D printing at least one portion of the dental article by consecutively depositing layers using NanoParticle Jetting, and a step of sintering at least the portion of the dental article obtained by the NanoParticle Jetting operation.

Description

Method of manufacturing a dental element

by three-dimensional printing

The present application relates to the manufacture of a dental element, for example a dental prosthetic element, an implant-borne element or a denture-supported or removable prosthesis, or even surgical guides, by a three-dimensional printing process, in particular by a printing process called "NanoParticle Jetting" ("NPJ" - it is also sometimes referred to printing technique by jet nanoparticles, or printing by jets of metallic ink).

A "dental element" here mainly, but not exclusively, refers to a dental prosthesis of the dento-worn type (such as a screed, a metal-ceramic crown, a ceramic-metal bridge, or an inlay-core) or, for example a prosthetic element of the implant-worn type (such as for example a unitary abutment (for sealed crown for example), a unitary infrastructure (for a fired ceramic crown for example), an implant-borne transvissé bridge, an implant bar for an adjoined prosthesis (that either transvissées on conical abutment or in direct-implant, but still of the type Ackermann, Dolder, Hader, RE bourke bars for attachment type Locator, bar with pillar ball, or other), or a prosthesis on stilts (for example of type Montreal, Wrap-around, Lock'n'release or others)). A "dental element" denotes a dental prosthetic element or possibly also a stellite frame or a surgical guide.

A dental element, in particular a denture-supported prosthesis, is traditionally manufactured by a prosthetist.

A very commonly used process is the casting wax technique. However, since a short time, the three-dimensional printing by laser fusion gradually supplants the technique of casting wax.

However, it turns out that three-dimensional laser fusion printing has some shortcomings, in some cases, for example: - It is often necessary to generate supports for supporting undercut areas of the element to be manufactured and / or to reattach the dental element to a three-dimensional printing plate on which the dental element is generated. These supports represent lost material, and therefore have a cost. In addition, these supports require firing time of the laser beam, thus increasing the time required for the manufacture of the dental element. In addition, these supports must then be removed, often manually and individually, from the dental element. After that, points of attachment of these supports leaving substantial traces on the surface of the dental element must be polished, for example to the turbine or the grinder, separately. Such a phase is therefore time-consuming and expensive.

- When a dental element is manufactured by three-dimensional printing by conventional laser fusion, it occasionally has a relatively rough surface that requires a finishing step, which includes a polishing step, wherein at least a portion of the surface of the element dental is polite.

Certain dental elements may require manufacturing precision that exceeds the precision capabilities of a conventional laser-based three-dimensional printing process.

According to other examples, a dental element, in particular implant-borne, is traditionally manufactured for example according to one of the following methods:

- According to a method of over-cast with burnout ducts for parts representing connectors. The dimensional characteristics and mechanical adjustments can then be very bad.

- According to a process of over-cast but with connections reported and glued. However, such an addition of glue can cause risks of crevice generating bacterial proliferation.

- By machining only, which generates a significant cost. - According to a method of three-dimensional printing of a body and machining functional areas with precise dimensional characteristics, which can induce a certain cost.

Finally, the use of a surgical guide in dental implantology has undergone a vast development with the arrival of the "cone-beam", by the guides that derive from it. This technology makes it possible to position implants optimally, both for the prosthesis and for the bone support. Most of these guides are currently produced by 3D printing in resin and not in metal, for convenience. Indeed machines for resin printing are easier to use and cheaper. However, this technology also has limitations in terms of accuracy and especially, in connection with the low mechanical resistance of a resin, which requires sizing the guide in a consistent manner, which is at the expense of accessibility for example for irrigation during drilling of the bone support, and visual implant site for, for example, ensure the smooth operation of the intervention. In addition, it is not possible to hot sterilize most of these guides because the resins used often have a melting point below the desired sterilization temperatures. However, it is possible to make these guides in 3D printing of metal but a limit to this technology is for example to generate metal supports very tedious and delicate to remove. The accuracy of a metal guide is also dependent on the surface condition that depends on the presence or absence of these supports, and the brand of the three-dimensional printing machine used.

At least one of the objectives of the present application is thus to improve at least in part the aforementioned drawbacks, leading in addition to other advantages.

For this purpose, is proposed in a first aspect, a method of manufacturing a dental element comprising:

a step of three-dimensional printing of at least a portion of the dental element by a successive deposition of layers by jets of nanoparticles, for each layer the three-dimensional printing step comprising a sub-step of forming the layer of the part of the element projection of droplets of at least one effective material in a confinement enclosure of a printing device and a substep of heating said layer in which nanoparticles of the effective material agglomerate and a binder forming a medium suspensive for the nanoparticles of the effective material is sublimated, in the containment, and

a step of sintering at least the portion of the dental element printed by jets of nanoparticles in an enclosure, the sintering step being configured to consolidate the bonds between the nanoparticles of the agglomerated effective material.

This step can be done according to various temperature levels corresponding to sublimation steps of the various compounds of the printed part. For example, a bearing to sublimate all organic components and then a gradual rise in temperature before finishing at the sintering temperature of the printed material.

This step can be carried out in a vacuum chamber or vice versa under pressure, or in an inert atmosphere, such as argon for example, to facilitate the diffusion of atoms.

Indeed, it has been found that an "NPJ" printing method is particularly advantageous for producing dental elements.

When the binder sublimes, the nanoparticles bind; in the following, the notions of binder and suspending medium are equivalent since the binder has both a role of maintaining nanoparticles but also a medium in which these nanoparticles are distributed.

As mentioned above, a printing process

"NPJ", for "NanoParticle Jetting", is a three-dimensional printing process by jets of nanoparticles, metal or even ceramic.

Such a method thus consists mainly in successively depositing layers of material by spraying fine droplets of at least one so-called "effective" material, for example by one or more piezoelectric printing heads (like a conventional "poly-jet" printing process). For example, a layer has a characteristic thickness of the order of 2 μιτι (micrometers), that is to say between 1 and 3 micrometers or even between 1.5 and 2.5 micrometers, or even between 1 .9 and 2.1 micrometers .

For example, the effective material comprises nanoparticles and a binder in which the nanoparticles are in suspension.

The binder may for example comprise at least some of the following elements and / or compounds:

• Transport compound, carrying, in suspension, the nanoparticles of the material to be printed. Examples of compounds are: Solsperce 6100 or 6300, for example of the brand Lubrizol; or Dysperbyk 163 of the brand BYK Chemie GMBH.

• Solvent compound for adding particles of the material to be printed in the matrix of the binder. This compound allows a better diffusion of the atoms of said material during the sintering in the oven.

· A dispersing compound that prevents the molecules of the final material from agglomerating with each other or on the walls of the tanks or channels.

The nanoparticles have, for example, a diameter of between approximately 10 nm (nanometers) and approximately 40 nm.

According to a preferred example, the nanoparticles of the effective material comprise a biocompatible material.

For example, the biocompatible material comprises biocompatible metal, for example titanium and / or chromium and / or a chromium-cobalt alloy, or a biocompatible ceramic material.

For example, the nanoparticles may comprise at least one of the following materials:

- feldspathic ceramics

- Vitroceramics:

o Ceramic reinforced with leucite crystals: Empress o Ceramic reinforced with lithium disilicate crystals: IPS eMAX

- Polycrystalline ceramics: alumina

- Ceramics infiltrated: o Glass infiltrated in crystals of pure alumina: InCeram Alumina o Glass infiltrated in crystals of alumina and magnesium:

InCeram Spinell

o Glass infiltrated in crystals of alumina and zirconia: InCeram Zirconia

For example, the effective material comprises a colloidal suspension.

In a particular example, the colloidal suspension comprises stochastic metal nanoparticles, that is to say which are randomly distributed, that is to say non-aligned or arranged in an orderly manner.

The layers are deposited on a manufacturing plate of a printing device, in a confinement chamber of the device, according to a principle similar to that of a poly-jet printing process.

The deposited layers are called "ultra-thin", that is to say they have a thickness of the order of 2 μιτι (micrometers).

When a section corresponding to a layer reaches a confinement chamber temperature of at least 250 ° C, or even 280 ° C or more, the binder, for example of the colloidal solution of the actual material, is sublimed and, then, the nanoparticles agglomerate, according to a phenomenon of coalescence, to form a solid part forming the part of the dental element.

Thus, typically, it is when the colloidal solution is projected into the heated enclosure that the binder sublimes once deposited.

The stack of these layers ultimately forms a volume corresponding to the portion of the desired dental element.

In an exemplary implementation, the three-dimensional printing step comprises at least one sub-step of producing a support by projection of a support material configured to fill, during at least part of the process, at least an area underdeep of the portion of the dental element in progress. In other words, if it seems useful, during the same phase, a material called "support" is deposited. The role of the support material is to maintain the initially sprayed material on areas that are likely to be backpainted and / or cantilevered, and this until solidification thereof.

Thus, for the same layer, the actual material is deposited when it is a section of the part to be produced, while the support material is deposited if it is necessary to fill a void and / or support a subsequent part in cantilevered.

The support material is, for example, wax.

For example, the support material is projected by a nozzle different from the same head as the nozzle through which the actual material is projected.

For example, the support material has a melting temperature equal to or greater than a sintering temperature of the nanoparticles of the effective material.

It may be thought that the wax has only a temporary, fleeting interest, namely during the phase of deposition of the colloidal suspension for example. After the sublimation of the transport fluid, that is to say the binder, the nanoparticles are supposed to be maintained by their interarticular friction.

When the printing of the portion of the dental element is complete, said part of the dental element is sintered, in an enclosure, possibly different from the confinement enclosure of the printing device, for example an oven or an oven , in order to consolidate the links between agglomerated nanoparticles. The cohesion of the piece is then ensured.

During this phase, any supports are melted, giving the piece its final shape.

In other words, the method comprises for example a support melting step.

A metallurgical result is virtually identical to metal from traditional manufacturing, for example by foundry. In an exemplary implementation, the method then possibly comprises a step of supercooling a portion of the dental element on the part of the dental element obtained at the outlet of the sintering step, that is to say say that one forms a first part of the element by jets of nanoparticles, then a second part on this first part.

Beforehand, the part to be produced, the dental element, is modeled numerically, then the corresponding numerical model is divided into slices, each slice of which corresponds to a layer that will be deposited by the printing device, at least for the part of the part which is to be realized by three-dimensional printing. The digital model is for example provided in the form of an STL file or other. Each slice therefore represents for example a thickness of the order of 2 μιτι.

Such an NPJ printing method has for example the following advantages over a conventional additive manufacturing technology, that is to say for example a three-dimensional laser melting process:

- The level of resolution of the parts is more precise because of the thin thicknesses used, which allows better dimensional and geometrical accuracies, approaching those obtained by machining. For example, it is thus possible to obtain a very good precision of a marginal line of the dental element.

- The level of residual stress is negligible in that the constituent material of at least the portion of the dental element made via this process is not fully heated to its melting point; there are no deformations or constraints related to clusters of material or heat treatment restrictive detention for the material, for example made just before detaching the parts of the tray on which they are built; this prevents them from being expressed and therefore deform during this operation or during the cutting phase.

- The surface condition obtained is better, as well as accuracy, compared to laser melting or electron beam technologies, for example close to a machining by chip removal, that is to say that the Average roughness Ra obtained for the surface is for example between about 0.2 μιτι and about 1 μιτι.

- The porosity of the material constituting the finished part is much more constant because the imbrication of nanoparticles leaves no gaps or macroscopic porosity. As a purely illustrative example, in traditional additive manufacturing, the commonly accepted rate is typically less than 1% whereas it may be less than 0.1% with an NPJ process.

- It is possible to dispense with the use of a bed of powder, which implies the use of powder in the manufacturing chamber, and an additional cost related to the storage thereof.

- The NPJ uses only the volume of material corresponding to that of the parts to be printed.

- The materials used are easier to handle because they are in the form of cartridges, similar to ink cartridges in inkjet processes, and thus present much less danger than when it comes to handle free metal powders. Not only is it possible to overcome the dangerous nature of the use of powdered products for health, but also for the environment.

- The chamber of the device used is not necessarily an inert atmosphere of nitrogen or argon, because the method uses the material in the liquid state which reduces the risks inherent in the use of powder.

- The supports intended to support the areas underdepth of the parts made are easy to remove and therefore do not present a constraint generating geometric restrictions.

- The printing time is faster (for example up to 5 times more productive) than the time required to achieve the same element by means of a laser or electron beam printing process (roughly estimated between 2 and 8 mm ³ / s depending on the type of material). It is also possible to make several elements in the same batch, that is to say simultaneously. Productivity is thus improved. It is thus possible to be more responsive to any request. - There is no loss of effective material related to the production of support, which reduces production costs.

Indeed, for example, it is possible to dispense with a step of polishing media attachment points which is often time-consuming and expensive and likely to alter the printed part because in a process NPJ the supports are made with a material of different origin of the actual material used for the part of dental element made and there is no physical junction before, and from there, no residual marks that should be polished. Thus, such a method makes it possible to remove these supports in an easy and autonomous manner, by sublimation of the material constituting them, for example during the sintering phase of the portion of the dental element produced.

Thus, in some cases, the dental elements can exit directly ready for use of such a process, or else with only a minimum of post-treatment steps, for example to obtain a mirror-polished appearance on certain surfaces of the dental element.

In other words, a major advantage of such a method is that the level of finish and accuracy output allows to overcome a step of recovery in machining, currently commonly used for parts to be assembled with other parts (implants, "multi-units").

Nevertheless, it may still be relevant and / or necessary to perform machining in cases where the required accuracy is important and exceeds the resolution of the NPJ process.

Another major advantage of this method lies in the fact that it is possible to overcome the problems of media, while allowing the use of metal or ceramic that have more interesting mechanical properties.

In the case of guides obtained by this method, these then have the following advantages, for example:

they can be sterilized in an autoclave,

- They can be thin and hollow in order to visually and physically access the implant sites, and to irrigate them without being masked by a geometric cluster, - They have good geometric accuracy compared to the three-dimensional printing of traditional metal, despite a ratio of the section compared to the less favorable length,

- They have a good roughness, which saves time on the post-finishing treatment, or even to emancipate.

To implement such a method, an NPJ printing device mainly comprises a containment chamber and a manufacturing plate, positioned in the containment chamber and from which it can be extracted if necessary.

Such a device also comprises an arm, which may comprise one or more print heads, the head or heads opening into the confinement enclosure, for example at least ten or twenty heads, for example twenty-four (24) heads (number mentioned by some manufacturers in the field of NPJ), or more.

In parallel, each head may possibly comprise one or more nozzles, for example at least ten or even fifty or even one hundred or even several hundred nozzles, for example five hundred and twelve (512) nozzles. Such a device then allows for example to project several thousand droplets per second, for example about 18,000 droplets per second according to the above values for illustrative purposes.

It is also proposed, in another aspect, a use of a three-dimensional printing process by jets of nanoparticles to manufacture at least a portion of a dental element.

This is for example to use a three-dimensional process of printing "NanoParticle Jetting" comprising at least a portion of the features described above, to manufacture at least a portion of a dental element.

The use of such a method thus has advantages similar to those described above.

The invention, according to an exemplary embodiment, will be well understood and its advantages will appear better on reading the detailed description which follows, given for information only and in no way limitative, with reference to the appended drawings in which:

FIG. 1 shows implant abutments with their support in the form of network rods, according to one embodiment by three-dimensional printing of the prior art,

FIG. 2 shows implant abutments, similar to those of FIG. 1, with their support, as obtained by a method according to an embodiment of the present invention,

Figure 3 shows the implant abutments of Figure 2 without their support, as obtained by the method according to an embodiment of the present invention,

FIG. 4 shows an example of dento-carried element with its support, as obtained by a method according to an embodiment of the present invention,

FIG. 5 shows a stellite frame with its support, as obtained by a method according to an embodiment of the present invention,

FIG. 6 shows the stellite frame of FIG. 5 devoid of its support, as obtained by the method according to an embodiment of the present invention,

Figure 7 shows a guide as obtained by a traditionally used embodiment method, and

Fig. 8 shows a guide as obtained by a method according to an embodiment of the present invention.

Identical or similar elements shown in the above figures are identified by identical or similar numerical references.

A unitary dental prosthesis, called "implant-borne", whether pillar or unitary infrastructure, traditionally comprises three main elements: a crown (not shown), a pillar 10 and an implant (not shown). The implant, traditionally manufactured by machining, behaves like a foundation that is anchored in the bone. This is usually a monoblock element. To be anchored in the bone, it often has an outer thread formed on at least one lower sector. In an upper sector and excluding intraosseous burial, the implant is often provided with a cavity that typically allows an insert 30 of the pillar 10 to come and connect to it. For this, the cavity thus opens at an upper end of the implant, that is to say a free end of the upper sector. The cavity allows the conventional functions of a traditional connection that are, in particular, clamping and angular indexing through repositioning geometries. Finally, the implant further generally comprises means for attaching at least the abutment in the implant, such as, for example, a threaded bore in the cavity configured to receive a screw.

A pillar 10 forms an interface between the implant and the crown. The pillar, qualified as dental or implant, has a preponderant role in the success of the implant case in that it ensures both a transmission of occlusal forces and an aesthetic component by healing the gingival tissues ensuring the respect of the biological space. Therefore, each pillar is specific to an implant and a crown, which is performed on a case by case basis. For the positioning of the pillar to be good, it is necessary precisely to conform a lower part of the pillar, called insert 30, according to the implant, and an upper part of the pillar, called body 20, according to the crown which represents the tooth To replace.

The pillar 10 thus comprises here by definition two main parts: an insert 30, in the lower part, and a body 20, in the upper part.

The insert 30 and the body 20 may be of any type of biocompatible metallic material, for example titanium or a cobalt-chromium alloy.

In order to fix the abutment 10 to the dental implant, the insert 30 can have different shapes and different profiles. The range of inserts thus makes it possible to cover the various clinical cases encountered. However, it can have a generic form, standard, that is to say be identical for several different pillars depending on the type of implant for which it is intended. The insert 30 comprises, by definition, an upper portion 31, in an extension of the body 20, and a lower portion 32, in an extension of the upper portion 31, which comprises a connector 33 configured to connect the insert 30 to the implant, at least axially. In other words, the upper part 31 is situated between the lower part 32 and the body 20.

The insert 30 is for example mainly axisymmetric, except the connector 33 and, generally, has a flared shape from the connector to the body, as shown in Figure 1.

The body 20 and the upper part 31 may have any type of shape.

The bodies are made to measure, case by case, depending on the morphology of the tooth to be replaced, that is to say the crown to which it is intended to be connected, and the profile of the bone ridge and the gum.

Thus, the body 20 generally needs to be made to measure while the insert 30 may be standard, but the insert has a connector that must be made precisely for its assembly with an implant.

For this, it had for example proved particularly interesting to combine an additive manufacturing process, in particular by laser melting, with an electroerosion process. Such a method has for example been described in French Patent Application No. 1655629 filed on June 16, 2016.

Figure 1 shows pillars 10 obtained by an example of implementation of such a method.

The implant abutments are then formed "upside down" on a platen 50 of manufacture. Thus, the connectors 33 are then a free portion oriented upwardly relative to the plate 50 of manufacture.

However, in such a method, a pillar 10, before finishing, further comprises a support 40, for example a reinforcement allowing a maintenance and a primer to the manufacture of the corresponding pillar. In a particularly interesting embodiment which is shown here, the support 40 comprises rods, for example arranged in a network. Such rods are then for example easily scored for detach from the pillar. However, such a method then requires a subsequent withdrawal of the support 40 which generally generates a recovery step in finishing, for example a polishing.

Similarly, it is also possible to resume machining the body 20 and the upper part 31.

However, it is interesting to be able to dispense with such a step in certain cases.

A manufacturing process comprising at least one step of successive deposition of layers by NanoParticle Jetting (NPJ) was then particularly interesting.

Such a method also makes it possible to produce simultaneously, that is to say during the same batch on the same plate, a plurality of dental elements, it being understood that "plurality" here means at least two; but, in the present context, it is possible to produce for example at least five or even ten or even twenty dental elements simultaneously, or even more.

In particular, for each layer, the three-dimensional printing step then comprises in particular a substep of forming the layer of the portion of the dental element by projection of droplets of at least one effective material, for example in a confinement enclosure of a printing device, and a substep of heating said layer in which nanoparticles of the effective material agglomerate and a binder of the effective material is sublimated in the containment.

In an exemplary implementation, the three-dimensional printing step also comprises at least one sub-step of producing a support by projection of a support material configured to fill, during at least part of the process, with the least an area underdeep of the portion of the dental element in progress.

Figure 2 shows dental elements which are abutments obtained at the end of such steps.

The pillar 10 shown to the right of Figure 2 is shown in section so as to better illustrate the presence of the support 40, which is here massive, formed around the body 20. Then, for example, the method comprises a step of sintering the abutment 10 printed by NPJ in an enclosure, the sintering step being configured to consolidate the bonds between the nanoparticles of the agglomerated effective material.

Such a step can take place in a different enclosure or in the same enclosure.

During this step for example, the method then comprises a step of melting the support.

If necessary, it is then preferable that the material constituting the support has a melting temperature equal to or greater than a sintering temperature of the nanoparticles of the effective material.

FIG. 3 shows pillars 10 obtained at the end of such a step, that is to say that they are now devoid of their support 40.

FIG. 4 illustrates the method according to an exemplary implementation applied to a dento-carried element 10 'with its support 40'.

FIG. 5 illustrates the method according to an implementation example applied to a stellite frame 10 "with its support 40" and FIG. 6 shows the stellite frame 10 "of FIG. 5 devoid of its support 40", such as obtained by the method according to an embodiment of the present invention after a step of melting the support 40 ".

These FIGS. 5 and 6 make it possible to better illustrate the advantage of the presence of a support made in an embodiment of the present invention when the dental element to be made comprises various highly complex or cantilever parts. .

FIGS. 7 and 8 make it possible to compare two guides: one obtained by a method of realization conventionally used (FIG. 7) by 3D printing and the other obtained by a method according to an embodiment of the present invention (FIG. 8).

The guide of Figure 7 is for example solid and integrally resin. Metal inserts can be added in the active parts for the guidance of ancillary tools. The guide 10 "'of Figure 8 is then feasible metal, which allows to sterilize hot and have a mechanically stronger guide, more solid.In addition, it may have a more ventilated structure and / or more complex - that is to say also more adaptable to any type of morphology - and at the same time allows better accessibility to the implant site.

Thus, such a method makes it possible to produce, during the same batch, several dental elements, whatever they may be (for example both one or more pillar (s) and / or one or more dental element (s). carried 10 'and / or one or more stellite frames 10 "and / or one or more guide (s) 10" etc.), for example on the same plate 50.

Claims

1. A method of manufacturing a dental element (10, 10 ', 10 ", 10"') comprising:

a step of three-dimensional printing of at least a portion of the dental element (10, 10 ', 10 ", 10"') by a successive deposition of layers by jets of nanoparticles, for each layer the step of three-dimensional printing comprising a substep of forming the layer of the portion of the dental element (10, 10 ', 10 ", 10"') by projecting droplets of at least one effective material into a confinement enclosure a printing device and a substep of heating said layer in which nanoparticles of the effective material agglomerate and a binder forming a suspending medium for these nanoparticles of the effective material is sublimated in the containment, and

a step of sintering at least the portion of the dental element (10, 10 ', 10 ", 10"') printed by jets of nanoparticles in an enclosure, the sintering step being configured to consolidate the links between the nanoparticles of the actual material agglomerated.

2. The method of claim 1 wherein the nanoparticles of the effective material comprise a biocompatible material which comprises biocompatible metal or a biocompatible ceramic material.

3. Method according to any one of claims 1 or 2 wherein the three-dimensional printing step comprises at least one sub-step of producing a support (40, 40 ', 40 ") by projection of a material carrier assembly configured to fill, during at least a portion of the method, at least one area in a counterpane of the portion of the dental element (10, 10 ', 10 ", 10"') in progress.

4. The method of claim 3, comprising a step of melting the support (40, 40 ', 40 ").

5. Using a three-dimensional printing process by jets of nanoparticles to manufacture at least a portion of a dental element (10, 10 ', 10 ", 10"').