Patent Application
20240164877
The present invention relates to a method for manufacturing a dental prosthesis, for example a removable dental prosthesis, complete or partial (more commonly called “stellite”).
It also relates to a shell mould configured to carry out such a method.
A dental prosthesis designates here an apparatus for replacing at least some of the natural teeth.
A removable dental prosthesis is a prosthesis that can be removed from the mouth for example for its daily maintenance or to sleep.
A “complete” dental prosthesis, also called dentures, designates a prosthesis that replaces all of the teeth, whether of the upper jaw for an upper denture or of the lower jaw for a lower denture.
A “partial” dental prosthesis is used when only one tooth, or some of the teeth, but not the totality, must be replaced.
A partial prosthesis thus conventionally comprises a metal chassis, or stellite, used to support artificial teeth that are positioned at the location of the missing teeth. This metal chassis (usually containing chromium-cobalt-molybdenum), rigid, bears both on the remaining teeth and on the mucosa, mainly the gums.
A dental prosthesis can also be maintained in place in the mouth by at least one implant. An implant is a metal element, possibly fastened via a screw, in the bone, in order to replace the tooth root of a tooth.
The manufacturing of dental prostheses requires the implementation of a protocol comprising a succession of high-precision steps, among which a step called flasking. This step involves taking the imprint of a prosthesis model made of wax, in a mould made of two separatable parts, called flask. The model is made manually by a prosthetist and includes artificial teeth disposed one after the other on the model.
In some cases, the taking of an imprint is carried out by casting plaster inside the flask. When the plaster is solidified, the flask is scalded and the wax, by melting, is eliminated and leaves an imprint in the plaster. A cooling of the mould made of plaster is necessary before casting a material, generally a resin, in the imprint in which artificial teeth have previously been disposed.
In other cases, the taking of an imprint is carried out by pouring a gel inside the flask. When the gel is solidified, the model made of wax can then be removed manually without a scalding phase. However, the artificial teeth must be separated from the model made of wax before being positioned in the imprint formed by the gel. Moreover, the artificial teeth are generally scalded in order to eliminate the wax residues.
This flasking step, in particular the substeps of solidification of the plaster, of scalding the flask, of cooling or of separation of the artificial teeth from the model made of wax are time-consuming and considerably delay the effective creation of the prosthesis.
The present invention thus aims to overcome, at least partly, these disadvantages.
It aims in particular to propose a method allowing to save time and increase the ease of manufacturing of a dental prosthesis.
For this purpose, the invention relates, according to a first aspect, to a method for manufacturing a dental prosthesis including:
a Such method for manufacturing a dental prosthesis according to the invention thus allows a possible saving of time by avoiding steps such as the scalding and the cooling of the flask.
Indeed, the prosthesis model made of wax is substituted here by a jaw portion manufactured from a digitally designed model.
In practice, the jaw portion is manufactured in a single piece.
Therefore, no artificial tooth needs to be removed or scalded since the jaw portion is in one piece and is not necessarily reused in the rest of the method, which allows to position the artificial teeth directly after the taking of an imprint and to abstain from the usual steps of scalding or of recovering the artificial teeth.
Moreover, a material forming the jaw portion can then be recycled to allow the manufacturing of other dental prostheses or of other products. The same applies to the material forming the teeth replica, which can be manufactured in the same manner as the jaw portion.
In an exemplary embodiment, the step of manufacturing the jaw portion and the step of manufacturing the teeth replica are carried out simultaneously.
Thus, the time of production of the prosthesis can be shortened.
A method according to the invention thus allows to easily and quickly obtain a dental prosthesis made on a case-by-case basis, that is to say made to order.
Moreover, the use of a replica of a patient's teeth for the manufacturing of the prosthesis, and more precisely during the step of casting a filling material, allows to obtain a more precise match between the prosthesis and the environment into which it is intended to be inserted than the usual methods.
The presence of a positioning member on the teeth replica, and thereby on the jaw portion, allows a more precise positioning of these two elements on the shell of the shell mould via the complementary positioning member. This thus allows to position the teeth replica more precisely inside the imprint of the jaw portion.
The positioning member is also used, in particular when it interacts with the complementary positioning member, to maintain the jaw portion or the teeth replica in place on the shell of the shell mould. Such a positioning member is for example formed on a lower portion of the teeth replica.
According to a preferred example, the positioning member interacts according to a sliding link with the complementary positioning member arranged on the shell.
For example, the interaction between the positioning member and the complementary positioning member can form a dovetail assembly.
In this way, the movement of the jaw portion or of the teeth replica with respect to the shell is limited to translation according to a single axis defined by the sliding link. It is thus possible to adjust the position in translation according to the axis defined by the sliding link of at least one out of the jaw portion or the teeth replica.
According to another preferred example, the positioning member includes a groove configured to interact with the complementary positioning member.
According to another preferred example, the complementary positioning member includes a tab configured to interact with the positioning member.
The groove can have a polygonal cross-section and be configured to form a female portion of a dovetail assembly by interaction with the complementary positioning member.
Likewise, the tab can have a cross-section configured to form a male portion of the dovetail assembly by interaction with the positioning member. The tab has for example a polygonal cross-section.
According to an option of interest, the complementary positioning member further includes an axial stop.
For example, this axial stop can allow a stopping in translation of the jaw portion or of the teeth replica when the positioning member interacts with the complementary positioning member according to the sliding link. Thus, the axial stop forms a reference for positioning the jaw portion and/or the teeth replica with respect to the shell. Indeed, it is possible to immobilise the jaw portion and/or the teeth replica in a predetermined position by sliding it along the axis defined by the sliding link until the axial stop.
Thus the positioning of the jaw portion on the shell is carried out easily and quickly by a prosthetist or any other practitioner, by translating the jaw portion until the stop. Moreover, it is thus possible to identically position the teeth replica on the shell by doing the same.
In exemplary the of an embodiment, step manufacturing the teeth replica is preceded by a step of parallelisation of the teeth replica model, in which undercut zones of the teeth replica model are filled in digitally.
These undercut zones are typically located at the junction between the teeth and the gums.
In the methods of the prior art, it was necessary to manually fill in these undercut zones with wax.
Consequently, the creation step is configured to minimise, or even eliminate, the undercut zones of the teeth replica model.
Thus, this step, carried out digitally, then allows to manufacture the teeth replica in which the “parallelised” zones are formed in a single piece with the teeth replica.
This is particularly advantageous during the step of creating the imprint in order to remove the jaw portion from the mould without damaging the imprint.
Moreover, the undercut zones are possibly filled in according to an axis of insertion determined digitally. The axis of insertion corresponds to the direction according to which the prosthesis will be inserted into the mouth of the patient. The axis of insertion is generally determined by the practitioner, or by a piece of software.
According to a specific exemplary embodiment, the step of positioning the imprint on the teeth replica is preceded by a step of positioning a stellite chassis on the teeth replica.
A stellite chassis is particularly useful in the case of a partial prosthesis, typically to maintain together two separate parts of the prosthesis.
Advantageously, the stellite chassis is rigidly connected to the dental prosthesis after the casting of the filling material.
Putting the stellite chassis in place is thus easy and quick for a practitioner and guarantees an optimal adaptation to the environment in which it is intended to be positioned.
According to another exemplary embodiment, the method further includes a step of piercing a supply channel opening into the imprint.
This supply channel is used thereafter for the casting of the filling material to create the dental prosthesis. In an example of interest, at least two channels are pierced in order to simultaneously allow the casting of the filling material and the evacuation of air present in the imprint.
According to an exemplary embodiment, the step of manufacturing the jaw portion and/or the teeth replica is carried out by additive manufacturing.
According to the invention, “additive manufacturing” designates a manufacturing method of adding material, most of the time assisted by computer, more commonly called “3D Printing”. The techniques of additive manufacturing allow for example a more precise manufacturing of the jaw portion.
Thus, it is possible to abstain from the manual manufacturing of a model made of wax.
Moreover, via the precision of the additive manufacturing, it can be possible to eliminate the need for a polishing step which is often time-consuming and costly and capable of damaging the part.
Thus, at least in certain cases, a dental prosthesis to be made can exit directly ready for the use of such a method, or with only a minimum of post-treatment steps, for example to obtain a polished-mirror appearance on some surfaces of the dental prosthesis.
According to an exemplary embodiment, the step of manufacturing the jaw portion and/or the teeth replica is carried out according to a method comprising a succession of additions of material by jets on a printing support, in successive layers, the material being solidified by photopolymerisation after each jet.
For example the jaw portion can be manufactured from a monomer, a polymer or a photopolymerisable resin. Preferably, the jaw portion is manufactured from PA 12 (for polyamide 12, also called Nylon 12).
Indeed, PA 12 has capabilities of interest of recycling the non-melted powder after the implementation of the additive manufacturing method as described here, and thus allows to reuse this powder in order to create other prostheses or even other products.
According to another aspect, a shell mould for manufacturing a dental prosthesis is also proposed.
According to the invention, the shell mould includes a complementary positioning member configured to interact with a positioning member of an insert to be positioned in the shell mould.
Such a mould is thus in particular configured to implement a method as described above.
In the context of the invention, a “shell mould” designates a mould formed by at least two portions interacting with each other, each portion thus being called “shell”.
An insert corresponds here to any part allowing to implement at least some of the steps of taking an imprint, moulding or overmoulding with a view to creating a dental prosthesis. For example, according to the invention, the insert can be a replica of a patient's teeth or a jaw portion.
Such a shell mould thus has advantages analogous to those described above in relation to the method.
According to one embodiment, the complementary positioning member is configured to form a sliding link with the positioning member of the insert.
In particular, the complementary positioning member is for example configured to form a male part of the dovetail assembly.
According to one embodiment, the complementary positioning member includes a tab configured to interact with the positioning member.
According to a complementary embodiment, the complementary positioning member includes an axial stop to block the movement in translation of the positioning member when it interacts with the complementary positioning member.
In particular, the axial stop can be formed by a protruding surface, protruding transversely to the longitudinal direction of the tab acting as a guide in translation, for example perpendicularly on either side of the tab, so that the complementary positioning member has the shape of a T.
The invention, according to an exemplary embodiment, will be well understood and its advantages will be clearer upon reading the following detailed description, given for informational and in no way limiting purposes, in reference to the appended drawings in which:
The identical elements shown in the aforementioned drawings are identified by identical numerical references.
Such a model is for example obtained via a step of taking a digital imprint (not illustrated) carried out on a model made of plaster via a table scanner or, preferably, directly via an intraoral scanner in the mouth of the patient.
The teeth replica model 1 thus corresponds to a digital representation of a portion of the jaw of a patient, in this case a lower jaw portion, for which a dental prosthesis must be made.
This teeth replica model 1 is generally stored in a file in the STL format and displayed using a piece of computer-aided design software.
The teeth replica model 1 includes for example an “upper” portion mainly forming a teeth portion, and a “lower” portion mainly forming a gums portion.
The teeth replica model 1 further includes a rear portion, or lingual portion, representing a concave inner face.
In the example illustrated, the teeth replica model 1 includes, in the upper portion, at least one missing tooth 3.
Moreover, in the example illustrated, the teeth replica model 1 includes at least one remaining tooth 5. The dental prosthesis to be made is in this case a partial dental prosthesis.
Of course, the present invention is not limited to this type of dental prosthesis and also applies to other types of prostheses, for example, to a complete dental prosthesis, that is to say for which the teeth replica model does not include any tooth 5.
As illustrated in
The teeth replica model 1 further includes in the lower portion a lower surface 7.
This surface, once the teeth replica model 1 has been manufactured, is configured to position it in a stable manner on a support.
The lower surface 7 of the lower portion of the teeth replica model 1 defines for example a plane.
In the example shown, the positioning member model 8 includes a groove 8a. The groove 8a is configured to form a sliding link with a complementary member.
Indeed, the groove 8a extends according to a longitudinal axis between the rear portion and the front portion of the teeth replica model 1. The groove 8a has here a trapezoidal cross-section that allows, by interaction with a complementary member, only the movement according to a longitudinal axis of the groove 8a.
In the example shown in
The dental prosthesis model 4 is designed digitally on the basis of the teeth replica model 1. A profile and a shape of the prosthesis model are determined according to the teeth replica model 1 in order to best adapt to it. The profile of the dental prosthesis model 4 is also determined according to an axis of insertion, that is to say the trajectory for inserting the dental prosthesis model by simulation into the mouth of the patient. This axis of insertion is for example determined by the prosthetist or by the software.
Therefore, the dental prosthesis model 4 typically includes at least one tooth, and optionally a gum portion according to the teeth replica model 1, so as to form a jaw portion model 2 with corrected and complete teeth.
In the case of a partial dental prosthesis, the dental prosthesis model 4 can include a stellite chassis model (not t shown) configured to bear on at least one remaining tooth 5 and/or on a mucosa, in particular the gums, and/or to maintain together at least two separate parts of the dental prosthesis model.
It is understood that a lower portion of the jaw portion model 2 corresponds entirely to the lower portion of the teeth replica model 1. Indeed, only the hatched portion shown on the jaw portion model 2 differs from the teeth replica model 1. Thus, the jaw portion model 2 also includes the lower surface 7 at its lower portion. Consequently, the jaw portion model 2 also comprises the positioning member model 8, including here the groove 8a and the stop 8b, identical to the positioning member of the teeth replica model 1.
For this, the shell 32 and the complementary shell 34 respectively include a notch 33a and a hook 33b. The hook 33b is configured to interact with the notch 33a to maintain the shell mould 30 closed. Of course, any other means for closing the shell mould 30 is possible, for example such as rubber bands.
The shell 32 has a bottom 35. The bottom 35 defines here a flat surface. The flat surface formed by the bottom 35 is intended to receive the jaw portion 20 on its lower surface 7 side.
According to the example shown, casting holes 38 are arranged in the complementary shell 34 in order to fill the shell mould 30 with a material with a view to the creation of an imprint of an insert.
The material for creating the imprint is a hydrocolloidal gel.
Such a shell mould 30 forms for example a dental flask.
The jaw portion 20 is for example made by additive manufacturing. For example, the jaw portion 20 is made from PA 12, or from photopolymerisable resin. In the exemplary embodiment described here, the jaw portion 20 is manufactured in a single piece.
The step of manufacturing the jaw portion 20 can further include, for example, a finishing substep. However, the parts made by additive manufacturing generally only require very few, or no, finishing touches; such a finishing step is therefore optional.
According to an aspect of interest of the invention, the shell 32 includes a complementary positioning member 36.
The complementary positioning member 36 of the shell 32 is configured to interact with a positioning member arranged in an insert, the overmoulding of which is to be carried out, in particular to form a sliding link. In the exemplary embodiment shown, the complementary positioning member 36 forms the male portion of a dovetail assembly.
In the present exemplary embodiment, the complementary positioning member 36 comprises an axial stop 36b to stop the movement in translation of the jaw portion 20 during the interaction of the complementary positioning member 36 with the positioning member 28. In general in the present description, an “insert” thus designates an object intended to be inserted into a mould to be overmoulded.
In the context of the present example, the insert in question is therefore the jaw portion 20.
As shown by
The complementary positioning member 36 of the shell 32 is therefore configured to interact with the positioning member 28 of the jaw portion 20.
The complementary positioning member 36 is located on the bottom 35 of the shell 32. In particular, the complementary positioning member 36 protrudes from the bottom 35 of the shell 32.
According to the example shown, the complementary positioning member 36 comprises here a tab 36a, which has a shape complementary to that of the groove 28a. The tab 36a has for example a cross-section complementary to the cross-section of the groove 28a.
The tab 36a protrudes from the bottom 35 of the shell 32. The tab extends longitudinally according to the axis G shown in
Thus, during the interaction the between positioning member 28 and the complementary positioning member 36, the jaw portion 20 is moved parallel to the flat surface of the bottom 35 of the shell 32.
In the exemplary embodiment shown, the groove 28a forms the female portion of a dovetail assembly. The groove 28a includes for example a polygonal, and more precisely trapezoidal, cross-section. In the exemplary embodiment shown, the tab 36a forms the male portion of a dovetail assembly.
The dovetail assembly is used here to prevent the movement of the jaw portion 20 in an out-of-plane direction, for example orthogonal to the flat surface of the bottom 35 of the shell 32, and to maintain in position the jaw portion 20 for example during the separation of the complementary shell 34 and the shell 32 after a step of creating an imprint described more in details below.
Of course, the groove 28a of the positioning member 28 and/or the tab 36a of the complementary positioning member 36 according to the invention can have any other shape as long as they allow an interaction according to a sliding link. Thus, in an embodiment not shown, the positioning member 28 includes a tab protruding with respect to the lower surface of the jaw portion and the complementary positioning member includes a groove having a cross-section complementary to the tab of the positioning member. According to the example shown, the axial stop 36b is configured to interact with the positioning member 28 and more particularly with the front portion of the jaw portion 20, optionally with the stop 28b of the positioning member 28. This axial stop 36b also forms a reference for positioning of the jaw portion 20 on the shell 32.
The axial stop 36b is formed by a protruding surface, extending perpendicularly on either side of the tab 36a, so that the complementary positioning member 36 has the shape of a T. The axial stop 36b is for example located at an end of the tab 36a so as to be able to visualise the bearing in abutment with an insert, such as the jaw portion 20 and in this case with the stop 28b of the positioning member 28.
Of course, the axial stop 36b of the complementary positioning member 36 is not limited to the example shown and can be formed by any other means allowing to stop the movement in translation of an insert. In an embodiment not shown, the groove 28a formed by the positioning member 28 does not pass all the way through and is stopped by a longitudinal end of the tab 36a.
According to the example shown, the imprint 39 is formed from the material introduced by the casting holes 38. Thus, in the present example, the imprint 39 is integrally comprised in the complementary shell 34 of the shell mould 30.
As illustrated also in
Thus, such a method allows to create an imprint with a view to creating a custom dental prosthesis by moulding.
For example here, several artificial teeth 42 are positioned in the imprint 39. These teeth are intended to fill in the missing teeth, shown in the teeth replica model 1. Consequently, such artificial teeth 42 are positioned in the imprint 39, at the locations corresponding to the teeth previously designed by the software, as shown with hatching in
For example, the teeth replica 10 is made by additive manufacturing, on the basis of the teeth replica model 1, in a manner analogous to the creation of the jaw portion 20.
The teeth replica 10 consequently includes a positioning member 18, identical to the positioning member 28 of the jaw portion 20.
In this case, the positioning member 18 includes here a groove 18a. According to the example shown, the positioning member 18 also includes a stop 18b formed by the front face of the jaw portion 20.
The complementary positioning member 36 of the shell 32 is thus configured to interact with the positioning member 18 of the teeth replica 10. In this way, the teeth replica 10 is positioned on the shell 32 in a similar, or even identical, way to the jaw portion 20. In particular, the complementary positioning member 36 is configured to form a sliding link, and more particularly a dovetail assembly, with the positioning member 18.
The sliding link allows here a movement in translation of the teeth replica 10 according to the longitudinal axis G of the tab 36a, that is to say parallel to the flat surface of the bottom 35 of the shell 32.
The dovetail assembly is used to prevent the movement of the teeth replica 10 in a direction perpendicular to the flat surface of the bottom 35 of the shell 32, and to maintain in position the teeth replica 10 for example during the separation of the complementary shell 34 and of the shell 32 after a step of casting of a filling material described in more detail below.
The teeth replica 10 forms a sealed link with the imprint 39. This is explained in particular by the fact that the lower portion of the jaw portion 20 is identical to that of the teeth replica 10.
However, since their upper portion is different, the teeth replica 10 only partly fills the imprint 39, so as to form a residual volume in the imprint 39. This residual volume is both defined and delimited by the imprint 39, the artificial teeth 42 and the teeth replica 10.
In the case of a partial dental prosthesis, this volume is further defined by the stellite chassis 44 (
During this step, the filling material 46 comes in contact with at least a portion of the artificial teeth 42 to bond thereto, for example, by overmoulding. The same applies for the stellite chassis 44 in the case of a partial prosthesis.
The filling material 46 can be injected under pressure or by natural gravitational filling, so as to best adjust to the walls of the residual volume. The filling material 46 can comprise any type of material known for the manufacturing of a dental prosthesis, such as an acrylic resin for example.
The method further includes a step of separating the teeth replica 10 and the imprint 39, or even for example of opening the shell mould 30, then a step of extracting (not illustrated) an unsurfaced blank configured to form the dental prosthesis.
The method also includes for example a finishing step which can include a step of eliminating an injection sprue corresponding to the moulding of the supply channel, and/or a finishing step involving for example a polishing and/or a deburring and/or a buffing of the unsurfaced blank.
In the present exemplary embodiment, the dental prosthesis 40 is a partial dental prosthesis. Indeed, the stellite chassis 44 connects two portions each including at least one artificial tooth 42 bonded to the solidified filling material 46.
Adjustment steps can be carried out by positioning the dental prosthesis 40 on the teeth replica 10, before being inserted into the mouth of the patient.
According to this example, the method includes:
| Number | Date | Country | Kind |
|---|---|---|---|
| 2103049 | Mar 2021 | FR | national |
This application is the US national stage of PCT/FR2022/050551, filed Mar. 24, 2022 and designating the United States, which claims the priority of FR 2103049, filed Mar. 25, 2021. The entire contents of each foregoing application are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2022/050551 | 3/24/2022 | WO |
