WO2025103994A1 - 3d printing of a unitary piece in a metal material - Google Patents

Abstract

The present invention relates to a dental or surgical handpiece (1) formed by a head (10) and a gripping handle (11), each provided with at least one integrated internal duct (2) selected from a pneumatic duct (20), a light transmission duct (23), and a blind duct (24) suitable for housing one or more electronic sensors (5), characterised in that at least one element selected from an internal shell (111) of the handle (11) and the head (11) is made by 3D printing in metal and contains the pneumatic duct (20) and/or the light transmission duct (23) and/or the blind duct (24) as an integrated internal duct (2) in a single unit.

Description

3D printing in a metallic material of a single piece

Technical field of the invention

The present invention relates to a dental device (i.e. a turbine, a contra-angle or a straight handpiece) made in a single piece with integrated conduits.

State of the art

Dental devices are generally equipped with internal sprays or conduits for irrigation with physiological liquid, allowing to cool the working area, that is to say the region of the tooth subjected to the action of the cutting, milling or prophylaxis/cleaning tool. In addition, they are often additionally equipped with one or more internal conduits intended to allow the insertion, guidance and/or positioning of a rigid optical fiber or a glass rod allowing the transmission of light to the head of the device near the positioning area of the cutting tool. Since a rigid optical fiber or a glass rod with one or more bends cannot be introduced into a conduit, these conduits for optical fiber or glass rods are necessarily formed of different segments, not extending over the entire length of the optical fiber or glass rod provided inside the dental device, but only along portions corresponding to each segment.

The spray or internal irrigation lines and the light transmission lines are assembled into the device casing by manual insertion and fixed integrally to the casing by driving or gluing. Since the device generally consists of at least two casing parts fixed together, typically a head and a handle (gripping part) and often a rear cap, the lines must be correctly positioned relative to all these components during assembly and, during the life cycle of the device, they are subjected to mechanical forces generated by the reciprocal movement of these components. of the external carcass (which are glued, driven or screwed together but which maintain a small freedom of vibration in torsion and/or traction.

Such traditional devices, where the spray/irrigation lines and the light line are assembled after machining or molding the device frame, have several disadvantages.

First, the pipes must be manufactured in advance, which requires one or more machining and degreasing steps, and then assembled manually because robotic assembly is made impossible by the curved shape of the pipes and the casing. The assembly time and manufacturing costs are therefore high.

Second, since the lines must be fixed by driving or gluing, their resistance during aging (which also involves disinfection, washing and autoclave sterilization cycles) and in the event of the device being dropped is unreliable. The rupture of a spray line during clinical treatment is dangerous because it causes liquid leaks outside the device which can lead to short circuits with other electrified devices located nearby in the dental office, as well as potentially immediate heating of the milling tool, which can cause burns to the patient.

Furthermore, the tube manufacturing and assembly stages require the use of chemical additives (lubricating oils for machining, degreasers, glues), which have an impact on the biocompatibility profile of spray lines, as residues are potentially absorbed by the patient. In addition, the toxicological profile of the products used is not necessarily known or it may change over time with the increase in clinical studies and knowledge.

In the case of a turbine air injector, manual positioning is otherwise often complex and incorrect positioning impacts significantly negatively affect the device's performance in terms of torque and speed.

A mixed spray is generally obtained using an air/water mixer, commonly called the diffuser, which is placed in the head of the device and fixed by driving, welding or gluing. The good quality of air-water mixed sprays therefore depends heavily on the geometric tolerances of the tubes and the diffuser as well as the correct positioning of the tubes and the diffuser during assembly. However, since the production dispersion is very important, it is mandatory to systematically carry out a final quality control of the sprays before the release of each device produced, which further prolongs the production lead time and, ultimately, costs.

Finally, the assembly of the light conductor, most often consisting of a rigid optical fiber or a glass rod, is complex, and it can often cause the fiber to break, which prolongs the average manufacturing time and therefore costs.

For all these reasons, we have sought to obtain solutions producing "monobloc" devices, i.e. made from a single piece. The reference technology for achieving this result is the molding or overmolding with plastic materials of the handpiece frame, as described for example in the European patent application EP0937440A2. A disadvantage of this simplified manufacturing method is that if the spray pipes are integrated into the monobloc part during a molding phase, then they must also be made of plastic. Furthermore, the possibilities in terms of geometric shapes for the pipes remain limited.

Otherwise, devices such as those disclosed in US patent US6186784B1 are known which have a removable and replaceable cartridge, intended to be fixed to the head of the dental device and which integrates, as a single-piece module, the spray lines. The geometry of this cartridge is however necessarily relatively simple to allow the machining of the lines through holes. Furthermore, these The lines, once the cartridge is inserted, must logically be aligned with the lines inserted into the handle of the device to perform the function of bringing the spray along the handpiece to the head of the device, which refers to the problems mentioned previously in terms of assembly.

French patent application FR2864442A1 discloses a handpiece with a single-piece frame, inside which the transmission kinematic chain must be assembled. However, this solution also does not solve the aforementioned problems in terms of formation, and in particular the areas where the pipes join.

US application 20170042639 A1 also describes a 3D printing technique using composite stereolithography to produce certain components of a handpiece, intended to be subsequently assembled to the handle of the latter. This solution still does not solve the aforementioned problems at the level of the internal pipe joining areas.

There is therefore a need for a dental device solution free from these known limitations.

Summary of the invention

An object of the present invention is to provide a dental device which can be more easily produced compared to prior art solutions.

These aims are achieved thanks to the characteristics of the main claim, and in particular thanks to a dental or surgical handpiece formed of a head and a gripping handle each provided respectively with at least one integrated internal pipe chosen from a pneumatic pipe, a light transmission pipe, and a blind pipe adapted for housing one or more electronic sensors, characterized in that at least one element chosen from a internal carcass of the handle and the head is made by metal printing and comprises said pneumatic pipe and/or said light transmission pipe and/or said blind pipe as an internal pipe integrated in a single piece. An advantage of the proposed solution is to simplify the assembly operations, and to substantially increase the reliability of the dental devices thus formed.

Another advantage of the proposed solution is that it provides improved flexibility in terms of design and geometric shapes to be achieved both for fluid-related pipes and for pipes intended for light transmission.

According to a preferred embodiment, the dental or surgical handpiece according to the invention is produced from end to end, from the handle to the head, by 3D printing and comprises at least one air spray channel and one water spray channel as pneumatic conduits, each of the pneumatic conduits being devoid of angular parts.

In this way, not only are time savings achieved in producing the entire dental or surgical handpiece in one go, thus considerably simplifying the manufacturing process and assembly constraints, but also considerably improving the quality of the resulting part, whose spray channels can not only be positioned in an optimized way inside the carcass, but whose shape is also optimized with simply curvatures instead of angular parts marking connections between machining or drilling segments. In this way, fluid flows are improved and the cleaning process is further facilitated.

According to an even more preferred embodiment, the dental or surgical handpiece according to the invention is characterized in that it comprises a diffuser integrated in the head which is formed of an upper ring for conveying air, a lower ring for conveying water, and a plurality of transverse outlet channels connecting the ring in parallel upper than the lower ring, the diffuser being directly connected to the air spray channel and the water spray channel.

Thus, it is possible to further optimize the quality of air-water mixed sprays, by producing in a single 3D printed part all the air and water pipes and simultaneously the mixer/diffuser, the latter also being single-piece with the head of the device. This makes it possible to produce a part containing pipes that are mostly circular, and in any case annular in shape, which are very difficult to obtain by molding, and to simultaneously eliminate the step of positioning and driving or welding the diffuser into the head.

According to an even more preferred embodiment, the dental or surgical handpiece according to the invention is characterized in that the integrated internal pipeline comprises at least one bifurcation.

Such a configuration is particularly difficult to obtain by machining or molding and thus allows the desired geometric shapes to be further optimized and the performance of the handpiece produced to be improved while reducing costs.

According to an even more preferred embodiment, the dental or surgical handpiece according to the invention is characterized in that the integrated internal pipe has a first double bifurcation of an air spray channel and/or a second double bifurcation of a water spray channel.

Such a configuration, which is almost impossible to obtain other than via 3D printing, makes it possible to maximize the diffuser's performance in terms of mixing quality thanks to fluid flow minimizing turbulence and guaranteeing better distribution of the pressure of each of the fluids.

According to another preferred embodiment, the dental or surgical handpiece according to the invention is characterized in that the Integrated internal channeling has a third bifurcation of a light transmission conduit followed by two domed end portions in the head.

This configuration for light pipes is doubly advantageous, on the one hand from a reliability point of view in the event of a fall or mechanical shock thanks to the absence of pinching, which also reduces the risk of breakage during assembly. Furthermore, as many light sources as there are branches can be removed, which reduces manufacturing costs accordingly.

According to yet another preferred embodiment for the dental or surgical handpiece, at least one pneumatic conduit has an elliptical section.

Such a configuration makes it possible to reduce the size of the pipes within the dental or surgical handpiece produced, and thus to be able to either minimize the total dimensions of the part, or to have other parts or pipes - in particular for sensors - or even, in the case of a contra-angle, to increase the size of the transmission gear, for the sake of reliability.

According to yet another preferred embodiment for the dental or surgical handpiece, at least one light transmission pipe has a hexagonal section.

Such a configuration makes it possible to minimize the contact points of a glass rod or an optical fiber with the integrated internal channel, and thus allow easier insertion of the light transmission element by minimizing friction, and at the same time reducing any risk of breakage of the latter.

According to yet another preferred embodiment for the dental or surgical handpiece, at least one light transmission pipe has a variable section following a wavy profile. Such a configuration also makes it possible to minimize the contact points of a glass rod or an optical fiber, and thus allow them to be inserted more easily by minimizing friction, and at the same time reducing any risk of them breaking.

According to yet another preferred embodiment for the dental or surgical handpiece according to the invention, the latter comprises a helical-shaped pneumatic cooling pipe.

Such a configuration, which is particularly difficult to achieve by molding or machining, is particularly suitable for motorized oral surgery devices, which cannot be cooled via any compressed air flow due to the risk of embolism.

According to yet another preferred embodiment for the dental or surgical handpiece according to the invention, the 3D printing process determines a surface roughness state on an external surface of an external cap of the gripping handle giving it anti-slip properties.

In this way, manufacturing costs can be further reduced by eliminating the need for a subsequent treatment step on the exterior of the handpiece or the addition of an additional coating around the grip handle.

According to yet another preferred embodiment for the dental or surgical handpiece according to the invention, the latter is characterized in that the micro-hardness of the outer surfaces of the carcass of the handpiece or of an outer cap of the gripping handle is at least 20% higher than the hardness of the inner surfaces following a heat treatment of metal powders prior to the 3D printing step, and a subsequent treatment by pulsed-plasma of said outer surfaces.

Such a configuration allows to have a sufficiently high hardness on the outside to resist aging phenomena (for example against scratches) and shocks and, at the same time, to preserve a sufficiently low hardness level for internal surfaces that are machined, such as typically a turning or grinding operation to further reduce tolerances for the internal surfaces of the turbine head, the positioning of O-ring seals for rotor positioning, etc.

According to yet another preferred embodiment for the dental or surgical handpiece according to the invention, the latter comprises at least one blind conduit adapted for housing one or more electronic sensors, the blind conduit comprising an open end at the grip handle, and being closed at the head by a housing.

Such a configuration with closed or plugged pipes at the head - hence the terminology of "blind" pipe by analogy with a blind hole - is very difficult or even impossible to obtain with other methods, and it makes it possible to intrinsically ensure the sealing of the terminal housing where electronic sensors are arranged, such as thermal sensors or accelerometers to capture a vibration level, and which would otherwise be subjected to a very aggressive external environment due to the presence of water, saliva, blood, organic and non-organic debris.

According to a variant for the dental or surgical handpiece according to the invention, the latter is characterized in that it comprises a mixer for a mixed spray channel arranged in the internal carcass of the gripping handle.

Such a variant makes it possible to offer a simple and effective alternative to a diffuser usually housed in the head of the tool, which is more likely to be damaged, for example, if the tool is dropped, and which sets an additional constraint on the minimum dimensions of the head of the device. Such a variant therefore makes it possible to reduce the dimensions of the head of the device and therefore to facilitate access to the patient's mouth. The present invention also relates to a preferred 3D printing method for producing a dental or surgical handpiece according to one of the preceding claims 1 to 14, characterized by a growth direction going from said gripping handle towards said head, the microscopic growth layers being superimposed according to printing planes perpendicular to said growth direction and oriented at an angle of between 10° and 20° relative to the transverse plane of the gripping handle.

Such a preferential choice for the growth direction of the 3D printing method with a slight offset from the axis of the grip handle makes it possible to optimize the geometric shapes to be produced, in particular the curvatures to be produced according to particular orientations with respect to the frontal plane and the sagittal plane of the handpiece to be produced.

Brief description of the drawings

The present invention will be better understood from reading the following description, given by way of example and with reference to the drawings in which:

- Figure 1A is a side view of a single-unit turbine made according to a preferred embodiment for the present invention, schematically representing the integrated internal pipes for air, water and light;

- Figure 1 B is a three-dimensional view of the head of a turbine such as that produced in Figure 1A, schematically showing the detail of a diffuser as well as a triple bifurcation for the arrival of air in the head;

- figure 1 C is a sagittal sectional view along plane AA shown in figure 1A showing the detail of the diffuser of the single-block turbine obtained according to the preferred embodiment of figures 1 A and 1 B above; - Figures 2A and 2B highlight the difference between an optical channel produced by 3D printing and by machining, Figure 2A illustrating a channel produced by machining having an angular part at its end, while the other channel, illustrated in Figure 2B and produced by 3D printing, has a rounded profile.

- Figure 3A is a side view of the exterior of a turbine according to another preferred embodiment;

- Figure 3B is a sectional view of the turbine of Figure 3A at the end of the handle along the section plane C-C illustrated in Figure 2A;

- Figure 3C is a sectional view of the head of the turbine of Figure 3A along the section plane F-F illustrated in Figure 3A;

- Figure 4 illustrates a three-dimensional view of a turbine produced in a single block according to another preferred embodiment for the invention, schematically highlighting a light transmission conduit branching off at the head of the turbine;

- Figure 5A illustrates a three-dimensional view of another turbine produced in a single block according to yet another preferred embodiment for the invention, schematically highlighting a particular form of a light transmission conduit;

- Figure 5B illustrates the particular section of a light transmission conduit for a turbine produced according to the preferred embodiment of Figure 5A;

- Figure 6 illustrates a three-dimensional view of yet another handpiece made in a single piece according to yet another preferred embodiment for the invention, provided with an integrated helical fluid channel; - Figures 7A, 7B and 7C illustrate respectively a side, front and three-dimensional view of a single-piece turbine, highlighting the vertical growth direction of the 3D printing process;

- Figure 8A is a schematic sectional view of a handpiece produced according to a preferred embodiment of the invention and which contains a conduit intended for housing one or more sensors;

- Figure 8B illustrates the detail of the head of a handpiece of Figure 8A, containing two housings into which a thermocouple and a piezoelectric acceleration sensor are respectively introduced;

- figure 9 is a schematic sectional view of a handpiece produced according to a preferred variant for implementing the invention, according to which a mixer is provided in the grip handle instead of a diffuser in the head

Detailed description

In the following, a preferred embodiment of the present invention will be described for the production of integrated internal pipes 2 of a handpiece 1 in the form of a turbine, shown schematically in the series of figures 1A-1B and 1C, then the details of the pneumatic pipes are then illustrated in the series of figures 3A, 3B, and 3C.

Figure 1A is a side view of a turbine made in a single piece from the gripping handle 11 to the head 10, schematically representing integrated internal pipes 2 for air, water and light; it will however be understood from the following that it will be possible to produce any type or any subset of these integrated internal pipes without departing from the scope of the present invention.

As illustrated in Figure 1A, the integrated internal pipes 2 comprise pneumatic conduits 20, provided for circulating fluids such as air or water. According to the embodiment shown in this figure, the pneumatic lines 20 thus comprise an air spray channel 21 and a water spray channel 22, which respectively comprise a first bent portion 21C and a second bent portion 22C, while the light transmission line 23 comprises a third bent portion 23C a little further oriented in the other direction, that is to say downwards so that the light source 4 can illuminate the working area of the handpiece 1 just under the head 10. The air spray channel 21 and the water spray channel 22 are routed to a diffuser 25 integrated in the head 10 and the detail of which is illustrated in figures 1B and 1C described below. However, seen from the external cap 110 of the grip handle, the way in which the various integrated lines are made is undetectable for the user.

Figure 1 B illustrates a three-dimensional view of the head 10 of the turbine with respectively the arrivals of the two spray channels, towards diffusion rings, and in particular an upper ring 251 connected to the air spray channel 21 and a lower ring 252 connected to the water spray channel 22; the upper ring 251 and the lower ring 252 being connected to each other via transverse outlet channels 253, clearly visible in Figure 1 C which is a sagittal sectional view along the plane A-A represented in Figure 1 A showing the structural detail of a single-piece turbine diffuser 25 obtained according to the preferred embodiment of the preceding Figures 1 A and 1 B.

The advantage of using 3D printing technology is that it is possible to produce here not only any shape for the diffusion rings (i.e. the upper ring 251 and the lower ring, having a circular shape in FIGS. 1 B and 1 C, but which can potentially take any shape required as needed, such as for example an elliptical shape in order to save space or to accommodate another element in the head. In FIG. 1 C, a particular shape of the diffusion rings can also be seen, with an “L”-shaped section for each of the rings; moreover, to improve the quality of the fluid flow, double bifurcations are made in each of the two pneumatic conduits 20, and in particular a first double bifurcation 210 of the air spray channel 21 and a second double bifurcation 220 of the water spray channel 22, clearly visible in FIG. 1 B. Such double bifurcations are almost impossible. to be obtained by molding and thus make it possible to improve the quality of the turbine in this specific case, but more generally of any handpiece produced according to the invention.

A great advantage of the handpieces made according to the invention is to avoid the formation of any angular part, which allows the improvement of the flow of fluids in the framework of pneumatic conduits 20, as illustrated in figure 1A where the air spray channels 21 and respectively water

22 only include bent parts, and no more straight segments obtained by machining assembled together. For the light transmission pipes 23, this property is particularly advantageous because it also prevents any damage or breakage of these pipes being made most of the time of glass or other materials likely to be brittle.

Figures 2A and 2B illustrate this fundamental difference between a prior art solution and the invention, where the light transmission line

23 has an angular part 23B with a pointed edge capable of pinching the glass fiber which would be inserted therein at the front of the gripping handle 11 (figure 2A) whereas the light transmission conduit 23 produced by 3D printing according to the invention no longer has any angular part, but on the contrary only a rectilinear then curved part, as illustrated in figure 2B where a third bent part 23C can be seen at the exit of the light transmission conduit 23 towards the front of the gripping handle 11. More generally, the fact of no longer having an angular part thus means no longer having only line or curved parts, and has advantages both in terms of fluid flow and reliability when it comes to light transmission conduits. Advantageously, the light transmission conduits 23 with a smooth surface, that is to say with a profile characterized by a continuous derivative, obtained via 3D printing, can be combined with the use of flexible optical fibers, characterized by multi-strands of vitreous fiber not secured to each other. This technical solution, which can be adapted to conduits having an accentuated curved shape, is mechanically fragile: the use of light conduits 23 obtained via 3D printing makes it possible to overcome this major drawback, by protecting these flexible fibers and avoiding their breakage during assembly and/or use of the device. The series of figures 3A-3B-3C show different views of a turbine produced according to another preferred embodiment for the present invention, the light pipes of which are not shown, but which highlights the way in which the different pneumatic pipes are produced thanks to sectional views according to different planes; figure 3B is in fact an enlarged view in projection according to the section of the turbine of figure 3A at the level of the end of the handle according to the sectional plane BB illustrated in figure 2A, and figure 3C is an enlarged view in projection according to the section of the head of the turbine of figure 3A according to the sectional plane CC illustrated in figure 3A, where the rotor has been removed for clarity of visualization.

The only notable difference between the elements represented between the preceding figure 1 A and figure 3A concerns, in addition to the visualization of the section planes B-B and C-C used for figures 3B and 3C described below, the fact that only the external parts of the head 10 and the gripping handle 11 are now visible, namely the external cap 110 thereof, which is here preferably provided with an external non-slip surface 110A which has a predefined surface roughness R obtained directly during the 3D printing process, and thus makes it possible to dispense with a subsequent surface treatment or a step of covering with an additional coating for this purpose. In this way, the number of steps required during the manufacturing process is reduced and it is possible to gain in efficiency.

Figure 3B, which shows the detail of the pneumatic pipes 20 in the section plane BB, that is to say before bifurcation at the inlet of the head 10, makes it possible to visualize the injection channel of the turbine 200, having a circular section, while the air spray channels 21 and water 22 each have an elliptical section 20S, which makes it possible to save space in height. Such a shape is also more delicate, or even almost impossible to produce by molding, and in particular for metallic materials, which will be favored in the context of the invention. According to the preferred embodiment illustrated in this figure, the minimum length of the pipes in the form of tubes is preferably greater than 20 mm, and the wall thickness range of these tubular pipes is between 0.2 mm and 2 mm. Figure 3C shows the detail of these same pneumatic conduits, but after a double bifurcation of the air spray 21 and water 22 channels, such as the first double bifurcation of the air spray channel 210 and the second double bifurcation of the water spray channel 220 shown diagrammatically in the previous figure 1B: This is the reason why, in this figure, we can distinguish three channels of elliptical section corresponding to the water spray channels 22 at the bottom of the head and, in a superimposed plane just above, three air spray channels 21, also of elliptical section. Just above the injection channel of the turbine, we can distinguish the injection channel of the turbine, still of circular section, and all of the pneumatic conduits are well integrated into the internal carcass of the head 111. According to the preferred embodiment illustrated here, the entire handpiece 1 is produced in a single piece, and in particular the head 10, the gripping handle 11 and the external cap 110 thereof; but according to an alternative embodiment, it would however be possible to produce only the internal carcass 111 provided with all of the integrated internal pipes 2 - not referenced in FIGS. 3B and 3C - including the pneumatic conduits 20, but to produce the casing of the handpiece 1, including in particular the external cap 110 in a separate manner for greater modularity and flexibility.

The turbine produced according to the preferred embodiment illustrated in Figures 3A-3C is thus provided with a spray of better quality than that which would have been obtained using an air/water mixer (via the diffuser 25) positioned in the head of the device and then fixed by driving, welding or gluing. Indeed, the good quality of the air-water mixed sprays then depends heavily on the geometric tolerances of the tubes and the diffuser as well as the correct positioning of the tubes and the diffuser during assembly. Since the production dispersion is very significant, it is therefore mandatory to systematically carry out a final quality control of the sprays before the release of each device produced, which prolongs the passage time and costs. Similarly, for the air injection of a turbine - via the air injection channel of the turbine 200, below also commonly referred to as an injector - manual positioning is often complex and incorrect positioning has a very strong negative impact on the performance of the device, i.e. in terms of torque and rotational speed provided. The turbine according to the invention makes it possible to overcome these drawbacks.

Figure 4 illustrates a three-dimensional view of a turbine produced in a single piece according to another preferred embodiment for the invention, schematically highlighting a light transmission conduit 23 bifurcated at the head 10 of the turbine 1, unlike that of Figure 1A which only comprises a bent part 23C at the end of the handle 11 just before the head 10. This figure thus highlights a third bifurcation 230 of the light transmission channel 23, which unlike the first and second previous bifurcations relating to the spray channels, is a simple bifurcation, that is to say transforming a channel into two sub-channels downstream, and not three as illustrated in particular in Figures 1B and 3C (the referencing diagram consisting of adding a suffix “0” for the bifurcations relative to the integrated internal pipes concerned, i.e. respectively 210 for the first, double bifurcation, of the spray channel air 21, 220 for the second bifurcation, also double, of the water spray channel 22 and finally 230 for the third bifurcation, here simple, of the light transmission pipe 23). The light transmission pipe 23 ends here with two curved end parts 230B oriented downwards, that is to say towards the work area. Such a configuration makes it possible to do without additional dedicated light sources and one could imagine, in a variant, making as many bifurcations as necessary while using only a single light source, and this makes it possible to reduce both manufacturing costs and reduce the assembly time for the handpiece to be produced.

According to a preferred embodiment, an LED module could be located at one of the two ends of one of the pipes corresponding to one of the light transmission pipes 23. Optimally, the LED module could be located at the front end of this pipe, that is to say rather towards the head 10 of the handpiece, and electrical wires housed all along this pipe. Figures 5A and 5B respectively illustrate a three-dimensional view and a sectional view of a light transmission pipe of another turbine produced in a single piece according to yet another preferred embodiment for the invention, schematically highlighting respectively a particular shape of a light transmission pipe, on the one hand, and on the other hand a particular section of such a light transmission pipe.

Indeed, as can be seen in view 5A when viewing the undulating profile 23A shown in dotted lines inside the gripping handle 11, and thus a priori hidden under the external cap 110 when the handpiece 1 is observed from the outside, the longitudinal section of the light transmission conduit 23 is not constant, which makes it possible to minimize the points of contact between this integrated internal pipe and the optical fiber (or any other suitable material used for light transmission) in the longitudinal direction, the contact between the internal wall of the light transmission conduit 23 and the fiber or for example a glass bar being only sporadic and not entirely continuous. Similarly, it can be seen that the profile of the section of the light transmission pipe is hexagonal - the hexagonal section being referenced 23S in this figure - which means that the number of radial contact points at each section is also limited to the maximum, here a point tangent to each side of the hexagon, or 6 in total. In this way, by reducing as much as possible the contact surfaces with the internal wall of the light transmission pipe 23, friction is also reduced, which makes it easier to introduce, or even possibly remove, the fiber if necessary, the corrugated part being free of angular parts avoiding any torsional stress likely to break it. Another advantage of this solution is the possibility of inserting a significant quantity of glue or other adhesive all along the pipe 23, the empty spaces between 2 contacts between the optical fiber and the pipe can be filled with the glue or adhesive, thus improving the mechanical attachment of the optical fiber to the device.

Figure 6 illustrates a three-dimensional view of yet another handpiece 1 made in a single piece according to yet another embodiment. preferred for the invention, provided with an integrated helical fluid pipe. Such a configuration with a pneumatic pipe 20 dedicated to the passage of water or physiological liquid is characterized by an axis which describes a helical shape 20H at the periphery of the handpiece, here represented in dotted lines in the gripping handle 11, but which does not extend into the head 10. Such a configuration aims to contribute to the cooling of the handpiece, which can be advantageous for motorized handpieces intended for oral surgery, which therefore cannot be cooled via a flow of compressed air due to risks of embolism. Here again, the particular geometry of the pneumatic pipe 20 would be almost impossible to produce by molding and consequently the production of such an internal pipe integrated directly into the internal carcass of a handpiece 1 is advantageously obtained via 3D printing.

According to the invention, the 3D printing process uses metals such as steel or titanium, unlike casting, whose technology is limited to certain specific, suitable polymers. Thus, the biological risks for the patient are now more limited, with a much lower probability of absorbing toxic substances released over time.

The use of metallic materials also has the advantage of being more robust with regard to cleaning, disinfection and sterilization cycles, a solution using plastic pipes being limited to single-use devices or having a very short service life (a few months of use at most).

Furthermore, polymers that would be used for spray lines cannot be cleaned and disinfected with the same level of efficiency as metals; for example, they are not resistant to all enzymatic and/or strongly alkaline products and/or certain alcohols, and can therefore constitute a support for microbial growth, causing a risk of cross-contamination for the patient.

The casting technology is also difficult to adapt to handpieces that can be used in combination with a motor because the introduction of a metal kinematic chain (the gears of dental devices are made of steel) inside a plastic casing and in proximity to plastic tubes is complex and can cause deterioration of the casing or internal pipes during the assembly process. For these reasons, it is once again advantageous to use a technology that minimizes the need for assembling different parts, and to work as much as possible only with metal, as proposed in the preferred 3D printing process according to the invention.

Finally, plastic materials have a modulus of elasticity (Young's modulus) lower than the modulus of elasticity of metals by a factor of more than two orders of magnitude: in fact, the Young's modulus of PEEK (standard thermoplastic polymer) is less than 4 GPa, while the Young's modulus of steel is approximately 200 GPa. Therefore, tubes made of plastic materials are subject to significant vibrations (in amplitude) even during normal operation (the flow of air and water passing through them activates vibrations according to the tubes' natural modes). The vibrations and noise generated are therefore significant and the risk of rupture is significant (the pipes must withstand pressures greater than 4 bars). The only possible solution when molding these parts of the dental device is to provide several support elements for the pipes to stiffen these intrinsically very flexible tubes as much as possible and minimize noise, vibrations and the risk of rupture. For turbines, pipe vibration can also affect performance by creating turbulence in the air exhaust. For all these reasons, the production of single-piece metal parts made by 3D printing presents many other advantages compared to the state of the art.

According to a particularly preferred embodiment, the grain size of the metal powder used in the 3D printing process is between 20 microns and 80 microns, and even more advantageously between 40 microns and 60 microns. Optimizing the grain size has two important technical advantages: minimizing the printing time and minimizing the roughness of the surfaces resulting from the printing, which avoids post-treatment of the surfaces with chemical substances. aggressive or micro-blasting techniques, these post-treatments leading to increased manufacturing costs and potentially resulting in toxic residues on surfaces, which should absolutely be avoided for all surfaces of medical and dental devices that are in direct or indirect contact with the patient (as is the case with spray lines).

Optimizing the grain size is not easy because, on the one hand, the printing time is inversely proportional to the grain size, which must therefore be maximized to reduce costs and reduce the risk of defect or malfunction of the machine during printing, and, on the other hand, the roughness of the surfaces is directly proportional to the grain size, which must therefore be minimized as much as possible. The optimal grain size therefore results from a two-parameter optimization. The grain size may also not be uniform throughout a handpiece made in a fully single-piece manner but, on the contrary, the head 10 may be printed with a powder having a grain size that is at least 1.5 times smaller than the grain size used for the 3D printing of the handle 10. In this way, it is possible to dissociate the material relating to different parts of the handpiece, or even parts that were previously separate from one another and then mutually assembled to one another, without losing the advantage of simplified single-piece manufacturing, that is to say, in one piece and via a single manufacturing operation.

Figures 7A, 7B and 7C illustrate respectively a side, front and three-dimensional view of a turbine produced in a single-piece manner, that is to say from end to end from the handle 11 to the head 10, highlighting the vertical growth direction of the 3D printing process. In the following, these three figures will be described jointly and the reference numbers will not be systematically repeated from one figure to another for the sake of clarity.

Figure 7A illustrates a profile view of a handpiece whose gripping handle 11 extends along an axis MM while the head is oriented perpendicular to a frontal plane P1, forming an angle of inclination a which is equal to that existing between the different printing planes P4 (several of which are represented in a superimposed manner) and the transverse plane P3 of the handle, that is to say the one perpendicular to the axis MM of the gripping handle 11. The growth direction D, during the 3D printing process, is here parallel to the frontal plane P1, but another setting could be carried out to optimize the precision of certain working areas of the handpiece 1 to be produced.

Figure 7B illustrates a front view of the handpiece 1 highlighting the sagittal plane P2 and the head 10 of which the diffuser 25 can be seen, and in particular the transverse outlet channels 253 of the latter; nevertheless, the curvature between the gripping handle 11 and the head 10 is no longer perceptible there. It is seen again, however, in three-dimensional figure 7C. From the above, it will be understood that the angle of inclination a, which corresponds both to the angle formed between the frontal plane P1 and the axis of the gripping handle M-M, and to that between the transverse plane P3 and that of the layers P4, allows a certain optimization of the growth direction D with respect to the handpiece 1 to be produced, in particular with regard to the curvatures of integrated internal pipes to be drawn. According to the preferred embodiment described, it is between 5° and 25°, and according to an even more preferred embodiment, it is between 10° and 20°.

Figures 8A and 8B which follow are intended to schematically illustrate a handpiece produced according to yet another preferred embodiment, comprising blind pipes, that is to say not through, but terminated by housings, the latter being intended to house sensors.

Figure 8A is a schematic sectional view of a handpiece produced according to such a preferred embodiment for the invention, and which contains such a blind conduit 24 intended for housing one or more sensors inside the handpiece 1. The blind conduit 24 begins with an open end 241 at the rear of the gripping handle 11, then has a fourth bifurcation 240 generating branches 243 each of which opens onto housings 242 in which the sensors 5 are housed. Figure 8B illustrates the detail of the head 10 of the handpiece of Figure 8A, containing two housings 242 in which a thermocouple 5A and a piezoelectric acceleration sensor 5B are respectively introduced as sensors 5 previously introduced in Figure 8A. The thermocouple 5A is described as “wired” because it is connected via a wire 50 to an energy source located elsewhere, preferably even outside the handpiece 1 as explained below.

The insertion of electronic sensors into dental or surgical handpieces aims to reduce risks for the patient. Indeed, such sensors can signal to the user the overheating of the handpiece head or the presence of excessive vibrations which could lead, respectively, to burns or injury to the patient.

The usual design of dental and surgical handpieces made it difficult to position the sensors 5, wired like the thermocouple 5A or wireless like the piezoelectric sensor 5B, near the head 10 or directly in the head of the handpiece, due to the limited space inside the head or in the junction part between the gripping handle 11 and the head 10. The creation of suitable housings, via a machining or drilling procedure, would risk breaking or weakening the carcass of the handpiece 1 (not referenced in these figures). In addition, the sensor 5 needs to be protected by a waterproof barrier that can prevent contact with spray water, body fluids and debris that are aspirated during clinical treatment. Machining such a barrier in such a limited space is technically complex and would logically lead to penalizing performance; in fact, for a turbine, one would either have to reduce the size of the turbine wheel, or, for a contra-angle, reduce the size of the ball bearings and/or gears, or compromise the ergonomics of the handpiece by increasing the weight and size of the head.

Inserting a sensor for its previously mentioned casing to make it waterproof does not resolve this problem because its positioning would then be even more complex, the casing then making the overall size of the component even greater. The production of a dental or surgical handpiece via 3D printing as illustrated in the schematic views of Figures 8A and 8B also makes it possible to directly integrate into the single-piece part integrated pipes called “blind” pipes 24 because they terminate in housings 242 adapted to receive electronic sensors in proximity or in the head of the handpiece 1. In fact, the 3D printing of the handpiece and the pipes in a single-piece part allows the production of curved pipes passing entirely through the handpiece 1 from the gripping handle 11 to the head 10 and whose front end is closed, which was previously unfeasible. Indeed, drilling or machining a pipe in the body of a handpiece could only make it possible to produce, on the contrary, rectilinear and/or very short closed pipes compared to the length of the handpiece. The formation of blind conduits 24, i.e. closed at the front and added during the assembly phase, is only possible for substantially straight and/or short conduits, due to the angled shape of the handpiece and the limited space inside the handpiece casing. In both cases, it was therefore almost impossible to position a sensor near or in the head of the handpiece from the rear of the gripping handle 11 of the handpiece. The only alternative option would therefore have been to insert the sensor directly into the head of the handpiece, which, however, makes it technically very difficult to achieve and also very expensive because it would be necessary to simultaneously ensure the sensor's tightness with respect to the spray water and the organic fluids aspirated during clinical treatments.

According to the particularly advantageous embodiment described, it is possible, after 3D printing, to insert and house one or more electronic sensors such as for example temperature sensors (thermocouples) or vibration sensors (accelerometers) in the vicinity of the head 10 or inside the head 10, while ensuring a perfect seal with respect to the water spray and the organic fluids that can be sucked up by the handpiece during the clinical treatment (the handpiece head being in the patient's mouth). The electronic sensors 5 such as the thermocouple 5A arranged in the housings 242 can be connected to an electronic console or to the dental unit through electrical wires passing through the cable or the hose connected to the handpiece, entering the handpiece through the open end 241 at the rear of the gripping handle 11, and passing through the handpiece inside the blind conduit 24 to its front end where a housing 242 is arranged as a terminal bulge. According to an advantageous variant, the sensor can be of the wireless type like the piezoelectric sensor 5B. In this case, the blind conduit 24 simply allows the sensor 5/5B to be inserted inside the handpiece 1 to its housing

242 near the head or in the head and then insert a glue or resin to both fix the position of the sensor and ensure the sealing of the sensor housing during reprocessing cycles, such as thermodisinfection and steam sterilization in an autoclave.

It is also important to note that plastic materials are thermal insulators and absorbents for mechanical vibrations. For this reason, the positioning of a thermal sensor (thermocouple) or vibration sensor (accelerometer) in a device obtained by plastic injection or overmolding in a plastic material would therefore be disadvantageous compared to the manufacturing process used in the context of the invention, because the sensor would then be highly isolated from the external environment by reducing the signal-to-noise ratio and/or considerably deteriorating its reaction time. Thus, the use of 3D printing in a metallic material proves to be particularly advantageous compared to the aforementioned manufacturing techniques using plastic materials.

Another interesting aspect related to the 3D printing technique is to allow the realization of selective hardnesses depending on whether one is at the heart of the part or at its external surface. Thus, according to a preferred embodiment, one seeks to obtain a micro-hardness of the external surfaces of the carcass of the handpiece or of the external cap of the gripping handle 11 as being at least 20% higher than those of the internal surfaces. This is preferably achieved following a heat treatment of metal powders prior to the 3D printing step, and a subsequent treatment by pulsed-plasma of the external surfaces. It will be noted here that in general, it is not possible to apply the same heat or physicochemical treatments to the steels obtained from 3D printing compared to the usual treatments of machined steels, before or after machining. More generally, it would be possible either to carry out specific treatments after 3D printing - these treatments being generally different from the treatments carried out for machined steels; for example, to impact the hardness, after 3D printing an "annealing" is sufficient whereas a machined steel requires quenching - or to carry out treatments for the powders before the 3D printing operation, or a combination of these two options. Treated powders change morphology and chemical composition and can give different fatigue and friction characteristics than untreated powders.

Figure 9 finally concerns a schematic sectional view of a handpiece 1 produced according to a preferred variant for implementing the invention, according to which a mixer 3 is provided in the gripping handle 11 in place of a diffuser in the head 10. This mixer 3 consists of a connection via a confluence between the air spray channel 21 and the water spray channel 22 at a mixing zone M located between the middle of the gripping handle 11 and its rear end. The mixer thus consists of a sort of reverse bifurcation, with regard to the direction of flow of the fluids, between the mixed spray channel 26, downstream of the mixer 3, and which conveys the air-water mixture towards the head 10, and its two tributaries upstream of the mixer 3, i.e. the air spray channel 21 and the water spray channel 22. In this variant allowing an alternative to the diffuser of the previous embodiments, 3D printing allowing the production of a single-piece part is always advantageous compared to the connection of angular channel segments having much less optimal fluid flow properties.

In the context of the invention, a simplified manufacturing and assembly process has been described for the production of dental handpieces, presenting reduced costs and time on the production line, while providing increased freedom in terms of geometric design and the elimination of pointed or simply angular parts.

The use of three-dimensional printing (3D printing) employed in the context of the invention makes it possible to produce parts in a monobloc, it is also possible to reduce in particular the dispersion of the positioning and the shape of the spray pipes, thus improving the quality of the sprays, and of the light transmission pipes, thus reducing the risk of breakage of the light conductor (glass rod or optical fiber) during assembly and/or operation. Furthermore, the absence of an assembly phase of the pipes makes it possible to optimize the arrangement of the latter inside the carcass of the device, for example, their curvature and/or their section could change several times from the rear part to the head of the device.

3D printing in metallic materials, such as steel or titanium, also makes it possible to increase the reliability and robustness of pneumatic and light transmission lines in the event of a fall or mechanical shock.

A handpiece made according to the technical teachings of the invention also provides the possibility of minimizing vibrations and noise by design, thanks to the fact that the interfaces between the solid elements are minimized and therefore the device vibrates as a 'whole' - the vibration modes are easily calculated through finite element simulations of the single-piece part integrating the carcass and pneumatic and light transmission lines.

Claims

Claims 1. Dental or surgical handpiece (1) formed of a head (10) and a gripping handle (11) each provided respectively with at least one integrated internal pipe (2) chosen from a pneumatic pipe (20), a light transmission pipe (23), and a blind pipe (24) adapted for housing one or more electronic sensors (5), characterized in that at least one element chosen from an internal carcass (111) of said handle (11) and said head (10) is produced by 3D printing in metal and comprises said pneumatic pipe (20) and/or said light transmission pipe (23) and/or said blind pipe (24) as an integrated internal pipe (2) in a single piece. 2. Dental or surgical handpiece (1) according to claim 1, characterized in that it is produced from end to end, from said handle (11) to said head (10), by 3D printing and comprises at least one air spray channel. (21) and a water spray channel (22) as pneumatic lines (20), each of said pneumatic lines (20) being free of angular parts. 3. Dental or surgical handpiece (1) according to claim 2, characterized in that it comprises a diffuser (24) integrated in said head (10), said diffuser being formed of an upper ring (241) for the air supply, a lower ring (242) for the water supply, and a plurality of transverse outlet channels (243) connecting in parallel said upper ring (241) to said lower ring (242), said diffuser (24) being directly connected to said air spray channel (21) and to said water spray channel (22). 4. Dental or surgical handpiece (1) according to one of the preceding claims, characterized in that said integrated internal pipe (2) comprises at least one bifurcation. 5. Dental or surgical handpiece (1) according to claim 4, characterized in that said integrated internal duct (2) has a first double bifurcation (210) of an air spray channel (21) and/or a second double bifurcation (220) of a water spray channel (22). 6. Dental or surgical handpiece (1) according to one of claims 4 or 5, characterized in that said integrated internal pipe (2) has a third bifurcation (230) of a light transmission pipe (23), followed by two curved end parts (230B) in said head (10). 7. Dental or surgical handpiece (1) according to one of the preceding claims, in which at least one pneumatic pipe (20) has an elliptical section (20S). 8. Dental or surgical handpiece (1) according to one of the preceding claims, in which at least one light transmission pipe (23) has a hexagonal section (23S). 9. Dental or surgical handpiece (1) according to one of the preceding claims, in which at least one light transmission pipe (23) has a variable section following a wavy profile (23A). 10. Dental or surgical handpiece (1) according to one of the preceding claims, comprising a pneumatic cooling pipe (20) of helical shape (20H). 11. Dental or surgical handpiece (1) according to one of the preceding claims 2 to 10, characterized in that the 3D printing process determines a surface roughness state (R) on an external surface (110A) of an external cap (110) of said gripping handle (11) giving it anti-slip properties. 12. Dental or surgical handpiece (1) according to one of claims 2 to 11, characterized in that the micro-hardness of the outer surfaces of said carcass (110) of said handpiece (1) or of an outer cap (110) of said gripping handle (11) is at least 20% higher than the hardness of the inner surfaces following a heat treatment of metal powders prior to the 3D printing step, and a subsequent treatment by pulsed-plasma of said outer surfaces. 13. Dental or surgical handpiece (1) according to one of the preceding claims, comprising at least one blind conduit (24) adapted for housing one or more electronic sensors (5), said blind conduit comprising an open end (241) at the level of the gripping handle (11), and being closed at the level of the head (10) by a housing (243). 14. Dental or surgical handpiece (1) according to one of claims 1 or 2, characterized in that it comprises a mixer (3) for mixed spray channel (26) arranged in said internal carcass (111) of said gripping handle (11). 15. Method for 3D printing a dental or surgical handpiece (1) according to one of the preceding claims 1 to 14, characterized by a growth direction (D) going from said gripping handle (11) towards said head (10), the microscopic growth layers being superimposed according to printing planes (P4) perpendicular to said growth direction (D) and oriented at an angle (a) of between 5° and 25° relative to the transverse plane (P3) of said gripping handle (11).