Robotic device for tooth preparation in the patient's mouth with base platform, patient chair, support structure for accessory arm and tool arm controlled by computer system.

Abstract

A robotic device that allows for the fully automated, direct preparation of teeth in the patient's mouth necessary for the placement of partial or total prosthetic elements, and which consists of a base platform (B), a chair with headrest and headrest for patient positioning and support (F), a very rigid articulated support structure (S) at the end of which is fixed, on a vertical sleeve (S3) at the end of the structure, the robotic part composed of two arms, a tool-holding arm (RO) and an accessory-holding arm (RS), said support structure (S) ensuring the positioning of this robotic part as close as possible to the intervention area on the patient and constituting, by the sleeve (S3),a very precise physical basis of the orthonormal reference system for controlling the movements and forces of the moving elements of the robotic part, whose dimensions are consequently reduced and whose information processing, piloting and control are ensured by the device's own dedicated computer system. Figure to be published for the abstract: Fig 7,

Description

Title of the invention: Robotic device for cutting teeth in the patient's mouth with base platform, patient chair, support structure for accessory arm and tool arm controlled by computer system. Technical field of the invention

[0001] The invention relates to the field of dental robots used during interventions for partial (onlay, inlay, veneer) or total (crown) coronal-peripheral preparations. State of the prior art

[0002] In any automated mechanical device with manipulation or machining of parts it is essential to define two coordinate systems each with a material origin that is at the same time very precise, very rigid and very stable. The first coordinate system is called the “machine coordinate system”, the origin of this system is designated by the term “machine zero”, it corresponds to a predefined and immutable fixed point specific to the machine. It is the reference and starting point for all other points used elsewhere in any handling or machining process. In particular, the “rest” and “start” positions of all the machining elements of the machine are defined in relation to this “machine zero”. Then, another coordinate system is defined at the part level, the zero of which is called “part zero” and which corresponds to the starting point of the machining movements for the program that controls the machining. This coordinate system is obviously as close as possible to the part to be machined, or even on the part to be machined. Its location relative to the machine coordinate system must be able to be carried out at any time with great precision. On a numerically controlled machine tool, the conditions of rigidity and stability, and therefore precision, are relatively easy to obtain given the robust and fixed structure of the machine. In addition, the parts carrying the machining tools are fixed to parts of the machine that are also rigid, so that deformations are, if not non-existent, at least completely tiny and negligible. The required stability conditions are therefore always met, and it is not uncommon to obtain accuracies of the order of a micron, or even better, in certain machine machining operations.

[0003] In the case of a robot, it is also important to be able to define these two coordinate systems, but it is much more difficult to meet the conditions of rigidity and stability required to achieve very high precision in the execution of tasks performed by the robot. The precise location of “part zero” in relation to “machine zero” constituted by the fixed base of the robot is often very delicate. Indeed, at the hardware configuration level, robots are generally made up of one or more arms, each arm comprising a certain number of more or less long segments connected to each other by joints. And at the end of the arm we find the organ intended to carry out the manipulation or machining function. Joints are of two types: revolute joints and prismatic joints. The revolute joint is a pivot-type joint that allows rotation around a common axis. The relative position between the two connected elements is given by the angle around this axis. One of the difficulties is the material realization of a revolute joint without so-called tilting play. Such play causes a shift between the axes of rotation of the two elements of the joint and therefore great imprecision in the movements. The prismatic joint is a slide type joint, the movement between two elements is therefore a translation along a common axis, which means that a linear displacement will occur measured by a distance along this axis. Here again it is difficult to obtain a prismatic joint without play, the solution often used is to increase the length of the slide which significantly weighs down the assembly considered. The base of the robot, which constitutes the starting point of the movements, the “machine coordinate system” with the “machine zero”, is most often far from the segment tips on which the tools or the manipulation organs are placed, organs which are in contact with the part where the “part zero” is located. Thus, in addition to the problems of play in the different joints, all the robot organs which are located between the base and the part to be manipulated are subjected to multiple tensile, compressive, bending and / or torsion constraints which generate deformations and even sometimes oscillations and vibrations of the different organs. The problem is all the more acute as these organs are very long. The location of “part zero” in relation to “machine zero” is therefore often quite imprecise and rigorous control of movements and forces at the end of the robot arm is made complicated. This means that using robots in a fully automated manner for tasks requiring a very high level of precision is generally very difficult.

[0004] Of course, in many applications, such as object manipulations less fragile, a lower level of precision remains compatible with the requirements of the application and it is then possible to make the robot work fully automatically. On the other hand, it is obvious that for specific and limited applications, in the field of research or space for example, very specific robots can be designed to be piloted and controlled in a fully automated manner. But the design, development, manufacturing and fine-tuning of these robots result in costs that are incomparable with what can be envisaged in other fields. But for applications that require a very high level of precision in the general industrial field or even the so-called “consumer” medical field, the use of robots operating fully automatically remains, if not impossible, at least quite problematic.

[0005] This is particularly the case for robots in dental applications. This is all the more so since, in this field, the basic base of the robot which constitutes the “reference system” is, for practical reasons, very often quite far from the intervention zone. This therefore requires large robot arms made up of very long segments between the joints [Fig.l]. This results in significant overhangs causing, with the weight of the joints and that of the segments themselves, an amplification of the internal clearances of the parts, elastic deformations, oscillations and vibrations as already mentioned. It should also be noted that this geometry with large robot arms complicates and makes very expensive the concrete realization of the robotic system, not only because of the large dimensions of the elements constituting the robotic part but also because the control system must be particularly elaborate to try to at least partially compensate for the inaccuracies linked to the geometry and the masses involved, without however being able to compensate for them completely.

[0006] Some solutions have been proposed to try to limit these problems of imprecision. For example, one option is to further thin the segments and reduce the size of the joints in order to limit the masses and thus the forces associated with them and the resulting deformations. But such a solution results in reducing the moments of inertia of the parts concerned and therefore does not significantly reduce the deformations [Fig.l]. Another option is to do the opposite, that is, to have larger segments and larger joints in order to reduce deformations. But this then results in a significant increase in the efforts required for movement as well as dynamic inertia linked to movements and does not improve really the level of precision. Of course, significant progress has been made in the field of computerized means of piloting and controlling robots, progress which nevertheless allows for some progress, but is insufficient to significantly eliminate the aforementioned problems.

[0007] Another solution sometimes used consists of fixing to the patient's mandible a large structure which often includes a semi-circular rail on which circulates a mini-robot which holds the cutting tool, a camera whose position is offset in relation to the cutting tool and possibly also a stirrup which is positioned on a tooth of the patient. This structure constitutes the “zero machine” reference system, very close to the intervention zone, in relation to which the movements of the robot heads are thus defined, piloted and controlled.

[0008] In order to improve the level of precision, it is also necessary to limit the deformation problems mentioned above. But this can only be done on condition that the structure is sufficiently rigid, which is not without significant bulk and therefore weight. Thus, such a solution has some disadvantages. First of all, it poses certain risks of injury to the patient who must also be able to support the fairly substantial weight of such equipment fixed to his jaw, then it also causes, for the patient, a certain discomfort and finally the time taken to adapt, install, adjust and remove this structure is very probably relatively long. In addition, due to the geometry and dimensions, the possibilities of moving the cutting tool robot, the camera and the caliper are probably quite limited. In particular, the outer surface and the top of the tooth are easily accessible, but to access other parts of the tooth, other arrangements must be made and other devices must be added. Finally, direct recording of images of the entire working area during the operation becomes significantly more complicated [Fig. 2].

[0009] It has also been proposed to fix a complex and bulky structure to the patient's head [Fig. 3]. Such a solution has practically the same disadvantages as the previous solution without bringing any truly significant improvements.

[0010] In conclusion, even if progress in piloting and control systems makes it possible to reduce uncertainties in the location and guidance of the tool, there still remain certain inaccuracies at the end of the robot arm which limit the possibilities of using robots for the automated execution of tasks which are necessary for dental implant surgery. In particular, tooth grinding is a delicate procedure that practitioners often dread because it requires extreme concentration, it takes a lot of time and there are many risks of error. Presentation of the invention

[0011] The aim of the invention is to provide decisive improvements to the dental robot and thus to propose a robotic device making it possible to carry out, directly in the patient's mouth and in a fully automated manner, the tooth cutting operations necessary for the fitting of partial (inlay, onlay, veneer) or total (crown) prosthetic elements. This system is shown diagrammatically in [[Fig.4]], it consists of: • a base platform placed on the ground (B) [Fig.6], • an instrumented chair fixed to the base platform and which is provided with a headrest with headrest for installing and maintaining the patient (F) [Fig.5], • a very rigid support structure (S) [Fig.6], fixed to the base platform (B) and placed on one side of the chair, near the headrest and which comprises a vertical column (SO), two articulated horizontal segments (SI) and (S2) and, at the end, a short pivoting sleeve (S3) which locks in two vertical positions at 180°, none of the articulations of this support structure being motorized, • of the two arms of the robotic part [Fig.7], the cutting tool-holder arm (RO) and the accessory-holder arm (RS) carrying the stirrup (ET) and the 3D camera (CA), each of the arms being fixed to one end of the vertical sleeve (S3) of the support structure (S) by a motorized rotoid joint with a vertical axis, • the computer system [Fig.4] for processing information, piloting and controlling the robotic part (I).

[0012] The articulated support structure (S) placed next to the patient's chair (F) is a very rigid assembly which ensures the support and positioning of the robotic part very close to the intervention zone at the patient's level. Once the joints are blocked, this support structure constitutes the very precise physical reference base for controlling the movements of all the mobile elements of the robotic part attached to it. The analysis of the state of the art highlighted the importance in automatic machines of the position of the “machine coordinate system” with the “machine zero”, which must remain almost unchanged. It was also indicated that a “part reference system” with “part zero” constitutes, in addition to the previous system, a practical means of make it easier to control the machine. • The first characteristic of the invention is that these two notions are incorporated into it. It is at the center of the sleeve (S3) at the end of the support structure (S) that the origin, the “machine zero”, of the robot reference system is placed, which acts as the “machine coordinate system” which is called in this case the “robot coordinate system” with the “robot zero” [[Fig.7]]. And it is at the level of a horseshoe-shaped stirrup placed by the accessory arm around the base of the patient's tooth to be treated or a neighboring tooth that the “part reference system” is placed with the “part zero”, which is called here the “tooth reference system” with the “tooth zero” [[Fig.8]]. • The second characteristic of the invention is the fact that the origin, the “robot zero” of the “robot coordinate system”, is located close to the work area at the patient’s mouth. This allows for reduced dimensioning of the organs constituting the arms of the robot part, the segments which constitute them are in fact very short, less than 500 mm for the first segment and less than 300 mm for the second. This results in a very significant reduction of all the parameters likely to limit precision: weight of the parts, overhang, effects of possible play between parts, elastic bending and torsion, oscillations and vibrations. • The third characteristic of the invention lies in the very constitution of the robot part which is presented in the form of two separate arms, the tool-holder arm (RO), which, of course, carries and manipulates the tooth cutting tool with its integrated systems for lubrication / spraying and lighting and the accessory-holder arm (RS) which carries and manipulates the stirrup (ET) and the 3D camera (CA). The tool-holder arm (RO) is piloted with the “robot coordinate system” as its reference system, but the possible trajectory corrections imposed on it are defined from the recorded movements of the “tooth reference system” relative to the “robot coordinate system”. This “tooth reference system” [Fig.8], by the fact that it is attached to a patient’s tooth by the horseshoe-shaped stirrup (ET), in fact follows all possible movements of the patient at this level, even those which have a reduced amplitude.These movements are recorded at the system level and converted into trajectory corrections for the tool. Of course, given the current capabilities of computer systems, these operations are carried out extremely quickly and very precisely. Detailed description of the invention

[0013] As already indicated in the presentation, the invention is therefore presented in the form of a complete equipment [Fig.4] including the following five elements: 1. The base platform (B), [Fig.4], [Fig.6] and [Fig.7], placed on the ground on which the patient chair (F) and the support structure (S) are fixed. 2. The swivel chair where the patient sits in a semi-reclined position, [Fig.4] and [Fig.5]. This chair is equipped with a manual mechanical vertical translation device with a maximum stroke of 200 mm which allows the height to be adjusted according to the patient's size and the intervention area. A headrest with a front flap in the form of a headrest to support the patient's head and a set of sensors to record the patient's movements complete the chair's equipment. Two emergency stop buttons, located on either side of the chair, allow the practitioner to stop the intervention at any time if necessary. 3. The support structure (S) of the robotic part, [[Fig.6]] and [[Fig.7]]. This is composed, in addition to the column (S0) fixed to the base platform (B), of a set of two horizontal segments (SI) and S2), the first of a length less than 500 mm and the second of a length less than 300 mm. The column and the two segments are connected to each other by two rotoid joints with vertical axis (SA01) and (SA12). The segments of this support structure are preferably tubular given that on the one hand the integration of the longitudinal rotoid joints is relatively easy to achieve since the motorization can be placed inside the segment itself and on the other hand the inertia of the section which, with the length, has a determining impact on the bending at the end, remains relatively important. As an example, it can be indicated that for a segment with a length of 500 mm, an external diameter of 100 mm and an internal diameter of 80 mm, we will have, for a bending load at the end of 200 N, a bending value less than 4 / 100th of a mm while taking into account the self-weight of the segment. However, the load level of 200 N taken here as an example is already higher than the load which is actually applied at the end of the segment. At the end of the second horizontal segment (S2) of the support structure (S), [ [Fig.7]] is attached, by a horizontal axis rotoid joint (SA23), a short pivoting vertical sleeve (S3) with a length of less than 200 mm on which are fixed, on either side, the two arms of the robotic part (RO for the tool-carrying arm) and (RS for the accessory-carrying arm). The “robot zero” of the “robot coordinate system” is placed in the center of this sleeve (S3) at the end of the support structure (S). In a preferred configuration of the invention, all the rotoid joints of the support structure are in the form of two single-row angular contact ball bearings mounted in an “O” configuration and preloaded, [[Fig.9]]. A diagram [[Fig. 10]], which will be detailed later in the description, explains the advantages of the preferred solution chosen. The support structure itself is not integrated into the robot part itself, so its joints are not motorized and, given that the joints are bearing joints and no significant effort is required for this operation, the orientation of the segments is done manually. The rotational positioning reference of each rotoid joint of this support structure is in the form of a ball pushed by a small spring and which is placed in a spherical cap-shaped imprint at each predetermined position. To reach another position, a simple pressure from the practitioner is sufficient for the ball to retract. Each joint is equipped with an electromechanical locking brake activated by the practitioner when the desired position of the base sleeve (S3) of the robot arms is reached just before the robot part is put into operation. 4. The robot part fixed on the short vertical sleeve (S3), [Fig.6] and [Fig.7], which constitutes the end of the support structure (S). This robot part, [Fig. 11] to [Fig. 17], whose dimensions are reduced thanks to the proximity of the base constituted by the sleeve (S3) of the support structure (S), is composed of two robot arms (RO) and (RS). Each arm comprises two articulated segments (ROSI and ROS2) and (RSSI and RSS2) and the support block of the controlled organ(s) at the end: the support block for the tool (PO) with the tool (OT) and its integrated lubrication / spraying and lighting systems for the arm (RO) and the support block for the accessories (PS) with the stirrup (ET) and the 3D camera (CA). Each robot arm is attached to one end of the short vertical sleeve (S3) of the support structure (S) by means of a double rotoid joint: a vertical axis joint, respectively (ROA1) and (RSA1) and a horizontal axis joint, respectively (ROA2) and (RSA2).These two joints, integral parts of the robot part, are obviously motorized. 1. The fixed rotating element of the vertical axis joint (ROA1 and RSA1), which constitutes the base of each robot arm, is directly attached to the short sleeve (S3) of the support structure (S) and the rotating element of this vertical axis joint constitutes the support of the horizontal axis rotoid joint (ROA2 and RSA2) to which the first segment of the relevant robot arm (ROSI and RSS1). The second segment of each robot arm (R0S2 and RSS2), shorter than the first, is connected to the first by a horizontal axis rotoid joint (R0A3 and RS A3). As with the support structure and for the same reasons, the segments that make up each robot arm are preferably tubular but of smaller dimensions. 2. The accessory arm (RS), [Fig 11], which is connected at the end of the second segment by a double cross-type joint, includes the accessory support block (PS) with the handling mechanism with several spherical joints for the stirrup (ET) to be placed around the base of the tooth to be cut or a neighboring tooth and for the 3D camera (CA) which produces the images allowing control and monitoring during the entire cutting operation. 3. The tool arm (RO), [Fig 12], which is connected at the end of the second segment by a double cross-type joint, includes the tool support block (PO) with the motorized manipulation mechanism with several spherical joints and the cutting tool (OT) of the tooth in the patient's mouth. In figures 11 and 12 each arm is shown in isolation to simplify the representation but it is quite obvious that in the real configuration both arms are present and operate at the same time. As an example and illustration, two types of tools, among all those used in dental practice, are shown, [Fig 13]. These two types of tools with their integrated lubrication / spraying and lighting systems can, one or the other, of course be mounted on the robotic device of the invention. All the revolving joints of the robot arms are on the one hand motorized by means of a stepper electric motor or, preferably, a direct current motor and on the other hand equipped with a pro-prioceptive position sensor to indicate the exact angular position. The information from the sensors is sent to the system so that, taking into account the precise length of the segments, the location of the various end components, tool (OT), stirrup (ET) and 3D camera (CA), can be defined very rigorously in relation to the reference system. Four arm positions are to be considered depending on the lo calization of the patient's tooth to be treated: position for lower jaw and tooth in the left part (MIG), represented [Fig 14], position for upper jaw and tooth in the right part (MSD), represented [Fig 15], position for lower jaw and tooth in the right part (MID) represented [Fig 16] and position for upper jaw and tooth in the left part (MSG) represented [Fig 17]. There is therefore a need to have two different configurations for the tool (OT) support block (PO) as well as for the accessories support block (PS): one configuration that covers both the case of the lower jaw with tooth on the left side (MIG) and the case of the upper jaw with tooth on the right side (MSD) and the other configuration that covers both the case of the lower jaw with tooth on the right side (MID) and the case of the upper jaw with tooth on the left side (MSG). These two configurations only differ in that it is necessary to rotate 180°: the tool (OT) in the tool support block (PO) and the stirrup (ET) and the 3D camera (CA) in the accessories support block (PS), each by its upper articulation (R0A5, RSA5 and RSA7). 5. The entire office-desk computer system which is placed near the chair and which includes the computer with the central unit integrating all the computer programs for data processing, piloting and control of the whole, the human-machine interfaces (keyboard, mouse and others) and the screens allowing the practitioner to follow the intervention and to intervene if and when necessary. In addition, the part relating to the processing of data in the computer system of the invention is provided with a particular function, detailed later, allowing in particular the conversion of external files transmitted into files directly usable by the robot part.In order to avoid any collision between the elements constituting the tool-carrying arm (RO) and the elements constituting the accessory-carrying arm (RS), specific software is incorporated into the system to carry out constant control by 3D imaging of the respective positions of the different elements, said software stopping any movement of an element of a moving arm which could cause, due to its imposed trajectory, a collision with an element of the other arm. A third emergency stop button is located at the level of the practitioner's desk-desk.

[0014] It is therefore the 3D camera (CA) mounted on the accessory-carrying arm (RS) of the robot part which provides the shots which make it possible on the one hand to provide the 3D color images serving as a basis for the automatic piloting and the control of the robot tasks robotized and on the other hand to display these 3D images on screen so that the practitioner can follow the operations of the robot arms and intervene if necessary.

[0015] It should also be emphasized that the design of the double-arm robot part has the advantage of having only the cutting tool fixed at the end of the tool-carrying arm (RO). This makes it possible to significantly limit the weight of this subassembly, support block (PO) and tool (OT), and, thus, to limit the forces to be supported by each robot arm, to significantly improve the precision of the movements.

[0016] The weight of the components fixed at the end of the accessory arm (RS), the support block (PS), the stirrup (ET) with its mini-articulated arm and the 3D camera (CA), is less problematic because • first a small part of this weight is taken up at the level of the support on the tooth itself, • then the organs constituting the arm can be a little more oversized than those of the tool-carrying arm, • finally the controlled movements of this arm (RS) are limited to the initial positioning of the stirrup (ET), once this positioning is carried out, unlike the tool-carrying arm (RO), there is no need for precise control of the accessory holder which remains passive. The system simply records the movements of the stirrup (ET), following the patient's movements, so that these can be analyzed and converted into possible trajectory modifications for the cutting tool.

[0017] The characteristics of the invention as well as the technical details presented previously give the robotic assembly of the invention a level of precision which makes it possible to carry out, in a fully automatic manner, a cutting of the tooth presenting only minimal and acceptable deviations from the pre-established theoretical definition integrated in specific files. The phase of developing an optical impression from the approximate actual cutting is no longer necessary. The manufacture of the prosthesis by an automatic machine can then be anticipated and thus be carried out before or during the cutting of the tooth by the robotic device of the invention. The prosthesis is thus available as soon as the cutting operation is finished and can be fixed immediately by the practitioner in the patient's mouth. This results in a considerable saving of time in the progress of the entire intervention.

[0018] The characteristics and advantages of the invention are explained in even more detail in the detailed description of figures 4 to 17.

[0019] [Fig.4] shows an example of a general view of the installation of the robotic device with the materialization of the computerized piloting and control system (I) in front of which the practitioner can install himself and, on the base platform (B), the robot assembly (R) with the chair (F) on which the patient is installed, the support structure (S) and the two arms of the robotic part (RO) and (RS).

[0020] [Fig.5] shows the support structure (S) placed next to the chair (F) on which the patient is installed. It shows the base of the chair (F1) which is fixed to the base platform (B) shown in [Fig.1], the pivot and lifting device (F2) which allows a slight latitude in the orientation and in the altitude of the chair in relation to the support structure, the area (F3) for installing the patient, the headrest (F4) and the headrest (F5) which allows a certain immobilization of the patient's head.

[0021] In [Fig.6] we can see the base platform (B) placed on the ground and on which the chair (not shown) is fixed and the support structure (S) with the main column (S0), the vertical axis rotoid joint (SOI) connecting the column (S0) to the first horizontal segment (SI), the vertical axis rotoid joint (S12) connecting the first horizontal segment (SI) to the second (S2) and the horizontal axis rotoid joint (S23) connecting the second segment (S2) to the robot arm holder sleeve (S3).

[0022] [Fig.7] shows the general configuration of the support structure (S) fixed to the base platform (B) placed on the ground. Note the sleeve (S3) at the end of the second segment (S2) of the support structure (S), sleeve on which the two arms (RO and RS) just shown of the robot part of the device are fixed. Note the horizontal axis rotoid joint (SA23) which is part of the support structure just like the sleeve (S3) itself. The two pairs of rotoid joints constituting the base of the robot arms are represented: the vertical axis joint (ROA1) and the horizontal axis joint (ROA2), for the tool-carrying arm (RO) and the vertical axis joints (RSA1) and the horizontal axis joint (RSA2) for the accessory-carrying arm (RS). The reference coordinate system called the “robot coordinate system” whose origin, the “robot zero”, is positioned very precisely in the middle of the sleeve (Sd) is also plotted in the figure.The Y axis corresponds to the orientation of the arm segments, the X axis, perpendicular to the Y axis, is oriented towards the inside of the patient's mouth and the Z axis is vertical.

[0023] [Fig.8] shows the positioning of the stirrup (ET) at the base of the patient's affected tooth or a neighboring tooth. The “tooth zero” of the “tooth reference system” coordinates is located at the middle of this stirrup. The orientations of the X, Y and Z axes are the same as those of the “robot coordinate system”.

[0024] [[Fig.9]] shows the preferred configuration of the rotoidal joints of the support structure which makes it possible to significantly increase the rigidity of the latter and thus considerably improve the precision of the entire robotic device. These joints are in the form of two single-row angular contact ball bearings mounted in an “O” and preloaded. This assembly makes it possible above all to completely cancel the tilting play (sometimes also designated by the term “tilting”). Thus, at the level of the joints themselves, any application of a tilting torque will only cause extremely reduced additional elastic deformations of the already preloaded rolling elements, in this case the balls and the raceways of the rings. These elastic deformations are all the more negligible as the preload is high. Furthermore, taking into account on the one hand the fact that the problem of bearing life, which is generally linked to the rotation speed, does not arise since there is no real rotation speed in the movements of the support structure and on the other hand that for a rolling bearing the extremely low rotation torque, it is possible to apply a very high preload to the rolling bearing which guarantees an almost zero amplitude of tilting. Furthermore, it can be noted that the use of two angular contact ball bearings placed side by side and mounted in an “O” configuration allows a significant reduction in the overall dimensions (b) while ensuring a much greater distance (a) between the points of application of the radial forces F linked to the torque C at the bearings. Finally, as explained in the following [Fig. 10], due to the preload, only part of the external torque is applied to the rolling elements and causes additional elastic deformation which is, in this case, practically negligible.

[0025] The diagram in [[Fig. 10]] explains the internal distribution of the forces generated by the application of an external force (Fext) on a preloaded assembly with a force (Fo). By this preload (Fo) the compression parts of the assembly are compressed by ô comp and the tension parts have an elongation of ô tract. The compression stiffness of the compressed parts being (Fo / ô comp) and the tension stiffness of the tension parts being (Fo / ô tract). We can thus see that the external force (Fext) is distributed between the two elements and only the part (Fae) of the external force is applied to the tension parts. The total force then becomes (Fo + Fae) and not (Fo + Fext) as one might think at first glance. This principle therefore also applies to the “O” assembly of preloaded bearings for which any tilting torque has only a very partial effect on the deformations. These are already quite low with a preload close to zero, they become practically negligible for a significant preload such as that which can be applied to the rotoid joints of the support structure.

[0026] Figures 11 to 17 show images of the different configurations of the two robot arms: the accessory arm (RS) and the tool arm (RO).

[0027] [[Fig.l] 1] shows the general configuration of the accessory arm (RS), the tool arm having been removed for ease of presentation. It shows the end of the support structure (S) with the sleeve (S3) to which the arm (RS) is attached by the ar rotoid joints (RSA1) and (RSA2) already described, the two segments (RSS1) and (RSS2) with the rotoid joint (RSA3) and the cross joint (RSA4). At the level of the support block (PS) of the accessories, the joints (RSA5) with vertical axis and (RSA6) with horizontal axis for the 3D camera (CA) and (RSA7) with vertical axis and (RSA8) with horizontal axis for the stirrup (ET), itself equipped with three joints (RSA9, RSA10 and RSA11), allow the precise positioning of each element concerned. It can be noted that the motorization of the joints in the axis of the segments is not visible because it is mounted inside the segment itself while the motorizations of the perpendicular joints are generally visible.

[0028] [Fig. 12] shows the general configuration of the tool-carrying arm (RO), the accessory-carrying arm having been removed to facilitate presentation, it is possible to see the end of the support structure (S) with the sleeve (S3) to which the arm (RO) is attached by the rotoid joints (ROA1) and (ROA2) already described, the two segments (ROSI) and (ROS2) with first the rotoid joint with horizontal axis (ROA3) and the cross-joint (ROA4) and, at the level of the support block (PO), the joints (ROA5) with vertical axis and (ROA6) with horizontal axis, this last part comprising the fixing of the cutting tool (OT) with its integrated lubrication / spraying and lighting systems.

[0029] [Fig. 13] shows two examples of cutting tools, a horizontal body turbine (A) and a vertical body turbine (B), among all the tools that can equip the device of the invention. Whatever the tool chosen by the practitioner, the mechanism for fixing to the tool holder (PO) is designed and adapted in such a way that the cutter or cutting member (F) is always located at the same level.

[0030] [Fig. 14] represents the position of the two robot arms in the case of an intervention on a tooth in the left part of the lower jaw of the patient “MIG”.

[0031] [Fig. 15] represents the position of the two robot arms in the case of an intervention on a tooth in the right part of the upper jaw of the patient “MSD”.

[0032] For these two configurations the tool support block (PO) and the accessory support block (PS) have the same orientation.

[0033] [Fig. 16] represents the position of the two robot arms in the case of an intervention on a tooth in the right part of the lower jaw of the “MID” patient.

[0034] [Fig. 17] represents the position of the two robot arms in the case of an intervention on a tooth in the left part of the upper jaw of the patient “MSG”.

[0035] For these two configurations the tool support block (PO) and the accessory support block (PS) have the same orientation.

[0036] [Fig. 18A], 18B, 18C and 18D illustrate by means of flowcharts the simplification that results from the use of the robotic device of the invention for an intervention on a patient for the fitting of a partial or total prosthetic element.

[0037] [Fig.18A] specifies the actions prior to the intervention of the robotic device of the invention.

[0038] [Fig.l8B] shows the necessary adjustments.

[0039] [Fig. 18C] details how the intervention of the robotic device of the invention fits into the entire treatment process concerned and shows the decisive advantage of the robotic device of the invention which allows the manufacture of the prosthesis in masked time (either before or during the intervention of the robotic device).

[0040] [Fig.l8D] lists the additional actions that are carried out at the end of the intervention.

[0041] In addition to the preceding indications, it should be recalled that, during the intervention, the joints of the support structure (S) were previously blocked in the desired configurations by the electromechanical devices operated by the practitioner. Then, at the robot part level, some joints are also blocked by the control system. This is the case for joints RSA1 to RSA8 of the accessory arm (RS) as soon as the stirrup (ET) has been put in place. Only the joints of the mini-arm of the stirrup (ET) itself (RSA9, RSA10 and RSA11) are not blocked. Each of these last joints of the stirrup mini-arm is equipped with a very precise angular position sensor in order to record all the movements of the stirrup (ET) caused by possible movements of the patient. It is the indications provided by these sensors that make it possible to record the movements of the “tooth reference system” with the “tooth zero” (concept explained previously) and to carry out tool path corrections during automatic cutting of the tooth.The system's analysis of the derivatives of the displacement functions as a function of time resulting from the indications of these sensors makes it possible to determine the abruptness of the movements. At the tool holder (PO), all joints remain controlled during the intervention. Joints R0A1 and R0A2 are more specifically actuated for longitudinal movements of more than 20 mm or angular movements of more than 10°. Joints R0A3 and R0A4 are more specifically actuated for longitudinal movements of more than 5 mm or angular movements of more than 5° and joints R0A5 and R0A6 are more specifically actuated for longitudinal movements of less than 5 mm and angular movements of less than 5°. A small torsion return spring is attached to the ROA6 joint of the tool support block (PO), which, in the absence of power supply to the joint motor, ensures a very slight vertical clearance of the tool, between 2 and 5 mm, from the patient's tooth. This safety feature prevents any in interference with the patient's tooth in the event of sudden movement of the latter during an emergency stop.

[0042] In a preferred configuration of the invention, at the level of the accessory holder assembly (PS), the mini-arm of the stirrup (ET) is provided with an electromechanical device similar to a haptic device allowing a form of compliance whose aim is to improve the comfort of the patient by limiting the risks of jolts at the level of the cutting tool without creating a situation of excessive discomfort in the smooth operation. In fact, as already stated, the movements of the cutting tool are modified according to the movements of the stirrup (ET), the latter following the movements of the patient's jaws, in particular at the level of the tooth to be treated. The aim is therefore to slow down and limit the amplitude of any possible movements of the patient's jaws and to significantly reduce any sudden movements, as mentioned above. To do this, the miniature DC motor associated with each of the three joints (RSA9, RSA10 and RSA11) of the mini-arm of the stirrup (ET) is equipped with an internal electrical connection in rheostat (dynamo operation). Thus, once the stirrup is in place and the motors of the main joints of the accessory arm (RS) are blocked, the rheostat operation of the DC motors of the three joints (RSA9, RSA10 and RSA11) of the mini-arm is activated. This preferential arrangement therefore creates a slight constraint which slows down and slows down the movements of the patient's affected jaw and limits their amplitude. This allows the computerized control and monitoring system more time to adjust the tool's trajectories and therefore eliminate jolts. This results in a very significant improvement in cutting precision.

[0043] In another preferred configuration of the invention, the cutting sequence defined by the system consists first of developing steps for the successive cutting of each of the five faces of the tooth - occlusal face, vestibular face, lingual face, mesial face and distal face -, taking into account a predefined edge of 0.14 to 0.22 mm and then proceeding with the actual cutting of each of the faces according to the following protocol: • cutting of the face up to a percentage of 50% to 66% of the complete cutting, • interruption of the cutting (stopping the rotation of the tool, stopping the coolant, clearing the tool by vertical movement over a few millimeters), • comparison of 3D images of actual cutting at the stopping stage with theoretical images at the same stage, • definition of possible tool path corrections, • resumption of cutting up to 100% with consideration of possible cor- ctions.

[0044] All of the basic characteristics detailed above allow the robotic device of the invention to carry out, completely automatically and under good conditions, delicate operations such as cutting teeth directly in the patient's mouth.

[0045] The two preferred configurations explained further provide significant improvements which give the whole a decisive operational safety.

[0046] Following the preceding descriptions detailing the technical characteristics of the invention and the advantages resulting therefrom, the chronology of the actions relating to an intervention on a patient using the robotic device can be specified.

[0047] First of all, it should be recalled that, obviously, the robotic device of the invention can only be put into operation after carrying out a certain number of preliminary actions, actions carried out directly by the practitioner, possibly with the assistance of the prosthetist or with the help of a more or less advanced computer system designed for this purpose, these actions are the following: 1. Patient examination. 2. Taking 3D images of the initial state of the affected area in the patient's mouth with a 3D camera that may be different from the one fitted to the robotic device. 3. Definition of appropriate treatment. 4. Design of the necessary prosthesis and development of the corresponding 3D image files. 5. Definition of the necessary cutting of the tooth and preparation of the corresponding 3D image files, with preparation of the cutting steps for each of the five faces to be cut, each corresponding to the orientation of the cutting plane: occlusal face, vestibular face, lingual face, mesial face and distal face, and finally taking into account the predefined edge of 0.14 to 0.22 mm. The definition is carried out in the form of 3D computer image files allowing control during the operation. 6. Introduction of the set of computer files developed in the previous actions into the control and piloting system of the robotic device which is the subject of the invention.

[0048] At the end of these first steps, or even during their implementation, the practitioner proceeds to install the patient on the chair and position the support structure. Then, once the required position is reached, the locking of the three joints of the support structure is done by a centrally controlled electro-mechanical system. Controlled by the practitioner, this system activates, for each of the joints of the support structure, an indexing pin which fits into a precise bore. The indexing of the support structure thus makes it possible to place the robot-carrying reference sleeve (S3) in four precise predetermined positions: • “MIG” position to treat a tooth in the patient’s lower jaw on the left side: the robot arm holder sleeve of the support structure is placed to the left of the patient’s head and its vertical orientation is such that the tool holder arm is in the low position and the accessory holder arm in the high position. • “MSD” position to treat a tooth in the patient’s upper jaw on the right side: the robot arm holder sleeve of the support structure is placed to the right of the patient’s head and its vertical orientation is such that the tool holder arm is in the high position and the accessory holder arm in the low position. • “MID” position to treat a tooth in the patient’s lower jaw on the right side: the robot arm holder sleeve of the support structure is placed to the right of the patient’s head and its vertical orientation is such that the tool holder arm is in the low position and the accessory holder arm in the high position. • “MSG” position to treat a tooth in the patient’s upper jaw on the left side: the first robot arm holder sleeve of the support structure is placed to the left of the patient’s head and its vertical orientation is such that the tool holder arm is in the high position and the accessory holder arm in the low position.

[0049] The practitioner then places, using the accessory arm of the robot part, the stirrup (ET) on the patient's tooth of choice and takes the first shots of the patient's mouth using the 3D camera (CA) of the robotic device. These images therefore concern the same area as that which was the subject of the first examinations carried out by the practitioner, but they are different since they were taken by a different camera in a different position. It is now a question of establishing a correlation between the first 3D images taken during the initial examination and these new 3D images which will serve as the basis for the entire intervention of the robotic device. This is the reason why, as indicated previously, the part relating to the processing of data in the computer system of the invention is provided with a particular function allowing the conversion of files so that they can be directly used by the piloting and control system of the robot part. Thus, before the start of the cutting operation, the following operations are carried out automatically by the system of the robot part after introduction, in point 6 above, of the files from point 5: 1. Analysis of previously taken 3D image files (point 2 above) of the initial state of the affected area of ​​the patient's mouth. 2. Analysis of 3D image files taken immediately by the robotic device's camera of the same area of ​​the patient's mouth. It should be noted that these images of the same area are, however, different from the previous ones (point 2 above) since the camera is different and its positioning is also different. 3. Development of correlation laws to link the significant points of the two sets of 3D images: images from point 2 above and images from point 8. 4. Analysis of the pre-established 3D image files (point 4 above) defining the cutting of the tooth, images which were previously established from the first file (point 2 above) of the initial state of the patient's mouth. 5. Application of the correlation laws developed previously (point 9) to create a new tooth cutting definition file corresponding to the new 3D image file (point 8) of the initial state of the patient's mouth taken by the 3D camera of the robotic device.

[0050] Finally, the 3D cutting image files having been specifically developed (point 11 above) for the computer system of the robotic device and being in good correspondence with the initial 3D image file (point 5 above) of initial definition of the cutting, the operations on the patient can be carried out. The device's computer system then performs the following operations from this file thus produced (point 11): 1. Determination of the stages of the cutting operation with, for each stage, definition of the trajectories, rotation speeds, torque and forces to be applied to the tool as well as the lubrication / spraying flow rates. 2. Application of these parameters for the actual cutting of the tooth face by face. 3. Monitoring of the cutting of each face of the tooth in real time by means of the 3D camera with comparison at each stage of the real images and the theoretical images previously developed corresponding to the stage considered. At each stage this comparison requires the prior interruption of cutting and lubrication / spraying. 4. In the event of a deviation greater than the predefined maximum deviation: stop cutting and correct the trajectory, rotation speed, torque and forces to be applied to the tool. 5. Resumption of cutting of the affected face with lubrication / spraying. 6. At the end of cutting all the faces, stop cutting and lubrication / spraying, remove the cutting tool, take 3D images of the cutting in its final configuration. 7. Removing the caliper and 3D camera. 8. Folding the two robot arms into their storage configuration.

[0051] Finally, once the intervention is completed, the various databases can be updated by the practitioner using the more or less automated means available in the office.

Claims

Claims

1. Robotic device for carrying out, in the patient's mouth and in a fully automated manner, the tooth cutting operations necessary for the fitting of partial or total prosthetic elements, characterized by the fact that it is made up of all the elements listed below:

1. a base platform (S) placed on the ground on which the patient's chair and the support structure of the robotic assembly are fixed, 2. a swivel chair (F) on which the patient sits in a semi-reclined position, said chair being equipped with: a headrest (F4) with a flap (F5) at the forehead to support the patient's head, 3. a support structure (S) comprising a vertical part (SO), two horizontal segments (SI and S2) connected together by two vertical axis rotoidal joints (SA01 and SA12) without tilting clearance, each provided with an internal locking device actuated directly by the practitioner, and at the end of which is mounted a short vertical sleeve (S3) fixed to the end of the second segment of said support structure by a horizontal axis rotoidal joint (SA23) and which can pivot from one vertical position to another at 180° depending on whether the operation on the patient concerns a tooth of the upper jaw or the lower jaw (the mandible), said support structure (S) with its short pivoting vertical sleeve (S3) constituting the extremely rigid, precise and stable base serving as material support for the orthonormal reference system with three coordinate axes (x, y, z), called the “machine coordinate system”, for the rigorous control of the movement trajectories,positions, orientations, speeds and forces of all the elements of the robotic part of the device, the origin 0, called “zero machine”, of this general orthonormal system being materialized by the midpoint (Orobot) of the short vertical sleeve (S3) at the end of the support structure (S), 4. a so-called robotic part consisting of two robot arms (RO and RS), each fixed to one end of the short vertical sleeve (S3) of the support structure (S) by a rotoidal joint with a vertical axis (RSA1 and ROA1) and comprising two segments, the first segment of each arm (RSS1 and ROSI) being connected to the previous joint by a rotoidal joint with a horizontal axis (RSS1 and ROSI) and the second segment of each arm (RSS2 and ROS2) being connected to the first also by a rotoidal joint with a horizontal axis (RSA3 and ROA3), the support block (PS and PO) of the functional member(s) being connected to the second segment by a cross-type joint (RS A4 and RO A4), one of the two robot arms constituting the manipulator of the tooth cutting tool with its lubrication / spraying and lighting systems and the other robot arm being the manipulator of the accessories that are the 3D camera and the stirrup which is positioned on the patient's tooth concerned or a neighboring tooth,the central point of this bracket constituting the material support of the origin called “zero part” of the second three-axis coordinate system called “part coordinate system” whose recorded movements corresponding to the movements of the patient allow the control and monitoring system to modify the trajectories of the cutting tool according to these movements, 5. the general computer system for piloting and controlling the robotic part in the form of a desk-desk placed next to the assembly consisting of the platform, the patient's chair and the support structure with the robotic part and including the computer integrating the various computer programs which contain • necessary information such as 3D images of the initial state of the tooth, 3D images of the tooth in the different stages of cutting, • the control and monitoring instructions for the trajectories of the cutting tool (OT) at the end of the tool-holder arm (RO) from the position of the stirrup (ET), previously placed on the patient's tooth by the practitioner by controlling the accessory-holder arm (RS), said computer system also including the interfaces (keyboard, mouse and others) and the screens allowing the display of 3D images and information necessary to allow the practitioner to intervene and monitor the intervention and finally including all the necessary electrical, electronic and computer connections.

2. Robotic device for carrying out, in the patient's mouth and in a fully automated manner, the tooth cutting operations necessary for the fitting of partial or total prosthetic elements according to claim 1 characterized in that, in order to avoid any collision between the elements constituting the tool-carrying arm (RO) and the elements constituting the accessory-carrying arm (RS), specific software is incorporated into the system to carry out constant control by 3D imaging of the respective positions of the different elements of each of the two arms, said software stopping any movement of an element of a moving arm which could lead, due to its imposed trajectory, to a collision with an element of the other arm.

3. Robotic device for carrying out, in the patient's mouth and in a fully automated manner, the tooth cutting operations necessary for the fitting of partial or total prosthetic elements according to claim 1 or 2, characterized in that the robotic part consisting of the accessory-holder arm (RS) and the tool-holder arm (RO) can be placed in four different configurations depending on the location of the patient's tooth to be treated: • configuration for an intervention on a tooth in the left part of the patient's lower jaw (so-called “MIG” configuration), • configuration for an intervention on a tooth in the right part of the patient's upper jaw (so-called “MSD” configuration), • configuration for an intervention on a tooth in the right part of the patient's lower jaw (so-called “MID” configuration),• configuration for an intervention on a tooth on the left side of the patient’s upper jaw (so-called “MSG” configuration).,

4. Robotic device for performing, in the patient's mouth and

5. in a fully automated manner, the tooth cutting operations necessary for the installation of partial or total prosthetic elements according to any one of the preceding claims, characterized in that the part relating to the processing of data in the computer system of the invention is provided with a particular function allowing the conversion of files so that they can be directly used by the control and monitoring system of the robot part, said function consisting of: • analyze the 3D image files of the initial state of the relevant area of ​​the patient's mouth, images having been taken by a camera different from that of the robotic device of the invention, • analyze the 3D image files of the same area of ​​the patient's mouth taken immediately by the camera of the robotic device of the invention, 3D images however different from the previous ones since taken by two different cameras, • develop correlation laws to link the significant points of the two previous sets of 3D images of the relevant area of ​​the patient's mouth, • analyze the pre-established 3D image files defining the tooth cutting, images which were previously established from the first file of the initial state of the patient's mouth, • apply the correlation laws developed previously to create a new tooth cutting definition file corresponding to the new 3D image file of the initial state of the patient's mouth taken by the 3D camera of the robotic device of the invention. Robotic device for carrying out, in the patient's mouth and in a fully automated manner, the tooth cutting operations necessary for the fitting of partial or total prosthetic elements according to any one of the preceding claims, characterized in that the mini-arm with three rotoid joints (RSA9, 10, 11) at the end of which is fixed the stirrup (ET), placed on the patient's tooth concerned or on a neighboring tooth, is equipped with a device intended to slow down and limit

6. the amplitude of any movements of the patient's jaws and also to significantly reduce jolts or sudden movements, a device which consists of equipping the miniature direct current motor associated with each of these three joints with an internal electrical rheostat connection (dynamo operation), said rheostat connection being activated from the start of cutting in order to create a slight constraint in the movements of the stirrup, a constraint which brakes and slows down the movements of the patient's jaw concerned and limits its amplitude. Robotic device intended for interventions on patient teeth with a view to producing dental implants according to any one of the preceding claims, characterized in that the voluntary interruption of the intervention by the practitioner or a cut-off of the electrical power supply to the system, in particular by one of the three emergency stop buttons - one on either side of the patient's chair and one at the practitioner's desk - causes the relaxation of a small torsion return spring fixed at the level of the articulation of the tool holder which makes it possible to ensure, for safety reasons, a very slight vertical clearance of the tool, between 2 and 5 mm, from the patient's tooth.

Images