Test bench and method for mechanical testing of a subperiosteal implant

Abstract

A test bench (100) for mechanical testing of a subperiosteal implant (810), wherein the subperiosteal implant (810) is provided with at least one superstructure, the test bench (100) comprising: a machine frame (200), a mandibular model (800) to which a subperiosteal implant (810) is fixable, and at least one force measuring unit (700) that is connected at one end to a load-bearing plate (710) fixed to the machine frame (200) and can be releasably connected at its other end to at least one test location (P) of the subperiosteal implant (810) for force measurement. The test bench (100) is characterised by further comprising a first shaft (613) that is rotatably connected to the machine frame (200) via at least a first bearing (612) such that it defines a first rotational axis (614), a second shaft (623) that is rotatably connected to the machine frame (200) via at least a second bearing (622) such that it defines a second rotational axis (624), wherein the mandibular model (800) is attached to the first shaft (613) and to the second shaft (623) at two, first and second, mandible head portions (801, 802) thereof for rotation about the first rotational axis (614) and the second rotational axis (624), at least one control and command unit (300) that is mounted on the machine frame (200) and has at least two, first and second, pneumatic cylinders (400, 500) provided with a first and a second piston rod (410, 510), wherein the at least two, first and second, pneumatic cylinders (400, 500) are arranged above the mandibular model (800), and wherein the control and command unit (300) is in operative connection with the first and second pneumatic cylinders (400, 500) such that it is able to exert a force of a given magnitude on the first and second piston rods (410, 510) to move them in a vertical direction, at least two, first and second, displacement measuring units (460, 560) mounted on the first and second pneumatic cylinders (400, 500) such that they are able to measure the vertical-direction displacement of the first and second piston rods (410, 510) of the first and second pneumatic cylinders (400, 500); at least two, first and second, resilient members (450, 550) with a strap-like configuration that are connected to the respective lower ends of each of the first and second piston rods (410, 510) by means of a first and a second connection member (430, 530) such that the first and second resilient members (450, 550) support the mandibular model (800) by forming a loop around both sides thereof; wherein the at least one, first and second resilient members (450, 550) are operatively connected to the control and command unit (300) by way of being connected to the first and second piston rods (410, 510), and thus they are able to apply a tensile load to the mandibular model (800). The method according to the invention is carried out applying a system according to the invention.

Description

[0001] Test bench and method for mechanical testing of a subperiosteal implant

[0002] Technical field

[0003] The invention relates to a test bench and a method suited for mechanical testing of a subperiosteal implant together with a superstructure.

[0004] Background art

[0005] In patients with tumours or bone deficits, the bone region to be removed or already missing can be so large that the remaining bone mass is not able to provide sufficient support to the soft tissues. For the correction of such large-sized bone deficits, subperiosteal implants are conventionally applied in patients in the case of whom bone replacement is not possible or not recommended. One type of subperiosteal implant is constituted by dental implants that, when placed under the gum, are able to correct the deficits of the jaw bones. Correction of the bone deficits of the lower jaw, i.e., the mandible, is especially of crucial importance, because mastication places much larger loads on the lower teeth compared with the upper teeth. Dental subperiosteal implants are provided with at least one superstructure and typically a plurality of superstructures, the superstructures essentially being elements firmly secured to the subperiosteal implant by bolts or adhesive bonding that are located above the gum surface, and are thus able to support various dental fittings, such as separate crowns or bridges. These dental implants are therefore such tailor- made medical devices that are configured to conform to the individual anatomical conditions of the patients, and consequently their mechanical testing must also be performed on an individual basis.

[0006] The precise design and implementation of subperiosteal dental implants and the attached superstructures is of utmost importance because subperiosteal implants are inserted under the gum, so the subperiosteal implant and its superstructure can be repaired, and their attachment errors can be corrected only through an invasive intervention. Furthermore, it is absolutely necessary to ensure that the relative positioning of the implant and the superstructure is accurate, and to adapt their optimal load-bearing capacity to the anatomical conditions, especially to the anatomical mastication / bite characteristics of the patient, because failing to do so may later on result in the inflammation of soft and hard tissues, further bone loss, and potentially in the implant being displaced or coming loose. The prior art includes several methods for testing the properties of subperiosteal implants and superstructures. In one of the widely applied methods, an impression of the patient’s mandible is taken in one of several ways; the impression can be digitised, and thereafter a subperiosteal implant fitting into the patient’s jaw and the appropriate superstructure attached to it can be designed in a customised manner with the help of computer software. Using simulations, this mandibular model can be subjected to various load tests in the computer program. However, computerised finite element analysis has a number of disadvantages. Different parameter settings and constraints must be applied for each individual mandibular model. Also, finite element analysis is performed under ideal circumstances, wherein only simplified, inaccurate mandibular models can be defined. The analysis of complex mandibular models may require large computing capacity, and more complex models may require excessive amounts time for running the various tests. In addition, in the computer environment it is only possible to reproduce the mechanism of mastication and biting in concert with anatomical conditions in an approximative manner.

[0007] According to the prior art, the problems arising in connection with the abovedescribed method can be solved applying bespoke measuring apparatuses, with the help of which efforts can be made to map the processes of biting and mastication true to reality by testing the implants, superstructures, and optionally, dental fittings.

[0008] The Korean patent KR101709166 discloses a loading apparatus for a dental implant having a superstructure, which also takes into consideration the movement of the mandible during testing. The technical solution according to the invention is suited for testing the loading of a dental fitting inserted into the jaw by applying loads to the superstructure of the implant in the forward, backward, downward, upward, right, and left directions; however the mechanism is only able to apply this load at a single point, and it is not able to reproduce the entirety of the forces directed at the lower jaw, and thus it is incapable of testing a subperiosteal implant. Although this technical solution is able to apply forces in six different directions, it achieves that with the help of a rigid member that does not correspond to the process of biting and mastication, since the role of the mandibular muscles and joints is completely disregarded.

[0009] The Chinese patent document CN106404231 discloses a measuring device that allows for performing personalised mechanical tests of the lower jawbone. The objective of the invention is testing a lower jaw model that has a material composition corresponding to the composition of real bones. To this end, the measuring device comprises a support structure to which the lower jaw (mandibular) model is attached through a unit adapted to reconstruct muscle movements, wherein the muscles attached to the mandibular model are implemented as one-dimensional springs which are connected at one end to portions of the lower jaw model corresponding to muscle attachment points, and at the other end, via a rigid guide, to mechanisms pulling the mandibular model upward. During the operation of the apparatus, the mandibular model attached to the apparatus in such a manner is pulled against a loading mechanism that substitutes for the upper jaw, while the strain of the mandibular model is measured by at least one strain gauge unit at the given location of the mandibular model.

[0010] Although the technical solution according to the Chinese patent document attaches the mechanism reconstructing muscle movement to the mandibular model via spring elements, it does so at specific points / locations, with the spring elements being attached via rigid guide elements to the mechanism adapted for pulling the mandible upwards, and thereby it is not possible to accurately reconstruct the free movements during mastication and biting. Furthermore, the strain gauge unit is only able to measure the strain of the mandibular model at given locations, so the measurement system does not give any information on the loads to which the superstructures optionally built into the mandibular model are subjected. The measurement system also does not allow for applying loads to both sides of the mandibular model independently, so the mechanical effects of asymmetrical bite and mastication cannot be tested.

[0011] Disclosure of the invention

[0012] The objective of the invention is to eliminate the above-mentioned problems by providing a test bench that is able to perform mechanical tests of subperiosteal implants together with their superstructures such that the subperiosteal implant with its superstructure is loaded in accordance with the real movement of the mandibular joint, with the potential deformations of the mandibular model being measured by measuring units.

[0013] Our objectives have been fulfilled by providing the test bench according to claim 1 and the method for operating the test bench according to claim 10. Preferred embodiments of the test bench and method according to the invention are defined in the dependent claims. Brief description of the drawings

[0014] In the following, the invention will be described in detail referring to the accompanying drawing. In the drawing:

[0015] - Fig. 1 illustrates in perspective view the structural configuration of a test bench according to the invention,

[0016] - Fig. 2 illustrates in perspective view a preferred embodiment of the machine frame of a test bench according to the invention,

[0017] - Fig. 3 illustrates in perspective view an embodiment of the control and command unit of a test bench according to the invention,

[0018] - Fig. 4 illustrates in perspective view a preferred embodiment of the force measuring unit of a test bench according to the invention,

[0019] - Fig. 5 illustrates in perspective view the elements of a test bench according to the invention adapted for moving a mandibular model, as seen from the back; and

[0020] - Fig. 6 is a flow diagram illustrating the major steps of a preferred embodiment of a method according to the invention.

[0021] Preferred embodiments of the invention

[0022] As can be seen in Fig. 1 , the test bench 100 according to the invention comprises a machine frame 200 for retaining and positioning the various structural components. The machine frame 200 according to Fig. 1 is depicted in detail, without the components mounted on it, in Fig. 2. In a preferred embodiment of the test bench 100 according to the invention, the machine frame 200 according to Fig. 2 preferably comprises

[0023] - a horizontally placed bottom plate 210,

[0024] - a back plate 220 mounted vertically on the bottom plate 210,

[0025] - an upper plate 230 mounted horizontally on the upper portion of the back plate 220, and

[0026] - a middle plate 240 that is mounted between the bottom plate 210 and the upper plate 230 in a horizontal direction relative to the back plate 220.

[0027] To improve rigidity, the machine frame 200 according to Fig. 2 further comprises

[0028] - a first stiffening member 250 attached to the middle plate 240 and to the upper plate 230, - a second stiffening member 260 attached to the back plate 220 and to the first stiffening member 250, and

[0029] - respective pairs of ribs 270, 290 for stiffening the bottom 210, back 220, and upper plates 230 with respect to each other.

[0030] To improve stability, the machine frame 200 according to Fig. 2 further comprises four adjustable legs 280 that are arranged symmetrically at the comers of the bottom plate 210. By appropriately adjusting the legs 280, the irregularities of the floor surface can be eliminated and the machine frame 200 can be levelled.

[0031] The components of the machine frame 200 can be interconnected releasably, for example by means of pins, bolts, and nuts, and / or permanently, for example by welding. In this preferred embodiment of the test bench 100 according to the invention, the height of the machine frame 200 is approximately 38 cm, its width is approximately 28 cm, and its depth is approximately 23 cm, but it can also be made with different dimensions provided it is able to retain the components mounted on the machine frame 200.

[0032] The test bench 100 according to the invention further comprises a control and command unit 300 that is expediently arranged on the upper plate 230 as it can be seen in the preferred embodiment according to Fig. 1. The control and command unit 300 of the test bench 100 is preferably implemented as a pneumatic unit.

[0033] Fig. 3 depicts in detail a pneumatic control and command unit 300 that essentially contains three main parts. One of the main parts of the pneumatic control and command unit 300 according to Fig. 3 is an air preparation unit 310 that is adapted for supplying the test bench 100 with an appropriate amount of compressed air, optionally filtered air, of an appropriate pressure and quality. The test bench 100 is able to operate properly already at a pressure of about 5 bar, but for unhindered and balanced operation it is recommended to keep the input pressure preferably in the range of about 7 bar to about 8 bar, particularly preferably at a pressure of 6 bar. The air preparation unit 310 may comprise:

[0034] - a manual on-off valve 311 applicable for pressurising the control and command unit 300;

[0035] - a pressure control element 312,

[0036] - a filter 313, and - a soft starter valve 314 for slowly increasing pressure in the control and command unit 300, thereby providing a smooth operation.

[0037] The second main part of the control and command unit 300 is at least one manual operation unit that is utilised only in case of manual operation, for example in case of a failure of the automatic control unit. The manual operation unit can be used for manually adjusting the pressure in a first pneumatic cylinder 400 and a second pneumatic cylinder 500; the first and second pneumatic cylinders 400, 500 are shown in Figs. 1 and 5. In a preferred embodiment of the test bench 100, two manual actuation units are built into the control and command unit 300 according to Fig. 3; the units can be utilised for separately operating the first and the second pneumatic cylinder 400, 500. The two manual operation units are preferably implemented as a first manual pressure control valve 320 equipped with a pressure gauge 321 and a second manual pressure control valve 330 equipped with a pressure gauge 331 .

[0038] Further, the third main part of the control and command unit 300 is an automated operation unit depicted in Fig. 3 that is preferably configured to include components controllable by a programmable logical controller, and comprises at least

[0039] - a first proportional valve 340 controllable by electronic signals that is adapted for adjusting the pressure building up inside the first pneumatic cylinder 400 such that the magnitude of the tensile forces can be adjusted dynamically;

[0040] - two first solenoid valves 360 applicable for controlling the movement of the first pneumatic cylinder 400,

[0041] - a second proportional valve 350 controllable by electronic signals that is adapted for adjusting the pressure building up inside the second pneumatic cylinder 500 such that the magnitude of the tensile forces can be adjusted dynamically;

[0042] - two second solenoid valves 370 applicable for controlling the movement of the second pneumatic cylinder 500.

[0043] In the case of both manual and automated operation, the tensile force values can be adjusted by modifying the pressure in the first and the second pneumatic cylinders 400, 500 that are not shown in Fig. 3. The pressure can preferably be adjusted in the range of about 0 to 5 bar utilising the first and second manual pressure control valves 320, 330 and / or the first and second proportional valves 340, 350. Thereby, the tensile forces applied by the first and second pneumatic cylinders 400, 500 can be adjusted separately, in the range of about 0 N to about 900 N, preferably in the range of about 200 N to about 850 N.

[0044] Certain components of the control and command unit 300 are operatively connected to the first and second pneumatic cylinders 400 and 500 for example through quick connector elements, manifold members, shut-off / check valves and interconnecting pipes that cannot be seen in the figures; these components and the way they are assembled is well known to the skilled person. In addition to applying pneumatic control, the control and actuation elements making up the control and command unit 300 can also be operated in alternative ways, for example hydraulically, mechanically, or electrically.

[0045] The test bench 100 according to the invention may preferably comprise a control cabinet that is in connection with the control and command unit 300. The control cabinet houses the components required for automated operation, it is essentially a conventional control cabinet known from prior art, so it has not been included in the drawings. The control cabinet preferably comprises

[0046] - a programming unit, for example a computer, for creating and / or modifying the system program adapted for operating the test bench 100;

[0047] - at least one programmable logical controller that may comprise at least

[0048] - an input unit through which the programmable logical controller is connected to the input components, such as for example at least one force measuring unit 700, first displacement measuring unit 460 and a second displacement measuring unit 560;

[0049] - an output unit through which the programmable logical controller is in connection with the output components, such as for example the first and second solenoid valves 360, 370 and the first and second pneumatic cylinders 400, 500;

[0050] - a program memory for storing the system program that operates the system;

[0051] - a data memory;

[0052] - a central logical and processing unit adapted for running the program loaded in the program memory, and for providing the control signals; - a communication unit adapted for interconnecting the plurality of programmable logical controllers.

[0053] One side of the first pneumatic cylinder 400 and the second pneumatic cylinder 500 of the test bench 100 illustrated in Fig. 1 is expediently connected to the upper plate 230 such that the first piston rod 410 of the first pneumatic cylinder 400 and the second piston rod 510 of the second pneumatic cylinder 500 are able to move vertically in the direction of the bottom plate 210. The first and second pneumatic cylinders 400 and 500 are separately connected in an operative manner to the control and command unit 300, whereby the parameters of the first and second pneumatic cylinders 400 and 500, such as the position of the first and second piston rods 410, 510, their position, speed and direction of their vertical motion, and the magnitude of the force exerted by them, can be controlled independently.

[0054] The first and the second pneumatic cylinders 400 and 500 preferably comprise respective first and second guided piston rods 410 and 510, whereby the first and second piston rods 410, 510 can be prevented from rotating, swaying, or even inclining during operation.

[0055] Displacement measuring units can be primarily utilised for measuring the stroke length of the first and second pneumatic cylinders 400 and 500, as it is illustrated in Fig. 1 , said displacement measuring units can be for example first and second linear displacement measurement units 460, 560 mounted on the first and second pneumatic cylinders 400, 500; alternatively, these units can be configured integrally with the first and second pneumatic cylinders 400, 500.

[0056] As can be seen in Fig 1 and Fig. 5, the free end of the first piston rods 410 protruding from the first pneumatic cylinder 400 can be provided with a first support plate 420, and likewise the free end of the second piston rods 510 protruding from the second pneumatic cylinder 500 can be provided with a second support plate 520.

[0057] In the preferred embodiment according to Fig. 5, the first support plate 420 and the second support plate 500 comprise a first connection member 430 and a second connection member 530, respectively. In this preferred embodiment of the test bench 100, the first and second connection members 430, 530 have a hook-like configuration, whereby they encompass a first resilient member 450 and a second resilient member 550, respectively, such that said resilient members suspended them.

[0058] The first resilient member 450 is configured such that it is connected at one end to the first connection member 430 and at the other end to an end of a mandibular model 800. In turn, the second resilient member 550 is configured such that it is connected at one of its ends to the second connection member 530 and at its other end to the other end of the mandibular model 800.

[0059] The mandibular model 800 is movable by means of the first and second pneumatic cylinders 400, 500 via the first and second support plates 420, 520, the first and second connection members 430, 530, and the first and second resilient members 450, 550.

[0060] In a preferred embodiment of the test bench 100, the first and second resilient members 450 and 550 are implemented as flat rubber brackets that are attached by means of bolts and / or adhesive to the side of the mandibular model 800.

[0061] In another preferred embodiment of the test bench 100, the first and second resilient members 450 and 550 are implemented in particular as reinforced flexible polyurethane straps. As can be seen in Fig. 5, in such a case the first resilient member 450 implemented as a polyurethane strap is looped along a first contact portion 451 formed at the bottom portion of the mandibular model 800, while the second resilient member 550 implemented as a polyurethane strap is looped along a second contact portion 551 formed at the bottom portion of the mandibular model 800. such that the first and second resilient members 450 and 550 are able to adapt, i.e. , they are able to freely move corresponding to the potential spatial movements of the mandibular model 800, thereby not limiting the forces acting on the mandibular model 800. As can be seen in Fig. 5, a respective pair of limiting elements protruding from the bottom portion of the mandibular model 800 can be expediently arranged at each of the first and second contact portions 451 and 551. which prevent the first and second resilient members 450 and 550 from sliding along the mandibular model 800 during the operation of the test bench 100.

[0062] For tests performed with the test bench 100, mandibular models 800 of distinct types can be applied:

[0063] - on the one hand, a type of mandibular model 800 having a generic configuration, to which the subperiosteal implant 810 to be tested, or at least one superstructure can be attached firmly; or

[0064] - on the other hand, a customised mandibular model 800 that represents the unique anatomical features of an individual, and already includes the bone deficit due to which the subperiosteal implant 810 is required. The mandibular models 800 can be preferably made of materials having such density that is essentially equal to the density of a human mandible, particularly preferably essentially equal to the density of the given individual’s mandible. The mandibular model 800 can be preferably also configured such that it comprises on the outside a harder portion corresponding to the harder, compact bone portion and comprises in its inside a softer portion that may correspond to the softer, cancellous bone portion. The mandibular model 800 may be made for example of aluminium, the mandibular model 800 preferably being made of a semi-rigid material that deformable under the force applied by the test bench 100, for example plastic and / or resin.

[0065] A subperiosteal implant 810 can be attached to the mandibular model 800 together with at least one superstructure. Subperiosteal implants 810 are typically larger-sized, so they may be equipped with more than one superstructures. The mandibular model 800 may optionally be provided with a plurality of subperiosteal implants 810, each of which may comprise at least one superstructure. The subperiosteal implant 810 attachable to the mandibular model 800 with a superstructure can be provided with a superstructure by one of prior art methods known in the field; such a method is obvious to the skilled person, so in the following an exemplary, customised design process is described:

[0066] - a CT scan is taken of the mandible of a patient having a bone deficit;

[0067] - a three-dimensional model of the mandible and the bone deficit inside the mandible is determined, and based on the model, a mandibular model 800 having a bone deficit is produced, and a subperiosteal implant 810 fitting into the bone defect is also made;

[0068] - based on the dimensions of the bone deficit, the number and position of the superstructures on the subperiosteal implant 810 are determined, taking into consideration the dental prosthesis to be supported by them;

[0069] - the mandibular model 800 including the bone defect, the subperiosteal implant 810 and the at least one superstructure attachable to it are made using an appropriate material or materials, and the superstructure or superstructures are firmly attached to the subperiosteal implant 810.

[0070] The method according to the invention can be performed with the test bench 100 according to the invention on the mandibular model 800 and subperiosteal implant 810 comprising at least superstructure assembled in such a manner. As can be seen in Figs. 1 and 5, the mandibular model 800 is rotatably connected to the machine frame 200 with the help of a first and a second articulated mechanism 610, 620. As it is depicted in Fig. 5, this is implemented by attaching the two - first and second - mandible heads 801 , 802 of the mandibular model 800 to the machine frame 200 with the help of two - first and second - articulated mechanisms 610, 620 such that under the effect of identically operated first and second pneumatic cylinders 400, 500, the left and right sides of the mandibular model 800 are rotated by an identical amount in a first and a second direction of rotation 615 and 625, while under the effect of differently operated first and second pneumatic cylinders 400, 500 they are rotated by different amounts in the first and second directions of rotation 615, 625. In this preferred embodiment of the test bench 100, in order to provide symmetrical and / or asymmetrical rotatability (i.e., rotatability by the same or different amounts) of the mandibular model 800, a first articulated mechanism 610 is connected to a first mandible head 801 of the mandibular model 800, which mechanism may comprise

[0071] - a first support member 611 attached to the middle plate 240 of the machine frame 200,

[0072] - a first shaft 613 that is connected to the first support member 611 through at least one first bearing 612, preferably a first pair of bearings 612, thereby defining a first rotational axis 614.

[0073] The first mandible head 801 of the mandibular model 800 is attached to the first shaft 613 such that the mandibular model 800 can be rotated about the first rotational axis 614.

[0074] In turn, the second head portion 802 of the mandibular model 800 is connected to a second articulated mechanism 620 that may comprise

[0075] - - a second support member 621 attached to the middle plate 240 of the machine frame 200,

[0076] - - a second shaft 623 that is connected to the second support member 621 through at least one second bearing 622, preferably a second pair of bearings 622 such that it defines a second rotational axis 624 that is expediently coaxial with the first rotational axis 614.

[0077] The second head portion 802 of the mandibular model 800 is connected to the second shaft 623 such that the mandibular model 800 is rotatable about the second rotational axis 624. The first and second bearings 612 and 622 are preferably self- aligning ball bearings, so both sides of the mandibular model 800 may undergo deformation relative to each other and may also be rotated at an angle similar to the workings of the mandibular joints.

[0078] As can be seen in Fig. 1 , the test bench 100 according to the invention preferably further comprises at least one load-bearing plate 710 that is attached replaceably to the bottom of the middle plate 240 of the machine frame 200, for example by means of pins and bolts.

[0079] At least one force measuring unit 700 is mounted on the bottom portion of the load-bearing plate 710; in the embodiment according to Fig. 1 , four force measuring units 700 are mounted thereon. For different tests, depending on the configuration and dimensions of the load-bearing plate 710, preferably a different number of force measuring units 700 can be attached thereto at distinct positions. The ability to replace the load-bearing plate 710 together with the at least one force measuring unit 700 allows the speedy preparation of various tests, because, for example, during the operation of the test bench 100, the position of the one or more force measuring units 700 can be adjusted on a load-bearing plate that is currently not in use.

[0080] In Fig. 4 there can be seen the at least one force measuring unit 700 according to the invention, comprising:

[0081] - a housing 710 that can be detachably connected to the load-bearing plate 710, for example by means of a pin and two bolts;

[0082] - a load cell 720 that is arranged in the housing 710 and is in wired connection to a data processing and control system;

[0083] - a loading pin 730 that is in operating connection with the load cell 720 and has an end that protrudes from the housing 710 and can be brought into contact with the mandibular model 800 and / or with the subperiosteal implant 810, preferably at least one superstructure thereof, at a predetermined test location P.

[0084] In the course of the various tests, as a result of rotating the mandibular model 800, the loading pin 730 of the at least one force measuring unit 700 can be brought into contact with a given portion of the mandibular model 800, preferably with the at least one superstructure of the subperiosteal implant 810 retained therein, at a predetermined test location P. Thereby, the first and second pneumatic cylinders 400, 500 are able to apply load to the mandibular model 800 via the loading pin 730 of the at least one force measuring unit 700 such that the loading pin 730 exerts such a force on the load cell 720 that is equal to the load applied to the mandibular model 800, and thus the magnitude of the forces exerted by the first and second pneumatic cylinders 400, 500 can be determined.

[0085] Depending on the number of force measuring units 700 mounted on the loadbearing plate 710, it is possible to apply loads to and perform measurements on the mandibular model 800 at various mutually independent test locations P.

[0086] In the preferred embodiment of the test bench 100 according to Fig. 1 the loadbearing plate 710 comprises four force measuring units 700 operating completely independently of each other.

[0087] The data processing and control system of the test bench 100 according to the invention (not shown in the drawing) is adapted for receiving, processing, and evaluating the data coming from the at least one force measuring unit 700, the displacement measuring units 460, 560, and the control and command unit 300. The data processing and control unit preferably comprises

[0088] - a data storage module for storing measurement and user data,

[0089] - a computation module adapted for performing automated analysis and processing of the measurement data, and

[0090] - a display module adapted for displaying raw measurement data and / or the computed values, for example in the form of 3D-models, tables, and graphs.

[0091] The data processing and control system preferably further comprises a control module, with the help of which the user can adjust the operating parameters of the test bench 100, such as the speed of the first and second pneumatic cylinders 400, 500, the magnitude of the tensile force exerted by them, the asymmetric movements of the first and second piston rods 410, 510, and the movement of the mandibular model 800.

[0092] In the following, the method for operating the test bench 100 according to the invention will be described in detail referring to Fig. 6.

[0093] In the first step S10 of the method, a mandibular model 800 is provided, with the subperiosteal implant 810 provided with at least one superstructure being secured to it, followed by securing the mandibular model 800 assembled this way to the machine frame 200 on the one hand with a first and a second articulated mechanism 610, 620, and on the other hand with a first and a second resilient member 450, 550.

[0094] In the subsequent step S20 forces of given magnitude are applied to the first pneumatic cylinder 400 and the second pneumatic cylinder 500 utilising a control and command unit 300, as a result of which first and second piston rods 410, 510 of the pneumatic cylinders move upward.

[0095] In step S30, as a result of moving upward the first and second piston rods 410 and 510 as according to step S20, the first and second resilient members 450, 550, and thereby the mandibular model 800, are pulled upward.

[0096] In step S40, by pulling the first and second resilient members 450, 550 upwards as according to step S30, the mandibular model 800 is rotated about a first rotational axis 614 and a second rotational axis 624 in a first direction of rotation 615 and in a second direction of rotation 625.

[0097] In step S50, the upward displacement of the first piston rod 410 and the second piston rod 510 is measured utilising at least a first displacement measuring unit 460 and a second displacement measuring unit 560.

[0098] In step S60, the subperiosteal implant 810 provided with at least one superstructure secured onto the mandibular model 800 is pushed against the at least one force measuring unit 700 at at least one test location P by means of pulling upward the at least two, first and second, resilient members 450, 550 as according to step S30, thereby transferring the applied force from the first and second pneumatic cylinders 400, 500 to the at least one test location P, wherein the test location P coincides with the position of the at least one superstructure.

[0099] In step S70, the magnitude of the force applied at the at least one test location P is measured with the at least one force measuring unit 700.

[0100] In an expedient variant of the method according to the invention, the magnitude of the deformation of the mandibular model 800 is determined based on the upward displacement of the first and second piston rods 410, 510 measured by the at least two, first and second, displacement measuring units 460, 560 as according to step S50.

[0101] In another expedient variant of the method according to the invention, steps S20-S70 are performed essentially simultaneously. By carrying out steps S20-S70 essentially simultaneously it is meant that they are performed simultaneously as limited by the time delay of signal transmission between the components involved in steps S20-S70.

[0102] In a further expedient variant of the method according to the invention, subsequent to step S70, in step S80 the application of a force of a given magnitude to a first and a second pneumatic cylinder 400, 500 is terminated by the control and command unit 300, as a result of which the first and second piston rods 410, 510 move downward.

[0103] In step S90, the at least two, first and second, resilient members 450, 550, and thereby the mandibular model 800, are lowered by means of moving downward the first and second piston rods 410, 510 as according to step S80.

[0104] In step S100, by lowering the at least two, first and second, resilient members 450, 550 as according to step S90, the mandibular model 800 is rotated about a first rotational axis 614 and about a second rotational axis 624 in a direction opposite the first direction of rotation 615.

[0105] In step S110, the downward displacement of the first piston rod 410 and the second piston rod 510 is measured utilising at least two displacement measuring units, i.e. a first displacement measuring unit 460 and a second displacement measuring unit 560.

[0106] In step S120, by lowering the at least two, first and second, resilient members 450, 550 as according to step S90, the subperiosteal implant 810 provided with at least one superstructure secured onto the mandibular model 800 is freed up, such that a spacing of a given size is formed between it and the at least one force measuring unit 700.

[0107] In an expedient variant of the method according to the invention, steps S80- S120 are performed essentially simultaneously. By performing the steps “essentially simultaneously” it is meant that they are carried out simultaneously as interpreted according to steps S20-S70.

[0108] In another expedient variant of the method according to the invention steps S20- S70 and steps S80-S120 are performed multiple times. By performing these operational steps multiple times, we essentially model the process of mastication, while by carrying out steps S20-S70 a single time the process of biting can be modelled for the mandibular model 800 under test.

[0109] In further expedient variants of the method according to the invention, in step S20b (not shown in Fig. 6) forces of different magnitude are applied to the first and the second pneumatic cylinders 400, 500 with the control and command unit 300, as a result of which the piston rods 410, 510 of said cylinders are displaced upward by different amounts, which is followed by performing steps S30-S70 with regard to step S20b. Performing the method according to the invention in such a manner essentially allows us to model a bite process that has unequal / different forces at both sides of the mandibular model 800, which can be preferable for example for modelling unilateral bite, grinding, or other, predominantly joint-related conditions affecting the mandible.

[0110] In a further expedient variant of the method according to the invention, steps S20b-S70 are performed essentially simultaneously. By performing the steps “essentially simultaneously” it is meant that they are performed in a manner set forth above.

[0111] In a further preferred embodiment of the invention, steps S80-S120 are carried out after performing steps S20b-S70. Preferably, steps S80-S120 are performed essentially simultaneously, the term “essentially simultaneously” being interpreted as set forth above. In a preferred embodiment of the invention, steps S20b-S70 and steps S80-S120 are performed multiple times. Performing these operational steps of the method multiple times allows the modelling of an asymmetrical mastication process, which can be particularly useful for testing for potential deformations of the mandibular model 800, because it is expected that an imperfect bite will, at least in the long term, cause deformity.

[0112] In an expedient variant of the method according to the invention, a force between approximately 0 and 900 N, particularly between approximately 200 N and 850 N is applied to the subperiosteal implant 810 provided with at least one superstructure.

[0113] In the following, examples of operating the test bench 100 are set forth for static and dynamic tests. In an exemplary test case, the test bench 100 according to Fig. 1 is applied for testing static and dynamic properties of the subperiosteal implant 810 provided with a superstructure.

[0114] In a first cycle, the mandibular model 800 is slowly pulled upward by the first and second pneumatic cylinders 400 and 500 until it reaches a zero position, where the subperiosteal implant 810 comes into contact with the four force measuring units 700. From then on, the first pneumatic cylinder 400 is put under a constant load of 900 N, the second pneumatic cylinder 500 being instantaneously subjected to a load of 750 N. The loads are sustained for 5 seconds, followed by removing the loads such that the subperiosteal implant 810 becomes spaced apart from the force measuring units 700 by a given distance.

[0115] In a second cycle, the mandibular model 800 is suddenly pulled upward by the first and second pneumatic cylinders 400 and 500 applying the maximum force of 900 N such that the subperiosteal implant 810 provided with a superstructure comes into contact with the force measuring units 700 suddenly, like a blow.

[0116] During these cycles, the first and second displacement measuring units 450 and 550 are applied for measuring the amount by which the mandibular model 800 can be pulled upwards with respect to the zero position, while the magnitude of the arising forces is measured at various test locations P by means of the four force measuring units 700.

[0117] Based on the displacement values measured by the first and second displacement measuring units 450, 550, we can determine the creep of the mandibular model 800 and the subperiosteal implant 810 provided with a superstructure.

[0118] We can also determine the extent to which the forces measured by the force measuring units 700 have changed; this may provide clues to potential damage suffered by the subperiosteal implant 810 provided with a superstructure.

[0119] Also, in the case of a fracture, the maximum static and / or dynamic load required for fracturing the test piece can also be determined.

[0120] In contrast to the prior art technical solutions, the test bench according to the invention has the advantage that it can be operated manually and automatically thanks to its simple configuration.

[0121] Another advantage of the test bench according to the invention is that by applying two (a first and a second) pneumatic cylinders, it is possible to apply symmetrical and / or asymmetrical loads to the mandibular model. Thus, it is possible to simulate the effects and the magnitude of the forces exerted by the left and right masseter muscles. It is also possible to implement a time shift between the operation of the two masseter muscles, for example for reproducing a unilateral bite.

[0122] An advantageous feature of the test bench according to the invention is that the mandibular model is attached to the machine frame by means of the first and second articulated mechanisms, and the first and second resilient members, thereby allowing the mandibular model to move freely under the effect of the forces applied thereto, and therefore the mandibular joints are essentially also modelled. In particular, reinforced flexible polyurethane straps can be applied as first and second resilient members, whereby the potential deformation of the mandibular model as a result of the applied forces is not restricted. It is thus possible to continuously apply a tensile force with a predetermined direction to the mandibular model by the first and second pneumatic cylinders, even in case the model undergoes deformation. In contrast to the technical solutions known from the prior art, the test bench according to the invention has the further advantage that it is able to perform more accurate measurements as to the magnitude of the applied tensile forces, while at the same time the location of application of the forces can also be assigned to the measured force values.

Claims

CLAIMS1. A test bench (100) for mechanical testing of a subperiosteal implant (810), wherein the subperiosteal implant (810) is provided with at least one superstructure, the test bench (100) comprising:- a machine frame (200),- a mandibular model (800) to which a subperiosteal implant (810) is fixable,- at least one force measuring unit (700) that is connected at one end to a load- bearing plate (710) fixed to the machine frame (200) and can be releasably connected at its other end to at least one test location (P) of the subperiosteal implant (810) for force measurement, characterised in that the test bench (100) further comprises- a first shaft (613) that is rotatably connected to the machine frame (200) via at least a first bearing (612) such that it defines a first rotational axis (614),- a second shaft (623) that is rotatably connected to the machine frame (200) via at least a second bearing (622) such that it defines a second rotational axis (624), wherein the mandibular model (800) is attached to the first shaft (613) and to the second shaft (623) at two, first and second, mandible head portions (801 , 802) thereof for rotation about the first rotational axis (614) and the second rotational axis (624),- at least one control and command unit (300) that is mounted on the machine frame (200) and has at least two, first and second, pneumatic cylinders (400, 500) provided with a first and a second piston rod (410, 510), wherein the at least two, first and second, pneumatic cylinders (400, 500) are arranged above the mandibular model (800), and wherein the control and command unit (300) is in operative connection with the first and second pneumatic cylinders (400, 500) such that it is able to exert a force of a given magnitude on the first and second piston rods (410, 510) to move them in a vertical direction,- at least two, first and second, displacement measuring units (460, 560) mounted on the first and second pneumatic cylinders (400, 500) such that they are able to measure the vertical-direction displacement of the first and second piston rods (410, 510) of the first and second pneumatic cylinders (400, 500);- at least two, first and second, resilient members (450, 550) with a strap-like configuration that are connected to the respective lower ends of each of the first and second piston rods (410, 510) by means of a first and a second connection member (430, 530) such that the first and second resilient members (450, 550) support the mandibular model (800) by forming a loop around both sides thereof; wherein the at least one, first and second resilient members (450, 550) are operatively connected to the control and command unit (300) by way of being connected to the first and second piston rods (410, 510), and thus they are able to apply a tensile load to the mandibular model (800).

2. The test bench (100) according to claim 1 , characterised in that the control and command unit (300) is in operative connection with the first and second pneumatic cylinders (400, 500) such that it is able to exert forces of different magnitude on the first and the second piston rod (410, 510) to move them in a vertical direction by different amounts.

3. The test bench (100) according to claim 1 , characterised in that the first and second resilient members (450, 550) are implemented as reinforced flexible polyurethane straps.

4. The test bench (100) according to any of the preceding claims, characterised by comprising a plurality of force measuring units (700) that can be operated independently of each other such that the force measuring units (700) define mutually independent test locations (P).

5. The test bench (100) according to any of the preceding claims, characterised in that the mandibular model (800) comprises a respective pair of protruding limiting elements formed at each of the first and the second contact portions (451 , 551 ) such that they surround from both sides the first and the second resilient members (450, 550).

6. The test bench (100) according to any of the preceding claims, characterised in that the mandibular model (800) is made of plastic, resin, and / or of any other shape-retaining, deformable material.

7. The test bench (100) according to any of the preceding claims, characterised in that the mandibular model (800) is a customised mandibular model that corresponds to the anatomical characteristics of a particular individual.

8. The test bench (100) according to any of the preceding claims, characterised in that the magnitude of the force exerted by the pneumatic cylinders (400, 500) is about 0-900 N, particularly about 200-850 N.

9. The test bench (100) according to any of the preceding claims, characterised in that the control and command unit (300) is a pneumatically operated control and command unit (300).

10. The test bench (100) according to claim 9, characterised in that the pneumatic control and command unit (300) comprises at least one manual operation unit and at least one automated operation unit for providing selectable manual or automated operation of the at least two, first and second, pneumatic cylinders (400, 500).

11. A method for mechanical testing of a subperiosteal implant (810) provided with at least one superstructure utilising the test bench (100) according to any of the preceding claims, the method comprising the steps of providing a mandibular model (800) and securing on it the subperiosteal implant (810) provided with at least one superstructure, followed by securing the mandibular model (800) assembled this way to the machine frame (200) on the one hand with a first (610) and a second articulated mechanism (620), and on the other hand with a first (450) and a second resilient member (550) (S10); applying a force of a given magnitude to a first and a second pneumatic cylinder (400, 500) with a control and command unit (300), as a result of which the first and second piston rods (410, 510) of said cylinders move upward (S20); pulling upward, by means of moving upward the first and second piston rods (410, 510) according to step S20, at least two, first and second, resilient members (450, 550), and thereby the mandibular model (800) (S30); rotating, by means of pulling upward the at least two, first and second, resilient members (450, 550) according to step S30, the mandibular model (800) about a first rotational axis (614) and about a second rotational axis (624) in a first direction of rotation (615) (S40);measuring, with at least two, first and second, displacement measuring units (460, 560), the upward displacement of the first and second piston rods (410, 510) (S50); pushing, by means of pulling upward the at least two, first and second, resilient members (450, 550) according to step S30, the subperiosteal implant (810) provided with at least one superstructure secured onto the mandibular model (800) against the at least one force measuring unit (700) at at least one test location (P), thereby transferring the applied force from the first and second pneumatic cylinders (400, 500) to the at least one test location (P), wherein the test location (P) coincides with the position of the at least one superstructure (S60); measuring, with the at least one force measuring unit (700), the magnitude of the force applied at the at least one test location (P) (S70).

12. The method according to claim 11 , wherein the magnitude of the deformation of the mandibular model (800) is determined based on the upward displacement of the first and second piston rods (410, 510) measured by the at least two, first and second, displacement measuring units (460, 560) according to step S50.

13. The method according to any of claims 11 -12, wherein steps S20-S70 are performed essentially simultaneously.

14. The method according to any one of claims 11 -13, wherein, after performing step S70: the application of a force of a given magnitude to a first and a second pneumatic cylinder (400, 500) is terminated by the control and command unit (300), as a result of which the first and second piston rods (410, 510) move downward (S80); the at least two, first and second, resilient members (450, 550), and thereby the mandibular model (800), are lowered by means of moving downward the first and second piston rods (410, 510) according to step S80 (S90);- by means of lowering the at least two, first and second, resilient members (450, 550) according to step S90, the mandibular model (800) is rotated about a first rotational axis (614) and about a second rotational axis (624) in a direction opposite the first direction of rotation (615) (S100); the downward displacement of the first and second piston rods (410, 510) is measured with at least two, first and second, displacement measuring units (460, 560) (S110);by lowering the at least two, first and second, resilient members (450, 550) according to step S90, the subperiosteal implant (810) provided with at least one superstructure secured onto the mandibular model (800) is freed up, such that to form a spaced apart distance from the at least one force measuring unit (700) (S120).

15. The method according to claim 14, wherein steps S80-S120 are performed essentially simultaneously.

16. The method according to any of claims 14-15, wherein steps S20-S70 and steps S80-S120 are performed multiple times.

17. The method according to any of claims 11 -16 performed with a test bench (100) according to any of claims 2-10, comprising: applying forces of different magnitude to the first and the second pneumatic cylinders (400, 500) with the control and command unit (300), as a result of which the piston rods (410, 510) of said cylinders are displaced upward (S20b) by different amounts; and performing steps S30-S70 with regard to step S20b.

18. The method according to claim 17, wherein steps S20b-S70 are performed essentially simultaneously.

19. The method according to any one of claims 17-18, wherein, after performing steps S20b-S70: steps S80-S120 are carried out.

20. The method according to claims 19, wherein steps S80-S120 are performed essentially simultaneously.

21. The method according to claims 17-20, wherein steps S20b-S70 and steps S80-S120 are performed multiple times.

22. The method according to any of claims 11 -21 , wherein a force between approximately 0 and 900 N, particularly between approximately 200 N and 850 N is applied to the subperiosteal implant (810) provided with at least one superstructure.

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